Floor loads in buildings, with particular reference to offices

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NATIONAL RESEARCH COUNCIL OF CANADA D I V I S I O N OF BUILDING FlESEARCH

F'LOOR LOADS I N BUILDINGS

With Partioular Reference t o Offices

by D,E, A l l e n

Report No,

4 9

of the

Divieion

of

Building

Research

O t t a w a Auguat

1958

PREFACE

T h i s r e p o r t summarizes t h e r e s u l t s of s t u d i e s c a r r i e d o u t i n t h e B u i l d i n g S t r u c t u r e s S e c t i o n of t h e D i v i s i o n of Bulding Hesearch a r i s i n g from a r e q u e s t which came t o t h e

D i v i s i o n from t h e Advisory F t r u c t u r a l Group which now o p e r a t e s under t h e A s s o c i a t e Committee on t h e N a t i o n a l B u i l d i n g Code. T h i s n a t i o n a l a d v i s o r y group, which b r i n g s t o g e t h e r almost two dozen Canadians from v a r i e d f i e l d s of work connected w i t h s t r u c t u r a l e n g i n e e r i n g work and i t s a p p l i c a t i o n s , has been r e v i e w i n g t h e N a t i o n a l B u i l d i n g Code w i t h a view t o i t s s t e a d y improvement. From t h e s e s t u d i e s have a r i s e n r e q u e s t s such a s t h a t t o which t h i s r e p o r t i s a p a r t i a l answer.

The r e p o r t has gone somewhat f u r t h e r t h a n was r e q u e s t e d by t h e Advisory S t r u c t u r a l Group s i n c e t h e s t u d y of l o a d s i n g e n e r a l i s a c o n t i n u i n g p r o j e c t of t h e B u i l d i n g S t r u c t u r e s S e c t i o n . I n i t s work on b u i l d i n g s a s a whole t h e D i v i s i o n h a s come t o r e a l i z e t h e g r e a t importance of a n a c c u r a t e e v a l u a t i o n of t h e l o a d s t o be imposed upon s t r u c t u r e s , a s t u d y which i n g e n e r a l r e c e i v e s t o o l i t t l e a t t e n t i o n i n comparison w i t h t h e g r e a t amount of r e s e a r c h done on s t r u c - t u r a l d e s i g n .

The r e p o r t i s a p r o g r e s s s t a t e m e n t only. It i s hoped t o c o n t i n u e w i t h some of t h e o b s e r v a t i o n s on a c t u a l f l o o r l o a d s which i t r e c o r d s . It has been p r e p a r e d by U.E. A l l e n , a g r a d u a t e o f Queens' U n i v e r s i t y and a membar of t h e B u i l d i n g S t r u c t u r e s Sect i o n .

Ottawa,

~ u g u s t

1958.

Robert

F. Legget,

FLOOR LOADS I N BUILDINGS

With P a r t i c u l a r Reference t o O f f i c e s

DOE. Allen

The Advisory S t r u c t u r a l Group of t h e A s s o c i a t e Committee on t h e National Building Code a t i t s 6 t h meeting r e c e n t l y

r e q u e s t e d a review of l o a d s imposed by modern computing m c h i n e r y i n connection with t h e l o a d s p e c i f i e d f o r o f f i c e f l o o r s . An o f f i c e f l o o r , designed according t o t h e N a t i o n a l Building Code of Canada ( N B C ) must be a b l e Z t o support a

uniformly d i s t r i b u t e d l i v e load of 50 ~ / f t o r a c o n c e n t r a t e d load of 2000 l b d i s t r i b u t e d over an a r e a of 25 by 25 f t .

Along with t h i s review a l i m i t e d l i t e r a t u r e s e a r c h was c a r r i e d out on t h e q u e s t i o n of o f f i c e l o a d s i n p a r t i c u l a r and occupancy l o a d s i n g e n e r a l .

T h i s r e p o r t summarizes t h e f i n d i n g s of t h e s e a r c h and t h e e n q u i r i e s i n t o computing machinery u s i n g t h e occurrence of such machinery a t t h e Dominion Bureau of S t a t i s t i c s , i n Ottawa a s an example. Also included a r e some s u g g e s t i o n s f o r changes i n t h e NBC c l a s s i f i c a t i o n of occupancy l o a d s according t o

expected use. Occupancy l o a d s i n g e n e r a l , o f f i c e l o a d s and o b s e r v a t i o n s made, comparison of d e s i g n o f f i c e l o a d s i n

B r i t a i n , United S t a t e s and Canada and f i n a l l y , t h e l o a d s due o f f i c e machinery and s a f e s a r e a l s o b r i e f l y d i s c u s s e d .

T h i s r e p o r t r e f l e c t s t o some e x t e n t t h e r e c e n t change of a t t i t u d e towards s t r u c t u r a l s a f e t y o r s t r u c t u r a l s u f f i c i e n c y . T h i s change emphasizes t h e need f o r a more r e a l i s t i c t r e a t m e n t of what l o a d s a c t u a l l y o c c u r ; t h i s means c o l l e c t i n g r e c o r d s of a c t u a l l o a d s t a k i n g s a m ~ l e s and t r e a t i n g them t o some e x t e n t i n terms of

.

It i s n o t intended t o d i s c u s s which extreme should be chosen o r what v a l u e of p r o b a b i l i t y of overload should b e used b u t r a t h e r what v a l u e s a c t u a l l y do occur and what a r e t h e s o u r c e s of l o a d , such a s persons,

p r o p e r t y and storage.

Live Loads Due t o Occupancy: A Suggested R e c l a s s i f i c a t i o n Live l o a d s due t o occupancy a r e g i v e n i n t h e N a t i o n a l Building Code (1953) (1) i n t h e form of a t a b l e which l i s t s a l p h a b e t i c a l l y 27 of t h e most common rooms o r f l o o r a r e a s

( s u c h a s k i t c h e n s , o f f i c e s , e t c ) w i t h t h e corresponding minirmun allowable uniformly d i s t r i b u t e d l i v e l o a d (Table I ) .

TABLE I

( T a b l e 3.2 of t h e N a t i o n a l Building Code of Canada ( 1 9 5 3 ) ) ?!inimum Allowable Uniformly D i s t r i b u t e d Live Loads

f o r Various Types of Use f o r F l o o r Areas o r Rooms

Column 1 Column 2

Minimum Allowable Uniformly D i s t r i b u t e d Type of Use of F l o o r Area o r Room Live Load, i n Pounds

Per Square Foot Assembly rooms w i t h f i x e d s e a t s such a s

t h e a t r e a u d i t o r i a o r c o n c e r t h a l l s 60 Other assembly rooms where non-fixed

s e a t s may be used i n c l u d i n g c l a s s - rooms designed o r intended f o r

assembly purposes 100

Concourses, w a i t i n g rooms i n assembly

b u i l d i n g s , r o t u n d a s , e n t r a n c e h a l l s 100

S t a d i a and g r a n d s t a n d s 100

Rowling a l l e y s , p o o l and b i l l i a r d rooms

and s i m i l a r a r e a s

75

Classrooms 60

V o c a t i o n a l shops

80

Operating and c l i n i c a l rooms i n h o s p i t a l s

D e t e n t i o n q u a r t e r s

75

Reading o r w r i t i n g rooms o r lounges* 60

75

Dining rooms, p u b l i c

-

f o r u s e by more t h a n 100 p e r s o n s 100

-

f o r u s e by fewer t h a n 100 persons 60

Kitchens-:? 100

Rooms used f o r nleeping4t Dwelling u n i t s , a l l rooms

R e t a i l s a l e s f l o o r s 100

Kanufacturing o r p r o c e s s rooms

O f f i c e s 125

T o i l e t and l o c k e r rooms 50

Cleaning and r e p a i r of goods 100 50

Shops p r o v i d i n g s e r v i c e s t o t h e p e r s o n such a s h a i r d r e s s i n g p a r l o u r s 100 E x i t s and c o r r i d o r s except t h o s e s e r v i n g 1- and 2-family d w e l l i n g s 100 Storage

-

passenger c a r s

-

t r u c k s and buses, unloaded 75

-

t r u c k s and buses, loaded 150

-

o t h e r s t o r a g e 250

Sidewalks and driveways over area- 125

ways and basements 250

These "occupancies" r e p r e s e n t " t h e u s e o r i n t e n d e d u s e o f a b u i l d i n g o r s t r u c t u r e o r p a r t t h e r e o f f o r t h e s h e l t e r o r

s u p p o r t of p e r s o n s , animals o r p r o p e r t y " (NBC, 3 . 3 . 3 ( a ) ) . ~ o r ' b c c u p a n c i e s " n o t i n c l u d e d i n t h e t a b l e t h e Code r e q u i r e s

t h a t l o a d s b e assumed f o r "occupancies" which c r e a t e o r accommodate s i m i l a r l o a d i n g s . The Code a l s o s u g g e s t s t h a t t h e " o c c u p a n c i e s t ' l i s t e d i n t h e American S t a n d a r d s A s s o c i a t i o n

A S A AS8.1

-

1955 ( 2 ) be used a s a f u r t h e r guide. T h i s s t a n d a r d s p e c i f i e s f i f t y "occupanciestt similar t o t h o s e i n t h e NBC and o f f e r s i n i t s appendix

55

more s p e c i a l i z e d

t I o c c u p a n c i e s " a s a g u i d e t o b u i l d i n g o f f i c i a l s .

I n s p i t e of a l l t h i s i n f o r m a t i o n i t i s i m p o s s i b l e t o c o v e r a l l c a s e s , It i s assumed t h a t o c c u p a n c i e s which a r e n o t covered c a n be t r e a t e d by comparing them w i t h s i m i l a r l y

loaded o c c u p a n c i e s i n t h e t a b l e s . Thus, a number o f occupan- c i e s of d i f f e r e n t f u n c t i o n a l u s e , b u t o f t e n of t h e same

p r o b a b l e l o a d occupancy a r e t h e b a s i s f o r c a t e g o r i z i n g

minimum a l l o w a b l e l o a d s . Furthermore, some of t h e i n d i v i d u a l t e r m s such a s " o f f i c e s " a r e t o o broad i n t h e m s e l v e s t o b e s a t i s f a c t o r i l y covered b y a s i n g l e d e s i g n l o a d . " O f f i c e s t ' may c o n t a i n rows of heavy f i l i n g c a b i n e t s , o r a s i s u s u a l l y

t h e c a s e , l i g h t f u r n i t u r e , some f i l e s and a s m a l l number o f p e r s o n s . T h i s s u g g e s t s t h e need f o r f u r t h e r c l a s s i f i c a t i o n w i t h i n some of t h e s e c l a s s e s depending on how w e l l t h e u s e of each f l o o r can be p r e d i c t e d and what r i s k t h e owner and t h e p u b l i c w i s h t o t a k e . The c o n c l u s i o n i s t h a t t h e r e i s no w e l l - d e f i n e d c a t e g o r y o f e x p e c t e d occupancy l o a d s . The

f o l l o w i n g i s suggested a s a n a l t e r n a t i v e approach.

Design f l o o r l o a d s c o n s i s t of l o a d s due t o occupancy c n t h e one hand and dead l o a d s on t h e o t h e r . These a r e d e f i n e d r e s p e c t i v e l y i n t h e NBC a s " t h e g r e a t e s t l o a d t h a t i s l i a b l e t o be imposed by t h e i n t e n d e d occupancytt (NBC

3.3.3

( a ) ) and " t h e a c t u a l w e i g h t s of t h e m a t e r i a l s o f c o n s t r u c t i o n i n c o r - p o r a t e d i n t h e s t r u c t u r e and t h e weight o f a l l permanent

b u i l d i n g s e r v i c e equipment" ( N B C 4.1.2.5). Live l o a d s due t o occupancy w i l l h e n c e f o r t h b e c a l l e d occupancy l o a d s .

A l l occupancy l o a d s a r e e i t h e r s t a t i c o r dynamic.

A l l s t a t i c occupancy l o a d s a r e d e r i v e d from two main s o u r c e s ; p e r s o n s and animals on t h e one hand and p r o p e r t y and s t o r a g e on t h e o t h e r . I n t h i s r e p o r t p r o p e r t y r e p r e s e n t s t h o s e t h i n g s whose u s e o r purpose i s n o t p r i m w i l y s t o r a g e . The f o l l o w i n g a r e suggested s o u r c e s of occupancy l o a d s .

A. S t a t i c Load

1. Assembly of persons and animals.

2. Assembly and s t o r a g e of p r o p e r t y . These may b e f i x e d o r movable.

B, Dynamic Load

1. Forces produced during impact. 2. Forces produced during v i b r a t i o n s .

Some o r a l l of t h e s e components i n f l u e n c e t h e maximum s t r u c t u r a l a c t i o n i n a f l o o r during i t s l i f e t i m e . For a

b u i l d i n g code, d e f i n i t e v a l u e s must be given and t h i s r e q u i r e s a c l a s s i f i c a t i o n of intended occupancy. Since it i s of prime importance t h e magnitude of t h i s load should be t h e b a s i s of c l a s s i f i c a t i o n and not t h e intended apecif i c "use" i n alpha- b e t i c a l order. The "use" a s i n d i c a t e d by t h e term " o f f i c e " by i t s e l f r e p r e s e n t s much more t h a n t h e probable load t o be

expected, It a l s o r e p r e s e n t s t h e f u n c t i o n s o r a c t i v i t i e s t o be c a r r i e d out. Thus t h e p r e s e n t c l a s s i f i c a t i o n i s compli- cated by b r i n g i n g i n more t h a n i s needed. I f t h e minimum

allowable load i s i n t h e form of a b a s i c uniformly d i s t r i b u t e d load, each of t h e s e loads i n o r d e r of magnitude should r e p r e - s e n t a c l a s s . F i r s t each of t h e sources of occupancy load should be discussed.

Where t h e g r e a t e s t probable load8 a r e due only t o assembly of persons t h e e s t i m a t i o n of t h e load i s s i m p l i f i e d by t h e homogeneous c h a r a c t e r of t h e loading agent and t h e l i m i t t o which people can be assembled and r e s t r i c t e d from over-assembly. The loading i s homogeneous i n t h a t t h e average u n i t weight of d i f f e r e n t groups of men i s n e a r l y t h e same.

Some p l a c e s a r e intended f o r open assembly such a s dance

f l o o r s , a u d i t o r i a and classrooms without f i x e d s e a t s , e n t r a n c e h a l l s , grandstands, gymnasia, and p u b l i c c o r r i d o r s . I n most p l a c e s , dynamic loading i s not l i k e l y t o be s i g n i f i c a n t when people a r e packed t o g e t h e r a t t h e maximum probable d e n s i t y whereas i n t h e case of d r i l l h a l l s and p e d e s t r i a n bridges, t h e e f f e c t s of dynamic loading a r e c o n s i d e r a b l e even though t h e r e i s l e s s crowding. Crowding up t o 180 lb/sq f t

( 5 )

has been proved p o s s i b l e but s i n c e such crowding (which c o r r e s - ponds t o a t i g h t l y packed e l e v a t o r ) i s extremely u n l i k e l y f o r most assembly occupancies, t h e load s p e c i f i e d i s l e s s , u s u a l l y 100 lb/sq f t ( a 150-lb man every

1.5

sq f t ) .

On t h e o t h e r hand assemby and s t o r a g e of property i s

not homogeneous i n c h a r a c t e r s i n c e t h e r e a r e d i f f e r e n t magni- tudea of load w i t h each t y p e of p r o p e r t y and a c o n s i d e r a t i o n of maximum probable load must account f o r t h e t y p e s of

p r o p e r t y l i a b l e t o occur and t h e probable arrangements of t h e d i f f e r e n t t y p e s of p r o p e r t y i n each case, The heavy a r t i c l e s w i l l predominate i n probable maximum loadings, On f l o o r s p r i m a r i l y intended f o r s t o r a g e an e s t i m a t i o n of probable load w i l l be s i m p l i f i e d because arrangement i s not a f a c t o r . Here t h e load e s t i m a t i o n should be based on t h e h e a v i e s t t y p e of s t o r a g e and t h e volume of s t o r a g e not l i k e l y t o be exceeded.

For s t o r a g e load, broad c l a s s e s of magnitude such a s 130,

150

and 200 lb/sq f t minimum allowable seem a more p r a c t i c a l b a s i s t h a n an a l p h a b e t i c a l l i s t of d i f f e r e n t t y p e s of s t o r a g e ,

mainly because t h e expected u s e cannot be e x a c t l y defined, The choice of c l a s s could be made by r e f e r e n c e t o m a t e r i a l weights. Where t h e r e i s a combination of two t y p e s of s t o r a g e

such a s an o f f i c e containing machines a s t h e heavy a r t i c l e and f u r n i t u r e a s t h e l i g h t a r t i c l e , t h e p r o b a b i l i t y of e x t e n s i v e l o a d i n g of t h e heavier a r t i c l e i s prevented by t h e r e l i a b l e presence of t h e l i g h t a r t i c l e s . Probable arrangements must be considered i n t h e s e c a s e s ( e , g , whether t h e l i g h t a r t i c l e s

a r e f i x e d o r n o t ) ,

Most occupancies such a s domestic rooms, o f f i c e s , and assembly rooms w i t h f i x e d s e a t s a r e a combination of assembly of persons and assembly of p r o p e r t y o r s t o r a g e ( f i x e d o r

movable), The magnitude of probable load depends on t h e weights of t h e d i f f e r e n t t y p e s of p r o p e r t y and t h e probable arrangements of t h e p r o p e r t y and assembly of persona a c t i n g t o g e t h e r . This argument i s considered i n more d e t a i l f o r o f f i c e s i n t h e next s e c t i o n of t h e r e p o r t . Johnson ( 6 ) made a study of two loading components

-

persons and f u r n i t u r e

-

i n a number of dwelling f l a t s . His measured sample of f l o o r l o a d s i s made up o f : 1) f u r n i t u r e p r e s e n t a t t h e t h e of observation, and 2 ) t h e g r e a t e s t number of persons having

v i s i t e d a t one time during t h e owner's occupancy. H i s r e s u l t s showed t h a t t h e mean load per u n i t a r e a due t o people was

n e a r l y independent of f l o o r a r e a and t h a t t h e l o a d due t o f u r n i t u r e was dependent on f l o o r area.

Dynamic loadings i n b u i l d i n g codes have been t a k e n c a r e of by use of "equivalent" s t a t i c l o a d s and l i m i t i n g

d e f l e c t i o n s . Limiting d e f l e c t i o n s safeguard a g a i n s t e x c e s s i v e s p r i n g i n e s s of f l o o r s under dynamic l o a d i n g (e,g. persona

walking, v i b r a t i n g machinery). The f o r c e s produced by dynamic l o a d s , however, a r e more d i f f i c u l t t o determine t h a n t h o s e f o r simple s t a t i c loads s i n c e t h e y depend e s s e n t i a l l y on t h e weight and r i g i d i t y of t h e member upon which they. a c t . It i s a l s o w e l l known t h a t t h e s t r e s s c a p a c i t y of almost a l l

engineering m a t e r i a l s i n c r e a s e s with an i n c r e a s e i n t h e r a t e of f o r c e a p p l i c a t i o n and might t h e r e f o r e warrant a compli- mentary i n c r e a s e i n t h e allowable s t r e s s . T h i s p r o p e r t y i s a l s o a f f e c t e d , however, by t h e f a t i g u e caused by high r e v e r s a l s of s t r e s s and would have t o be considered with caution.

Since the p r e s e n t c l a s s i f i c a t i o n according t o

II occupancies1' i s not e a s i l y a p p l i e d and administered, Table I1

which i s a c l a s s i f i c a t i o n of s t a t i c occupancy l o a d s i s suggested. It i s s i m i l a r t o t h e B r i t i s h Standard Code of P r a c t i c e

( 3 ) .

TABLE I1

OCCUPANCY LOADS

Class

1 0

Types o f Occupancy Expected Examples o f Occupancy

(1) No assembly o f p e r s o n s , I n a c c e s s i b l e a t t i c s l i t t l e s t o r a g e

( 2 ) P l a c e s o f v e r y l i m i t e d Crawl s p a c e s a c c e s s and s t o r a g e

( 1 ) Very l i g h t p r o p e r t y , l i t t l e D w e l l i n g s ; second and t h i r d assembly o f p e r s o n s s t o r i e s

( 1 ) Very l i g h t p r o p e r t y , some D w e l l i n g s ; f i r s t f l o o r rooms u s e d assembly o f p e r s o n s f o r s l e e p i n g , s i t t i n g and d r e s s i n g ( 1) L i g h t p r o p e r t y , some O f f i c e s not u s e d p r i m a r i l y f o r

s t o r a g e , some assembly s t o r a g e o f p r o p e r t y . T o i l e t and o f p e r s o n s l o c k e r rooms

( 2 ) Assembly o f p e r s o n s , b u t Auditoriums and c l a s s r o o m s w i t h w i t h l i g h t p r o p e r t y f i x e d s e a t s . Reading and w r i t i n g rooms. Churches (1) L i g h t s t o r a g e O f f i c e f i l e rooms. A t t i c s t o r a g e ( 2 ) S t o r a g e o f h e a v i e r i t e m s S t o r a g e o f p a s s e n g e r c a r s b u t r e s t r i c t e d i n a r e a covered

( 3 ) S t o r a g e and some assembly O p e r a t i n g and c l i n i c a l h o s p i t a l o f p e r s o n s rooms. Bowling a l l e y s , p o o l and

b i l l i a r d rooms. V o c a t i o n a l shops ( 4 ) L i m i t e d assembly of p e r s o n s D e t e n t i o n q u a r t e r s . C o r r i d o r s t o rooms o f c l a s s 40 o r l i g h t e r (1) P l a c e s o f assembly of Assembly p l a c e s w i t h o u t f i x e d p e r s o n s s e a t s , i.e., d a n c e f l o o r s , c l a s s - rooms, gymnasiums, c o n c o u r s e s , e n t r a n c e h a l l s , d i n i n g rooms, l o b b i e s , c o r r i d o r s and e x i t s . Ztadiums

( 2 ) S t o r a g e and some assembly K i t c h e n s o t h e r t h a n d w e l l i n g u n i t s , r e t a i l s a l e s f l o o r s . C l e a n i n g and r e p a i r o f goods. Shops p r o v i d i n g

s e r v i c e s t o t h e p e r s o n s u c h a s h a i r d r e s s i n g p a r l o u r s

( 3 ) L i g h t t o medium s t o r a g e O f f i c e rooms c o n t a i n i n g p r i m a r i l y machinery o r heavy f i l e s . Ware- h o u s e s , workshops and f a c t o r i e s used f o r l i g h t w e i g h t s t o r a g e ( 1 ) Medium s t o r a g e S t a c k rooms; l i b r a r i e s , o f f i c e s

w i t h c a r d f i l e s

( 2 ) S t o r a g e o r heavy S t o r a g e ; l i g h t t r u c k s and buses. p r o p e r t y and assembly Armouries, d r i l l h a l l s , t h e a t r e o f p e r s o n s s t a g e f l o o r s . Warehouses, work-

shops and f a c t o r i e s f o r medium w e i g h t l o a d

(1) Heavy s t o r a g e Warehouses, workshops, f a c t o r i e s f o r heavyweight l o a d s . S t a c k o o f books, b o o k s t o r e s

(1) Very heavy s t o r a g e S t o r n g c ; h e a v y t r u c k s and b u s e s , l o a d e d , sidewalks, drivewnys o v o r a r e a s

O f f i c e Load; Discussion and Observations

Freudenthal

( 7 )

suggest a t h a t I n any loading a n a l y s i s t h e following determlnat Ions be made:

( a ) S p e c i f i c a t i o n of atandard loading p a t t e r n and i t s r e l a t i o n -

ship t o a c t u a l loading conditlona. Is t h e standard load s u f f i c i e n t l y c h a r a c t e r i s t i c of t h e r e a l load p a t t e r n t o make t h e s t r u c t u r a l a c t ion equivalent o r comparable? ( b ) Evaluation of t h e p r o b a b i l i t y of occurrence of varioua

i n t e n s i t i e s of t h e standard load. When t h e v a r i a t i o n of l o a d i n t e n s i t y i s random, it i s described by It8 frequency d i s t r i b u t i o n ,

( c ) Analysis of t h e t i m e dependence of t h e atandard load and i t s v a r i a b i l i t y : ( i ) t h e r a t e of load a p p l i c a t i o n , ( i i ) t h e d u r a t i o n of loading and, ( I l l ) t h e number, frequency and

sequence of load r e p e t i t i o n s ,

The maximum s t r u c t u r a l a c t i o n t o which a f l o o r of a p a r t i c u l a r o f f i c e i s subjected during i t s l i f e t i m e i a caused by a t l e a s t some of t h e following sources:

A. S t a t i c Load

1. Assembly of persons

2. Assembly of property and s t o r a g e ( I ) F u r n i t u r e

(11) Stack8 containing books, f i l e s , c a r d s , etc. (iii) Heavy concentrated l o a d s due t o s a f e s , o f f i c e

machinery ( i n c l u d i n g loada due t o t h e t r a n s p o r t a - t i o n of t h e s e

( i v ) Movable partitions B e Dynamic Load

1. Forces due t o Impact

2. Forces due t o v i b r a t i o n

The standard design-loading p a t t e r n should r e p r e s e n t t h e equivalent s t r u c t u r a l a c t i o n 8 o c c u r r i n g from extreme

loadings. These extreme loada a r e determined by t h e probable arrangement8 of t h e above components w i t h i n t h e limits of t h e intended "uses" t h a t t h e s p e c i f i c f l o o r Is l i k e l y t o experience. I n o t h e r words, t h e l i m i t s defined by t h e "uae" t e r n w i l l

d i r e c t l y a f f e c t t h e probable arrangements and hence t h e probable extreme values. I f t h e term d e f i n i n g t h e "use" has a broad

meaning and i f it may be f u r t h e r divided i n t o more s p e c i f i c

loading p a t t e r n . T h i s p a t t e r n w i l l t h e n be t o o l a r g e f o r more s p e c i f i c usea of l i g h t occupancy and t o o small f o r thoae of heavy occupancy. This suggests a d i v i d i n g up of t h e s e broad terms. The degree t o which t h i s p r o c e s s of c a t e g o r i z i n g t o more s p e c i f i c usea can be c a r r i e d out i s l i m i t e d however, by t h e

r e l i a b i l i t y of t h e assumption t h a t t h e use w i l l not change

d u r i n g t h e s t r u c t u r e ' s e x i s t e n c e and by t h e limits t o which t h e owners o r p u b l i c a n t i c i p a t e t h e u s e of each room.

This c o n s i d e r a t i o n suggests t h a t o f f i c e f l o o r s should b e designed t o withstand l o a d s varying from about 50 lb/sq f t

f o r off i c e s where deskwork i s expected t o be t h e main u s e , t o about 150 lb/sq f t where s t o r a g e of high s t a c k s of books o r f i l e s i s expected. A 50-lb/sq f t load may r e p r e s e n t adequately t h e maximum loads l i k e l y t o occur i n o f f i c e s primarily used f o r deskwork but i t i s much t o o low f o r o f f i c e s where s t o r a g e o f f i l e s may be t h e only use, It may be b e t t e r t o avoid t h e g e n e r a l term " o f f i c e s " and perhaps u s e more d e s c r i p t i v e terms f o r each room o r a r e a under c o n s i d e r a t i o n . These terms would b e baaed on magnitude and arrangements o f persons, p r o p e r t y o r

s t o r a g e a s suggested previounly. The v a r i a b i l i t y of extreme v a l u e s w i l l depend g r s a t l y on how w e l l t h e "use" i s defined.

Within a given u s e c e r t a i n p h y s i c a l f a c t o r e , such a s t h e s i z e of t h e loaded a r e a , have a s i g n i f i c a n t e f f e c t on t h e probable mean load p e r sq f t . The NBC r e c o g n i z e s t h a t b o t h t h e loaded a r e a and t h e number of f l o o r s a r e s i g n i f i c a n t . Where s t o r a g e i s concerned, t h e height of t h e s t o r y w i l l have

some e f f e c t on t h e maximum probable load. Also, t h e s i z e of t h e room may p a r t l y r e s t r i c t t h e probable arrangements of t h e components. There i s a l s o l e s s l i k e l i h o o d of s t o r a g e a g a i n s t e x t e r i o r w a l l s w i t h windows. The shape of t h e loaded a r e a considered may a l s o be a f a c t o r .

The b e s t way t o determine probable l o a d s i s t o make e x t e n s i v e o b s e r v a t i o n s of l o a d s on a n e x i s t i n g sample f o r each

11 _{use", t a k i n g i n t o account t h e f a c t o r s of a r e a , f l o o r s , e t c .}

and making s p e c i a l o b s e r v a t i o n s of extreme c o n d i t i o n s which a r e most s i g n i f i c a n t i n e s t i m a t i n g a d e s i g n load.

Loads i n o f f i c e b u i l d i n g s have been observed i n surveys by White ( 8 ) and Dunham

( 9 ) .

White's study covered e i g h t t y p e e

of o f f i c e b u i l d i n g s t o t a l l i n g 140,000 sq f t . Dunham surveyed two h e a v i l y loaded government o f f i c e b u i l d i n g s ( I n t e r n a l

Revenue Building, Veteran1 s Administration B u i l d i n g ) , t o t a l l i n g 380,000 sq f t . The maximum observed mean load p e r sq f t of f l o o r decreased w i t h an i n c r e a s e of a r e a loaded. T h i s i s expected s i n c e maximum l o a d s occur from arrangements o f heavy and l i g h t a r t i c l e s except where t h e t y p e of loading i s homo- geneous and spread over a n a r e a . T h i s l a t t e r arrangement i s l i m i t e d by t h e e x t e n t of area t o which t h e load i s l i k e l y t o extend without i n t e r r u p t i o n .

These r e c o r d s have been a p p l i e d t o t h e normal p r o b a b i l i t y curve by Horne ( 1 0 ) on t h e assumption t h a t t h e a c t u a l f l o o r

load i s t h e r e s u l t of a l a r g e number of independent causee, none of which i s of over-riding importance. The curves and r e c o r d s a r e shown i n Figure 1 along w i t h some v a l u e s observed by t h e author. Maxima observed by Dunhmm, White and t h e a u t h o r a r e l a r g e compared t o t h e code d e s i g n load of 50 lb/sq f t .

For a r e a s over about 100 s q f t t h e maxima were s t r o n g l y

i n f l u e n c e d by s t o r a g e s t a c k s of books, f i l i n g , c a r d s e t c . and, f o r s m a l l e r a r e a s by b o t h s t a c k s and h e a v l o a d s due t o s a f e s , machines, e t c . Safes and machines a r e considered l a t e r i n t h i s r e p o r t .

White ( 8 ) has observed how w e l l t h e a c t u a l l o a d p a t t e r n i s r e p r e s e n t e d by a uniformly d i s t r i b u t e d load. For a number of t y p i c a l rooms he compared t h e a c t u a l load t o t h e e q u i v a l e n t uniformly d i s t r i b u t e d load ( i . 8 , g i v i n g e q u i v a l e n t bending moment i n t h e room f l o o r a c t i n g a s a simple beam s u p p o r t ) . In

t h e worst c a s e t h e d i f f e r e n c e was l e s s t h a n 20 p e r c e n t and u s u a l l y i n t h e o r d e r of 2 t o

5

per c e n t ,

Office Loads; A Comparison of D i f f e r e n t Building Standards Table I11 summarizes and compares t h e o f f i c e l o a d s s p e c i f i e d i n B r i t a i n

( 3 ) ,

United S t a t e s ( 2 , 4 ) and Canada (1). Column ( 2 ) of t h e t a b l e shows t h e b a s i c l o a d which a p p l i e s t o medium-length s t r u c t u r a l members whose t r i b u t a r y a r e a s a r e approximated by t h e l i m i t s of 60 and 200 s q f t . S p e c i f i e d mean load i n c r e a s e s considerably w i t h a d e c r e a s e i n loaded a r e a and columns

( 3 ) ,

(4)

and

( 5 )

a r e p r o v i s i o n s e i t h e r f o r a c ~ n c e n t r a t e d load which a f f e c t s small spans, o r a r e d u c t i o n which a f f e c t s long spans o r l a r g e supported a r e a s . Reductions f o r v e r t i c a l members, such a s columns o r w a l l s , g i v e n i n

Column

( 5 )

a r e e i t h e r r e p r e s e n t e d by t h e number of f l o o r s c o n t r i b u t i n g load t o t h e member o r simply by t h e a r e a c o n t r i - b u t i n g load.

T h i s r a i s e s t h e q u e s t i o n of whether t h e r e i s any

d i f f e r e n c e i n t h e l o a d s which a r e l i k e l y t o occur i n a column when t h i n k i n g i n terms of f l o o r s c o n t r i b u t i n g i n s t e a d of a r e a c o n t r i b u t i n g ? It may a l s o be asked which approach b e s t

r e p r e s e n t s a c t u a l c o n d i t i o n s ? Column

(5)

shows t h a t g r e a t e r r e d u c t i o n s a r e p o s s i b l e f o r mean l o a d s by c o n s i d e r i n g f l o o r s c o n t r i b u t i n g load r a t h e r t h a n a r e a loaded. T h i s i n d i c a t e s

it i s more probable t h a t a l a r g e f l o o r a r e a w i l l have a high mean f l o o r load t h a n a number of c o n s e c u t i v e f l o o r s w i t h t h e same t o t a l area. T h i s may be due t o t h e i n f l u e n c e o f s i m i l a r f u n c t i o n s on t h e same f l o o r . Storage o f a c e r t a i n m a t e r i a l i s u s u a l l y found on t h e same f l o o r . Another p o s s i b l e r e a s o n f o r u s i n g f l o o r s loaded i n s t e a d of c o n t r i b u t i n g a r e a i s t h a t upper

TABLE: I11

Office Live Loads According t o Various Building Standards

50 lb/sq f t 2000 l b over

j0.15

when AT

>

200 ] Roof 0 , r o o f

+

1 12 l b / s q f t 1

2& f t x 2 3 f t

1

J f l o o r 0.15, roof ! p e r f o o t I

+

2 f l o o r s 0-20,

I lof w a l l

;

, I j e t c , dorm t o 0.50 : h e i g h t

50 lb/sq f t 2000 I b over .0.0008 (AT

-

150) 0.0008

(AT

-

1 5 0 ) 2 0 lb/sq ft'

2fr

_{f t}

_{x 2&}

_{f t}

_{/ o r , 0.231 (1}

+

_{D/L) o r , 0.231 (1}

+

_{D / L ) '}

o r , 0.60, whichever o r , 0.60, whichever,

1

1

, ' i s l e a s t i s l e a s t

I

j

American 2000 l b over r0.0008 (AT

-

150) ' 0.0008 ( A T

-

150) ' T o b e

i Standards '2& f t

x

23

f t : o r , 0.231 (1

+

D/L)' o r , 0,231 (1

+

D/L) , c o n s i d e r e d i

1

Assoc. l o r , 0.60, whichever! o r , 0.60, whichever,

i I

~ 5 8 1

-

1955 ' i s l e a s t i s l e a s t

f

I I P

1

B r i t i s h

i

50 lb/sq f t Slabs i ( F l o o r s c a r r i e d ' 1 / 1 0 u t .

i

0 A~ Standard

j

o f f i c e f l o o r s v ' l % / f t widthi0.05 (-), f o r

-

1) 0.1, up t o p a r t i t i o n j I

I Code of ! above e n t r a n o e d i s t r i b u t e d 500 0.40, OF, f o r p e r f t r u n

I

;;;;tice f l o o r m i f or-

_In,>

500 , AT

>

500, *05

Inor

<

20

1

ems

i

I

(af/500) up t o

; lb/aq f t

I / 13200 l b , u p t o 0.25

1

0 . 2 5 , w h i c h e v e r i 6

i

[ d i s t r i b u t e d i s g r e a t e r I

i

i I I I hnif ormly , I :

I

1

Standard

1

100 lb/sq f t . S l a b s i , o f f i c e s u s e d ' 8 0 0 b / f t width Same a s

! f o r s t o r a g e d i s t r i b u t e d Same as above . Same a s above above f _{and f i l i n g uniformly}

Basic Uniformly j I

,

*

REDUCTIOhS ( o f t o t a l l i v e l o a d ) I I

D i s t r i b u t e d j Concentrated

I

Beams G i r d e r s j Foundations

/

Movable DesianLoad i Load

1

Trusses

'

columns P i e r s Walls . P a r t i t i o n s '

j purposes

:

I

d i s t r i b u t e d I I

*

Symbols AT f l o o r area supported by member i n s q f t D dead load lb/aq f t

To compare t h e d i f f e r e n t s t a n d a r d s g r a p h i c a l l y , Fig. 2 shows t h e v a r i a t i o n of s p e c i f i e d o f f i c e mean f l o o r l o a d s w i t h

a r e a , t h e most s i g n i f i c a n t v a r i a b l e . Only t h e B r i t i s h Standard s p e c i f i c a t i o n f o r " o f f i c e s usod f o r s t o r a g e and f i l i n g purposes" (100 lb/sq f t ) i s included s i n c e t h e s p e c i f i c a t i o n f o r 'off i c e f l o o r s above t h e e n t r a n c e f l o o r " resembles t h e NBC s p e c i f i c a - t i o n c l o s e l y . For s h o r t members, t h e NBC and ASA s p e c i f y a c o n c e n t r a t e d load whereas t h e B r i t i s h Standard s p e c i f i e s a c o n s t a n t l o a d spread uniformly.

Thus t h e d i f f e r e n c e between t h e B r i t i s h and American s p e c i f i c a t i o n s f o r c o n c e n t r a t e d load i n Table I1 w i l l almost d i s a p p e a r when t h i n k i n g i n terms o f bending moment i n a simple beam, I n applying column r e d u c t i o n s based on t h e number of f l o o r s f o r Fig. 2, a f l o o r a r e a of 500 sq f t i s used.

Although t h e ASA has a h i g h e r b a s i c l o a d , it has h i g h e r r e d u c t i o n s and g e n e r a l l y t h e l o a d s a r e s i m i l a r t o t h e o t h e r codes f o r small members and l a r g e members. The r e a s o n s f o r

t h e change from 50 l b / s q f t w i t h a small r e d u c t i o n t o 80 l b / s q f t w i t h a l a r g e r e d u c t i o n a r e d i s c u s s e d i n Dunhamfs p a p e r s ,

Loads much over

SO

l b / s q f t have occurred i n o f f i c e b u i l d i n g s and it was f e l t t h a t 80 l b / s q f t accompanied by a h i g h e r reduc- t i o n would g i v e a b e t t e r balanced d e s i g n w i t h l e s s chance of o v e r s t r e s s . The ASA r e d u c t i o n .231(1

+

D, s i g n i f i e s t h a t i f

Z

t h e e n t i r e a r e a were loaded t o t h e b a s i c l i v e load L, no p a r t would be o v e r s t r e s s e d more t h a n 30 p e r c e n t . It was thought t h a t t h e r e w a s l e s s r i s k of exceeding 80 l b / s q f t t h a n

50 l b / s q f t over t h i s " e n t i r e a r e a " . The B r i t i s h Standard Code of P r a c t i c e accounts f o r b o t h f l o o r s and a r e a i n r e d u c i n g

column l o a d s where columns have a r e d u c t i o n of a t l e a s t t h e e q u i v a l e n t o f beams and s l a b s f o r a r e a loaded.

A l s o included i n Fig. 2 a r e Whitefs r e c o r d s a p p l i e d

t o t h e normal p r o b a b i l i t y curve f o r s l a b s , beams and columns ( 1 0 ) . The curve i s expressed by:

W = X

?

l o ad +

326

7

7

P

mean s t a n d a r d d e v i a t i o n

t

f o r u n i t a r e a s x i s a c o e f f i c i e n t which depends on t h e p r o b a b i l i t y of being exceeded ( i . e . t h e a r e a under t h e normal curve beyond W ) .

For a p r o b a b i l i t y l e v e l of 1 i n 1000, x

= 3.13.

A i s t h e a r e a . For beams, A = 2a s i n c e t h e a c t u a l load i s shared between two beams. S i m i l a r l y f o r columns,

For o f f i c e s not p r i m a r i l y intended f o r s t o r a g e , t h e maximum probable mean load f o r any but a small a r e a w i l l depend on t h e probable arrangements of t h e sources t ~ h l c h i n c l u d e s t o r a g e and p r o p e r t y , persons, impact and v i b r a t i o n s . For small a r e a s arrangement w i l l not be a f a c t o r . I f i t i s assumed t h a t t h e worst arrangements during t h e l i v e s of

d i f f e r e n t f l o o r a r e a s a r e random, then t h e mean l o a d expected f o r a given p r o b a b i l i t y w i l l d e c r e a s e w i t h an i n c r e a s e of a r e a , and i t s decrease r a t e w i l l l e s s e n w i t h an e x t e n s i o n of a r e a . The normal curve has t h e s e c h a r a c t e r i s t i c s . How well assump- t i o n s of random arrangements can be r e l i e d upon, however, and whether t h e normal curve i s c o r r e c t , might be s u b s t a n t i a t e d by

sampling. White's m d Dunham's r e c o r d s s u b s t a n t i a t e t h e normal curve t o a minor e x t e n t but they a r e very small samples, On t h e o t h e r hand t h e b u i l d i n g standards s p e c i f y l o a d s which decrease i n t e r m i t t e n t l y and remain t h e same between 50 s q f t and 200 o r 500 s q f t . I n a d d i t i o n t h e ASA l o a d s p e c i f i c a t i o n d e c r e a s e s a t a c o n s t a n t r a t e . Regarding t h e l i m i t s of d e f i n i t i o n a t t a c h e d t o t h e t e r m " o f f i c e " , t h e B r i t i s h Standard s t a t e s i t s c a s e more c l e a r l y t h a n t h e o t h e r codes. It s p e c i f i e s 50 l b / s f t f o r " o f f i c e f l o o r s above t h e e n t r a n c e f l o o r " and 100 l b

3

sq f t f o r " o f f i c e f l o o r f o r s t o r a g e and f i l i n g purposes" whioh i s much more r e a s o n a b l e t h a n t h e NBC o r ASA. I f , however, t h e r e i s doubt a s t o t h e intended u s e of t h e o f f i c e a r e a perhaps 80 l b / s q f t should be used,

Loads Due t o Computing Machinery and S a f e s

A t t h e r e q u e s t of t h e Adviaory S t r u c t u r a l Group of t h e N a t i o n a l Building Code, e n q u i r i e s were made r e g a r d i n g t h e

weights and loaded a r e a s of computing machinery. The following i s a summary of information r e c e i v e d through t h e a s s i s t a n c e of

M r , D,M. Rosevear of I n t e r n a t i o n a l Business Machines. It was found t h a t only IBM s o l d heavier computing machines e x t e n s i v e l y . Therefore, machines l i s t e d by IBM w i l l be predominant when

c o n s i d e r i n g extreme weights.

E l e c t r o n i c data-processing machines weigh a s much a s 5000 l b but a r e r e l a t i v e l y r a r e i n o r d i n a r y o f f i c e use. The manufacturer r e q u i r e s a f l o o r designed f o r a 200-lb/sq f t l o a d

i f a r a i s e d f l o o r i s n o t used. Generally, a r a i s e d f l o o r i s d e s i r a b l e t o accommodate t h e s e r v i c e s ( w i r e s ) r e q u i r e d f o r such machines, E l e c t r i c accounting machines a r e more widely used and Table I V r e p r e s e n t s extremes taken from t h e manual

" I n s t a l l a t i o n I n s t r u c t i o n s f o r IBM E l e c t r i c Accounting Machines" ( 11 )

.

TABLE

IV

IBM Machines o v e r 2500 l b and 100 l b / s q f t

The s p e c i f i e d NBC c o n c e n t r a t e d l o a d o f 2000 l b i s exceeded by 60 p e r c e n t by one o f t h o machines a s a t o t a l l o a d b u t o n l y 70 p e r c e n t o f i t s moan area l o a d i s approached.

Occurrence of l o a d s duo t o s a f e s were r e p o r t e d i n t h e l o a d survey of t h e E q u i t a b l e B u i l d i n g , New York i n 1922, which covered what was t h e n t h e l a r g e s t o f f i c e b u i l d i n g i n t h e world.

" O f

35

s a f e s and s a f e c a b i n e t s , 22 weighed l e s s t h a n 1000 l b ;

5

between 1000 and 2000 l b ; 2 e a c h w8ighed 2200 l b and 2360 l b ; one each weighed 2800 l b , 3000 l b , 3500 l b , and 4.250 l b " ( 1 2 ) .

Machinos The a u t h o r b e l i e v e s t h a t , based on t h e i n f o r m a t i o n a v a i l a b l e , t h e 2000-lb c o n c e n t r a t e d l o a d assumption of t h e NBC i s a d e q u a t e f o r t h o p r e s e n t because (1) t h e o c c u r r e n c e of rrmhines of w e i g h t s g r e a t e r t h a n 2000 l b i s s t i l l r a r e i n any l a r g e sample of t y p i c a l o f f i c e s p a c e and it i s u n l i k e l y t h a t

73

machine i n t r o d u c e d some advantage of t h e f l o o r s t r u c t u r e c a n o f t e n be g a i n e d w i l l b e surrounded by o t h e r machines;

by p r o p e r p o s i t i o n i n g , keeping i n mind t h e r o u t e of moving t h e machines. To hnvo every p o s i t i o n o f t h e f l o o r a r e a d e s i g n e d f o r t h e worst c o n c e n t r a t e d l o a d i s uneconomic.

( 3 )

People a r e g e n e r a l l y aware of t h e p o s s i b l e consequences i n v o l v e d i n i n t r o - d u c i n g such a heavy machine o r s a f e .

M a x i m u m Weight l b 2751 2850 3286 2530 B e 402 403 404 CPC I n c o n n e c t i o n w i t h t h e p r e s e n t r e v i e w of f l o o r l o a d s due t o computing machines a v i s i t was made by t h e a u t h o r t o t h e

Name Accounting machine 11 11 11 1 I Card

-

p r o g r a m e d e l e c t r o n i c c a l c u l a t o r Type 4 9 1 a c c o u n t i n g machine Loaded Area s q f t 20.3 20.3 15.7 20.1 f o r comparison N a t i o n a l B u i l d i n g Code Mean Load l b / s q f t 136

141

209 126 320

-

I

2000 6.25

Mechanical T a b u l a t i o n s D i v i s i o n of t h e Dominion Bureau o f S t a t i s t i c s s i n c e i t was expected t o p o s s e s s a n extreme o c c u r - r e n c e o f a r r a n g e d computing machines. The f o l l o w i n g i s a b r i e f summary o f i n f o r m a t i o n o b t a i n e d w i t h t h e a s s i s t a n c e of

M r . W . I . Moore of t h e Bureau.

It was found t h a t a l l machines were spaced r e l a t i v e l y f a r a p a r t t o p r o v i d e a d e q u a t e s p a c e f o r p e o p l e t o o p e r a t e them and t o move about. The h e a v i e s t machine neighed 2700 l b ( ~ y p e 402, Table I V ) and t h e approximate " t r i b u t a r y " a r e a was loaded t o

15

l b / s q f t . The " t r i b u t a r y " a r e a under t h e machine i n c l u d e s one-half t h e unused s p a c e around t h e machine. Uncomfortable v i b r a t i o n s had been experienced when t h e frequency of v i b r a t i n g machines was i n c r e a s e d from 80 t o 100 c y c l e s p e r minute. These were overcome by moving t h e machines n e a r e r t o t h e column.

I n t h e same D i v i s i o n much g r e a t e r f l o o r l o a d s w e r e observed from f i l i n g c a b i n e t a completely f i l l e d w i t h c a r d s , One 25- by 2 5 - f t bay had a mean load of 1 2 5 l b / s q f t produced by c a r d c a b i n e t s g i v i n g a d i r e c t l o a d of 220 Ib/sq f t . T h i s o c c u r r e n c e r e p r e a e n t s a n extreme w i t h l i t t l e p r o b a b i l i t y of o v e r l o a d because t h e c a b i n e t s were c o m p l e t e l y f i l l e d , s t a n d i n g c l o s e t o g e t h e r and a s h i g h as t h e y could be u s e f u l l y used,

The c a b i n e t s could be s t a c k e d h i g h e r b u t a l a d d e r d e v i c e would b e needed. These o b s e r v a t i o n s i n d i c a t e t h a t t h e consequences of l o a d s due t o s t o r a g e of f i l e s , c a r d s , books, e t c . a r e much l e s s l i k e l y t o be noted by t h e p e o p l e concerned t h a n t h e l o a d s r e s u l t i n g from heavy o f f i c e machines.

Conclusions

Recent computing machines used i n o f f i c e s weigh up t o 5000 l b b u t t h o s e weighing over 2000 l b a r e r a r e and s p e c i a l c o n s i d e r a t i o n a p p e a r s t o b e g i v e n by t h e manufacturer t o t h e r e s u l t i n g f l o o r l o a d . E l e c t r o n i c d a t a - p r o c e s s i n g machines, t h e h e a v i e s t t y p e o f o f f i c e machinery, u s u a l l y r e q u i r e a r a i s e d f l o o r t o accommodate s e r v i c e s t o t h e machine. T h i s r a i s e d f l o o r w i l l h e l p t o d i s t r i b u t e t h e l o a d , Recommendations 1. Occupancy l o a d s should b e p r o p e r l y c l a s s i f i e d a c c o r d i n g t o t h e t y p e - and magnitude of t h e l o a d i n a expected, It i s

submitted t h a t t h e t y p e may b e T-% e t e r m ned by c o n s i d e r a t i o n of t h e f o l l o w i n g t w o - s o u r c e s ; s t a t i c and dynamic. The s t a t i c l o a d s c o n s i s t o f an assembly of p e r s o n s , p r o p e r t y and s t o r a g e , Probable l o a d s i n any a r e a a r e due t o

2. Based on t h e above c l a s s i f i c a t i o n , samples of occurrencea should be obtained i n t h e form of frequency diagrama f o r each occupancy type o r c l a s s . I n t a k i n g samples, t h e geo- metric i n f l u e n c e s such a s a r e a which may a f f e c t t h e probable

loading should be included.

3.

The r e s u l t s of t h e s e samples should provide more r e a l i s t i c loading p a t t e r n s f o r t h e occupancy t y p e , To g i v e more r e a l i s t i c loading p a t t e r n s expected a t l e a s t some s t a t i s - t i c a l i n t e r p r e t a t i o n i s r e q u i r e d , The expected loadings w i l l be based on t h e sample, t h e l i m i t s of t h e type of occupancy including ohange of usage, and expected changes of t h e sources of loading and t h e i r magnitude.

Acknowledgments

The Divison wishes t o express i t e a p p r e c i a t i o n t o M r . D.M. Ro sevear of I n t e r n a t i o n a l Business Machine8 Corp, f o r supplying information on weights of computing machinery and t o M r . W , I . Moore of t h e Dominion Bureau o f S t a t i s t i c s f o r a s s i s t i n g and supplying information a t t h e Mechanical Tabulations Division of t h e Bureau.

The a u t h o r wishes t o expresa h i s a p p r e c i a t i o n t o t h e following members of t h e Building S t r u o t u r e e Section,

A,G, Davenport f o r h i s suggestions on dynatnlo l o a d s and W,R. Schriever f o r h i s a a s i s t a n o e i n p r e p a r i n g t h e r e p o r t ,

1, National Building Code of Canada (1953 )

,

P a r t

3.

Use and

Occupancy, P a r t

4.

Design: General Requirements, National Research Council, Ottawa,

2, U,S, National Bureau of Standards, Minimum deaign l o a d s i n b u i l d i n g s and o t h e r s t r u c t u r e s . Amerioeui Standards Association, New York 1956, 2 9 ~ .

3.

B r i t i e h Standard Code of P r a c t i c e , Code of f u n c t i o n a l requirements of b u i l d i n g s ; Chapter

1;

loading, London 1952, 33p.

4.

uniform Building Code, 1955 E d i t i o n , Volume 1. P a c i f i o Coaet Building Off i c i a l e Conference, LOB Angelea. 3 8 3 ~ .

5.

Howe, W,B,W,, Charles Worthington e t

a l ,

Discussion of

C.C, Schneider a paper, t h e s t r u c t u r a l design of b u i l d i n g s , Transaction8 of A,S.C,E., Vol. L N , June 1905, p.413-489,

6, Johnson, Arne. S t r e n g t h , s a f e t y and economical dimensions of s t r u c t u r e s , Swedish S t a t e Committee f o r B u i l d i n g Research, B u l l e t i n 22, Stockholm 1951, 168p,

7, Freudenthal, A.M. S a f e t y and p r o b a b i l i t y of s t r u c t u r a l f a i l u r e . T r a n s a c t i o n s of AoSoCeEes Vol. 121, 1956,

P O 133701375.

8. White, C.M. Survey of l i v e l o a d s i n o f f i c e a . F i r s t I n t e r i m Report of t h e S t e e l S t r u c t u r e s Research Committee,

HoMoSoOos London, 1931, p. 45-65.

9. Dunham, J , W , Design l i v e l o a d s

i n

b u i l d i n g s . T r a n s a c t i o n s of A o S e C e E . , Vole 112,

1947, P O

725-745.

10. Horne,

M,R,

The v a r i a t i o n of mean f l o o r load8 w i t h a r e a . Engineering, Vol. 1 7 1 , February

1951,

p. 179-182.

11. I.B.M. World Trade Corporation. I n s t a l l a t i o n i n s t r u c t i o n s f o r 1.B.M. E l e c t r i c Accounting Machines, S a l e s

k g i n e e r i n g Department, New York. 1957.

12. A atudy of o f f i c e b u i l d i n g l i v e - l o a d s baaed on a atudy

by C O T . Coley., Engineering News-Record, Vol. 90, NO. 13,

March 1923, p. 584-586.

Bibliography

Schneider, C.C. The s t r u c t u r a l d e s i g n of b u i l d i n g s . Transac- t i o n s of A.SoCoEes Vol. LIV, June 1905, P O 371-412.

T i l d e n , C,J. K i n e t i o e f f e c t s of crowds, T r a n s a c t i o n s of

A.S.C,E,, Vol. LXXVI, December

1913,

p. 2107-2126.

I s a a c s , D.V. The s t r u c t u r a l sufficiency of domestic b u i l d i n g s , Commonwealth Experimental Building S t a t i o n , Sydney

,

Aunt.

,

B u l l e t i n No, 1, June 1956, Sop.

D u n h a m , J.W., G o N . Rrekke, and G.N, Thompson. Live l o a d s on f l o o r s i n b u i l d i n g s . U,S, Nat, Bur. of 3 x n d a r d s , BMS

Heport 133, Washington, Deoember 19, 1952, 27p.

Baker, J,F,, M.R. Horne and J e Heyman. The a t e e l s k e l e t o n ,

Vol. 11, C h . 16: The l o a d f a c t o r . Cambridge U n i v e r s i t y P r e s s , 1956.

J u l i a n , 0.G. Synopsis of t h e F i r s t P r o g r e s s Report of t h e Committee on F a c t o r s of Safety. J o u r n a l of A.S.C.E,, S t r u c t u r a l Division, Paper 1316, J u l y 1957, 22p,

-

_I

I

I

I

I

'

I l l

I

1

I

'

I I l l 1

I

I

I

I 1

I I L '

-

_-

DUNHAM'S RECORDS (INTERNAL REVENUE WHITE'S RECORDS

,

1931

-

_-

-

BUILDING) APPLIED TO NORMAL 0 MAXIMA FROM SAMPLE OF 140,000 SQ F T

-

-

PROBABILITY CURVE FOR PROBABILITY OF 8 DIFFERENT OFFICE BUILDINGS.

-

MAXIMA PRACTICABLE BY CONSIDERING FILING

-

AND BOOKS ON SHELVES.

DUNHAM'S RECORDS

,

1947

-

X MAXIMA FROM SAMPLE OF 400,000 SQ F T OF

2 GOVERNMENT BUILDINGS , INTERNAL REVENUE

BUILDING

,

VETERAN'S ADMINISTRATION B U I L D I N K

CARDS

-

-

-

-

-

-

-

-

-

-

MAXIMA OCCURRING IN MECHANICAL

-

TABULATIONS DIVISION

-

_NOTE:

FOR ROW LOADING (i.e. CABINETS)

-

_{AREA LENGTH IS TAKEN AS}

TWICE THE WIDTH PROBABILITY CURVE FOR PROBABILITY

OF I IN 1000 (HORNE)

I

I

I

I

I l l 1 1

I

I

I

I

I

I l l 1

I

I

I

I I I I I

LOADED AREA (SQUARE F E E T )

FIGURE

I

- _{ACCORDING TO:}

-

_-

-

NATIONAL BUILDING CODE 1953.

-

111 AMERICAN STANDARDS ASSOClATlON A 58.1

-

1955.

-

-.-

BRITISH STANDARD CODE OF PRACTICE 1 9 5 2 - OFFICES

USED FOR STORAGE AND FILING PURPOSES.

-

WHITE'S DATA APPLIED TO NORMAL PROBABILITY -

CURVE FOR PROBABILITY OF I IN 1000 BY HORNE.

NOTE: PART a REPRESENTS SPECIFIED CONCENTRATED LOAD

-

(NBC AND ASA) WHEREAS A L L OTHERS REPRESENT SPECIFIED DISTRIBUTED LOAD.

.-.-.-.

*--

-

-

-

-.

*-. _{BEAMS 8 GIRDERS} - 7

-

- * . COLS 8 FOOTINGS . . a

-

7

-

BEAMS 8 GIRDERS - ASSUMPTIONS :

-

I

NUMBER OF FLOORS, EACH COLUMN IS ASSUMED TO BE

LOADED BY 5 0 0 SQ. FT. AT EACH FLOOR.

@ SLABS ARE ASSUMED SQUARE FOR BRITISH

STANDARD CODE OF PRACTICE

LOADED AREA (SQUARE FEET)

FIGURE

2

N A T I O N A L R E S E A R C H C O U N C I L D I V I S I O N OF B U I L D I N G R E S E A R C H E R R A T A T O DBR I N T E 3 N . A L R E P O R T NO,

149

FLOOR LOADS I N B U I L D I N G S With P l r t i c u l a r R e f e r e n c e t o O f f i c e s by D.E. A l l e n p e l p a r a . 1 2 5 b y 2 5 f t . should r e a d 2.5 by

2.5

f t r