Bureau of Standards

E-01 Admin. B!dg.

[| 7 1969

BUILDING SCIENCE SERIES

aken

Techniques for the Survey and

Evaluation of Live Floor Loads

And Fire Loads in Modern

Office Buildings

U.S. DEPARTMENT OF COMMERCE

National Bureau of Standards
Announcing—The Building Science Series

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UNITED STATES DEPARTMENT OF COMMERCE • C. R. Smith, Secretary

NATIONAL BUREAU OF STANDARDS , • A. V. Astin, Director

Techniques for the Survey and Evaluation of Live Floor

Loads and Fire Loads in Modern Office Buildings

JV O. Bryson and D. Gross

Building Research Division

Institute for Applied Technology

National Bureau of Standards

Washington, D.C.

Building Science Series 16

Issued December 1968

For sale bv the Superintendent of Documents, U.S. Government Printing Oflice Washington D.C. 20402—Price 10 cents
Contents

Page

1. Introduction 1

2. General approach 2

3. Survey techniques and procedures 2

3.1. General 2

3.2. Definition of survey loads 2

3.3. Data records and classification 3

3.4. Survey team 5

3.5. Equipment 6

3.6. Survey procedure 6

3.7. Measurement of contents in selected items 8

4. Computer program for data analysis 8

5. Application of techniques—initial survey results 9

6. Discussion 27

6.1. Review of initial work 27

7. Future work 27

8 Selected references 27

Appendix A. Description of coded records 28

Appendix B. Computer program for live floor loads and fire loads 29
Techniques for the Survey and Evaluation of Live

Floor Loads and Fire Loads in Modern Office Buildings

J. O. Bryson and D. Gross

The procedures and techniques developed for measuring and evaluating the

live floor loads and fire loads in modern office buildings are summarized. The main

features of a computer program for analyzing the data are outlined. This pro- gram provides a tabulation of the data, some statistical properties, and selected graphical relationships between the measured loads and the characteristics and

usage of the structure. A rationale is developed which is intended to achieve the

ultimate goal—easier and less expensive means of surveying live loads in buildings

and their combustible content. Two office buildings have been surveyed in a pilot evaluation of the survey

techniques—the National Bureau of Standards Administration Building in Gaithersburg, Maryland, and the U. S. Civil Service Commission Building in downtown

Washington, D. C. Typical results are presented to illustrate the computer output.

Key Words: Fire loads, live floor loads, loads survey techniques, occupancy loads.

1. Introduction

A survey of loads in modern office buildings was initiated in February 1967 as the first step

in a broad program developed at the National

Bureau of Standards to scientifically study existing loads on structures. The first phase of

the program is concerned with measurement of

actual live floor loads and fire loads. The central

objective of the first part of this program is to develop survey techniques and procedures for

easier and less expensive means of surveying

loads on buildings, and to develop evaluative

measures, in line with present day technology

of scientific methods, for determining the nature of the loads in relation to the characteristics of the load items and in relation to the

geometry of the structure. In the structural design of a building the

engineer has three principal concerns, the

analysis of the structural system, the strength

of the materials in the system, and the loads to which the structure will be subjected. Extensive scientific knowledge exists on the characteristics of structural systems and the properties of materials due to broad and continuing

research in these areas. In contrast to this, very

little is known about the actual loads that are

applied to structures. The few studies that have

been made in the past [1-7]* have not been of

sufficient scope to provide comprehensive data

that could serve as a scientific basis for establishing design criteria. Comprehensive data on

actual loadings could result in a reduction of

design loads specified in codes and standards.

* Figures in brackets indicate the literature references on

page

Even where higher design loads are shown to be needed, gains in economy could still be realized, since more accurate information about

loads could justify a reduction in safety factors.

With respect to fire loads, there is a need to update and to extend the survey of combustible

contents of buildings made approximately 30

years ago [8, 9]. Although significant changes

have occurred in the type of building construction and the nature of the occupancy load, fire protection measures currently required in

building construction are based on the assumption of the same fire loads as previously observed.

The field studies carried out in the past were

of necessity limited in scope; consequently, a

relatively small sample size of data was obtained from which to draw conclusions about

the vast population of buildings. The main

purpose of this current work is to develop, for

the first time, a sufficiently large bank of comprehensive data that can be used to predict,

with measured accuracy, the live floor loads

and fire loads for various building occupancy

types in this country.

This paper summarizes the procedures and

techniques developed to date for the weighing

and classification of items and for the analysis

of live floor loads and fire loads in modern office buildings. As an illustration, the loads measured within two modern Government-owned

office buildings in the Washington, D. C, area

are included. It is planned that these results

will eventually form part of a large collection

of data from surveys of buildings located in

the major regions across the country.

1
2. General Approach

The first phase of the survey was considered

to be a pilot study which would provide an

opportunity to perfect the techniques and sur- vey procedures and to serve as a training exercise for survey crews. A principal objective was to accumulate data and experience which

could lead to easier and less expensive ways of

surveying loads in buildings. For example, it may be possible to classify furniture into a number of types and sizes, and its contents by

volume, either in cubic feet or percent of ca- pacity, so that little or no weighing will be

necessary to obtain weight estimates in the

future.

The survey is presently being limited to modern buildings, i.e., buildings erected within the \$n nast 10 years. Since the occupancy load is likely

to change appreciably over the years, supple-^

mentary load data on older buildings may alsoj

be needed. One consideration in the choice fori the initial survey was the availability of then building for resurveys in future years. Accordingly, the National Bureau of Standards'

Administration Building and other Govern-'

1 ment buildings in the Washington, D. C, area

represent logical buildings for possible periodic

load surveys.

3. Survey Techniques and Procedures

3.1. General

The techniques and procedures for measuring and recording the data from occupancy

loads were developed in accordance with plans

established for a broad NBS program designed

to evaluate existing live floor loads and fire loads in office buildings. The load data obtained

with the techniques used provide singular source type input information for both live

load and fire load data analysis. The actual sur- vey work for this preliminary phase of the

study represents the first step of a program in

which statistical analysis of the data will serve

as the foundation for succeeding steps leading

to statistical sampling techniques.

In the two buildings surveyed, the weights

and the approximate horizontal locations of all the items in each room were determined and

recorded. Floor plans of the buildings were

used to note room layouts and locations and were corrected, if necessary, to reflect actual

conditions. These plans were maintained with

other records for the investigation. All data were coded and recorded in a format consistent

with an appropriate computer program for

automatic data processing. In each case the

room was divided into nine sections and defined by three strips in each direction parallel

to the wall and perpendicular to each other.

The width of the center strip was one-half the

distance between the walls that it parallels and

the strips to either side were one-quarter of

the distance between the walls. These strips

then correspond to the midstrips and column

strips of a two way flat slab where the boundaries of the room serve as the column line. The

overlapping of the strips in the two directions,

form a checkered pattern of areas which provides a general location scheme (see fig. 1).

3.2. Definition of Survey Loads

The live loads in the survey include the oc- cupants, the floor covering, movable partitions,

1

1 14 I 01 I 12

04 ! 00 02

34 ; 03 23

TI 1/4

1/2

1/4

1/2 1/4

Code number is related to an actual direction, e.g.:

00 = Central 03 = South

01 - North 34 = Southwest

12 = Northeast 04 = West

02 = East 14 . Northwest

23 = Southeast

Figure 1. General scheme for locating items within the room.

all furniture and equipment and their contents,

except built-in items. Built-in items are those

whose shape and size were designed as an

integral part of the structure and were formed

during construction of the buildings. The furniture and equipment brought in for the service of the occupants after the construction of

the building (including those which are placed

in recesses and/or tied down in the structure)

2
were not considered built-in and their weights were determined (or estimated).

) The fire load falls into two general cate- gories—"movable contents" and "interior fin- ish." Movable contents include combustible

furniture, equipment, and goods, and the combustible contents within and on top of items

i including metal furniture and containers. Also

; included were floor coverings not securely

fastened to the floor. The remainder of the

J combustible load associated with rooms and

1 buildings consisted of the "interior finish fire load" and comprised walls, ceilings, floors (including permanently installed wall-to-wall car- peting and finish flooring) , drapery, wall hangings, partitions, door and window trim, and

built-in fixtures (e.g., bookcases). Where such

i items could not be weighed, their weights were

J estimated from thickness and area. As an aid

i in estimating, a "combustible trim list" was

j prepared containing weights for typical sizes

i of doors, windows, molding, and lumber. A

"building materials list" was also prepared

| which provided a rapid means for converting

measured or estimated thicknesses of typical

i interior finish materials into equivalent unit

i weights of combustibles. For common doors,

one-half the total weight was assigned to the

respective room on each side. All weights were converted to equivalent

weights of combustibles having a calorific value

of 8000 Btu/lb. Tables of calorific values of materials can be found in standard reference

sources. A list of heat release values for building materials under "fire" conditions is also

available [10] and is particularly useful for

metals and materials of low combustibility.

The movable contents fire load has been further divided into separate totals of "free" movable contents and "adjusted" movable contents. The "free" movable contents fire load represents materials readily available for combustion, and includes combustible furniture and

their combustible contents, combustibles on top

of steel desks and tables, and those associated

with miscellaneous and "free contents" items.

It excludes combustibles within enclosed steel furniture, such as shelving, filing cabinets,

desks, and safes. The "adjusted" movable contents fire load represents the "free" movable

contents fire load plus the "effective" contribution of the combustible contents of steel furniture, computed in accordance with the "derating" values in table 1, based on BMS 92. These

values have been (customarily) assumed to depend only on the relative portion of combustibles within a room which are located in

steel furniture. However, the degree of compaction within individual file cabinets, shelving, desk drawers, etc., may also modify its effective contribution.

Estimates of the volume of combustible contents on top, rather than measured weights,

Table 1. De-rating factors to determine combustible contents

of steel fiirniture

(Based* on Table 6, BMS 92)

Part of combustibles in containers

Container One-half More

Less tha n to three- than

one-half fourths three- fourths % % %

Enclosed steel shelving.. 60 50 25

Steel file cabinets and desks 40 20 10 Insulated (1 hr fire-rated files &

safes) - . . 0 0 0

were used to determine the "free" movable

contents portion of desks and tables. In con- verting the volume estimate to weight, a density of 40 lb/ft 3 was assumed. A volume esti- mate was made of the contents of desks, cabinets, and bookcases, and note made of the nature of its contents (100% books, 100% paper

or mixed). For desks and cabinets, an estimate was also made of the contents volume, ex- pressed as a percent of its capacity. With these

measurements and estimates, the "derating"

factors for steel furniture were applied, and

data were assembled for correlating the combustible weight of contents (paper or books)

with the capacity of standard desks and cabi- nets (by percent) and of bookcases (by volume). For miscellaneous steel furniture, the

empty weight was unknown and volume esti- mates provided a means for estimating the

weight of combustible contents.

3.3. Data Records and Classification

The survey data included code input designations for floor level, room number, room use, overall dimensions, number of assigned personnel and sex, item weight, location, and description, and a description and measurement of the

contents in items. The locations of the items in a room were recorded with respect to the nine

sections defined for room area. In addition,

surface finish and the weights of trim and

floor covering were recorded. A typical log

sheet with entries is shown in figure 2 and a schematic representation of the items listed on

the log sheet is seen in figure 2A. From this

log sheet, a single "room" card and the re- quired number of "item" cards were keypunched directly without further conditioning

or special handling. Rooms were designated in one of the following use categories: office,

laboratory, storage, conference room, lounge,

lobby (or reception room), dining room, li- brary, file room, and "other." The length,

width, and height of the room were recorded

to the nearest foot, with an area reduction en3
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0520 0400 0001 0102

Figure 2-A. Schematic representation of items listed on typical log sheet

(figure 2).

try in square feet to allow for recess areas. Each item was assigned a four-digit numeric code and was classified into one of six

categories: desks (0100 series), tables (0200),

cabinets (0300), chairs (0400), bookcases

i (0500), or miscellaneous (0001 to 0099). A

reference catalog of the basic "standard" items

of office furnishings was prepared prior to starting the survey, and was augmented with

new items encountered in the survey. The catalog entry included a photograph of the item,

the assigned code number, dimensions, composition, empty weight, and other pertinent

descriptive information. A detailed description

of the coded records is given in Appendix A.

3.4. Survey Team

A team of four men performed the survey

work. The team leader defined the items, re- corded the data, and took photographs. Two

men handled the weighing equipment and did

the measuring of dimensions. The fourth man

estimated combustible contents.

5
3.5. Equipment

The weighings were made with the use of

electronic load platforms. These devices are

rectangular plates that were designed to indi- cate the load that is applied normal to its sur- face within a specified area (see fig. 3). Two

load platforms were used in the survey. One

platform was 26-in long by 14-in wide with a 20xl4-in loading area and the other platform

was 32-in long by 14-in wide with a 26 X 14-in

loading area. Both platforms were approximately 1-in in height. Two units of item handling equipment were used for lifting room

furnishings. Both units were standard equipment purchased from commercial sources. For

both units, load indications were linear with

load over the load range, and accuracy as read was estimated to be within 2 percent. One unit was a desk handler, figure 4, and the other was

Figure 4. Commercial type desk handler with modified

central braces to support load platform. a hydraulic forklift, figure 5. Figure 6 shows

views of these units with load platforms positioned on them so that weighings were made

in conjunction with the lifting operation. A

list of all the equipment and supplies for the

survey operation is given below and a view is presented in figure 7. List of Equipment and Supplies for Survey

Team

1. Hydraulic fork truck

2. Desk handler

Figure 5. Forklift actuated through hydraulic pump

system.

3. 2 steel plates

4. 2 load platforms

5. 1 readout box

6. Assortment of 2X4-in wood bearing strips

(18 in, 24 in, 48 in, and 2 72-in-long

strips)

7. Hand truck

8. Chain and padlock

9. Large clipboard

10. Survey sheets and envelopes

11. Red, blue, green pens (ball point and felt tip)

12. 12 and 50 ft tapes

13. Slide rule

14. Camera, film, flashbulbs (Polaroid, color)

15. Floor plans of buildings

16. Tool kit—pliers, screwdriver, solder, etc. 17. Calibrating weights

3.6. Survey Procedure

[ The order of floor levels in the survey was

random; however, for the most part rooms on;

a given floor were surveyed in numerical order j according to room number.

Before starting the survey, the survey team 3 was briefed and drilled on the techniques and

6
Figure 6. Top: Desk handler with load platform posi- tioned for use. Bottom: Forklift with load platform

inserted across the arms and a flat metal plate on top.

procedures to be followed. The manner of coding and recording the data was thoroughly

explained and discussed. The team leader was

given an item code list and an instruction sheet

for location code.

Just prior to surveying a room, the team

leader recorded the floor level, the room number, room use (e.g., office, storage, etc.), and

the number of assigned personnel—indicating

sex. The two assistants were then called into

the room with the team leader to take measure- ments in the room. The weighing equipment was left outside the room while measurements

of the room were being made. The dimensions

of the room were measured by the two as- sistants and recorded on the record form by

the team leader. The equipment for weighing was then brought in and the items in the room

weighed in an order determined by the team

leader. It was found that in a few cases an

item and its contents could not be weighed

together, as in the case of tall or fragile items

that were not designed to be moved when full

;

therefore, in these cases contents were weighed

separately from the item. For each item, a

separate weight of the noncombustible portion

of the contents was determined and recorded

by the team leader. For items that could not

be weighed either because of size, weight, or

sensitivity or because they were tied down, the

weights were obtained from the manufacturers

or were estimated. The types of surface finish

and their thickness were determined by the

team leader, who used a material type listing

to select the appropriate unit weight range in

terms of combustibles.

All items were weighed using the load platform and the item handling unit, desk lifter, or hand forklift, whichever was best suited for

the particular case. Figures 8 and 9 show

views of weighing operations during the survey. The exception to this was the weighing of

a file cabinet for which a set procedure was

established using only a load platform and a wood bearing strip. The following is a detailed

description of the procedure in the form of instructions to the survey team which was used

throughout the survey.

In most cases, file cabinets will be found backed

against a wall, either standing alone or in groups placed

closely together. The procedure that will be used to weigh these items is designed to minimize strenuous handling in the weighing operation. Two men will be

needed to perform the task. The units will be weighed

with the load platform positioned on the floor. First, the cabinet will be slid out from the wall 12 inches or more. Next, place the load platform on the floor directly

in front of the cabinet with the long dimensions of both

objects in line. Place the short length wood bearing

strip (2x4-in) on its broad side on the load platform

positioned within the loading area parallel to the front

of the file cabinet. (See figure 10 top). Tilt the file cabinet back so that the front edge of the bottom sur- face will be raised 5 or 6 inches off the floor. Slide the platform straight forward under the cabinet until the wood bearing strip is located near the center of the bottom surface of the cabinet. Lean the cabinet forward

to make contact with the bearing strip on the load platform and rock the cabinet to an upright position. (See

fig. 10 bottom). If the cabinet is not balanced on the bearing strip, apply with the hand the necessary force

in a horizontal direction to maintain the cabinet in an

upright position while the load indicator is being read. The cabinet shall be removed from the load platform

and replaced in its original location by reversing the handling operation leading up to weighing.

7
FIGURE 7. Equipment and supplies for survey work.

3.7. Measurements of Contents in

Selected Items

The weight of all of the contents found in a room was determined by weighing. The noncombustible portion of the contents was esti- mated directly in pounds. The amount of the

combustible contents associated with selected

items was estimated either as a percentage of

the total capacity of the item to hold paper, or

as volume of contents in cubic feet, or both,

depending on the type of item. Specific ex- amples follow:

1. Desk

(a) Regular type—estimated the total

amount of combustible contents on top

and inside as a percentage of the volume capacity of the drawers. Also,

estimated the volume of combustible

contents on top in cubic feet.

(b) Miscellaneous metal type—separate

estimates of the volume of combustible

contents both on top and inside were made in terms of cubic feet.

2. File Cabinets

(a) Regular type—estimated the total of

combustible contents as a percentage

of the volume capacity of the drawers.

Contents on top of the item were con- sidered unassociated and were designated free contents (code = 0001).

(b) Miscellaneous type—estimated the

total amount of combustible contents

in cubic feet.

3. Bookcases

For all bookcases, estimated the amount of

combustible contents within the case in

cubic feet.

4. Computer Program for Data Analysis

A flexible computer program in Fortran IV

language was written to analyze the data and

to provide outputs in tabular and graphical

form. The program can handle a maximum of

900 rooms from a given building or from a combination of buildings, making maximum

usage of the 65,000 storage cells of a UNIVAC

1108 computer. Use is also made of available

subroutines for statistical analysis, frequency,

and plotting. The time for a complete run is approximately 19 + 2.6 N seconds, where N

equals the number of rooms. An auxiliary program is used to check the input data for obvi- ous errors or missing entries. Further details are given in Appendix B.

8
FIGURE 8. Weighing techniques for desks.

5. Application of Techniques—Initial Survey Results

To date, load surveys have been conducted in

two office buildings. The NBS Administration

Building, located at Gaithersburg, Maryland,

is an 11-story reinforced concrete 45 by 225 ft building of rectangular shape completed in

1965. Except for the basement and utility

rooms, it was surveyed completely from February to May 1967. The area surveyed covered

70,820 ft 2 in 335 rooms. Of this 53,689 ft 2 or 252 rooms were offices. The U.S. Civil Service

Commission Building, FOB (Federal Office

Building) No. 9, located at 19th, 20th, D and E

Streets, N.W., Washington, D.C., is a 7-story

reinforced concrete H-shaped structure completed in 1963. A sampling of 55,130 ft 2 of

space (48,407 ft 2 office), considered to be representative of its 573,000 ft 2 total, was sur- veyed in July 1967. The total area surveyed was 125,950 ft 2 covering 556 rooms. According

to room usage category, there were 453 office,

9
Figure 10. Weighing a file cabinet.

8 laboratory, 26 storage, 22 conference, 1 lounge, 8 lobby, 13 library, 5 file, and 20 rooms

classified as other. The NBS building was sur- veyed at an average rate of 430 ft 2 /hr. The

CSC building was surveyed at an average rate

of 590 ft 2 /hr. These rates reflect the tedious

detailed work in the pilot study needed to de- : f

velop the survey techniques and procedures and

to set a firm foundation for the advanced sur- vey methods.

Based upon experience gained in surveying

the NBS Administration Building, significant

changes were made in the survey procedure for

FOB 9. These included adding estimates of

combustible contents on top of desks and tables,

| and within miscellaneous files, combining items

of similar type and weight, and substituting a. - volume estimate for a linear measurement of s contents. Because of this, and the fact that two

buildings may not represent a true sampling j a of office building types and use conditions, j

- these results are to be considered as prelimif |J nary.

The output is in the form of 15 tables andii i

10 sets of graphs (see list, Table B-l of Ap- ; jj pendix B) which should provide meaningful ! information on the individual items and their '' |

relation to the geometry of the structure. These include

(1) The average weight of a file cabinet, -; - desk, bookcase, etc. (2) The frequency distribution of weight

and combustible content for these items.

(3) The average amount of its contents.

(4) The discrete unit load (weight of item/

base area of item) for each item.

(5) The distribution of loads on floor sec- • tions.

(6) The variation of loads by floor level. (7) The percentage of space occupied by

load items.

(8) The distribution of loads by room area. <l Some of the results from the pilot study are presented only to illustrate the type of com- 1 i! > puter output that was developed as a first or- der statistical evaluation of the data. The re- j suits are presented in tables 2 through 6 and 1

figures 11 through 24.

Table 2 shows the distribution by room - usage of the mean movable contents, interior

finish, and total fire loads for the two buildings.

The movable contents portion is listed both in ' pounds per square foot and expressed as a

percent of the total load (combustible and noncombustible) . Also shown for FOB 9 are the

separate listings of the mean values of "free"

and "adjusted" movable contents fire load. The

total fire load is the sum of the movable con- 1 tents and the interior finish fire loads, without

adjustments. Table 3 lists the percentage of

combustible contents within three types of en- ; closed steel furniture.

Table 4 gives the equivalent uniformly dis- '| j tributed load for each floor level in both build- i ings surveyed. The first six floor levels are ' those for FOB 9 and the following 11 are for 1 the NBS building. The bottom line shows a

distributed load for the two buildings.

10
Table 2. Mean movable contents, interior finish and total fire loads

Room usage

NBS Administration Bldg. FOB 9

No. of rooms

Movable

contents

Interior

finish

fire load

Total

fire load Xo. of rooms

Movable contents

Interior

finish

fire load

Total

fire lVie'Au load

fire

r ercent

of total load

fire load

JT ciXtill I _ r 01 total

1 _ l load

v ree contents

"AH-Ad- justed"

tents*

psf % psf /o psf psj psj

Off! no AOL 4.9 42.2 1 .

1

fi ft 9ft 1 3.5 38.2 2.3 2.4 1 i *± . o Laboratory. . - Co 7.8 46.8 0 9 8 7 0 23 20.9 65.4 on i 3 4.7 26.4 1.6 2.7 1 .5 6.2

Conference 10 2.5 54.7 1.1 3.6 12 2.5 82.9 2.5 2.5 2.2 4.7 Lounge 1 1.3 91.2 1.3 2.6 0

1 .{>u i) y 7 0.7 51.3 0.3 1.0 1 0.1 4.0 0.1 0.1 1.0 1.1 Dining room . _ _ 0 0 Library 11 15.9 59.3 0.9 16.8 2 7.8 34.4 6.6 7.3 1.0 8.8

File room . . 3 28.8 63.3 1.0 29.8 2 28.4 58.4 3.3 6.7 0.8 29.2

Other 20 0.4 22.0 0.8 1.2 0

Bldg, Total 335 5.3 45.9 1.0 6.3 221 3.8 40.9 2.3 2.5 1.5 5.3

According to derating factors in Table 1.

Table 3. Combustible contents of steel furniture

Percent

combustible

contents of room

within

Enclosed steel shelving

Steel files and

desks

Insulated files, safes

NBS Administration

Bldg.

Offices

(%)

3.4

27.3

.7

File rms.

(%)

2.9

49.8

.0

Total

(%)

2.6

23.9

.5

FOB 9

Table 4. Uniformly distributed load for each floor level in NBS Administration Building and FOB 9

Equivalent distributed load for each floor level

Offices

(%)

2.8

36.7

.3

File rms.

(%)

0.0

88.5

.0

Total

Floor Total Load Total Area Dist. Load

FOB 9 (%)

2.6

40.2

.2

Table 5 gives the percentage of room floor area covered by the occupancy load for each room use category.

Table 6 gives a list of rooms loaded with 25

lb or more per square foot of area. The location and room area is shown along with the

value of uniformly distributed load. These are

the rooms that are considered to be heavily

loaded and are listed for possible reexamination of types and arrangements of loads. As

expected these are principally file rooms, stor- age rooms, and library rooms, although some

office rooms are included.

Figures 11 and 12 present frequency distributions (histograms) for uniformly distributed loads in office rooms in the NBS and

FOB 9 buildings, respectively. The height of

each bar represents the number of rooms

lb ft' psf 1.0 38184.0 6197.0 6.2

2.0 . 19565.0 2500.0 7.8

3.0 199413.0 19285.0 10.3 4.0 119478.0 9504.0 12.6

5.0 5440.0 1334.0 4.1 6.0 133531.0 16310.0 8.2

NBS ADMINISTRATION BUILDING

1.0 65720.0 11178.0 5.9

2.0 55217.0 5859.0 9.4

3.0 88273.0 5947.0 14.8 4.0 80849.0 6037.0 13.4 5.0 61853.0 6040.0 10.2

6.0 110099.0 5900.0 18.7 7.0 89344.0 5989.0 14.9 8.0 94980.0 6283.0 15.1 9.0 76861.0 6059.0 12.7

10.0 57310.0 5996.0 9.6

11.0 43027.0 5532 .

0

7.8

TOTAL

17 1339126.0 125950.0 10.6

11
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Table 5. Percentage of room floor area covered by the occupancy

load for room, usage categories and for the building total

Percen- Room use category tage Occupied Total

of oc- area area cupied

space

ft 2 ft 1 ft 11

(jitice _ _ - •JIQfi'i (J O loU-> . rt 1 n9DQfi

Labs. . _ . — ZU . v o / o . u

1 7^7

Storage - - . . 0£ O ZD . Z 57 1 . 3 ZZl Ml . Conference ._ ._ - } 1 o ol .U OA Q7 Q 8(199 Lounge.

15.1 35.9 238. Lobby. . . 7.6 3U.4 4110. Dining Room.. . . _ .0 .0

T 1 1 Y\ V T" V 31 .0 75S.7 2444.

File room .... ... 38.3 519.8 1358. Other 3.7 135.9 3695.

Building total . _ 29.0 36563 .

125950.

Table 6. Rooms loaded with 2h~ lb or more per square foot of area

Room No. Floor Distributed Room area Room

load use

psf ft*

03336 3 0 29 4 170 0 1 04445 4 0 57 9 575 0 9 6312A 6 0 29 5 275 0 9 A0123 1 0 59 8 172 0 9 A0303 3 0 30 6 187 0 8

A0335 3 0 46 5 187 0 8 A0404 4 0 38 9 20 0 0 A0422 4 0 28 8 164 0 9 A0424 4 0 34 7 187 0 1 A0439 4 0 26 8 20 0 3 A0442 4 0 42 o 20 0 3 A0629 6 0 48 6 272 0 8 A0631 6 0 63 1 187 0 8 A0633 6 0 52 8 187 0 3 A0635 6 0 47 6 187 0 3

A0700 7 0 27 7 275 0 1 A0719 7 0 46 7 1S7 0 3 A0730 7 0 25 6 257 0 8 A0835 8 0 30 8 231 0 2 A0839 8 0 34 1 231 0 2

A0840 8 0 27 8 231 0 1 A0900 9 0 28 6 275 0 1 A0922 9 0 46 3 187 0 3 A0924 9 0 31 8 181 0 3 A0928 9 0 47 2 172 0 9 A1102 11 0 32 6 12 0 3 A1106 11 0 72 5 6 0 3 All 18 11 0 44 8 6 0 3 A1135 11 0 58 6 72 0 3

which contain loads within a 2 psf interval ex- tending from 1 psf below to 1 psf above the

plotted value. Thus, the bar plotted at zero

(0), covers loads up to 1 psf, the bar at 2 psf,

includes loads from 1 up to 3 psf, the bar at

4 psf includes loads from 3 up to 5 psf, etc. Note that some statistical data is printed out

at the top of the plot.

An important factor in the study of floor

loads on buildings may be the relationship

between room size and room loads. Figures 13

and 14 show plots of room area versus uniformly distributed load for office rooms in both

buildings. More data appears to be necessary

in order to delineate a possible relationship

between room size and distributed loads.

The load items in office buildings vary widely

in weight and in size. The weight of a given

item divided by the floor area that it occupies is defined as its discrete unit load. It follows that

items of different weight may produce the same discrete load on the floor depending on

the respective item size. The sum of the floor areas occupied by load items is defined as the

loaded area. Figures 15, 16, 17, and 18 show

the relationship between loaded area and dis- crete load values for office rooms, storage

rooms, file rooms, and library rooms in the

NBS Administration Building. The area carrying loads greater than a discrete load value is given as a ratio of the total loaded area on the

vertical axis and the value of discrete load is given on the horizontal axis. Therefore, these

plots indicate the fraction of the loaded area

carrying loads greater than a particular value

of discrete load. For example, it is seen from

figure 15 that 38 percent of the loaded area in

office rooms support loads greater than 25 psf.

Figures 19 and 20 show frequency distributions of the percent of room floor area covered

by the occupancy load in office rooms in the

NBS Administration and FOB 9 buildings,

respectively.

Figures 21 and 22 show frequency distributions for movable fire contents in offices in the

NBS Administration and FOB 9 buildings,

respectively.

Examples of the correlations between weight

of combustible contents and estimated amount

of contents (percent or cubic feet) are shown

for a desk and a file cabinet in figures 23 and

24, respectively. The amount of contents for

desks and file cabinets were estimated as percentages of the total storage capacities of the

items. For bookcases, volume estimates were made of the amount of contents in units of

cubic feet. The weights of combustible contents were determined by subtracting from the total

weight recorded for an item, the empty weight

of the unit, and the weight of noncombustible

content. The plots were constructed to aid in

evaluating the work of the survey team members in estimating amounts of contents and to show where improvements or changes in techniques are needed. For each plot a least square

fit is given at the bottom of the graph. This

is an equation of the straight line most com- mon to all points,

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In the case of miscellaneous metal files and

of miscellaneous fire-rated files, where the contents measurements were not available * and

the empty weights were unknown, the combustible weights were taken as 48 percent and

25 percent of the total weights. These ratios were based on available data from standard

files.

6. Discussion

This preliminary survey covered a total of

125,950 ft 2 of which 102,096 ft 2 were con- sidered to be office space. Although this ex- ceeds by over 14,000 ft 2 the office space sur- veyed and reported in BMS 149, it represents a

i small statistical sampling from only two buildjings, and should not be considered representative of all office space. In particular, the occu-

! pancy load is likely to change appreciably over

the years.

Compared to the survey results reported in

BMS 149, this survey includes a larger sampling (in terms of area), classification of

"free" combustible contents (i.e., on top of

desks versus within desks) and the spatial distribution of combustible items within the room

according to a floor area grid pattern.

6.1. Review of Initial Work

Some changes in survey techniques were made during the course of the work in the

pilot study. The most significant ones were

concerned with estimating the amount of combustible content associated with items of furniture. Other changes were made to either

expedite a measurement procedure or to improve the coordination of the survey team. The

net results of these changes were improved

efficiency and additional data refinement.

A great deal of attention was devoted to the

elimination of human errors in data recording —principally in transferring the data from the

log sheets to computer cards. As a result an

auxiliary computer program was developed to locate all obvious errors in the data prior to submitting it to the main program.

7. Future Work

Additions to the computer program are planned which will provide statistical comparisons between buildings, and rules for combining or separating data. Also it is planned to use stratified and conditional sampling techniques in future surveys according to the rules

of probability sampling. The nature of the

work will be evolutionary, depending on past

findings to reduce the effort in any structure. One approach is to have the team captain walk

through the building before measurements are

started assigning each room to a use category

and—within large categories like "office"—to a subcategory by weight (heavy, medium,

light) . The sample of rooms to be surveyed may

then be selected using different sampling fractions for different categories and subcategories.

All file rooms, storage rooms, etc., will be sur- veyed until a larger population has been ac- cumulated. The team leader will include in the

sample all rooms visually estimated to be in

the upper 10 to 15 percent, to permit a finer

definition of the extreme loads.

A similar philosophy says office buildings in

other geographic regions should be considered

to be akin to those already surveyed until a

representative sample proves otherwise, whereupon exhaustive surveying would be resumed.

This conceptual approach is valid for office building types (government, private, insurance, etc.).

Grateful acknowledgement is made to J. M.

Spang for his most valuable contributions to the details of the program in the early stages

of the planning and the surveying work; to John Smith, Computer Services Division, for

preparing and debugging the computer program, and to all members of the survey team.

8. Selected References

[1] The amount of possible strain on a crowded floor, American Architect and Building News, p. 34, Apr. 15, 1893, Prof. Kernot.

[2] A study of office building live loads, Eng. News

Record 90, 584, March 29, 1923.

[3] Minimum live loads allowable for use in design of

buildings, Report of the Department of Commerce Building Code Committee, Nov. 1, 1924. (Out of print.)

[4] John W. Dunham, Design live loads in buildings,

* In some instances administrative restrictions prevented the survey team from obtaining contents measurements for items containing classified information and for executive's furniture when

the individual was not available to give consent.

Trans. Am. Soc. Civil Engrs. 112, 725, 1947.

[5] American standard building code requirements for minimum design loads in buildings and other

structures, NBS Miscellaneous Publication

M179, 1945.

[6] NBS contributions to building codes, reprint from

NBS Tech. News Bull., Oct. 1950.

[7] Live loads on floors in buildings, John W. Dunham, Guttorm N. Brekke, and George N. Thompson, NBS Building Materials and Structures Report BMS133, December 19, 1952.

[8] Fire Resistance Classification of Building Constructions, NBS Building Materials and Structures Report BMS92, 1942.

27
[9] S. H. Ingberg, J. W. Dunham, and J. P. Thompson, Combustible contents in buildings, NBS

Building Materials and Structures Report

BMS149, 1957.

[10] J. J. Loftus, D. Gross, and A. F. Robertson, Potential heat—A method for measuring the heat

release of materials in building fires, ASTM

Proc. 61, 1336-48, 1961. Appendix A. Description of Coded Records

Data on log sheets

t. First row—general room data—40 digits (1) Room number—5 digits (alphameric)

(2) Floor level—3 digits; third digit will be zero unless mezzanines, balconies, or the like occur between floors. (a) Range: —9 to 99, so that basements may

be considered.

(b) Examples:

010 = 1st floor 100 = 10th floor 011 = first balcony between 1st and 2d

floors 012 = second balcony between 1st and 2d

floors — 010 = 1st basement

(3) Use of room—1 digit

(a) Designates by code the use of the room:

1. Office

2. Laboratory

3. Storage

4. Conference

5. Lounge

6. Lobby, Reception Room

7. Dining Room

8. Library

9. File Room

0. Other

(b) Each type of building will have its own

code—i.e., the above code is for an office building.

(4) North-South dimension—3 digits (a) Floor dimension in feet

(5) East-West dimension—3 digits (a) Floor dimension in feet

(6) Height of room—2 digits (a) Measure in feet

(7) Number of male personnel—2 digits

(a) Range: 0 to 99

(8) Number of female personnel—2 digits (a) Range: 0 to 99

(9) Number of items—2 digits (a) Total number of items in room

(10) Surface finish—6 digits, to represent, in order, floor, ceiling, North wall, East wall,

South wall, West wall.

(a) Designate by code the unit weight ex- pressed in terms of combustible equivalent. Use "Finish Materials List." 0 Noncombustible

1 Less than 0.1 psf 2 0.1 to 0.2 3 0.21 to 0.40 4 .41 to .60 5 .61 to .80 6 .81 to 1.0 7 1.01 to 1.5 8 1.51 to 2.0 9 greater than 2.0 (see notes)

(11) Trim—3 digits (a) Estimate weight, in pounds, of combustible doors, window sash, shelving, and

other trim. Use "Combustible Trim List." (12) Weight of floor covering—4 digits (whole

number, decimal point, and two decimal

places)

(a) The unit weight in psf of floor cover- ings such as carpets, rugs, etc., will be determined and recoz'ded.

(13) Area reduction—4 digits (floating point)

The major N-S and E-W dimensions of a room are used to compute the room area. When there is a recess within the area defined by the major dimensions, the area of

this recess is subtracted from the first computed room area. The recessed area is recorded in square feet under "Area Reduction."

(14) Notes

(a) Unit weight (s) of combustible surface

greater than 2.0 recorded in sequence

corresponding to order of occurrence of "code = 9" entries from left to right in surface finish columns.

(b) Comments regarding the room in general. (c) Description of data which are recorded

as "other."

II. Second and succeeding rows—28 digits each

(1) Item No.—2 digits

Consecutive numbering of items.

(2) Item code—4 digits (a) Each item will be assigned a four digit

numeric code in accordance with the es- tablished coding series. (b) When an item is encountered that has

not yet been assigned a code number

and described in reference catalog this column will be left blank, and a description of the item (including empty weight

and base area, if possible) will appear under "Notes." Where appropriate, a

Polaroid picture will be taken and the

log sheet "Item No." written on the back

for later reference in assigning an item

code. For unusual or "one-of-a-kind" items, a

designation of "miscellaneous" will be

written under "Notes."

(3) Location—2 digits (See fig. 1) (4) Base area code—1 digit

(a) A 1 digit code will be used to indicate whether an item is occupying space on

the floor or located on top of another

item (e.g., a bookcase section on top of a table)

(b) Code designation

1—Items occupying space on the floor 0—Items not occupying floor space (the

computer will assign the weight of this item to the floor section over which

it is located).

(5) Miscellaneous item base area—4 digits

(a) The base area, in square inches, for miscellaneous items only will be recorded in

this column.

(b) The base area of items on legs is defined as the area enclosed by straight

lines connecting the legs. (6) Total weight—4 digits

(a) The total weight of the item and its contents in lbs. (b) Range: 0 to 9999 lbs. (7) Contents, weight noncombustibles—4 digits (a) Weight, in pounds, of noncombustible

contents, such as metal, glass, etc.

28
(8) Contents category—1 digit (a) Designate by code of content category

1 100 percent paper

2 100 percent books

3 Mixture

(9) Contents measurement

(a) Percent of capacity—2 digits

This column records the estimated

amount of combustible contents in an

item as a percentage of the total capacity of the item for papers. The estimate

is recorded to the nearest 10 percent

with range from 0 percent to 990 percent

(e.g.,, 60 percent is recorded as 06 and

120 percent is recorded as 12)

(b) Cubic feet—3 digits

(whole number, decimal point, one deci- mal place) The amount of contents within selected items are estimated in cubic feet. This estimate is recorded to the nearest tenth of a cubic foot with range from 0.0 ft :* to 9.9 ft 3. (10) Combustible contents on top—3 digits

(whole number, decimal point, one decimal

place)

(a) The amount of free combustible contents on top of certain items (e.g., desks and

tables) are associated with those items. The amounts of these contents are esti- mated in cubic feet to the nearest tenth

of a cubic foot with range from 0.0 ft 8 to 9.9 ft 3. (11) Notes

(a) Comments regarding the particular item.

(b) A full description of the item if an item

code is not available.

(c) The weight of contents if the item cannot be weighed while still containing its contents.

(d) Combustible contents of higher heat of combustion (e.g., plastic, rubber, animal

and vegetable oils, fats and waxes, flam- mable liquids, asphalt, and other petro- leum-base products) when present in excess of 20 percent of the total movable

contents combustible load for the room. Appendix B. Computer Program for Live Floor Loads and Fire Loads

Read LOAD cord

Read ROOM card i

Last room? YES

NO

Compute INTERIOR FINISH FIRE LOAD

Store ROOM AREA

Print high load rooms OUTPUT 2

1

Print distributed floor load OUTPUT 3

1 Read ITEM card

r Compute and store

various s jbtotols

Last item in room ?

Print high load sectors OUTPUT I

Print frequency of item weights OUTPUT 24

17 Print high load items OUTPUT 25

- f

Figure B-l. Computer program block diagram.

can handle up to 6000 blocks, each of which consists of five quantities—item

code, floor, room number, section, and concentration. STAT: This routine calculates, for a given set of

values, the mean, standard deviation, and

tolerance limits. FREQ: This routine calculates, for a given set of

values, the number of occurrences (fre- quency) within selected intervals of width. In operation, the program first reads the LOAD card

containing values of the limiting weights w\, wi, W3,

etc. It then reads the data deck consisting of a ROOM

card followed by a prescribed number of ITEM cards. As the cards are read, a series of subtotals are formed,

which are indexed according to (a) floor, (b) room,

(c) item code, (d) room use code, and (e) room sector. Also, subsets of the room data and item data are writ- ten on a drum (the drum could be replaced by a tape

for a tape-oriented computer). After the ITEM cards

for a given room have been read in, area sectors having

a distributed load equal to or greater than wo are

printed as OUTPUT 1. The process repeats with the next ROOM and associated ITEM cards. A ROOM

card with special room number designation ZZZZZ sig- nals the end of the deck, and the program prints OUTPUTS 2 through 21, computed from the appropriate

subtotals. Most of these outputs are calculated in dis- joint blocks of program so that, with few exceptions,

they may be removed from the program if desired, or

their order may be changed. To obtain OUTPUTS 22 through 25, the information is read back from the drum

in several passes, then selected and organized into the

desired form for printout.

Figure B-l is a simplified block diagram of the main

program. The present output is in the form of 15 tables and 10 sets of graphs, listed in table B-l. A "set" of graphs generally consists of up to 11 individual graphs,

one for each of the 10 room use types, and one for the

total building. The program consists of a main pro- gram, designated LOADS, and five subprograms, desig- nated PLOT, SCALE, SORT 6, STAT, and FREQ.

The functions of the subprograms are as follows: PLOT: This routine is used to plot (a) a series of individual points from given x, y coordinates, or (b) a histogram.

SCALE : This routine is used to calculate the scale of x and y values for the PLOT routine. SORT 6: This routine arranges blocks of data into ascending order by load concentration. It

Table B-l. Listing of computer program output

1. Table of room sectors with distributed load greater

than or equal to 100 psf.

2. Table of rooms with distributed load greater than

or equal to 25 psf.

3. Table of distributed load for each floor.

4. Table of number of items of each type in each type

of room.

5. Table of average percent of item capacity.

6. Table of load per item as percent of total load.

7. Plot of relative distribution of loaded area with

loads greater than discrete load value.

8. Table of percent of occupied space and total area by room type.

29
9. Plot of frequency distribution for distributed room

loads.

10. Plot of room area versus distributed load.

11. Plot of frequency distribution of percent of occupied space in a room.

12. Table of distribution of interior finish fire loads.

13. Table of mean interior finish fire loads.

14. Table of mean movable fire loads.

15. Table of mean total fire loads.

16. Plot of frequency distribution of movable fire contents.

17. Table of percent of combustible contents within

steel desks, files, safes, etc.

18. Plot of frequency distribution of interior finish

fire loads.

19. Plot of frequency distribution of total fire loads.

20. Plot of frequency distribution of distributed loads on room sectors.

21. Plot of frequency distribution of surface finish fire load.

22. Plot of combustible contents vs. estimated amount

for selected items.

23. Table of frequency of occurrence of items.

24. Table of frequency of item weights.

25. Table of items with distributed load greater than

or equal to 150 psf.

30

frU.S. GOVERNMENT PRINTING OFFICE: 1968 0—319-891


Announcement of New Publications in

Building Science Series

Superintendent of Documents,

Government Printing Office,

Washington, D.C., 20402

Dear Sir: Please add my name to the announcement list of new publications to be

issued in the series: National Bureau of Standards Building Science Series. Name

Company

Address

City State . Zip Code

(Notification key N-339)

NATIONAL BUREAU OF STANDARDS

The National Bureau of Standards1 was established by an act of Congress March 3, 1901. Today, in addition to serving as the Nation's central measurement laboratory,

the Bureau is a principal focal point in the Federal Government for assuring maximum application of the physical and engineering sciences to the advancement of technology in industry and commerce. To this end the Bureau conducts research and

provides central national services in three broad program areas and provides central national services in a fourth. These are: (1) basic measurements and standards,

(2) materials measurements and standards, (3) technological measurements and

standards, and (4) transfer of technology.

The Bureau comprises the Institute for Basic Standards, the Institute for Materials

Research, the Institute for Applied Technology, and the Center for Radiation Research.

THE INSTITUTE FOR BASIC STANDARDS provides the central basis within the

United States of a complete and consistent system of physical measurement, coor- dinates that system with the measurement systems of other nations, and furnishes

essential services leading to accurate and uniform physical measurements throughout

the Nation's scientific community, industry, and commerce. The Institute consists

of an Office of Standard Reference Data and a group of divisions organized by the

following areas of science and engineering

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and Frequency. 2 THE INSTITUTE FOR MATERIALS RESEARCH conducts materials research leading to methods, standards of measurement, and data needed by industry, commerce,

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and application of radiation to the solution of Bureau mission problems and the

problems of other agencies and institutions. The Center for Radiation Research consists of the following divisions:

Reactor Radiation—Linac Radiation—Applied Radiation—Nuclear Radiation.

1 Headquarters and Laboratories at Gaithersburg, Maryland, unless otherwise noted ; mailing address Washington, D. C. 20234.

2 Located at Boulder, Colorado 80302.

3 Located at 5285 Port Royal Road, Springfield, Virginia 22151.
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