UNITED STATES DEPARTMENT OF COMMERCE

ELIMINATION OF WASTE SERIES

M LIVE LOADS ALLOWABLE

FOR USE IN DESIGN OF BUILDINGS

111

||>-. REPORT

OF BUILDING CODE COMMITTEE

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UNITED STATES DEPARTMENT OF COMMERCE

HERBERT HOOVER, SECRETARY ELIMINATION OF WASTE SERIES

MINIMUM LIVE LOADS ALLOWABLE

FOR USE IN DESIGN OF BUILDINGS

REPORT OF

BUILDING CODE COMMITTEE

NOVEMBER 1, 1925

Ira H. Woolson, Chairman

Edwin H. Brown Rudolph P. Miller William K. Hatt John A. Newlin

Albert Kahn Joseph R. Worcester

Frank P. Cartwright, Technical Secretary JOHN M. CRIES, Chief

Division of Building and Housing

BUREAU OF STANDARDS

PRICE, 10 CENTS

Sold only by the Superintendent of Documents, Government Printing Office Washington, DC. '

WASHINGTON GOVERNMENT PRINTING OFFICE

1925
MEMBERSHIP OF THE BUILDING CODE COMMITTEE

OF THE DEPARTMENT OF COMMERCE

Iha H. Woolson, Chairman, Consulting Engineer, National Board of Fire Underwriters, New York City; Member, American Society of Mechanical Engineers; American Society for Testing Materials; National Fire Protection

Association; American Concrete Institute. Edwin H. Brown, Architect, Minneapolis, Minn.; Secretary, American Insti- tute of Architects; Member, American Institute of Architects. William K. Hatt, Professor of Civil Engineering, Purdue University; Member,

American Society of Civil Engineers; American Concrete Institute. Albert Kahn, Architect, Detroit, Mich.; Fellow, American Institute of Architects. Rudolph P. Miller, Consulting Engineer, New York City; Past President, Building Officials Conference; Member, American Society of Civil Engineers; American Institute of Consulting Engineers; American Society for Testing Materials. John A. Newlin, In charge of Section of Timber Mechanics, Forest Products

Laboratory, Forest Service, United States Department of Agriculture, Madison, Wis.; Member, American Society for Testing Materials; American

Society of Civil Engineers. Joseph It. Worcester, Consulting Engineer, Boston, Mass.; Member, American

Society of Civil Engineers; American Institute of Consulting Engineers. Frank P. Cartwright, Technical Secretary.
CONTENTS

PART I.—INTRODUCTION

Page

Investigations 2 Present methods uneconomical 3 PART n.—MINIMUM LIVE LOADS ALLOWABLE FOR USE IN DESIGN

OF BUILDINGS

Section 1. Definitions 5

1. Dead load 5

2. Live load 5

2. General 5

3. Human occupancy 5

4. Industrial or commercial occupancy 6

5. Roof loads 6

6. Allowance for movable partition loads 6

7. Reductions in live loads 7

8. Wind pressures 7

9. Live loads to be posted 7 10. Occupancy permits 8 PART in.—APPENDIX

Paragraph 1. Purpose 9

2. Influence of building inspection 9

3. Status of recommendations 9

4. Present, code requirements 10

5. Loads due to human occupancy 12

1. Residential occupancies 12

2. Hospitals 12

3. Schools 13

4. Grandstands 13

5. Offices 13

6. Library stack rooms 17

7. Crowded rooms 17

6. Floor loads in industrial and commercial buildings IS

7. Roof loads 28

8. Partition loads 28

9. Reduction of live loads 29

10. Wind pressures 30

11. Floor-load placards 32

12. Occupancy permits 33

13. Impact allowances 34

14. Effects of lighter load assumptions on general stability. _ 37

15. Load assumptions unrelated to stress requirements 37

16. Weight of construction materials. 37 hi
IV CONTENTS

TABLES Table 1. Table 2. Table 3. Table 4. Table 5. Table 6. Table 7. Table 8.

Minimum floor-load requirements allowed as a basis of structural design in the United States Weights of merchandise in warehouse of wholesale hardware company

Floor loads in storage buildings Floor loads in manufacturing buildings Data on live loads resulting with use of steel furniture Dimensions and weights of typical trucks Recorded wind velocities in various American cities Extensometer investigation of live load and impact stresses due

to crowded loadings on balcony of the gymnasium of Iowa

State College-.. ILLUSTRATION

Fig. 1. Floor-load placard.

Page1120

22

23

26

27

31

35

33
LETTER OF SUBMITTAL

Washington, D. C., November 1, 1924. Hon. Herbert Hoover,

Secretary of Commerce,

Washington, D. C. Dear Sir: In further prosecution of the program of the Building Code Committee appointed by you to simplify building code require- ments, I have the honor to present its report on Minimum Live Loads

Allowable for Use in Design of Buildings. .This is the fourth in the

series. Existing floor-load requirements as found in building codes are in an unsettled condition. A variation of 100 per cent in allowable

floor loads for the same occupancy in different cities is common, and

disparities of 200 and 300 per cent are found. Such variations are without justification. Unnecessarily high requirements in respect to

floor loads are a financial burden upon the builder and lead to a waste of materials. The recommendations of Part II, while occupying but a few pages

are the essence of the report. The committee believes the live loads recommended as a basis for design are conservative and safe, although

frequently they are considerably lower' than those in current use in many municipalities. Their general adoption will materially lessen the cost of buildings. The appendix contains a digest of the original studies made for the committee and of all similar available information. The committee

believes it to be the best and most complete accumulation of live-load data thus far published. The report is submitted for your approval with the recommendation

that it follow the usual procedure as to publication. Yours very truly, Ira H. Woolson,

Chairman, Building Code Committee, Department of Commerce.
LETTER OF ACCEPTANCE

Department of Commerce,

Office of the Secretary,

Washington, D. C., December 19, 1924. Mr. Ira H. Woolson,

Chairman, Building Code Committee, Department of Commerce, Washington, D. C. My Dear Mr. Woolson: I am most happy to receive the report

of the Building Code Committee on minimum live loads allowable

for use in the design of buildings. I have directed that it be published

in the elimination of waste series of the Department of Commerce.

These recommendations of the committee make possible, I believe, savings of millions of dollars a year for the American people, and

thus contribute toward a higher standard of living. The report is, however, significant in other ways. It demonstrates once more the willingness of American professional men to devote their time and energies to public service, and the readiness with which a well-accredited group can obtain the cooperation of hundreds of others in such an undertaking. Another most important contribution that is being made by your

committee, in addition to placing the design of buildings on a more

scientific basis, is to emphasize the real saving that a thorough and

efficient municipal inspection of building construction makes possible. With an inspection service of a high order, and well framed

codes, the great majority of competent engineers, architects, and

constructors are enabled to make the best use of their skill in design and quality of workmanship. With good inspection there is no

occasion to penalize these able and honest persons by requirements

for excessive use of materials that are sometimes specified as a partial measure of protection for the public from the ignorance and neglect

of incompetent and irresponsible persons.

I have no hesitation in thanking you, in behalf of the American

public, for your laborious efforts in the preparation of this report. Yours faithfully, Herbert Hoover
RECOMMENDED MINIMUM LIVE LOADS ALLOWABLE FOR USE IN DESIGN OF BUILDINGS

This report is divided into three general headings, as follows: Part I.—Introduction: Describes briefly the organization of the committee and its method in preparing and presenting the recommendations. Part II.—Minimum Live Loads Allowable for Use in Design of Buildings : These are briefly stated in the form of recommendations

suitable for municipal adoption. Part III.—Appendix: A compilation of live-load data and of material not suited for incorporation in a building law, but which

is explanatory of the requirements recommended in Part II and

descriptive of good practice. PART I.—INTRODUCTION

The Department of Commerce Building Code Committee was

organized early in 1921, in recognition of a general public demand for greater uniformity and economy in building code requirements. Its

first work was concerned with regulations affecting construction of small dwellings, and the final report on this subject was published in January, 1923.1 Early in the committee’s work the question was raised of code

variations regarding live loads, and efforts were made to collect data on actual loads which might be used in drafting recommendations. Investigation disclosed that very little had been published on this important subject, and showed wide variation in the mini- mum floor, roof, and wind loads for which buildings are required to be designed by building codes. The extent of this variation, if the

significance of the values be admitted, indicates either that safety

is disregarded in many cases or that an unnecessary amount of building materials or labor is used because of these laws. (See Appendix, par. 4.) It was found that live loads assumed in designing many types

of buildings were largely matters of tradition and had scant scientific

> Recommended Minimum Requirements for Small Dwelling Construction, 15 cents. Other reports issued are: Recommended Minuraum Requirements for Masonry Wall Construction; and a report on Recommended Minimum Requirements for Plumbing in Dwellings and Similar Buildings, prepared by

an associated committee of sanitary engineers, 35 cents. These publications are obtainable from the Superintendent of Documents, Government Printing Office, Washington, D. O-
2 RECOMMENDED MINIMUM REQUIREMENTS

basis. The result was that accuracy in stress computations was

defeated because of ignorance of the loads causing stresses. The

building professions for years have busied themselves with tests of materials, but have given little attention to this complementary

factor of loads-. This report presents load requirements recommended for general adoption with the object of preserving safety, stimulating uni- formity of requirements, and effecting conservation of materials and labor. Investigations As a preliminary step the committee compiled the live-load require- ments of 109 existing codes. These were referred to the building

officials in the respective cities and checked to ascertain if they

represented current practice. The compilation was then submitted

to a number of experienced architects and their discussions of the

subject were made the basis of still further inquiries. (See Appendix, par. 4.) Through the courtesy of several technical and industrial organizations, particularly through the efforts of members of the American

Institute of Architects, the National Association of Building Owners

and Managers, and the American Warehousemen’s Association, information has been obtained on live loads characterizing a number

of typical occupancies. An extensive investigation of office floor loads was made for the committee by C. T. Coley, manager of the Equitable - Office Building in New York, N. Y., and the results published in a number of journals. This stimulated others to similar

efforts. C. H. Blackall, of Boston, had already reported floor loads found in a large office building in that city, thereby affording a comparison with similar investigations made by him at an earlier date. Studies by M. W. McIntyre of office floor loads; by the Hotels

Statler Co.; by the Turner Construction Co., in warehouses; and

analyses by R. Fleming, of the American Bridge Co.; by C. Heller,

of San Francisco; by Norman Stineman, of the Portland Cement

Association; and by J. D. M. Phillips, secretary, National Association of Steel Furniture Manufacturers, have been exceedingly helpful

in the preparation of this report. B. C. Kadel, of the United States Weather Bureau, assisted in preparation of the material on wind

velocities and pressures. With this information in hand, and with due reference to the

structural elements involved, the committee prepared a tentative

draft of recommended live load assumptions. This was submitted

to over 500 carefully selected architects, engineers, building officials, and others qualified to discuss the subject with authority. About

125 letters were received from these men discussing the committee’s
MINIMUM LIVE LOADS FOR BUILDING DESIGN 3

proposals from many angles and affording a valuable basis for re- vision of the report into fuller agreement with the best information and practice. Present Methods Uneconomical.

Floor live-load requirements in codes are expressed as a minimum

for which buildings for each class of occupancy must be designed and built, and are intended to protect occupants and owners from

loss of life or property through partial or total structural failure. In most codes these occupancy classes are few, and commercial and

industrial classes in particular include under the same minimum

requirement many diverse occupancies with varying characteristic

loads. Inspection practice in the great majority of cities does not

insure control of occupancy changes, nor does it involve periodical attention to make sure that design loads are not exceeded. It has re- sulted from these conditions that the minimum allowable load for all occupancies in a class approaches that which is considered safe for the

heaviest occupancies in that class. A considerable increment also is attributable to the desire to provide for unreported occupancy changes and unsupervised loading conditions. Code requirements in many

cases are, in fact, framed to secure buildings strong enough to endure whatever changes of use may occur, whether or not reported to the

building official. The builder who erects a structure under such drastic code require- ments is directly penalized for the city’s failure to provide inspection

of the two types mentioned above.

It is desirable as a safety measure to regulate the live loads for which a building is designed and it is just as necessary to make sure

thereafter that these loads are not exceeded. If adequate supervision of subsequent loadings is obtained, the provision of an initial surplus is unnecessary. Certain classes of buildings are distinguished by loads so light or so uniform in nature as to require no further

attention after construction. Office and residence buildings fall in

this class. Others, as shown by observations reported to the committee, are so often subject to overloads that a blanket requirement

affecting design only, no matter how drastic in nature, is insufficient for safety unless the use of each building is watched. If floor loads and occupancy changes are controlled throughout the life of the building, it is possible to adopt the policy requiring each building merely

to be strong enough for its intended use. This requires more complete information than is now current as to the floor loads which

various occupancies involve, and an attempt is made in this report

to present a nucleus of such data. Zoning ordinances, now generally being adopted by cities, require the reporting of occupancy

30868°—25f 2
4 RECOMMENDED MINIMUM REQUIREMENTS

changes to the authorities and should make the control measures

described above much easier than in the past. In drafting its recommended floor-load requirements, the Building Code Committee has given weight to all these considerations. For

occupancies having a low maximum live load, or in which live loads

are practically uniform, a minimum limit has been prescribed for which buildings of these specific occupancies should be designed. Other buildings, subject to heavy floor loads or those not necessarily uniform in amount are required to be designed for loads ap- proaching the maxima which characterize the proposed occupancy, and it is recommended that such buildings be periodically inspected

after construction.
PART II.—MINIMUM LIVE LOADS ALLOWABLE FOR USE

IN DESIGN OF BUILDINGS

Section 1. Definitions.

1. Dead load. —The dead load in a building includes the weight of walls, permanent partitions, framing, floors, roofs, and all other per- manent stationary construction entering into a building. (See Appendix, par. 16, for weights of construction materials.)

2. Live load.'—The live load includes all loads except dead loads. Sec. 2. General. Buildings and all parts thereof shall be of sufficient strength to support safely their imposed loads, live and dead, in addition to their own proper dead load; provided, however, that no building or part of a building shall be designed for live loads less than those specified in the following sections. (See Appendix, par. 13, for impact considerations.) Sec. 3. Human Occupancy.

1. For rooms of private dwellings, hospital rooms and wards, guest rooms in hotels, lodging and tenement houses, and for similar occupancies, the minimum live load shall be taken as 40 pounds per square

foot uniformly distributed, except that where floors of one and two

family dwellings are of monolithic type or of solid or ribbed slabs the

live load may be taken as 30 pounds per square foot. (See Appendix,

par. 5, 1 and 2.)

2. For floors for office purposes and for rooms with fixed seats, as in churches, school classrooms, reading rooms, museums, art galleries, and theaters, the minimum live load shall be taken as 50 pounds per square foot uniformly distributed. Provision shall be made, however, in designing office floors for a load of 2,000 pounds placed upon

any space 2^ feet square wherever this load upon an otherwise unloaded floor would produce stresses greater than the 50-pound dis- tributed load. (See Appendix, par. 5, 3, 4, and 5.)

3. For aisies, corridors, lobbies, public spaces in hotels and public

buildings, banquet rooms, assembly halls without fixed seats, grandstands, theater stages, gymnasiums, stairways, fire escapes or exit passageways, and other spaces where crowds of people are likely to assemble, the minimum live load shall be taken as 100 pounds per square foot uniformly distributed. This requirement shall not apply, however, to such spaces in private dwellings, for which the minimum

live load shall be taken as in paragraph 1 of this section. (See Appendix, par. 5, 7.) 5
6 RECOMMENDED MINIMUM REQUIREMENTS

Sec. 4. Industrial or Commercial Occupancy.

In designing floors used for industrial or commercial purposes, or purposes other than previously mentioned, the live load shall be assumed as the maximum caused by the use which the building or part of the building is to serve. The following loads shall be taken

as the minimum live loads permissible for the occupancies listed, and

loads at least equal shall be assumed for uses similar in nature to those listed in this section. Minimum

Floors used for: (ibjtu) Storage purposes (general) 250

Storage purposes (special) 2 100 Manufacturing (light) 75

Printing plants 3 100 Wholesale stores (light merchandise) 100

Retail salesrooms (light merchandise) 75

Stables 75 Garages

All types of vehicles 100 Passenger cars only 80 Sidewalks—250 or 800 pounds concentrated, which ever gives the

largest moment of shear. (See Appendix, par. 6, for live-load data, especially divisions 3, 4> and 5 for discussion of considerations involved in design for light loads in commercial buildings.) Sec. 5. Roof Loads. Roofs having a rise of 4 inches or less per foot of horizontal projection shall be proportioned for a vertical live load of 30 pounds per square foot of horizontal projection applied to any or all slopes. With a rise of more than 4 inches and not more than 12 inches per

foot a vertical live load of 20 pounds on the horizontal projection

shall be assumed. If the rise exceeds 12 inches per foot no vertical

live load need be assumed, but provision shall be made for a wind

force acting normal to the roof surface (on one slope at a time) of 20 pounds per square foot of such surface. (See Appendix, par. 7.) Sec. 6. Allowance for Movable Partition Loads.

Floors in office and public buildings and in other buildings subject to shifting of partitions without reference to arrangement of

floor beams or girders shall be designed to support, in addition to other loads, a single partition of the type used in the building, placed

in any possible position. (See Appendix, par. 8.)

» See Appendix, par. 5, 8.

1 See Table 4, item 9.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 7

Sec. 7. Reductions in Live Loads. Except in buildings for storage purposes the following reductions

in assumed total floor live loads are permissible in designing all columns, piers or walls, foundations, trusses, and girders. (See Appendix, par. 9.) Reduction of total live loads carried

Per cent Carrying one floor 0 Carrying two floors 10 Carrying three floors 20

Carrying four floors 30

Carrying five floors 40

Carrying six floors 45 Carrying seven or more floors 50 For determining the area of footings the full dead loads plus the

live loads, with reductions figured as permitted above, shall be taken; except that in buildings for human occupancy, listed in section 3, a further reduction of one-half the live load as permitted above may

be used. Sec. 8. Wind Pressures. For purposes of design the wind pressure upon all vertical plane

surfaces of all buildings and structures shall be taken at not less than

10 pounds per square foot for those portions less than 40 feet above

ground, and at not less than 20 pounds per square foot for those portions more than 40 feet above ground. The wind pressure upon sprinkler tanks, sky signs, or upon similar exposed structures and their supports shall be taken at not less than

30 pounds per square foot of plane surface, acting in any direction. In calculating the wind pressure on circular tanks or stacks this pressure shall be assumed to act on six-tenths of the projected area. Where it shall appear that a building or structure will be exposed

to the full force of the wind throughout its entire height and width

the pressure upon all vertical surfaces thus exposed shall be taken at not less than 20 pounds per square foot. (See Part II, section 5, roof loads. See also Appendix, par. 10.) Sec. 9. Live Loads to be Posted. The live loads for which each floor, or differing parts thereof, of a commercial or industrial building is designed shall be certified by

the building official and shall be conspicuously posted in that part

of each story where they apply, using durable metal signs. The

occupant of the building shall be responsible for keeping the actual loads below the certified limits. Adequate measures shall also be

taken by the building official to insure that these loadings are not

exceeded. (See Appendix, par. 11.)
8 RECOMMENDED MINIMUM REQUIREMENTS*

Sec. 10. Occupancy Permits. Plans for other than residential buildings filed with the building

official with applications for permits shall show on each drawing the

live loads per square foot of area covered, for which the building is designed, and occupancy permits for buildings hereafter erected shall not be issued until the floor-load signs required by section 9 have

been installed. No change in the occupancy of a building now existing or hereafter erected shall be made until a revised occupancy permit

has been issued by the building official certifying that the floors are suitable for the loads characteristic of the proposed occupancy. (See Appendix, par. 12.)
PART III.—APPENDIX

Par. 1. Purpose. The Appendix consists of explanatory matter referring to Part II and is a vital pait of this report. The committee believes that every

building code should be accompanied by an appendix, which should

contain sufficient explanation of the code requirements to make

them easily understandable, and such other information on good

practice as can not be obtained elsewhere in concise form.

Par. 2. Influence of Building Inspection.

It is recognized that the requirements recommended in Part II constitute in most particulars relaxations from those in force in certain cities and parts of the country. In the committee’s opinion

these modifications of existing practice are justified by the facts developed through its investigations. In addition to the live-load data presented in this report, and which establishes clearly that

existing requirements are too high for some occupancies, the experi- ence is reported of several large cities which supervise live load assumptions for building design by the method recommended in Part II. This method involves three essential steps: (1) The

requirement by the code of a low minimum live load for each class of occupancy, (2) the requirement by the building official of higher

design loads where the prospective occupancy obviously involves such loads, and (3) the periodical inspection of buildings housing

certain classes of occupancy to prevent undue overloads. The success of this procedure in many places answers satisfactorily the objections to its adoption in localities where code requirements

are now more conservative. It should be understood that the code

requirements in Part II are recommended only where responsible supervision of loadings and good materials and workmanship are assured. Without such supervision mere requirements for loading

will not insure safe construction. Par. 3. Status of Recommendations.

1. It has been called to the committee’s attention that some

misunderstanding exists with regard to the legal status of its recommendations. It should be recognized that the committee’s functions

are purely advisory. The recommendations can not be considered

in any sense as obligatory, but are issued to make available to those

locally responsible for exercise /f the police power the consensus

of public opinion on this phase of building regulation.

9
10 RECOMMENDED MINIMUM REQUIREMENTS

2. The recommended code requirements are in all cases the minimum consistent with safety. The scope of the police power, upon which all such ordinances depend for authority, does not

justify requirements which are merely good building practice. Par. 4. Present Code Requirements.

Early in the committee’s work on live loads an extensive investi- gation was made of existing floor-load requirements. The provisions

of 109 building codes were carefully examined and their application

in local practice checked by correspondence with building inspectors. The results of this work are summarized in Table 1. The limits commonly in force for industrial and commercial occupancies should be considered by designers in connection with the data presented

in Appendix, paragraph 6. Table 1 appeared in the following

journals: Buildings and Building Management, May 14, 1923; American Architect and Architectural Review, May 9, 1923; Safety

Engineering, May, 1923; The Constructor, June, 1923; and Engineering News-Record, August 16, 1923.
Table

1.

—

Minimum

floor-load

requirements

allowed

asa

basis

of

structural

design

in

the

United

States

[Analysis

of

building

code

requirements

of

109

representative

cities

of

the

United

States

showing

number

in

which

each

of

the

following

minimum

loadings

are

specified

for

the

occupancies

listed.

United

States

Department

of

Commerce,

Building

Code

Committee,

December,

1922]

MINIMUM

LOAD

IN

POUNDS

PER

SQUARE

FOOT

MINIMUM LIVE LOADS FOR BUILDING DESIGN 11
12 RECOMMENDED MINIMUM REQUIREMENTS

Par. 5. Loads Due to Human Occupancy.

1. Residential occupancies. —After investigating the floor loads in residences the Building Code Committee recommended in an earlier report (Minimum Requirements for Small Dwelling Construction) that a live load of 40 pounds be required for small dwellings with wood floors and 30 pounds for those having solid or ribbed monolithic

floors. Through submission of a preliminary report on the subject opportunity was made for critical discussion of the suggestion, with

the result that it received practically unanimous approval. The heaviest furniture loads discovered by investigators were pianos, weighing up to 55 pounds per square foot, and bookcases weighing up to 170 pounds per linear foot, but in both cases the distribution was such as to bring the equivalent uniform load well below that

specified above. According to information furnished by the Hotels

Statler Co. the complete furniture of a typical guest room weighs 812 pounds, or about 4.1 pounds per square foot for an 11 by 18 foot room. The reported observations of several experienced architects and

builders are that the furniture loads in residential occupancies will seldom exceed 50 per cent of the minimum design load specified, but

that crowds averaging 40 pounds per square foot are quite probable and should be provided for. For the average requirements of 109 codes in respect to the occupancies mentioned above, see Appendix, paragraph 4. It will be

noted that the average for hotel guest rooms is but 7.6 pounds heavier than that for corresponding parts of dwellings, and but 6.7 pounds

heavier than for tenements, indicating that loads for these three occupancies are generally considered about the same.

2. Hospitals. —Through the courtesy of those in charge of the New

York State hospitals for the insane at Brooklyn and Rochester,

actual live-load measurements were obtained for several large wards

in each institution. The data are as follows:

Live loads in crowded wards BROOKLYN STATE HOSPITAL

Ward number Dimensions

Total number of beds

Average

weight

of bed

equip- ment and

occupant

Total

floor load Load

per square

foot

8 and 10 1 43 feet by 58 feet 62 Pounds

275 Pounds

17, 050 Pounds6.9

65 275 17, 875 7.2

21 dormitory 1 do 62 295 18, 290

19, 175

7.3 22 dormitory 1 65 295 7.7 ROCHESTER STATE INSANE HOSPITAL

9, east 3 49 feet 6 inches by 34 feet 6 inches 46 256 11, 776 6.9

9, west 3 50 feet by 34 feet 6 inches 52 256 13,312 9,936

7.7 52 3 48 feet by 28 feet 36 276 7.5

53, dormitory 1

3 36 feet by 47 feet 276 11, 868 7.0

53, dormitory 2

3 21 feet by 36 feet 18 276 6.6

53, dormitory 3

3 49 feet by 28 feet 45 276 12] 420 9.0

1 Wards 8, 9, and 10, females, average weight, 145 pounds; dormitories 21 and 22, males, average weight,

165 pounds. Radiators not included.

1 Ward 9, females, average weight, 130 pounds; wards 52 and 53, males, average weight, 150 pounds. Radiators not included.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 13 A survey of a large dormitory in the Willard, N. Y., State hospital checks the above figures very closely. The room accommodated 86

beds in a total area of 2,600 square feet. The live loads were as

follows:

Pounds 86 beds, at 85 pounds each 7, 300

86 mattresses, etc., at 45 pounds 3, 870

86 patients, at 135 pounds 11, 600

Total load.. 22, 770 Average load per square foot 8. 75

8. Schools. —According to investigations by Norman M. Stineman

(American Architect, April 11, 1923) a standard classroom has 736

square feet area and accommodates 45 pupils. The average weight

of furniture and inmates is about 7,500 pounds, or 10 pounds per

square foot. He estimates the maximum possible load as 2 adults in each seat and 30 around walls, giving total live load of 28 pounds

per square foot. In the course of loading tests for schoolhouse floors made by the Milwaukee Board of Education (Engineering News-Record, May 6, 1920) a room 24 feet 5 inches by 32 feet (781.3 square feet) normally

for the accommodation of a teacher and 48 pupils was crowded with 258 pupils, filling all seats double, and all aisles and open spaces. There resulted a total weight per square foot, including desks, of 41.7 pounds. Under normal conditions with 48 pupils at an average weight .of 115.6 pounds, plus weight of desks and teachers, the average floor load was 10.83 pounds per square foot. Filled under normal condition! with adults, as in the case of night school, the load amounted to

12.9 pounds per square foot. Other investigators put the live load in school classrooms normally

filled at 14 pounds per square foot, and at 22 pounds if the aisles are crowded.

4- Grandstands. —Even with due allowance for increased weight

of adults the limits given in Part II, section 3, for schools, are believed to apply also for other indoor places of assembly with fixed

seats. Grandstand seats are more closely spaced, the supporting

structure is more open to deterioration by action of the elements, and there is greater prospect of serious impact effects from moving

crowds. (See appendix, par. 13.) The minimum load for such struc- tures was, therefore, increased considerably over that for indoor assembly places.

5. Offices. —The information available on this occupancy is much

more complete than for any other. It has been carefully presented
14 RECOMMENDED MINIMUM REQUIREMENTS

in recent technical periodicals 4 and only a resume sufficient to support the committee’s recommendations is included here. Actual weights of furniture and occupants on three complete

floors and in a number of selected heavy occupancies in the Equitable

Building, New York, N. Y., are reported by C. T. Coley, manager of the building, as follows: Maximum, minimum, and average live loads in Equitable Building

Offices Maximum Minimum Average

Light-occupancy floor (twentieth) 07 Lbs./ft* 55.4

Lbs./ft* 0.87Lbs./ft*

10. 20 Medium-occupancy floor (thirty-seventh) 64 30. 73 3.27 10. 67 Heavy-occupancy floor (eleventh) 62 33.84 5.00 13. 96 Total and average 193 11.8 Selected heavy occupancies throughout building 14 78.3 21.4 42.4 The weights given do not include the radiators, which would add

approximately 1 pound per square foot for all exterior bays. The weight of the partitions was not included in the calculations. These, in general, are 3-inch hollow tile plastered each side, and one which was being removed was found to weigh 30 pounds per square

foot, or approximately 350 pounds per linear foot. The weight of occupants, taken at 150 pounds per person, is probably high, as most of the occupants are females, and some

studies indicate that an average weight of same would not exceed

120 pounds.

Careful sketches of load arrangement prepared by Mr. Coley

made it possible to throw some light on the prevailing method of assuming uniformly distributed live loads as a basis for office floor design, and help to indicate what relation such assumptions should bear to actual total loads. Examination of bays for which the live load was more than 25 pounds per square foot showed wide variation

in the distribution of such loads. The larger proportion was found,

as might be expected, within a zone approximately 3 feet wide around

the walls, the remainder being distributed variously in the centers of the rooms. In one or two cases, however, the major portion of the load was located away from the walls and this condition must be

provided for by designers. There is also the probability that practically all furniture may be collected in the central portion of a floor area when occupants are moving, or when decorating or cleaning

is in progress. The sketches show that the heavier loads, such as library shelves and double filing cabinets, are likely to be located away from walls

4 An article on “Live loads in office buildings, ” based on data obtained by Mr. Coley and other investi- gators, appeared in the following journals: Engineering News-Record, March 29, 1923; American Architect and Architectural Review, March 28, 1923; Concrete, April, 1923; American Machinist, March 22, 1923; Distribution and Warehousing, April, 1923; Architectural Forum, April, 1923; and Buildings and Building Management, March 19, 1923.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 15

and partitions. This is obviously for ease of access, and the same

consideration demands that when total loads per square foot are high they must be quite uniformly distributed. The heaviest loading discovered was one incidental to office purposes, being made up chiefly of card filing cases, but the stack room of a law library on one floor would have averaged 87 pounds

per square foot if the shelves had been completely filled. Only eight articles of furniture (safes) were found over 2,000 pounds

in weight. A number of sectional filing cases and bookcases with

contents weighed much more, but these weights were distributed over such a large area they could not be regarded as concentrated. Of 36 safes and safe cabinets, 23 weighed less than 1,000 pounds;

5 between 1,000 and 2,000 pounds; 2 weighed 2,200 pounds; 2, 2,360 pounds; 1, 2,800 pounds; 1, 3,000 pounds; 1, 3,500 pounds, and 1, 4,250 pounds. As would naturally he expected, the live loads were found to be

lighter next to the exterior walls of the building. Single-row filing

cases, cabinets, safes, bookcases, and bins are usually located against blank interior walls. Whether by accident or otherwise, the heavier

loads were not found where partitions cut up the floor space into small rooms, indicating that allowance may not be necessary both

for movable partitions and heavy floor loads. Several instances were found where two adjacent floor hays sup- ported average loads of 25 pounds or more, but in no case were two

adjacent bays found loaded in excess of an average of 40 pounds

per square foot. There are hut two or three instances in the floor plans discussed where three or more offices or storerooms meet at the same column, and it is probable that this condition will be found but rarely in buildings designed for a sufficiency of light and ventilation. An investigation by M. W. McIntyre of the Union Central Life Insurance Co.’s building in Cincinnati gave quite similar results. All files, desks, etc., were considered as* being 100 per cent full or furnished with all necessary accessories. Following are tabulated the

results of Captain McIntyre’s investigations:

Office live loads in Union Central Life Insurance Building

Number

of square

feet

Number

of pieces

of furniture

Total weight

of furniture

Weight

of furniture per square

foot

Section A 10, 339 9,303

7,348

10, 339

635

273

702

Pounds

104,478 27,085

36, 306

121, 388

Pounds

10.05

2.91 4.92

11.74

Section B

Section C

Section D

Average 9,332 561.5 72, 314 7.405 30868°—25f 4
16 RECOMMENDED MINIMUM REQUIREMENTS

Weight of employees, computed at the rate of 150 pounds each, added from 0.9 to 1.75 pounds per square foot of floor area. Several individual offices similarly surveyed by Mr. McIntyre showed an average weight of furniture of 7.66 pounds per square foot. The chairman of the Building Code Committee has investigated the live loading in a reference room of a New York insurance company

equipped with heavy -steel filing cases for large Sanborn insurance map books. This was considered to represent unusually heavy

occupancy. The cases were placed back to back, occupying a floor space approximately 5 by 22 feet, and were 55 inches high. It was

found that the case with its aisles for access occupied a space of 247

square feet and weighed, with contents, 10,620 pounds. Observation showed it liable to use by no more than 12 men simultaneously. The total load thus occasioned amounted to 50.3 pounds per square

foot. Some interesting data on the weights per cubic foot of typical heavy office furniture resulted from this investigation. Steel filing cases filled with map books were found to weigh 21.7 pounds per cubic foot; wooden filing cases full of cards weighed 31.8 pounds

per cubic foot; and steel cases similarly filled, 47 pounds. Wooden

correspondence file cases, filled, weighed 21.2 pounds per cubic foot, and those of steel from 23.3 to 26.4 pounds.

C. H. Blackall, of Boston, Mass., and Arthur C. Everett, of the Boston Building Department, published in the American Architect and Building News, April 15, 1893, the results of floor load investi- gations in three office buildings of that city. The buildings were examined very carefully and copious notes taken of room dimensions, occupancy, and details of contents. Average weights were assumed, based on averages for the various

articles of furniture. The human occupancy was taken as the

greatest known to have occurred in each of the offices investigated. The nature of occupancy was sufficiently diverse to be representative. Following is a resume of the results obtained:

Live loads in Boston office buildings

Building Number

of offices Total Total weight

Average

weight

per square

foot

Rogers 41

Sq.ft.

18, 127

32, 151

26, 183

Pounds

294, 984 Pounds16.8 70 544, 419 16.6 A flams ....... 99 425, 109 16.7 Averacre 16.3

i
MINIMUM LIVE LOADS FOR BUILDING DESIGN 17 The 10 heaviest loadings in each building averaged 25.9, 29.8, and

29.0 pounds per square foot, respectively. The highest load found was 40.2 pounds per square foot, and in only 12.4 per cent of the

offices was the floor load in excess of 25 pounds per square foot, and

in only 26 per cent did it exceed 20 pounds. Mr. Blackall recently conducted a similar investigation of live loads

in the Little Building, of Boston, which is reported in the American

Architect and Architectural Review, January 3, 1923. Sixty-four

offices were surveyed, the results indicating live loads even less than

those discovered in the earlier investigations. The maximum floor load was 14.7 pounds per square foot, and but four offices had

loadings over 10 pounds per square foot. The minimum loading

discovered was 1.3 pounds per square foot.

6. Library stack rooms.-—Investigations of library stack rooms show

loads much heavier than are at all likely in reading rooms associated with them. The weight of books assembled as in library stacks

is given by F. J. Ward as 35 pounds per cubic foot, which with stacks

of the customary 8-foot height covering one-half the available floor space would amount to 140 pounds per square foot. The stacks, books, and equipment in the library of the New York Law Institute, weighed by C. T. Coley, were found to average 77.3 pounds per

square foot of floor area. The Department of Commerce library, Washington, D. C., weighed 87 pounds per square foot. Records bound in leather and stored in heavy oaken racks 8 feet high were

found by Frank Burton, commissioner of buildings, Detroit, Mich.,

to weigh 85 pounds per square foot of floor area. The average floor load was 125 pounds, due to the fact that additional records had

been piled to considerable heights on top of the racks. The committee would consider this occupancy a form of special storage, coming under item 2 of the list in Part II, section 4.

7. Crowded rooms. —Densely crowded groups have been shown by

several investigators to weigh at least 140 pounds per square foot, but those results were obtained by strenuous methods, and it is held

unlikely that they will occur under ordinary conditions. Observations of the loading obtained under normal conditions in the elevators

at the Grand Central Terminal in New York showed a maximum of 73 persons on 92 square feet of floor area. With an estimated weight

of 130 pounds each this gives a load of 100 pounds per square foot. Crowds of students at Iowa State University, packed for the purpose

of testing balcony construction under dynamic loads, weighed 116 pounds per square foot. The floor load for spaces subject to crowding, therefore, has been placed at 100 pounds rather than 140 pounds

per square foot. Crowds may occur in places such as listed in section

3, 3, but need not be provided for in rooms with fixed seats. The

average of present code requirements for assembly places is shown

in Appendix, paragraph 4.
18 RECOMMENDED MINIMUM REQUIREMENTS

Par. 6. Floor Loads in Industrial and Commercial Buildings.

It will at once be noticed that the minimum loads prescribed in Part II, section 4, for industrial and commercial occupancies are much less than the average of such requirements now in force. (See Appendix, par. 4). This results from a number of factors which

were carefully considered by the committee.

1. It has been strongly urged by a number of those who partici- pated in the preliminary work on this subject that present code

requirements work an injustice to those conscientiously designing

buildings for certain light commercial and industrial occupancies. In the effort to secure safety in structures subject to unexpected and possibly unregulated change of use the tendency has been to choose the minima which were believed safe under all circumstances. These minima, applied indiscriminately, have occasioned unnecessary expense in many cases for the construction of floors heavier than

needed. Comparison of the observed floor loads in Tables 3 and 4 and the average requirements shown in Appendix, paragraph 4, will illustrate this point.

2. It also has been shown that in many cases the enforcement of a high minimum for design purposes is ineffectual to secure safe conditions unless buildings are periodically inspected for overloads and

changes of use carefully regulated by municipal authorities. Data

received by the committee show many cases of serious overloads in manufacturing and storage buildings, sometimes as high as 300 and

400 per cent. Attention is called to the observed floor loads in Table 3 and to the fact that many of the commodities listed in this table, if piled to moderate story heights, would cause loads far greater than the minima now generally prescribed for storage occupancies.

3. In view of the foregoing, the committee has recommended mini- mum floor load requirements which will permit design of buildings

in each case for the purposes intended, and has provided in succeeding

sections of Part II for a system of control after erection, which, if consistently applied, will eliminate dangers due to overloading.

4- It should be emphasized that the loads prescribed in Part II

as the basis of design are in all cases the minimum loads and must be

increased where the type of occupancy makes this necessary. Special allowance must be made for special loadings, as, for example, laboratories in school buildings, file rooms in office buildings, or library stack rooms. The committee, therefore, has made its requirements apply to portions of buildings rather than whole buildings, specifying

the purpose for which such portions will be used.

5. Those designing buildings for the minimum loads allowed should bear in mind that the future adaptability of the structure may thus

be seriously impaired, its serviceability limited, and its sale or rental value reduced. The minimum loads permit a builder having in mind a
MINIMUM LIVE LOADS FOR BUILDING DESIGN 19

specific occupancy involving light loads to build with maximum

economy, but he should look ahead to the possibility that he may

wish to use or sell the building for some purpose involving greater

loads, and that this will not be permitted without expensive changes. The additional cost of a heavier floor and supporting members may

be returned many times over in superior adaptability of the building.

It is recommended that in designing plants for commercial or industrial purposes, at least some buildings or parts of buildings be made

stronger than may at the time appear necessary. Future changes

in the purpose or process involving increased loads can then be pro- vided for by utilizing these heavier bays or buildings.

It has been found good economy in many cases to design flat roofs of commercial or industrial buildings for loads equal to those assumed

for floors below. It often is desirable to use such roof spaces for purposes unforseen when the structure was built, as, for example, temporary storage of materials, recreation purposes, or additional light equipment, roof signs, small tanks, etc. By making the roof struc- ture strong enough for such service a small initial outlay at the time

the building is built may avoid much greater expense later.

6. Where a building is designed for a particular purpose, as, for example, a chemical or gas plant where loads are inconsiderable except

for those of tanks and other heavy apparatus built into the structure, and where extensive alteration would have to be made before the

building could be used for other purposes, it is assumed by the committee that floors will be adequate at all points for at least 75 pounds

per square foot, and that the necessary provision will be made for

special or concentrated loads exceeding that amount.

7. It is well established by information made available to the committee that storage buildings for certain special purposes may never be loaded to more than 100 pounds per square foot. It is also well proved that space for general storage purposes may be loaded over

large areas to a much greater amount than this. Two minimum

limits are, therefore, specified in Part II, section 4, the first to apply

to buildings for general storage purposes, and the second only when

the special commodity which the structure is to shelter will obviously not entail loads greater than 100 pounds per square foot. It must

be clearly understood that the larger figure is a minimum also and

that it should not be used where there is a possibility of the building being used for materials weighing more than 250 pounds per square

foot.

8. For the guidance of those designing buildings and of building

inspectors in checking applications for building and occupancy per- mits there follow tables of floor load data for storage and factory
20 RECOMMENDED MINIMUM REQUIREMENTS

The data of Table 2 were furnished by C. H. Heller, consulting engineer of San Francisco, Calif., as a result of requests in the tentative draft of this report. Properly interpreted, this information should materially assist in determining the probable live loads in storage buildings for special purposes. Together with data given

in Table 3, it indicates that live loads in buildings for general storage purposes may and do frequently exceed greatly those commonly

assumed for such structures. Table 2.—Weights of Merchandise in Warehouse of wholesale hardware company

[Compiled by C. Heller, consulting engineer, San Francisco, Calif.]

Article Size

1

(in inches) Weight of article Number of

tiers 8

Load per square

foot of

floor area covered 8

Pounds

50 6 [600 if on

1 end; if

i flat,

l 370.64-90 360

211 22552

400

37571

685 200

148

100 132

170 266

75 270

677

254

119 420

500

146

150 250-500

17099

275

300

11784 350

116 400

81

91 225

208

58

30 6 54 20 /22 by 13 by 13 47. 9 Auto wheels

\11)4 by 17 by 5 13 23 25 by 25 by 17 45 5 ... Barbed wire 14 diameter 110 5 Batteries (dry cells) 11 by 18 by 18 105.... 5 Bicycles

Bolts, in barrels

5 by 74 by ? 12 by 12 by 22.. 195 3 Bowls, mixing (barrels) .

.

Brace bits

24 by 24 by 29 200 4 16 by 42 by 9 63 11 Brass pipe and bars rack. Clothes hangers

11 by 4)4 by 7 (ft.) 11 (racks) (Ave.)

17)4 by 19 by 19 38.. 8 Clothes pins 19 by 17 by 10 Cocoa mat., bundles 27 by 31 by 16 107 7 Concrete buckets.. 24 by 30 173 2 Copper wire (barrel) Crow bars, 55-inch, bin. _ Drip cans

18 diameter

2 by 5 300

15 (bins) . _ 7 . 17 by 15 by 10 50 Electric washing machines. 35 by 26 by ? 370 2

(13 by 13 by 16 80 6 Electric wire Enamel ware

\14 diameter by 3 24 17)4 by 28 by 27 62 Fishing tackle, etc 24 by 24 by 6 600

Fittings, in barrels 18 diameter 450-600 . . 1 or 2 Flywheels .... 24 diameter by 8)4 236 Qlassware 15 by 22)4 by 11 18 6. Grindstones Handles (axe), 126 bundles in area (31 by 31). Handles.

24 diameter

31 by 5 by 5

110. 16 (pile) 10126.. 25 by 22 by 7 37 12 Hoe handles, 162 bundles, packed. Hoes, in barrels .

5 diameter by 60; 60 by 60 13 18 20 diameter 485 2 Iron wheelbarrow frames. Iron wheelbarrow trays.

.

Lamp chimneys

24 by 66 by 6 53 24 27 by 32 by 6 24 100

20 by 20 by 17 25 Danterns 16 by 21 by 13 25 Lawn mowers 13 by 20 by 9J4-- 37 u

Mason jars Mops

12 by 15 by 6 42 by 28 by 15...

13158 20

1 First two dimensions determine area on floor. Third dimension is height of article.

• Number of tiers exact, found at time of investigation.

• This load is based upon number of tiers in previous column and not upon weight of one package.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 21

Table 2.—Weights of Merchandise in Warehouse of wholesale hardware company—Continued

Article Size (in inches) Weight of article Number of

tiers

Load per square

foot of

floor area covered

181 6 153 180

840

70 117

130

150 390

158 290

240

500

199 3 210... 4 Oil cans _. 12 by 36 by 15. 21 10

1365 10 Pails (6 are 11 inches high) 50 72 inches

110 3-4J4 Paper (for print depart- ment) . Pipe fittings bins 30 by

30 by 24 by 3 bins barrel fittings weight 500:

1 barrel fitting per

bin.

2 barrel fittings, per

bin.

SH feet by 2 feet 2 inches by

1 foot 9 inches. 650 3}4

500

26

20 77 246

170 130

64

10056

121 no

123 325-475

320 200

180 242

250

115

945 200

212

206 450

90

112

710

68

180

315

125 240-300

430

195

1,145 220

460 375-500

84 5 Pump jacks 14J4 by 27 350.. Pumps 24 by 22 by 51 6 (3 wide, 3 long).. 396

16

i Do 29 by 33 56800 1 Rakes 100 bundles in pile. Roasters (2 deep)

6 feet square 40. 24 by 19 by 13 30 (2 deep) 13 Rolls (wrapping paper) _ . 9 diameter, 15 high 30 6 Roofing paper Rope

6 diameter:

[21 diameter 125 .. 5 <4 feet 0 inches by 3 feet 0 inches- 2,162

Shells (ammunition)

(14 diameter 41 8

24 by 36 by 6 4,000 pounds per 0 Shovels, 30 pounds per bundle, 96 bundles to

pile (pile is 5 by 5 feet)

.

Sledges in barrels

bin. 30

1 foot diameter 315 3 Soap 19V4 hv 20V4 hv im^J 112 5 Spark pings . 14 by 23 by 15 120 4

Steel mats 32 by 28 by ? 320 4 _ _ Tacks 8 by 12 25 Tees 6_ 30 3 Toilet paper 23 by 18 by 23 56 6 Tools (bins 2 feet by 4

feet) 6 high; 270 in' bin

2 equal. Toys.

2 by 4 by 8 7 (K load) ..

25 by 35 by 22..

/1 2-24 wide

84 5 Trucks (hand) Varnish

\481ong__ |90

105

12

1 fi by 24 8. Waste cotton 24 by 34 by 15 100 7

fl foot 6 inches diameter 530.... 28 inches high12. Weed chains (barrel) Wheelbarrow trays (bundle of 6). Window weights (bin)

(10 per bundle)

.

\8 by 8 16

2fi hv 32 117 (9 in row) 10

2 feet 9 inches by 4 feet 0 inches.

(18 by 17 by 10

5 (63 bundles) 4 60 10 Wire cloth _ . _ \26 diameter.. 180 12

10 diameter, 3 foot high 87 3
22 RECOMMENDED MINIMUM REQUIREMENTS

Table 3.—Floor loads in storage buildings

[See explanatory note for method of compiling data]

Class of commodity

Acids

Agricultural machinery.

Asbestos Automobiles, crated Automobile parts

Automobile tires Automobiles, uncrated. Baggage: Empty

Packed

Beverages Books (solidly packed).

Fire clay Cable and wire Carpets and rugs Cement

Cereals Chain

Chemicals

Clocks and watches Cocoa..

Cotton: American

Foreign Cotton goods Cutlery

Electrical goods and machinery.

Extracts Flour and meal

Fruits, dried or canned

Fruits, fresh Furniture Guns and ammunition Gypsum

Hardware, small. Hides, green Hemp, jute, and other fibers Leather and leather goods Machinery, light Meat and meat products.. Milk, condensed

Nonferrous metals, bulk..

Oils and greases Paints Paper and books

Photographic supplies : Plumbing:

Fixtures

Supplies. Potash Rope, fiber Rubber, crude

Shafting steel Silk and silk goods

Sugars, sirups, and candies.

Tiles. Tobacco .' Tobacco

Toilet articles, miscellaneous.

Tools, small, metal Trucks

Varnishes

Maximum

probable weight per

cubic foot of storage space

Maximum

probable weight per square foot

of storage space

Observed loads per square foot of

floor space in storage buildings

65

6560

13 110, 140, 150, 165, 200, 225, 235, 345, 700 30

8 240

64 90, 100, 171

620

40

65

4575

7530

65

45

1005040

35

48 160 320

620 360

600

600 240220

360

800

400 320

280

256, 200 1,200 370, 600, 450

‘ 210,‘450

.bales .do...

.bales.

30

40

45

4540

60

45

60

3520

40

20

45

50 25045

5040

30

55

5530

50

12545

50 225

60

6035

35

75

22

55

240

320

360 360

320

480

360

400

400 2,000

360

720 400

320

200, 300-400,350

350, 450, 340, 315, 300-400, 400

250 250, 60-85, 100

250, 650

220

176, 210, 260, 85-300

150 410, 370, 340

370, 305, 365, 360,385 240

270^ 395, 340, 300

275, 500, 200

240 440

440

240

400

1,000 360

400

400

280 224

250, 310, 400

435, 650

200, 350,

§

25, 350, 300-400

180

600

176 440

100 250
MINIMUM LIVE LOADS FOR BUILDING DESIGN 23

Table 3. —Floor loads in storage buildings—Continued

Class of commodity Maximum

probable weight per cubic foot of storage space

Maximum

probable weight per square foot

of storage space

Observed loads per square foot of

floor space in storage buildings

Vegetables, canned or dried 45 860 285,250,300-400,400 Woods, bulk 45 360 Wool and woolen goods 60 400 150, 245, 250, 330 Note.—The “maximum probable weight per cubic foot of storage space” shown in Table 3 is based on

easeful study of data compiled by the United States Shipping Board for use of the American Expeditionary

Force and published in “Stowage Factors for Ship Cargoes.” Reference also was had to data presented

in Report No. V, Slow Burning or Mill Construction, prepared by the Boston Manufacturers Mutual

Fire Insurance Co. (The former publication is obtainable from the Superintendent of Documents, Government Printing Office, Washington, D. C., at 35 cents per copy, and the latter from the organization named, at 31 Milk Street, Boston, Mass., for 25 cents per copy.) Data also were obtained from various

private sources as to floor loads actually obtaining in different warehouses. They are given in the column

to the right. The “maximum probable weight per cubic foot” is computed from figures obtained by the United States Shipping Board on the weights per cubic foot of commodities crated or prepared for shipment and stored in a ship’s hold. It represents, in other words, the weights of the customary packages or units divided by the storage space they occupy and is believed the most suitable unit for estimating the probable

loads on storage floors. The United States Shipping Board, in practically every case, gives figures for a number of different packages or units or containers, customarily used in different localities, or for different types or weights

of the commodity in question. These usually vary through a range of 100 per cent or more above the mini- mum figure. In selecting the maximum probable weight per cubic foot of storage space it was assumed

as unlikely in most cases that the heaviest type of load would obtain over a whole bay to the greatest possible depth. The maximum probable load was selected with reference to the range of data for that class

of commodities and is as a rule from 10 to 25 per cent less than the maximum figure given in the bulletin. Having in mind the use of modern elevating machinery for piling packages to full-story height in warehouses, the necessary clearance for handling goods, or for effective sprinkler action, it is suggested that an

8-foot depth of stored material is a conservative basis for estimating probable warehouse floor loads. Column

3 of Table 3 has been computed on this basis, and though the results in some cases are rather improbable

the reported loads (column 4) indicate that for most commodities the assumption is not far wrong Table 4.—Floor loads in manufacturing buildings

Occupancy

1. Automobile plants: Machine shop, floors Body building Motor assembly Car assembly Ovens

Furnaces

Storage of parts

Storage of bodies

2. Automobile tire plants: Vulcanizers Dryers

3. Furniture factories (domestic)

:

Woodworking and assembly of pieces. Finishing departments

Storage and shipping

4. Furniture factories (steel furniture)

:

Fabricating departments Machine shops ; Warehouses, factory Warehouses, distributors

Observed loads per square foot of floor space 1

.... 60, 75, 80, 95, 100, 110, 116, 120, 125, 200. .... 14,35.

.... 110. .... 60. .... 150. .... 300.

.... 60, 65, 70, 75, 80, 85, 90, 110, 140, 145, 165, 195, 225, 235, 345. .... 14,27,32,33,41,50.

175.

100-300.*

25. . 50.

200. 250.

250.

300.*

1 The “observed loads per square foot of floor space” are from many sources, and are understood to repre- sent in each case the results of careful observations or actual weighings by those, reporting them. The

greater number of observations on machine shops, perfumery, and automobile factories were furnished by

Albert Kahn; those on textile mills by Charles T. Main; and those on furniture factories by the Grand

Rapids Chapter of the American Institute of Architects and by the National Association of Steel Furniture Manufacturers. The data are regrettably scant in view of the need for such information. They are all that were obtained from an earnest appeal to the architectural and engineering professions.

1 Typical unit loading uniform on all bays at once was judged to be 150 pounds per square foot.

: Much material shipped in knock-down condition.
24 RECOMMENDED MINIMUM REQUIREMENTS

Table 4—Floor loads in manufacturing buildings—Continued

Occupancy Observed loads per square foot of floor space

5. Textile mills: Cardrooms 80. Other departments 50,75.

fi. Machine shops: Light work . 7 bays at 30 pounds, 2 at 35, 4 at 40, 3 at 45, 9 at 50, 4 at 55, 5 at 60, 2 at 70, 5 at 75, 2 at 85, 3 at 90,

1 at 95, 2 at 100. Heavy work. 150-175.

7. Garment factories.. 100.

8. Perfumery works

9. Printing and binding: Heavy pressrooms Light presses Composing rooms

Linotype rooms Type cases, closely packed.

Stereotype rooms

10. Silk mills

40, 65, 75, 85, 105, 120, 160.

250-400. •

175. 75-85.

75-85.

250. 200-250.

30. The following information on floor loads in packing plants is given

by John G. Hormel, of Austin, Minn. The figures for storage floors are based on story heights of 11 feet or less and should be interpreted accordingly when heights are greater. The data are given in round

numbers, but are stated to approximate closely the actual loading in

different departments of the packing plant.

Beef cooler floors Beef cooler ceilings.. Do

Casing storage... Cattle pens Curing coolers Do

Cutting rooms

Cooper shop..

Fertilizer storage.. Freezer storage: Beef piled loose on floors.. Sheep piled loose on floors. Ofial freezer Sharp freezer with racks.

.

Storage freezer. Hair drying and storage... ... Hide storage Hog coolers—floor Hog coolers—ceilings— Hogpen ~-f- Hog dressing room.

Killing floors Lard refinery Lard storage coolers Smokehouse —

100. Pounds per square foot 250 per linear foot of rail (beef in sides). 150 per linear foot of rail (beef in quarters). 200. 100. 250 (meat in tierces laid flat and piled 3 high). 200 (dry salt meat).

150.

150. 300.

200. 175.

250.

250 to 300.

250 (usually in cellars). 100. 200 per linear foot of rail.

150.

150.

100. In spite of repeated efforts no information has been obtained on

the floor loads characterizing retail salesrooms. It is obvious that many of these are very light, and that the maximum load frequently

is due to human occupancy. Such maximum loads approach, but do

not equal those in assembly places not equipped with fixed seats.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 25

Robert D. Kohn, architect, New York, N. Y., reports loads of from

40 to 600 pounds per square foot in a large department store building. Floors in this building were used for office and school purposes, light and heavy storage, retail sales, and in some cases were traversed by

loaded delivery trucks. The National Association of Steel Furniture Manufacturers, on

invitation of the Building Code Committee, has completed a very thorough investigation of live loads resulting from the use of steel furniture with various conditions of loading. The equipment investigated included four general types, namely,

vertical and horizontal filing cases, safes, office desks, and shelving, such as used for factory storage or library purposes. The weights

of several representative types in each class were obtained for three

conditions. First, empty; second, filled with materials, such as com- monly used in offices and representing an average condition; and,

third, with the load produced by the heaviest material likely to be

stored in the type of equipment under consideration. The overall dimensions of the furniture were used in computing the weights per cubic foot and the square feet of floor occupied. Allowance was made in the case of library shelving for human occupancy.

It is reported that the storage and library shelving is rarely moved

in the ordinary course of office use, but that the other types of equipment are all of a portable nature. The following table summarizes the information supplied by the

association:
26 RECOMMENDED MINIMUM REQUIREMENTS
MINIMUM LIVE LOADS FOB BUILDING DESIGN - 27 The minimum live load for sidewalk design was taken at 250 pounds per square foot, in view of the possibility that paving materials

or coal may be piled on walks, or that delivered goods may be

placed on them temporarily to an extent approximating conditions

in general storage warehouses. Recommended live loads for garage floors are based principally on the standard weights of trucks with pay load; data compiled by

E. L. Verveer, of New York. (Engineering News-Record, Feb. 9, 1922.) The following is a partial presentation of this information: Table 6.—Dimensions and weights of typical trucks

Capacity Over- Over- Front Rear Wheel Rear

Chassis and body

weights combined

Chassis, body, and pay load combined

(tons) length width tread tread base tire Front

axle Rearaxle Total Frontaxle Rear

axle Total

Ft. in. (16 7

Ft. in. 5 11 Ft. in. 4 10 Ft. in. 4 10 Ft. in.

11 5 5 Lis.

1,942 Lis. 2,428 Lis.

4, 370 Lis.

2,102 Lis.

4, 268 Lis.6,370

1 \16 2 5 m 4 8 4 10 10 8 4 1,700 3,100 4,800 2,095 4,705 6,800

J17 10 5 m 4 9 4 Hi 2 11 11 6 2,020 3,000 5,020 2,240 6,780 9.020 2

;\18 1 6 1 4.10^ 4 10>2 12 0 7 2, 600 3,800 6,400 3, 000 7,400 10,400

_ 1/17 11 5 10 4 8 4 8 10 4 6 2,700 4,122 6,822 5,460 7,362 12, 822

0

' \20 2 7 0 5 4 5 4 13 6 3,000 4,700 7,700 3,600 10,100 13,700

1/19 7 7 4 5 7 S 7 13 0 10 3,550 5,-910 9,460 4,430 13,030 17, 460 4

\23 7 7 4 5 7 5 7 15 6 12 3,550 6,020 9,570 4,430 13, 140 17, 570

1/20 ey2 7 5M 5 6 6 2% 13 4 12 3, 616 5,684 9,300 4,818 14, 482 19,300 5

i\26 9 7 75/ 5 8 5 4 17 0 13H 4,110 7,590 11, 700 4,550 17, 150 21, 700

1/18 l'A 7 i'A 5 7A. 6 1 10 8 14 4,025 7,225 11, 250 5,630 17, 620 23, 250

j\23 7 7 4H 5 9% 5 9% 15 6 14 3,950 7,605 11, 555 5,505 18,050 23, 555 Mr. Verveer compiled, also, the figures for the distances separating wheel loads when trucks are parked in a garage as closely as is reason- ably to be expected in practice. These data are given below.

Distance between wheel centers

Truck capacity (tons) Trucks

parked

side by

side

Trucks

parked

front to back

Trucks

parked back to back

Ft. in.

1 6

1 6 2 0

2 0

2 0

2 0

Ft. in. 6 0

6 6

6 6 6 6

6 6

Ft. in. 8 0

8 0

8 6 8 6 8 6 8 6

2_

3

45

6

It is very probable that loaded trucks will be driven into garages from time to time for shelter or repair, and provision should be made

for the heavy wheel concentrations thus imposed, taking into account

the possibility that such trucks may be overloaded. It is not at all probable, except, perhaps, in special cases, that there will be several loaded trucks closely adjacent and code requirements providing for such contingencies or for loaded trucks above the entrance floor are believed unnecessary.
28 RECOMMENDED MINIMUM REQUIREMENTS

Par. 7. Roof Loads. The minimum roof loads specified in Part II, section 5, apply only

in localities where snow loads are not an important consideration. Roofs having a slope of less than 4 inches per foot are always liable to accidental loading, such as groups of moving people, storage of material, etc. Hence the necessity of moderate unit loads even where snow is not to be expected. Where large snow loads are to be antici- pated, the loadings prescribed should be increased in accordance with

local experience. Par. 8. Partition Loads. There is slight chance that the shifting of partitions will be an

important matter except in particular occupancies. Residential

buildings in which the floor loads, due to furnishings, approach the minima prescribed for design are usually not those in which a rear- rangement of plan is likely. Apartment buildings, especially those

of recent years, do not admit of much further subdivision, and the

shifting of partitions, once located, is improbable. Construction

plans indicate the position of partitions with respect to floor spans, and unusual loading conditions may readily be checked up. The

weight of wood stud and plaster partitions varies from 80 to 150 pounds per linear foot, depending on height and thickness of plaster, gypsum block from 100 to 150, and hollow-tile partitions from 150 to 300 pounds per linear foot for partitions 10 feet high. The weight

of an additional partition in a building designed for storage or heavy

manufacture purposes therefore is not an important matter. Relocation of partitions is a frequent practice in office and public

buildings and must be provided for. A study of th'e 193 floor plan

sketches made in the course of Mr. Coley’s investigation (see Appendix, par. 5, 5) shows that 33 per cent had partitions additional to those originally located over floor beams. These varied in total length from 12 or 14 feet inclosing a corner of the original office space,

to 38 feet dividing the room into four parts. The average length was 28 feet in a floor bay about 21 feet long by 16 feet 6 inches -wide. In a number of cases the length exceeded 33 feet and consisted of partitions running each way of the floor slab and centered on it. With the type of partitions used in the Equitable building, the weight

thus added amounted in the most extreme case to 13,300 pounds,

or 38.4 pounds per square foot uniformly distributed. The fact must

also be considered that these weights are not thus distributed. So far as the offices in the Equitable building were concerned, there were no cases in which a furniture load of over 30 pounds occurred in conjunction with extra partitions, and it appears that the type of occupancy which causes heavy loads does not usually require

partitions.
MINIMUM LIVE LOADS FOR BUILDING DESIGN 29

Par. 9. Reduction of Live Loads. The usual building code requirement is the following: Every column, post, or other vertical support shall be of sufficient strength to bear safely the combined live and dead loads of such portions of each and every

floor as depend upon it for support, except that in buildings more than five stories high the live load on the floor next below the top floor may be assumed at 95 per cent of the allowable live load, on the next lower floor at 90 per cent, and on

each succeeding lower floor at correspondingly decreasing percentages, provided

that in no case shall less than 50 per cent of the allowable live load be assumed. The committee, however, in the light of evidence received, considers this too conservative. According to statements by a number of authorities, the actual

floor loads in a dwelling or apartment may reach 40 pounds per square foot in one room, but do not average over 15 pounds over

the whole living space and may be much less. Data on hotel rooms

given by the Hotels Statler Co. indicate even lighter loads, and

there seems no reason to believe that the contents of asylums, hospitals, and other residential institutions are any heavier than those

of dwellings. (See Appendix, par. 5, 2, 3.) There is the consideration, moreover, that in residential occupancies only a few interior columns have all quarters of the adjacent floor slab loaded. At

least one quarter will usually be corridor space, thereby reducing

the probable total load on the column, and it is most unlikely that more than one quarter at a time will be called upon to support the

full floor load assumed for the occupancy. There was very little difference between the average loads on the

floors selected as representing light, medium, and heavy occupancy

in the Equitable Building, and no case occurred where more than

three offices or filing rooms came together at one column.

In view of this and the remarkable uniformity of average floor loads in office buildings, as disclosed by several other investigations,

it seems fully justifiable to reduce assumed loads for column design

far below those for floor slabs. Consideration was given to reduction of assumed loads for design

of beams and girders supporting considerable floor areas. Data on

overloading obtained by the committee show that reductions can

not safely be applied to floors for storage or manufacturing purposes and most codes exclude these occupancies from reduction clauses. In view of the moderate floor-load requirements recommended in Part II for other occupancies, the committee believes reductions on beams and girders carrying one floor only is unwise. Study of the

floor-load sketches made in the Equitable Building shows a general tendency for loads to accumulate along partitions and, therefore, over beams. The same also is true to a certain extent in residence
30 RECOMMENDED MINIMUM REQUIREMENTS

buildings, and indicates that reductions for design of beams may be

unadvisable as well as unnecessary. Current code provisions on this point are extremely diverse and

often complicated. Their omission would not appreciably increase construction costs, and would assist greatly in simplifying code

requirements.

Par. 10. Wind Pressures. Some experiments made by the Weather Bureau several years ago gave for the relation between wind velocity and pressure the formula: D P = 0.004 3qSF2

in which P is the pressure in pounds due to positive and negative wind effects upon a small rectangular plate, B is the barometric pres- sure in inches of mercury, S is the surface of the plate in square

feet, and V is the actual velocity of the wind in miles per hour. g

The factor is generally neglected. More recently M. Eiffel, of Paris, determined for the numerical

factor in the above formula the value 0.0033. It seems quite likely that with the more accurate appliances used by M. Eiffel, his value

is the better one. Records of wind velocities have been maintained for many years by the Weather Bureau at its stations located in the principal cities of the country, and the maximum recorded velocities for an average

of five minutes may be found in the publications of the Weather

Bureau, or at any of its offices. These five-minute averages require

correction before they can be used in the formula given above, because of known departures of the records of the Robinson ane- mometer from actual wind velocity, and also because individual gusts

greatly exceed the average for a five-minute period. The relation

of gust to five-minute average is not well worked out. From a few

actual records up to 48 miles per hour, it appears that a 50 per cent

increase may be expected, but it is not established that such a large increase occurs at velocities beyond 50. Inasmuch, however, as the maximum actual velocities shown in Table 7, following tins discussion, seldom exceed by any considerable amount a velocity of 50 miles per

hour, it would seem safe and not unduly drastic to apply the same

allowance of 50 per cent for gusts in cities where higher actual

velocities may be expected.

Practical considerations have led to important differences in the exposures of anemometers of the Weather Bureau in different cities. Furthermore, because of removal from one building to another, the

erection of neighboring buildings, or the gradual increase in height of surrounding buildings, the records from the same city are not strictly
MINIMUM LIVE LOADS POE BUILDING DESIGN 31 comparable year upon year. Hence the use of Weather Bureau

records of wind velocity for engineering purposes involves specific in- quiry in each instance as to local surroundings, and a general code requirement that does not take these conditions into account is likely to lead either to unsafe construction or to needless expense. Table 7.—Recorded wind velocities in various American cities

City and State Period of observations (in years)

Maximum

indicated

velocity recorded

in five- minute

periods

Equivalent actual

velocity

in miles per hour

Building

code

require- ments for heights of approxi- mately

50 to 100

feet

Boston, Mass 45 72 55.8 20 Columbus, Ohio _ _ 20 70 54.4 30 New Haven, Conn 35 62 48. 6 30 New York, N. Y 23 96 73.6 30 Pittsburgh, Pa 17 69 25 Salt Lake City, Utah - 24 68 52! 9 20

St. Paul, Minn 19 102 78.0 ! 30

St. Joseph, Mo 10 60 47.0 Spokane, Wash 41 52 41.3 30 Richmond, Va ' 18 61 47.8 20 Washington, D. C 46 68 52.9 15-30 The velocities shown in the table may or may not be the maxi- mum reasonably to be expected in the life of a building. Certainly no pains should be spared to insure against the wrecking of high

buildings or structures by wind pressure. It is recommended therefore that in all cities the assumed pressure should be at least 20 pounds per square foot and that in cities where indicated maximum

velocities have exceeded 70 miles per hour, this assumption be

increased accordingly. Except in localities where unusually high winds prevail, it is probable that the ordinary structural requirements will afford sufficient wind bracing for most small buildings. The protective effect of natural objects and of other buildings is also in favor of the small

structure. High buildings are not often built in an exposed location with regard to other buildings. The requirements suggested in Part II, section 8, are predicated on the assumption that an unretarded wind pressure will not occur on low buildings nor the lower parts of high buildings. Where this may occur, as, for example, on Michigan Avenue, Chicago, 111., provision for greater wind pressures should be demanded. The requirement; for wind loads take into account the custom of using lower factors of safety for wind stresses and the impact effect which gusts of wind may produce. When buildings are exposed to unusually high winds the structural design should provide for the effects of the wind’s negative pressure
32 RECOMMENDED MINIMUM REQUIREMENTS

component on the leeward side of the building, and for the interior pressures which occur when the wind finds access on the windward

side of the building. These may be fully as great as the direct pressures on exterior surfaces. The factor of safety against overturning, in structures or parts of structures, the stability of which

against wind force depends wholly upon the force of gravity, should be increased rather than reduced. For such structures safety may

be assured by increasing the assumed wind pressure to 40 pounds

per square foot, or, in localities subject to tornadoes, to 60 pounds

per square foot. Par. 11. Floor-Load Placards. The practice recommended in Part II, section 4, allows greater

latitude than is now generally customar}^ in the choice of floor loads

for which commercial and industrial buildings are designed. The

Qwner may take advantage of low floor loads characteristic of the

particular need of his building, but it should be kept in mind that it is always possible that he or some subsequent owner may wish to put the building to a use involving heavier loads. The building

official should be required to issue, and the owner to display prominently in each story of a building, permanent notices giving the safe load. The occupant should be held strictly responsible for overloading, but it is also the duty of the building official so far as practicable, to prevent this. If the actual loads are checked occasionally by the inspection force, as should be done, it is believed that failures due to overloading will for the most part be prevented and the

responsibility for such failures as do occur will be more readily

established.

It is suggested that metal placards similar to automobile number

plates will be most suitable for such purposes, and it is recommended

that issue of an occupancy permit for a building be made conditional on the display of an adequate number of such notices. A suggested form of notice is shown in Figure 1. In this notice the figure will, of course, vary with the conditions. The date in the lower left-hand corner should correspond with the time when the posted floor capacity was approved. It serves merely to find the record of approval readily, when that may be necessary or desirable.

It might be replaced by an official record number if there is such. In the lower right-hand corner should appear the name and title of the

official who issued the placard. A suitable size for the placard would

be by 11 inches. This would make the figure (the outstanding

feature) 1 % inches high, the lettering of the three principal lines onehalf inch high, and that of the lower (secondary) lines one-fourth

inch high.
MINIMUM LIVE LOADS fOR BUILDING DESIGN 33 The design of different portions of a floor and its supporting members for varying uniform live loads should be permitted only when the

portions in question are separated by a permanent partition or wall

so that the higher loading may not carelessly be extended over a

floor space not designed to support it. THIS FLOOR WILL SAFELY SUSTAIN

150

POUNDS PER SQUARE FOOT

UNIFORMLY DISTRIBUTED

IT IS UNLAWFUL TO PLACE ANY

GREATER LOAD ON THIS FLOOR

OFFENDERS ARE SUBJECT TO PROSECUTION OCTOBER

1924

JOHN DOE

BUILDING INSPECTOR

Fig. 1 . —Recommended form of floor-load placard Par. 12. Occupancy Permits. When the design load for which each part of a building is designed

is shown on the plans it facilitates checking by the building official and helps to prevent misunderstandings. It is also easier to ascertain the allowable floor loads if the building occupancy changes at some

later date. Recommendations as to the use of occupancy permits in code enforcement work are somewhat outside the scope of this report. The committee is unanimous in considering them essential to effective control of building construction, and has called attention in Part II

to their usefulness in floor load regulation. Where municipal inspection is effective, the owner is required to report changes in character of occupancy, and occasional inspections

are made to detect overloading. There is much evidence that this

is necessary if public safety is to be assured. Data from numerous

sources indicate that overloads are common in manufacturing and

storage buildings and show that requirements governing original construction must be supplemented by periodical inspection and the checking of occupancy changes if dangerous conditions are to be

prevented.
34 RECOMMENDED MINIMUM REQUIREMENTS

Par. 13. Impact Allowances.

Tests of the impact blows produced by trucks moving at various speeds were made by the United States Bureau of Public Roads and

are reported in "Public Roads,” March, 1921. These tests showed

that up to 10 miles an hour on a level surface the load is practically

static. When a solid-tired truck passes over a one-half inch obstacle, no increased load due to impact need be considered up to a speed

of 5 miles per hour. A review of available information leads to the conclusion that no impact allowance is necessary in the design of garage floors. The live loads specified in Part II are intended to include a sufficient allowance to cover the effect of impact. In the case of special occu- pancies involving unusual impacts a provision for this may well be made by increasing the loads herein specified. Several of those reviewing the tentative draft of this report have

expressed the view that buildings designed for low live loads will be too flexible and that vibration due to dynamic loads, particularly

in theater balconies and similar places, may seriously alarm the occupants. Several cases are reported of buildings which have re- quired alterations for this reason. There is no evidence, however,

that vibration indicates dangerous conditions. A well-built struc- ture may be flexible; and the absence of vibration does not necessarily prove that a building is safe. Two structures may be equal

in strength, but may differ in stiffness, particularly if one is of canti- lever type. When it is desirable for any reason to avoid vibration or undue

deflection, care should be taken to that end by designing for greater

live loads or by using more braces. Safety considerations, however, on which code requirements are based, do not justify live-load as- sumptions greater than those given in Part II.

1. Experiments were made at Iowa State College in 1921 and 1922, under supervision of Almon H. Fuller, professor of civil engineering,

to determine the stress increases caused by crowds in rhythmic

concerted motion such as may characterize the cheering sections

at university games or in fact any crowd under general stimulus of excitement or alarm. Thirteen different investigations were made with groups of men

on a balcony framed on steel beams, supported at one end on a masonry wall and at the other end by tension rods suspended from

roof trusses. Extensometer measurements on the floor beams and

the suspension rods showing increased stresses due to dynamic

loading are given in Table 8.
T

able 8

.

—

Extensometer

investigation

of

live

load

and

impact

stresses

due

to

crowded

loadings

on

balcony

of

the

gymnasium

of

Iowa

State

College

MINIMUM LIVE LOADS FOE BUILDING DESIGN 35
36 RECOMMENDED MINIMUM REQUIREMENTS

2. R. Moreland, in London Engineering, recounts that in the course of an experiment about 1900, 90 men were crowded into a space of 112 square feet on a large scale platform. The average weight was 100 pounds per square foot. They were asked to jump

up and down, and the scale beam registered 150 pounds per square

foot due to impact. The men then ran four abreast across the

platform, but registered no increase over the 150 reading.

3. In the experiments by C. J. Tilden, of Yale University, 5 men

of varying weight were placed on scale platforms, the scales were

balanced and they were then asked to rise quickly from a crouching

to a standing posture. The increased weight registered by the scale beam averaged 66 per cent of the static weight, with variations from

45 to 80 per cent. The men were then asked to rise from a sitting to a standing posture. The average weight increase registered was

79 per cent, with variations from 61 to 122 per cent. Individuals were then asked to stand on the scale platforms and jump up and down in such manner as to produce the greatest possible

effects. The average increase thus caused over static weight was 174 per cent. Mr. Tilden points out that while this last effect was much

more than the others, it is extremely unlikely that the movements

of a number of individuals would occur coincidently. Investigations

of the horizontal impulse exerted by persons rising suddenly from

their seats showed that they might exert a backward horizontal push, about equal to one-half their weights, for a very brief period

of time. Similarly, the horizontal force exerted by a man in walking

will be approximately one-half his weight exerted for a small fraction

of the time during which he passes over a given space.

4. Tests were made on three different bridges of the lateral forces exerted by men running from one side to another as might occur in watching a boat race beneath. The bridges were of different widths

varying from 17 feet to 68 feet. The average velocity of movement

in feet per second was from 10.8 to 13.7 and kinetic energy amounted

to an average of 360 foot-pounds for a man of 144 pounds weight. The acceleration and deceleration were accomplished within a space

of from one-quarter to one-fifth of a second and a horizontal force was exerted during that period of about 150 pounds. If deceleration were accomplished in a much shorter space of time, the lateral force might amount to several hundred pounds. Where vibration is pronounced, the ratio of dead to live load should be increased as much as possible, and particularly good workmanship

should be required for masonry walls and piers. The relation between the mass of the live load and the mass of the

structure must be considered in judging the application of impact

tests to design.

» Transactions of A. S. O. E., Vol. LXXVI, p. 2107 (1913).
MINIMUM LIVE LOADS FOR BUILDING DESIGN 37

Par. 14. Effects of Lighter Load Assumptions on General Stability Consideration was given to the possibility that design for less than customary loads might result in structures too light and flimsy from

the viewpoint of general construction requirements, such as stability and fire resistance. It was decided that the changes proposed do not

affect the safety of buildings. The relation of dead load stress to live load stress in fire-resistive construction is great enough so that no

considerable decrease in stability, as conferred by weight of materials

or rigidity of framing, will occur. The protection of structural members from fire effects is entirely independent of load and stress considerations. If a building is adequate under normal conditions to carry its assumed live loads with a reasonable factor of safety for

stresses, and if its structural members are well protected, it will endure a fire successfully. Wooden joists subject to fire will not be

seriously decreased in cross section during the period ordinarily necessary to vacate the building. Par. 15. Load Assumptions Unrelated to Stress Requirements. Code requirements for live load assumptions frequently are in- creased above what may ordinarily be expected, to offset the effects of unusually liberal working stress requirements elsewhere in such

ordinances. In other cases the situation is reversed, and stress re- quirements are rigid to prevent dangerous conditions in structures designed for less than actual loads. The committee takes the stand

that these are independent considerations and should be so treated. Live load requirements should be adopted with reference only to the probable actual conditions of use. Stress limits should be based on

the known ultimate strength of materials with due reference to work- manship and use conditions affecting uniformity and durability of the material. Par. 16. Weight of Construction Materials. An understanding between designer and building official as to the weights of construction materials is necessary and desirable for purposes of code enforcement. Provision for this does not come

•within the scope of the report. It is suggested, however, that a sec- tion somewhat as follows should be included in a building code. In the absence of definite information establishing the weights of construction materials which are to be used the following unit weights

shall be assumed.
38 RECOMMENDED MINIMUM REQUIREMENTS

Brickwork, solid Concrete, plain or reinforced Cinder concrete Douglas fir, cypress Oak, yellow pine, maple, birch_ Spruce, hemlock

Hollow gypsum partition block. Hollow tile partition block

Plaster and mortar

Pounds per cubic foot .. 120

150

84

36

483048

60

96 Other materials and equipment entering into the dead load of the building shall be taken at their unit weights as given by the manufacturer.

DEPARTMENT OF COMMERCE

WASHINGTON

PUBLICATIONS IN RELATION TO HOUSING AND MUNICIPAL REGULATION

[These publications may be obtained from the Superintendent of Documents* Government Printing

Office, Washington, D. C., payments to be made by money order or New York draft; currency at sender’s

risk. Postage or foreign money not accepted.)

' " ' ’ Recommended Minimum Requirements for Small Dwelling Construction. By the Building Code Committee: Ira H. Woolson, chairman; Edwin H. Brown, William K. Hatt, Rudolph P. Miller, J. A. Newlin, Ernest J. RussCll, and Joseph R. Worcester. 30 illustrations. 108 pages. Govern- ment Printing Office, Washington. Price, 15 cents. Recommended Minimum Requirements for Plumbing in Dwellings and

Similar Buildings. By the Subcommittee on Plumbing; George C. Whipple, chairman; Harry

Y. Carson, William C. Groeniger, Thomas F. Hanley, and A. E. Hansen.

100 illustrations. 250 pages. Government Printing Office, Washington.

Price, 35 cents. Recommended Minimum Requirements for Masonry Wall Construction. By the Building Code Committee; Ira H. Woolson, chairman; Edwin H.

Brown, William K. Hatt, Albert Kahn, Rudolph P. Miller, J. A. Newlin, and Joseph R. Worcester. 4 illustrations. 57 pages. Government Print- ing Office, Washington. A Zoning Primer. By the Advisory Committee on Zoning; Edward M. Bassett, Irving B.

Hiett, John Ihlder, Morris Knowles, Nelson P. Lewis, J, Horace McFarland, Frederick Law Olmsted, and Lawrence Veiller. 12 pages. Govern- ment Printing Office, Washington. Price, 5 cents. A Standard State Zoning Enabling Act, undeb which Municipalities may

Adopt Zoning Regulations. . / By the Advisory Committee on Zoning. 12 pages, Government Printing

Office, Washington. Price, 5 cents. . ~ How to Own Your Home. By John M. Gries and James S. Taylor, with a foreword by Herbert Hoover,

viii plus 28 pages. Government Printing Office, Washington. Price, 5 cents. MIMEOGRAPHED MATERIAL A list of zoned municipalities and references to State laws relating to zoning

is kept by the Division of Building and Housing, Department of Commerce,

Washington, and copies may be obtained on application.