U. S. DEPARTMENT OF COMMERCE

NATIONAL BUREAU OF STANDARDS

AMERICAN STANDARD BUILDING

CODE REQUIREMENTS FOR MINIMUM DESIGN LOADS IN BUILDINGS AND OTHER STRUCTURES

MISCELLANEOUS PUBLICATION M179

U. S. DEPARTMENT OF COMMERCE

. HENRY A. WALLACE, Secretary NATIONAL BUREAU OF STANDARDS

LYMAN J. BRIGGS, Director

NATIONAL BUREAU OF STANDARDS MISCELLANEOUS PUBLICATION M179

AMERICAN STANDARD BUILDING CODE

REQUIREMENTS FOR MINIMUM DESIGN LOADS

IN BUILDINGS AND OTHER STRUCTURES

By

Sectional Committee on Building Code Requirements for Minimum Design Loads in Buildings—A58

Under the Sponsorship of the National Bureau of Standards

Issued October 18, 1945

Approved June 19, 1945, by the American Standards Association

as American Standard A58.1-1945

UNITED STATES

GOVERNMENT PRINTING OFFICE WASHINGTON : 1945

For sale by the Superintendent of Documents, U. S. Government Printing Office Washington 25, D. C. - Price 10 cents

FOREWORD

In the design of buildings it is necessary to use certain assumptions

regarding the weight of the materials used and of the building contents,

as well as the external forces to which the structure may be subjected.

Building codes set minimum values that are to be assumed under

given conditions. In this standard a committee chosen for its special

knowledge of the subject has recorded its recommendations on assumptions as to dead, live, wind, and earthquake loads.

The standard is one of a series presenting recommended building

code requirements that are being developed by technical committees

under the procedure of the American Standards Association. The

general building code program is under the supervision of the Building Code Correlating Committee of the Association.

The objectives of the program and information concerning the

several technical committees and the Building Code Correlating

Committee are given in an announcement, Building Code Standardization, which may be obtained from the American Standards

Association.

Lyman J. Bkiggs, Director
SECTIONAL COMMITTEE

The nersonnel of the Sectional Committee on Building Code Ren^^^mmimnR Design Loads m BuHdrngs-ASS, which

developed the standard, is as follows: National Bureau of Standards, Sponsor George N. Thompson, Chairman,

j H Courtney, Secretary.

Organization represented Representative

American Institute of Architects TheodoreT Coe

(Alternate)

.

American Society of Civil Engineers J*-» L. Edw££.

Building Officials Conference of America - J^A£ Easton

(Alternate). Coast and Geodetic Survey, U. S. Department of Nedmann_ t^SST^'£^:-y^"^^_^^ chafes W. Baeber.

Nattonal Association 6f Real"Estate Bo^rdV/- K. Lee Htder.

National Bureau of Standards, U. S. Department of ^ Thompson. ^b«-ss-w»z"-::-^--- ?o

A

sLEpC

h

OLW

N DegeN. Members-at-Large Henry D. Dewell.

Hugh L. Dryden.

R. R. Martel.

David Lee Narver.

Arthur C. Ruge.

C. A. Willson.

in the building code program.

IV
CONTENTS

Page

Foreword in

Sectional Committee iv Section 1. General

1-1. Scope

1-2. Definitions

1-3. Safe support required

1-4. Additions to existing structures Section 2. Dead Loads 2 2-1. Weights of materials and constructions 2 2-2. Weight of building equipment 2 Section 3. Live Loads 2 3-1. Uniformly distributed floor loads 2

3-2. Provision for partitions 3

3-3. Concentrated load& 3

3-4. Partial loading 3

3-5. Impact loads 3

3-6. Reduction of live load 3

3-7. Restrictions on loading 3

3-8. Posting of live loads 4

3-9. Roof loads (including snow loads) 4

3-10. Other live loads 4 3-11. Load tests 4 Section 4. Soil and Hydrostatic Pressures 4 4-1. Pressure on basement walls 4 4-2. Uplift on floors 5 Section 5. Wind Loads 5 5-1. Minimum design pressures 5

5-2. Exterior walls 5

5-3. Roofs I 5

5-4. Chimneys 6

5-5. Signs , 6

5-6. Other structures 7

5-7. Shielding and unusual exposures 7

5-8. Combined stresses 7 5-9. Overturning and sliding 7 5-10. Stresses during erection 7 Section 6. Earthquake Loads—General 7 6-1. Minimum lateral load - 7

6-2. Combined stresses 7

6-3. Horizontal torsional moments 7 6-4. Distribution of horizontal shear 8

< 6-5, Special requirements 8 Section 7. Earthquake Loads—Major Earthquakes r 8

7-1. Minimum lateral load 8

7-2. Resistance of skeleton frame 9

7-3. Combined stresses- 9

7-4. Horizontal torsional moments " .__ 9

7-5. Distribution of horizontal shear 9

7-6. Connections 9

7-7. Utilization of permanent structural elements 9 Appendix 9 General 10 2-1. Weights of materials and constructions 10 Range in weights 16 3-1 (a). Uniformly distributed floor loads 17

3-6. Reduction of live load 19

3-9. Roof loads (including snow loads) 21

3-11. Load tests 21

5-1. Minimum design wind pressures 21

5-2. Exterior walls 25

5-3. Roofs 25

5-4. Chimneys 26

5-5. Signs 26

6 and 7. Earthquake loads 26 Earthquakes in the United States 27
yj CONTENTS

TABLES

Page 1 . Minimum design dead loads - ]\

2. Minimum uniformly distributed live loads |»

3. Miuimum design loads for materials iy FIGURES

22

1. Snow loads ~ 03

2. Velocity pressures 9S 3 Earthquakes of destructive intensity *°
American Standard Building Code Requirements

for Minimum Design Loads in Buildings

and Other Structures

By

Sectional Committee on Building Code Requirements for Minimum

Design Loads in Buildings—A58

Under the Sponsorship of the National Bureau of Standards

ABSTRACT

Building Code Requirements for Minimum Design Loads in Buildings and

Other Structures (ASA—A58. 1-1945) gives assumptions for dead, live, wind, and

earthquake loads suitable for inclusion in building codes. This document, pre- pared by American Standards Association Sectional Committee A58 under the

sponsorship of the National Bureau of Standards, is one of a series of building code standards prepared by various committees under the jurisdiction of the Building Code Correlating Committee of the American Standards Association. The basis of the requirements is discussed in an appendix, which also gives sup- plementary information useful to those engaged in preparing and administering

local building codes. SECTION 1. GENERAL

1-1. Scope.—These requirements are intended to govern assumptions

for dead, live, and other loads in the design of buildings and other

structures which are subject to building code requirements.

1-2. Definitions.

Building official means the officer or other person charged with the

administration and enforcement of the building code, or his duly

authorized representative.

Bead load means the weight of all "permanent construction and

equipment, including walls, framing, floors, roofs, permanent partitions, and stairways, of a building or other structure. Live load means the load imposed by the occupancy.

Note.—The live load does not include the wind load or earthquake

load. 1-3. Safe Support Required.—Buildings or other structures, and all arts thereof, shall be designed and constructed to support safely all oads, including dead loads, without exceeding the allowable stresses prescribed for the materials of construction in. the structural members.

1-4. Additions to Existing Structures.—When an existing building or

ther structure is enlarged or otherwise altered, all portions thereof

ffected by such enlargement or alteration shall be strengthened, if ecessary, so that all loads will be supported safely without exceeding

the allowable stresses prescribed for the materials of construction in

the structural members.

1
2 Miscellaneous Publications, National Bureau of Standards

SECTION 2. DEAD LOADS

2-1. Weights of Materials and Constructions.—In estimating dead

loads for purposes of design, the actual weights of materials and constructions shall be used, provided that in the absence of definite in- formation values satisfactory to the building official may be assumed.

Note.—For information on dead loads, see appendix, table 1. 2-2. Weight of Building Equipment.—In estimating dead loads for purposes of design, the weight of plumbing stacks and risers, electric feeders, and ventilating and air-conditioning systems shall be included

whenever any of these are carried by structural members.

SECTION 3. LIVE LOADS

3-1. Uniformly Distributed Floor Loads.

(a) The live loads assumed for purposes of design shall be the

greatest loads that probably will be produced by the intended occu- pancies or uses, provided that the live loads to be considered as uniformly distributed shall be not less than the values given in the

following table: OCCUPANCY OR USE LIVE LOAD

Apartment houses: lb/ft2 Private apartments 40

Public stairways 100 Assembly halls: Fixed seats 60 Movable seats 100

Corridors, upper floors 100

Corridors

:

First floor 100 Other floors, same as occupancy served except as indi- cated. Courtrooms 80 Dance halls 100 Dining rooms, public 100 Dwellings 40

Hospitals and asylums:

Operating rooms 60

Private rooms 40 Wards _* 40

Public space 80 Hotels

:

Guestrooms 1_ 40

Corridors serving public rooms 100

Public rooms 100 Loft buildings__-_ 125 Manufacturing, light 125

Office buildings:

Offices 80 Lobbies 100

Schools: Classrooms 40

Corridors 100

Stores : 125 Theaters

:

Aisles, corridors, and lobbies 100 Orchestra floor 60

Balconies 60 Stage floor 150
Minimum Design Loads in Buildings

(b) When occupancies or uses not listed above are involved, the

live load shall be determined in a manner satisfactory to the building

official.Note.—For information on live loads, see appendix, table 2. 3-2. Provision for Partitions.—In office buildings or other 'buildings

where partitions might be subject to erection or rearrangement, provision for partition weight shall be made, whether or not partitions are shown on the plans, unless the specified live load exceeds 80 pounds

per square foot. 3-3. Concentrated Loads.—In the design of floors, consideration

shall be given to the effects of known or probable concentrations of

load to which they may be subjected. Floors shall be designed to carry the specified distributed loads, or the following minimum concentrations, whichever may produce the greater stresses. The indicated concentrations shall be assumed to occupy areas 2){ feet square

and to be so placed as to produce maximum stresses in the affected

members.

Office floors, including corridors 2,000 lb. Garages Maximum wheel load. Trucking space within building "Maximum wheel load. 3-4. Partial Loading.—When the construction is such that the structural elements thereof act together in the nature of an elastic frame

due to their continuity and the rigidity of the connections, and the

live load exceeds 150 pounds per square foot or twice the dead load,

the effect of partial live load such as will produce maximum stress in any member shall be provided for in the design.

3-5. Impact Loads.—The live loads specified in Section 3-1 (a) may

be assumed to include a sufficient allowance to cover the effects of ordinary impact. For special occupancies and loads involving unusual

impacts, such as those resulting from moving machinery, elevators,

craneways, vehicles, etc., provision shall be made by a suitable

increase in the assumed live load.

3-6. Reduction of Live Load.

(a) No reduction shall be applied to the roof live load.

(b) For live loads of 100 pounds or less per square foot, the design

live load on any member supporting 150 square feet or more may be

reduced at the rate of 0.08 percent per square foot of area supported

by the member, except that do reduction shall be made for areas to be occupied as places of public assembly. The reduction shall exceed

neither R as determined by the following formula nor 60 percent:

I *=100 ><Sz'

in which

#=reduction in percent

Z?=dead load per square foot of area supported by the member

L=design live load per square foot of area supported by the

member.

For live loads exceeding 100 pounds per square foot, no reduction

shall be made, except that the design live loads on columns may be

'educed 20 percent.

3-7. Restrictions on Loading.—It shall be unlawful to place, or cause

or permit to be placed, on any floor or roof of a building or other struc- ture a load greater than that for which such floor or roof is designed.

665106°—45 2
4 Miscellaneous Publications, National Bureau of Standards

3-8. Posting of Live Loads.—In every building or other structure, or part thereof, used for mercantile, business, industrial, or storage

purposes, the loads approved by the building official shall be marked

on plates of approved design which shall be supplied and securely

affixed Iqy the owner of the building, or his duly authorized agent, in a conspicuous place in each space to which they relate. Such plates

shall not be removed or defaced but, if lost, removed, or defaced, shall be replaced by the owner or his agent.

3-9. Roof Loads (including snow loads).

(a) Ordinary roofs, either flat or pitched, shall be designed for a

load of not less than 20 pounds per square foot of horizontal projection

in addition to the dead load, and in addition to either the wind or earthquake load, whichever produces the greater stresses. Note.—The figure of 20 pounds per square foot is a minimum. In pre- paring local codes, the map shown in figure 1 in the appendix should be

consulted and the indicated snow load for the* locality, if larger, substituted for this minimum.

(b) Roofs to be used for promenades shall be designed for a minimum load of 60 pounds per square foot in addition to the dead load.

Roofs to be used for other special purposes shall be designed for

appropriate loads as directed or approved by the building official. 3-10. Other Live Loads.

(a) Stair treads shall be designed to support a uniformly dis- tributed load of 100 pounds per square foot, or concentrated loads of 300 pounds spaced 3 feet center to center each occupying an area

1 foot wide by the depth of the tread, whichever will produce the

greater stresses.

(b) Sidewalks shall be designed to support either a uniformly

distributed load of 250 pounds per square foot, or a concentrated load

of 8,000 pounds on an area 2% feet square placed in any position,

whichever will produce the greater stresses.

(c) Driveways shall be designed to support a uniformly distributed

load of 100 pounds per square foot for vehicles weighing less than 3 tons with load, 150 pounds per square foot for vehicles weighing 3 to 10 tons with load, 200 pounds per square foot for vehicles weighing over

10 tons with load, or a concentrated load equal to the maximum

expected wheel load on an area 2){ feet square placed in any position,

whichever will produce the greater stresses.

(d) Accessible ceilings, scuttles, and ribs of skylights shall be

designed to support a concentrated load of 200 pounds occupying an

area 2){ feet square, and so placed as to produce maximum stresses in

the affected members.

(e) Stairway and balcony railings, both exterior and interior, shall be designed to resist a horizontal thrust of 50 pounds per linear foot

applied at the top of the railing.

3-11. Load Tests.—The building official may require a load test of

any construction whenever there is reason to question its safety for the intended occupancy or use. SECTION 4. SOIL AND HYDROSTATIC PRESSURES

4-1. Pressure on Basement Walls.—In the design of basement walls

and similar approximately vertical structures below grade, provision

shall be made for the lateral pressure of adjacent soil. Due allowance I
Minimum Design Loads in Buildings 5

shall be made for possible surcharge from fixed or moving loads. When a portion, or the whole, of the adjacent soil is below a free-water

surface, computations shall be based on the weight of the soil diminished by buoyancy, plus full hydrostatic pressure. 4-2. Uplift on Floors.—In the design of basement floors and similar

approximately horizontal construction below grade, the upward

pressure of water, if any, shall be taken as the full hydrostatic pressure

applied over the entire area. The hydrostatic head shall be measured

from the underside of the construction.

SECTION 5. WIND LOADS

5-1. Minimum Design Pressures.—Buildings or other structures

shall be designed and constructed to withstand the horizontal pres- sures shown in the following table, allowing for wind from any direction. The height is to be measured above the average level of the

ground adjacent to the building or structure.

Design wind pressures for various height zones of buildings or other structures

Height zone Wind pressure

ft lb/ft* Less than 50 _ • _____ 20

50 to 99 24

100 to 199 28 200 to 299 30

300 to 399 32 400 to 499 33 500 to 599 34

600 to 799 35

800 to 999 36

1,000 to 1,199 37

1,200 to 1,399 38

1,400 to 1,599 39

1,600 and over. _ _ _ 40

Note.—The figures given are recommended as minimum. In pre- paring local codes, figure 2 and the accompanying discussion in the appendix should be consulted and larger figures substituted if necessary. These requirements do not provide for tornadoes. They are based on a

design wind velocity of 75 miles per hour corresponding roughly to a 5-minute average of 50 miles per hour (indicated 63 by a 4-cup anemometer) at 30 feet from the ground.

< 5-2. Exterior Walls.—Every, exterior wall shall be designed and con-

' structed to withstand the pressures specified in Section 5-1, Minimum

I Design Pressures, acting either inward or outward.

5-3. Roofs.

. (a) The roofs of all buildings or other structures shall be designed

and constructed to withstand pressures, acting outward normal to the surface, equal to lji times those specified for the corresponding

height zone in which the roof is located. The height is to be taken

as the mean height of the roof structure above the average level of

the ground adjacent to the building or other structure, and the pres- sure assumed on the entire roof area.

(b) Roofs or sections of roofs with slopes greater than 30° shall be

designed and constructed to withstand pressures, acting inward normal
5 Miscellaneous Publications, National Bureau of Standards

to the surface, equal to those specified for the height zone in which the

roof is located, and applied to the windward slope only.

(c) Overhanging eaves and cornices shall be designed and constructed to withstand outward pressures equal to twice those specified

in Section 5-1, Minimum Design Pressures.

(d) Adequate anchorage of the roof to walls and columns, and of walls and columns to the foundations to resist overturning, uplift,

and sliding, shall be provided in all cases. 5-4. Chimneys.—Chimneys, tanks, and towers shall be designed and

constructed to withstand the pressures specified in Section 5-1, Minimum Design Pressures, multiplied by the following factors, depending on shape:

Square or rectangular __ Hexagonal or octagonal

Round or elliptical 5-5. Signs.

(a) Signs in which the projected area exposed to wind consists of 70 percent or more of the gross area as determined by the over-all dimensions shall be classed as solid signs; those in which the projected

exposed area" is derived from open letters, figures, strips, and struc- tural framing members, the aggregate total area of which is less than

70 percent of the gross area so determined, shall be classed as open

signs.

(b) All signs shall be designed and constructed to withstand the

horizontal pressures shown in the following table applied to the

projected exposed area, allowing for wind from any direction:

Design wind pressures

Height from ground to top of sign Wind pressure

Solid signs

(all types) Open signs

(all types)

ft lb/ft> Ib/fV Less than 50 « 25 b 35

50 to 99 30 42

100 to 199 _ 35 49

200 to 299 38 53 300 to 399_ I 40 56 400 to 499 42 58 500 to 599 43 60 600 to 799 . 44 61 800 to 999 45 63

1,000 to 1,199 46 65

1,200 to 1,399 48 67

1,400 to 1,599 49 68

1,600 and over _ _ _ _ _ 50 70

» Solid ground signs less than 50 ft in height shall be designed and constructed to withstand a wind pres- sure of not less than 15 lb/ft*. b Open ground signs less than 50 ft in height shall be designed and constructed to withstand a wind pres- sure of not less than 25 lb/ft2

. Note.—Complete requirements for signs are being developed by

Sectional Committee on Building Code Requirements for Signs and

Outdoor Display Structures—A60.

1.00 0.80 0.60
Minimum Design Loads in Buildings 7

5-6. Other Structures.—The building official may require evidence to support the values for wind pressure used in the design of structures not specifically covered in this section.

5-7. Shielding and Unusual Exposures.

(a) No allowance shall be made for the shielding effect of other

buildings or structures.

(b) If the building or other structure is on a mountain, ocean promontory, or in any other location considered by the building

official to be unusually exposed, higher wind pressures may be^

prescribed by the building official. 5-8. Combined Stresses.—For combined stresses due to wind, dead,

live, and snow loads, the allowable stress may be increased 33}£

percent provided the section thus found is at least as strong as that

required for dead, live, and snow loads alone.

5-9. Overturning and Sliding.

(a) The overturning moment due to the wind load shall not ex- ceed 66% percent of the moment of stability of the building or other

structure due to the dead load only, unless the building or other

structure is anchored so as to resist the excess overturning moment

without exceeding the allowable stresses for the materials used.

The axis of rotation for computing the overturning moment and the

moment of stability shall be taken as the intersection of the outside

wall line on the leeward side and the plane representing the average

elevation of the bottoms of the footings. The weight of earth superimposed over footings may be used in computing the moment of

stability due to dead load.

(b) When the total resisting force due to friction is insufficient to prevent sliding, the building or other structure shall be anchored to withstand the excess sliding force without exceeding the allowable

stresses for the materials used. Anchors provided to resist over- turning moment may also be considered as providing resistance to

sliding.

5-10. Stresses During Erection.—Provision shall be made for wind

stress during erection of the building or other structure. SECTION 6. EARTHQUAKE LOADS—GENERAL

6-1. Minimum Lateral Load.—Every building or other structure,

except a farm building or like structure, shall be designed and constructed to withstand a static lateral load from any horizontal direction

at least equal to 5 percent of the dead load.

6-2. Combined Stresses.—For combined stresses due to the lateral load specified in Section 6-1 together with dead, live, and snow loads,

the allowable stresses may be increased 50 percent provided the section

I thus found is at least as strong as that required for dead, live, and snow loads alone. The section thus found shall also be compared

with that found for the combination of wind, dead, live, and snow

loads, and that section used which provides the greater strength.

6-3. Horizontal Torsional Moments.—The vertical structural units

of a building or other structure that resist lateral load shall be so arranged that, in any horizontal plane, their center of rigidity will be

coincident with the center of gravity of the dead loads of the building

or other structure, or proper provision shall be made for any resulting

torsional moment in the building or other structure.
g Miscellaneous Publications, National Bureau of Standards

6-4. Distribution of Horizontal Shear.—The total shear at any level due to the lateral load shall be assumed to be distributed to the

vertical resisting units at that level in proportion to their rigidities,

except as the deformation of horizontal distributing elements may

modify the distribution.

6-5. Special Requirements.—Every parapet wall shall be designed

and constructed to withstand a normal lateral force of 50 percent of

its weight. Every tank tower, tank, and masonry chimney shall be

designed and constructed to withstand a lateral force from any

direction equal to 10 percent of its dead and vertical live loads.

SECTION 7. EARTHQUAKE LOADS—MAJOR EARTHQUAKES

Note.—It is recommended that these provisions be included in building ordinances in those communities that have experienced earth- quakes of major or near-major intensity, say of intensity of VII or over

in the Rossi-Forel scale. 7-1. Minimum Lateral Load.

(a) Every building or other structure shall be designed and constructed to withstand a minimum static lateral load, acting from any

horizontal direction, as given by the formula

F=CW

in which

i^=Horizontal lateral load in pounds

(7=A numerical coefficient as given hereafter

TF=The total dead load in pounds at and above the plane or elevation under consideration, except that for buildings

used for storage W shall equal the total dead load plus

50 percent of the live load.

(b) The coefficient C shall have the following values (F being

assumed to act from any direction), provided that for buildings not

over 100 feet in height in which the ratio of height to least horizontal

dimension is not over 1.5, C shall be taken as 0.10 for each story.

Values of Cfor parts of buildings or other structures

Part . Value of CDirection of force

Bearing wall 0.20 Division wallFiller wall

.20 .20 |

Normal to surface of wall. , Curtain wall _ _ __ .20 Fire wall 1.00 Parapet wall _ _ 1.00

|

Normal to surface of wall. Cantilever wall_ _ 1.00 Exterior ornamentation

Exterior appendage

1.00

1.00 |From every horizontal direction. Penthouse _ _ Tank tower

.20

.20 jFrom ever}- horizontal direction. Tank plus contents _ _ .20 Masonry pier .20 Masonry chimney __ .20 From every horizontal direction. Smokestack .20 Marquises _ __ .20
Minimum Design Loads in Buildings 9

7-2. Resistance of Skeleton Frame.—In every building having a skeleton frame, such frame shall be designed and constructed to withstand not less than 20 percent of the force specified for the building

itself, without assistance from any walls or floors. By skeleton frame

is meant a framework consisting of columns, girders, beams, and

similar members supporting and transmitting all loads to the foundations.

7-3. Combined Stresses.—For combined stresses due to the lateral load specified in Section 7-1, Minimum Lateral Load, in combination

with dead, live, and snow loads, the allowable stresses may be in- creased 50 percent provided the section thus found is at least as strong

as that required for dead, live, and snow loads alone. The section

thus found shall also be compared with that found for the combination

of wind, dead, live, and snow loads, and that section used which provides the greater strength.

For members with stresses due only to the lateral load specified in

Section 7-1, Minimum Lateral Load, the allowable stresses for the

materials used may be increased not more' than 66% percent.

7-4. Horizontal Torsional Moments.—Those vertical structural units

of the building or other structure which resist the horizontal force

shall be so arranged that in any horizontal plane the center of rigidity

of such resisting structural units will be coincident with the center of gravity of the vertical loads of the building or other structure, or else proper provision shall be made for the resulting torsional moment in

the building or other structure. 7-5. Distribution of Horizontal Shear.—The total horizontal shear at any level shall be assumed to be distributed to the various resisting

units at that level in proportion to their rigidities, except as the deformation of the horizontal distributing elements may modify the

distribution.

7-6. Connections.—Such connections of members as resist the

moments and shears of the specified horizontal force shall also be made

capable of resisting mom'ents and shears due to vertical loads in proportion to their relative stiffness. . 7-7. Utilization of Permanent Structural Elements.—Reinforcedconcrete or masonry walls and all other permanent structural elements

capable of providing resistance shall be assumed to act integrally with

the structural frames in resisting the shears and moments due to the

specified horizontal force, unless specifically designed and constructed

to act independently.

APPENDIX

This Appendix consists of explanatory and supplementary material

designed to assist local building code committees and building officials in applying the recommended code requirements. It. is not a part of American Standard Building Code Requirements for Minimum

Design Loads in Buildings and Other Structures—A58.1; but is provided as background material for users of the standard. In some

cases it will be necessary to adjust specific values in the standard to

local conditions; in others, a considerable amount of detailed information is needed to put the general provisions into effect. This Appendix

provides a place for supplying material that can be used in these situations and also is intended to create a better understanding of the
10 Miscellaneous Publications, National Bureau of Standards

recommended requirements through brief explanations of the reason- ing employed in arriving at them.

The subdivisions of the Appendix are numbered to correspond with

the section numbers in the Code requirements. Since it is not neces- sary to have Appendix matter for every section in the Code, there are gaps in the numbering in the Appendix.

General.—Since 1924, when a report of the Department of Commerce

Building Code Committee entitled "Minimum Live Loads Allowable

for Use in Design of Buildings" was published by the National Bureau

of Standards, the recommendations contained in that document have

been widely used in revision of local building codes and have been

quoted in many textbooks. The recommendations made at that time were based on a study of data obtained from many sources and

represented the considered judgment of experienced architects and

engineers.

At the present time, a continuation of development of building

code recommendations is being carried on by various sectional committees operating under the procedure of the American Standards

Association, with the Building Code Correlating Committee providing

the necessary guidance and correlation. The Sectional Committee on

Building Code Kequirements for Minimum Design Loads in Buildings—A58 is one of these sectional committees. It has considered

the work of the previous committee which brought out the 1924 report

and has taken into account facts developed in later investigations so

as to provide requirements suitable for use under present conditions.

It has also endeavored to cover a wider field than in the earlier report,

and has provided information on the various kinds of loads to which

structures may be subjected. Loads have been construed to include

weight of materials and equipment, weight of occupants and of

movable contents, wind pressures, and earthquake forces. Some of these loads will be the same regardless of the location of the structure and others will vary with local conditions. Information is provided

to make it possible to deal with the whole range of circumstances that

may have to be taken into account.

2-1. Weights of Materials and Constructions.—Values for weights of

different materials and constructions are based on a schedule pre- pared in the Office of the Supervising Architect, Public Buildings

Administration, Federal Works Agency. They have been reviewed

by the National Bureau of Standards and by a number of other

agencies with respect to particular items on which the agency had

information.

To establish uniform practice among designers it is desirable to present a list of materials generally used in building construction

together with their proper weights. Many building codes prescribe

the minimum weights for only a few building materials and in other

instances no guide whatsoever is furnished on this subject. In some

cases the codes are so drawn up as to leave the question of what

weights to use to the discretion of the building official without pro-
Minimum Design Loads in Buildings 11

viding him with any authoritative guide. This practice, as well as the use of incomplete lists, has been subjected to much criticism.

The solution chosen has been to present an extended list in this Appendix which will be useful to- the designer and official alike. However, special cases will unavoidably arise, and so authority is granted to the building official to deal with these. For ease of computation, most values are given in terms of weight

per square foot of given thickness. Cubic-foot values consistent with

the square-foot values are also presented in somes cases. Table 1.

Minimum design dead loads a WALLS

lb/ft3 4-inch clay brick, high absorption 34

4-inch clay brick, medium absorption 39

4-inch clay brick, low absorption 46

4-inch sand-lime brick 38

4-inch concrete brick, heavy aggregate 46

4-inch concrete brick, light aggregate 33

8-inch clay brick, high absorption 69

8-inch clay brick, medium absorption 79

8-inch clay brick, low absorption 89

8-inch sand-lime brick 74

8-inch concrete brick, heavy aggregate 89

8-inch concrete brick, light aggregate 68

12>^-inch clay brick, high absorption 100

12>£-inch clay brick, medium absorption - 115

12>2-inc'h clay brick, low absorption 130

12^-inch sand-lime brick 105

12^-inch concrete brick, heavy aggregate 130

12}^-inch concrete brick, light aggregate 98

17-inch clay brick, high absorption 134

17-inch clay brick, medium absorption 15^

17-inch clay brick, low absorption 173

17-inch sand-lime brick 138

17-inch concrete brick, heavy aggregate 174

17-inch concrete brick, light aggregate 130

22-inch clay brick, high absorption 168

22-inch clay brick, medium absorption 194

22-inch clay brick, low absorption 216

22-inch sand-lime brick 173

22-inch concrete brick, heavy aggregate 216

22-inch concrete brick, light aggregate 160

4-inch brick, 4-inch load-bearing structural clay tile backing 60

4-inch brick, 8-inch load-bearing structural clay tile backing 75

9-inch brick, 4-inch load-bearing structural clay tile backing 102

8-inch load-bearing structural clay tile 42

12-inch load-bearing structural clay tile 58

8-inch concrete block, heavy aggregate 55

12-inch concrete block, heavy aggregate 85

8-inch concrete block, light aggregate 35

12-inch concrete block, light aggregate 55

2-inch furring tile, one side of masonry wall, add to above figures 12

» Weights of masonry include mortar but not plaster. For plaster, add 5 lb/ft2 for each face plastered. Values given represent averages. In some cases there is a considerable range of weight for the same construction. For such ranges, see pages 16 and 17.

665106°—£5 3
12 Miscellaneous Publications, National Bureau of Standards

Table 1.

Minimum design dead loads*—Continued 1 PARTITIONS ib/ft* 3-inch clay tile 17

4-inch clay tile 18

6-inch clay tile * 28

8-inch clay tile 34

10-inch clay tile 40

2-inch gypsum block 9y2 3-inch gypsum block 10y2 4-inch gypsum block I2y2 5-inch gypsum block 14

6-inch gypsum block 1S%

2-inch solid plaster, _• 20

4-inch solid plaster 32

4-inch hollow plaster 22

4-inch concrete block, heavy aggregate 30

6-inch concrete block, heavy aggregate 42

8-inch concrete block, heavy aggregate 55

12-inch concrete block, heavy aggregate 85

4-inch concrete block, light aggregate i 20

6-inch concrete block, light aggregate 28

8-inch concrete block, light aggregate , 38

12-inch concrete block, light aggregate 55 Wood studs 2X4, unplastered 4 Wood studs 2X4, plastered one side 12 Wood studs 2X4, plastered two sides 20 GLASS-BLOCK MASONRY

4-inch glass-block walls and partitions 18 SPLIT FURRING TILE

114-inch 8

2-inch . 8#

CONCRETE SLABS

Concrete, reinforced-stone, per inch 12^

Concrete, reinforced-cinder, per inch 9%

Concrete, reinforced, lightweight, per inch 9 Concrete, plain stone, per inch 12 Concrete, plain cinder, per inch 9 Concrete, plain, lightweight, per inch S}i

a See footnote on page 11.
Minimum Design Loads in Buildings 13

Table 1.

Minimum design dead loads*—Continued

RIBBED SLABS

Depth

in. Width of rib, in inches

12-inch clay-tile fillers 4 plus 2 6 plus 2

8 plus 2y2 10 plus 3 12 plus 3

20-inch metal fillers: 6 plus 2 8 plus 2%

10 plus 3 12 plus 3 14 plus 3__ 30-inch metal fillers: 6 plus 2y2 8 plus 2y2 10 plus 3

12 plus 3 14 plus 3

2-way clay-tile fillers (12X12)

4 plus 2

6 plus 2

8 plus 2y2 10 plus 3 12 plus 3

2-way metal fillers (16X16):

4 plus 2

6 plus 2 8 plus 2%

10 plus 3 12 plus 3 14 plus 3 2-way metal fillers (20X20):

4 plus 2

6 plus 2 8 plus 2y2 10 plus 3 12 plus 3 14 plus 3

MP

49

60

79

96

108

41

5163

6975

4145

56

6187

100

121 13644

55

72

91 103 11642

50

6683

93

105

lb/ft1 5163

82

100

112

4354

67

74

814348

59

63

696289

103

126

14147

6078

96

111 12544

54

7188

100 113

lb/ft' 5265

85

103 116

45

57

70

78

864550

6167

72

6490

107

131 14650

63

83

103

118

13346

58

7694

107

120

iblft? 546787

106

120

47

60

74

82

9047

52

6370

76

» See footnote on page 11.
14 Miscellaneous Publications, National Bureau of Standards

Table 1.Minimum design dead loads a—Continued

FLOOR FINISH AND FILL

Double % wood on sleepers, light-concrete fill Do

Double % wood on sleepers, stone-concrete fill Do

Single Y% wood on sleepers, light-concrete fill Do

Single % wood on sleepers, stone-concrete fill Do

3-inch wood block on mastic, no fill %-inch wood block on stone-concrete fill 1-inch cement fin. on stone-concrete fill 1-inch terrazzo on stone-concrete fill Clay tile on stone-concrete fill Marble and mortar on stone-concrete fill Linoleum on stone-concrete fill Do _s Linoleum on light-concrete fill Do

FLOOR FINISH

1^-inch asphalt mastic flooring 3-inch wood block on ^-inch mortar base.

Solid flat tile on 1-inch mortar base, 2-inch asphalt block, }£-inch mortar'

1-inch terrazzo, 2-inch stone concrete

Finish

floor to top slab,

in.

At 1Q

O4 28

5 40

4 23

5 30

4 38

5 50

3 10

4 40

4 48

4 48

4 48

4 50

4 46

5 58

4 27

5 34

WATERPROOFING

Five-ply membrane

Five-ply membrane, mortar, stone concrete. 2-inch split tile, 3-inch stone concrete. FLOOR FILL

Cinder concrete, per inch Lightweight concrete, per inch. Sand, per inch Stone concrete, per inch WOOD-JOIST FLOORS (NO PLASTER) DOUBLE WOOD FLOOR

12-inch spacing16-inch spacing Joist sizes, in inches: 2x6

2x8

2 x 10 2 x 12 3x6

3x8

3 x 10 3 x 12

3 x 14

a See footnote on page 11.

lb/ft*6

67

8

7

8

9

1112
Minimum Design Loads in Buildings 15

Table 1.

Minimum design dead loads a —Continued

CEILINGS ib/ffi Plaster on tile or concrete 5 Suspended metal lath and gypsum plaster 10 Suspended metal lath and cement plaster 15

Plaster on wooden lath 8 ROOF COVERINGS

Asbestos shingles 4 Asphalt shingles 6 Copper or tin 1 Corrugated iron 2 Clay tile (for mortar add 10 lb)

:

2-inch book tile 12

3-inch book tile 20 Roman 12 Spanish 19 Ludowici 10 Cement tile 16 Composition:

Three-ply ready roofing 1 Four-ply felt and gravel 5H

Five-ply felt and gravel 6 Sheathing, per inch thickness 3

Slate, jKe-inch 7

Slate, 34-inch 10

Skylight, metal frame, %-inch wire glass 8 Wood shingles 3 MATERIALS WW

Cast-stone masonrv (cement, stone, sand) 144 Cinder fill 57

Concrete, plain: Stone (including gravel) 144

Slag 132 Cinder 108 Haydite (burned- clay aggregate) 90 Expanded-slag aggregate 100

Concrete, reinforced: Stone (including gravel) 150

Slag 138 Cinder 111 Masonry, brick: Hard (low absorption) ! 130 Medium (medium absorption) 115

Soft (high absorption) 100 Masonry, ashlar: Granite 165 Limestone, crystalline 165 Limestone, oolitic .* 135 Marble 173 Sandstone 144

I Masonry, rubble mortar:

Granite 153 Limestone, crystalline 147 Limestone, oolitic 138 • Marble 156 Sandstone 137 Terra cotta, architectural: Voids filled 120 Voids unfilled 72 Timber, seasoned: Ash, commercial white 41

Cypress, southern 32

Fir, Douglas, coast region 34

Oak, commercial reds and whites r 45

Pine, southern yellow. _ ^ : 39 Redwood 28

Spruce, red, white, and Sitka 28

•See footnote on page 11.
lg Miscellaneous Publications, National Bureau of Standards

Range in Weights.—Some constructions for which a single figure is given actually have a considerable range in weight. The average

figure given is suitable for general use; but when there is reason to suspect a considerable deviation from this, the actual weight should

be determined.

Examples of the range in weight that have been found for some

constructions follow. It will be noted that there is a difference of over 25 percent in some cases. Range in weight of masonry construction

Construction Unplastered One side plas- tered Both sides plastered WALLS

4-inch clay brick, high absorption

4-inch clay brick, medium absorption

4-inch clay brick, low absorption

4-inch sand-lime brick 4-inch concrete brick, heavy aggre- gate

4-inch concrete brick, light aggregate.

8-inch clay brick, high absorption

8-inch clay brick, medium absorption 8-inch clay brick, low absorption

8-inch sand-lime brick

8-inch concrete brick, heavy aggre- gate

8-inch concrete brick, light aggregate

12%-inch clay brick, high absorption _•_ 12%-inch clay brick, medium absorption 12^-inch clay brick, low absorption. _ 1234-inch sand-lime brick 12^-inch concrete brick, heavy aggre- gate

12%-inch concrete brick, light aggre- gate

17-inch clay brick, high absorption

17-inch clay brick, medium absorption.

17-inch clay brick, low absorption

17-inch sand-lime brick

17-inch concrete brick, heavy aggre- gate . 17-inch concrete brick, light aggregate.

22-inch clay brick,'"high absorption

22-inch clay brick, medium absorption 22-inch clay brick, low absorption

22-inch sand-lime brick 22-inch concrete brick, heavy aggre- gate

33 to 35 38 to 40

45 to 47

35 to 40

45 to 47

30 to 35

64 to 73

74 to 83

84 to 93 67 to 80 84 to 93

60 to 75

90 to 110

105 to 125

120 to 140 95 to 115

120 to 140

85 to 110

120 to 148

141 to 168

159 to 187

125 to 150

160 to 187

115 to 145

150 to 186 177 to 211

198 to 234

157 to 188

198 to 234

lb/ft* 38 to 40

43 to 45 50 to 52 40 to 45

50 to 52

35 to 40

69 to 78 79 to 88 89 to 98

72 to 85

89 to -98 65 to 80

95 to 115

110 to 130

125 to 145

100 to 120

125 to 145

90 to 115

125 to 153

146 to 173

164 to 192

130 to 155

165 to 192

120 to 150

155 to 191 182 to 216

203 to 239

162' to 193 203 to 239
Minimum Design Loads in Buildings 17

Range in weight of masonry construction—Continued

Construction Unplastered One side plas- tered Both sides plastered WALLS—Continued

22-inch concrete brick, light aggregate.

8-inch load-bearing structural clay

tile 12-inch load-bearing structural clay

tile 8-inch concrete block, heavy aggre- gate

12-inch concrete block, heavy aggre- gate

8-inch concrete block, light aggregate.

12-inch concrete block, light aggregate.

140 to 180 37 to 46

50 to 65

50 to 60

75 to 95

30 to 43

45 to 65

lb/ft* 145 to 185 42 to 51 55 to 70

55 to 65

80 to 100 35 to 48

50 to 70

MP

47 to 56

60 to 75

60 to 70

85 to 105 40 to 53

55 to 75 Partitions

2-inch gypsum block 8 to 11 13 to 16 18 to 21

3-inch gypsum block 8. 5 to 12. 5 13. 5 to 17. 5 18. 5 to 22. 5

4-inch gvpsum block 10 to 14. 5 15 to 19. 5 20 to 24. 5

6-inch gypsum block 15 to 22 20 to 27 25 to 32

4-inch concrete block, heavy aggre- gate 27 to 35 32 to 40 37 to 45

6-inch concrete block, heavy aggre- gate 38 to 50 43 to 55 48 to 60

8-inch concrete block, heavy aggre- gate 47 to 60 52 to 65 57 to 70

12-inch concrete block, heavy aggregate 80 to 90 85 to 95 90 to 100

4-inch concrete block, light aggregate. 17 to 23 22 to 28 27 to 33

6-inch concrete block, light aggregate. 23 to 32 28 to 37 33 to 42

8-inch concrete block, light aggregate. 27 to 40 32 to 45 37 to 50

12-inch concrete block, light aggregate. 50 to 60 55 to 65 60 to 70 GLASS-BLOCK MASONRY

4-inch glass-block walls and parti- tions _ 17 to 19

s 3-1 (a) Uniformly Distributed Floor Loads.—A selected list of occupancies and uses more commonly encountered is given in Section

3-1 (a) and the building official is given authority to pass on occupancies not mentioned. Table 2 below is offered as a guide in the exercise

of such authority.
18 Miscellaneous Publications, National Bureau of Standards

Table 2.Minimum uniformly distributed live loads

Ib/fp Air-conditioning (machine space) a 200 Amphitheater:

Fixed sea'ts 60 Movable seats 100 Amusement park structure » 100 Armories 150

Attic

Nonstorage 25

Storage e 80 Bakery 150 Balcony:

Exterior 100

Interior (fixed seats) 60

Interior (movable seats) 100 Boathouse, floors 6 100

Boiler room, framed » 300

Broadcasting studio 100 Catwalks 25

Ceiling, accessible furred 10 Cold storage: No overhead system h 250

Overhead system

Floor 150 Roof 250

Dormitories:

Partitioned 40 Nonpartitioned 80

Drill rooms 125 Driveways (see Garages). Elevator machine room a 150 Fan room a 150

File room:

Letter e 80 Card e 125 Addressograph e 150

Fire escape 100 Foundries a 600

Fuel rooms, framed 400

Grandstands (see Reviewing

stands).

Garages:

Cars, with load, less than

3 tons f 100 Trucks, with load, 3 to 10 tons- f 150 Trucks, with load, above 10 tons f 200 Greenhouses 150 Gymnasiums 100 Hangars f 150

Incinerator charging floor 100

Kitchens, other than domestic. _ a 150

Laboratories, scientific 100 Laundries a 150

lb/ft2 Libraries: Reading rooms 60

Corridors e 100 Stacks (b) Manufacturing

Ice 300

Stockroom (see Storage).

Marquise « 60 Morgue 125

Office buildings:

Files (see File room).

Business machine equipment a 100 Penal institutions: Cell blocks 40

Corridors 100

Stairways, public. _1 100

Printing plants:

Composing rooms 100 Linotype rooms 100

Press rooms : a 150 Paper storage ( d

) Public rooms 100 Railroad tracks ( c

) Ramps, driveway (see Garages).

Ramps, pedestrian (see Side- walks in sec. 3-10 (b) ; also Corridors in sec. 3-1.) Ramps, seaplane (see Hangars). Rest rooms 60 Reviewing stands and grandstands i 100 Rink, ice skating 250 Roof (see fig. 1 and sec. 3-9). Stairways 100

Storage:

Light e 125 Heavy e 250 Hay or grain e 300 Telephone exchange a 150

Theaters: Dressing rooms 40

Grid-iron floor or fly gal- lery

Grating 60 Well beams, 250 lb/lin. ft per pair.

Header beams, 1,000

lb/lin. ft. Pin rail, 250 lb/lin. ft. Projection room 100

Toilet rooms 60 Transformer rooms a 200

Vaults, in offices 6 250

» Use equipment when greater,

b Book stacks 20 lb/ft».

o As required by railroad company.

d Paper storage 50 lb/ft of clear story height.

» Increase when occupancy exceeds this amount.

' Also subject to maximum wheel concentrations,

e Minimum uplift of 20 lb/ft2 with no downward live load.

*> Plus 150ib for trucks.

' For detailed recommendations, see American Standard Specifications for Portable Steel and Wood

Grandstands, Z20.1-1941, or latest revision thereof.
Minimum Design Loads in Buildings 19

For purposes of estimating live loads caused by accumulations of various materials, a list of weights is given in table 3. Some of the

items may also be useful in connection with estimation of dead loads. Table 3.

Minimum design loads for materials

lb/ft* Bituminous products:

Asphaltum 81 Graphite 135

Paraffine 56

Petroleum, crude 55

Petroleum, refined 50

Petroleum, benzine 46

Petroleum, gasoline 42

Pitch 69 Tar 75 Brass 526 Bronze 552 Cement, portland, loose 70 Cement, portland, set 125

Cinders, dry, in bulk 45

Coal, anthracite, piled 52

Coal, bituminous, piled 47

Coal, lignite, piled 47

Coal, peat, dry, piled 23 Charcoal 12 Copper. 556

Cork, compressed 14.4 Earth (not submerged)

:

Clay, dry 63

Clay, damp 110 Clay and gravel, dry 100

Silt, moist, loose 78

Silt, moist, packed 96

Silt, flowing 108 Sand and gravel, dry, loose 100 Sand and gravel, dry,

packed 110 Sand and gravel, wet 120 Earth (submerged):

Clay 80

Soil 70 River mud 90

Earth (submerged) —Continued

Sand or gravel 60 Sand or gravel, and clay__ 65

Gold, solid 1,205

Gold bars, stacked 1,133

Gold coin in bags 1,084

Gypsum, loose 65

Ice 57.2

Iron, cast 450

Iron, wrought 480

Lead 710

Lime, hydrated, loose 32 Lime, hydrated, compacted. _ 45

Mortar, hardened: Cement 130 Lime 110 Riprap (not submerged)

:

Limestone 83 Sandstone 90

Slag, bank 70

Slag, bank screenings 108

Slag, machine , 96

Slag, sand 52

Silver, solid 656

Silver bars, stacked 590

Silver coin in bags 590

Slate__ 172

Steel, cold-drawn 489

Stone, quarried, piled:

Basalt, granite, gneiss 96 Limestone, marble, quartz 95 Sandstone 82

Shale 92

Greenstone, hornblende. _ 107 Tin 459

Water, fresh 62.4 Water, sea 64

Zinc, rolled, sheet 449

3-6. Reduction of Live Load.—The proposed live-load-reduction

formula in Section 3-6 (b) differs from conventional treatment but

is believed to offer a more logical approach than is found in most

building codes. The provisions are based upon a consideration of

data available on distribution of loads in different occupancies, and more particularly a survey made by the Public Buildings Administration covering' loads in a number of Federal buildings. The results

of this survey are to be published in the Proceedings of the American

Society of Civil Engineers.

The system proposed for live-load reduction consists essentially of a basic live load equal to the maximum to be allowed on any panel

and a rapid reduction to a minimum load based upon the relation of

live and dead loads in such a manner that overstress on any member,

due to full basic load throughout the structure, cannot exceed a pre-
20 Miscellaneous Publications, National Bureau of Standards

determined value. Moreover, the system should be such that only

a very small portion of the structure will be overstressed by the probable actual live loads.

It is proposed that:

1. The basic live load shall be the maximum average live load

intended to be allowed on any panel.

2. The basic live load may be reduced for the design of any

member at the rate of 0.08 percent per square foot of area supported by the member.

3. The reduction shall exceed neither R percent as determined

by the following formula nor 60 percent:

*= 100xSr

in which

R—reduction, in percent

Z?=dead load per square foot of area supported by the member

L=design live load per square foot of area supported by the

member.

The maximum reduction is such that if a member supports an area

large enough to allow the maximum reduction, and if the member is loaded with the full design live load, the overstress will not exceed 30

percent. The formula is derived as follows: Let

D and L have the values given above

K==proportional reduction R=% reduction^ 100K.

Then

L+D =1.3[D+(l-K)L]

L+D =l.SD+1.3L-1.3KL

1.3i£Z=0.3Z>+0.3Z

It has been found by comparing the results of this formula with

actual load conditions in a number of buildings that only a small

portion of the structure would be overstressed.

The proposed system is, of course, based on the assumption, as any such system must be, that excessive overloading will be prevented

through posting of allowable loads and adequate inspection. The

system when so safeguarded should provide a suitable basis for design

of buildings without:

(1) The incorporation of so much unused strength as heretofore;

(2) Significant overstress in members from probable loadings;

(3) Danger of structural failure in the remote contingency of

full basic loading on the entire area supported by any

member.
Minimum Design Loads in Building* 21

Since public-assembly occupancies, such as theaters, must be

assumed to be fully occupied under normal conditions, any reduction

would be unwarranted. An exception has therefore been made in

the case of these occupancies.

In the case of occupancies involving relatively heavy basic live loads, such as storage buildings, several adjacent floor panels may be

fully loaded. However, data obtained in actual buildings indicate

that rarely is any story loaded with an average actual live load of more than 80 percent of the average rated live load. It appears that

the basic live load should be unreduced for the floor-and-beam design

but that it could be reduced a flat 20 percent for the design of columns.

Accordingly, this principle has been incorporated in the recommended

code requirement.

3-9. Roof Loads (including snow loads).—Figure 1 showing isopleths

connecting points of equal snow load is based upon a map prepared by

the United States Weather Bureau. Values for any particular

location not on an isopleth may be found by interpolating along the

shortest line through the location between isopleths or between an

isopleth and point having different values. The values shown are probably conservative since they are based upon maximum depth of snow on the ground rather than on roofs. The pressures shown on this map are based upon the maximum

undrifted snow depth on the ground as reported by first order Weather

Bureau stations during the period from the beginning of record to December 1938, inclusive, and on the assumption that 6.5 inches of snow have the same water content as 1 inch of rain. This assumed

density may vary in different localities. Isopleths have been omitted in the region between the Pacific

Coastal Section and Longitude 117° W. due to the irregular distributions associated with rugged terrain.

3-11. Load Tests.—A specific method of test for completed construction has not been given in the requirements, since it may be found

advisable to vary the procedure according to conditions. Some

codes require the construction to sustain a superimposed load equal to twice the design live load for 24 hours without evidence of damage.

Other provide for a superimposed test load equal to one-half of the

dead load plus one and one-half times the live load, with the evident

intention of increasing the stresses in. the affected members by a

definite percentage of the allowable stress. Recovery of at least three-quarters of the maximum deflection within 24 hours after the

load is removed is a common requirement. Concrete and masonry

construction should be at least 60 days old when tested. 5-1. Minimum Design Wind Pressures.—The requirements in Section 5, Wind Loads, are intended for more or less average conditions.

There is considerable variation in wind-velocity pressures in different

parts of the country, as will be seen by reference to figure 2. This

map has been prepared at the National Bureau of Standards, from

data obtained from the United States Weather Bureau. Local

building code committees should consult this map and also obtain

any other available facts on conditions in their own areas. With

this information in hand, any necessary adjustments in requirements can be made. v
22 Miscellaneous Publications, National Bureau of Standards
Minimum Design Loads in Buildings 23

The design wind load, which should not be confused with the

velocity pressure shown on figure 2, is the product of the velocity

pressure and a shape coefficient determined by the geometrical form

of the structure. The velocity pressure is influenced by geographical

location, height above ground, and exposure. It is the computed

pressure on a square foot of surface perpendicular to the wind, repre- senting the kinetic energy of moving air. The design wind pressure, on the other hand, is the actual pressure of wind on a square foot of surface and is affected by the ratio between height and width of the

surface and by other factors.

Figure 2.

Velocity pressures {in pounds per square foot). In arriving at suitable design pressures, without the use of the map

on figure 2, the following must be taken into consideration:

(1) Maximum wind velocities averaged over 5 minutes and cor- rected for instrumental errors as obtained from records of the Weather

Bureau for each of 188 stations;

(2) A seventh-root law for the variation of wind velocity with height

above the ground ; (A review of information on this subject was made

by W. W. Pagon and published in Engineering News-Record, May 23,

1935. This law fits in well with both meteorological and laboratory

data.)

(3) A gust factor, which has been taken arbitrarily as 1.5 at 30 feet, 1.3 at 500 feet, 1.23 at 1,000 feet, and 1.2 at 1,500 feet and higher;

(There is evidence from many sources that the gustiness decreases

with height but that it never completely disappears as known, for example, from airplane flights. The values adopted are conservative. In a paper by W. A. Mattice, "A Comparison Between Wind Velocities as Recorded by the Dines and Robinson Anemometers," Monthly

Weather Review, vol. 66, August 1938, p. 238-240, the extreme gust
24 Miscellaneous Publications, National Bureau of Standards

velocities were 42 percent greater than the fastest single mile, which is itself greater than the 5-minute average. Airplane data show gusts

of the order of 40 ft/sec.)

(4) The corresponding velocity pressure which is simply the product of one-half the air density by the square of the resultant design

speed, the units being self consistent;

(5) A shape factor or pressure and suction coefficients determined

largely from wind-tunnel tests. (The roof data are based on the rec- ommendations in the final report of Subcommittee. No. 31, Committee on Steel of the Structural Division, American Society of Civil

Engineers, published in the ASCE Proceedings, October 1940, part 2, p. 1713-1739.)

The requirements for general use given in Section 5-1, Minimum

Design Pressures, are based on a velocity pressure of 15.4 lb/ft2

, this

odd value being selected to give a round number value (20 lb/ft2

) at 30-foot height for ordinary buildings with shape coefficient 1.3. A

better value of the velocity pressure for any locality could be obtained

by (a) obtaining from the nearest Weather Bureau station the maximum true average velocity Vh for 5 minutes observed during the

existence of the station, corrected for instrumental errors ; (b) reducing

this value to a height of 30 feet by the formula V30/Vh = (30/A) 1/7

, where h is the height of the Weather Bureau anemometer above the

ground; (c) increasing Vso by 50 percent to allow for gusts, obtaining

a design speed for 30-foot height equal to 1.5 V3 q; and (d) computing

the corresponding velocity pressure qQ at the design speed V from the

formula g =0.00256 V2 for V in miles per hour and q

in pounds per

square foot. In brief,

20=0.00576 (S0/h)2/7 Vh

2

. This formula is based on a standard air density of 0.07635 pound

per cubic foot. For localities at considerable elevation above sea

level, a reduction in proportion to the actual density would be warranted.

The shape coefficient depends somewhat on the ratio of height to width, but for ordinary buildings the observed values lie between 1 .3 and 1.5. The variation with height is a stepwise approximation to the formula given. In the design of the main frame, the wind pres- sure is assumed to act on the area of the windward wall. It is not

ordinarily necessary to distribute the load between windward and

leeward walls. By the use of the map shown in figure 2 some of the operations

described above may be dispensed with, since the values shown on the

map incorporate most of the steps taken.

After ascertaining from the map, interpolating between isopleths

if necessary, the velocity pressure for a given place, this should be

multiplied by the following factors to provide for increase in wind

velocity with height:
Minimum Design Loads in Buildings 25

Height Factor

Feet

1 ou to yy _ _ 1. £i iuu to iyy 1 A 1. 41 0(\C\ +r\ to 9QQ zyy 1. O Qnn +r\ qqq ouu vo oyy 1 ft 1. Ann +r» zlqq ^tuu to _ryy_ 1 ft K 1. OO ouu KftO +TjOr» oyy_ ^QQ _

1 7 600 to 799 1. 75 800 to 999_ _ ______ 1. 8 1,000 to 1,199 1. 85

1,200 to 1,399 1. 9

1,400 to 1,599 1. 95

1,600 and over _ _ _ 2. 00 The remaining step is to multiply the velocity pressures thus

obtained by the shape factor of 1.3, which completes the table for

insertion in Section 5-1, Minimum Design Pressures, in place of the one presented for general conditions.

For ordinary buildings and for other buildings whose ratio of height to least width is less than 2 y2 to 1 in which the walls, floors, and

partitions contribute materially to the lateral rigidity, no design

computations or test data need ordinarily be submitted. The building official may, however, require evidence of the safety of the structure. For new types of construction, such as those consisting of prefabricated panels or of unusually light supporting members, the

official will in many cases need adequate evidence that the construction is capable of resisting the pressures to which it may be subjected.

5-2. Exterior Walls.—By failure of windows, or otherwise, the interior

may be subjected to either the full pressure or suction acting on the

building. Hence, any exterior wall should be able to withstand the > full wind load acting either inward or outward.

5-3. Roofs.—In case it is desired to make allowance for combined

loadings inward and outward on roofs, the following requirements are suggested:

Roofs or sections of roofs shall be capable of withstanding the

following loads acting simultaneously on the windward and leeward

slopes:

Slope

Exterior load coefficients * (factors to be

applied to loads specified in sec. 5-1) Windward slope Leeward slope

20° or less __ __ __ Between 20° and 30° Between 30° and 60° Between 60° and 90°

-0. 60

0. 06A - 1. 8

0. 015A-0r45

0. 45

-0. 45 -0. 45

-0. 45 -0. 45 •

» Positive values indicate an inward load; negative values an outward load. A is the roof slope in degrees.
26 Miscellaneous Publications, National Bureau of Standards

The maximum outward force on a gable roof occurs when the wind

blows parallel to the ridge. The suction coefficient is about —0.6.

The interior may, however, be subject to full velocity pressure

through broken windows or other openings, and hence the force

coefficient is 1.6. In view of the recommendations of various insur- ance groups, somewhat higher values have been adopted, namely

one and one-fourth those in Section 5-1, Minimum Design Pressures. The highest inward loads on gable roofs occur when the interior

is subjected to full suction. The force on the lee slope is then zero, and the total inward force on the windward slope has been taken

equal to the values in Section 5-1, Minimum Design Pressures, for angles greater than 30°. No inward loads need to be considered

for angles less than 30°.

The combined loadings are based on the recommendations given

in the final report of Subcommittee No„ 31, Committee on Steel of

the Structural Division, American Society of Civil Engineers, published in the ASCE Proceedings, October 1940, part 2, p. 1713-1739.

The subcommittee also gives recommendations for rounded roofs. It is believed that these combined loadings are critical only for certain types of roof trusses. 5-4. Chimneys.^—The value for round chimneys corresponds to

% a shape coefficient of 0.84, which is in good agreement with the windtunnel value 0.8. Hence, the familiar value is retained.

5-5. Signs.—Signs or signboards on the roofs of buildings are exposed

to local wind velocities considerably higher than those of the wind

itself. The increase is produced by the presence of the building.

The reduced value for solid signs on the ground is made in recognition of the decreased velocity pressure to be expected at the limited

height within which such signs are generally erected, and the decreased

risk of signs located at such height. The recommendations for open

signs are based on the work of O. Flachsbart and H. Winter, published in Der Stahlbau, 1934, Nos. 9 and 10, and 1935, Nos. 8, 9, and

10. They take into account the increased load to be expected on the

exposed parts of such signs because of the shape factor of these parts.

6 and 7. Earthquake Loads.—It is hoped that the very moderate

coefficients of lateral load which have been recommended in Section 6, Earthquake Loads—General, together with the fact that they are measured in terms of the dead load only of buildings, and are to be

used with stresses 50 percent greater than the ordinary working

stresses for dead and live load, will make this section suitable for general use. The recommended provisions will give increased

stability of construction with very small increase in cost over that

required for poor or even mediocre construction.

From experience it has been found that certain structural features

will, if incorporated in the construction, give practical and effective

resistance, not only to earthquakes, but to the lateral force of high

winds. Among such structural features are the adequate anchorage

of floors to masonry walls, reinforced-concrete bond beams placed

in the masonry walls just below the floors, and corresponding reinforcedconcrete bond columns placed in the corners of the walls. These

special structural features are particularly important in the more common type of building, represented by the one-story commercial

buildings with brick walls and timber floors and partitions. Schools
Minimum Design Loads in Buildings 27

and churches are examples of buildings of similar construction which

often lack lateral stability and are hazardous in earthquakes or wind

storms. Buildings of this type are often, if not usually, designed and

constructed without the services of a structural engineer. Tall office buildings, on the contrary, are usually designed, insofar as their

structural features are concerned, by structural engineers.

Methods of structural design for resistance to earthquakes are much more complex and consequently more controversial in the case of

tall multistoried buildings than for low commercial buildings. For

the multistoried buildings it seems best that some flexibility in design

should be allowed, with the provision that the design for earthquake

resistance be required to conform to reasonable and logical analysis

and be subject to the approval of the building official. Some experiments made on models of tall buildings indicate that the horizontal

shear factors increase with the number of stories. However, the

committee feels that the range of experiments has not been sufficiently

broad to justify definite recommendations on the subject. For this reason it has been thought best to recommend a constant coefficient for the earthquake factor, as has been done in Section 7-1, Minimum

Lateral Load, of the requirements. Again, due to the probability that

in the majority of buildings the assumed live load is often not realized,

it has been thought best to base the earthquake factor on the dead

load of the building, except in the case of buildings used for storage

purposes, where it is recommended that one-half the live load be

counted as dead load.

With reference to the Rossi-Forel and other scales measuring the

intensity of earthquakes, and to the history of earthquakes in America

and their distribution, attention is invited to the earthquake bulletins

of the Seismological Society of America, and to the earthquake

catalogs of the United States Coast and Geodetic Survey and of the

Seismological Society of America.

The following information provided by the U. S. Coast aud Geodetic

Survey is presented for the information of local code committees:

EAKTHQTJAKES IN THE UNITED STATES

The United States lies partly within the great seismic belt which circumscribes the Pacific Ocean. Practically all parts of the country, however, are subject to earthquakes, as will be seen in figure 3, which shows the distribution and magnitude

of destructive earthquakes within historic time. While the great majority of strong shocks are restricted to rather broadly defined belts, even great earthquakes, such as that at Charleston, S. C, in 1886, may occur in regions generally considered immune on the basis of the historical record. Earthquake map.—Four grades of intensity are indicated on figure 3. The

smallest dots represent either shocks which were strong enough to overthrow

chimneys or shocks, perceptible over more than 25,000 square miles. They may

be either VII or VIII according to the Rossi-Forel scale of earthquake intensity.

(VII indicates the fall of some chimneys, and VIII, IX, and X increasing degrees

of destruction up to and including total destruction.) The larger solid dots may be

associated with damage ranging from several thousand dollars to a hundred

thousand, or to shocks usually perceptible over more than 150,000 square miles. The intensity range is from VIII to IX. The smaller encircled dots represent

damage ranging approximately from a hundred thousand to a million dollars, or an affected area greater than 500,000 square miles. The intensity range is IX to X. The larger encircled dots indicate damage of a million dollars or more, or an

, affected area usually greater than 1,000,000 square- miles. An intensity of X is indicated. The numeral after a dot indicates the number of shocks that have

occurred at or near the location shown. Earthquakes in the border areas of Canada are included as they sometimes result in damage in the United States.
28 Miscellaneous Publications, National Bureau of Standards
Minimum Design Loads in Buildings 29

Quite a few have been felt over very large areas in both countries. This is also true for Mexico. The points of origin of many of the earlier shocks are uncertain. Relation between destructive and -potentially destructive shocks.—Relatively weak

shocks may cause great damage in congested areas while shocks of heavy energy

occurring in uninhabited areas will cause practically no damage. The map must

therefore be viewed as having value in showing in a broad way the potential

earthquake risk in various areas as based on the historical record. Earthquakes of the Pacific Coast and western mountain region are considered shallower than those

in other parts of the country as the ground motions are generally of more destructive character in comparison with those of equal areal extent elsewhere. In the greatest earthquakes, those of the type indicated by encircled dots on the map, damage was great in 10 percent, heavy in 15 percent, considerable in 30

percent, and minor or negligible in 45 percent of the total number. In veiy strong

shocks, indicated by the large dots, damage was great in 10 percent, heavy in 20

percent, considerable in 27 percent, and minor or negligible in 43 percent. In

strong shocks, those in the small dot category, damage was heavy in 1 percent, considerable in 9 percent, and minor or negligible in 90 percent. In this appraisal,

damage over a million dollars is considered great; a hundred thousand dollars or

over, heavy; over ten thousand dollars, considerable; and anything less, minor.

More than half of the shocks of destructive intensity in the country have occurred

in the Pacific Coast and western Nevada area. References.—This summary is based on reports and records of the United States Coast and Geodetic Survey, principally Serial 609, Earthquake History of the United States, Part I—Continental United States (Exclusive of California and

Western Nevada) and Alaska; Part II—Stronger Earthquakes of California and

Western Nevada. More detailed information will be found in those reports and

in the annual Seismological reports of the Survey. Special reference is made to the January 1939 number of the Bulletin of the Seismological Society of America

containing a " Descriptive Catalog of Earthquakes of the Pacific Coast of the United States, 1769 to 1928," by S. D. Townley and M. W. Allen. A comprehensive review and discussion of the earthquake problem in the United States from the insurance and engineering viewpoints is "Earthquake Damage and

Earthquake Insurance" by J. R. Freeman (McGraw-Hill Book Co., Inc., New

York and London, 1932).

General.—While only about 275 shocks are indicated in figure 3, the actual number of shocks of all types, felt and unfelt, runs into the thousands annually. As many as a million have been suggested* for the earth as a whole. Neither their ultimate nor immediate cause is known although plausible hypotheses have been

advanced, especially in regard to their immediate cause. They cannot be pre- dicted with respect to time and place. Analyses of available statistics have not

revealed any periodicity factors of practical value in predicting. Since 1933 the Coast and Geodetic Survey has made instrumental observations

of destructive ground motions. Although the application of this information to the design of structures is handicapped by the need for further laboratory research and more satisfactory analytical methods, progress is being made through the

active participation of several engineering research organizations in this special- ized field. There is indication that the complex stresses set up in structures during destructive earthquake motions can be expressed, in terms of equivalent

static forces. Pending the successful completion of this research and the accumulation of sufficient instrumental records of destructive ground motions, the engi- neer must depend largely on empirical formulas such as recommended in Sections

6 and 7.
30 Miscellaneous Publications, National Bureau of Standards

Important earthquakes of the United States and adjoining regions

Year R-F in- tensity Remarks

1638

1663

1732

1755

1769

1790

1811

June 1

Feb. 5

Sept. 15 Nov. 18

July 28

(?)

a Dec. 16

1812 1812

1839

1857

1868

1870 1872

1886

Dec. 8 Dec. 21

(?) Jan. 9

Oct. 21

Oct. 20 Mar. 26

Aug. 31

Mass., Plymouth.

Canada, Three Rivers,

Lower St. Lawrence

River. Canada, Ontario

Mass., near Cambridge.

Calif., San Pedro Channel area.

Calif., Owens Valley. _ Mo., New Madrid

VIIIX

IX?

IX

Calif., San Juan Capistrano.

Calif., near Lompoc__

Calif., Redwood City

Calif., Fort Tejon___

IX

X

IX?

X

Calif., Hayward.

Canada, Montreal to Quebec.

Calif., Owens Valley. _

S. C, Charleston.

IX

X

X

Many stone chimneys down.

Chimneys down in shocks

in 1662 and probably other

years. Chimneys broken in Mass. Bay area. 7 killed at Montreal. Many chimneys down, brick

buildings damaged, stone

fences generally wrecked. Sand emitted from ground

cracks. Felt from Chesapeake Bay to Annapolis,

Nova Scotia. Major disturbance with many

aftershocks. Major shock with appearance

of fault scarps. Greatest United States earth- quake in historic time. Town

destroyed, great changes in configuration of ground and

rivers including the Mississippi River. Chimneys down

in Cincinnati. Felt in Boston. Several killed. Church collapsed killing 40. Churches and other buildings

wrecked in several towns in- cluding Santa Barbara.

Possibly thousands of redwoods

broken off. Probably greatest of Pacific Coast shocks. Originated in NW corner of Los Angeles

Co. Buildings and large

trees thrown down.

Many buildings wrecked,

nearly all damaged. Severe damage at San Leandro and

San Francisco. 30 killed. Widespread. Minor damage

on coast of Maine.

One of 3 greatest earthquakes

in Pacific Coast area. 23-

foot fault scarp formed. 27

killed at Lone Pine out of 300 population; all adobe

houses wrecked.

Greatest earthquake in east- ern part of country. 102

buildings destroyed; 90 per- cent damaged; nearly all chimneys down. $5,500,000

damage. About 100 killed. Felt at Boston, Chicago and

St. Louis.
Minimum Design Loads in Buildings 31

Important earthquakes of the United States and adjoining regions—Continued

Year Date Place R-Fin

tensity Remarks

1887

1895

1899

1906

May 3

Oct. 31

Dec. 25

Apr. 18

Mexico. Sonora.

1909

1915

1915

1925

1925

1925

1929

1929

1931

1931 1932

1933

May 26 June 22

Oct. 2

Feb. 28

June 27

June 29 Aug. 12 Nov. 18

Apr. 20 Aug. 16 Dec. 20 Mar. 10

Mo., near Charleston.

Calif., San Jacinto.

X

IX

Calif., San Francisco.

111., Aurora

Calif., Imperial Valley.

Nev., Pleasant Valley __

Canada, Murray Bay___ Montana, Manhattan. _

Calif., Santa Barbara. N. Y Attica___

Grand Banks, off Newfoundland.

N. Y., Lake George,

Texas, near Valentine. _ Nev., Cedar Mountain.

Calif., Long Beach

VIII IX

X

IX

IX

IX

X

VIII IX

X

IX

Widespread in border states. Chimneys down in several towns including El Paso and

Albuquerque.

Felt in Canada, Virginia, Louisiana and South Dakota.

Acres of ground sank and

lake formed. Many chimneys demolished.

Nearly all brick buildings badly

damaged in San Jacinto and Hemet. Chimneys down in Riverside. 6 killed. Another severe shock in 1918. Great earthquake and fire. About 95 percent of esti- mated $400,000,000 damage

due to fire. 700 killed. Greatest destruction in San

Francisco, Santa Rosa, and

other towns near San Andreas fault. Horizontal slip- ping along fault, 21 feet. Greatest damage on made

land. Many chimneys down. Felt over wide area. Nearly $1,000,000 damage. 6

killed. Well-constructed

buildings were cracked. Widespread. Adobe houses and water tank towers

wrecked.

Felt in many eastern and central states. Damage less than $100,000.

Landslide blocked entrance to

railroad tunnel. Some build- ings wrecked and many

chimneys fell. $300,000 damage. $6,000,000 damage. 13 killed. 70 buildings condemned.

250 chimneys toppled.

Submarine shock broke 12

transatlantic cables; some

breaks 150 miles apart. Some deaths by seismic sea wave along Burin Peninsula. Some chimneys in Canada

toppled.

Chimneys fell. All buildings damaged; many

chimneys fell. In sparsely settled region.

Widespread.

$4 L000, 000 damage; 120 killed. Fire damage insignificant. Greatest strictly earthquake

damage in country.
32 Miscellaneous Publications, National Bureau of Standards

Important earthquakes of the United States and adjoining regions—Continued

Year Date Place R-F in tensity Remarks

1934

1935

1935

1941 1941 1944

Mar. 12 Nov. 1 Oct. 18

June 30 Nov. 14

Sept. 5

Utah, Kosmo.

Canada, Timiskaming.

Montana, Helena

Calif., Santa Barbara _ Calif., Torrance-Gar- dena area. Canada-New York,

Cornwall and Massena.

IX

IX

IX

IX

VIII IX

Marked changes in terrain north of Great Salt Lake. 2

killed. Widespread. Landslide near

origin.

$3,500,000 damage. 4 killed;

less than 50 injured. More

than half of buildings damaged from 2.5 to 100 percent. $100,000 damage.

About $1,000,000 damage. 50

buildings severely damaged.

On St. Lawrence River. $1,-

500,000 damage reported. 90 percent of chimneys in Massena destroyed or damaged.

Washington, April 26, 1945.

o