Restraint and temperature studies on wall of clay brick exposed to fire

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Restraint and temperature studies on wall of clay brick exposed to fire

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PREFACE

The l a r g e f i r e r e s i s t a n c e f u r n a c e s i n t h e F i r e Research Labora%ory of t h e D i v i s i o n a r e

intended p r i m a r i l y f o r r e s e a r c h though t h e y may a l s o be used i n t h e t e s t i n g of p r o p r i e t a r y con- s t r u c t i o n s . Since t h e s e a r e l a r g e f a c i l i t i e s r e q u i r i n g l a r g e and c o s t l y specimens it w i l l

always be t h e aim of t h e Division t o o b t a i n and t o make a v a i l a b l e a s much information a s p o s s i b l e from each specimen c o n s t r u c t e d . The second of two w a l l s c o n s t r u c t e d f o r use d u r i n g t h e i n i t i a l

t r i a l s o f t h e w a l l furnace has now been r e - t e s t e d t o provide supplementary i n f o r m a t i o n on tempera- t u r e measurement and on panel r e s t r a i n t which i s now r e p o r t e d . The a u t h o r , a mechanical e n g i n e e r and a r e s e a r c h o f f i c e r with t h e F i r e Section of t h e D i v i s i o n , i s r e s p o n s i b l e f o r t h e work being done on f i r e r e s i s t a n c e . .

M.B. Hutcheon A s s i s t a n t D i r e c t o r

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RESTRAINT AND TENZ'ERATURE STTIDIES ON

WALL OF CLAY B R I C K EXPOSED _{TO FIRE}

T.Z. Harmathy

During t h e commissioning period f o r t h e f i r e r e s i s t a n c e f u r n a c e s i n s t a l l e d i n t h e new F i r e Research Laboratory of t h e Division of B u i l d i n g Research, two masonry w a l l s were c o n s t n ~ c t e d f o r c l o s i n g t h e w a l l

furnace. Following a t r i a l period it was decided t o u t i l i z e them t o provide i n f o r m a t i o n which would be b e n e f i c i a l i n t h e f u t u . r e t e s t i n g and r e s e a r c h program of t h e F i r e Section.

I t was t h e purpose of t h e s e t e s t s t o :

( a ) g a i n experience i n . overcoming problems met d u r i n g a w a l l t e s t ,

( b ) study t h e deformation and t h e r e s t r a i n i n g f o r c e s i n t h e w a l l when exposed t o f i r e ,

( c ) stu.dy d i f f e r e n t methods of measuring t h e unexposed s u r f a c e temperature.

This r e p o r t d e s c r i b e s a t e s t conducted on a

b r i c k w a l l on May

5 ,

1959. DESCRIPTION OF

----

THE SPECIIJEN

Clay b r i c k s 2h by 32 by 8 i n c h e s were used t o b u i l d a n u n p l a s t e r e d w a l l 8 i n c h e s t h i c k , 1 3 f e e t - 5 & inches

wide, and 1 2 f e e t - 5 i n c h e s high.

A few weeks b e f o r e t e s t i n g , t h e w a l l had been used f o r c l o s i n g t h e wal.1 f u r n a c e d u r i n g a performance t e s t o f about 1 h o u r ' s d u r a t i o n . 11s a r e s u l t , t h e f i r e - exposed s i d e of t h e wal.1, was s l i g h t l y discoloured. and s e v e r a l f i n e c r a c k s i n th.e brick-work could be d e t e c t e d . The mortar a l s o was damaged, f o r t h e s u r f a c e l a y e r could e a s i l y be rubbed o f f . l l o i s t u r e con-tent of t h e b r i c k was n o t measured, b u t it must have been very low because of t h e previous t e s t .

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TESTING PROCEDURE

t h e t e s t w a s c a r r i e d o u t in accordance w i t h ASTM S p e c i f i c a t i o n E-119. Furnace t e m p e r a t u r e w a s measured by n i n e s y m m e t r i c a l l y d i s p o s e d thermocouples, s i x of which were e n c l o s e d i n s e a l e d $-inch p i p e s of standard-weight

b l a c k wrought s t e e l , as p r e s c r i b e d by t h e t e s t s p e c i f i c a t i o n . The o t h e r t h r e e were p l a c e d i n 13/16-inch OD I n c o n e l

t u b e s of 0.035-inch w a l l t h i c k n e s s , equipped w i t h wrought s t e e l c a p s a t t h e end. Both t h e i n d i v i d u a l t e m p e r a t u r e s a t n i n e p o i n t s and t h e a v e r a g e of t h e n i n e r e a d i n g s were recorded. The f u r n a c e t e m p e r a t u r e was c o n t r o l l e d s o t h a t t h e a v e r a g e t e m p e r a t u r e f o l l o w e d t h e p r e s c r i b e d t e m p e r a t u r e - time c o r r e l a t i o n .

The un.exposed s u r f a c e t e m p e r a t u r e was measured by 1 0 thermocouples, f i v e covered w i t h s t a n d a r d a s b e s t o s pads

6 i n c h e s s q u a r e and 0.4 i n c h t h i c k , s y m m e t r i c a l l y

d i s p o s e d as r e q u i r e d by t h e ASTM S p e c i f i c a t i o n E-119. The

o t h e r f i v e were p l a c e d under pads recommended a s s u b s t i t u t e a i n t h e "Minutes of Meeting of Committee E-5'on F i r e T e s t o f M a t e r i a l s a n d C o n s t r u c t i o n s " (ASiCM), P e b r u a r ~ ~ 1 2 , 1958.

Other methods o f measuring t h e unexposed s u r f a c e t e m p e r a t u r e were a l s o s t u d i e d :

( i ) t h e s t a n d a r d method o f BS S p e c i f i c a t i o n

4769

(ii) a method shown i n Hg. 1.

Illhe l o c a t i o n o f t h e d i f f e r e n t thermocouples on t h e unexposed s u r f a c e i s shown

i n

Fig. 2.

P r i o r t o t h e t e s t s p e c i a l c a r e had been t a k e n t o s e a l t h e g a p s between t h e f u r n a c e a n d t h e w a l l specimen and t o a d j u s t t h e f u e l f l o w a t each b u r n e r i n o r d e r t o o b t a i n a f a i r l y uniform t e m p e r a t u r e i n s i d e t h e f u r n a c e . Although t h i s t y p e o f w a l l i s g e n e r a l l y u s e d as

a

l o a d - b e a r i n g element, it w a s t h e i n t e n t i o n t o t e s t t h e w a l l a c c o r d i n g t o t h e r e q u i r e m e n t s p r e s c r i b e d f o r non-bearing w a l l s i n o r d e r t o s t u d y t h e v a r i a t i o n of t h e r e s t r a i n i n g f o r c e s d u r i n g the t e s t . A method p r e v i o u s l y r e p o r t e d

( 1 ) was i n t e n d e d t o be u s e d t o r e s t r a i n t h e specimen; however,

10 m i n u t e s a f t e r s t a r t i n g t h e t e s t t h e c a p a c i t y r e q u i r e d f o r f u l l r e s t r a i n t exceeded t h a t of t h e h y d r a u l i c l o a d i n g system. From t h i s t i m e on t h e l o a d remained c o n s t a n t a t

a b o u t 180 t o 190 pounds p e r s q u a r e i n c h o f w a l l c r o s s - s e c t i o n a l a r e a , b o t h i n v e r t i c a l and h o r i z o n t a l d i r e c t i o n , a n d t h e h o r i z o n t a l expansion of t h e w a l l w a s r e c o r d e d u s i n g t h e d e v i c e shown i n Pig.

3

of Ref. 1.

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The l a t e r a l d e f l e c t i o n of t h e w a l l was a l s o measured a t t h r e e p o i n t s h a l f way between t h e t o p and bottom: a t

t h e c e n t r e and a t t h e t w o edges. These measurements were t a k e n a t

5-

t o 10-minute i n t e r v a l s .

Immediately a f t e r t h e specimen f a i l e d t h e f u r n a c e

w a s opened and t h e f i r e - e x p o s e d s i d e of t h e w a l l was sub- j e c t e d t o a hose s t r e a m t e s t . T h i s t e s t d i d n o t conform t o t h e AS!t%I s p e c i f i c a t i o n a s t h e w a t e r p r e s s u r e w a s o n l y 30 pounds p e r s q u a r e i n c h gauge and t h e d u r a t i o n of a p p l i - c a t i o n w a s f o r 2$ minutes i n s t e a d of f o r

5

minutes,

RESULTS

Uniformity of f u r n a c e temperature was very good throughout t h e t e s t . A f t e r 1 0 minutes t h e maximum d e v i a - t i o n from t h e a v e r a g e was always l e s s t h a n 100°F. A p l o t of t h e average f u r n a c e t e m p e r a t u r e a g a i n s t time i s shown i n Fig. 3. Readings from t h e thermocouples e n c l o s e d in. I n c o n e l t u b e s followed t h e same t r e n d .

The v a r i a t i o n of t h e t e m p e r a t u r e of t h e unexposed s u r f a c e of t h e speoimen was a l s o uniform. Those t h e m o - c o u p l e s which r e p r e s e n t e d i d e n t i c a l methods gave v e r y n e a r l y i d e n t i c a l t e m p e r a t u r e s , t h e maximum d i f f e r e n c e always b e i n g l e s s t h a n 20°P. The s u b s t i t u t e ASTM method y i e l d e d n o t i c e a b l y lower r e a d i n g s t h a n t h e s t a n d a r d ASTM method. The a v e r a g e d i f f e r e n c e i n c r e a s e d s t e a d i l y and toward t h e end of t h e t e s t i t w a s 2g0E', The BS method

gave much lower r e a d i n g s t h a n t h e ASTM methods. O n t h e o t h e r hand, no s i g n i f i c a n t d i f f e r e n c e w a s found between t h e t e m p e r a t u r e s o b t a i n e d a c c o r d i n g t o t h e B r i t i s h method and t h e method shown i n Fig. 1.

V a r i a t i o n of t h e unexposed s u r f a c e temperature i s a l s o p l o t t e d i n F i g , 3 . _The _{curve r e p r e s e n t i n g t h e}_ASTM

method shows t h e a v e r a g e of t h e s t a n d a r d and s u b s t i t u t e measurements.

I n Pig.

4

l a t e r a l d e f l e c t i o n and n e t change i n

width o f t h e w a l l a r e shown. C o n t r a c t i o n of t h e w i d t h caused by a p p l i e d l o a d w a s measured on t h e day f o l l o w i n g t h e t e s t . When p l o t t i n g F i g . 4 t h i s v a l u e w a s added t o t h e r e c o r d e d v a l u e s of t h e w a l l expansion, so t h a t curve A a c t u a l l y r e p r e s e n t s t h e n e t change i n width i n c a s e of a f r e e l y expanding w a l l . The e f f e c t of t h e a p p l i e d l o a d on t h e l a t e r a l d e f l e c t i o n was found t o be n e g l i g i b l e ; t h e r e f o r e c u r v e s B1,

Br,

Bc and B can a l s o be r e g a r d e d as approximately r e p r e s e n t a t i v e of t h e deformation w i t h no imposed l o a d .

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According t o t h e ASm method of temperature measurement t h e average temperature of t h e unexposed

s u r f a c e reached t h e l i m i t i n g v a l u e (75

+

250 = 325OP) i n 4 h o u r s and 47 minutes.

Both t h e exposed and t h e unexposed s u r f a c e s of t h e w a l l were f r e q u e n t l y i n s p e c t e d d u r i n g t h e t e s t ; s e r i o u s

c r a c k s o r o t h e r damage were n o t i c e d . & r i n g t h e hose

stream t e s t t h e m o r t a r mas washed away t o a n average depth of

15

i n c h e s and p i e c e s of b r i c k were s e p a r a t e d from t h e exposed s u r f a c e .

DISCUSSION

The thermocouples enclosed i n t h e Inconel t u b e s y i e l d e d temperature r e a d i n g s p r a c t i c a l l y i d e n t i c a l t o t h o s e g i v e n by t h e thermocouples i n t h e s t a n d a r d wrought s t e e l pipes. However, from t h e p o i n t of view of r e s i s t a n c e t o c o r r o s i o n and sagging a t high t e m p e r a t u r e s t h e Inconel t u b e s a r e much s u p e r i o r . T h e i r u s e f o r thermocouple p r o t e c t i o n i s , t h e r e f o r e , recommended.

Since t h e temperatures o b t a i n e d from t h e unexposed s u r f a c e a c c o r d i n g t o t h e BS method were almost i d e n t i c a l t o t h o s e measured as shown i n Pig. 1, i t can be concluded

t h a t t h e B r i t i s h method g i v e s v e r y n e a r l y t h e t r u e s u r f a c e temperature. The e x p l a n a t i o n i s t h a t t h e temperature

drop caused by conduction through t h e thermocouple w i r e s

i s a l m o s t completely compensated by t h e temperature r i s e due t o the low e m i s s i v i t y o f t h e copper d i s k .

The r e s i s t a n c e t o h e a t flow of t h e s u b s t i t u t e ASTh4 pads proved somewhat lower t h a n t h a t o f t h e s t a n d a r d ASTM peds.

Restraint and temperature studies on wall of clay brick exposed to fire

NRC Publications Archive

Archives des publications du CNRC

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