Tests on the lateral strength of concrete block walls at Aultsville

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N A T I O N A L

RESEARCH

C O U N C I L

CANADA

D I V I S I O N O F B U I L D I N G RESEARCH

TESTS

,ON

THE

LATERAL STRENGTH O F

CONCRETE BLOCK

WALLS

AT AULTSVILLE

by

W. G. Plewes

Internal

Report

No.

239

of

the

Division of

Building

Research

OTTA1iVA

November

1961

Advantage was t a k e n of t h e o p p o r t u n i t y t o c a r r y o u t s t r u c t u r a l t e s t s on b u i l d i n g s t o be removed o r demolished i n t h e a r e a t o be f l o o d e d b y t h e c o n s t r u c t i o n of t h e S t . Lawrence Power P r o j e c t . Only one b u i l d i n g r e p r e s e n t a t i v e of c u r r e n t con- s t r u c t i o n p r a c t i c e s was f i n a l l y s e l e c t e d f o r s t u d y . The r e s u l t s of l o a d i n g t e s t s on t h e c o n c r e t e b l o c k masonry w a l l s of t h i s b u i l d i n g a r e now r e p o r t e d . They a r e r e v e a l i n g i n t h a t t h e y i l l u s t r a t e b o t h t h e l i m i t a t i o n s and b e n e f i t s t o be d e r i v e d from f i e l d l o a d i n g t e s t s on a c t u a l s t r u c t u r e s . l l h e work was c a r r i e d o u t by t h e s t a f f 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 . The a u t h o r , a c i v i l e n g i n e e r , i s a r e s e a r c h o f f i c e r w i t h t h e D i v i s i o n h a v i n g s p e c i a l i n t e r e s t s i n c o n c r e t e s t r u c t u r e s . Ottawa November 1 9 6 1 A s s i s t a n t D i r e c t o r

N.

B. Hutcheon

TESTS ON THE TtATGItAE STRENGTH 01" CONCRETE BLOCK WALLS AT

AULTSVILLE

This r e p o r t d e a l s w i t h t h e r e s u l t s of load t e s t s on s e l e c t e d w a l l p a n e l s of a c o n c r e t e b l o c k b u i l d i n g a t A u l t s v i l l e , Ontario. The o p p o r t u n i t y t o use t h i s b u i l d i n g f o r t e s t s presented i t s e l f w i t h t h e construe-tion of t h e S t . Lawrence Power P r o j e c t , when t h e f l o o d i n g of l a n d s n e c e s s i t a t e d t h e r a z i n g o r removal of a l l b u i l d i n g s i n s e v e r a l v i l l a g e s and farms.

I t appeared a t f i r s t t h a t load t e s t s might be made on a number of t h e s e b u i l d i n g s and u s e f u l i n f o r m a t i o n obtained which would a s s i s t with t h e planning of a proposed l a b o r a t o r y

s t u d y of t h e s t r e n g t h of masonry w a l l s and t h e d e s i g n of l o a d t e s t a p p a r a t u s . T e s t s on a c t u a l s t r u c t u r e s would a l s o ,

it

was thought, be of some h e l p i n c o r r e l a t i n g l a b o r a t o r y t e s t s w i t h f i e l d c o n d i t i o n s .

Permission was _{obtained from t h e Hydro E l e c t r i c}

Power C o m i s s i o n of Ontario t o use some of t h e . b u i l d i n g s f o r t h i s purpose, and a survey was made t o s e e what might be done.

The b u i l d i n g s scheduled f o r d e m o l i t i o n were houses, churches, s c h o o l s , and an o c c a s i o n a l commercial b u i l d i n g

v a r y i n g from 50 t o 150 y e a r s o l d , t h e m a j o r i t y of them 80 o r 90 y e a r s of age. Many o f them o r i g i n a t e d a s modestly-sized b u i l d i n g s b u t had r e c e i v e d one o r more a d d i t i o n s over t h e y e a r s , o f t e n of d i f f e r e n t c o n s t r u c t i o n . Examination of t h e b u i l d i n g s r e v e a l e d i n t e r e s t i n g i n f o r m a t i o n concerning t h e

c o n s t r u c t i o n methods of former days. Walls were g e n e r a l l y 8 - i n . s o l i d b r i c k

o r

1 0 - t o 1 2 - i n . c a v i t y w a l l s . Lime mortar w a s t h e r u l e . Rubble w a l l s and hand-hewn beams were found

i n almost a l l basements. J o i s t and r a f t e r s i z e s and s p a c i n g s were q u i t e i r r e g u l a r , and connections were made w i t h wrought

i r o n square n a i l s o r even wooden pegs. The i n n e r wythe of c a v i t y w a l l s f r e q u e n t l y had wooden members

o r

f u r r i n g s t r i p s embedded i n t h e brickwork, and a t l e a s t one w a l l had a l a y e r of s h e a t h i n g i n t h e c a v i t y , presumably a n i n t u i t i v e a t t e m p t a t i n s u l a t i o n .

Because of t h e outdated d e s i g n s of most of t h e s t r u c t u r e s ,

it

was thought t h a t t h e c o n c e n t r a t e d e f f o r t and probable expense involved i n load t e s t s would n o t be .warranted by t h e amount of u s e f u l i n f o r m a t i o n obtained. One b u i l d i n g , however, a former cheese f a c t o r y i n A u l t s v i l l e , O n t a r i o , w a s

of c o n c r e t e b l o c k c o n s t r u c t i o n , about 30 y e a r s o l d , and i n good c o n d i t i o n . Since

i t s

c o n s t r u c t i o n was t y p i c a l of some p r e s e n t day b u i l d i n g s ,

it

was decided t o c a r r y o u t a l i m i t e d number of simple t e s t s on i t s w a l l s u s i n g equipment immediately

DESCRIPTION

OF

--- THE BIJIP~DTNCI _.-

The buildinlz chosen f o r t h e t e s t i s shown i n F i g . 1.

The w a l l s e e n i n t h e figure consis1;ed of a s e r i e s of c o n c r e t e b l o c k p a n e l s s e p a r a t e d b ; ~ r~indow openings. I t was 10 f t

4

i n . h i g h ( 1 5 c o u r s e s ) , made of 8 - i n . h o l l o w block w i t h a

5

i n . of p l a s t e r r e n d e r i n g on t h e i n s i d e f a c e . The f a r s-ide of t h e

b u i l d i n g w a s o f s i m i l a r c o n s t r u c t i o n w i t h t h e a d d i t i o n of a s m a l l o f f i c e extension and l o a d i n g p l a t f o r m s .

The w a l l s o f t h e b u i l d i n g r e s t e d on a ].ow c o n c r e t e f o u n d a t i o n vial1 which w a s _{i n} good c o n d i t i o n and showed no s i g n s of weakness o r rnovemcnt t h r o u g h o u t t h e t e s t s . Roof r a f t e r s and c e i l i n g jo-l.sts were c a r r i e d on a p l a t e b o l t e d t o t h e t o p of t h e w a l l w i t h & - i n . b o l t s a t

7 - f t

c e n t r e s ( F i g . 2 ) .

The c o n c r e t e b l o c k s used i n t h e jail were 8- b y 8- by 1 6 - i n . t w o - c e l l e d

~ m i t s

havi.ng ? - i n . f a c e s h e l l s and l & - i n .

webs. Probab1.y from a g e , t h e u n i t s had a h i g h compressive s t r e n t h a v e r a g i n g 5610

_B

p s i on t h e n e t a r e a . M o r t a r j o i n t s were i n . t h i c k : t h e m o r t a r a p p e a r e d t o b e a m i x t u r e of

cement and l i m e , v e r y hard, and g e n e r a l l y s t r o n g l y bonded t o t h e u n i t s .

Numerous c r a c k s were n o t e d i n t h e p l a s t e r on t h e i n s i d e of t h e w a l l s t h a t f o l l o w e d t h e p a t t e r n of t h e m o r t a r j o i n t s behind. S i n c e t h e r e were no s i g n s of s t r u c t u r a l movement, s h r i n k a g e w a s presumed -to be t h e c a u s e .

SEUJCTIOB

OF

PANELS S h o r t masonry w a l l s s u p p o r t e d on f o u r s i d e s un- d o u b t e d l y

d e r i v e

t h e i r r e s i s t a n c e t o l a t e r a l f o r c e s from a p l a t e a c t i o n t h a t i s d i f f i c ! u . l t t o a s s e s s due t o t h e non- homogeneity of t h e m a t e r i a l s . I n t h e c a s e of a l o n g w a l l , however, t h e s t r e n g t h of t h e c e n t r e p o r t i o n can b e t a k e n a s t h e sum of t h e s t r e n g t h s of v e r t i c a l s t r i p s s u p p o r t e d t o p and bottom, which a r e e a s i e r t o a n a l y z e .

To keep t h e t e s t s s i m p l e and t o f a c i l i t a t e e x e c u t i o n and i n t e r p r e t a t i o n , i t v:as d e c i d e d t o t e s t f o u r p a n e l s o n l y , and t o i s o l a t e t h e p a n e l s nunbesed 1, 2 and

3

i n Pig. 1 b y

h o c l r i n g o u t t h e b l o c l ~ v o r l c above and. below t h e vrindows. T h i s r e s u l t e d i n t h r e e v e r t i c a l s t r i p s o:f a t y p i c a l c o n c r e t e b l o c k w a l l ( P i g .

3 ) .

The edges were l e f t saw-toothed t o a v o i d

damaging t h e vralls by an a t t e m p t t o t r i m t h e e d g e s of t h e p a n e l s . I t was though-t t h . a t t h e p r o j e c t i n g b l o c k s would n o t a f f e c t t h e t e s t s v e r y much, e x c e p t by v i r t u e of a l i t t l e e x t r a w e i g h t .

F311cl

4

(Pi{;s. 1 rind

4.

) Y I : ~ ? : ; much l a r g e r and r e p -

r e s e n t e d a d i f le:r-erlt; condi.tiou. !Ill-~i :: w:~l.l. vra:; p a r t of' a n e x t e n s i o n

t o

t h e main builtlini; and vras n o t p l a s t e r e d on t h e i n s l d e

.

The edge o:f -the pailel abut;-L-j.ng t h e o r i g i n . a 1 b u i l d i n g was n o t bonded t o i t , i . e . i t v a s freestanding. The o t h e r

end was i n t e g r a l w i t h t h e end w a l l of t h e e x t e n s i o n . I t t h u s r e p r e s e n t e d a wall s u p p o r t e d on t h r e e ed.g$s, and i t was t h o u g h t t h a t a u s e f u l cornpar-ison might; be made between t h e s t r e n g t h of t h i s w a l l and a s i m i l a r one s u p p o r t e d o n l y t o p and bottom u s i n g t h e ::tren@h d.ata o b t a i n e d from P a n e l s 1,

2 and

3.

The dimensions of t h e p a n e l s a r e g i v e n i n P i g .

LOADING METHOD

A s p r e v i o u s l y n o t e d , t h e t e s t s were done u s i n g , t h e m a t e r i a l and equipment r e a d i l y a v a i l a b l e . F o r t h i s reason. t h e l o a d i n g system shown i n Pigs.

5

( a ) and ( c ) was a d o p t e d .

!Pwo h o r i z o n t a l line l o a d s were a p p l i e d a t t h e t h i r d p o i n t of e a c h p a n e l 1 t o

3

t h r o u g h 2$-in. d i a m e t e r p i p e s , These were yoked t o g e t h e r by 8- by 8 - i n . t i m b e r s and a s t e e l beam. A 2 - i n . r o d was bolted t o tlie s t e e l beam, passed t h r o u g h

a s m a l l h o l e a t t h e c e n t r e of t h e t e s t p a n e l and c a r r i e d a c r o s s t h e b u i l d i n g t o t h e f a r w a l l . It w a n passed t h r o u g h t h e far w a l l and t h r o u g h a 100--lion c e n t r e - h o l d Simplex jack. S i n c e t h e d e f l e c t i o n s of t h e t e s t p a n e l s were expected t o be g r e a t e r t h a n t h e jack e x t e n s i o n , a s t e e l s t o o l was p r o v i d e d below t h e j a c k s o t h a t t h e l o a d could be " t i e d o f f " w i t h a n u t w h i l e t h e j a c k was r e t r a c t e d and r e s e t . F u r t h e r 8 - by 8 - i n . t i m b e r s below t h e s t o o l s p r e a d t h e j a c k r e a c t i o n o v e r t h e r e a c t i o n w a l l . A t t h e t e s t p a n e l t h e l o a d i n g assembly was s u p p o r t e d on r o l l e r s t o a v o i d a n y a d d i t i o n t o t h e normal v e r t i c a l w a l l l o a d s ( F i g . 6 ) . F o r w a l l p a n e l 4 t h e l i n e l o a d s were n o t c o n t i n u o u s b u t n e a r l y s o ( P i g s . 5 ( b ) and

7 ) -

I n t h i s c a s e t h e y were a p p l i e d i n 5 - f t l e n g t h s spaced a b o u t 1 f t a p a r t a l o n g t h e l e n g t h of t h e w a l l . Four such l o a d s were yoked t o one jack. Thus, two j a c k s were r e q u i r e d . The r e a c t i o n and j a c k i n g arrangements 01.1 t h e f a r w a l l were t h e same a s p r e v i - o u s l y d e s c r i b e d f o r t h e oth.er p a n e l s .

MEASUREMENTS

OF DEFLECTION

D e f l e c t i o n s were measured by means of two d i a l gauges ( r e a d i n g t o ,001) s t r a d d l i n g -the cen-l-re l i n e of t h e w a l l on t h e i n s i d e ( F i g s . 8 and 9 ) . I n a d d i t i o n , w i r e s were

a t t a c h e d a t 6 p o i n t s on t h e 011-tside o f t h e - u z l l a l o n g t h e

v e r t i c a l c e n t r e l i n e f o r p a n e l s 1 t o

3,

and. a t

1 7

p o i n t s a l o n g h o r i z o n t a l and v e r t i c a l l i n e s Tor p a n c l 4 ( P ~ c . €3). These w i r e s w i t h a 1 - l b weight a t t h e end of each were c a r r i e d by

a system of p u l l e y s t o a rnarlring board ( P i g .

7 )

s o t h a t t h e d e f l e c t i o n s c o u l d b e r e c o r d e d (Sca3.e 1: 1) on a c h a r t .

LOADING SEQUENCE

The l o a d was a p p l i e d t o w a l l p a n e l s 1 and 2

i n

i n c r e m e n t s of a p p r o x i m a t e l y 1 0 0 l b a t t h e jack. The l o a d a t e a c h increment was h e l d f o r a b o u t

7

minutes w h i l e b o t h t h e d i a l gauges and d e f l e c t i o n board r e a d i n g s were r e c o r d e d . Loading was d i s c o n t i n u e d when t h e l o a d r e a c h e d a maximum and remained c o n s t a n t , o r d e c r e a s e d w i t h i n c r e a s i n g d e f l e c t i o n . The l o a d was t h e n d e c r e a s e d i n t h r e e e q u a l s t e p s t o z e r o .

F a n e l

3

was t e s t e d i n e s s e n t i a l l y t h e same way e x c e p t t h a t l o a d i n g was con-tinued t o a c t u a l c o l l a p s e . F i g . 1 0 shows p a n e l

3

u n d e r l o a d a t a n advanced s t a t e of d e f l e c t i o n .

P a n e l 4 was l o a d e d t h r o u g h two jacks. The l o a d s

on t h e j a c k s were k e p t e q u a l s o t h a t t h e two l i n e l o a d s were a t a l l t i m e s e s s e n t i a l l y uniform a l o n g t h e w a l l . Loading i n c r e - ments were 100 l b a t e a c h jack and d e f l e c t i o a r e a d i n g s were t a k e n a t e a c h i n c r e m e n t , The t e s t was d i s c o n t i n u e d a f t e r t h e l o a d had r e a c h e d a maximum.

R E S U L T S AN11 D I S C U S S I O N P a n e l s 1, 2 and

-

3

Close agreement was o b t a i n e d between t h e t e s t r e s u l t s f o r p a n e l s 1, 2 and 3 a s c a n be s e e n from t h e l o a d - d e f l e c t i o n c u r v e s of P i g . 11. (Load i s e x p r e s s e d i n t e r m s of t o t a l l o a d , a p p l i e d a t 1/3 p o i n t s of t h e v e r t i c a l span, p e r

f t l e n g t h of p a n e l ) . C r a c k i n g occurred a t a n a v e r a g e loc-

-

of

254

l b

p e r f i t l e n g t h and t h e accompanying deflections

a v e r a g e d 0.03 i n . I n s p e c t i o n of t h e c u r v e s shows t h a t t h e t e s t on p a n e l 2 s h o u l d have been c a r r i e d f u r t h e r f o r a b e t t e r a s s e s s m e n t of t h e a v e r a g e maximum l o a d between t h e t h r e e p a n e l s . The c u r v e s f o r a l l p a n e l s show t h a t a f t e r c r a c k i n g , d e f l e c t i o n s i n c r e a s e d r a p i d l y and a l t h o u g h t h e l o a d s c o n t i n u e d t o i n c r e a s e , t h e e r r a t i c n a t u r e of t h e c u r v e s i n d i c a t e t h a t t h e r e was a n i n t e r m i t t e n t y i e l d i n g of s t r u c t u r a l par-ts. The b e s t e s t i m a , t e of t h e a v e r a g e maximum l o a d a p p e a r s t o be a b o u t

Loadi.ng of pnncl

3

!:::n:; con:tinucd. un-l-il. c o l l . a p s e o c c u r r e d a t a v e r y 11.ar~;c d e f li?c:l;l.on

(8.93

i n . )

.

The p o r t i o n of t h e c u r v e beyond. maxi~nurn load is inf1.1zcnced par'~l:: b y t h e c h a r a c t e r i s t i c s o f t h e l o a d i n g system ~l!liich d i d n o t a p p l y a c o n s t a n t load. f o r a l l . def 3-ec-tion=: an6 is, t h e r e f ol-e, p e r h a p s n o t t o o s i g n i f i c a n t , I t shows t h o - t beyond t h e maximum l o a d e q u i l i b r i u m was p o s s i b l e u n d e r s u c c e s s i v e l y reduced l a t e r a l l o a d s u n t i l a l i m i t i n g d e f l e c t i o n w a s r e a c h e d . F i g u r e 1 2 shovrs v e r t i c a l c e n t r e l i n e p r o f i l e s a t sel-ec-ted l o a d s f o r p a n e l

3

and i s t y p i c a l a s w e l l of p a n e l s 1 and 2. The p r i n c i p a l s i g n i f i c a n c e of t h e s e c u r v e s i s t h e c o n f i r m a t i o n of t h e c r a c k i n g l o a d s t h a t were o t h e r w i s e observed v i s u a l l y . Immediately p r i o r t o craclcing, Lhe d e f l e c t i o n s a t p o i n t s 3 and

4

were e q u a l a s would be e x p e c t e d , and t h e niaximum d e f l e c t i o n was, t h e r e f o r e , a t t h e c e n t r e l i n e . A f t e r t h e a p p e a r a n c e of t h e c r a c k , however, t h e d e f l e c t i o n a t

4

became g r e a t e r t h a n a t

3

and tine tnnxim~~m d e f l e c t i o n s t h e r e a f t e r o c c u r r e d a t t h e c r a c k , I n e v e r y c a s e c r a c k i n g of t h e p a n e l s o c c u r r e d a t a j o i n t a t t h e mortar-bloclr i n t e r f a c e , i . c .

,

by bond f a i l u r e . Taking t h e w a l l w e i g h t

(70

p s f ) and t h e r e a c t i o n o f t h e r o o f on t h e t o p of t h e w a l l (155 l b p e r l i n f t ) i n t o a c c o u n t i n t h e c a l c u l a t i o n s , t h e a v e r a g e a p p a r e n t modulus of r u p t u r e

(f,) f o r a l l w s l l p a n e l s was found t o b e 31.7 p s i (Appendix A ) .

If t h i s v a l u e of f r had been known o r assumed i n advance, and

i f t h e s t r e n g t h o f t h e w a l l had been c a l c u l a t e d w i t h o u t

t a k i n g i n t o a c c o u n t t h e v e r t i c a l l o a d s , a v a l u e of 211 l b p e r

l i n

f t would have been o b t a i n e d a s compared t o 254 l b p e r l i n f t a s found i n t h e t e s t s . T h i s shovrs t h a t f o r a n a c c u r a t e a s s e s s m e n t of t h e s t r e n g t h of a wal-1, i t i s n o t s u - f f i c i e n t merely t o h o w t h e modulus o f r u p t u r e and t h e l a t e r a l l o a d s ; t h e v e r t i c a l l o a d s must a l s o be i n c l u d e d i n t h e c a l c u l a - t i o n s .

On t h e o t h e r hand, i f a p a n e l i s assumed t o have c r a c k s a t t h e same l o c a t i o n a s t h o s e which o c c u r r e d i n t h e t e s t s , t h e n t h e maximum l a t e r a l l o a d c a l c u l a t e d f o r c o n d i - t i o n s of s t a b i l i t y would be 169.5 l b p e r l i n f t (Appendix B ) . T h i s i s l e s s t h a n t h e c r a c k i n g s t r e n g t h o b t a i n e d e x p e r i m e n t a l l y ; f o r t h e l o n g term s t r e n g t h of a w a l l , t h e r e f o r e , one must

c o n s i d e r w h e t h e r o r n o t bond c a p a b l e of r e s i s t i n g t e n s i l e

s t r e s s e s c a n be e x p e c t e d t o p e r s i s t f o r t h e l i f e o f t h e b u i l d i n g -

o r w h e t h e r w e a t h e r i n g o r a c c i d e n t i s l i l t e l y t o c a u s e a c r a c k . In t h i s c o n c r e t e b l o c k b u i l d i n g t h e bond appeared. t o be good a f t e r 25 y e a r s l i f e .

S i n c e f o r t h e g i v e n v e r t i c a l . l o a d s on one of t h e t e s t p a n e l s , t h e l a t e r a l l o a d s c a u s i n g c r a c k i n g c a n b e shown t o be g r e a t e r t h a n t h e l a t e r a l s t a b i l i t y l o a d of a c r a c k e d p a n e l , c o l l a p s e of t h e p a n e l s s h o u l d have f o l l o w e d immediately

a f t e r cl-r~cli-in[;. Nevc?r-Lllcl (::-<:;, .i'lw:; con.L'in11c:ci to r e s i c - t

-,

i l l c r e a s e d l o a d s u p 'to a un:\:iirii\nn> :\ban i; :)O :pi::c ct;nL ~ ~ : c n t e r

%ban -the cracl.:ing l o a d o r ::it!ou t iloublc: -tllc ab nvc -men-6i oned

s t a b i l i t y l o a d . !Phis can o n l y bt.. i . t ~ c ~ ) u i ~ - t c c l :Cora b y -6hc: p r e s e n c e

o f e x t e r n a l f o r c e s n o t :prt?vic,.c:sl,y -i-nl:.ci-1 i'nt;o nccol.2ri.t i n t h e c a l c u l a t i o l i s

.

The o:nly a p p a r e n t s o u r c e o f s ~ . i c h a 120s s i b l e f o r c e i s t h a t t h e t o r s i o n a l r e s i s - t a c c e o f t h e r o o f , pla-be and

anclior bol-l; c o m b i n a t i o n exex-tcd a nci;::il,.1-ve movemeat at t h e

t o p of t h e w a l l . Tfhetlzcr o r .-lot t h e mornen-t ~:cr,ista.nc;e of %lie

c o r ~ n e c t i o n s i s a p r a c - L i c a l mn.ttcr o r r c ? . i a b l l ? enough -to be

t a k e n i n t o accoufi-t i n d e s i g n needs fur-tsh.cr study. I n p l a n n i n g

f u r t h e r t e s t s , however, t h e a p p a r a t u s t o b e u s e d must p r o v i d e f o r i t s e v a l u a t i o n t o a s s i s t i n t h e in-l;i:rpret-ation o f r e s u l t s .

P a n e l 4

A s ~~roulcl be e x p e c t e d , t h e crac!cing of vial1 p a n e l

4

began a t t h e f r e e end of t h e w a l l (.Fj.g, 8 ) and p r o g r e s s e d t o w a r d s t h e end su2porAted by t h e a b u t t i n g w a l l . I n t h i s c a s e c r a c k i n g o c c u r r e d i n t h e j o i n t below t h e f _{i : f t h c o u r s e , from}

.the t o p r a t h e r Cnan below t h e s.i;rtk a s i n p a n e l s 1, 2 and

3.

I n P i g . 1 3 t h e l o a d - ( 1 e : f l . e ~ - t i o n c u r v e s a r e ? l o t t e d f o r s e c t i o n s A , B , C and D l o c a t e d a t t h e f r e e end of t h e w a l l , t h e q u a r t e r p o i n t s and t h e c e n t r e 1-ine. The f i r s t c r a c k a p p e a r e d

at-

s e c t i o n A a t a l a t e r a l l o a d of 244 l b p e r f t o f w a l l a s i n d i c a t e d by

' x r

on t h e

curve.

T h i s i s o n l y s l i g h t l y l e s s t h a n t h e c r a c k i n g l o a d f o r t h e p r e v i o u s p a n e l s showing t h a t t h e d e f l e c t i o n a t t h i s s e c t i o n was p r a c - t i c a l l y u n a f f e c t e d by t h e a b u t t i n g w a l l a t t h e f a r end. S e c t i o n s

IJ,

C and D were p r o g r e s s i v e l y s t i f f e r , s i n c e t h e y were s ~ x c c e s s i v a l y n e a r e r t o t h e support;; when

c r a c k i n g o c c u r r e d a t A t h e d e f l e c t i o n a t D w a s a b o u t

25

p e r c e n t o f t h a t a t A .

A f t e r the f i r s t c r a c k i n g t h e c r a c k p r o g r e s s e d

t o w a r d s

D

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

cyc shown on t h e c u r v e s . F i n a l l y a t l o a d t z q t h e complete

c r a c k p a t t e r n s h o ~ ~ i n F i g . 8 was develo1)ed and t h e l o a d began t o d e c r e a s e . W ~ a n th e t e s t was d i s c o n t i n u e d t h e d e f l e c t i o n a t

U

vras a b o u t 80 p e r c e n t t h a t a t A.

The

g r a d u a l e q u a l i z a t i o n of d e f l e c t i o n s i s a l s o i l l u s t r a t e d by t h e h o r i z o n - t a l w a l l p r o f i l e s p l o t t e d i n P i g . 1 4 f o r s e l e c t e d l o a d s . If t h e e f f e c t of t h e a b u t t i n g c r o s s - w a l l were n o t c o n s i d e r e d , it l?~ould be e x p e c t e d t h a t p a n e l

4

would r e a c h a maximurn l o a d p e r f - t of

335

l b p e r l i n f t , ' t a k i n g t h e r e s u l t s of p a n e l s 1, 2 and 3 a s t h e c r i t e r i a ( a c t u a l l y a b o u t

5

p e r c e n t l e s s s i n c e p a n e l

4

w a s n o t r e n d e r e d on the i n s i d e ) . The a c t u a l a v e r a g e maximum l o a d f r o m -the. t e s t was 348 l b p e r l i n

The above o b s e r v a t i o n s indic:n tc t h a t a n ubu-1;-king

w a l l may i n f l u u n c c the r;tiffne:;:~ and c r a c ! r i . n ~ s t r c t n ~ ; t l ~ oS a w a l l over a h o r i z o n t a l d r i ~ ~ t a n c c a b o u t thrcc: t:i.rnes t h e vrall h e i g h t , b u t that; t h e n.laximurn s t r e n g t h is l i l c e l y t o b o l i t t l e a f f e c t e d except n e a r t h e cross-mil. I t a p p e a r s

from

this

t h a t t h e p r a c t i c a 1 maxlimum s p a c i n g s o f c r o s s - w a l l s o r a b ~ r t

-

ments w i l l depend on whether cracir-i~zg o r

maximum

lond i s assumed a s the c r i t e r i o n . CONCLUSION The t e s t s on t h e c o n c r e t e block b u i l d i n g a t A u l t s v i l l e i n d i c a t e t h a t t h e s t r e n g t h o f t h e v e r t i c a l s t r i p s of t h e w a l l s was g r e a t l y i n f l u e n c e d by t h r e e f a c t o r s : t h e s t r e n g t h of t h e mortar-block bond, t h e e f f e c t of t h e v e r t i c a l l o a d s and t h e moment r e s i s t a n c e of t h e c o m ~ e c t i o n s . If comprehensive f i e l d o r l a b o r a t o r y t e s t s a r e undertaken, t h e y should be planned t o e v a l u a t e t h e r e l a t i v e importance of t h e s e s o u r c e s of s t r e n g t h o v e r a wide range of p r a c t i c a l cases. C o n s i d e r a t i o n should a l s o be given

t o

determine t h e probable r e l i a b i l i t y of bond over l o n g p e r i o d s .

The t e s t s a l s o i n d i c a t e t h a t c r o s s - w a l l s o r a b u t - ments may n o t g r e a t l y i n c r e a s e t h e maximum s t r e n g t h of some w a l l s , b u t t h e i r i n f l u e n c e on t h e c r a c k i n g s t r e n g t h may be g r e a t e r .

While t h e r e s u l t s of t h i s i n v e s t i g a t i o n may n o t appear unexpected, t h e y a r c a r e a s o n a b l y c l e a r s t a r t i n g p o i n t f o r t h e D i v i s i o n s ' f u t u r e i n v e s t i g a t i o n s i n t o t h e l a t e r a l

s t r e n g t h

of.

masonry w a l l s , a s u b j e c t on which more i n f o r m a t i o n i s needed d e s p i t e t h e l o n g use of t h i s type of c o n s t r u c t i o n .

e

_P

_{Cheese factory,}

_.Aul%svflHe,

_{O n t a f i o ,}

[Wall

chosen

_for

_{t e s t s with panel} iguggabers

shorn

1

R A F T E R S 2 " X 5 % " SHEET l R Q N R O O F I N G ₉

\AT

_2'-0"

_{C - c}

1"

"

_%8

6

SHEATHING BOLT A T

7"-6

FIGURE

₂

TYPICAL C R O S S - S E C T I O N

0

_TEST

_{W A L L}

e

3

_{Test panels 1, 2 and}

_{3 after}

W A L L PANELS 1-3 PANEL I X s 8 . 6 3 ' P I N E L 2 Y ~ 5 . 3 4 ' PANEL 3 X = 9.34' 26 B 2 ( b ) WALL PANEL 4 E X T E R I O R V I E W 9 -e=S-s s --

___----

- - - = = = --- - -. ... -- - .... .- - . . . .. ... ..- . ... R E A C T I O N WALL--- - ..

2" BIB R O D - IOO TOM JAG#

... . . . - . . =*>:: ...: : STEEL MEMBER S T E E L STOOL ( e l C R O S S - SECTION FIGURE 5

Figure

6

_{VTaBl ps.ne1}

₁

_{showing loading and}

e

'7

_{WaPI panel 4 shewing l o a d i n g and}

e

9

_{D i a l gauges}

_{on inside}

_face

_of

_a

t = 8 . 5 "

p

- -- .i. ;F-- -.

I

WALL

= A V G ROOF LOAD PER

LIN. F T OF PANEL

B E F O R E C R A C K I N G

FIGURE 15

A F T E R CRACKING

lidall 'Panel..; 1, 2 and

3

-

Cal-culations a t Crac!ring Load

Cracking of t h e wal.1 panels occurred a t small d e f l e c t i o n s o f about 0.0Y i n . For s t r e s s c a l c u l a t i o n s t h e geomctry of t h e w a l l and t h e l o a d i n e systcin p r i o r t o c r a c k i n g may be considered u n c h a n ~ c d exccpt f o r t h e l o c a t i o n of t h e v e r t i c a l l o a d s and r e a c t i o n s a t t h e t o p and bottom of t h e panels.

Rotation of t h e t o p of t h e w a l l w i l l cause t h e roof r e a c t i o n t o move from i t s t h e o r e t i c a l o r i g i n 8 1 p o s i t i o n

'x'

(Fig.

1 5 ( a ) )

a t t h e c e n t r e of t h e p l a t e towards t h e i n n e r edge of t h e p l a t e a t Idis e i a c t p o s i t i o n i s n o t knovm b u t t h e e r r o r w i l l be small i f f o r t h e purposes of t h e s e c a l c u l a t i o n s

it

i s assumed t o have moved t o t h e c e n t r e of g r a v i t y of t h e -mil a t ' y r

.

Notation:

w = t h e r e a c t i o n of t h e roof on t h e t o p of t h e panel 1

w = t h e weight of t h e panel above t h e s e c t i o n considered

2 A = t h e n e t a r e a of t h e h o r i z o n t a l c r o s s - s e c t i o n of t h e panel c = d i s t a n c e t o t h e o u t e r f i b r e of t h e panel from i t s c e n t r e of g r a v i t y I

=

t h e moment of i n e r t i a of t h e n e t c r o s s - s e c t i o n a l a r e a of a panel M = t h e moment ac-Ling on a h o r i z o n t a l c r o s s - s e c t i o n of t h e panel

P

= t h e t o t a l load a p p l i e d t o t h e panel a t 1/3 p o i n t s Other symbols a r e defined i n Pig.

1 5 .

Assuming no bond between t h e base of t h e w a l l and t h e foundation, t h e t e n s i l e s t r e s s ( f ) a t any c r o s s - s e c t i o n

t

may be expressed by

Plaximurn t e n s i l e s t r e s s w i l l occur where t l ~ t ? maximum moment i s combined w i t h t h e l e a s t v e r t i c a l l o a d , i.e. a t -the upper loading p o i n t . I n t h e Les-ts, c;:acl.cing o c c u r r e d a t t h e f i r s t mortar j o i n t below t h e upper l o a d , i . e . at E.

and

The average r e a c t i o n VJ of t h e roof on t h e w a l l p a n e l s was c a l c u l a t e d t o b e 155 i b p e r l i n f t o f panel. The weight of t h e wall. was found by mcc7s1lre1nen-t t o b e 70 l b p e r

sq f t i n c l u d i n g

$I

i n . o f renderin[; on the i n s i d e f a c e . Hence

-

b

x

70 =

19-22.

70 = 287 l b p e r l i n f t

W2

-

12

of panel. The average c r a c k i n g l o a d f o r the p a n e l s was 254 l b p e r l i n f t . A t c r a c k i n g , f t became e q u a l t o t h e modulus of r u p t u r e f r and

-

( 1 5 5

+ 2 8 7 ) 2 5 1 ~ 1 2 3 . 7 5 4.14

fr---.-

TO.

1 +--

~

~

5

7

0

= 31.7 p s i .

Assuming t h a t t h e v a l u e of f r viere lmo-m i n advance and t h a t t h e v e r t i c a l l o a d s were n e g l e c t e d , t h e n on t h e b a s i s of bending s t r e n g t h o n l y t h e l o a d r e q u i r e d t o c r a c k t h e w a l l would be c a l c u l a t e d a s f o l l o w s : 6 f r

1

P

= _hc -

-

-

31*7

570

= 211 i b p e r l i n f t 12:r-r5

x

4 . 1 T

The e s t i m a t e , t h e r e f o r e , wou1.d have been a b o u t 1 7 p e r c e n t t o o low.

Wall T3an.els 1, 2 and

3

- C a l c u l a t i o n s l i e p r d i n ; : S-1;abili:ty A f t e r Cra tzl<inyL

-

----

A f t e r a w a l l p a n e l h a s c r a c k e d , I u r 3 ) c r r o t a t i o n of t h e upper and 1owr:r se,.;mc:uCs w i l l t-alcc plnc:: immediately. V e r t i c a l r e a c t i o n s w and Vi3 w i l l s h i f - t t o their extreme

1

p o s i t i o n s a t ' 0 1 and B ( P i g . 1 5 ( b ) ) and w i l l be c o n c e n t r a t e d

o v e r a s m a l l enough a r e a t o b e cons-idercd a s a c t i n g a l o n g a l i n e o r a hinge.

A

"hinp;..;ct' w i l l a l s o o c c u r a t 1:.

O v e r t u r n i n g of t h e two segrnents should o c c u r

immediately f o l l o w i n g c r a c l i i n g , u n l e s s -the s h i f t s of wl and

VB

a r c s u f f i c i e n t t o r e s t o r e t h e e q u i l i b r i u m I-ost by t h e d i s - appearance of t h e mornen-l; of r e s i s t a n c e a t s e c t i o n E o r u n l e s s o t h e r f o r c e s come i n t o p l a y .

For p a n e l s 1, 2 and 3, t h e l a t e r a l l o a d t h a t would cause c o l l a p s e of a cracked w a l l m a y b e c a l c u l a t e d a s f o l l o w s :

S i m i l a r l y , t a k i n g t h e f r e e body of t h e u p p e r segment of t h e w a l l p a n e l ,

2

( a )

+

w2

S o l v i n g (1) and ( 2 )

p = 169.5 Ib p e r l i n f t of

ane el.

T h i s l o a d i s l e s s t h a n t h e l o a d causing c r a c k i n g of t h e p a n e l s , and on t h i s b a s i s c o l l a p s e should have occurred immediately f o l l o w i n g c r a c k i n g . Since t h e p a n e l s d i d n o t

f a i l , an e x p l a n a t i o n can be made o n l y on t h e b a s i s o f a n a d d i t i o n a l f o r c e o r moment t h a t w a s n o t t a k e n i n t o a c c o u n t i n t h e bond c a l c u l a t i o n s .

I n

t l l e s e t e s t s t h e t o r s i o n a l r e s i s t a n c e of t h e t o p p l a t e , t h e a n c h o r b o l t s and t h e roof must have a p p l i e d a n e g a t i v e r e s i s t i n g moment a t t h e t o p of t h e panel.