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/NBS building science series TA435 .U58 V58;1974 C.1 NBS-PUB-C 1974 NBS BUILDING SCIENCE SERIES

U.S. DEPARTMENT OF COMMERCE / National Bureau of Standards

State-of-the-Art

3f Structural Test Methods

for Walls, Floors, Roofs

and Complete Buildings
The Building Science Series

The Building Science Series disseminates technical information developed at the National Bureau of Standards on

building materials, components, systems, and whole structures. The Series presents research results, test methods, and performance criteria related to the structural and environmental functions and the durability and safety characteristics of building elements and systems. These publications, similar in style and content to the NBS Building Materials and Structures Reports (1938-59),

are directed toward the manufacturing, design, construction, and research segments of the building industry, standards organizations, and officials responsible for building codes. The material for this Series originates principally in the Center for Building Technology of the NBS Institute

for Applied Technology. The publications are divided into three general groups: Building Systems and Processes;

Health, Safety and Comfort; and Structures and Materials. For further information regarding these publications

please contact the Scientific and Professional Liaison Section, Center for Building Technology, Institute for Applied Technology, National Bureau of Standards, Washington, D.C. 20234.

ISee mailing list announcement on last page |
National gweau &f S^uar^

NOV S 8 ig7S

tm$> State-of-the-Art

• u5A of Structural Test Methods for Walls,

Floors, Roofs and Complete Buildings

C. W. C. Yancey and L. E. Cattaneo

Center for Building Technology

Institute for Applied Technology

National Bureau of Standards

Washington, D.C. 20234

H05 BinJdin* <$uenae- Series iM> . 5%

Prepared for

OflBce of Policy Development and Research Department of Housing and Urban Development

Washington, D.C. 20410

U.S. DEPARTMENT OF COMMERCE, Frederick B. Dent, Secretary

NATIONAL BUREAU OF STANDARDS, Richard W. Roberts, Director

Issued November 1974
Library of Congress Cataloging in Publication Data

Yancey, C. W. C.

State- of- the- Art of Structural Test Methods

Walls, Floors, Roofs, and Complete Buildings.

(National Bureau of Standards Building Science Series 58) Supt. of Docs. No.: 03.29/2:58

1. Buildings—Testing. 2. Structural Frames—Testing.

I. Cattaneo, L. E., joint author. II. United States. Dept. of Housing and Urban Development. Office of Policy Development

and Research. III. Title. IV. Series: United States. National Bureau of Standards. Building Science Series 58. TA435.U58 No. 58 [TH845] 624M71 74-23735

National Bureau of Standards Building Science Series 58

Nat. Bur. Stand. (U.S.), Bldg. Sci. Ser. 58, 139 pages (Nov. 1974) CODEN: BSSNBV

U.S. GOVERNMENT PRINTING OFFICE

WASHINGTON: 1974

For sale by the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402 (Order by SD Catalog No. C13.29/2:58). Price $2.00
State-of-the-Art of Structural Test Methods

for Walls, Floors, Roofs and Complete Buildings

by

C. W. C. Yancey and L. E. Cattaneo

Structures Section

Structures, Materials, and Life Safety Division

Center for Building Technology, I AT

National Bureau of Standards

ABSTRACT

As part of a comprehensive research program concerned with the structural

testing of building components, conducted for the U. S. Department of Housing

and Urban Development (HUD) , a search for information was conducted. This

search was undertaken in order to document existing information pertaining

to structural testing of wall, floor and roof assemblies. Various information

sources were consulted to trace the evolution of structural testing of

building construction from the 1930 's to the present time. This task was

a prerequisite to defining the state-of-the-art and to identifying the test

areas requiring fundamental research.

Based on information obtained from a review of the literature and from

liaison with committees concerned with the development and revision of voluntary standards, it was found that there is a dearth of research information

contributing directly to the development of test methods. Most of the

research conducted on building components has been carried out either to

observe the behavior of a sample of a particular type of construction or to

evaluate the performance of a specimen against some performance requirements. However, helpful inferences can be made on the basis of some of the

documentation, especially that contained in reports of full-scale tests on housing

.

As a result of comparing the test methods used by the National Bureau

of Standards in HUD project Operation BREAKTHROUGH with American Society for

Testing and Materials (ASTM) Standard methods, several recommendations

have been made by the authors for improving present structural test practice.

An up-to-date status report of voluntary test standards activities

(in the U.S.) was prepared through verbal and written communication with

members of the technical subcommittees of ASTM Committee E-6 on Performance

of Building Construction.

Key Words: Building construction; complete buildings; floors; roofs; standardization; test methods; walls.

1.0 INTRODUCTION

A study of available information was undertaken for the purposes

of documenting information applicable to structural test method development

and determining what fundamental research is needed for the improvement

of present test practice. To obtain the background of the present state

Of practice, the evolution of structural testing of building construction

has been followed from its early stages to the present time. The information

sources consulted are: indexes of governmental agency publications; Engineering Index; NTIS Search; libraries; lists of proceedings of symposia, colloquia

and conferences; indexes of publications by standards associations; technical

indexes; regulatory documents and codes of practice; individual researchers

and committees concerned with the promulgation of voluntary test standards.

1
Chapter 2 presents a review of existing information as found in publications; a Bibliography containing all of the references cited is presented

in Appendix A of the report. Included in the review are both publications

of a general nature and material of specific reference to walls, floors,

roofs or complete buildings. The principal findings of this part of the

study are summarized at the end of the chapter.

The present status of standards for structural performance testing

is discussed in Chapter 3. The most commonly-used standard methods are tabulated. The current activities of both domestic and international

association are discussed, and a summary of standards under revision,

as well as new standards in various stages of preparation, is presented.

A critique of some adopted test methods based on the experience of

the National Bureau of Standards (NBS) with the structural testing of

industrialized building components is presented in Chapter 4. There are

7 separately published test reports that provide material for Chapter

4. Five reports pertain to the testing of panels representative of proposed

building systems in the Department of Housing and Urban Development

Operation BREAKTHROUGH. The remaining two reports are of experimental

studies of full-scale houses, one under field conditions and one under

laboratory conditions. The test methods used in the NBS test program

are discussed and compared with corresponding ASTM E72 standard methods.

Several recommendations are made for improving the standard methods.

A review of requirements stated in codes , standards and performance

criteria documents with respect to structural testing is summarized in

Chapter 5. Typical clauses have been excerpted or paraphrased from a representative sample of foreign and domestic documents.

2.0 LITERATURE REVIEW

In order to document existing information pertinent to structural

testing of building components, a review of the literature was undertaken.

Thirty publications, spanning from 1937 to 1973, have been studied and

are discussed in this chapter. To establish a framework for the review

of reports of technical studies, several items of information were identified

as being of uppermost importance. These items were: objective of the

investigation, scope, main parameters considered, type of materials and

construction and the main conclusions and recommendations presented.

It is intended that the summaries that follow supply this key information

as well as convey the historical and technical significance of the work that

is described. The summaries are sequenced in chronological order to aid in

fulfilling the historical objective.

The summaries are arranged into five sections. The classification

of the principal structural elements being investigated (i.e. walls, floors,

roofs and complete buildings) provides the headings of four sections. The

fifth section covers publications of a general nature which do not strictly

fit any of the other four headings. The review of general publications is

presented first. Table 2.1.1 illustrates the distribution of the subjects

covered in the review by charting the types of construction in relation to

specific test categories. The coded entries (G, general information; W,

walls; F, floors; R, roofs; S, complete structures) refer to the accompanying

lists (table 2.1.2) of publication titles which are arranged in the same order as the reviews appear in the report.

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Table 2.1.2 - Publications referenced in table 2.1.1 on structural

testing grouped by types of construction.

GENERAL INFORMATION

G-l "Structural Properties of Low-Cost House Construction [43]*

by National Bureau of Standards

G-2 "Research on Building Materials and Structures for Use In LowCost Housing" [20]

by H. L. Dryden

G-3 "Methods of Determining the Structural Properties of Low-Cost

Housing Constructions" [49]

by H. L. Whittemore , and A. H. Stang

G-4 "A Philosophy of Loading Tests" [19]

by D. B. Dorey and W. R. Schriever

G-5 "The Testing of Structures" [3 8]

Report of a Committee set up by the United Kingdom

Institution of Structural Engineers

STRUCTURAL EVALUATION OF WALLS

W-l "Transverse Strength of Masonry Walls" [30]

by C. B. Monk, Jr.

W-2 "The Racking Resistance of Frame Wall Construction [24]

by M. W. Isenberg, R. M. Branoff and R. R. Mozingo

W-3 "Guides to Improved Framed Walls for Houses" [4]

by L. 0. Anderson

W-4 "Shear in Grouted Brick Masonry Wall Elements" [7]

by J. A. Blume and J. Proulx

W-5 "Structural Behavior of Masonry Infilled Frames Subjected to

Racking Loads" [13]

by C . Carter and B . S . Smith

W-6 "Experimental Determination of Eccentricity of Floor Loads Applied

to a Bearing Wall" [47]

by D. Watstein and P. V. Johnson

W-7 "Racking Resistance of Timber Framed Walls" [35]

by T. Ramstad, V. D. Reyers and E. B. Espiloy, Jr.

W-8 "Racking Strengths and Stiffnesses of Exterior and Interior Frame

Wall Construction" [34]

by NAHB Research Foundation, Inc.

4
Table 2.1.2 continued - Publications referenced in table 2.1.1 on structural

testing grouped by types of construction.

STRUCTURAL EVALUATION OF FLOORS

F-l "Testing of Large Diaphragms" [14

J

by R. D. Cousineau

F-2 "1966-Horizontal Plywood Diaphragm Tests" [45]

by John R. Tissell

F-3 "Deflections of Light-Gage Steel Floor System Under Action of

Horizontal Loads" [32

J

by A. H, Nilson

STRUCTURAL EVALUATION OF ROOFS

R-l "Lateral Tests on Full-Scale Lumber and Plywood Sheathed Roof

Diaphragms" [42]

by J. R. Stillinger

R-2 "Loading Tests on Full-Scale House Roofs" [44]

by H. J. Thorburn and W. R. Schriever

R-3 "Strength and Behavior of Light-Gage Steel Shear Diaphragms" [27]

by L. D. Luttrell

STRUCTURAL EVALUATION OF COMPLETE HOUSES

S-l "Strength of Houses" [48]

by H. W. Whittemore, J. B. Cotter, A. H. Stang and

V. Phelan

S-2 "Evaluation of 40-ft by 100-ft Frameless Straight-Sided Prefabricated Metal Utility Building" [29]

by the U.S. Naval Civil Engineering Research and Evaluation

Laboratory

S-3 "Rigidity and Strength of Houses Built of Plywood Stressed Cover

Panels" [28]

by R. F. Luxford and E. C. 0. Erickson

S-4 "Structural Tests of a House Under Simulated Wind and Snow Loads"

[18]

by D. B. Dorey and W. R. Schriever

S-5 "Full-Scale Tests of Pre-Cast Multi-Story Flat Construction" [21]

by A. J. Francis, W. P. Brown and S. Aroni

S-6 "The Wood-Frame House as a Structural Unit" [50]

by National Forest Products Association

S-7 "Effect of Wind Pressure on the Racking Strength and Stability of a One-Story, Gable-Roof Building of Sandwich Panel

Construction" [17]

by Simon H. Diskin, Consulting Engineer

5
Table 2.1.2 continued - Publications referenced in table 2.1.1 on structural

testing grouped by types of construction.

S-8 "Model and Full-Scale Tests on a Five-Story Cross-Wall Structural

Under Lateral Loading" [40]

by B . P. Sinha, H. P. Maurenbrecher and A. W. Hendry

S-9 "Test and Evaluation of the Prefabricated Lewis Building and Its

Components-Phase 1, Part 2-Full Scale Building

Tests" [36]

by T, W. Reichard and E. V. Leyendecker

S-10 "Tests and Evaluation of the Prefabricated Lewis Building and Its

Components -Phase II" [26]

by E. V. Leyendecker and T. W. Reichard

S-ll "A Facility to Evaluate Three-Dimensional Performance of Modules of

Houses" [8]

by K. H. Boiler

6
2.1 General Information

"Structural Properties of Low-Cost House Construction" [43]*

by National Bureau of Standards

This Letter Circular, LC-502-A, is a leaflet produced for public

distribution by the National Bureau of Standards in 1937 that contains

descriptions of test methods. This was possibly the first reference to

test methods forming the basis of ASTM Test Method E72 (originally issued

in 1947) . The Letter Circular is the forerunner of National Bureau of

Standard-Building Materials and Structures Report BMS 2 [49] which is more

widely known. Circular LC-502-A is supplementary to LC-502 which discussed

generally, the then current federal research program related to a study of

building materials and structures for use in low-cost housing.

The Circular describes test procedures to be used in determining

the structural properties of walls, partitions, floors and roofs. The

description includes requirements for size and number of specimens. The

types of test loads described include compressive, transverse, impact,

racking and concentrated loads for various structural elements, and, lastly,

vertical shearing load at a butt joint between prefabricated floor panels.

Requirements are also given for maximum load capacities of specimens

and for allowable permanent deformations after application of specified

loads. However, these requirements were offered, not for use in building

codes, but only as a guide in the selection of constructions for further

study. If the performance of a construction did not comply with certain

minimum requirements, no further tests were made.

Although the Circular considers numerous categories of structural

test methods, it is very brief in its descriptions of these methods. It was intended to be a preliminary documentation of procedures that were

being planned for use, therefore, it lacks some of the details to be found

in BMS 2 [49] which superseded it; hence it is primarily of historical

interest.

"Research on Building Materials and Structures for Use In

Low- Cost Housing" [20J

by H. L. Dryden

This was the first (BMSl) of a series of publications —the National Bureau

of Standards Building Materials and Structures (BMS) Reports —originated

in 1938 to deal with the technical aspects, procedures and results of

tests associated with a federally-funded research project. In this first

report, however, the content is devoted to a general explanation of the

intent of the research program that was being formulated with the advice

of various government housing agencies by a committee of NBS division

chiefs under the chairmanship of the author. The program was funded by

Congress for the purpose of assisting progress in the building industry

to attain the goal of satisfactory housing within the means of those in

need of it.

The stated objective of the investigation was "to furnish government

agencies, the building industry and the public, technical information

from every available source on the engineering properties of building

The bracketed number corresponds to the publication's listing in the

Bibliography in Appendix A.

7
materials as incorporated in the structural elements and equipment of

a house, with particular reference to low-cost housing, and including

new materials, equipment and methods of construction as well as those

already in use."

In discussing the procedure and scope of the program the author points

out that, for simplicity, structural testing was to be limited to laboratory

investigation of structural elements. These elements were to be suitable

for detached houses, new houses and low-cost apartments. New as well

as conventional constructions were to be included in the study, but their

selection was narrowed by a cost limitation to restrict the investigation

to constructions (and equipment) suitable for a low-cost house. The report

closes on the note that in the BMS reports which are to follow, NBS is to serve as a fact-finding agency and that reports are not to be construed as "approvals .

In retrospect, 152 BMS Reports were published. Of the 45 that involved

structural testing, almost all presented performance data on particular

types of construction. The testing methods used in obtaining the data

contained in these reports are referenced to BMS 2 [49] , which is devoted

to the descriptions of such procedures.

"Methods of Determining the Structural Properties of Low-Cost

Housing Constructions" [4 9]

by H. L. Whittemore, and A. H. Stang

This is the first formal publication (BMS2) that describes methods in use

(in 1938) in the NBS laboratories for measuring the strength, stiffness

and resistance to local damage of types of construction intended for walls,

partitions, floors and roofs of low-cost housing construction. The tests

which are described were designed to provide information on structural

properties of wall specimens under compressive, transverse, concentrated,

impact and racking loads; of partition specimens under impact and concentrated

loads; of floor specimens under transverse, concentrated and impact loads;

and of roof specimens under transverse and concentrated loads. A graphic

method of presenting the results is also described and includes the description of a loading procedure for determining permanent deformation (set)

at progressively higher load levels.

Unlike its predecessor, NBS Letter Circular LC-50 2A, this report does

not suggest acceptable levels of performance, but is restricted to the

various procedures for testing, all of which formed the basis for ASTM

Method E72 (originally issued in 1947) . It promotes the structural testing

of elements such as floors, walls and roofs rather than complete houses,

for the sake of efficiency and economy. The authors cite house testing

as being too expensive, time consuming and limited by the response of

the weakest element in providing information on performance of the whole

structure. Recommendations are made for the size and number of specimens

and the method of loading. Instrumentation suitable for the measurement

of deformation and displacement is described and consideration is given

to using modified procedures for specimens of different types of construction.

It is interesting to note that the Foreword of the report contains

one of the earliest references to the probability of performance requirements

and performance tests finding their way into building codes to replace

prescriptive clauses for conventional construction.

8
"A Philosophy on Loading Tests" [19]

by D. B. Dorey and W. R. Schriever

This paper, presented at the 58th Annual Assembly of the American

Society for Testing and Materials, in June 1955, addresses the need for a systematic approach to formulating structural performance test specifications.

Two critical shortcomings in the building codes of 1955 were found to be in

the areas of test load determination and test result determination. As a requisite to the derivation of a philosophy on structural testing, several

important factors to be considered in such a formulation were discussed on the basis of the then current state of knowledge. The distinguishing characteristics of three structural test categories were given in the following

order: 1) an "acceptance test", 2) a "rating test", and 3) a "research test".

The authors concluded the paper with two significant proposals based on their

assessment of the existing state of knowledge. First, they derived a proposed method for determining the magnitude of the test load. Secondly, they

suggested some guidelines for developing a criteria to be used in assessing

structural adequacy on the basis of the test results.

From a review of the specifications for structural performance tests

included in building codes from various parts of the world, the authors con- cluded that the "specifications differ in principle, detail and procedure".

The results of the code review were summarized in a table which listed the

requirements for the following factors: type of test, time of test, superimposed test load, duration of loading, requirements after loading and

requirements on removal of loading. Five of the thirteen specifications so summarized pertained to concrete exclusively, and five others pertained

generally to all construction materials. The lack of a standard set of

descriptions for expressing the type of test was indicated by the use of a common label such as "strength", by a number of codes to express significantly

different structural requirements. For example, one code stated a qualitative

"no signs of failure" in a specification for concrete strength testing while

another one cites the requirement for concrete strength quantitatively, in

terms of limiting deflections. It is of interest to note that a similar sur- vey was conducted in 196 4 by a committee charged by the United Kingdom

Institution of Structural Engineers. A tabular summary of this survey can

be found in reference [38] . A summary of a 1973 survey conducted for this

report is presented in Chapter 5.

In reviewing the discussions of the three structural test categories

named by the authors, it is observed that the categories are delineated

on the basis of circumstances in practice that dictate the test. For example,

an acceptance test is one performed on a completed structure or part thereof

to determine the structure's acceptability to some designated set of

requirements. On the other hand, a rating test is one performed on a number

of specimens to determine the acceptability of a commercially produced type

of construction. A research test is one performed to investigate the structural behavior of a type of construction. In contrast to the rating and

research tests, the acceptance test serves to establish that a minimum allowable level of strength or stiffness is achieved by the structure in question.

Both the rating test and the research test may have as one of their objectives

the determination of a load factor by safety applicable to the type of con- struction in question. In which case they possess the common characteristics

of requiring the load to increase until failure has occurred. It should

be emphasized that the standardization of test categories is a very important

prerequisite to the development of structural test specifications.

The lack of a common understanding of the relationship between the test

requirements and the structural performance of actual structures renders the

testing profession to relatively the same position it was in nineteen years

ago. The current use of such terms as "proof-load testing", "acceptance

testing", "prototype testing" "quality-control testing" and "ultimate strength

9
testing" to indicate in many instances the same set of test circumstances is

symptomatic of the problem.

Before presenting their suggested approach to determining test loads

and to interpreting test results the authors briefly discussed eleven factors

to be considered in test formulation. These factors are listed below and

each item is followed by a comment whose purpose is to inform the reader

of the nature of the discussion.

A. Classification of Structures

The structures referred to in the paper were classified as static

ally determinate or statically indeterminate.

B. Intended Use of Structure

"The risk of failure, that is, the losses in human lives and

valuable property which would result from failure depends upon

the use and occupancy of the structure."

C. Materials of Construction

The physical and chemical properties of a given material determine the use for which that material is most suited.

D. Standard of Workmanship

The variability of workmanship is critical to the structural

performance of some types of construction (e.g. concrete).

E. Design Loads and Actual Loads

Consideration should be given to the probability of overloading

with respect to the recommended design loadings.

F. Overdesign for Special Reasons

The excessive loads anticipated to occur during construction

may warrant the overdesigning of a structure

.

G. Types of Failure

Failures are classified into three types: 1) those without

warning, 2j those occurring after yielding has taken place at a certain load, and 3) those that are marked by a state of unserviceability at a certain safe load.

H. Factor of Safety

The distinction is made between "stress factor of safety" and

"load factor of safety"

I. Risk of Failure

This factor is concerned with potential danger to human life and

valuable property during the structure's service life.

J. Duration of Loading

The discussion centers on the effects of long-term loading on the deformations of certain types of construction, (e.g. wood)

10
K. Repeated Loading and Vibration

The discussion touches on only the subject of fatigue strength

considerations for some design considerations.

From the above listing it is observed that all of these factors are of concern to the structural designer and the structural evaluator.

In the proposed method of test load determination, the authors explained

that the magnitude of test loading in an acceptance test may be made up of

three parts which are directly additive. The first part consists of the

total design live load plus any necessary dead load additions. The second

part is expressed as a certain percentage of the design live load, based on

the intended use or occupancy and on the type of failure (see the three

classes of failure mentioned above) . The applicable percentage could be

determined from any one of three curves depending on the type of failure

usually experienced by the type of structure in question. The third portion

is expressed as a percentage of design live load and it is determined by

summing percentages of design live load attributed to such factors as workmanship, deterioration and fatigue. Although a tabular format was suggested

for presenting the percentages based on the latter factors, no attempt was made by the authors to establish such values. For the rating test the

magnitude of test loading may also be composed of three parts. However, the

third part would contain an additional percentage based on the variability of

test results for various materials and on the relative sample size.

The proposed criteria for evaluating structural performance on the basis

of test results are fundamentally sound, but remains too general to offer

sufficient guidance in actual test applications. A good point for test

specification writers to keep in mind is the recommendation that a combination

of criteria be used in specifying strength requirements in an acceptance

test. That is, a combination of maximum deflection and minimum deformation

recovery, coupled with the absence of any signs of distress in the primary

structural components should be used in strength requirements.

This paper expounded on some important fundamental subjects related to

structural performance testing and this in itself was a rarity. It took an active, rather than passive, position in that certain recommendations were made to implement the then current state of knowledge. The future development

of new and improved standard test methods is dependent on additional energies

being expended to establish a standard set of terms to express certain concepts and to systematically establish the magnitude of test loading for

different test conditions.

"The Testing of Structures" [38]

Report of a Committee set up by the United Kingdom Institution

of Structural Engineers

In 1962, an ad hoc committee was charged by the United Kingdom Institution

of Structural Engineers with the mission of examining various code requirements for structural behavior as they relate to acceptance testing and

of developing some recommendations for a rational basis for structural

tests in general. This report, published in 1964, presents the Committee's

findings and advances some guidelines for the practitioner who must devise

and execute tests to satisfy code requirements.

The guidelines are aimed mainly at the testing of new structures;

however, testing of bridges, liquid-containing structures, foundations,

piles and materials are specifically excluded from the scope. The Committee

notes that some modifications of the test guidelines may be necessary

to deal with proof testing of old structures. Although no provisions

11
are stated for implementing dynamic testing, the authors acknowledge the

limitations of static loading tests and alert the engineer to consider

other design forces such as fatique loading.

Initially, the report defines two general types of tests- an acceptance

test and a test to destruction to determine ultimate strength- and summarizes

the circumstances which usually make testing necessary. The section on Testing Procedure points out some factors to consider in applying and

recording the load and in measuring the resulting deformation and stress.

For example, when considering a procedure for load application, it is

recommended that the test load be applied in stages or increments. Often

it is desirable to follow the same procedure for load removal (i.e. by

load decrements). Specifically, the authors recommend "that the number

of load increments (or decrements) should be about ten and not less than

five . "

Another section of the report discusses test requirements with respect

to load factors, duration of loading, acceptable deformations and acceptable

defects. On the subject of duration of loading, the main conclusion is

that "the test load on a structure need not be maintained longer than

required to ensure that its effects are fully realized." The time required

for a test specimen to adjust to applied loading is mainly influenced

by the type of materials involved; to emphasize the point the Committee

compares the time needed by metal structures (a few minutes) for settling

down to that necessary for adjustment by timber structures (several hours)

.

One of the several milestones in this report is the set of recommendations

for minimum times to be allowed for load application or load removal,

prior to making measurements and observations. These quantitative recommendations are stated for several stages of test, with a distinction being

made between "elastic" and "non-elastic" materials. In order to establish

a set of limits for acceptable deformation and recovery, a survey of current

practice was executed. Several codes were reviewed in relation to their

requirements for deflection limits and the limits are summarized in a table. Then some recommendations are made for deformation limits to be

observed during testing as well as for acceptable rates of recovery. A

table summarizing the code requirements for acceptance tests, similar

to the one prepared by the Committee, can be found at the end of Chapter 5

( see table 5.5).

2.2 Structural Evaluation of Walls

"Transverse Strength of Masonry Walls" [30]

by C. B. Monk, Jr.

In the general absence of design code provisions for the transverse

strength of unreinforced masonry walls, the author set out to provide

some basis upon which design requirements could be established. The investigation was primarily aimed at evaluating the transverse strength of 6-in

brick walls. Starting about 1951, this study was comprised of three distinct

stages: 1) transverse tests were performed in the laboratory on nine

-ft x 8-ft brick wall specimens, 2) the exterior walls of an 18-ft by

22-ft by 8-ft high model house were tested to check the laboratory forecast

of strength and 3) another set of 4-ft by 8-ft brick walls were tested in

the laboratory under different end conditions from those in stage 1. In

order to provide a basis of comparison for the 6-in brick walls with conventional wall construction (for that period) tests paralleling stages 2 and

3 were performed for 8-in brick block wall and 10-in brick cavity wall

specimens

.

12
In the first stage of testing, the type of mortar was a variable

while the same type of brick was used for all nine specimens. Three wall

specimens each were prepared from three types of mortar. Following the

recommendations for transverse loading presented in "Building Materials

and Structures Report, BMS No. 2 [49] , quarter-point loading was applied

to the walls, placed in a vertical position. The support condition at

the ends of the 7-ft 6-in-span and the support at the base of the wall

conformed to the recommendations of BMS No. 2. The specimens were loaded

to failure and the average maximum load and modulus of rupture were tabulated

for each type of mortar. The recommendations for determining the allowable

load for masonry walls given in Building Materials and Structures Report,

BMS No . 109 [48] were consulted to derive allowable loads for the nine

specimens for an 8-ft span.

To check the laboratory prediction of transverse strength of 6-in

brick walls, a model single-story, brick house was tested. The mortar

used in constructing the model house was identical to one of those

used in the first stage of testing. Since uniform pressure was held

to be more representative of the lateral forces to which walls are subjected

in service, an air bag system was used for applying the load sequentially

to each exterior wall. Hence, the method of loading and the boundary

conditions of the walls were differed in stage 2 from the corresponding

parameters in stage 1. The air pressure was measured by using the average

of three manometers and the desired lateral pressure was obtained by

adjusting the head of water above the bottom of two standpipes. According

to the author, the pressure was maintained reasonably constant during

the time required for reading deflections. To provide a check on the

manometer readings, the connections of the reaction framework were instrumented

with electrical strain gages. The framework was so designed that the

strain readings could be used to determine the total reaction force.

A grid system was employed on the inside of each wall to locate the dial

gages used for measuring the lateral deflections.

Typically, load-deflection curves starting with an initial zero load

and terminating at the failure load were drawn for each data point. It was noted that the curves generally were characterized by an initial straight

portion, indicative of a linear relationship between load and deflection.

A method for determining the "yield strength load" was developed. This

"yield strength load" corresponded to the ordinate of the point of intersection of a line parallel to and offset from the initial slope of the loaddeflection curve. The amount of offset was equivalent to the deflection

at the point of transition from linearity to non-linearity. This method

could be useful in comparing the performance of different types of masonry

walls, provided there is close correlation between the test parameters

for any two cases. It was noted that tests identical to the stage 2 testing

were performed on an 8-in brick-block, and a 10-in cavity, wall model for

the purpose of comparing performance.

It was because of a high percent difference between the results of

stages 1 and 2 that it was decided to test additional 6-in brick walls

in the laboratory, with the air bag system. The "yield strength loads"

obtained in stage 2 suggested considerably higher strengths than the average

maximum loads obtained for identical construction in stage 1. Three 4-

ft by 8-ft brick-wall specimens, 6 in thick, were subjected to uniform

pressure and at the same time the field boundary conditions were more

nearly simulated. Contrary to the base support treatment in stage 1,

these three walls were tested flat-ended without the benefit of base rollers.

An identical procedure was performed for three 8-in brick-block and three

10-in cavity wall specimens. The test results for stage 3 did indicate,

for the 6-in walls, a closer prediction of the field strength than was obtained from the results of stage 1. To justify the apparent higher

transverse strengths obtained by using the air bag system, as opposed

13
to the quarter-point loading the author performed some calculations based

on the so-called "Statistical Theory of Rupture." To quantify the influence

of method of loading on mean strength the author concluded that "theoretically, on the average, the uniform loading, depending on end conditions,

will yield mean strengths 8.8 to 17.1 percent greater than the quarterpoint loading for the case discussed* [masonry construction with a coefficient

of variation of 16.8]." It is interesting to note that although ASTM

Standard E72-68 [5] does include both methods of loading, there is no related commentary pertaining to the possible influence of the loading

method on the test results.

"The Racking Resistance of Frame Wall Construction" [24]

by M. W. Isenberg, R. M. Barnoff and R. R. Mozingo

The report done by Pennsylvania State University for FHA in 1963

contains the results of a limited study and its main contribution is a survey of existing information on the racking resistance of frame wall

construction. The survey was made to determine what research was required

to arrive at a procedure for the determination of racking strength. A

pilot testing program was conducted to evaluate existing test procedures

and examine the feasibility of performing racking tests by a diagonal

compression procedure.

One output of the survey, a bibliography of 72 references, provides

background on the racking test for wall panels and documents the need

for its improvement. The authors express the opinion that the literature

available to them was, in general, rather limited in depth since most

laboratories had confined their work to tests of panels rather than basic

research on the racking problem. In addition, the survey included documentatation of opinions on the racking test and associated problems given by

researchers in 36 laboratories and institutions. In discussing the merits

of the then existing techniques of racking testing and the needs of the

racking evaluation problem, the authors consider such topics as manner

of load application, participation of wall anchorage in resistance to

racking, the extent to which undesirable racking effects are developed,

and limitations on racking distortion imposed by various regulatory organizations. The existing ASTM E72 standard racking tests, including those

of specimens conditioned by wetting, are discussed and a proposal is made

for an alternative method of loading employing diagonal compression.

A laboratory comparison of the existing standard method and the proposed

method made use of panel specimens of one height (8 ft) and three different

widths (8 ft, 4 ft and 2 ft) . A total of 7 comparative tests were performed.

These comprised an 8-ftx 8-ft control specimen and 3 sets of duplicate

specimens of the above sizes. The control specimen used 2x4 wood stud

framing with horizontal 1-in x 8 -in board sheathing and a 1-in x 4 -in

diagonal let-in brace; the other specimens used similar framing with 5/16-

in plywood sheathing and no brace.

One group of tests was performed in accordance with ASTM Method E72.

The instrumentation for measuring displacements met the requirements of

the ASTM procedure and was augmented by additional instruments for measuring

other, unspecified deflections and loads for correlation with similar

observations made in the proposed method.

The diagonal load tests were performed with the plane of the specimens

in a horizontal position. The diagonal compression load was applied between

two opposite corners of the specimens by a hydraulic jack through tierods. Load was indicated by strain gages on the tension bars and deformation

The portion in brackets is not part of the quotation.

14
of the specimen was measured by a single dial gage mounted along the

diagonal joining the unloaded corners of the specimen.

The authors discuss the additional information needed for the development

of a satisfactory racking test and outline a plan for future research.

For this interim period of research, recommendations are made to extend

and standardize the existing requirements for adequate racking resistance

stated in FHA Circular 12 [41] and determined by ASTM Method E72. One

major departure from those existing requirements involves the recommendation

of an alternate test involving panels in a wetted condition.

The report is not only a useful guide to testing by racking but is

also helpful in that many of the problems discussed are common to other

test methods. The major contribution of the report is its state-of-theart survey of racking resistance and its documentation of the strong need

for improvement of existing racking test methods and criteria.

"Guides to Improved Framed Walls for Houses" [4]

by L. 0. Anderson

As indicated in its summary, the paper itself is a summary of work

reported by the Forest Products Laboratory (FPL), U.S. Department of

Agriculture during the period 1934 to 195 8. Comparisons are made of the

relative racking rigidity and strength of sheathed framed walls, with

and without openings, and ranging in size from 8 ft x 8 ft to 12 ft x

18 ft. Relative values are based on the performance of a control, conventional

frame wall without openings made up of nominal 2 x 4-in studs spaced at

16 in on center and sheathed with horizontal 1 x 8 -in lumber fastened

to each stud with two eight penny common nails.

Of particular interest to the present survey, however, is a photographic

illustration of an FPL racking apparatus. This fixed steel frame has

the capability of racking an 8-ft x 8-f t panel in opposite directions

in one setup. The reversible feature of the equipment was used in testing

panels constructed with diagonally placed board sheathing. Although no details are given about this equipment, its reverse loading feature makes

it desirable as a prototype reference in the event of any development

of a proposed standard cyclic racking test.

"Shear in Grouted Brick Masonry Wall Elements" [7]

by J. A. Blume and J. Proulx

At the request of the Western States Clay Products Association, John

A. Blume and Associates conducted a research testing program in 1964-

68 to study the shear capacity of grouted brick masonry wall panels. Tests

were made on 84 4-f t by 4-ft grouted masonry panels to explore the effects

of various parameters (including reinforcement, grout, core thickness,

orick strength and brick absorption rate) on shear strength and energy

capacity. Although some tests were also made to evaluate the damping

of 4-ft-square wall panels, made to vibrate freely in a transverse mode

by impact loads, the major effort deals with "shear" as measured by diagonal

tension —the usual control in seismic design and response of walls and

wall elements. The test procedure finally selected after preliminary

study was one of compression loading across two diagonally opposite corners

of a square panel to develop tension normal to the loaded diagonal. The

report is included here primarily for its consideration and discussion

of the diagonal tension test method used to evaluate racking shear capacity

of brittle wall panels.

15
The authors selected the diagonal loading technique as most appropriate

for obtaining the desired results (shear capacity) with masonry elements.

Their reasons for choosing this method over others, such as a pure shear

technique, ASTM-E72, or certain modifications of ASTM-E72, were that the

diagonal test was easier to perform and developed a state of stress in

the panel that was known with greater clarity. Equations are given for

average shear stress on a test wall panel section parallel to its base

and top edges, as well as for maximum diagonal tensile stress acting normal

to the load line at the center of the panel. Although all of the shear

tests involved only a diagonal compressive force, there are also presented

stress equations for cases of (a) a diagonal compressive force plus uniform

pressure normal to a parallel pair of panel edges and (b) an applied

shear plus triangularly-distributed counteracting pressure normal to a parallel pair of panel edges.

Aside from the particular values determined for the constructions

tested, this report presents what appears to be a favorable method for

obtaining shear strength, energy capacity and ductility related to racking

in brittle materials. However, appropriate though it might be for materials

which fail in diagonal tension, it would also appear necessary to investigate

the adaptability of the method to testing materials for which the critical

factor is not diagonal tension, but rather compression which would be

developed in the vicinity of the loading corners of a specimen.

"Structural Behavior of Masonry Infilled Frames

Subjected to Racking Loads" [13]

by C. Carter and B. S. Smith

Chapter 2 7 on Designing , Engineering and Construction with Masonry

reports on a three-year investigation, begun in 1965, into the stiffness

and strength of masonry infilled frames subjected to in-plane racking

loads. Laboratory investigations prior to this study had already succeeded

in describing the three modes of failure which can occur in masonry infilled

frames as a result of racking loads:

"1. local crushing of the masonry or mortar close to

the applied load or at its reaction.

2. tension cracking along the mortar joints or through

the masonry

.

3. shear cracking along the mortar joints."

This investigation was concerned primarily with deriving a method

of predicting the shear failure of the infill panel. Mode 3 was considered

the most probable for "mortar-jointed masonry" because of the reduced

shear strength along the mortar joints.

Two secondary derivations were obtained as a result of the elastic

stress analysis performed by the authors. Infill panels of different

stiffnesses and length -height proportions were analyzed for an assumed

edge- load distribution and length of contact between the surrounding column

and the infill panel. As a result of a finite difference solution of

the biharmonic equation, normal and shear stresses were obtained throughout

the panels. These stress analysis results were used to determine the

magnitude and orientation of the principal shear and tensile stresses.

The principal shear stress computations provided the basis for deriving

a formula for predicting the magnitude of diagonal load necessary to cause

shear failure in the infill panel. The principal tensile stress values

provided a basis for the prediction of the diagonal load necessary to cause a diagonal tension failure (refer above to the description of mode 2).

16
A means of estimating the lateral stiffness of infilled frames was also obtained. It was conceived that the infill panel could be replaced

by an equivalent diagonal strut whose effective width could be ascertained

once the diagonal strains in the panel were known. The diagonal strains were calculated from the stress analysis results. By comparing the theoretical

values of the effective widths with experimental values obtained from

model testing, it was found that the former were excessive. Nevertheless,

a rough estimate of the lateral stiffness can be obtained by assuming

the frame to be pin-jointed, replacing the infill with equivalent struts

and using a conventional pin-jointed frame analysis.

The authors compared the predictions of shear failure as determined

by their derived method with several published test results. The percent

of correlation varied over a wide range, but is not entirely reflective

of the accuracy of the method. The necessity for estimating the value

of the coefficient of internal friction of the various masonry composites

was one factor contributing to the disparity.

This study of the behavior of masonry-infilled frames has resulted

in substantial progress toward the development of a reliable design and

analytical tool. There is a need for refining the proposed methods of

strength prediction to achieve closer correlation with available test

results

.

"Experimental Determination of Eccentricity of

Floor Loads Applied to a Bearing Wall" [47]

by D. Watstein and P. V. Johnson

An exploratory study was conducted by the Structural Clay Products

Institute Research Fellowship to determine the feasibility of measuring

the eccentricities of axial loads applied to load-bearing masonry walls.

The research was performed at the National Bureau of Standards during

1968. The principal investigatory tool was a specially-designed, stresssensitive, steel strut, which was assumed to simulate a load-bearing brick

wall

.

The steel strut was a rectangular tube 4 by f inches in cross section

with a wall thickness of 0.187 in. The strut was 18 in high and had a 3/ 8-in welded steel plate insert at the top providing a closed end. A

1- by 4- by p-in cold-rolled steel plate was bonded to the top welded

plate insert with expoxy cement. The entire steel assembly was capped

with a solid extruded clay brick which served to receive the load. This

assembly was judged to simulate the bearing conditions at the top of a brick masonry wall. The open bottom end was machined normal to the axis

of the strut and was supported on a machined steel plate 4 in thick. The

strut was instrumented with two wire strain gages on each of the 4-in

wide faces.

The underlying thesis of the study was that a calibration curve could

be obtained for the steel strut by applying an axial load of known eccentricity

and measuring the resulting maximum and minimum strains on the opposite

faces of the compressed strut. The calibration load was applied through

a steel knife edge seated in a suitable V block. It was reported that

the eccentricity of the load could be measured with an accuracy of about

1/32 in. The eccentricities were measured over a range of 3 in on each

side of the strut's center line. In this manner, an experimental curve,

relating eccentricity and maximum and minimum strain was obtained. Using

the conventional equations for computing maximum and minimum stress for

combined axial and bending loading and the stress-strain relationship

expressed by Hooke's Law, it was possible to derive a theoretical linear

relationship expressed as:

17
e max - e min

e max + £ min1

where

e = eccentricity of applied load, in

r = radius of gyration, in

c = distance from neutral axis to the outer fiber, in

£ max, £ min = maximum and minimum strain, respectively

Although the experimental calibration curve departed from the theoretical

curve, there was reasonably close agreement between the two.

Once the calibration curve was established, two series of five tests

each were conducted in which a 6 -in deep I-beam was loaded with one of

its ends bearing on the calibrated strut. Throughout these ten tests,

measurements were taken of the rotation of the beam end at the strut and

the corresponding maximum and minimum strains on the strut. The experimental

strain values were used in the theoretical relationship mentioned above

to obtain eccentricities. Then an eccentricity ratio (eccentricity divided

by depth of strut) was plotted against the rotation, in radians, of the

beam end.

The first series of five tests was conducted to study the effect

of bonding a high strength gypsum plaster to the brick bearing surface

atop the steel strut. To study this parameter the tests were separated

into two groups: 1. In the first two tests, constituting the first group,

the I-beam was bedded in unbonded plaster and the responses were measured.

2. In the three tests of the second group, the I-beam was bedded in bonded

plaster. It was observed that while the eccentricity ratio increased

with load in group I, the opposite behavior resulted for the tests in

group II. In fact, at the maximum recorded rotation the average eccentricity

in group II was 42% less than that in group I. Because high strength

gypsum plaster is not a practical bedding material for floor beams, this

phase of the investigation is primarily of academic value.

The second series of five tests was performed to determine the eccentricity

ratio for the same 6-in I-beam supported on varying thicknesses of neoprene

rubber pads. In addition to varying this thickness parameter, two other

variables were introduced. There were two bearing lengths used, 4 inches

in three tests and 2 inches in the other two tests. In order to observe

the effect of intimacy of contact between the supporting strut assembly

and the flange of the I-beam, the two neoprene pads were coated with gypsum

plaster on both sides while the remaining three pads were uncoated. In

the latter case it was specifically noted that intimate contact was not

achieved. As in the first series of tests, five eccentricity-ratio-versusrotation curves were obtained and their characteristics were compared.

The final stage of this investigation involved studying the feasibility

of measuring the eccentricity of the reaction at the base of a wall subj ected

to an eccentric loading. The "wall" consisted of a brick pier 3 9/16

by 7 7/8 inches in cross section. The steel strut used in the first stage

was used as a base for the brick wall. Then, upon applying a load of

known eccentricity, the strains were again measured on the faces of the

strut. In this manner, the eccentricity of the reaction at the base of

a simulated bearing wall was obtained.

18
Although this research effort resulted in a procedure specifically

app licable to measuring the eccentricity of either the load applied to

the top of, or the reaction at the base of a load-bearing masonry wall,

the same approach can conceivably be used for other types of construction.

Some research would be required to test the validity of the assumption

associated with simulating a given wall construction with a steel strut.

"Racking Resistance of Timber Framed Walls" [35]

by T. Ramstad, V. D. Reyers and E. B. Espiloy, Jr.

Based on work done at the Norwegian Building Research Institute,

this report was presented at a CIB international symposium on low-rise

lightweight construction held in Budapest in 1971. The paper presents

the results of 24 racking tests of timber framed walls with different

panel-type sheathing railed to the frame. Wall section specimens of 2.4 x 2.4 metres with no openings were investigated using the ASTM E-72 test

method. The sheathing consisted of 1.2 x 2.4 metre vertical panels which

were butt-jointed and glued, or shiplap-jointed. A calculation method

to determine the strength and stiffness of nailed timber framed walls

with panel sheathing is given and compared with test results. The calculation

method requires the results of an auxiliary lateral nail resistance test

which is also presented. In the supplementary test, the lateral resistance

of a single nail driven through the sheathing material into a wood block

(frame sample) is determined by pulling ^part the test specimen components

transversely to the nail while measuring load with a load cell and slip

with an inductive displacement transducer.

In considering the correlation between experimental results and theoretical analysis of the sheathed, timber framed wall specimen performance,

the nailed joints between studs and sills are assumed to be totally hinged

so that stiffness is attributed entirely to fastenings of the sheathing

panels to the frame members. Calculations are based on the theory that the

deformation and lateral force on each nail is proportional to its distance

from a line of symmetry of the total panel deformation. This line of

symmetry is observed to be the panel vertical centerline. Equations are given relating: ta) lateral force on the wall with maximum force on a nail, Ch) shear deformation with shear stress and (c) slip deformation

with wall geometry and data from auxiliary nail resistance tests.

The calculation method showed satisfactory agreement between computed

and measured maximum loads. However, the method appears to be less useful

for computing horizontal deformations of walls with glued lapjoints than for

those with butt joints. Also the method is limited to wall sections without

openings and to wall sections which are not much longer than the tested

walls

.

Although the calculations for predicting the racking performance

of the tested constructions apparently needs to be improved, it is encouraging

to find a treatment of the racking test which concerns itself with an analytical interpretation of the results. Unfortunately, this aspect

of the problem of improving racking design has not, generally, been examined

as much as the physical test procedures. Such analysis should obviously

be carried along with any development of improved test methods.

"Racking Strengths and Stiffnesses of Exterior and

Interior Frame Wall Construction" [34]

by NAHB Research Foundation, Inc.

The primary objective of this research, conducted in 1971, was to

develop recommendations for performance criteria for racking resistance.

19
The basis for the recommendation was to be the experimental results for

several types of wood-frame wall construction. Another objective of the

investigation was to determine the comparative racking performance of

commonly-used exterior wall constructions, permitted in FHA-Minimum Property

Standards* (MPS) and several exterior wall constructions, not permitted

in FHA-MPS. Also, the results of earlier racking tests (conducted by

NAHB Research Foundation) on typical interior partitions were included

and compared with the test results for exterior walls.

A total of 11 exterior walls were tested in accordance with paragraph

15 of ASTM Standard E72-68 [5] , with one exception; the specimens were

tested in a horizontal position. All frames were built in accordance with

ASTM E72-68. Of the total sample, 4 walls were representative of those

permitted by FHA-MPS, in that they utilized let-in bracing as the principal

means of providing racking resistance. The remaining 7 walls would not

be permitted by FHA-MPS because they contained no let-in bracing. There

were 11 interior partitions tested in the earlier program. A sample size

of 3 was used for each of the 22 specimens.

For the purpose of comparing the performance of different types of

construction, the tabulated summaries of the test results were quite effective.

One table summarized the results for the exterior walls and another summarized

the results for the interior partitions. Because all the results were

to be compared with the performance requirements of FHA Technical Circular

12 [41] , the average deflection and residual deflection at loads of 1200

lb. and 2400 lb. were listed in the table. The average maximum load obtained

for each specimen was also listed. Another useful presentation of results

is the inclusion of "relative stiffness at 1200 lbs" and "relative strength"

values. These values were obtained by calculating the ratio of the results

for all other types of construction divided by the lowest average deflection

and the maximum load, respectively.

The "Discussion" section cited three widely used criteria for evaluating

racking resistance of exterior walls: provisions of the Uniform Building

Code, Housing and Home Finance Agency Performance Standards and HUD 1 s Operation BREAKTHROUGH Guide Criteria. Based upon the racking test results

the consideration of these three criteria and FHA Technical Circular 12,

the authors have offered some recommendations for evaluation criteria

to be used in judging ASTM E72 racking test results. The format for these

recommendations is similar to that found in FHA Technical Circular 12

.

The new criteria would require a minimum ultimate load of 3600 lb. (vs

5200 lb.) and a maximum allowable average racking deflection (at 1200

lb or one times design wind, whichever is greater) , of 0.25 in (vs 0.2 in)

.

The maximum allowable average residual racking deflection, upon load removal,

(i.e., 1200 lb) would be raised from 0.10 in to 0.12 in.

The evaluation approach used in this study illustrates the importance

of establishing relevant performance requirements that can serve as a basis

for comparing the results of structural testing. While the relevance of the

requirements in FHA Technical Circular 12 to specific structural attributes

of a house in service may be questioned, this document does provide a means

of interpreting test results that can be commonly understood. For this

purpose, the use of the ASTM Standard E72 was quite appropriate. The major

shortcoming of the recommendations presented in this report is that they are predicated upon the same rationale that underlies the existing FHA Technical

Circular 12. No new insights are gained as to the correlation between

these requirements and the behavior of an erected house and the influence

*

1 "—

'

Minimum Property Standards for Multi-family Housing, FHA No. 260, Federal

Housing Administration, Washington, D. C, June 1969 , Para. M718-3.7.

20
of cyclical loading on the house's structural performance. The authors

of the report qualified their recommendations by stating that "The Foundation

does not wish to recommend use of the above structural criteria without

some evaluation of the effect of cyclical loading on some of the exterior

wall construction types tested herein.

2.3 Structural Evaluation of Floors

"Testing of Large Diaphragms" [14]

by R. D. Cousineau

This paper presents some guidelines to be applied to testing diaphragms.

The four test parameters elaborated on are: test apparatus, size of test

panels, measurements and presentation of data. At the time of the paper's

presentation, 1959, there had been considerable increase in the use of new materials for roof sheathing and floor decking as compared to the practice

of 10 years before. This introduction of new technology was accompanied

by questions about the value of these new types of construction as horizontal

diaphragms to transmit lateral loads to shear walls. Since the methodology

for testing diaphragms was not standardized, these guidelines represented

a contribution toward the unification of test methods.

Following a listing of some of the types of construction that had

been tested to date by organizations such as the U. S. Forest Products

Laboratory and by researchers at universities, the point is made that the

type of construction will generally be a determining factor in selecting

panel sizes and shapes. It is stated that test panel selection is also

influenced by the "span and spacing of supporting members and the thickness

and strength of covering materials." This statement is specifically applicable

to frame-wall construction. A more general factor influencing the selection

of test panels is the "usual size of panels in building construction."

Reflecting on the absence of a performance standard on which to base the

evaluation of a test panel's performance, it is mentioned that the desire

to compare the results with the performance of the same or similar materials

often dictates the selection of the test panel. Consequently, to compare

the performance of a test panel with that of previously-tested wood-frame

construction it is necessary to test full-scale diaphragms in the range

of 15 to 20 ft wide and 40 to 60 ft long.

Three types of testing apparatus then in common use are described,

with a note about their respective applications. One type of rig is completely

independent of the test panel while another rig depends on certain elements

of the test panel to develop the load. The third rig illustrated is a permanent reinforced concrete test frame useful in testing small diaphragms.

The size limitation on the diaphragm is dependent on the bending moment

capacity of the concrete members comprising the frame.

There are some guidelines presented to aid in the selection of instruments

used for measuring deflections. But, there is no mention of instrumentation

used for measuring loads. Furthermore, there is no discussion of other

important test parameters such as rate of loading, duration of loading

and the type of boundary conditions for the diaphragm.

Although this paper does not go far enough, it is a worthwhile undertaking to review the existing state of knowledge before developing a standard

test method for any type of component. The review in this paper of commonlyused apparatus for diaphragm testing is a good example of what should be

done for other important test parameters.

21
"Shear Diaphragms of Light Gage Steel" [32]

by A. H. Nilson

In this paper the author first presents a description of a series of

full-scale diaphragm tests, on light gage steel systems, conducted at Cornell

University's Thurston Testing Laboratory. The test description is followed

by a general analysis of the test results with regard to safe working values

of shear, limits to horizontal deflection and the effect of varying several

test parameters on the panels' behavior. The first of these diaphragm tests

was conducted in July 1955 and there followed more than fifty tests, utilizing

many types of panels, steel thicknesses, patterns of welding, panel spans and

panel depths. Using the categories of testing recommended by Dorey and

Schriever (see reference [19]), this series of tests could be categorized as both "rating tests" and "research tests". The rating test category applies

because the establishment of working strength values for many different steel

systems resulted from this program. On the other hand, the research test

category applies because one of the principal objectives of the testing was

to catalog the structural performance of such diaphragms.

During the first year of testing a three-bay steel frame was used to

test the corrugated panels made of 16-, 18- and 20-gage steel. The steel

frame can best be described by quoting the paper. "Three 10 ft x 12 ft bays

were established, forming a deck area 12 ft x 30 ft. 12 WF 27 beams framed

in the short direction of each bay, into 10 WF 33 jacking beams running

east-west at the third points of the test area, and into 10 WF 21 reaction

beams running east-west at the extreme ends. The frame was supported on eight

short columns located at the ends of the 10-in beams. The columns under the

two jacking beams were set on rollers to minimize frictional resistance. A

24 WF 84 beam was provided, to the east of the decked area, running in the

north-south direction, and set with the web horizontal. Loads were applied

to the test structure by jacking between the 24-in beam and the jacking beams

previously described, using two 50-ton hydraulic jacks. The reaction beams

at the north and south ends of the deck area were connected to the 24-in beam,

and in turn to the laboratory columns at the extreme ends. The deck panels

were laid on top of the beams, suitably interconnected along the seams and

welded to the beams to form a diaphragm. 1 '

Prior to the installation of the corrugated steel deck, the bare frame

was loaded to a level of 500 lb per jack and the third-point deflection was measured. This step was performed to establish a baseline of stiffness, from

which the resistance to horizontal movement provided by the deck could be

determined. ^

Loads were then applied to the complete diaphragm in increments, and at

each increment, observations were made of horizontal displacement at several

points along the span, tensile and compressive strains in the marginal

beams (i.e. the top and bottom chord of the hypothetical plate girder) , and

relative movement between the adjacent panels.

After completion of the stage in which the multibay frame was used, it was decided to test diaphragms with longer spans. It was desired to increase

the bay spacing from the 10-ft dimension of the first stage to a maximum of

30 ft. After considering the prohibitive expense and difficulty of handling

associated with a multi-bay test frame of dimensions 30 ft x 90 ft, a more

simplistic test scheme was developed. During the first stage of testing it was concluded that due to the presence of both symmetrical loading and geometry

the center bay did not contribute to the resistance to horizontal shear.

Hence, its function was to resist bending moments, not to provide shear

strength. On the basis of this analysis, it was proposed that a single "end

bay, loaded as a cantilever, would yield the same strength values as provided

by the three-bay frame". Furthermore, it was proposed that the maximum deflection of an equivalent three-bay frame could be computed after two corrections

22
were made to the deflection results obtained from the single-bay frame. The

first correction would be a negative one to account for movement of the

cantilever support points. Secondly, an additive correction would have to

be introduced to account for the effects of the missing center bay.

In order to obtain experimental verification for this proposal, a series

of single-bay frames, 10 ft by 12 ft, were tested as a cantilever. The details of these frames were identical to those of some three-bay, 12-ft by 30 -ft frames that had been tested previously. As a result of the close agreement obtained from the two series of tests, it was decided that subsequent

testing of long-span panels would employ the single-bay, cantilever load test

method. From the standpoint of test method development, this evaluative

process contributed significantly to the state-of-the-art as regards diaphragm

testing. The three-bay frame test was quite useful for short-span diaphragms

while the single-bay frame test provided a practical and economic solution to

the problem of testing full-scale, long-span diaphragms.

The latter part of the paper is devoted to an analysis of the test

results. The following subjects are discussed: 1) safe working values of

shear, 2) deflection, 3) effect of panel depth, 4) effect of panel span,

5) relation of material thickness to strength, 6) effect of acoustic perforations, and 7) panel orientation relative to load. The author suggests a direct

application of the test results to the establishment of criteria for safe

working strength values of light-gage steel diaphragms. Recognizing that the

ultimate strength value for a diaphragm system is a definitely established

quantity, one simply has to apply an appropriate load safety factor to arrive

at a working strength value.

This paper, representing one part of an extensive series of diaphragm

tests, is notable in that the test procedures described therein have been

used successfully for the past eighteen years. In fact, modifications of

both methods are presently being considered for adoption as standard test

methods by the American Society for Testing and Materials.

"1966-Horizontal Plywood Diaphragm Tests "[45]

by John R. Tissell

The report on a program conducted by the American Plywood Association

presents information from 19 tests of 16-ft x 48-ft diaphragms of plywood

sheathing as used for roofs and floors. Tests included some diaphragm

constructions not previously tested, such as preframed plywood roof panels

applied over trusses, plywood applied over trusses placed more than 4 ft on centers, and plywood applied directly over open-web steel joists. The

tests were performed to determine the validity of existing design shear

values as applied to Douglas-fir plywood and to determine previously unestablished values for plywood panels made of veneers other than Douglas fir.

Other parameters which were investigated included veneer grade, workmanship, manner of joining panel edges, lateral bearing strength of different nails

and amount of minimum bearing of plywood panel edges on the framing.

The diaphragms were tested in a horizontal position by loading them

laterally along a 48-ft side using 16, equally -spaced, hydraulic jacks.

Observations included deflections measured in-plane and out-of-p lane, and

deformations of the diaphragm tension and compression chords. Instrumentation

for measuring displacements included dial gages and machinist scales, the

latter used in conjunction with taut wires. Strain gages were attached

at the center of the tension chord to measure strain. The loading procedure

consisted of applying six cycles of designated design load followed by six

cycles of double design load and a final loading to the point of failure.

23
Observations were also made of general performance at various locations

in the specimen. Load-deflection curves are given for the first, seventh

and thirteenth cycles of each test.

Conclusions are presented which are based on observations of the various

features of construction tested and are directed toward the development

of design values. A summary of the ultimate-to-design load factors exhibited

by the specimens is tabulated. Recommended design shears for horizontal

plywood diaphragms are derived from the test results, with reference to

all previous tests of horizontal plywood diaphragms and shear walls. The

recommended shear values are related to plywood grade and thickness, width

of framing member, nail size, nail/frame penetration and types of diaphragm

construction. An example also shows how design shears may be derived for

fasteners, spacings or framing species not included in the report or its

references. Although the report is oriented toward the evaluation of specific

materials and construction, the test loading procedure contains features

worth considering in examining methods suitable for improved tests. The

use of full-scale, large size specimens clearly demonstrate their desirability

when there is need to develop service conditions for evaluating interpanel joint performance of multipanel construction.

2.4 Structural Evaluation of Roofs

"Lateral Tests on Full-Scale Lumber and Plywood

Sheathed Roof Diaphragms" [42]

by J. R. Stillinger

This report summarizes the results of research conducted during 1952

and 1953 at the Oregon Forest Products Laboratory to study the behavior

of full-scale wood-frame, roof diaphragms subjected to in-plane forces.

The primary objective was to obtain experimental data that could serve

as a basis for developing rational design methods for the use of structural

engineers. Ten diaphragms, each 60 ft long and 20 ft wide were loaded

to failure in order to determine their strength and stiffness characteristics.

There were ten variables included whose influence on strength and stiffness

was determined. Among the variables cited were: the type of sheathing,

the presence or absence of skylight openings, and the construction of the

boundary members. A secondary objective was to determine the effects of

scale as indicated by comparing previously-obtained (by the same laboratory)

results of testing quarter-scale wall and roof diaphragms with those obtained

from testing the ten full-scale roof diaphragms.

Each diaphragm was positioned with its plane horizontal and was supported

along the 60-ft chords on nominal 4-in by 6-in timbers, which were laid

flatwise on concrete blocks spaced on 10-ft centers. There were no supports

along the 20-ft chords. The loading equipment consisted of two 30-ton hydraulic

jacks that were centered at the third points of the 60-ft span. The jacks

acted against timber loading beams. These beams transferred the load to one chord of the diaphragm through four steel rocker bearings that bore

against four 1/2-in by 10-in by 48-in steel distributing plates. The steel

plates were centered on the fifth points of the span. Thus, the load was distributed over 16 ft of the 60-ft chord. This was thought to be the

most practical representation of a uniformly distributed load. A reaction

assembly was located at each end of the unloaded 6 0-ft chord. The connection

between the chord and the reaction assembly was effected by a hardwood

block whose one end bore against the end post at the diaphragm and other

end was equipped with a steel plate that bore on a solid steel roller.

24
The diaphragms were loaded in predetermined increments and at each

load level, the load was maintained for a short time and then returned

to zero. Seven of the diaphragms were subjected to five additional cycles

of loading and unloading at each load level. According to the author "the

purpose of the repetitive loading was to determine the level at which repeated

loadings would cause significant increases in set or deflection and thus

aid in determining practical working loads."

In order to comprehensively describe the overall structural behavior

numerous deformation measurements were necessary: in-plane deflections

and strains of the unloaded chord, buckling in the framing members located

in maximum shear stress areas, strains in the endpost members, and buckling

in the sheathing material were measured in all diaphragms. There is no discussion in the report about the adequacy of the number of instruments

used to measure deformation. For the purpose of testing a diaphragm against

some performance standard it would be useful to obtain a recommendation

of the number and placement of instruments. The conclusions section neglected

any discussion of a comparison of the results from full-scale testing with

those from the quarter-scale testing. It is a commonly-held opinion that

reduced-scale models are inapplicable to wood-frame construction primarily

because the connections cannot be satisfactorily modelled.

As a result of the cyclical loading tests it was generally concluded

that the first cycle at each load level was the most influential of the

six cycles with respect to set. This conclusion has also been reached

in research conducted on full-scale, wood-frame houses by Yancey [51] and

Yokel [53]

.

"Loading Tests on Full-Scale House Roofs" [44]

by H. J. Thorburn and W. R. Schriever

The behavior of eight typical wood-frame gable-roof structures under

simulated roof gravity loading was studied in laboratory conditions. The

observed strengths of these roofs were to be compared with the results

of tests previously conducted on single frames of identical construction.

The objective of the study was to determine the influence of the sheathing

on the roof's strength. To provide a basis for comparison, the procedure

for the full-scale roof tests was similar to that for the single frame

tests. It is indicated that both test programs were executed at the Division

of Building Research of the National Research Council of Canada, but it

is not stated exactly when the tests occurred.

The geometry was identical for each of the eight roofs; each frame

had a span of 24 ft and a slope of 5 in 12, and consisted of a pair of

rafters, a pair of joists (spliced at mid-span) and a collar tie. The

length of the roofs was held constant at 30 ft. Despite these similarities,

each of the roofs constituted a sample size of one since they differed

in construction details. The type of roof sheathing was one of the test

variables. The sheathing, which was nailed to the rafters, was either

4-ft by 8-ft sheets of 3/8-in plywood or 3/4 -in by 6 -in square-edge boards.

Another variable was the rafter size, which was either 2 in by 4 in or

2 in x 6 in. All joists were 2 in by 6 in and the collar ties were 2 in

by 4 in. Since timber is a material with a relatively high variability

in strength, the sample size is too small to afford quantitative conclusions

about the structural behavior. Therefore, the immediate value of the

results lies in the qualitative conclusions that are drawn. If the strength

data obtained for the eight roofs tested were supplemented by additional

test results for similar structures, a statistically reliable prediction

of strength for typical roof constructions could be derived.

25
The testing was aimed at assessing the ultimate strength of the roofs

and the test loading was applied in only three steps. The roofs were first

loaded to the equivalent of one-half the design load (25 lb per sq ft)

and then the load was removed. In the second step, the load was increased

to the full design load (50 lb per sq ft) and then removed. In the third

step, the load was increased until the roof failed.

The test method used was necessarily ad hoc because no standard test

method for full-scale roofs existed. Judging by the list of equipment

required to conduct these tests on 30 ft-long roof structures, it is concluded

that too few facilities are so equipped to justify a standardization effort.

In this test program, two bridge trusses, supported at each end by columns, were used for the reaction frames. Six hydraulic jacks, which provided

the actual loading force, were suspended from the lower chord of each of

these trusses. The load from each jack was divided by a whiffle tree into

four equal live loads. Although the laboratory dimensions are not stated

specifically in this report, it is concluded that the minimum space requirement

was 45 ft by 35 ft by 14 ft. Thus, only a few laboratories in the U. S. can satisfy the space requirements, not to mention the loading capacity

and equipment needs. It therefore seems desirable to provide a basis for

testing a smaller roof specimen. As a first step toward developing a test

method for relatively small specimems, the effects of scale must be studied

in some detail. J

"Strength and Behavior of Light-Gage

Steel Shear Diaphragms" [27]

by Larry Luttrell

This research bulletin reports on a laboratory investigation conducted

at Cornell University to observe the response of light-gage steel diaphragms

to in-plane shear force and to determine the influence of certain variables

on the response. This investigation was part of an extensive research program sponsored by the Americal Iron and Steel Institute (A.I.S.I.), for the

study of light-gage, cold-formed steel structures. The results of the

constituent investigations provided the bases for an A. I. S.I. publication

entitled "Design of Light-Gage Steel Diaphragms."

The author noted that the state of the art with respect to predicting

the behavior of diaphragms by purely analytical means was impeded by the

large number of variables and parameters that must be considered. Hence,

there is a need for structural test data to augment the existing analytical

tools. The scope and objectives were defined to provide some of the needed

information. The scope of the investigation included the testing of 73 full-scale (of dimensions 12 ft by 10 ft, 6 ft by 6 ft and 10 ft by 12

ft) and 13 smaller (from 17 3/4 in to 28 in long and 24 in wide) diaphragms.

The investigation was limited to diaphragms made from open fluted and

standard corrugated panels. No attempt was made to consider cellular

panel diaphragms nor diaphragms with filler material. The structural

characteristics under consideration were shear strength and shear rigidity

with respect to in-plane forces. The test objectives were: 1) to establish

shear strength values for typical light-gage steel diaphragms; 2) to determine

the variation of shear deflection with load; 3) to determine the maximum

reliable strength under cyclic load and 4) to determine the influence of

diaphragms in a building.

In general the diaphragms consisted of a steel test frame, covered

on one side with the light-gage steel ribbed or corrugated panels. The

panels were fastened to the frame with screws, welds or back-up fasteners

such as lock rivets. The size of the perimeter framing members and of the

purlins was included in the list of variables. The large diaphragms were tested as horizontal cantilevers with two point reactions. The reaction

26
at one corner simulated a theoretical pinned connection while a greased

bearing plate at the opposite support corner represented a roller support.

The load was applied through the use of two 50-ton hydraulic jacks, whose

axes were in line with the plane of attachment between the panels and the

frame. The 13 smaller frames were all tested in a 400,000 lb testing machine

as vertical cantilevers. Except for this difference in setup, the testing

procedure was the same for both the larger and smaller diaphragms.

In view of the first two test objectives, various diaphragms were statically loaded either by one of the hydraulic jacks or in the testing

machine in increments from zero to failure. To measure the effect of cyclic

loading on the ultimate strength of the diaphragms, either pulsating or reversed loads, with amplitudes equivalent to chosen percentages of the

expected ultimate load, were applied for various numbers of cycles. The

expected ultimate load was based on the results of an identical diaphragm

loaded statically to failure. The pulsating loads cycled between zero

and +0.4 of the expected ultimate load for 5 cycles. The reversed loadings

were applied through the alternate use of the two hydraulic jacks. The

loading sequence was performed by first increasing from zero to some percentage

of the expected ultimate, unloading, and then loading to the same percentage

in the opposite direction. The numbers of cycles of reversed loading were

5,25 or 29 and the three percentages of ultimate were 30, 40 or 60. After

the specified cyclic loading had been applied, the diaphragm was loaded

statically to failure by one of the hydraulic jacks.

Dial gages were attached to three corners of the respective test frames

to measure the in-plane deflections. Four gages were sufficient to account

for support movement in the process of determining the total diaphragm

deflection. The assumption was made that the total corrected deflection

is composed of two components, namely bending deflection and shear deflection.

A method was derived for computing the stiffness of a given diaphragm,

based on the characteristics of the resulting load-deflection curves. The

author defines the stiffness as the slope of the load-deflection curve

in the nearly linear region below approximately 0.4 of the ultimate load.

The author also illustrates, by numerical example, the use of cantilever

test results in predicting the shear deflection of a diaphragm. While

the author does not provide any commentary on the evaluation of the cantilever

test method, its limitations are alluded to in the American Iron and Steel

Institute (New York City) publication, "Design of Light-Gage Steel Diaphragms".

In Section 3.2 (Methods of Tests) of that publication, it is stated that

either the cantilever test or a simple beam test (involving two-point concentrated loading) is acceptable for obtaining the necessary test results.

However, it is implied that although the simpler cantilever method is acceptable

for predicting the shear strength of multibay structures, it may not yield

reliable results for predicting the deflection of those structures. The

problem of predicting the deflection for multibay structures is more complex

because of the kinematic indeterminacies introduced by the interior frames.

Hence, equations must be generated to account for the deflection compatibility

that must exist between the diaphragm and the interior frames.

One example is presented in the appendix of the report to illustrate

the use of the experimental value of the modulus of rigidity in the determination of diaphragm deflection. It is seen that a general approach to predicting

the total in-plane deflection of a diaphragm in a structure would involve

obtaining the experimental value of the modulus of rigidity and subsequently

using existing analytical methods to determine the shear and bending deflection

components

.

27
2 . 5 Structural Evaluation of Complete Houses

"Strength of Houses" [48]

by H. L. Whittemore, J. B. Cotter, A. H. Stang and V. Phelan

This report, issued in 1949, was the forerunner of practically all

domestic attempts at explaining the structural behavior of houses by physical

testing. This analytical study resulted in some recommendations for a comprehensive design procedure for one- and two-story frame houses based

on engineering principles.

Basic information on wind forces, snow load, dead load and floor

live load was synthesized prior to the determination of a full set of

design loads for the structural components of two typical house constructions.

This was done for three geographic locations of diverse environmental

characteristics. A procedure for determining the "allowable" (working)

loads applicable to different types of construction was discussed. The

determination of an allowable load from the laboratory data was based

on considerations of strength and safety only. This procedure was applied

in assessing the allowable compressive, concentrated, racking and impact

loads for 100 house constructions that had been previously documented

in National Bureau of Standards series of Building Materials and Structures

(BMS) reports. For example, allowable racking loads were expressed in

terms of "racking moduli," as computed from the test results reported

in other BMS reports. The design loads assigned to the walls, floors

and roofs of the two houses were compared with the allowable loads and

the comparisons were discussed.

In order to simplify the analysis of load distribution to the various

components, four basic assumptions about component behavior are stated

in the report. These simplifying assumptions relate to the assumed action

of floors as rigid diaphragms in resisting in-plane loads, and of floors and

walls and roofs as simple beams in resisting transverse loads; the underlying premise is that a house can be considered as a statically determinate

structure for all load conditions except racking. None of the assumptions

have been substantiated by test results. Nevertheless the analyses presented

in this report constitute a substantial effort toward the understanding

of the interactions that occur between various components and their connections

in house construction. Unfortunately, since this study, little basic

research has been undertaken for the development of rational design methods

for houses.

"Evaluation of a 40-ft by 100-ft Frameless Straight Sided

Prefabricated Metal Utility Building" [29]

by the U. S. Naval Civil Engineering

Research and Evaluation Laboratory

This report presents the results of an evaluation test conducted

in 1952, on a frameless, metal utility building submitted to the U. S. Naval Civil Engineering Research and Evaluation Laboratory (now called

the Naval Civil Engineering Laboratory) . The evaluation was with respect

to performance requirements related to naval activities. One of the requirements was that a standardized utility building must be structurally adequate.

The report dealt with the structural performance of the building under

simulated snow loading.

The prototype structure was 40 ft-0 in by 100 ft-6 in in plan, 14

ft-0 in high at the eave and 19 ft-4-1/2 in high at the peak of the gabled

roof. The building was designed to be anchored to a concrete footing

28
or slab with anchor bolts. The roof and wall panels, consisting of corrugated

galvanized steel, were all 41 inches wide and 7-1/2 inches deep. Each

end wall contained 2 windows, a metal louver and a sliding door.

The design snow load was 20 psf according to the appropriate military

specifications. The overload factor was established as two for the test.

Thus, the structure was expected to perform adequately for the application

of vertical loads equivalent to 40 psf. The loading was provided by hydraulic

rams and effected by a whiff letree assembly located on the underside of

the roof.

A number of electrical resistance strain gages were used to obtain

data for stress calculations, while deflections were measured by deflectometers

developed at the laboratory. The roof was loaded in 10 percent-of -design

increments until the occurrence of a buckling failure in the roof panels

at a load equivalent to 60 percent of the design load. Failure of the

roof panels was attributed to the lack of a structural member for transmitting

the forces from the ridge channel to the end walls. Also the center

of the ridge channel underwent a relatively high vertical deflection,

thereby tending to pull the end walls inward. Subsequent to the release

of the failure loading, some wooden columns were placed under the ends

of the ridge channels. The loading was then applied to a level equivalent

to 100 percent of the design load.

On the basis of the test results it was concluded that there were

three structural factors in the building contributing to the support of

the loading. These three factors were identified as rigid-frame action,

roof -beam action and roof -diaphragm action. The configuration of the

structure was held to be too complex to afford a determination of the

relative contribution of these factors in distributing the load, despite

the use of considerable instrumentation.

There is one feature in this evaluation that warrants consideration

when developing a test method for full-scale prototype testing. The use

of a whiffletree assembly to transfer the load from loading devices such

as a hydraulic ram to the surface of the strucure is cited in several

other reports [18] , [44] . None of the authors discusses the advantages

and disadvantages of employing such a system. But, a study of alternative

loading methods would include a comparison of trade-offs.

Several other similar evaluation tests were conducted by the same laboratory during the same period. However, they do not offer any additional

information about structural behavior or test methodology.

"Rigidity and Strength of Houses Built of Plywood

Stressed Cover Panels" [28]

by R. F. Luxford and E. C. O. Erickson

This report presents details of a racking test performed on one fullscale, single-story house at the U.S. Forest Products Laboratory. The

outside dimensions of the test unit were 29 ft-4 in by 21 ft-0 1/2 in.

There was one partition parallel to the side walls that was continuous

between the end walls. To one side or the other of this long partition there was a total of four partitions parallel to the two end walls, having a total length of 36 ft. The structure was formed of wood, stres sed-skin

panels. Each wall panel was 4 ft by p ft in size and consisted of two 1/ 4- in faces of 3-ply Douglas fir plywood glued to 3/ 4-in by 1 3/ 8-in

studs spaced on approximately 12-in centers. Panels were fastened to

each other using vertical mullions with parallel grooves, but this was not a positive connection. Floor and roof panels utilized 2-in by 6-in

29
joists spaced on 24-in centers with an upper face of 5/ 8-in plywood and

a lower face of 3/ 8-in plywood.

The experiment was conducted about 1954 to evaluate the structural

behavior of the house when subjected to simulated wind forces. Based

on the results of this field test it was believed that predictions could

be made for the performance of panelized houses in high winds. The design

wind pressure cited was 20 lbs per sq ft , which is associated with a wind

velocity of 8 0 mph. There were no performance requirements for structural

stiffness or strength that provide a basis for evaluating the results.

Furthermore, the authors acknowledged that they knew of no data from similar

tests performed on more conventionally constructed houses with which

to compare the results they obtained.

The method of loading was dictated by an unrepresentative construction

detail. The prototype house was connected to a "temporary" foundation

and hence did not have sufficient anchorage or resistance to overturning

to permit the application of external lateral forces. Therefore, a method

of applying diagonal, in-plane forces to the 21-ft shear walls was used.

Loading was effected by systematically tightening a nut on each of four

diagonally-installed threaded rods two of which were attached outside

of the end walls. The other two rods , placed inside the house, were spaced

equidi stantly from the exterior rods. A dynamometer was inserted into

the lower 1/3-length of the rods to measure the force. The equivalent

wind pressure could be calculated from the measured forces and known geometry.

The lateral deformation was determined by measuring diagonal shortening

in the two 21-ft end walls. For this purpose a telescoping wooden rod,

to which a "scale" (interpreted to mean a graduated ruler) was fastened

to the corner mullions at each end of the building in "approximately the

same plane as that of the four loading rods. " Relative vertical movement

between the end wall panels and the respective mullions that connected

them was also measured. Starting at an equivalent wind pressure of 34

lbs per sq ft, the horizontal movement of the roof was measured by fastening

a scale to one corner of a roof panel and reading the change from a known

initial point on the scale with a transit.

The in-plane loading method and the indirect method of measuring

horizontal deflection (drift) constituted a practical approach to fieldtesting a full-scale prototype structure. However, the details of the

deflection-measurement device are too scant to assess the reliability

of the deflection data. The smallest graduation of the scale is not stated

and the degree of accuracy of the telescoping wood device cannot be ascertained.

These shortcomings notwithstanding, the use of more accurate instrumentation

may not have been justified because of the increased cost and complexity.

"Structural Tests of a House Under Simulated Wind

and Snow Loads" 118]

by D. B. Dorey and W. R. Schriever

Using a one-story wood-framed house (36 ft by 24 ft) , built in 1948,

a field test program was undertaken by the Division of Building Research

of the National Research Council of Canada. The two main objectives of

this study were: "(1) to obtain information on the strength and stiffness

of a full-scale single-story house without exterior sheathing; and (2)

to obtain experience in full-scale testing and in evaluation of the strength

of houses." The design loads for wind and snow, as indicated in the 195 3 edition of the National Building Code of Canada, were applied. This testing

did not strictly fit into either of the categories of: proof testing

Ci.e. testing to a factored load equal to or greater than the design load,

30
but less than the required ultimate load) or ultimate load testing because

it was decided that the maximum loading would be limited by the occurrence

of "relatively minor damage."

In discussing the loading apparatus, the authors state that two loading

methods were considered well suited for the field conditions. The possible

use of steel cables with one end anchored to the ground and directed over

a column to a load mechanism on the other was compared with the possible

utilization of a rigid reaction framework that envelopes the test house.

It was concluded that the latter method was more desirable. In discussing

the merits of the two methods the authors do point to the relative design

and assembly simplicity of the first method. However, it has the disadvantage

of being difficult to adopt for the application of outward thrusts normal

to moderately sloping roof surfaces. It is stated that "with a rigid

reaction framework spanning the test house, simultaneous inward or outward

thrusts may be applied and controlled from a central position without

altering the test house very much." A whiff letree assembly was positioned

over the roof and on the side walls to reasonably effect the uniform load

assumed in design. This means of representing the design load was decided

upon in lieu of a system employing concentrated loads; with the latter

system, the maximum shear and bending moment obtained in the design can

be represented.

The loading phases were ordered so that each subsequent phase was more severe than the preceding one. The four design conditions simulated

were

:

(a) wind load acting alone -

(b) wind load acting alone -

(c) combination of wind load

with internal suction

with internal pressure

and one-half design snow load.

(d) snow load acting alone.

The simulated wind forces were derived by transforming the wind velocities

into equivalent static pressures acting on equal areas of the side walls

and roof slopes. The initial simulated wind force corresponded to a wind

velocity of 70 mph. The subsequent simulated forces corresponded to wind

velocities of 80 mph and 90 mph, the latter being the design velocity.

After the force associated with the design velocity had been sustained

for 1 hour it was released and reapplied. The loading was further increased,

in increments of 10 mph, up to a value corresponding to a wind velocity

of 120 mph.

A system of pulleys and wires was used inside the house to measure

the resulting deformations. Horizontal and vertical displacements along

four deformation planes were measured by running piano wire over a system

of low-friction aircraft pulleys. The practice of instrumenting so-called

deformation planes with vertical and horizontal deflection recorders has

also been employed by Yancey [51] in laboratory racking tests performed on a wood framed housing unit. This technique constitutes an efficient use

of a limited number of instruments in that relatively complete deformation

data can be obtained for discrete planes through the test structures.

These planes can be selected to correspond to the perimeter of shear

walls or they may be located at other points of interest along the structure.

Using the deformation values obtained from these data points, the behavior

of the entire test structure can usually be interpolated. To facilitate

the detection of cracks as evidence of structural distress, thirteen plaster

telltales (i.e. "returned layers of gypsum plaster") were used at the junctions

formed by intersecting walls and the ceiling.

31
The test structure possessed one distinguishing feature in that the

exterior sheathing was purposely omitted. Thus, its stiffness and strength

performances can be compared with those of sheathed, wood-framed houses

to gain insight into the contribution to racking resistance offered by

the sheathing.

A summary is given on the structural test results relating to the effect

of the sheathing on racking strength and resistance to snow loads. The authors

point out that before definite conclusions can be reached, numerous similar

tests are necessary because structural evaluation of house structures is

made difficult by such factors as complexity of form, and variations in

materials, workmanship and methods of construction. It is likely that

future tests would be conducted in laboratories rather than in the field,

because of the time and cost required in constructing test equipment around

an existing house, as done in this instance.

"Full-Scale Tests of Pre-Cast Multi-Story Flat Construction" [21]

by A. J. Frances, W. P. Brown and S. Aroni

A single specimen of three-story, pre-cast concrete housing was tested

in Melbourne Australia in 1956 as a part of a feasibility study for the

Housing Commission of Victoria. The central question underlying the experiment

was; "could the height limits on Commission-sponsored housing be extended

from conventional two-story construction to three or more stories?" The

authors investigated the behavior of a prototype three-story unit under

a combination of lateral loading and gravity load equivalent to the contribution of 4-1/2 stories. The magnitude of the gravity load was limited by

the bearing stress capacity at the base of the ground story walls. Field

testing measures of an ad hoc nature were employed since no standard test

method existed.

The test specimen was constructed according to the current practice

to a height of three stories (28.5 feet). Then, the effect of an additional

1-1/2 stories of dead load was simulated by superimposing five complete

layers of floor slabs onto the uppermost story bearing walls. The test

structure measured 27 ft by 26 ft in plan.

The investigators acknowledged that it was necessary to compromise

with the test loading since the design shears and moments for a fivestory structure could not be identically matched in the three-story prototype.

It was decided that the lateral loading in the test structure be app lied

in a manner to represent the overturning moment calculated for the ground

floor level in a five-story structure using the design loads specified

in the Uniform Building Regulations of Victoria. The maximum lateral

force applied during the test program was equivalent to 1.5 times the

design wind load. Force was applied to a loading beam at 12 equally spaced

locations along the top of the designated windward side of the structure

through turnbuckles attached to high-strength stainless steel wires. The

load in each wire was measured by a device consisting of a short length

of high-strength silver steel rod, with gage points 8 in apart, to which

a demountable mechanical strain gage was attached. In the authors' opinion,

the error in reading the load in each wire was probably + 5 percent or

less. The temperature during the testing exceeded 90 °F and so that it was necessary to apply a correction factor to compensate for its effect on

the load measurements.

Lateral deflection along the top of the structure was measured at

three points by deflectometers with dial gages. The lateral movement

between the base of the windward and leeward walls and the adjacent floor

slabs was measured at each corner of the building, on the second and third

floors by the use of dial gages.

32
An analysis of the structural behavior, based on the measurements

obtained and the visual observation of cracking patterns, provided the

bases for some recommendations on the use of this type of construction

for taller buildings. Some understanding of the lateral stability of

buildings of this type was also gained.

For the purpose of loading a three-story structure at its top, under

field conditions, the loading method used was a practical selection. It seems relatively easy to apply the load in increments as well as to release

the load quickly when necessary. However, it is doubtful that the accuracy

of load measurement was less than + 5 percent. Instead of measuring the

strain values in the steel rod, better accuracy could probably have

been achieved by using a load indicating device operating on the same principle as a load cell.

"The Wood-Frame House as a Structural Unit" [50]

by National Forest Products Association

A full-scale house was subjected to several combinations of simulated

gravity and lateral wind forces to evaluate its structural performance.

The one-story, three-bedroom unit was constructed with trussed roof framing

and wood wall and floor framing over a full-story height basement constructed

with 8-in concrete block walls. The testing program was conducted during

1963 and 1964 at Virginia Polytechnic Institute. The 1963 phase of the

program consisted of three parts.

Part I involved the measurement of floor deflections , under simulated

gravity live loading, for 14 stages of construction. The performance

of the floor system was measured while several components like partitions

and structural elements such as 1 in by 8 in scabs (ties) were added to

the assembly.

In part II, floor vibration tests were performed on 43 joists for

the same 14 stages of construction as specified in part I. The response

was induced by suddenly releasing a 688-pound force, which was applied

equally to two adjacent joists. Results were presented for the frequency,

amplitude and duration of response.

Part III dealt with a study of the interaction of the various components

and their contribution to overall structural stiffness with respect to

simulated wind loading. Racking tests were performed during seven stages

of dismantling. By means of hydraulic rams, acting in tension, cycles

of simulated wind loading were applied to all four exterior walls and

on the roof surfaces. All surfaces were loaded to the same equivalent

pressure in 4 psf increments up to 16 psf. Each increment was repeated

twice during a 6-minute period before going to the next level. Horizontal

deflection was measured on the two leeward walls for each increment of

load. A simulated gravity load equivalent to the simulated wind pressure

at a given increment was applied and maintained for five minutes. Then

the vertical movement at the crown was measured. Results were presented

for leeward wall movement, 4 feet above the floor, for each stage of dismantling.

It was necessary to correct the measurements of horizontal deflection

because the deflection recorders were mounted on the steel reaction frame

to which the hydraulic rams were attached. By using transits, the horizontal

deflection of the reaction frame was measured at points where the deflection

recorders were mounted. The corrected horizontal deflections were obtained

from these two sets of data. The authors have attempted to quantify the

degree of inaccuracy of the deflection-measurement procedure. "The degree

of accuracy for the horizontal measurements is considered + 0.05 inch

33
because some transit readings could only be read to the nearest millimeter,

or 0.04 inch. The deflection recorder has an experimental error of + 0.01 inch." Their conclusion about the effectiveness of the measurement

procedure to fulfill one of the test objectives is stated as follows.

"While this degree of accuracy would not be acceptable for experiments

with small test specimens under controlled atmospheric conditions, it

is considered accurate enough for the full-scale house tests. Greater

accuracy is always desirable, but the difficulty and cost of attaining

it in this case did not seem to be justified."

The results of part III suggested that a typical wood-framed house

may resist racking in several ways. The contributions of the roof sheathing

and ceiling diaphragm to resist horizontal movement were evaluated, but

the additional resistance supplied by the partitions could not be distinguished.

In 1964, the house was disassembled and part I (i.e. testing the

floor for gravity loading) was repeated for 2 of the original 14 stages

of construction. The time lapse between the corresponding 196 3 and 1964

tests ranged from 9 to 15 months. The objective of the re-testing was

to observe the repeatability of test results after short-term exposure

to the effects of the environment.

Several aspects of this test program are cases-in-point of recommended

procedure for any test method. By repeating a given load several times

it is generally possible to determine if a test specimen exhibits elastic

response. The application of three cycles should be sufficient for wood

structures. It is good practice to instrument for the measurement of

possible movement of the datum line so that a correction factor can be

applied to the results. While the re-testing of a structure for all stages

of construction seems impractical, some re-testing is warranted when a single sample is used. The reliability of the test data is dependent

on its reproducibility.

"Effect of Wind Pressure on the Racking Strength

and Stability of a One-Story,

Gable-Roof Building of Sandwich Panel Construction [17]

by Simon H. Diskin, Consulting Engineer

The performance of a prototype structure as manufactured by Panelfab,

Inc., was evaluated under racking loads in 1966. Field-testing techniques

were used to subject the single-story structure to simulated horizontal

wind forces. A series of concentrated loads were applied at the eave

line on one side of the building and the resulting horizontal and vertical

deflections were measured at several locations.

The primary purpose of the test was to observe the racking behavior

of the end walls and to determine their strength and in-plane stiffness.

The test structure consisted of a shell constructed of panels; it contained

no interior partitions.

A secondary purpose was to study the behavior of the structure as

a complete unit. The objective was to establish a rational design method

for individual panels.

The test structure was 20 ft-4 in by 35 ft-4 in with an 8 ft- 0-inhigh wall and a gable roof that sloped 3 in 12. The wall panels were

of 2-inch nominal thickness with 26-gage steel facings adhesive-bonded

to a honeycomb core. The roof panels were 3-inch nominal thickness with

24-gage steel facings and a honeycomb core. The wall base channels were

anchored to an 18-in thick concrete wall footing placed continually around

34
the building. J-type anchor bolts were used at the four corners and lag

bolts with expansion shields were used for intermediate anchorage.

The loading system consisted of four loading cradles suspended by

vertical steel cables which passed over pulleys. Each pulley was located

on top of a pipe column whose axis was oriented 45 degrees to the vertical.

The cables transmitted the vertical dead weight from the cradle to a horizontal

force at the eave line. Incremental forces were effected by adding solid

concrete block units to the cradles. After applying a pre-load, the load was increased by increments to a test load equivalent to two times the

specified design wind pressure. The test load was maintained for 24 hours

and then removed

.

Horizontal deflection measurements were obtained at eight eave line

stations for each increment of load. The deflections were also obtained

at the end of a 24-hour period during which the test load was held constant.

The deflection recovery, expressed as a percentage of the deflection under

test load, was determined 24 hours after the removal of the test load.

Vertical deflections at the ridge were also measured.

The simulated wind load was derived from a static analysis of the

designated windward wall for the design wind pressure. The portion of

the assumed uniform pressure that is reacted at the base of the wall was disregarded in computing the test load. Therefore, the simulated wind

load applied at the windward eave of the test house was equivalent to

one-half the total design wind force acting on the structure. This simulation

was justified by the fact that the wind pressure on the lower half of

the windward wall did not contribute to the racking force at the top

of the end walls. Also, the overturning moment caused by the test load was equivalent to that attributed to the design pressure acting on the

entire windward wall. However, the base shear in the test arrangement

was only one-half the design base shear. This shortcoming in the load

simulation was inconsequential to the objective of evaluating the racking

performance of the end walls. The report contains an analysis of the distribution of forces through the structure to the end walls and this analysis

is followed by a simple design method for individual panels.

The use of dead weight as the source of the test load was apparently

justified by the nature of the test. This was essentially a proof test,

consisting of a static overload sustained for a relatively short period

of time. Although, the load was applied in increments up to the test

load there were no cycles of load-removal and reapplication involved.

When such is the case, handling the deadweight material may become a substantial

problem. The total test load was relatively low, less than 8000 lb,

thereby further justifying the loading method used. This report provides

good information on the distribution of lateral forces through a simplyconstructed sandwich panel building.

"Model and Full-Scale Tests on a Five-Story Cross Wall

Structure Under Lateral Loading" [40]

by B. P. Sinha, H. P. Maurenbrecher and A. W. Hendry

The authors' primary objectives were to compare test results from

a full-scale multi-story masonry building with those from a one-sixth

scale model test and those obtained from existing theories. Prepared

in 1970, the report presents an unusual, yet economical, means of providing

large horizontal load reactions over a great height by using the face

of a stone quarry. Such a choice, of course, requires the test structure

to be built at the quarry site. The walls were built of brick masonry

according to cited British specifications. The five floor slabs were of

precast reinforced concrete with a cast-in-place reinforced topping.

35
A portion of the quarry face was surfaced with concrete for a height

of 46 ft against which lateral loading jacks reacted at each floor and

roof line. All jacks were operated from a central pump; roof -line jacks

exerted half the load applied by floor-line jacks. Each jack load was measured by a load cell.

Scaffolding was erected around the building for access and for mounting

instrumentation (although no access was permitted during testing) . The

scaffolding was free of the structure and tied firmly to the quarry face.

Wind effects on scaffolding and instruments necessitated calm weather

for testing. All deflections at slab level were measured by dial gages.

On the loaded side of the structure, dial gages were attached to the scaffolding and read by means of theodolites; on the opposite side, a pulley and

wire system transferred deflections to dial gages mounted at ground level.

Strains were measured at locations on ground floor walls by hand-held

mechanical gages with 12-in or 24-in gage lengths. The maximum lateral

loading corresponded to a 106 mph wind speed.

The full-scale testing was primarily intended as research for confirmation

of results obtained from the model tests. As such it was designed as a detailed single undertaking rather than as a repeatable standard procedure.

Nevertheless, consideration of certain of its features is helpful in the

development of improved test methods. For example, comparison of the

results with results from earlier single-story tests shows clearly the

increased rigidity caused by the precompression due to additonal stories,

a factor to be considered in recommending standarized procedures.

"Test and Evaluation of the Prefabricated Lewis Building and

Its Components-Phase 1, Part 2-Full Scale Building Tests" [36]

by T. W. Reichard and E. V. Leyendecker

This report was prepared to document erection problems and the load

capacities of a relocatable building assembled of prefabricated sandwich

panels. The report serves as a good illustration of full-scale structural

testing in the laboratory.

The test structure was a 20-ft x 32-ft one-story building having

a gable roof. The major components of the building were 4 -ft wide panels

constructed with aluminum skins and paper honeycomb cores, aluminum extrusions

for framing and rigid vinyl cleats for joining; sheet metal screws and

bolts were also used for fastening.

The building was erected on a reinforced concrete test frame that

was cast on the floor of a large environmental test chamber (chosen for

thermal tests) . This foundation-type test frame was constructed to simulate

the pier support called for by the building design. Erection of the test

building was performed as a field operation in an attempt to expose and

subsequently eliminate assembly problems.

Loading of the building simulated the effect of roof loads and lateral

wind forces. Pressurized air bags applied load normal to the roof. Because

of the flat slope of the roof (2.5 in 12) the vertical roof pressure was

98 percent of the normal roof pressure. The vertical pressure was, therefore,

assumed equal to the normal pressure. The air bags reacted against an overhead timber framework that was tied down to the laboratory fLoor by

vertical steel tie rods passing through holes in the test building. Air

pressure in the bags was recorded with a low-pressure, strain gage, pressure

transducer. Vertical movements of the roof were measured with a surveyor's

level by sighting on lightweight leveling rods suspended from the roof

ridg e line.

36
Wind forces on the building were simulated by concentrated loads

applied at the eave line on the leeward side. These loads were developed

by tension -type hydraulic rams operated from a common manifold, and a combination of cables and pulleys arranged to pull with equal forces at

four points on the leeward eave. The load on the building was calculated

from the ram pressure which was measured by a high -pressure, strain gage,

pressure transducer. Lateral movements of the windward and leeward walls

were measured by linear variable differential transducers (LVDT) , whose

signals were fed into a data processor and recorded as perforated tape

as well as printed copy.

Separate racking tests were performed to determine performance of

the building under design load, loads greater than design load, and finally,

a designated ultimate load. The racking test procedures utilized both

cyclic and increasing, gradually applied (i.e. static) loadings. The roof

vertical load test was performed with an increasing, static loading procedure

to determine load capacity.

Results of the various tests are discussed in detail and the discussion

illustrates well the completeness with which information can be derived

from such tests. Some of the tests described also serve to show that

reasonably accurate information related to performance of the whole structure

was obtained even though only part of the structure was loaded.

Although very complete in its approach, the overall test included

several procedures that were devised as expedients in this instance and

could readily be improved. Because of its very completeness and detail,

however, it is questionable that such a test lends itself to recommended

standardized practice. Nonetheless, the discussions of structural failures,

in relation to the procedures used, provide helpful background for developing

improved test methods.

"Tests and Evaluation of the Prefabricated Lewis Building and

Its Components-Phase II" [26]

by E. V. Leyendecker and T. W. Reichard

This account deals with structural tests of a relocatable building

which differed in layout from that reported in reference [36] . This building

was 20 ft by 48 ft, erected in two 24-ft long modules and tested without

the 20-ft wide end walls in place. This open-ended arrangement of the

2-module structure was used to determine the behavior of an elongated

building consisting of an indefinite number of modules. Besides fullscale structural tests, numerous other tests of structural components

and of material coupons are described. The latter used ASTM Recommended

Methods C393, C273, C297, and C365 to determine, respectively, flexural,

shear, tensile and compressive strengths of structural sandwich construction.

These tests were performed in duplicate sets with specimens that had been

conditioned at 73°F and 50%RH or 100%RH. The structural test procedures

have many innovative features, thus making the report a particularly useful

reference.

Since the full building was used in performing numerous tests, a determination of load capactiy was not included. The series of tests was conducted

with the building erected on, and attached to the tie-down floor of a structures testing laboratory. Again, the supporting piers simulated those

of field installations. Tests included the simulation of wind forces

using concentrated loads along one eave line; and the testing of the roof

as a diaphragm. For the latter, a horizontal concentrated load was applied

at the mid-length of the eave line on one side and reactions were supplied

at the two ends of the opposite eave. All loading of the full-scale structure

was accomplished by hydraulic rams (connected to a common manifold when

37
necessary) and all displacements were measured by linear variable differential

transducers (LVDT's) with signals recorded by an automatic data processor

as perforated tape and as printed copy.

Sandwich panels, measuring 4 ft x 8 ft were simply supported and

loaded uniformly, using air bags. The panels were flexed with the air

bag between the specimen and the tie-down floor. The test floor was used

to hold down the ends of the panels with simple supports. Additional

flexure tests were performed using specimens made of three panels (each

4 ft x 14 ft) cleat ed side by side and bridging the same span. The manner

of loading and the instrumentation were similar to those of preceding

tests except that only the two outer panels were loaded. This was done

to determine the load that could be transferred through the joining cleats

to an unloaded panel. A third group of flexure tests made use of individual

4-ft by 8-ft panels, simply supported as beams, but uniformly loaded by

a vacuum on the tension surface rather than by air bag pressure on the

compression surface. This loading technique was used to determine if

the tension facing would part from the core material before the panel

could develop the maximum load determined by air-bag flexure loading.

Again, LVDT's and strain gages were used to measure deformations.

Before installation into the test building, a 24-ft ridge beam was tested in flexure in a novel way. This prefabricated component contained

a 24 -in deep web of honeycomb sandwich panel construction and continuous

flanges made of aluminum extrusions riveted together. The beam was loaded

by applying air pressure to a fire hose placed between the beams in an inverted (from actual use) position and the test floor. The beam was held

to the floor at the ends through simple supports applied to the tension

flange.

Descriptions of many testing techniques in this reference make it

useful for evoking ideas to improve structural test methods. However,

even certain of these need deliberation if considered for adoption. For

example, the use of a fire hose for loading, presents the problem of a changing pressure-contact-area as it inflates with specimen deflection —

a factor which is more critical in this case than in using wide, large

area air bags.

"A Facility to Evaluate Three-Dimensional Performance of

Modules of Houses" [8]

by K. H. Boiler

The report describes a facility at the U. S. Forest Products Laboratory

by which the strength and stiffness of house modules up to 8 x 12 x 24

feet can be evaluated. The facility consists of a structural steel framework;

a system to apply loads by air bags and hydraulic rams simulating service

conditions; and an electronic system for acquiring data.

Although it is primarily a description of equipment, the report contains

opinions on the desirability of three-dimensional testing of structures.

In this regard, it contributes to what should be an impartial approach

in considering the problem of improving test methods. The author stresses

the need for adopting a composite approach to structural testing of houses

to seek out much-needed efficiency and economy . Such an approach involves

the study of structural elements performing as parts of a building system

in order to evaluate their three-dimensional interactions.

2. 6 Summary and Conclusions

The foregoing review has covered a representative sairple of the

literature pertaining to structural testing of building components. It

38
is intended to convey the nature and scope of the information which must

be drawn from to determine the present state of knowledge and the immediate

research needs. Whereas more publications were consulted for this phase

of the study, their review has been omitted to avoid redundancy. The literature

contributing to this review spans the 26-yr period between 1937 and 1973

and therefore, traces the recent history of domestic structural testing.

Structural test methods in the United States, had their origin with

a congressionally funded research program—intended to assist the building

industry in providing adequate, lowcost housing for all who needed it.

A set of test methods was developed at the National Bureau of Standards,

in conjunction with this research program to provide a means of evaluating

the strength, stiffness, and resistance to local damage inherent in various

types of construction which were intended for use in walls, floors, partitions

and roofs in low-cost housing construction. As was reported in Building

Materials and Structures (BMS) No. 2 [49] , the scope of the test methods

provided NBS with the wherewithal to determine the structural properties

of wall specimens under compressive, transverse, concentrated, impact

and racking (i.e., lateral in-plane) loading; of specimens representing

partitions under the application of impact and concentrated loading; of

segments of floors under the application of transverse, concentrated and

impact loading; and of roof specimens under transverse and concentrated

loading. The literature implies that the principal types of construction

at the time of publication of BMS No. 2 were wood-framed and masonry construction . Variations of the two main types of construction, as well as less

widely accepted types of construction, were tested by these structural

test methods during the following decade and the results were published

in subsequent Building Materials and Structures Reports by NBS and in

reports by Forest Products Laboratory. In 1947, the ASTM Committee E6, On Performance of Building Construction , adopted the structural test

methods in virtually their original form (i.e., name, scope, format, procedure,

and content) as a Tentative Standard, E72 , Standard Methods of Conducting

Strength Tests of Panels for Building Constructions . Subsequent additions

to, and revisions of the Tentative Standard were made to reflect the changing

demands of the building industry and the updating of the state-of-theart. The E72 test methods were adopted as a Standard Method in 1954 and

underwent revisions in 1961 and 1968.

The second standard test method developed pertained to the testing

of roof truss assemblies. This standard, ASTM E73-70, "Standard Methods

of Testing Truss Assemblies," was first issued with a Tentative status

in 1948 and, after being revised in 1952, it was adopted as a Standard in

the same year.

The literature indicates that for the past 25 years structural testing

usually has been performed with the objective of evaluating the performance

of a sample of components, which were representative of some type of building

construction. Furthermore, the majority of the structural testing has

been performed in accordance with, or as a modification of ASTM Standards

E72 and E73. The further advancement of test method development and standardization has been impeded by the lack of programs whose purpose is to correlate

the results of tests of prototype buildings with those of building components.

As a result, designers, builders and evaluators are not provided with

sufficient reliable data to rationally predict the contribution to structural

resistance made by the different components that comprise houses and small

industrial build ings . The authors of BMS No. 109 [48] undertook a comprehensive

research program which resulted in the cataloging of allowable loads for

all the components tested in accordance with the recommendations of BMS

No. 2 [49] and reported on in other BMS reports. There have been no similar

programs documented since that publication was issued in 1948.

39
There have been several other notable efforts to review information

from various sources with the objective of establishing general guidelines

for structural testing. Dorey and Schriever [19] surveyed the specifications

for structural testing contained in various building codes in existence in

1955. The authors discussed generally the purpose and scope of structural

testing and then discussed in detail eleven factors to be considered in the

formulations of test specifications. Noting the lack of principles reflected

in the diversity of the then current test specifications, they attempted to

utilize the present state of knowledge to derive a method for determining the

appropriate test load magnitude. A suggested criteria to be used in evaluating

a structure's adequacy on the basis of the structural test results was also

discussed. The ad hoc committee charged by the United Kingdom Institution

of Structural Engineers [38] culminated a two-year study of code requirements

as they relate to structural testing for acceptance purposes, with several

significant general guidelines useful in development of test methods.

Cousineau [14] drew from the body of information covering 10 years of

testing diaphragms to advance some guidelines for the future testing of

diaphragms. Although this paper may have made some contribution toward

the unification of diaphragm test methods, there is still no standard

test method available. The assessment of diaphragm stiffness and strength

is quite germane to predicting the lateral stiffness and strength of buildings

subjected to lateral environmental forces. This area of deficiency is

currently being addressed by ASTM Committee E06 (see table 3.2 of Chapter 3).

As a prerequisite to determining what research was required to arrive

at a procedure for the evaluation of racking strength, Isenberg et al

[24] undertook a survey of existing information on the racking resistance

of frame wall construction. While their bibliography of 72 references

provides some background on racking tests for framed wall construction,

the authors point to the lack of basic research work supporting the development

of racking test methods. After conducting a pilot testing program to

evaluate the existing racking test procedures, the authors discuss the

additional information needed for the development of a satisfactory racking

test. The recommendations for future research, made in 1963, have not

been implemented at this writing. The advent of new materials, construction

practices and manufacturing techniques in the 10-year interim has amplified

the deficiencies cited in that report.

As the section pertaining to tests on full-scale houses (Section

2.5) indicates, there have been complete houses tested in the United States,

England, Canada and Australia for various combinations of lateral and

vertical loading. In general, the primary purpose has been to quantify

the stiffness in terms of measured deformations and the strength in terms

of the total load being applied at the time of failure or extreme deformation.

Such considerations as determining the share of the total structural resistance

contributed by the building components and the manner of load distribution

through the structure were secondary. These shortcomings notwithstanding,

there is some useful data contained in these nine reports . This data

must be augmented with that from testing additional full-scale prototypes

in the laboratory. The systematic observation of force distribution patterns

and deformation behavior of the prototype components is a necessary task

before bases for recommending improved test methods can be established.

Another area of deficiency observed from reviewing the literature

is that there is no known correlation between the results of full-scale

building tests and those of associated tests on building elements. Desirably,

one needs a kind of "transfer function" to relate the results of component

testing to the predicted behavior of complete buildings . The transfer

function (s) could make it possible to evaluate the structural attributes

of a given building on the basis of the data obtained from reliable test

methods

.

40
3.0 Present Status of Standard Structural Performance Testing

3 . 1 Activities of Domestic Associations

The development and promulgation of national standards for testing

and evaluation of building materials, elements and components is within

the purview of several voluntary standards associations. The various

technical committees, subcommittees and task groups are composed of representatives of various interests and backgrounds. The utilization of successive

ballots to obtain consensus approval for a proposed standard is the most

common approach

.

The American Society for Testing and Materials (ASTM) is the largest

and most widely recognized domestic organization involved in the development

of voluntary standards. Likewise, ASTM Committee E-6 , On Performance

of Building Construction, comprises the largest group addressing priorities

in the area of structural performance test methods for building construction.

ASTM Standard E72 , Standard Methods of Conducting Strength Tests of Panels

for Building Constructions , is the most widely used document in this country

for testing building components. To illustrate the point more graphically,

table 3.1 lists the standard structural performance tests currently used

by test practitioners. The test methods are listed as they pertain to one of three categories of building components: walls, floors, and roofs.

Most of the previously mentioned test methods were adopted as standards

on the basis of research work conducted at the National Bureau of Standards

and Forest Products Laboratory during the 1930 's. In fact, much of the

original wording in one published report, BMS No. 2 [49] was incorporated

verbatim into the Tentative E72 Standard in 1947. A review of the latest

version of the same standard, E72-68 will show that only relatively minor

revisions have been made during the subsequent 25 years.

The principal objective of the test standards - as for practically any

product-oriented standard - was the promotion of safe and economic use

of materials through the establishment of bases for comparing the performance

of building components and structural details. Of course, the conventional

construction materials and building technology were considered in the

adoption of the standards. As new developments in construction practice,

in design standards, in manufacturing processes and in materials applications

have evolved, most segments of the structural profession have acknowledged

the need for updating the testing practice as it pertains to building

components. Consequently, many of the existing standards are currently

undergoing some degree of revision. Just as significant an activity is

the development of new standard methods to satisfy heretofore unfulfilled

evaluation requirements

.

What follows immediately is a status report of current (as of December

1973) activities by ASTM Committee E-6, in the area of standard development

and revision. The report includes a mixture of proposed revisions and

new test standards. The name ( proposed name in the case of a new standard)

of the standard is cited between quotation marks, followed by a short com- mentary and a status statement of the current activities based on subcommittee

correspondence, minutes of meetings and liaison with subcommittee and

task group chairmen. Table 3.2, located at the back of this section, summarizes the current activities of ASTM Committee E-6.

41
Table 3.1 - List of standard test methods

currently (December 1973) in use

Type of

Component

Standard No. or Identifier Name of Standard Remarks

ASTM E72-68-

Section 7 Compressive Load Eccentric loading isstandard

.

ASTM E72-

Section 9 Transverse Load - Specimen Horizontal

Quarter-point loading

is standard but uniformly distributed load

may be used.

ASTM E7 2-

Section 10

Transverse Load - Specimen Vertical

Quarter-point loading is

standard but a vacuum

pressure may be used.

ASTM E72-

Section 11

Concentrated Load This test is made after

the transverse load

test (sect. 10), on the

same face of the speci- men .

WALLS ASTM E72-

Section 12

Impact Load - Specimen Horizontal

The specimen is tested

as a simple beam.

ASTM E72-

Section 13

Impact Load - Specimen VerticalThis method is intended

for constructions to

which impact loads can- not satisfactorily be

applied with the specimen

horizontal

.

ASTM E72-

Section 14

Racking Load - Complete AssembliesThis test is for measuring the racking re- sistance of "Standard"

wood frames.

ASTM E72-

Sections 15&16

Racking Load - Evaluation of Sheathing Materials on a Standard Wood FrameSect. 16 is identical

to sect. 15 except that

for the former the specimen is tested wet.

FLOORS

ASTM E72t-68-

Section 18

Transverse Load The test is performed on the upper face of the

floor in accordance with

Sections 9 & 10

.

ASTM E72 - Section 19

Concentrated Load This test is performed

in accordance with Sect.

11.

ASTM E72-

Section 20

Impact Load This test is performed

in accordance with Sect.

12 . ASTM E196-6 6 Load Tests of Floors

and Flat Roofs

Static loads are applied

for either proof testing

or ultimate load testing.

42
Table 3.1 continued - List of standard test methods

currently (Deoember 1973) in use

Type of

Component

Standard No. nr T H n "h "i "Fif^T" MiaTriA o "F R f~ Pi n c\ -=) vc\ Porn a rV c

'LOORS

American Iron & Steel Institute.

"Design of L.G.

Steel Diaphragm"

1969 Edition

Cantilever Diaphragm

Test

This test method is intended to obtain shear

strength and stiffness

data for light-gage

steel diaphragms.

ft American Iron & 3 LCCl J.HO 1—L t ULC ( 1969 Edition

Simple Beam Diarchy" ^rnn T

1 c;t" This test method has

f-I—

V-i lieo cr^TTif^ O amc nhipnf UtJ i vp J C ^— U J_ V C as the "Cantilever Diaphragm Test" but results

are more reliable for

diaphragms intended for

multibay construction.

ASTM E73-70 Testing Truss

Assemblies

This standard was originally entitled "Standard

Methods of Tpstina Heaw

Truss Assemblies".

Truss Plate

Institute TPI-70

Load Test on Full

1 ' A- t-i ^ — ±- i

' —' — i—

'

The test can be performed

on either single truss

specimens or double truss

specimens

.

ASTM E196-66 Load Tests on Floors

and Flat Roofs

Static loads are applied

for either proof testing

or ultimate load testing

w

ft

ASTM E72-68-

Section 22

Transverse Load The test is performed in

accordance with Sect. 9.

ROO ASTM E72-68-

Section 23

Concentrated Load This test is made after

the transverse load test

(Sect. 22) on the same

face of the specimen, in

accordance with Sect. 11.

Appendix B of

Z\mPT"i P^n "i on — ^XlllC J- 1W CJH J-N C*, 1 LUJi al Standard

A119.1, 1972

Test Procedure for

Rnnf Raftprq or Roof

Trusses

These test recommendaf i nrm ^tp c^"im'ilr3T tn

those in the Test Method

by Truss Plate Institute.

American Iron & Steel Institute.

1969 Edition.

Cantilever Diaphragm

Test

See Remarks stated for

"Floors" above.

American Iron & Steel Institute.

1969 Edition.

Simple Beam Diaphragm

Test

See remarks stated for

"Floors" above.

43
Table 3.2 - Summary of standards currently under development

or revision hu ASTM Cr mmittee E-6*

BUILDING COMPONENT

NAME OF STANDARD TYPE OF LOADING COMMENTARY STATUS

WALL

SHEATHING Evaluation of Materials on a Standard Wood

Frame (R) ASTM E72-68

Static? ShortTerm; Racking; Concentrated

Method intended to determine the relative

shear stiffness and strength of various sheathinq materials.

Grading specifications

of frame lumber being

revised. Task group assigned to draft a new standard method.

WALLS OR

WALL SEGMENTS

Test for Flexural Strength of Walls

(R) ASTM E72-68

Static; ShortTa v'tii • Pi P»Y11r*A 1

* Uniform or Concentrated

Method intended to determine the flexural stiffness and strength

of walls or wall segments under simulated wind force. To be a replacement for Sections 9 and 10 of ASTM

E72-68

.

A revised draft is expected prior to the June 1974 meeting.

Adoption of the test method as a standard by ASTM, is projected for 1974 .

SHEAR WALLS AND PARTITIONS

Test for Framed Shear Walls and Partitions for Buildings (N)

Term; Racking

Proposed method represents a modification

of the proposed "Standard Method of Test

for Framed Floor or

Roof Diaphragm Con- structed for Buildings".

CSee ASTM E196 below)

.

Task Group is studying

first draft for possible

improvements . Subcom- mittee E06 . 12 is also reviewing the first

draft.

BEAMS AND

GIRDERS Flexural Tests

on Beams and Girders for Building Construction (N)

Static; ShortTerm; Flexural

;

Uniform

Method intended primarily for construction whose predicted

behavior does not con- form to the assumptions

used in flexural analysis .

Has been approved by Committee E06 and its adoption by ASTM as a standard is iminent.

pinnnc awn ROOFS Load Tests of Floors and Flat

Roofs (R) ASTM E196-66

Static; ShortTerm; Flexural; Uniform

Procedures can be used

for either proof testing or ultimate load testing of horizontal

components . This method is often referred to

in model codes, (e.g. ACI 318-71)

A revised draft of the standard is forthcoming

from the assigned task group

.

ROOFS Tests for Framed

Floor or Roof Diaphragm Construction of Buildings (N)

Static ShortTerm; In-Plane Flexural or In- Plane Shear; Concentrated

Method involves use of either cantilever

frame or simple span

frame to determine the response of diaphragms

to in-plane concentrated loads. Based on

test method by A. I. S.I.

Task group is preparing

a new draft for simultaneous review by Subcommittee E06.ll and Committee E06 prior to June 1974.

ROOF TRUSSES Methods of Testing Truss Assemblies (R) ASTM E73-70

Static; ShortTerm; Flexural; ConcentratedProcedures are intended for testing single

truss specimens; loading may be applied

either at the panel

points or between the panel points.

Currently under task group study. Has been subject of significant criticism in a recent preliminary report.

A draft of revised standard to be presented at the June 1974 meeting. EXISTING

BUILDING AND

FULL-SCALE

PROTOTYPES

Recommended

Practice for Load Tests on Existing Buildings and FullScale Prototypes

(N)

Static or

Dynamic; ShortTerm; Flexural;

Shear; Impact; Uniform or Concentrated

The sixth draft of the proposed Re- commended Practice encountered many difficulties and conflicting requirements

The Task Group concluded that rather

a "guide" should be undertaken jointly by ASCE S ASTM.

A joint committee has beer appointed. A committee

report is to be presented

TRUSS CONNECTORS Test for Tensile Strength Properties of Steel Truss Plates (N)

Static; ShortTerm; Tensile; ConcentratedMethod intended to ev- aluate the tensile strength of steel truss plates used to fasten wood members together.

The sixth draft has been balloted among

the entire membership

of Committee E0 6 . Proposed method should be- come a standard in near future

.

(R) -Existing Standard Being Revised

(N) -New Standard Being Proposed. *As of December 1973.

44
"Standard Method of Test for Framed Floor or Roof Diaphragm Construction

for Buildings"

Commentary : This proposed standard test method is intended to have general applicability to framed diaphragm assemblies representative of floor and roof construction

used in buildings. The proposed standard describes two alternative test

methods

:

(1) uses a cantilever test frame and

(2) uses a simple span frame with third-point loading.

The test setup, loading procedure, spatial details and associated calculations

are all based on test methods described by the American Iron and Steel

Institute in the publication, "Design of Light Gage Steel Diaphragms" (1969

edition) . By recording the deflection of discrete points within the diaphragm

for successive levels of static loading to failure, it is possible to

determine the ultimate shear strength and the in-plane shear stiffness

of the test assembly.

Status : The task group for this proposed standard test method prepared a new draft and circulated it to the subcommittee concerned with the performance

of horizontal components and to Committee E-6 prior to the June 1974 meeting.

"Standard Method for Load Tests of Floors and Flat Roofs"

Commentary : This standard (ASTM E196-66) was originally issued by Committee E6 in 1962 and was subsequently revised in 1966. This method provides

for the evaluation of floor or flat roof assemblages (slope of less than

1 in 12) for strength and stiffness characteristics, under actual or simulated service conditions. The procedure involves the measurement of

deflections at key locations as the test component is subjected to successive

increments of superimposed static load. This standard, or some variation

of it, is often referred to in model codes as a method for proof testing

or ultimate load testing.

Status : A revised draft of the standard is forthcoming from the task group

assigned to make recommendations.

"Racking Load - Evaluation of Sheathing Materials on a Standard Wood Frame"

ASTM E72 Sections 15 and 16.

Commentary : The results of this test method provide a measure of the racking

resistance of wall panels composed of a standard frame covered with any

specified sheathing material. The standard frame being a test constant,

it is possible to assess the relative racking resistance contribution

of the various sheathing materials. Section 15 of E72 describes the procedure

for testing specimens with a moisture content ranging between 12 and 15

percent + 3 percent. Section 16 of E72 cites an identical procedure

but the specimen must undergo simulated environmental conditioning prior

45
to testing. The prescribed conditioning involves two successive cycles

of spraying the sides of the specimen with water and allowing it to dry

in laboratory air, preferably at a temperature of 75°+5°F. Then a third

cycle of wetting is performed. The panel is to be tested in racking no more than two hours after the third wetting stage. The test method described

in these two sections is designated in the requirements of FHA Technical

Circular 12 [41] as the physical means by which the performance of various

sheathing materials can be compared with that of a "standard" sheathing.

Status ; These two sections, along with the other 21 sections of E72 were

last accepted in September 1968. The original version was issued in 1947.

The membership of Committee E-6 is currently voting on a revision which

changes the specification for the lumber constituting the standard frame.

Furthermore, a task group has been assigned to draft a revised standard

method which will reflect the present state of knowledge.

"Standard Methods of Test for Flexural Strength of Walls"

Commentary : This is a proposed revision intended to replace the existing standards

found in Sections 9 and 10 of ASTM E72-68. The intent of these flexural

test methods is to determine the strength and stiffness characteristics

of walls or wall segments as they are influenced by a static-load simulation

of perpendicular design wind forces. Either proof-load testing or ultimateload testing can be accomplished by following the prescribed incremental

force-application and deflection-measuring procedure.

Status ; Substantive comments were made at the December meeting as to improvements that could be made in a draft sent to the subcommittee concerned with

performance components prior to that meeting. Also, the subcommittee

concerned with the performance of vertical components discussed the pros and

cons of adopting a standard method for testing for the strength of curtain

walls (ASTM E330-73) , which was prepared by another subcommittee (E06.51) as the method for testing for the flexural strength of walls. The task

group was charged with determining the feasibility of making such an adoption. The task group's recommendations are to be presented in the form of

another draft of a proposed revision to the standard method in ASTM E72.

"Method of Test for Diagonal Tension (Shear) in Masonry Assemblages"

Commentary : The proposed standard consists of a procedure for determining the

shear resistance of 4-ft by 4-ft masonry specimens which are loaded in

diagonal compression, normal to the mortar bed joints. The applicability

of the test method is supported by considerable test experience; it has

been used by the Structural Clay Products Institute (now Brick Institute

of America) for several years and it is referred to in Section 4-3 (Allowable

Stresses in Non-Reinforced Brick Masonry) of the Second Edition of their

publication Recommended Practice for Engineered Brick Masonry . This method

has also been employed by C.B. Monk at Purdue University, John Blume

and Associates Co. , and the National Bureau of Standards. The size of

the specimen, as compared to the 8 -ft by 8 -ft dimension designated in

the ASTM E72 racking test, is an important parameter in that it permits

46
the use of a type of testing machine that is common to many laboratories.

Furthermore, by using smaller scale specimens, four samples can be produced

for about the same effort as one 8-ft by 8-ft sample. In the opinion

of the task group, the recommended size is the smallest that would be

representative of a full size masonry assembly.

Status :

The proposed standard method has been approved by the subcommittee con- cerned with the performance of vertical structures and Committee E-6 . It

will subsequently be sent to the society (ASTM) for final approval before

publication

.

"Standard Method of Test for Framed Shear Walls and Partitions for Buildings"

Commentary : This method was proposed by some of the technical staff of the American

Plywood Association as a generalized racking test for wall construction.

The first draft indicates that the test method has been derived by modifying

the procedure for the cantilever frame setup described in the proposed

"Standard Method of Test for Framed Floor or Roof Diaphragms for Buildings."

The task group assigned to prepare additional drafts will be studying

the proposed standard to evaluate its applicability to different types

of construction and different geometric configurations.

Status :

The development of this standard is in its preliminary stages. The

first draft has been circulated to members of the subcommittee on performance

of vertical components, for their review and comments.

"Standard Methods of Testing Truss Assemblies"

Commentary : The general recommendations in this standard are applicable to either

proof load or ultimate load tests of single-truss specimens. The original

version of this standard, then entitled "Standard Methods of Testing Heavy

Truss Assemblies," was issued in 1948 with a Tentative status. A revised

version was approved in 1952 and adopted as a Standard in the same year.

The emphasis of the test method was on "heavy" assemblies with purlins

or concentrated panel point loading or both. The current edition, ASTM E73-

70, contains the same recommendations as the 1952 edition, except that

a procedure has been added for loading the top chord of the truss —while

it is in the in-service position —between the panel points.

Status : A task group has been studying this standard for areas of possible

revision. It is the preliminary finding of the task group that: the existing

standard test method fails to include all applicable loading techniques

(e.g. vacuum loading) ; there is the implication that other loading techniques

are not adequate, although there is no stated justification for this implication;

there is a lack of safeguard against the possible use of test gimmicks

intended to produce more favorable test results; and the method as it

presently exists is inapplicable to testing light trusses. It was recommended

that the test standard have its status changed to a Standard Recommended

Practice. The task group will continue to study this test area and then

47
begin preparation of a draft of a revised test method. The proposed revisions

will be presented at the June 1974 committee meeting.

"Recommended Practice for Load Tests on Existing Buildings and Full-Scale

Prototypes"

Commentary : The planning and execution of load tests on existing buildings or on full-scale prototypes is presently handled on an ad hoc basis, since

no standard procedures have been adopted. The absence of a standard

methodology in this area constitutes a significant deficiency in that

there is substantial rationale for executing tests on full-scale assemblies.

The results of full-scale testing can be applied during the design and

analysis stage as well as during the evaluation stage. Despite the apparent

merits of promulgating recommended practices to be employed when testing

full-scale structures, the task group has concluded that the significance

of professional judgement in the planning and execution stages is too

great to render the process to generalized procedures. It was noted that

the sixth draft of the proposed Recommended Practice encountered many

difficulties and conflicting requirements. The task group recommended

that a "guide" for engineers be prepared by a joint ASTM-ASCE Committee.

Status : A joint committee has been appointed and a report of the proceedings

of a committee meeting will be presented at the June 1974 E-6 committee

meeting.

"Standard Methods of Flexural Tests on Beams and Girders for Building

Construction"

Commentary : The scope of this proposal is stated as follows: "These methods

provide for the flexural testing of beams and girders under simulated

service conditions to determine their structural performance characteristics

.

In some cases, they are also suitable for determining the structural performance

adequacy of the design, materials, connections, and fabrication techniques.

They are intended primarily for construction that may not conform with

the relatively simple assumptions upon which well known flexural theories

are based. The methods are not intended for use in routine quality control

tests."

Status : At the June 1973 meeting the Subcommittee on Horizontal Building

Construction (E06.ll) unanimously agreed that this proposed standard test

method be recommended to the main committee for submittal to ASTM members

for ballot as a Standard.

"Standard Method of Test for Tensile Strength Properties of Steel Truss

Plates"

Commentary : This proposed standard addresses the need for a method of evaluating

the tensile strength of steel truss plates used to fasten wood members

together. The method calls for testing the steel truss plates, testing

control plates of the same material as the truss plate and then comparing

48
the performance of the two types of specimens.

Status : The sixth draft is presently being balloted by the full E-6 Committee.

"Standard Method of Test for Flexural Bond Strength of Masonry"

Commentary : The two methods comprising this proposed standard are intended for

the determination of flexural bond strength of masonry assemblages. Through

the application of these procedures, the bond strength of prisms composed

of different types of masonry units and mortar can be compared. Also,

the relative quality of workmanship during construction can be determined.

Status : This proposed standard method has been approved by Committee E-6 and

hence must be sent to the society for total ASTM membership approval, prior

to being published.

3 . 2 Activities and Publications of Foreign and International Associations . 3.2.1 Foreign Standards Associations

A search has been conducted through the index of standards published

by several foreign standards associations and by one international association

to determine if there are references to existing standard test methods

which may be consulted in attempting to improve domestic test practice.

In this effort, the standards index of the following standards associations

have been consulted: Standards Association of Austrialia, Canadian Standards

Association, British Standards Institution, German Standards Institution

(DNA) , The Standards Institution of Israel, Japanese Standards Association,

and International Organization for Standardization (ISO) . The standards

pertaining to the structural performance of building construction, as developed by these associations ,. generally provide design data and include

recommended design and construction practice similar to that in the American

Concrete Institute's Standard 318-71 [2].

Contained in the standards published by all the previously mentioned

associations except one, are some general guidelines for planning and

executing test programs, but no standardized test procedures applicable to

evaluating building components. The Japanese Standards Association has

issued standard test methods, similar in format and scope to ASTM Standard

E72, for testing building components. English versions of two typical

Japanese standard test methods have been prepared and reviewed for this

report (refer to Appendix C) . Their titles (see reference [39]) are:

(1) "Test Method for Bending Resistance to Local Concentrated Load" and

(2) "Test Method of Loading Resistance for Loading Normal to Surface."

The procedure recommended in these standards for rating the performance

of test specimens seems to be an improvement over the strictly subjective

approach to interpreting test results that is necessary when using most

domestic standards. The Japanese standards include a 10-point rating

scale from which one can obtain a basis of comparison for the performance

of two or more types of construction.

49
3.2.2 International Associations

Although there are several international associations (i.e. CIB and RILEM)

whose main functions are to serve as a medium of exchange of technical

ideas, research experiences and expert opinion, and to promote development

of standards, there is only one organization (i.e. ISO) authorized to

promulgate international standards. The work of that organization and

two other international associations will be discussed briefly. Special

attention has been given to those collective committees, symposia (or

similar gatherings) and publications that may be relevant to structural

performance testing and the associated conditioning of test specimens

.

3.2.2.1 The International Organization for Standardization

The International Organization for Standardization (ISO) is a federation

of the national standards institutes of 73 countries from all parts of

the world. As a means to promoting international cooperation in the development

of standards and in the exchange of scientific, technological and economic

information the ISO may: (a) set up international standards; (b) encourage

and facilitate the development of new standards having common requirements

for use in the national or international spheres; and (c) cooperate with

other international organizations interested in related matters, particularly

by undertaking, at their request, studies relating to standardization

projects. The work of developing International Standards is carried out

through technical committees. There are 146 technical committees, which

are subdivided into various subcommittees and working groups . Prior to

January 1, 1972, the ISO published ISO Recommendations as a result of

the work of the technical committees , subcommittees and working groups.

Since that time what have been issued are called International Standards . A close scrutiny of the list of technical committees and the scope

of their activities produced the identification of one committee of particular

interest. The committee on Enclosures and Conditions for Testing , TC

125, seeks to develop ISO standards in relation to conditioning environments

for test and/or test environments for materials and equipment for any

application. It is also concerned with the requirements for enclosures

in which these environments are obtained and maintained.

3.2.2.2 The Union of Testing and Research Laboratories for Materials and

Structures

The Union of Testing and Research Laboratories for Materials & Structures

(RILEM) is an international, non-profit association governed by Swiss

law. The two main functions of this organization are to serve as a medium

of exchange of ideas, information and experience with respect to the study

of building materials and building elements and to act as a catalyst in

the improvement and unification of testing methods.

Through the issuance of publications, the distribution of surveys

and the organization of symposia the association promotes international

dissemination of information and discussion of developments and experiences.

The second function is performed through the establishment of technical

committees, the members of which are selected on the basis of their interest

and expertise in the particular field of study. The respective committees

then engage in activities appropriate to the production of recommendations

for international standards. The recommendations are eventually transmitted

to ISO which is the only organization authorized to promulgate international

standards. There are 25 standing technical committees at the present

time

.

50
There are four technical committees whose stated scopes and objectives

indicate that their activities may be of interest to the study of current

practice of test methods conducted on walls, floors, and roofs. Those

names are listed below and referenced according to the symbols assigned

by RILEM.

1) 3-TT Testing Methods of Timber (established in 1967)

,

2) 20-TBS Testing Building Structures in Situ (established in 1970)

,

3) 21-IL The Effect of Impact Loading on Buildings (established

in 1970) and

4) 24-BW Methods of Testing the Mechanical Properties of Load Bearing

Walls and Masonry . RILEM has organized about 35 international symposia since 1954 and

the full proceedings have been published. Several of the symposia topics

warranted a thorough search of the publications for pertinent information.

The lists of proceedings reviewed are as follows: (1) "Effects of Repeated

Loading of Materials and Structural Elements," Mexico, 1966, (2) "Testing

Methodology and Technique of Full -Scale and Model Structures, under Static

and Dynamic Loads," Bucarest, 1969, (3) "Testing and Design Methods of

Lightweight Aggregate Concretes, Budapest 1967, and (4) "Performance Concepts

in Buildings," United States, 1972.

3.2.2.3 The International Council of Building Research, Studies and Documentation

The International Council of Building Research, Studies and Documentation

(CIB) is an organization comprised of representatives of large public

building research organizations and large industrial bodies or departments

involved in building research. The scope of the organization's concern

ranges from the study of various aspects of construction to consideration

of the social aspects of the total built-up environment. The encouragement

of international collaboration between all types of research bodies and

the promotion of exchange of comprehensive research reports are two principal

functions undertaken by CIB. To this end, CIB has currently adopted several

working methods

:

1. Public congresses on themes of general interest are held every three years. There have been five

congresses convened since the organization was established in 1953, with the first one being held

in 1959.

2. A General Assembly attended by members and specially

invited guests is held at least in three-year

intervals to discuss selected topics.

3. The organization of symposia and colloquia is undertaken on different scales depending on the interest in a special theme. These sessions are sometimes jointly

organized with other associations such as RILEM and

ASTM.

In order to effect international research and study projects, working

commissions, made up of experts from different national institutes, are organized. (The delegation of research duties to committees, subcommittees,

etc., is common to all three international associations, ISO, RILEM and

CIB.) The results of the research work or study project are published

51
by the working commission and distributed to the membership. CIB also

publishes an international periodical, BUILD International, that attempts

to inform the practitioners of research results as to the latest findings,

recommendations and trends.

Of the 30 listed CIB Working Commissions there are 4 whose programs

of work have at least a remote connection with test method development.

Those relevant working commissions are listed below, according to number

and name, along with a condensed version of their respective purposes.

W18 Timber Structures - Improvement of structural uses,

jointing, testing and stress grading

of timber; comparison and unification

of national timber design codes

.

W23 Basic Structural Engineering Requirements - Development of

recommendations on standarized

calculation methods of structures

.

W23A - Safety of Load Bearing Walls - Development of scientific

bases for building codes, particularly

related to calculations and testing of

stresses in load-bearing walls.

S56 - Lightweight Lowrise Construction - Symposia on various

aspects of lightweight constructions,

e.g., technical trends and solutions.

None of the 10 CIB reports published addresses the subject of structural

test method development of walls, floors or roofs. Likewise, a search

of the proceedings of CIB congresses and of CIB symposia did not produce

any significant sources of information. Presently, Working Commission

W23A, with RILEM Technical Committee 21-IL The Effect of Impact Loading

on Buildings, is conducting an international survey among research institutions

as a means of finding out what research is currently underway or has been

completed relating to load-bearing walls. The National Bureau of Standards

has a United States National Committee Corresponding Membership on CIB

W23A. The findings of the survey will be distributed at some future date.

4.0 Review of Operation BREAKTHROUGH Structural

Testing Performed at the National Bureau of Standards

4 . 1 Introduction

4.1.1 Purpose and Scope

In this chapter the test methods employed by the National Bureau

of Standards (NBS) during the evaluation of industrialized building components,

for the Operation BREAKTHROUGH housing program, are compared to the methods

contained in ASTM Standard E-72-68[5]. This comparison is done for the

purpose of contributing to the evaluation of improved standard methods

that may be effectively used in the evaluation testing of innovative housing

systems

.

The comparison of test methods is confined to a critical review of

the deviations from, and extensions to, the adopted standard test methods.

It was not felt necessary to describe the standard test methods to fulfill

the stated purpose. Furthermore, it is not within the scope of this chapter

to address the overall effectiveness of the respective standard methods

referred to in the comparisons.

52
Also, tests on housing systems are summarized and reviewed for the

purpose of making recommendations toward the development of standard

test methodology for full-scale housing units.

A separate section of this chapter is devoted to each of the three

groups of tests: roof and floor; wall; and full scale systems. Included

in the section covering each group of tests is a summary of the test, a review and recommendations for improving the test, based on NBS experience

with the BREAKTHROUGH testing.

4.1.2 Objectives of the Operation BREAKTHROUGH Testing Program

Innovative uses of materials and methods of fabrication and construction

were features of housing systems proposed by several Housing Systems Producers

(HSP's) for the HUD-sponsored housing program. Where the evaluation of

such features could not be accomplished by rational analysis, it had to

be supported by structural tests (as well as fire and acoustic tests) of

critical components. Thus, the knowledge gained about the structural

behavior of the specimens was to be applied in the evaluation of housing

systems for structural safety and serviceability. Also included were panels

representative of certain conventional constructions for which engineering

data was either non-existent or inadequate for the performance of an effective

evaluation.

In general, physical simulation was used to represent the support

and loading conditions for the building components so that the test results

could be used directly in the evaluation process. For the cases where

direct evaluation through testing was not feasible or necessary, the testing

provided structural data such as material strength, elastic modulus and

component stiffness, any one of which an evaluator may need to perform

an analysis.

4.1.3 Scope of Operation BREAKTHROUGH Structural Testing

The types of wall, floor and roof panels and systems tested, and

the nature of the tests conducted at NBS for the Operation BREAKTHROUGH

program are listed below.

1. Floor and Roof Tests

a. Impact and subsequent concentrated static loading on plywood subflooring supported by wood joists 125]

b. Local resistance of conventional plywood subflooring

to concentrated load [52]

c. Static uniform load on sandwich panels with

gypsum board facings [22]

d. Static uniform load on panels fabricated from

glass fiber-reinforced polyester laminate [37]

e. Static uniform load on steel-faced sandwich panels [33]

2. Wall Tests

a. Compressive loading on sandwich panels with gypsum

board facings [22]

53
b. Racking load on panels fabricated from glass

fiber reinforced polyester laminate [37]

c. Compressive loading on panels fabricated from

glass fiber reinforced polyester laminate [37]

3. Full-Scale System Tests

a. Two story house subjected to lateral load [53]

b. A wood framed housing module [51]

Table 4.1.1 relates types of construction and tests conducted at NBS by

indicating which of the seven representative reports contain certain topics.

4 . 2 Floor and Roof Tests

4.2.1 Impact and Subsequent Concentrated Static Loading on Plywood Subflooring Supported by Wood Joists [25]

4.2.1.1 Summary of Tests

A series of tests was made on floor specimens to establish a relationship

between an impact load and the subsequent deflection of the impacted area,

as it was subjected to a concentrated static load. The impact was first

delivered to the floor specimen (see figure 4.2.1) by dropping a 60-lb

bag from a given height as shown in figure 4.2.2; then a 400-lb concentrated

load was applied in the manner depicted in figure 4.2.3. The latter load

was applied through the end of a 5/8-in round steel rod to simulate large

magnitude concentrated loads that may be transmitted through a caster

of a crowded couch, or a piano caster. A description of the test specimens

is presented in table 4.2.

4.2.1.2 Review of Tests

The setup and procedures employed in this test were similar to those

recommended in ASTM E72 for impact and concentrated loading. However,

the diameter of the loading rod used, was 5/8 in instead of the 1 in specified

in ASTM E72 because it was concluded to be closer to reality (e.g. simulation

of a couch leg) . The use of the smaller rod will be discussed in Section

4.2.2.

Using curves such as those shown in figure 4.2.4, a limiting level

of impact energy could be determined for a specific floor system provided

that an acceptable deflection limit under the 400-lb concentrated load, was established. At present, no such limit is found in the design specifications

and standards used in the United States. Based on results of tests conducted

on 1/2-in plywood subfloors with wood joists spaced at 16 inches o.c,

the Canadian Standards Association Standard- CSA0152-1964 , "Performance of

Construction Plywood", has a requirement for a maximum deflection limit

for plywood subfloors. The deflection limit is 1/180 of the span between

joists under a static concentrated load of 175 lb.

4.2.1.3 Recommendations

There exists a basic impediment to the development of an improved

test method involving impact and concentrated loadings in that acceptable

limits of localized deflection have not been determined through research.

Such limits must be based on the various levels of perceptible discomfort

54
55
Table 4.1.2 - Operation BREAKTHROUGH structural test

reports referenced in table 4.1.1

(WJ) "The Effect of Impact Loadings on the Performance of Wood Joist

Subflooring Systems", PB-221-188 [25]

by H. S. Lew

(LY) "Study of the Local Resistance of Conventional Plywood Subflooring

to Concentrated Load" PB-220-432 [52]

by F. Y. Yokel

(MO) "Structural Tests of a Wood Framed Housing Module" COM-73-10860 [51]

by C. W. Yancey and N. F. Somes

(FH) "Full Scale Test on a Two-Story House Subjected to Lateral Load"

BSS 44 [53]

by F. Y. Yokel et al

.

(ST) "Structural Evaluation of Steel Faced Sandwich Panels" PB-213-240 [33]

by J. H. Pielert et al.

(GY) "Structural Tests for a Housing System Using Sandwich Panels with

Gypsum Board Surfacings", PB-214-336 [22]

by W. E. Greene et al

.

(PO) "Structural Tests on Housing Components of Glass Fiber Reinforced

Polyester Laminate" PB-221-183 [37]

by T. W. Reichard et al.

56
Table 4.2 - Description of test specimen.

Group Component of Specimens No. of Tests

1 1/2 in. A-D INT, Group 1* 56

2 5/8 in. Under layment C-C

Plugged

44

3

a 1/2 in. C-D Plugged INT with

1/4 in. A-A Under layment

25

b

+ 1/2 in C-B PliiPPed INT with

1/4 in. A-A Underlayment

28

a 1/2 in. C-D Plugged INT with

1/4 in. Hardboard Underlayment

36

4 b

+ 1/2 in. C-D Plugged INT Split

with 1/4 in. Hardboard Underlayment .

28

These specimens had split sheets of plywood panel

thus providing discontinuous edge at the center of

test panel.

For designation of plywood, refer to latest edition

of U. S. Product Standard PS 1-66 for Softwood Plywood-Construction and Industrial, Product Standards

Section, National Bureau of Standards, U. S. Department of Commerce.

/2-in A-D INT (GROUP I) 5/8-in UNDERLAYMENT C-C(6R0UP2)

l/2-in C-D PLUGGED (GROUP 3 8 4)

|/4-in PLYWOOD A-A UNDERLAYMENT ( GROUP 3o a 3b ) l/4-in HARDBOARD UNDERLAYMENT (GROUP 4a ft 4b)

Figure 4.2.1 - Test specimen.

57
Figure 4.2.2 - Impact test setup.

Figure 4.2.3 - Concentrated load test setup.

58
59
experienced by a person walking over, or standing on, a localized area that

has been subjected to impact loading. It is recommended that once deflection

limits are established, a development program be conducted with the objective

of deriving a test method that evaluates the response of the floor for

its acceptability to human perception.

A recommendation regarding the area of the rod best suited to apply

a concentrated load on a floor specimen will be expressed in the next section.

4.2.2 Local Resistance of Typical Plywood Subflooring to. Concentrated Load [52]

4.2.2.1 Summary of Test

Five typical plywood subflooring assemblies, constructed in accordance

with the requirements of the November 19 66 edition of the FHA Minimum

Property Standards , were tested under concentrated loading in order to

compare their performance with performance criteria which had been developed

on the basis of available data on anticipated occupancy loads. The test

specimens were separated into two major groups, those with underlayment

and those without underlayment (figures 4.2.5 and 4.2.6). Table 4.3

indicates the other test variables and the scope of the testing program. A

typical test setup is shown in figure 4.2.7.

4.2.2.2 Review of Test

Concentrated loads on floors may be caused by heavy furniture or by human activity. Two possible critical conditions are identified and

they are as follows:

1. A concentrated load of critical magnitude may cause damage to the entire floor or, as is more likely, to

a portion of the floor, by exerting excessive bending

moments and/or excessive shear forces.

2. A load may be concentrated over a very small area,

therefore causing failure by excessive compressive stress

and/or excessive punching shear . , -Typical heavy concentrated

loads have been studied by Boyd — and are summarized

below:

1. A person carrying a heavy load 350-450 lb

2. A crowded sofa (per front caster) 300-350 lb

3. An upright piano (1 caster) 200 lb

4. A grand piano (1 caster) 280 lb

5. Transportation of an upright piano (per wheel) . . .250-350 lb

6. Transportation of a grand piano (per wheel). 2 . . .250-450 lb

Boyd concluded that since the presence of grand pianos in residences

is relatively rare, the following design loads should be used:

(a) 400 lb for several seconds

(b) 350 lb for 1/2 hour

(c) 200 lb idefinitely. —^See the report by Boyd, J. D . , "Minimum Strength and Stiffness Necessary

for Wooden Floors and Houses", Paper No. 34, CSIRO, Division of Forest

Product Technology, Melbourne, Australia, 1964.

60
Figure 4.2.5 - Standard specimen without underlayment.

Figure 4.2.6 - Standard specimen with underlayment.

UNDERLAYMENT —1/2" PLYWOOD
Table 4.3 - Number of tests performed.

Joist Spacing, in 16 24 20 10 6

Dian

Loadec eter of area, in 1 5/8 1/2 1 5/8 1 5/8 1 5/8 1 5/8 TOTAL

item

A

B

12 18

18

6

12

6 6

6

6 6

11

e 6

6

72

53

>. C 5 6 2 13

Subf

looring D

E

F

G

14

14

7

7

6

7

21

2 1

6

7

Total No. of Tests 193

SUBFLOORING SYSTEMS:

A: 15/32-in-thick underpayment grade Southern Pine interior-type, - 5-ply

plywood.

B: 1/2-in-thick standard grade Southern Pine interior-type with exterior

glue, 5-ply plywood.

C: 1/2-in-thick C-D grade Dourlas Fir interior-type, 3-ply plywood.

D: 1/2-in-thick standard grade Douglas Fir interior-type, 3-ply— plywood

under 7/32-in-thick hardboard underlayment

.

E: 1/2-in-thick plywood as in D under 1/4-in-thick plywood underlayment.

F-. 1/2-in-thick plyood as in C under 7/32-in-thick hardboard underlayment.

G: 1/2-in-thick plywood as in C under 1/4-in-thick plywood underlayment.

—^The core of this plywood was laminated giving the interior ply double

thickness

.

Figure 4.2.7 - Test setup.

62
Critical loading caused by load concentration over a small bearing

area is also caused by stilletto heels. Even though these heels are not

currently fashionable, their future use cannot be ruled out. A study

of typical stilletto-heel pressure!/ indicates a range of compressive

stresses from 550 psi to 1390 psi, and one extreme value of 2260 psi.

Values of punching shear computed from these data range from 80 lb/in

to 117 lb/in. The case that produced the 2260-psi compressive stress

produced a punching shear of 156 lb/in.

The concentrated load test described in Section 19 of ASTM E72-68[5]

is intended to measure the structural capacity of the system, and the

ASTM D2394 Test—' measures the strength of the finished flooring. These

tests, with proper choice of load levels, could adequately evaluate most

floor systems. A problem arises, however, with floor systems that consist

of a thin structural skin supported by stiffening elements. In this case,

the system may perform satisfactorily under the ASTM D2394 test, while

under different support conditions the structural skin may fail by punching

shear. On the other hand, in order to generate adequate stress under

a 1-in diameter disc, the concentrated load would have to be increased

to over 1000 lb, and in order to generate adequate punching shear the

load would have to be increased to at least 500 lb. These heavier concentrated

loads would be higher than the extreme concentrated loads that act on the floor in service.

The compressive stress caused by the 400-lb load, applied over a 5/8-

in diameter circular area, is 1360 psi and the punching shear is 203 lb/in.

Comparing the concentrated load, the compressive stress and the punching

shear values with the concentrated loads data presented above for stiletto

heels, it is evident that the effect of a 5/8-in diameter circular area more closely approximates these data than that of a 1-in diameter circular

area

.

4.2.2.3 Recommendation

In view of the above comparison, it is recommended that the standard

ASTM E72 test be modified to reflect the findings of this test [52] . Hence,

the standard would specify a 5/8-in diameter rod to apply the concentrated

load

.

4.2.3 Short Term Flexure Tests

4.2.3.1 Summary of Tests

A. Static Uniform Load on Sandwich Panels with Gypsum

Board Facings [22]

One roof and one floor panel were tested, in a dry state with temperature

and relative humidity conditions of approximately 73°F and 50% respectively.

Figures 4.2.8 and 4.2.9 show the test setup and the details of the specimens.

A complete load-versus-def lection plot could not be recorded because of

the large deflections encountered and the need to protect the equipment

from damage

.

The results of these tests cannot be compared directly to generalized

code requirements because of design changes which resulted in the roof — Thornburn, H. T. "Flooring Damage by Heels," Materials Research Standards,

ASTM, Vol. 2, No. 9, Phila., Pa., Sept. 1962.

^STM D2395-69 "Tests for Simulated Service Testing of Wood and Wood-Base

Finish Flooring", American Society for Testing and Materials.

63
REACTION BEAM

2-LVDTs

GAP

(BOTH ENDS)

AIR BAGS

SECT A-A

7-5/16

DETAIL

A 5/8 GYPSUM BOARD

B FRP LAMINATE

C PAPER HONEYCOMB

D SAME AS "b"

E ROOF-5/8" GYPSUM BOARD

FLOOR 5/8" PLYWOOD

Figure 4.2.8 - Schematic of short term flexural test setup for safety

and serviceability testing.

64
65
and floor components becoming flat plates, supported on all four edges.

The specimens tested were elements which acted primarily as beams supported

only on two opposite sides. However, the beam stiffnesses were determined

from the load-versus-def lection plot by using the elementary beam deflection

equation for the case of uniform loading.

From this, an estimate of the structural rigidities of the roof and

floor plates were made. For the roof, the derived structural rigidity

was used to calculate a maximum deflection for a uniform load of 20 psf.

This afforded a comparison of the computed deflection-to-span ratio with

the value allowed by the governing performance criterion.

The test results were also applied indirectly to determine a suitable

limit for the design ultimate uniform load for the roof plate. In the

test specimen, failure occurred in the compression facing, so that the

strength was limited by bending. It was assumed that the strength of the

roof plate would also be limited by bending and that the ultimate bending

moment of the plate would equal the ultimate bending moment derived from

the simple beam test performed. Substituting the test results into the

equation for the maximum plate bending moment, and solving for an equivalent

uniform load, yielded a load capacity for the roof. Based on this value,

an allowable design ultimate loading for the roof was determined.

The floor was also a flat plate with the same dimensions and aspect

ratio as the roof. Using the same analytical process as that applied

to calculate the roof deflection, a maximum deflection was calculated

for a design uniform floor load of 40 psf. As with the roof plate, this

afforded a comparison of the computed deflection-to-span ratio with the

value allowed by the governing performance criterion.

The same analytical procedures used in determining the load capacity

of the roof were used to determine the load capacity of the floor. This

value was used to establish an allowable design ultimate load.

B. Static Uniform Load on Panels Fabricated from Glass

Fiber Reinforced Polyester (FRP) Laminate [37]

One roof panel was tested in a dry state with environmental conditions

of approximately 75 °F and 50% relative humidity. Figure 4.2.10 shows

the test setup, dimensions and details of the cross section of the panel.

The midpoint deflections measured during this test afforded a direct comparison

of the deflection-to-span ratio with that permitted by the governing performance

criterion since the physical simulation of the supports and loading were representative of actual conditions. The roof panel did not reach its

flexural capacity because the air bag failed first. However, at this

point, the load on the roof panel had exceeded the recommended ultimate

design load by a factor of 1.8.

C. Static Uniform Load on Steel Faced Sandwich Panels [33]

Four roof panels were tested after each had been conditioned by one

of the following procedures:

1. 50% relative humidity at 73 + 3°F for five days

2. 95% relative humidity at 73 + 3°F for five days

66
REACTION BEAM

\~2-LVDTs

END SUPPORT ASSEMBLY \

(BOTH ENDS)

y/////////////// /\/ /////////,

\*~ 4 1/2" Wall (Typ) £. Span

9. ROCKER

I - 7 1/2

AIR BAGS

-3' -8" —

SECT A-A

DETAIL

A .l" Thick FRP LAMINATE FACING B POLYESTER ADHESIVE

C .05" Thick FRP LAMINATE

CORRUGATED CORE

D SAME AS "B" E SAME AS "A"

Figure 4.2.10 - Schematic of test setup for short term flexural test on roof panel.

67
3. Complete submersion in a water bath at 73 + 3°F for seven days and a subsequent 9-day drying period at

73 + 3°F and 50% relative humidity. Figures 4.2.11

and 4.2.12 show the test setup.

Again, as in the roof panel tests described (paragraph B) above,

the midpoint deflection measured during this test permitted a comparison

of the deflection-to-span ratio with that permitted by the governing performance

criterion as the support condition and loading technique were representative

of the design parameters.

4.2.3.2 Review of Tests

The test setup and procedures used for this series of tests, A through

C, followed ASTM E72 recommendations except that the air bag was sandwiched

between the laboratory floor and specimen instead of between the specimen

and a reaction frame, as called for in E72. Also, no air bag containment

plates were provided around the edges of the specimen; although in the

test on steel faced sandwich panels, side containment was provided by

the edge members of the panel (figure 4.2.11). It seems clear that reacting

the applied load uniformly against an existing laboratory floor simplifies

the test setup by eliminating the grid assembly from the reaction frame.

The grid would have to be tailored for different sizes of specimen, while

no alterations would be required for the laboratory floor. The advantages

and disadvantages resulting from eliminating the containment plates around

the edges of the specimen may not be quite as apparent as those resulting

from eliminating the grid assembly from the reaction frame; therefore

the effect of the former, warrants further discussion.

If edge -containment plates are provided, it still may not be possible

to fully determine the loaded area of the specimen, since the air bag

probably will not be able to fit exactly into the re-entrant corners along

the edges of the specimen, where the direction of confinement changes

from horizontal to vertical. If edge-containment plates are not provided,

either the air bag will extend beyond (i.e. be outboard of) the edges

of the specimen (except in cases where the edge members of the specimen

protrude above its surface as described in Section 4. 2. 3. IB) or the extent

of the area of contact between the air bag and the specimen's loaded surface

will be inboard of the edges of the specimen (see Sections 4.2.3.1A and

4. 2. 3. IB for descriptions of specimens without edge-member protrusions).

In the latter case, the absence of edge-containment plates allows the area not in contact to be observed. Consequently, measurements can be

made to determine the amount of unloaded area, and an accurate assessment

of the applied load can be made. This was the procedure followed during

performance of the tests summarized in Sections 4.2.3.1A and 4. 2.3. IB; the test summarized in Section 4.2.3.1C had confined edges due to the

construction of the panel. Both procedures appeared to give satisfactory

results

.

The concept of allowing the air bag to extend outboard of the specimen's

edges was not used in the test summarized in Section B due to weak longitudinal

panel edges (see figure 4.2.10). Neither was the outboard air bag arrangement

employed in the test summarized in Section 4.2.3.1A because of the risk

that the sharp edges of the specimen would cut the air bag. Three other

factors were also considered, the first one being that if the diameter

of the outboard portion of the air bag became greater than the distance

between the laboratory floor and loaded surface of the specimen, hoop

tension forces would introduce additional loading along the edges of the

specimen in the direction of the uniformly applied load. For example,

if the diameter of the outboard portion of the bag was 6 in, and the distance

from the laboratory floor to the loaded surface was 4 in, a force of 17.0

lbs per ft along the edges of the specimen could easily develop, for an

68
N

\

\

69
70
applied load of 72 psf. The second consideration was the air bag's membrane

stress, which can be calculated from the internal pressure, membrane thickness,

and radius of the air bag along the edges. However, this did not turn

out to be a problem; the air bag used to test the floor specimen of sandwich

panels with gypsum board facings attained an edge radius of almost 9 in

without rupturing, corresponding to an 18-in midpoint deflection of the

specimen. The third factor was the possibility of subjecting the panel

to in-plane forces caused by the radial pressure within the air bag. As

a result of these in-plane forces the panel would in effect become a beamcolumn and hence its true flexural strength and stiffness would be affected.

(The following section contains some recommendations regarding the use of

air bags) . In addition to this stability consideration for the panel

is the problem of local edge effects. Panels with weak edge construction

could be adversely affected by crushing or buckling as the pressure is

increased. All three of these factors should be considered according

to the details of construction of individual specimens.

4.2.3.3 Recommendations

The ASTM E72 test method for floor and roof panels clearly needs

to be modified to improve cost effectiveness and the capability of observing

the structural behavior during the test without degrading the simulation

of uniformly applied loading. This can be accomplished by employing methods

similar to those employed during the Operation BREAKTHROUGH structural

testing program for roof and floor panels. The major cost saving came

from devising a method which eliminated the grid assembly from the reaction

frame; also, with the elimination of the side containment plates, the

specimen was completely uncovered, permitting structural behavior of

the specimens to be more readily observed. An apparent drawback of this

simplified method stems from the inability to fully load the surface

of the panel. This certainly is not a drawback for panels with weak

edges, such as those described in Section 4. 2. 3. IB. On the other hand,

for many panels, it might seem desirable to load the entire surface.

This is not possible unless some portion of the air bag extends outboard

of the edge of the panel being loaded, which causes an undesirable edge

loading and creates the risk of damaging the air bag when testing panels

with sharp edges. Therefore, it is recommended that the structural test

method employed in the Operation BREAKTHROUGH testing program for physically

simulating support conditions and uniform loading of roof and floor panels

be further developed for adoption as a standard test.

It will be shown that the inability to load the entire surface of

panels, that are capable of resisting such loading without incurring local

damage along the edges, need not be considered a drawback. There are several alternative ways to account for this condition. The area reduction,

or its complement, the actual loaded area, can be observed during the test

and then calculated if appropriate measurements are made during observation;

or, the area reduction can be calculated prior to testing, using the geometry

of the specimen, air bag and test setup (see Appendix B) . Thirdly, the

imposed uniform loading can be measured. This can be accomplished by

using two reaction beams at each support, with load cells inserted between

them as shown in cross^-section B-B of figure B.2 in Appendix B.

The use of load cells provides the most accurate method of monitoring

the simulated uniform loading of the panel; however the use of load cells

adds to the complexity of the test setup, which will increase the cost

of performing the test. This increase in complexity and cost may not

be warranted if it can be shown that the other two approaches, (i.e. determining

the reduction in area during the test by measuring the width of the unloaded

area along the edge of the panel and calculating the reduced area from

the geometry of the air bag, specimen, and test setup) which employ knowledge

71
of only air bag pressure and contact area, do accurately monitor the simulated

uniform load.

Caution must be exercised when evaluating the results of a test in

which significant reduction in area occurred. It must be remembered that

although the total load obtained from a partially loaded panel may be

equivalent to the total load resisted by a panel that is fully loaded

with a uniform distribution, the resulting moments, shears and deflections

may be considerably different.

A test program should be devised to compare the results of the two

test setups which do not contain load cells to those of the test setup

which contains load cells. The scope of this test program should include:

a. evaluation of predicted loading using a single air bag

to load panels.

b. evaluation of predicted loading using two or more

air bags to load panels.

c. investigation over a full range of deflections from

zero to 20 in, recalling that one of the panels tested

in the Operation BREAKTHROUGH test program deflected

nearly 20 in.

d. development of techniques for continuously monitoring large

deflections efficiently and safely, (i.e. minimize

the necessity for resetting deflection gages)

.

4.2.4 Long Term Flexure Tests

4.2.4.1 Summary of Tests

A. Static Uniform Load on Sandwich Panels with Gypsum

Board Facing [22]

One roof and one floor panel were tested under environmental conditions

of 70 °F and 50% RH. The magnitude of the test load was 5 psf and 10 psf

for the roof and floor panels respectively; the test setup, specimen size

and details are shown in figure 4.2.13. The test results for the roof

panel specimen are shown in figure 4.2.14 as a curve which describes the

creep deflection as a function of time. Note that the time coordinate

is plotted on a logarithmic scale. The solid line in the figure approximates

the time-deflection relationship for an average relative humidity of 30%.

The broken line is an estimated time-deflection curve for an average

relative humidity of 50%; the latter RH value was judged to be the more realistic one for the specified design conditions. It is shown below

that these data can be used to predict the time -dependent deflection of

the actual roof system for its entire service life.

When the broken line in figure 4.2.14 is extrapolated from 300 days

to 50 years (18,000 days), a creep deflection of 0.81 in is estimated

for the roof panel. On the assumption that the data used to obtain the

extrapolation is statistically reliable, the boundary C support) conditions

of the test panel can be compared to those assumed for the actual roof

system (i.e. rectangular plates supported along all edges) to provide

an estimate of the creep deflection of the roof for the entire service

life. For the design load combination of one times the dead load and

0.25 times the live load (which amounts to 5 psf superimposed load) the

estimated creep deflection is 0.23 in. This procedure is also applicable

to the results of the floor panel tests.

72
19-71/2"

STEEL

ROLLER

DEFLECTION

GAGE

STEELROCKER

DRY SAND y

Mr^X:.',:-:;::

A. RETAINING RAIL

B. ROOF- 5/8" GYPSUM BOARD

FLOOR- 5/8" PLYWOOD

C. FRP LAMINATE

D. PAPER HONEYCOMB

, E. SAME AS'C'

F. 5/8" GYPSUM BOARD

DETAIL

Figure 4.2.13 - Schematic of long term flexural load test setup.

73
%'AliailAinH 3AI1V13H

Nl 'Nouo3U3a NVdSaiW

74
B. Static Uniform Load on Panels Fabricated From Glass

Fiber Reinforced Polyester Laminate [37]

A single roof panel specimen was tested in flexure under controlled

environmental conditions. Figure 4.2.15 depicts the test setup, dimensions

and details of the specimen.

The results of this testing are presented in figure 4.2.16. Midspan

deflections, temperature and humidity readings were taken for 280 days

but only the data from the first 100 days of the test period were considered

usable as a failure in the temperature and humidity control unit resulted

in erratic environment conditioning after this period. The data points

for days 12 to 100 lie approximately in a straight line when time is plotted

on a logarithmic scale. If this line is extrapolated to 50 years, the

maximum deflection due to creep can be calculated, assuming the reliability

of the data on which the extrapolation is based. This deflection, when

added to the instantaneous deflection caused by a live load yields a total deflection for a simulated long-term loading condition.

4.2.4.2 Review of Tests

The relatively small uniform load (25% of design live load) , applied

to the panels tested for BREAKTHROUGH resulted in a very low creep rate,

causing the test to be prolonged. To be effective, test methods for obtaining

data to evaluate creep should be obtained in a relatively short period

of time, say two weeks. It is evident that 25% of the design live load

sustained by a floor or roof specimen does not reflect service loading

conditions over the expected service life of the structure. The actual

loading is more a combination of a small -magnitude uniformly sustained

load and large-amplitude cyclic loading.

4.2.4.3 Recommendations

It is recommended that a test method using a combination of uniform

sustained and cyclic loading be developed to simulate service loading.

The magnitudes of both loads can be determined through studying existing

live load information. The test setup could be similar to the air bag

setup used in BREAKTHROUGH testing, with an automatic cycling device to

increase pressure to simulate temporary large-order loading superimposed

on a small-order sustained load. The cycling could be accomplished, say,

every ten or fifteen minutes. Starting with a low magnitude of uniform

loading, the results of the test will provide data needed to plot load versus number of cycles, and load versus deflection increase. The latter

could be accomplished by taking the difference between the first and last

cycle at a particular load. Some reasonable number of cycles of loading

must be determined; again, this can be determined through studying existing

live load information. A physical testing program should be developed

to verify the test procedures and the adequacy of the prescribed loading.

4.3 Wall Tests

4.3.1 Short Term Compression

4.3.1.1 Summary of Tests

A. Sandwich Panels with Gypsum Board Facings [22]

The aim of these tests was to evaluate the performance of full size

wall panels of single-story height under the action of short-term compressive

loads. Wall specimens were representative of exterior wall panels but

75
II '-7 1/2"

i i i~ i i i i iii

j

STEEL

ROCKER

STEELROLLER

DEFLECTION GAGE

SEE DETAIL

32"

5 ^3/4

'

SECT. B-B

Figure 4.2.15 - Schematic of long term (creep) sustained flexural load

test setup.

76
77
were of a width suited to test purposes; specimens were 4 3/8 in thick

by 24 in wide by 96 in high. Figure 4.3.1 is a photograph of a wall specimen

under test. The basic construction of the panels is shown schematically

in figure 4.2.8. The upper and lower 3 in of the core in each panel consisted

of laminated plywood bearing blocks bonded to the fiber-reinforced plastic

(FRP) laminate and the honeycomb core. The design of the wall panels

called for application of compressive loads to the walls through the wood

bearing blocks without any load bearing on the gypsum board facing. Two

panels, called "dry," were conditioned for 14 days in the testing laboratorycontrolled atmosphere of 73°F and 50% relative humidity (RH) and tested

immediately thereafter. Two other panels, called "wet," were preconditioned

for 4 days in the same laboratory, then exposed to a controlled atmosphere

of 160°F and 95% RH for 7 days, just prior to testing; all four specimens

were tested in the laboratory atmosphere described above. A total of

four tests comprised different combinations of "wet" or "dry" specimens,

and concentric or eccentric (1/6 of the panel thickness) loading. Load

application was substantially in accordance with ASTM E72-68.

B. Short Specimens of Sandwich Panels with Gypsum

Board Facing [22]

These tests were performed to evaluate the edgewise compressive strength

of the panel material without the effect of lateral deflections experienced

by the full-height wall panel tests described above. The four specimens

were 24 in high by 12 in wide by 4 3/8 in thick and were of the same construction as the full-height wall panels except for end conditions. The top

and bottom of the specimens were bonded with an adhesive to 14 -in. long, 2x6 wood bearing plates for test purposes. Figure 4.3.2 is a photograph

of a short-wall specimen ready for test. Two specimens were conditioned

for 11 days in air at 73°F and 50% RH. Two others were conditioned for

7 days in a steam-heated chamber at 160 °F and about 95% RH . All specimens

were tested at 7 3°F. The specimens conditioned at elevated temperature

and humidity were cooled to 73°F but were not dried before testing. Specimens

were loaded in a hydraulic testing machine by applying increasing concentric

compressive load until failure occurred.

C. Sandwich Panels of Glass-Fiber Reinforced

Polyester (FRP) Laminate [37]

Two wall panels, were tested in short-term compression to evaluate

their performance under simulated service loading conditions. The panels

were typical of those intended for use in service but also incorporated

two additional wood members at the top and at the bottom edges to facilitate

test simulation of service loading (figure 4.3.3). Each panel was 40

in wide, 96 in high and 3 7/8 in thick; except for these dimensions, the

basic cross section details are the same as those shown in figure 4.2.10.

Specimens were positioned in a compression testing machine so that the

load was applied at an eccentricity ratio (fraction of panel thickness)

equal to 0.26, as incurred in service. Generally, the rest of the test

procedure followed ASTM E72.

4.3.1.2 Review of Tests

One of the departures from the ASTM E72 method was in the positioning

of the test load on the specimen. In the case of the honeycomb-gypsum

board panels (see Section 4.3.1.1A), concentric loading was included so that a comparison of its results with those caused by E72 loading would

provide an indication of the relative effect of eccentric loading. In

testing the corrugated FRP panels, sufficient details were known about

service loading conditions to simulate them in the laboratory.

78

80
The use of linear variable differential transformers (LVDT) as compressometers and def lectometers (figures 4.3.1, 4.3.2, 4.3.3) made it possible

to automatically observe and record data for each load increment in a short

time interval —a particularly important factor in testing constructions

that creep readily. Moreover, in contrast with what is recommended by

illustration in figure 2 of ASTM E72 [5], the def lectometers were located

so that they spanned virtually the full length of the specimens, and measured

the deflection of the neutral axis . Another circumstance which influenced the test procedure was the

involvement with materials that, even with little structural history, were known to be sensitive to high temperature and humidity. The need

to know the percentage reduction in performance (especially of the paper

honeycomb -gypsum board panels) caused by exposure to such conditions was

quite evident. A less obvious aspect of this kind of procedure, however, was the choice of laboratory exposure conditions for a realistic simulation

of service exposure

.

Testing of the short specimens of sandwich panels with gypsum board

facing (see Section 4. 3.1. IB) elicits two observations. First, adhesivebonded wood 2x6 plates provided satisfactory bearing at the loaded ends

and prevented localized test-related bearing failure, thus permitting

the determination of representative values of strength and stiffness.

Secondly, the height-to-thickness ratio of the short specimens (approx.

5 1/2) was an arbitrary choice and therefore does not reflect sufficient

systematic regulation.

4.3.1.3 Recommendations

Provision should be made in ASTM E72 for positioning the compression

test load in its service location on the wall, if it is known. Similarly

if the test is to be a realistic one, consideration should be given to

requiring simulation of wall support and restraint conditions. If this

kind of information is not known, then a generalized type of procedure

could be employed. Furthermore, such a generalized test would need additional

fundamental study. For example, location of test load, as well as manner

of bottom edge support (flat or roller) should be reconsidered. Location

of instrumentation on the specimen should be improved to minimize errors,

and recommendations for instrumentation should be modernized to facilitate

rapid observations and reduce manpower requirements.

A standarized compression test should take into account the detrimental

effects of environment on the wall structure. Conditioning procedures

for laboratory simulation will have to be established by research. These

procedures should entail pre-conditioning as well as test conditions.

The testing of short compression specimens should be considered as a recommended complement to wall tests. These would provide strength

and stiffness values for use in design calculations of load capacity and

deflection to be compared with test observations. The choice of a heightto-thickness ratio for these short specimens requires study for standardization,

however, since there is a diversity of values now in use.

4.3.2 Long Term Compression of Sandwich Panels of GlassFiber Reinforced Polyester (FRP) Laminate [37]

4.3.2.1 Summary of Test

Two wall panel specimens, identical to those used for short-term

compression (Section 4.3.1.1 C) , were tested under a sustained compressive

81
design load as shown in figure 4.3.4; the load eccentricity was the same

as in the short-term compression test of the panels. Two support conditions

were used. Both specimens were originally loaded using the flat bottom

bearing illustrated in figure 4.3.4. Later, the set-up of one specimen

was changed to employ a roller bearing at the bottom providing the same eccentricity as at the top (figure 4.3.5). Both of the above-mentioned

figures also show the springs used to sustain the test load, and the mirrorbacked graduated scale and taut wire used for measuring deflection.

4.3.2.2 Review of Test

The basic set-up, shown in figure 4.3.4, for sustaining a constant

compressive load on a wall panel functioned satisfactorily. Load can

be monitored in such an arrangement either by measuring the length of

the springs or the strain in the tie rods. Visually measured deflection

was an adequate indication of creep experienced by the specimen under

eccentric compressive load.

However, still open to question is the choice of test load magnitude

and manner of application that can provide, in a relatively short time,

creep data which are indicative of projected performance over a much longer

period

.

4.3.2.3 Recommendations

As in the recommendations for the short-term compression test, the

same factors of load eccentricity, edge support and restraint, and environmental

conditioning procedures must be studied and standardized for application

to the long-term compression test.

A need which is peculiar to the long-term compression test is its

particular standard procedure for applying the load. It is generally recognized

that a wall probably does not bear a full design load for the entire period

of its life. On the other hand, a reduced sustained test load, which is an estimate of a life time average, would not produce creep data soon enough for practical purposes of evaluation. Research is needed to develop

a short-duration test procedure (possibly sustained load combined with

cyclic loading) that will produce data which can be correlated with prolonged

creep test data. It is likely that in the development of such a procedure,

assistance can be gained from techniques resembling those used in obtaining

curves which relate stress levels and number of cycles of loading (i.e. fatigue

curves) ; data resulting from current structural live load investigations could

also be used to further the stated objective.

4.3.3 Racking of Sandwich Panels of Glass-Fiber Reinforced

Polyester (FRP) Laminate [37]

4.3.3.1 Summary of Test

To evaluate performance under the action of short-term racking loads, one wall panel specimen was tested in a normal vertical position by subjecting

it to horizontal racking forces. The 3 7/8-in-thick specimen, of the

same basic cross section as the compression specimens (Section 4.3.2), was nominally 7 ft wide by 8 ft high (figure 4.3.6). The height of the

panel was extended by using two 2 x 4's nailed and adhesive-bonded along

the top and bottom edges of the panel. These attached members were intended

to distribute the racking load and its reaction horizontally along the

top and bottom edges of the test panel. The specimen was made of two

82
Figure 4.3.4 - Long term compressive load test with Figure 4.3.5 - Long term compressflat bottom support. ive lead test with

eccentric bottom

support.

83
Figure 4.3.6 - Test setup for racking test No. 1.

34
panels, approximately 3' -6" wide; the panels were connected by the fabricator

through the use of joint-cover plates made of the same FRP and adhesive

as the panels.

Three racking tests were performed on the one specimen by re-setting

the specimen between tests. The apparatus for the three different tests

is shown respectively in figures 4.3.6, 4.3.7 and 4.3.8. Loading was accomplished by hydraulic rams attached to a structural steel framework connected

to the laboratory tie-down floor. The specimen was bolted and clamped

(by the two bottom 2 x 4's) between steel channels which were bolted to

the test floor (figure 4.3.6) Lateral guides and a toe-stop, recommended

in ASTM E72, were used. Vertical hold-down, used in some of the tests, was provided by hydraulic rams attached to the test frame.

In the first test (figure 4.3.6) the racking load was increased gradually

until an indication of impending failure was observed. No vertical holddown from above the wall was supplied in this test to allow possible rotational

failure to develop at the bottom. Racking load was applied in increments.

In the second test the racking load was applied incrementally and

reduced to zero after each additional increment was applied. The racking

was increased until failure developed. Vertical hold-down was supplied

at the loading corner by a hydraulic ram which was loaded to provide a restraining moment equal to that of the racking load (figure 4.3.7).

The third test was conducted in the same manner as the preceding

test except that the vertical hold-down above the wall was provided by

six equally spaced rams operated simultaneously by a common pump. The

vertical resultant of these rams was always such as to develop a restraining

moment equal to that of the racking load (figure 4.3.8).

4.3.3.2 Review of Tests

Although less desirable than using a new specimen for each test,

it was possible to perform three variations of a racking test on the one available specimen because failure in each test was anticipated (and occurred)

in different areas. This was so because, in each of the succeeding setups,

the failure area of the preceding test was no longer a critical area for

the type of loading used in the following test. The tests were expedient

attempts to examine the resistance to racking forces on the wall offered

under different circumstances: 1) by attachments near the floor alone,

2) by vertical reaction at the loading corner, and 3) by distributed

vertical reaction along the top edge of the wall; each in conjunction

with a toe-stop and an accompanying reaction at the corner diagonally

opposite the loading corner. A consideration of such tests leads to the

question of what a standard racking test should evaluate. Proposals might

conceivably include a) performance of wall connections to adjacent structure,

b) shear strength and stiffness of the wall construction alone, c) effect

of superimposed live loads, or d) combinations of the foregoing.

4.3.3.3 Recommendations

An approach to developing a realistic standard test for measuring

racking performance of walls must include studies of numerous factors.

Probably the most important of these is the establishment of guidelines

for imposing the proper edge conditions on the wall specimen. Such edge

conditions include the manner of wall support and attachment at its base;

the amount and distribution of restraint to be applied around its perimeter;

and the manner in which the racking forces, themselves, should be distributed.

For example, should a wall be tested in racking while under constant vertical

forces simulating bearing loads, or, should it be tested in as nearly

pure shear as possible? Should racking forces be applied along the entire

85
86
height of the wall, and should they be cycled and reversed? These are some of the areas of recommended research.

Since racking is caused by short-term wind and seismic forces it

is probably unnecessary to investigate creep test methods. However, as

in other tests, the need for employing environmental conditioning of specimens

exists here also, and should be considered for application to a standard

racking test.

With regard to the purpose of conducting a racking test, very little

information exists in the form of specifications to be met by racking

performance of walls. Aside from developing testing techniques, therefore,

much study is needed to determine limiting values of racking drift, caused

by wind and seismic forces, that will provide safety and comfort for the

occupants of a building.

4.4 Full-Scale House Tests

4.4.1 Summary of Tests

A. Full-Scale Test on a Two-Story House Subjected

to Lateral Load [53]

The primary purpose of this field test program was to measure the

lateral drift of a conventional, two-story, wood-framed house under simulated

wind load to determine whether the drift limitation required in the design

of medium- and high-rise buildings is applicable to low-rise housing units.

A secondary purpose was to determine the dynamic response characteristics

of the house under lateral impulsive load. A front view of the 47 -ft by

26 -ft house is shown in figure 4.4.1.

Table 4.4 summarizes the static tests performed; and figure 4.4.2 shows

the location of loading points and the deflection transducers. Lateral

forces were first applied at the second-floor level and then at the eave

line. The separate effects of these forces were combined to compute a total effect, using the principle of superposition. The loading arrangement

at the lower level is shown pictorially in figure 4.4.3. The measurements

in this first experiment included loads, vertical deflection, horizontal

deflection of floors and walls and racking deformation of walls. Thirtytwo displacement transducers were used to measure deformation of the house

and racking distortion of walls. All displacement transducers were placed

inside the building to be maintained at a temperature of approximately

70°F and to protect the equipment against inclement weather. As a result

of placing the supports for the deflection transducers inside the house,

the reference for the measurements (i.e. the second-floor surface), made

at the eaves line translated with respect to the ground floor. Thus,

the movement of the reference for the upper story measurements had to

be allowed for in determining the drift values for the house.

In the experiment to determine the dynamic response of the building,

a 12-in-long piece of steel pipe was inserted between one of the loading

rams and the corresponding loading plate located on the lower level. After

a predetermined load was applied, the pipe was removed by a sharp hammer

blow, and the deflection amplitude was recorded as a function of time.

Two of the 32 deflection transducers were used to measure the dynamic

response and the data were recorded by a strip-chart recorder.

B. Structural Tests on a Wood Framed Housing Module [51]

A series of six structural tests was performed on a wood-framed,

volumetric, housing module, subsequent to a series of tests relating to

87
Figure 4.4.1 - Front view of the building.

Table 4.4 - Summary of static tests. (See figure 4.4.2 for locations

of loads )

.

Test

No. Date

Loading

Points

Loading Sequence

kip Conditions Comments

1 2/5/71

pm

A,B f C,D 0 - 5.63 - 0.14

0.14 - 8.00 - 0

0 - 7.93 - 0

Cloudy

35°F

Loading was limited by frictional

resistance of

forklifts

2 2/6/71

am A,B ,C,D 0 - 10.00 Sunny

40°F

Horizontal resistance was increased by blocking of

forklifts

.

3 2/7/71

am E,F,G,H 0 - 2.00 - 0

0 - 4.Q0 - 0

0 - 6.00 - 0

0 - 7.23 - 0

Rainy

36°F

ii

4 2/7/71

pm

A,B,C,D 0 - 10.00 - 0 Rainy

36°F

it

88
All LVDT's near the side walls, except the LVDT's at the center vertical plane, were set 5.5" below the ceiling and 9" away from the wall.

LEFT WALL

RIGHT WALL

REAR WALL

PLANE ON WHICH BUILDING WAS INSTRUMENTED

Figure 4.4.2 - Locations of transducers and loading points.

Figure 4.4.3 - Loading arrangement.

89
transportation by rail. The general objective of the structural tests

was to quantify some of the structural characteristics (e.g. lateral stiffness,

floor-vibration response and deflection-recovery behavior) of the module

which were not conducive to analysis. The factory-built module is shown

in the bold outline of the schematic drawing, figure 4.4.4. The six tests

performed were: 1. Service Life Racking (Test 1) , 2. Transient Floor

Vibrations (Test 2), 3. Sustained Floor Load (Test 3), 4. Repeated Racking

(Test 4), 5. Reversals of Racking (Test 5) and 6. Racking to Capacity

(Test 6) . The module was visually inspected for damage or other evidence of

structural distress, upon its arrival, via rail, at the laboratory. All

cracks and other forms of local damage were systematically documented.

Prior to lifting and transporting from the factory, reference points had

been established on the exterior and interior wall surfaces and linear

measurements were made between the reference points. These measurements

were repeated in the laboratory, to determine any dimensional changes

in the module caused by the handling and shipping operations

.

In Test 1, the module was subjected to the static concentrated loads

simulating wind forces normal to the front face of the house and the resulting

horizontal and vertical deflections of selected points were measured.

The loading ram locations are shown in figure 4.4.5 and the exterior

deflection-measuring instruments are presented schematically in figures

4.4.6 and 4.4.7. From the results of this test, the drift at the secondfloor level in the actual house was estimated for several values of design

wind pressure. To obtain these estimates of second-floor drift, an analytical

model was derived to provide a kind of "transfer function" between the

results from the test module and the response of the actual structure.

The objective of Test 2 was to determine the damping behavior of

the floor when subjected to vibrations of relatively short duration,

such as those induced by human activities. This test recorded the decay

of the deflection amplitude, with time, following a single-impulse excitation.

An impact load was applied to the floor as a result of releasing a 25-

lb bag which was attached to the head of a tripod at a height of 3 ft.

The deflection amplitude was measured with a deflection transducer and

recorded on an oscillograph.

In Test 3, a factored uniform load was applied by sand bags over

the entire surface of one floor of the module and sustained for 24 hours.

Vertical deflections at five points were recorded immediately after the

proof load was applied and several times during the subsequent 24 hours.

The ability of the floor to return to its initial position was quantified

by recorded measurements made at the same points immediately upon unloading

the floor and several times during the subsequent 24 hours.

To document any detectable decrease in serviceability, and to determine

if a reduction in lateral stiffness resulted upon the module being subjected

to repeated applications of lateral loading, Test 4 was performed. Onethousand cycles of simulated wind force, oscillating between zero and

one-half the design wind pressure, were applied at right angles to the

front face of the module. Figure 4.4.8 locates the two loading rams used

for this test. The shortened version of the test structure resulted from

severing a portion of the original module following Test 2. Following

a single cycle of static loading, the 1000 cycles were applied automatically

in twenty blocks of 50 cycles each, at a frequency of 1 Hz. The residual

deflections at the end of each 50-cycle block were recorded to determine

the ability of the module to recover its original geometry.

90
91
Figure 4.4.6 - Exterior instrumentation on the rear —Test 1. 92
Figure 4.4.8 - Ram locations for Tests 4, 5 and 6. 93
The objective of Test 5 was to describe, qualitatively, the extent

of distress and damage to all visible connections and exposed components

as the module was subjected to loading that corresponded, in magnitude,

to earthquake design provisions for two-story structures in the 196 7 edition

of the Uniform Building Code. Five cycles of reversed lateral load, oscillating between plus one times the design earthquake load and minus one times

the design earthquake load, were applied to the front face of the module.

Since there is no known requirement for deflection limitation of a structure

subjected to such loading, the main consideration was the effect on the

visible joints in the module and the change in lateral stiffness. Figure

4.4.8 locates the two loading rams used for this test.

Test 6 was an ultimate load test intended to assess the maximum lateral

load which the module could withstand. Four hydraulic rams (see figure

4.4.8) were used to apply concentrated forces in increasing magnitude

until failure occurred. Deflection data were periodically recorded and

the module was visually examined for signs of distress and damage.

4.4.2 Review of Tests

A. Full-Scale Test on a Two-Story House Subjected

to Lateral Load [53]

There is no standard test method for field testing of full-scale

houses with which to compare the two experiments which comprised this

test program. As was stated in Chapter 3, the development of a set of

guidelines by a joint ASTM-ASCE Committee, for use in testing complete

nouses is in the planning stage. Nevertheless, the investigation can

be discussed with respect to its treatment of key test parameters and

the possible value of the test results.

In the general field of structural performance testing, the method

of load application should be chosen to represent, as closely as practicable,

the known or assumed design load characteristics. Likewise, the manner

of the test structure's resistance to the test loading should closely

represent the actual service reactions. While the simulation of componentto-component and component-to-foundation connections is often a difficult

and expensive undertaking in laboratory testing, this parameter is inherently

accommodated in field testing of existing houses. On the other hand,

the simulation of a uniform wind pressure, which is usually assumed in

design of low- and medium-rise buildings, is generally more difficult to

accomplish in field testing.

As described in summaries of previous tests of full-scale houses

(see Section 2.5), the application of a series of concentrated loads at

approximately the eave line and/or the floor of a test house, has been

the most commonly used field method for representing the effect of an equivalent static wind pressure acting normal to one face of the erected

building. Assuming that the test house has the same dimensions as the

building, this loading arrangement effects a simulation of both the design

overturning moment at the top of the foundation and the racking forces

distributed to the tops of the shear walls. These two representations

are accomplished at the expense of not simulating the design base shear.

Depending on the geometry and type of construction being investigated,

the consideration of the latter detail may be more important than the

other two.

The technique of loading the house one level at a time and combining

the two sets of responses was justified in that the requirements for the

application of the principle of superposition were satisfied. The results

confirmed the assumption of linearly elastic response of the house. Also,

94
the resulting deflections were sufficiently small to allow all measurements

to be referenced to the original geometry.

Typical of field testing procedures, the loading method was not readily

adaptable to either reversals of loading or relatively rapid repetition

of one-directional loading. However, the use of hydraulic rams did afford

a couple of test advantages: the rate of loading could be easily controlled

and the relatively slow repetition of one-directional racking loads, for

a small number of cycles, could have been accomplished. It is likely

that the use of two separate and redundant systems (a pressure transducer

and two load cells) for measuring the load produced a degree of accuracy

of less than the 2% maximum recommended in reference [38]

.

The placement of all deflection-measuring instruments inside the

house, in lieu of using a series of two-story -high frames for supporting

the instruments outside, was a practical solution to the anticipated problems

posed by inclement weather and inadvertent jolting. Furthermore, this

technique of measuring displacements is a good illustration of the necessity

for compensating in the observed results for expected movement of the

datum point. Since the second floor was expected to translate as a result

of the lateral load, its displacement had to be added to that measured

at the eave line to determine the magnitude of drift.

It is desirable that a test method be practically reproducible in

order to establish a basis for comparing the structural performance of

similar structures. Furthermore, the structural performance can be evaluated

against a standard of performance as specified in a code, standard or criteria document. To these ends, this investigation has made a contribution

since the results seem to be reproducible and the test was performed on

a common type of house construction.

B. Structural Tests on a Wood Framed Housing Module [51]

The fact that six separate structural tests were performed during

this investigation does illustrate the point that a relatively large number

of non -destructive tests can be performed on a single prototype specimen.

Furthermore, for serviceability tests such as floor flexural and vibration

tests, the evaluation is effectively supplied with several full-scale

specimens whose test boundary conditions are identical to the in-service

boundary conditions.

Most of the test methods comprising this investigation probably do

not represent practical models for the development of standard laboratory

test methods, since the laboratory facilities and the test equipment were

atypical of the US population of test organizations. Nevertheless, some

of the prevailing concepts and the manner of handling some of the test

parameters warrant discussion.

By referring to the test setup for the four racking tests (1, 4, 5 and 6) , it is seen that a relatively large number of deflection-measuring

instruments is required by a module of this size and the data acquisition

task becomes tedious if there is no automatic data-recording equipment.

The technique of instrumenting the structure along discrete planes seems

to be an efficient way to employ the deflection gages. Sufficient information

can be obtained to define the deformation pattern of several planes in

the structure. The planes may coincide with actual end walls and interior

partitions or they may be imaginary. Subject to the qualifications imposed

by a straight-line approximation between the data points, the response

of the entire prototype can be interpolated or extrapolated.

95
Considering the length of the test module, the use of a series of

concentrated loads at the eave line seems to be a practicable representation

of the uniform wind pressure assumed in design. For laboratory test purposes,

the loading simulation probably could have been improved by using loading

beams between the rams and the surface of the module to further distribute

the ram loading. The degree of improvement has not been quantified by

research results, so it is not possible to assess the compromise involved.

The repeated lateral loading test (Test 4) and the test involving

reversal of loading CTest 5) were performed using ad hoc procedures which

manifested the evaluators ' interpretation of applicable performance requirements with respect to the effects of wind and earthquake, respectively.

In effect they were pseudo -dynamic , proof-load tests, in which the predetermined

peak loads were certain factors times the assumed design load and the

number of cycles was designated to conservatively simulate the structural

effect of repeated applications of wind pressure during service life and

of load reversals during a major earthquake. Since the main consideration

was the effect on the visible joints and the change in lateral stiffness

of the structure, the simulation of actual boundary conditions was a very

important test parameter. Specifically, the predicted line of weakness,

the joint located at the base of the prototype, had to be prepared in

strict accordance with the design specifications for the housing system.

A notable shortcoming of applying a cyclic loading within a relatively

short period (conversely, high frequency) was that the response data (from

about 40 channels) could be recorded only at the zero load occurring at

the ends of a predetermined number of cycles; or else a "static cycle,"

in which the load was manually controlled, was necessary. Ideally, the

rate of scanning for the recording device should be about two times the

frequency of loading to insure the acquisition of reliable, continuous

data. Then, any changes in the response characteristics of the structure

can be associated with a particular cycle and amplitude of loading. As was the case for Tests 4 and 5, it may be necessary to compromise the

ideal to the extent of obtaining data at some point when the load is stationary.

Thus, it is seen that the scanning rate capability of the data acquisition

equipment may be a controlling factor in establishing a test procedure

for cyclic loading.

The importance of achieving a close simulation of the design load

characteristics and the field boundary conditions (i.e. anchorage and

joining) as well as the benefit of performance criteria related to acceptable

structural performance was emphasized at the conclusion of Test 1. It was then that it became necessary to determine the significance of the

deformation in relation to the prediction of lateral stiffness for the

erected house. In the absence of an accepted maximum allowable drift

for low-rise buildings and houses, the conventionally accepted value for

medium- and high-rise buildings (height/ 500) was used. Since the anchorage

conditions for the prototype were held to be congruous with the joining

and anchorage conditions in the erected house the analytical model was effective in yielding an estimate of drift. The exercise of comparing

this estimate with a lateral deflection limit accepted for high-rise buildings,

can be considered academic until such time as a maximum allowable drift

for low-rise construction is reconciled with occupancy and serviceability

requirements

.

The development of performance criteria pertaining to transient vibration

response of floor assemblies is in a preliminary stage, at present. For

this reason, the significance of a vibration test such as Test 2 cannot

be fully assessed. It is first necessary to determine the relative importance

of such vibration parameters as damping and natural frequency on human

perception. Such is the nature of one of the phases of a long-range research

program being conducted at NBS, entitled Structural Deflections . For

96
the purpose of comparing frequencies and percentages of critical damping

among various types of floor construction, the test method seems effective.

The test equipment requirements are not extensive and the test setup is

simple enough to encourage uniformity of procedures.

The procedures used in Test 3 were similar to those recommended in

ASTM Standard E196-66, "Load Tests of Floors and Flat Roofs", and only

one feature warrants some discussion. Due to the inaccessibility of the

underside of the test floor, it was necessary to attach the deflectionmeasuring instruments to the top surface of the floor. To eliminate the

effect of a person's weight being superimposed on the sand bags during

testing, it was necessary to record the deflection data remotely. The use of a strip chart recorder (for two of the five data points) served

this function adequately, and provided a time-record of the test load

and zero load deflection as well.

4.4.3 Recommendations

Based on the review of these two full-scale house tests, a partial

list of research needs is suggested:

• A co-ordinated national effort is required to collect

and correlate structural performance data relative to

the lateral resistance of existing houses and low-rise

buildings. This data would probably have to be

supplemented with the results from further field testing

of both traditional and industrialized housing. The

principal obj ective to be served by such an effort would

be to establish a basis for code requirements for the

maximum allowable drift of houses and low-rise buildings.

• A comprehensive set of guidelines is needed to promote

the unification of both field- and laboratory -testing

procedures as they pertain to full-scale houses or modules. As is mentioned in Section 3.1, it is planned that

a joint ASTM-ASCE Committee be established for the purpose

of drafting a set of guidelines. Perhaps this activity

should be paralleled with a study of alternative ways to

accommodate certain test parameters. Typical subjects

for investigation are "effective techniques for measuring

deflections" and "advantages and disadvantages of various

load simulation practices."

• A laboratory test method encompassing repeated, one- directional lateral loading and reversals of loading

should be developed for industrialized housing prototypes.

As a prerequisite to the test method, it will be necessary

to reconcile such test parameters as 1000 cycles of

repeated loading and 5 cycles of load reversal (requirements stated in the HUD Operation BREAKTHROUGH Guide

Criteria) with the state-of-the-art as it pertains to

earthquake and wind effects on houses.

• Basic research is needed to determine the limits of

floor vibrations which are perceptible by humans as well

as to identify the vibration parameters which contribute

to the perception. Once this information is known, an improved test method which will assist in the evaluation

of a floor's vibrational performance can be devised.

It is anticipated that these objectives will be fulfilled

by the structural deflections program in progress at NBS

.

97
The continued use of the method employed in Test 2 is recommended, since it does yield worthwhile information

about floor damping. There are substantial test data

available with which to compare future test results.

• Before the development of more representative racking

and diaphragm test methods can be realized, it is

necessary to obtain a better understanding of the

interaction of building components and the stiffness

and strength of joints and anchorages. Contributions

to this effort can be made by existing information such

as that reviewed in Section 2.5 and that discussed in

Section 4.4. However, this information must be augmented by

data obtained from laboratory tests on segments of

full-scale buildings and full-scale prototypes. It

is recommended that laboratory tests be conducted on several full-scale assemblies, representative of building construction types for which existing information

is insufficient.

5.0 Review of Codes, Standards and Criteria with Respect

to Structural Test Requirements

The primary reason for undertaking practically all structural performance

testing is that many requirements in design standards or codes dictate

proof of compliance in the form of test results. The provision for the

acceptance of building components; new construction techniques and materials

applications; and entire buildings on the basis of some form of load testing

is made, either implicitly or explicitly, in many design regulations.

As a prerequisite to the development of standards for structural testing,

it is necessary to identify those requirements which dictate testing and

to examine the intent of the requirements relative to the built structure.

To this end a representative sample of codes, standards and performance

criteria, both domestic and foreign, were reviewed by the authors. To

provide a convenient reference the principal requirements of these documents

have been summarized in table 5.5.

According to a report [3 8] by an ad hoc committee on the testing

of structures, set up in 1962 by the United Kingdom Institution of Structural

Engineers, "There are two general types of tests, either of which may

be carried out in situ or under laboratory or other special conditions:

(i) An acceptance test to check the behavior of a structure

or part of a structure, under a load equal to or greater than the known working load, so as to assess its adequacy for service.

If a structure fails to meet the acceptance test

requirements in regard to recovery of shape after

load removal, it may sometimes still be accepted if

it meets the special requirements of a re-test.

(ii) A test to destruction to determine the ultimate

strength of a structure and hence either the load

factor or, conversely, the working load that will

be permissible with a given load factor.

Most of the testing suggested by the following standard and code

requirements pertain to the first general category.

98
5 . 1 Review

ACI Standard 318-71 - "Building Code Requirements

for Reinforced Concrete" [2]

Chapter 20 - Strength Evaluation of Existing Structures

The circumstance dictating a static-load strength test is the existence

of a structure or part of a structure whose margin of safety is suspected

by the "Building Official" in charge of approving the structural system.

The essence of the testing is that a proof load or overload is applied

and maintained on the designated test area for a specified period of time.

If the structural performance of the test area is acceptable under the

loaded condition and also upon removal of the proof load, the structure

or part of the structure passes. One retest is permitted if the performance

requirements are not met on the first trial, provided there is no visible

evidence of failure. It is emphasized that the scope of this testing

does not include considerations of serviceability (e.g., stiffness), quality

control or ultimate strength.

There are no recommendations made relative to test setup, apparatus

or procedure. However, the load factors to be used for the superimposed

load, as well as the duration of loading, are given in (ACI-318) Section

20.4 (paragraphs 20.4.3 and 20.4.4). The total load on the designated

section of the structure, including the existing dead weight, shall be

equivalent to 0.85 times the quantity (1.4 times the dead load + 1.7 times

the live load) . At least four approximately equal increments should be

used to reach the maximum load; the critical deflections shall be measured

24 hours after its removal. Provided the structure does not exhibit signs

of failure, its deformation behavior must satisfy several quantitative

criteria. If the limit established for maximum deflection is not exceeded,

the recovery characteristics are not to be measured. For relatively flexible

construction, where the maximum deflection does exceed the limit prescribed

in paragraph 20.4.6, the deflection recovery must be at least 75 percent

of the maximum deflection for non-pres tressed concrete (80 percent for

prestressed concrete) within the 2 4 hours after load removal.

The provisions in Chapter 20 are common to several other domestic

codes and to foreign codes in which the behavior of concrete structures

is under consideration.

American National Standard A119.1, 1974

"Standard for Mobile Homes" [3]

Part B - Section 6.6 - Walls

The strength requirements for the walls are such that tests applying

axial loading, transverse loading or racking loads may have to be conducted

to demonstrate the adequacy of a component's strength. No test methods

are explicitly suggested, but the standard methods found in ASTM E72 would

generally be appropriate.

Part B - Section 6.9 - Floors

"Floor assemblies shall be designed in accordance with accepted engineering practice to support a uniform live load of 40 lb/ft^, plus the dead load

of the materials. In addition (but not simultaneously), floors shall be

able to support a 2 00 -pound concentrated load on a 2 -inch diameter disc at

the most critical location with a maximum deflection not to exceed 1/8 inch

relative to floor framing.

99
Part B - Section 6.11 - Structural Load Tests

"Every structural assembly shall be capable of sustaining its dead

load plus superimposed live loads equal to 1.75 times the required live

loads for a period of 12 hours without failure. Failure shall be considered

rupture, fracture, or residual deflections which are greater than the

limits in 6.10 of this part."

Australian Standard CA 65-1972, "The SAA Timber

Engineering Code" [6]

Section 9. Testing of Timber Structures or Elements

Two types of load tests are considered. "One is a 'proof load test which

shall be applied to every structure of a population of structures for

them to be accepted. The other is a 'prototype' load test which needs

to be applied only to a portion of a population of structures for all

structures of that population to be accepted. " In both of these types

of tests it is necessary to apply a load factor to account for variability

in structural strength. The circumstances under which testing is required

are the same ones cited in section 5 of British Code of Practice CP 118

til] . A two-stage procedure is prescribed for determining the test load

for the proof testing. First, the critical combination of design loads

is specified by the design engineer or is determined from appropriate

codes and specifications. Secondly, the equivalent test load (ETL) is

calculated from the following formula:

2 • 1 K_ , K__

ETL = — (Px + 1.4 (P

2 + P

3 + P

4 + . .))

where

P^ = known permanent load on the structure such as its self

weight

P

2' P 3' P 4' ' " = ot^er imPose<3 loads

K

1 = the factor from Table 5.1 appropriate to the design

load of shortest duration included in the critical

combination

= factor obtained from Table 5.2 to compensate for

effect of duration of load on strength of special

components

K-^ = factor obtained from Table 5.3 to compensate for the

fact that test load is not of 15 minutes' duration."

Several factors are incorporated into the formula to compensate for the

effect of duration of loading on timber components. The uniform rate

of loading and a 15-minute duration of the ETL are required. Some guidelines

for acceptance criteria for strength and stiffness are also included, such as the possible requirement for a retest should the load-deflection curve show

any discontinuities or non-linearity.

The provisions for prototype testing include some requirements for

the materials used in the prototype. Only that grade of timber which

is specified for production can be used in the prototype. Furthermore,

the material used for the prototype should contain the upper limit of

imperfections permitted for a given stress grade, as far as practicable.

100
Table 5.1 - Duration of load factor for strength

(Table 2.4.1.1 in CA-65)

niir^i"i uui on o "F

a. u i ui i wju load

Multiplying

factor

K

l

Duration of

load

Multiplying

factor

K*1

Permanent 1.0 1 day 1.4

5 years 1.1 6 hours 1.5

6 months 1.2 1 hour 1.6

2 months 1.25 10 minutes 1.7

2 weeks 1.3 1 minute 1.8

5 days 1.35 5 seconds or less 2.0

Table 5.2 - Compensation factor

(Table 9. 4. 1 in CA-65)

Structural Component Factor K_-

. . 26

Columns, beams and arch elements with slenderness coefficients

greater than 10 - Timber initially dry

Timber initially green

1.1

1.4

Metal connectors - Failure in timber that is initially green

For failure of steel

1.2

0.6

Table 5.3 - Compensation factor

(Table 9.4.2 in CA-65)

Time to reach ETL 15 min 30 min 1 hr 2 hr 6 hr

Factor K

27 1.00 0.98 0.96 0.93 0.90

101
The equivalent test load is found by another formula, which includes

an additional factor, K28, (see table 5.4 for a list of values for this

factor) in the numerator to account for the number of units to be tested

and the estimated coefficient of variation of strength for the total population

from which the test units are selected. Furthermore, the constants 2.1

and 1.4 in the formula for proof testing are changed to 2.2 and 1.0 respectively

for prototype testing .

The test procedure calls for a preload, equal to the design longterm load, to be maintained for a five-minute period and then removed.

Subsequently, the prototype is to be loaded, at as uniform a rate as practicable,

until either failure or the ETL is reached, whichever comes first. Guidelines

for acceptance of the strength and stiffness characteristics of the prototype

are also given. For example, no specimens may show any sign of failure before

reaching the ETL; nor may any residual deflection or deformation exceed 5%

of the acceptable amount under short-duration loading.

British Standard Code of Practice, CP 112 (1967)

"The Structural Use of Timber" [9]

Section 6 is entitled "Inspection, Testing and Maintenance." Paragraph

602 sets down the provisions for testing of timber structures, with no specific components being designated. The circumstances dictating the

testing of timber structures or parts of such structures are substantially

the same as those cited for aluminum structures (see reference [11]) . There is no method indicated for the application of loading or the points

at which to measure the deflections, for these decisions would depend

upon the specific structure or components to be tested. As close an approximation of the actual loading and support condition as possible is required.

A loading and deflection recording sequence is outlined for a stiffness

evaluation test and the duration of loading is specified. For a period

of 30 minutes prior to performing a given load test, a preload equal to

the design long-term load, should be maintained on the structure or structural

component. This preload should cause a settling-down of the test specimen.

Subsequent to testing for stiffness characteristics, the strength of the

test specimen is assessed by loading at a uniform rate until 2-1/2 times

the design load is applied or failure is induced.

British Standard Code of Practice, CP 114 (1957)

"The Structural Use of Reinforced Concrete in Buildings" [10]

Section 605. Load Testing of Structures

There is no specific procedure fully outlined in this section, but

the load levels, duration of loading and relaxation requirements suggest

the application of a static load test. The conditions dictating testing

are requirements by the specification or the presence of reasonable doubt

about the adequacy of the strength of the structure. A curing period

of 56 days before testing is recommended.

The specified superimposed test loading is one and a quarter (1-

1/4) times the design superimposed load. The test load should be maintained

for 24 hours and then removed. If within 24 hours after the removal of

the load the structure does not show a recovery of at least 75 percent

of the maximum deflection reached during the 24-hour loading period, the

test loading should be repeated. Acceptance of the adequacy of the structure

is then dependent upon a recovery of at least 75 percent of the maximum

deflection during the second loading test.

102
Table 5.4 - Sampling factor

(Table 9.5.4 in CA-65)

Number of Similar

nits to be Tested

Value of sampling factor K 2 8 for estimated

coefficient of variation (per cent) of

strength of individual units of - 15 25 35

1 1.8 2.8 4.3

2 1.6 2.4 3.5 1

3 1.5 2.2 3.0

4 1.5 2.0 2.8

5 1.5 1.9 2.6

10 1.3 1.7 2.1

100 1.0 1.0 1.0

Note: For intermediate coefficients of variation use linear interpolation

on log-log plot of coefficient of variation against K

2

_

103
British Standard Code of Practice, CP 118 (1969)

"The Structural Use of Aluminium" [11]

No specific test is required in Section 5 (Testing) . The conditions

under which an acceptance test is appropriate are indicated and they are repeated below:

" (1) The structure is not amenable to calculation or calculation is deemed impracticable;

f2) Design methods other than those specifically referred

to in Section 4 (Design) of this code are used;

(3) There is doubt or disagreement as to whether the

structure has been designed in accordance with

Section 4 (Design) , or whether the quality of

material or workmanship is of the required standard."

There are two classes of tests described. The Static Acceptance

Test applies to structures or parts of structures which are not subject

to fluctuating loads likely to cause fatigue failure. The appropriate

load factors are given as well as the duration of loading, for each loading

increment. Prior to the actual test, it is recommended that a "settlingdown" of the test structure be accomplished through the application, for

15 minutes, of the combination of live and dead loading determined to cause the severest effect. The criterion for acceptance is that the structure

must sustain the test loads without excessive deformation and without

development of deleterious effect.

It is required that the recovery of deformation, measured 15 minutes

after removal of the test loads, be at least 95 percent, to prevent retesting

of the structure.

The second test, Fatigue Acceptance Test, is intended for structures

or parts of structures that may experience fatigue failure as a result

of fluctuating loads. A sequence of loading must be decided upon and

the test specimen should not fail until at least 30 repetitions of the

loading sequence have been executed.

Canadian Standards Association Standard A23. 3-1970 "Code

for the Design of Plain or Reinforced Concrete Structures" [15J

Section 4. Load Tests of Structures

Reliable load test data is recommended as a basis for demonstrating

the safety of either innovative or special systems of design or construction

of concrete structures or structural elements not directly covered by

the standard. A time limit for obtaining the data subsequent to placing

the concrete in the structure is imposed. The period should not be greater

than the minimum age at which the structure is to be put into service

or is assumed to possess the specified strength.

When there is reasonable doubt about the safety of an existing structure,

static load testing may be ordered (Clause 4.3) . This field testing of

the designated portion should not begin until the structure is at least

56 days old. Roof and floor components are explicitly mentioned in this

standard. The superimposed test load (Clause 4.4) equivalent to 0.3 times

the dead load plus 1.7 times the live load shall be applied without shock

to the structure and maintained for 24 hours. The standard spells out

criteria for evaluating the performance of floor or roof construction

when subjected to the prescribed proof test. The five criteria cited

104
in Clause 4.5.1 are almost identical to those stated in Section 20.4.6

of the ACI Code, 318-71 [2]

.

Canadian Standards Association, S157, "The Structural

Use of Aluminium in Buildings" [16]

Clause 4.3 provides for the establishment of structural adequacy

by direct load tests in lieu of approved design calculations. Clause

20 includes provisions for the testing of prototype structural units and

of portions of existing structures. A basic test load is established

for application to the prototype units which is equivalent to the design

load. The design load includes dead weight and impact allowances where

applicable

.

The loading sequence is comprised of three stages. First, the basic

test load is applied, the deflections are measured and compared with the

limits given in Clause 6. After removing the basic test load, the prototype

is reloaded to 1.4 times the basic test load. After removal of the factored

load the recovery of deflection shall be at least 90 percent. The prototype

is then to be subjected to a load of 1.75 times the basic test load without

failure

.

The stiffness characteristics of existing structures are evaluated

by loading the test portion of the structure with a required working load,

including impact allowances where applicable. The live load is removed

after the measured deflections are compared with the limits cited in

Clause 6. Then the test portion is reloaded to 1.5 times the total dead

plus live loading mentioned above. Subsequent to load removal the recovery

of deflection shall be at least 90 percent.

"A Standard for Testing Sheathing Materials for

Resistance to Racking" [41]

Federal Housing Administration (FHA) Technical Circular 12

This circular was issued October 5, 1949, by FHA in an effort to

establish a common method of evaluating the contribution to overall racking

resistance made by sheathing materials not specifically allowed by FHAMinimum Property Standards for One- and Two-Family Living Units (U.S. Dept.

of Housing and Urban Development, FHA No. 300) . The standard size, 8- ft by 8-ft, test panels were to be subjected to racking forces, applied

according to the recommendations given in NBS report BMS No. 2 [49] . It

is noted that the recommendations in BMS No. 2 were adopted as a Tentative

Standard by ASTM in 1947.

The established basis for acceptance of test panels was the observed

load-deflection relationship exhibited by a wood-framed wall sheathed

with horizontal wood boards and stiffened at the corner with diagonal

let-in bracing. Demonstration of comparable performance by other sheathing

materials as well as by many new types of panel construction is still

the requirement for gaining acceptability by FHA.

In addition to stipulating the critical load levels for the test

panels, the requirements for conditioning of the samples prior to testing

are described. Specimens are to be supplied in sufficient numbers to

allow for test in both a "dry" and a "wet" condition.

There have been no significant revisions to the content of this circular

since it came to existence but the document is currently under review

and should undergo some changes. The nature and extent of those changes are not known at this writing.

105
Uniform Building Code, 1973 Edition, [46]

Chapter 24 - Masonry, Section 2404 - Tests

This section states the load factors to be used in a flexural proof

test of masonry components in an existing structure. For evaluation purposes,

the superimposed static load shall be equal to two times the design live

load plus one-half of the dead load. This loading shall be maintained

for a period of 24 hours. There are no recommendations for the loading

apparatus, rate of loading or positioning of instruments for measuring

deflection. The maximum deflection measured at the end of the 24-hour

period is limited to the lesser of L/200 or L2/4000t (L is the span in

feet and t is the thickness or depth of the component in feet) . During

the 2 4 hours after the removal of the proof load the component must exhibit

a recovery of 75 percent of the maximum deflection.

Chapter 26 - Concrete, Section 2620 - Load Tests of Structures

The provisions in Section 2620 are identical to those given in Chapter

20 (Strength Evaluation of Existing Structures) of ACI Standard 318-71 [2]

.

5 . 2 Summary

An examination of table 5.5 will show that these requirements differ

in principle, scope and detail. Some requirements are intended for general

application while others are addressed to a specific material or type

of construction. The structural performance of horizontal concrete components

is the most widely covered subject in the listing. A majority of the

tests fall into the category of "acceptance" tests, but only the Australian

Standard CA65-1972 makes a distinction between the testing of existing

structures or components and that of prototype structures or components.

The distinction between existing and prototype structures is important

when one contemplates the significance of the test results from one specimen.

When testing an existing structure (or part of a structure) for proof

of compliance, a single proof load application is generally sufficient

for making a judgement on acceptance. However, the results obtained from

testing one specimen or a small sample, may be practically useless if

the variability of performance is high. It was also observed that the

specifications generally do not clearly distinguish between a "stiffness"

and a "strength" test.

6.0 Summary of the Report and Recommendations for Research

6.1 Summary of the Report

In order to establish the present state of knowledge and to identify

specific research needs various sources of information were consulted. A

collection of test reports, technical papers, symposium proceedings and

other publications were reviewed, leading to the preparation of thirty extensive abstracts for this report. The abstracts are intended to show the nature

and utility of the available publications. In addition to the literature

review, the activities of several voluntary standards associations concerned

with structural test methods were monitored. The current status of the activities of ASTM Committee E-6 (On Performance of Building Construction ) has

been discussed according to specific test method categories. The performance

requirements cited in various codes and standards were studied with respect

to test method requirements, implied or explicit, and a summary of that study

was included herein. The details of test methods used by NBS to evaluate

industrialized building components for the HUD Operation BREAKTHROUGH housing

program were compared with the details of methods contained in ASTM Standard

106
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E72-68, "Standard Methods of Conducting Strength Tests of Panels for Building

Construction". This was done to derive some recommendations intended to

make standard test methods more effective tools in evaluating the performance

of innovative housing systems.

6.1.1 Literature Review

It was found that there is a scarcity of research information contributing

directly to the development or revision of structural test methods . Most of

the testing of building components has been carried out to study the performance of a sample of components representative of a particular type of con- struction or to evaluate the performance of specimens relative to certain

requirements cited in codes or standards. Hence, the literature does not

contain substantial discussion or commentary on the merits or shortcomings

of the various test setups and procedures which are described. Such subjects

as the simulation of boundary conditions, the interpretation of test results

in terms of the predicted performance of the actual structure, the feasibility

of measuring critical deformations, the validity of certain test assumptions

and the proper method of loading are generally not discussed in any detail,

if at all.

The review showed that the early predominance of wood-framed and masonry

construction in housing influenced the objectives, scope and procedures of

the testing methods that were then used. As a result, there evolved several

test methods which eventually were widely accepted as standard test procedures

(e.g., ASTM E72) . Yet, the test methods reflected the influence of this prevailing background which on occasion rendered them inappropriate for application to innovations which were being introduced. The lack of subsequent test

method development resulted in housing technology that was not provided with

sufficient reliable data to predict rationally the performance of a wide

variety of structural concepts being used in houses and small industrial

buildings

.

Another deficiency made evident in the review of the literature, was the

lack of correlation between the results of full-scale building tests and those

of associated building components. Shortcomings such as these help to form

the bases for conclusions drawn about the research needed for component test

methods which can be effective in the evaluation of the structural attributes

of a building.

6.1.2 Activities of Voluntary Standards Associations

As new developments have evolved in construction practice, design

standards, manufacturing processes and material applications, most segments of

the structural engineering profession have acknowledged the need for updating

testing practice as it pertains to building components. Consequently, many

of the existing standard test methods are currently undergoing some degree of

revision. Just as significant an activity is the development of new standard

methods to satisfy previously unfulfilled evaluation requirements.

Because ASTM is the largest voluntary standards association and its Standard

E72-68, Standard Methods of Conducting Strength Tests of Panels for Building

Construction , is" the most widely used methodology in this country for testing

building components, this association's current activities are reported and

summarized in table 3.2.

It was found that ISO is the only international organization which is

authorized to develop and promulgate international standards. The scope of

this organizations activities encompasses the development of structural test

methods for building components. However, to the present time, the technical

committees have not produced any material germane to this area.

109
It was found that the standards pertaining to the structural performance

of building construction, as developed by the six foreign associations re- viewed, generally provide design load information and include recommended

design and construction practice. The exception to this generality is the

Japanese Standards Association (JSA) , which has issued standard test methods

for evaluating building components. These standards, while being similar in

format and scope to ASTM Standard E72-68, include a 10-point rating scale

which serves as a basis for comparison of the performance of two or more materials or types of construction. English versions of two typical JSA

Standards have been prepared for this report and are presented in Appendix

C.

To provide the reader with a capsule account of the state-of-the-art of

structural test methods for building components, table 6.1 has been prepared.

The information included in this table was derived from a review of the

publications of domestic, foreign and international standards associations

and of several domestic technical associations. It should be noted that the

scope of this investigation precluded coverage of test methods whose purpose

is to evaluate the performance of structural connections and joints. Due

to the relative significance of the joints and connections in building

systems a comprehensive study of test method availability and deficiency in

this area is warranted.

6.1.3 NBS Testing for HUD Operation BREAKTHROUGH Housing Program

The test methods employed by NBS to evaluate industrialized building

components for the HUD Operation BREAKTHROUGH Housing Program have been

compared with those contained in ASTM Standard E72. The main emphasis was placed on the deviations from and extensions of accepted standard methods

with a view toward improving these standards. The following list of items

summarizes the recommendations generated by this comparison exercise:

• develop a low-frequency repeated loading test in combination with

static loading to supplant static creep tests of extremely long duration.

• establish guidelines for the simulation of boundary conditions and

loading procedures (re: distribution, cycling and reversing) in com- pression, flexure and racking tests.

• improve instrumentation in order to minimize errors and expedite

observations

.

• establish guidelines for employing environmental conditioning of test

specimens

.

• use small-specimen, complementary tests for determining strength and

stiffness parameters unaffected by the size proportions of structural

test specimens.

• develop guidelines to correlate field and laboratory testing practices

for houses.

• conduct tests to study and better understand the interaction of building

components, joints and anchorages for improved correlation of component

evaluation with full-structure performance.

6.2 Recommendations for Research

On the basis of the literature review, the other sources of information

which are summarized in a general state-of-the-art by table 6.1 and the

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112
Operation BREAKTHROUGH testing, seven structural test categories for which basic

and development research is needed have been identified. The categories are divided into two groups: (1) those for which no standard test method has been

adopted and (2) those for which procedures have been accepted as a Standard by

ASTM Committee E-6 but are in need of substantial modifications.

The seven categories are listed below in accordance with these two

groupings. The order in which they occur is arbitrary and should not be

construed to be a recommended ranking of priorities. The brief discussion

presented for each category is intended to convey the nature and scope of the

problem.

6.2.1 Categories for which a Standard Test Method Exists but Needs Modification

6.2.1.1 Horizontal In-plane Loading on Shear Walls* - Static Racking Load

As a prerequisite to the development of an improved racking test, it is

necessary to gain insight into force distribution patterns and deformation

behavior by consulting existing information and supplementing this

information with data obtained from laboratory tests on prototype segments of

full-scale houses. To make the test method an effective evaluation tool, the

degree of correlation between the test results and the predicted lateral

response of the building must be determined.

6.2.1.2 Transverse Loading on Floors and Roofs - Short-duration, Static,

Uniform Load

There are modifications needed to improve the cost effectiveness of the

test and to make the test setup more easily adaptable to specimens of

different sizes. Section 4.2.3 of this report elaborates on one possible

alternative to the existing standard method.

6.2.1.3 Vertical Loading on Walls and Partitions - Short -duration, Static,

Compressive Loading

It is necessary to study such parameters as wall support and restraint

condition simulation, positioning of the compressive loading and location

of instruments. The testing of short specimens should be considered as

a recommended complement to full-height wall tests.

6.2.1.4 Local Transverse Loading on Walls, Partitions and Floors - Impact

Loading and Subsequent Short-duration Concentrated Loading

As a prerequisite to developing an improved test method, acceptable

limits of deflection under the concentrated load must be established. Model

U.S. codes do not state requirements for this serviceability consideration.

6.2.2 Categories for Which No Standard Test Method has been Adopted

6.2.2.1 Vertical Loading on Walls and Partitions - Simulation of Creep in

Compression

The need to evaluate the creep performance of new construction materials

and techniques warrants the development of a standard test method. It is

The expression "shear walls" refers to those walls which are subjected to

shear forces in their plane, as a result of horizontal forces. This distinction does not preclude the likelihood of other types of loading acting

concurrently

.

113
desirable to develop a relatively short-term test procedure that will produce

data which can be correlated with long-term performance that occurs in service.

The most important determination to be made is the required duration of test

loading to effect the desired correlation. Other factors to be considered

are: the type of conditioning required prior to and during the test; the amount

of eccentricity for the load; and the simulation of edge support and restraint

conditions

.

6.2.2.2 Transverse Loading on Floors and Roofs - Simulation of Creep in

Bending

It is desirable to develop a technique that in a relatively short term

will produce data which can be correlated with long-term performance that occurs in service. In Section 4.2.4 of this report there is a suggested

loading method that warrants further investigation. Other test parameters

must be studied as well.

6.2.2.3 Lateral Loading on Complete Prototype Houses - Racking Induced by

Cyclic Load Reversal and Rapid Repetition of One-Directional Loading

A laboratory testing procedure is needed for the purpose of evaluating

the load-cycle relationship for industrialized building prototypes. Of

primary interest is the structural integrity of joists, anchorages, and

other points of potential weakness. As a prerequisite to the test method,

it will be necessary to reconcile such test parameters as 1000 cycles of

repeated loading and 5_ cycles of load reversal with existing information" on earthquake and wind loading histories for houses.

114
APPENDIX A

BIBLIOGRAPHY

The following is an alphabetical listing of specific references noted

by number in the text and the appendices of the report.

1. ACI Standard 318-63 , "Building Code Requirements for Reinforced Concrete,"

American Concrete Institute.

2. ACI Standard 318-71 , "Building Code Requirements for Reinforced Concrete,"

American Concrete Institute.

3. American National Standard A119.1, 1974 , "Standard for Mobile Homes,"

American National Standards Institute

.

4. Anderson, L. 0., "Guides to Improved Framed Walls for Houses,"

Research Paper FPL 31 , Forest Products Laboratory, U.S. Department

of Agriculture, Madison, Wis., August 1965, 28 pp.

5. ASTM E72-68 , "Standard Methods of Conducting Strength Tests of Panels

for Building Construction, " American Society for Testing and

Materials.

6. Australian Standard CA65-1972 , "SAA Timber Engineering Code," Standards

Association of Australia.

7. Blume, J. A. and Proulx, J., "Shear in Grouted Brick Masonry Wall

Elements," Western Clay Products Association, San Francisco,

Calif., August 1968.

8. Boiler, K. H., "A Facility to Evaluate Three-Dimensional Performance

of House Modules," Research Note FPL-002 5 , Forest Products Laboratory,

U.S. Department of Agriculture, Madison, Wis., 1972.

9. British Standard Code of Practice, CP112 (1967) , "The Structural

Use of Timber," British Standards Institution

.

10. British Standard Code of Practice, CP114 (1957) , "The Structural

Use of Reinforced Concrete in Buildings," British Standards

Institution.

11. British Standard Code of Practice, CP118 (1969) , "The Structural

Use of Aluminium," British Standards Institution

.

12. Canadian Structural Design Manual 1970 , Supplement No. 4 to the National

Building Code of Canada, NRC No. 11530, National Research Council

of Canada, Ottawa, Canada.

13. Carter, C. and Smith, B. S., "Structural Behavior of Masonry Infilled

Frames Subjected to Racking Loads," Chapter 27 of Designing, Engineering and Construction with Masonry , Gulf Publishing Company,

Houston, Texas, 1969 , pp.'226-233.

14. Cousineau, R. D., "Testing of Large Diaphragms," ASTM Special Technical

Publication No. 282 , presented at ASTM Symposium on Methods

for Testing Building Construction, San Francisco, Calif., October

12-14, 1959.

15. CSA Standard A23.3-197Q "Code for the Design of Plain or Reinforced

Concrete Structure," Canadian Standards Association, Ottawa,

Canada

.

115
16. CSA Standard S157 , "The Structural Use of Aluminium in Buildings,"

Canadian Standards Association, Ottawa, Canada.

17. Diskin, S. H. , "Effect of Wind Pressure on the Racking Strength and

Stability of a One-Story, Gable-Roof Building of Sandwich Panel

Construction," Panelfab Technical Series Engineering Test Report

No. 113 , (Panelfab, Inc.), North Miami, Florida, April 196 8,

11 pp.

18. Dorey, D. B. and Shriever, W. R., "Structural Test of a House Under

Simulated Wind and Snow Loads," ASTM Special Technical Publication

No. 210 , presented at ASTM Symposium on Full-Scale Tests

of House Structures, Los Angeles, Calif., Sept. 18, 1956.

19. Dorey, D. B. and Schriever, "A Philosophy on Loading Tests," presented

at the 58th Annual Assembly of ASTM , Atlantic City, N. J., June

29, 1955.

20. Dryden, H. L., "Research on Building Materials and Structures for

Use in Low-Cost Housing," Nat. Bur. Stand. (U.S.), Building Materials

and Structures Report (BMS) 1 , June 1938.

21. Francis, A. J., Brown, W. B. and Aroni , S., "Full-Scale Tests of

Pre-Cast Multi-Story Flat Construction," ASTM Special Technical

Publication No. 210 , presented at ASTM Symposium on Full-Scale

Tests of House Structures, Los Angeles, Calif., Sept. 18, 1956.

22. Greene, W. E. et al, "Structural Tests for a Housing System Using

Sandwich Panels with Gypsum Board Facings," NTIS PB 214-336 , National Bureau of Standards (U.S.), Nov. 20, 1972, 75 pp.

23. Hendry, A. W. , "Shear Tests on Full-Scale Single-Story Brickwork

Structures Subjected to Pre-Compression , " (research conducted

at University of Edinburgh) , Paper presented at the RILEM

International Symposium on Methodology and Technique of Testing

Structures , Topic III, Bucharest, 1969, pp. 95-110.

24. Isenberg, M. W. , Barnoff, R. M. , and Mozingo, R. R., "The Racking

Resistance of Frame Wall Construction," a report prepared for

the Federal Housing Administration, (College of Engineering

and Architecture, The Pennsylvania State University), April

1963, 112 pp.

25. Lew, H. S., "The Effect of Impact Loadings on the Performance of

Wood Joist Subflooring Systems," National Bureau of Standards

(U.S.), Building Science Series 52 , May 1974, 28 pp.

26. Leyendecker, E. V. and Reichard, T. W. , "Test and Evaluation of the

Prefabricated Lewis Building and Its Components, Phase II,"

National Bureau of Standard (U.S.) Report No. 10 568 , unpublished

report prepared for Naval Civil Engineering Lab., Port Hueneme

,

Calif., April 1971, 66 pp.

27. Luttrell, L. D., "Strength and Behavior of Light-Gage Steel Shear

Diaphragms," Cornell Engineering Research Bulletin No. 6 7-1 , Cornell University, Ithaca, N. Y., July 1967, 41 pp.

28. Luxford, R. F. and Erickson, E. C. 0., "Rigidity and Strength of

Houses Built of plywood Stressed-Cover Panels," ASTM Special

Technical Publication No. 210 , presented at ASTM Symposium on Full-Scale Tests of House Structures, Los Angeles, Calif., Sept.

18, 1956.

116
29. Mason, W. R. , Rush, P. J. and Bruck, A. B., "Evaluation of a 40-

ft by 100-ft Frameless Straight-Sided Prefabricated Metal Utility

Building," Final Technical Memorandum M-050 , U.S. Naval Civil

Engineering Research and Evaluation Laboratory, Port Hueneme,

Calif. , April 1, 1952

.

30. Monk, C. B. Jr., "Transverse Strength of Masonry Walls," ASTM Special

Technical Publication No. 166 , presented at ASTM S /mposium on Methods of Testing Building Constructions, Chicago, 111., June

17-18, 1954.

31. National Building Code of Canada 1970 , NRC No. 11246, National Research

Council of Canada, Ottawa , Canada

.

32. Nilson, A. H., "Shear Diaphragms of Light Gage Steel", Journal of the

Structural Division, Vol. 86 ST 11, ASCE , Nov. 1960.

33. Pielert, J. H. et al, "Structural Evaluation of Steel-Faced Sandwich

Panels," NTIS PB 213240 , National Bureau of Standards (U.S.)

Revised Sept. 27, 197 2, 47 pp.

34 . Racking Strengths and Stiffnesses of Exterior and Interior Frame Wall

Constructions , Report No. CR-4 86, NAHB Research Foundation Inc.,

Rockville, Maryland, May 1971, 88 pp.

35. Ramstad, T., Reyes, V. D. and Espiloy, E. B. Jr., "Racking Resistance

of Timber Framed Walls," CIB Publication S56 , presented at CIB

International Symposium on Low-Rise Lightweight Constructions,

Budapest, Hungary, April 26-29, 1971.

36. Reichard, T. W. and Leyendecker, E. V., "Test and Evaluation of the

Prefabricated Lewis Building and Its Components, Phase I, Part

2," (Full-Scale Building Tests), National Bureau of Standards

(U.S.) Report No. 10 164 , unpublished report prepared for Naval

Civil Engineering Lab. , Port Hueneme, Calif., February 1970,

46 pp.

37. Reichard, T. W. et al, "Structural Tests on Housing Components of

Glass Fiber Reinforced Polyester Laminate," NTIS PB 221-183 , National Bureau of Standards (U.S.), April 1973, 90 pp.

38. Report on the Testing of Structures , Series No. 40, United Kingdom

Institution of Structural Engineers, London, September 1964,

15 pp.

39. Research Group of Systematic Methods for Selecting Building Materials,

"On the Systematic Method for Selecting Materials - Third Report - Standard Testing Methods," Report No. 56 , The Building Research

Institute, Ministry of Construction, Tokyo , Japan, January 1970,

179 pp.

40. Sinha, B. P., Maurenbrecher , A. H. P., and Hendry, A. W., "Model

and Full-Scale Tests on a Five-Story Cross-Wall Structure Under

Lateral Loading," Proceedings of the Second International Brick

Ma sonry Conference (SIBMAC) , Stoke-on-Trent, England, April

12-15, 1970, pp. 201-208.

41 . A Standard for Testing Sheathing Materials for Resistance to Racking , FHA Technical Circular No. 12 , Federal Housing Administration,

Washington, D. C, Oct., 1949.

117
42. Stillinger, J. R., "Lateral Tests on Full-Scale Lumber- and PlywoodSheathed Roof Diaphragms," ASTM Special Technical Publication

No. 166 , presented at ASTM Symposium on Methods of Testing Building

Constructions , Chicago, 111., June 17-18, 1954.

43. Structural Properties of Low-Cost House Construction , National Bureau

of Standards (U.S.), Letter Circular LC-502A, August 1937.

44. Thorburn, H. J. and Schriever, W. R., "Loading Tests on Full-Scale

House Roofs," ASTM Special Technical Publication No. 312, presented

at ASTM Symposium on Methods of Testing Building Constructions,

Washington, D. C. , November 15, 1960.

45. Tissell, John R. , "1966 —Horizontal Plywood Diaphragm Tests,"

American Plywood Association Laboratory Report 106 , American

Plywood Association, Tacoma, Washington , 4 8 pp

.

46. Uniform Building Code , 1973 Edition, International Conference of

Building Officials, Whittier, Calif.

47. Watstein, D. and Johnson, P. V., "Experimental Determination of Eccentricity of Floor Loads Applied to a Bearing Wall," National Bureau

of Standards (U.S.), Building Science Series 14 , June 196 8,

6 pp.

48. Whittemore, H. L . , Cotter, J. B., Stang, A. H. and Phelan, V. B.,

"Strength of Houses," National Bureau of Standards (U.S.),

Building Materials and Structures Report (BMS) 109 , April 1948,

133 pp.

49. Whittemore, H. L. and Stang, A. H. , "Methods of Determining the Structural

Properties of Low-Cost Constructions," National Bureau of Standards

(U.S.), Building Materials and Structures Report (BMS) 2 , August

1938, 18 pp.

50. The Wood-Frame House as a Structural Unit , Technical Report No. 5,

National Forest Products Association, Washington, D. C., 1965.

51. Yancey, C. W. and Somes, N. F., "Structural Tests of a Wood Framed

Housing Module," COM 73-10860 , National Bureau of Standards

(U.S.), March 26, 1973, 101 pp.

52. Yokel, F. Y., "Study of the Local Resistance of Conventional Plywood

Subflooring to Concentrated Load," National Bureau of Standards

(U.S.) Building Science Series 53 , May 1974, 36 pp.

53. Yokel, F. Y. , Hsi, G. and Somes, N. F., "Full Scale Test on a TwoStory House Subjected to Lateral Load," National Bureau of Standards

(U.S.), Building Science Series 44 , March 1973, 23 pp.

118
APPENDIX B - Air Bag Contact Area - Flexure Tests

In section 3.2.3.3 there are three alternative ways of accounting

for the fact that under some circumstances the air bag used in a flexural

test does not load the entire surface of the test panel. Described herein

is the second of those three ways; this procedure is based on the original

geometry of the specimen and the air bag. Figure B.l schematically shows

the specimen and the air bag in their unloaded (i.e. original and loaded

positions. The symbols shown in this figure are subsequently explained

and used in performing the necessary calculations.

Figure B.2 is a schematic representation of the third way in which to

account for the stated condition. The actual uniform load imposed on the

specimen can be determined by measuring the reaction at each support with

a set of load cells sandwiched between two reaction beams.

119
PLAN VIEW- FLEXURE TEST

REACTION BEAMS

LOAD CELL

A

ROLLER SUPPORT

TIE-DOWN ROD

LABORATORY

FLOOR

SECTION B-B

Figure B.2 - Section of flexural test setup at reaction beams.

120
Calculation of Contact Area

Symbols

L

u

= transverse length of air bag contact at the centerline when the specimen

is unloaded .

L

L

= transverse length of air bag contact at the centerline when the specimen

is loaded .

r u

= edge radius of air bag at the centerline when the specimen is unloaded .

rL

= edge radius of air bag at the centerline when the specimen is loaded.

c = circumference of air bag

t = edge distance of the unloaded specimen.

t = edge distance of the loaded specimen.

Using the plan view and section A-A in fig. B.l and the symbols listed

above, several geometric relationships can. be derived. It is assumed that

the circumference remains constant throughout the longitudinal length of the

air bag.

2L + 2irrT = c [B.l]

2L + 2irr = c [B.2] u u

Eliminating c from the two equations and transposing terms yields the

following relationship at the centerline.

LT = L - tt (r T - r ) [B. 3] L u L u

Since the transverse deflection of the specimen follows a circular arc,

with the maximum deflection (i.e. the distance between the chord and the arc)

occurring at midspan, the edge profile of the air bag's contact area against

the specimen will also follow a circular arc of large radius. Assuming that

the edge profile of the air bag's contact area can be approximated by a straight

line, as shown in the plan view of figure B.l, an expression can be derived

for the average transverse length of air bag contact, LaVg

:

L = L = 1 (rT - r ) [B.4]

avg u 2 L u

L can be calculated from equation B.2 as follows:

u

L = % = ur [B.5] u 2 u

Using equations B.4 and B.5, the following example is presented:

Given: c = 12 in, r = 1.0 in u

L = 60 = tt (1) = 56. 84 in. u

121
Table B.l - AVERAGE TRANSVERSE LENGTH REDUCTION FOR AIR BAG CONTACT

rL

L ave Average Percent of Midspan

(eqn. B.4) Length Reduction Deflection

(in) (in) 100 (L - L )/L

u ave ' u

(r_ - r ) L u 1.25 56 .46 0.7 0.25

1.50 56 .06 1.40 0.50

1.75 55.66 2.07 0.75

2 .00 55 .27 2 .76 1.00

2.25 54 .88 3.45 1.25

3.00 53.70 5.52 2 .00

4 .00 52 .13 8 .28 3.00

6 .00 48.99 13.81 5 .00

10.00 42.71 24 .86 9.00

15 .00 84.86 38.66 14 .00

122
APPENDIX C - Translation of Two Japanese Standard Test Methods

The two standard test methods presented on the following pages were

selected as being typical, in format and content, of a series of standard

test methods included in [39] . Among the other structural performance tests

included in this reference are the following titles: 1) "Standard Method of

Test for Impact Strength by Steel Ball Pendulum System", 2) "Standard Method

of Test for Bearing Resistance in Dynamic Pressure" and 3) "Standard Method

of Test for Bearing Resistance in Compression by Concentrated Load".

These test methods are to be used in evaluating specific building components against various structural performance requirements. It should be

noted that the designated performance requirements are stated at the beginning of the test method. After following the details of the test procedure,

the user is supplied with some guidelines for quantitatively assessing the

resistance of the test specimens and for establishing a rating of the components performance.

123
(1)

Name of Test

Method

Performance

Requirements

601T-2 "Test of Method of Loading Resistance

(Test Method of Pressure Resistance for

Vertical Loading Normal to Surface)

louij io dk saie agaxnsc live ioao ana snow loading

(3)

Test

To find the degree of safety against

uniformly distributee loading which is

acting on the horizontal members,

subjected to live and snow loading.

(4)

Test Specimens

1. Type: Building Element and Joint - Various

types of panels and joints

2. Dimension: Shall be the smallest unit of

the structure, but it should

include the entire span length

3. Quantity: Three specimens

(5)

PR

0

ED

U

R

E

S

(5-1)

Summary

In principle this should be a uniformly distributed load test. However, if deemed appropriate, many equally spaced concentrated loads or a single concentrated load at the center

may be applied to the Building element.

(5-2)

Test Setup

1. Test setup for uniformly distributed loading

(Refer to Figs. 1, 2, and 3 and photo. 1)

2 . Test setup for many concentrated points of

loading

3. Test setup for compression (airbag) loading

4 . Instruments for Deflection Measurement

(e.g., Dial Gages)

(5-3)

Conditioning

Prior to Test

Moisture Content — For air-dried specimens

the temperature-moisture

condition is class 2.

(5-4)

Details of Test

Method

1. Uniformly distributed load shall be used —

In principle, only both ends are to be

supported, although in real structure all

four edges may be supported. Load increments are as follows: 50, 100, 150, 200, 300,

400, 500, 1000, 1500 kg/m2 2. Increase load gradually; load at a rate of

about 1 kg/5 sec, and at each load level

maintain load for 10 minutes. Then release

load to zero. Repeat process at next highest load. (Sketch on next page)

3. The test shall be conducted until failure or until severe displacement occurs.

(Severe displacement in actual practice

would be the point beyond which the deflection is irrecoverable.)

4. If necessary, perform the same steps again.

124
(6)

Method of

Evaluation

To determine the least loading capacity, use one of the following three:

1. Two loading steps before the level at

which failure or severe displacement

occurs

.

2. Loading step at which deflection reaches

supported span divided by 150 (L/150).

3. The loading step (in the step by step

loading procedure) at which the surface

of the Bldg. Element will fail.

Table 1 - Grading of Loading (Perpendicular to

the Surface) Resistance

Grade 0 1 2 3 4 5 Unit Pressure f (kg./m2

)

0 1(

I

K) 1

1

50 2

I

DO - 300

1 1

(Table 1 - cont.)

Grade 5 6 7 8 9 Unit Pressure 4E (kg./m 2

)

>0 71 )0 10 DO 15 DO

(7)

Test

Results

Indicate the loading capacity in units of kg/m2 which was determined by above techniques

(8)

Remarks

No remarks

125
Commentary on Test Method of Loading Resistance (601 T-2)

Live load capacity so determined is usually used for structural calculations in satisfying building code requirements. Normally the value

ranges between 60 and 550 kg/m z

. In [501] live loading and snow loading,

quantitative grading is divided into ten levels from 50-1500 kg/m 2

. Test Setup for Uniformly Distributed Loading

By filling the compressed air into several air bags, the uniformly

distributed load is applied. The equipment used in the building research

lab. is shown in Figures 1, 2 and 3 and in Photograph 1.

Loading Technique

Repeat the loading for each loading step and continue until bending

failure or shear failure occurs. But, if increase of deformation is

large and no increase of load is possible, in this case it is not

necessary to continue increasing the loading until failure.

Evaluation

Following the three evaluation methods in section (6), bending strength

performance of the Bldg. Element can be obtained.

126
C. L.

i tr- a (ioo ^200)

Figure 2 - Section Along the Span (for the case of two edges supported)

127
Photograph 1 - Test Setup for Uniformly Distributed Loading
(1)

Name of the

Test Method

608T-2 Test Method for Bending Resistance to

Local Concentrated Load

(2)

Performance

Requirements

[507] To be safe against locally concentrated

loading

[708] Locally concentrated compression

(3)

Purpose of

Test

To find the characteristics of a Bldg. Element

and its surface material under the locally

concentrated loading, simulating actual design

conditions

.

(4)

Test

Specimens

1. Type: Various kinds of Bldg. Elements

2. Dimension: The dimensions shall conform

to the dimen. of the actual

structure. Typically the long- er side is approx. 90-250 cm and the shorter side is approx.

60-120 cm.

3. Quantity: More than two samples or such

quantity that will yield two

test results.

(5)

P

R

0

C

ED

U

R

E

S

(5-1)

Summary

Test specimen shall be supported at both ends

by horizontal line supports. Center of con- centrated load is to be applied perpendicular

to the upper surface of test specimen at its

geometric center. Measure the change in deformation of the Bldg. Element as well as the

deformation of the surface of the Bldg. Element.

(5-2)

Test

Setup

1. The panel bending strength test machine —

to have a maximum capacity of more than 1 ton

.

2. Load is applied to the surface of the test

specimen through either a 10 cm diameter

disc or a 10 cm square block. A 10 mm

' thick hard rubber pad is placed between

the surface of the specimen and the disc

or block. The method of attaching the above

assembly to the panel bending strength

test machine depends on the machine's con- struction . 3. Dial gage or displacement detector with

automatic recorder.

4. Load cell and automatic recorder.

(5-3)

Conditioning

Prior to Test

Store the test specimen more than 7 days under

constant temperature and relative humidity of

•JS H _ OJTS'T'^ «J1U anrl 4^1 *±J —— Ro DS &T> rocnor'tiimlu f IcSpcCtlVS ly ,

129
(5-4)

Details of Test

Method

Span Length - the span length depends on the span (L) in the actual design conditions

but it is usually about 180 cm in standard

size. Condition of support fixity is dependent on actual design.

Location of the Loading - Principally, one point in the center of the test specimen

such as in Figure 1.

Location of the Displ . Meas. Points - Deformations to be measured at least at

the following three locations shown in

Figure 1.

(1) Edge Defl. at 1/4 span (6 l7 6 2 , 6 3f 5 4 ) (2) Edge Defl. at Center Span (6 5 & 6 6 ) (3) At Center of Specimen (6 7 ) Loading Method - Increase load until failure occurs in the Bldg. Element or in the surface

material or until load reaches 1 ton. In case the displacement is meas. by dial gages,

the loading rate is to be based on the gage

which shows the most movement. And also the

loading rate should be based upon the behavior of the specimen. When using automatic recorder the average loading rate is

about 100 kg/min

.

(6)

Method of

Evaluat ion

When failure occurs before the center deflection

at mid-span (6 7 ), reaches L/150 the local bending resistance is expressed by 2/3 of the loading

at which failure occurred. In other case, the

bending resistance is expressed for the point

at which 5 7 reaches L/150 and then the grading

is based on Table 1. Table 1 - Grading of Local Bending Strength

1 Grade 0 3 4 5 6 7 8 9 Load (kg) 1 •U 2.1 4

• .5

j .0 21 .5 4 5 1(

i 0 215 o

(7)

Test

Results

1. Detailed information of test specimen;

2. Location of load and displ. meas. points;

3. Load-deflection curve;

4. Failure load (kg)

;

5. Local load bending strength (kg) and grade.

(8)

Remarks

When there is a displacement at the top of

support, measure this displ. along the support

and take it into account. The original draft

of this method was a Japanese Industrial Standard for local load testing of Bldg. Elements.

130
Location of Loading and Observation

Points of Displacement

131
Commentary on Test Method for Locally Concentrated

Loading Bending Strength (608 T-2)

Locally Concentrated Loading

Here, the locally concentrated loading, applied to a relatively small

area of the surface, acts perpendicular to the surface of the sample.

As such, this concentrated loading can be applied to floors as well as to walls. In the case of loading on the floor of a building, the loading

is caused by human occupancy and by household goods. Sources of localized loading include such items as spiked heels, desk legs and chair legs.

Although the following items are not defined as loading, the local

pressure due to humans leaning on to objects is herein considered to be

local loading.

Local Load Bending

The structure experiences bending when local loading is applied. This

particular loading state is called local load bending. The local

bending of surface material should be considered in relation to the

path of loading. Such a case is local loading action on the surface

material of a panel made of cellular structures with voids. However,

the test method presented herein considers only the local bending

strength of surface material, the Local Compression Test Method (test

no. 608T-1) should be consulted.

Loading Method

(a) Loading Assembly

In the Local Compression Test method the leg of a chair or a desk is

simulated by a 25 mm-diameter sphere attached to the bottom of the

assembly. However, this assembly is not suitable for the evaluation

of bending resistance of a building element . It is necessary to provide for the loading assembly to contact EEe surface of the specimen

over a certain area. Photograph 1 shows an example of such an arrangement. A wooden block attachment with surface dimensions of 10 cm x 10

cm, with a 10 mm-thick hard rubber pad on the entire contact surface,

of the wooden block, is reinforced by a steel band which is wrapped

around it. This assembly is usually employed with the panel bending

test machine (described in another test method) . But, it can also be

applied to the Local Concentrated Loading Bending Test. An improved

steel assembly is shown in figure 2. The part which contacts the specimen is a steel disc 10 cm in diameter and there is a steel sphere

between the disc (see Attachment B in figure 2) and the supporting bar

of the panel bending machine.

(b) Span Between Supports and Location of Loading Points

The test span should be the same as that of the real structure. The test

span should be the same as the span of the main members of the building

element or multiplies of it.

Load should be applied at tne center of the test specimen. Usual

Panel Bending Test Machine can be used for this purpose. This type of

testing machine can present problems when two-point loading across the

width of the specimen is assumed to simulate the line loading on the

specimen in that direction.

132
Figure 2 - An Example of Attachment for the Local Loading

Bending Test (Units in mm)

133
NBS-1 14A (REV. 7-731

U.S. DEPT. OF COMM. 1, |n:HU< A ! ION OK REPOR 1 NO. 2. Gov't Accession BIBLIOGRAPHIC DATA No. sheet NBS BSS- 58

4. TITLE AND SUBTITLE

State-of-the-Art of Structural Test Methods for Walls, Floors, Roofs and Complete Buildings

5. Publication Date November 1974

6. Performing Organization ("ode

7. AUTHOR(S)

C.W.C. Yancey and L.E. Cattaneo

8. Performing Organ. Report No.

9 l->F ]i ] OW MIMt , OR ( , A \M / A !' lOM VAMK AWH Anni/l-s\< NATIONAL BUREAU OF STANDARDS DEPARTMENT OF COMMERCE

WASHINGTON, D.C. 20234

IU. rrojfct/ I ask / Work Un 1 1 INo. 4618491

11. Contract/Grant No.

12. Sponsoring Organization N ii m c and Complete Address (S tr&c t , Ci ty , 5 t3t& , IP_)

Office of Policy Development and Research Department of Housing and Urban Development

Washington, D. C. 20410

13. Type of Report & Period Covered

Final

14. Sponsoring Agency Code

is. supplementary notes

16. ABSTRACT (A 200-word or less tactual summary of most significant information. If document includes a significant bibliography or literature survey, mention it here.) MbAc npdla r*+

L r\T Ul a

a fCUllipi * /"imrvrohdn cllcl loc iwo 1 Vtr rQCQar^h IfcJocIdlLM nrc\nr3 piuyialllm ffinrornQrt LUllLclllcU uiitn Willi thQ lllc ctni^tiirjll oLIULlUlal ioctinn Icollliy c\T Ul hnUUIIUIliy i In i nn LUII c nmnnno ipUl ICIntc 1 lo rnn^n^toH , CUIlUULlcU

for the U.S. Department of Housing and Urban Development (HUD), a search for information was conducted. This search was undertaken in order to document existing information pertaining to structural testing of wall, floor and

roof assemblies. Various information sources were consulted to trace the evolution of structural testing of building construction from the 1930's to the present time. This task was a prerequisite to defining the state-of-the-art and to identifying the test areas requiring fundamental research. Based on information obtained from a review of the literature and from liaison with committees concerned with the development and revision of voluntary standards, it was found that there is a dearth of research information contributing directly to the development of test methods. Most of the research conducted on building components has been carried out either to observe the behavior of a sample of a particular type of construction or to evaluate the performance of a specimen against some performance requirements. However, helpful inferences can be made on the basis of some of the documentation, especially that contained in reports of full-scale tests on housing. As a result of comparing the test methods used by the National Bureau of Standards in HUD project Operation BREAK- THROUGH with American Society for Testing and Materials (ASTM) Standard methods, several recommendations have been made by the authors for improving present structural test practice. An up-to-date status report of voluntary test standards activities (in the U.S.) was prepared through verbal and

written communication with members of the technical subcommittees of ASTM Committee E-6 on Performance of

Building Construction.

17. KEY WORDS (six to twelve entries; alphabetical order; capitalize only the first letter of the first key word unless a proper name; separated by semicolons)

Building construction; complete buildings; floors; roofs, standardization; test methods; walls.

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