Restraint and temperature studies on wall of cinder concrete blocks exposed to fire

Publisher’s version / Version de l'éditeur:

Vous avez des questions? Nous pouvons vous aider. Pour communiquer directement avec un auteur, consultez la

première page de la revue dans laquelle son article a été publié afin de trouver ses coordonnées. Si vous n’arrivez pas à les repérer, communiquez avec nous à PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca.

Questions? Contact the NRC Publications Archive team at

PublicationsArchive-ArchivesPublications@nrc-cnrc.gc.ca. If you wish to email the authors directly, please see the first page of the publication for their contact information.

https://publications-cnrc.canada.ca/fra/droits

L’accès à ce site Web et l’utilisation de son contenu sont assujettis aux conditions présentées dans le site LISEZ CES CONDITIONS ATTENTIVEMENT AVANT D’UTILISER CE SITE WEB.

Internal Report (National Research Council of Canada. Division of Building Research), 1959-12-01

READ THESE TERMS AND CONDITIONS CAREFULLY BEFORE USING THIS WEBSITE.

https://nrc-publications.canada.ca/eng/copyright

NRC Publications Archive Record / Notice des Archives des publications du CNRC :

https://nrc-publications.canada.ca/eng/view/object/?id=02fb638f-26cb-4760-90a2-f12d1924b0dc https://publications-cnrc.canada.ca/fra/voir/objet/?id=02fb638f-26cb-4760-90a2-f12d1924b0dc

NRC Publications Archive

Archives des publications du CNRC

For the publisher’s version, please access the DOI link below./ Pour consulter la version de l’éditeur, utilisez le lien DOI ci-dessous.

https://doi.org/10.4224/20338161

Access and use of this website and the material on it are subject to the Terms and Conditions set forth at

Restraint and temperature studies on wall of cinder concrete blocks exposed to fire

NATIONAL RESEARCH COUNCIL CANADA

D I V I S I O N O F B U I L D I N G RF;SEARCH

R E S T R A I N T

AND

TEMIPERIITURE S T U D I E S 011 _WALL

O F CImDER CONCRETE BLOCKS EXPOSED T O FIRE

R e p o r t N o . 180

of t h e

Division of B u i l d i n g Research

OTTAWA

PREFACE

A cinder block wall constructed to provide a closure for the wall furnace during its initial trials was specially instrumented and used in a special final run. Th.is wall

was

not suitable for a fire-resistance test because of the many times it had been heated

during trial

runs

of the furnace, but it could still be used to provide other infornlation, as described in this report. The author, a mechanical engineer, is a research officer

with

the E r e Research Section of the Division and is speciall-y concerned with fire resistance studies,

Ottawa

December 1959

N,B,

Hutcheon Assistant Director

RESTRAINT AND T~1FERATU.W STUDIElS ON WALL

OF CINDER CONCRETE BLOCKS

EXPOSED

TO FIRE

T.Z. Harmathy

During t h e comrnissioning 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 D i v i s i o n of Building Research, two masonry wa1.1~ were con;.tructed f o r c l o s i n g t h e wall f ~ n m a c e . Following a t r i a l p e r i o d it was decided t o u t i l i z e them t o provide information 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 s i n s k i l l i n overcoming problems met d u r i n g a w a l l t e s t ,

( b ) s t u d y 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 ) ctudy d i f f e r e n t methods f o r 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 c i n d e r block w a l l on March 24, 1953.

DESCRIPTION OF TEE SPECI?~lEll

Cinder _{concrete blocks 16 by} 8 _{by 8 inches were used t o}

b u i l d an u n p l a s t e r e d wall 8 inches t h i c k , 1 3 f e e t - 6 i n c h e s wide, and 12 f e e t - 4 inches hir&.

It ha(: bcben used s e v e r a l times f o r c l o s i n g t h e wall furnace d u r i n g I n m a c e performance t e s t s ; and although t h e s e t e s t s had never l a s t e d more t h a n 1/2 hour, t h e fire-exposed s u r f a c e of t h e wall was d i s c o l o u r e d , t h e mortar was cracked i n

some p l a c e s and could be rubbed o f f . I t s low moisture content; (1.93 p e r c e n t x..fcrred t o oven-dry weight) lvas probably a l s o t h e r e s u l t o f I l l - . plevious t e s t s ,

TESTING PROCEDURE

TLe t e s t was i n t e n d e d t o be c a r r i e d o u t i n accordance with ASTM "pe . i f i c a t i o n E-119. Furnace temperature was measured by n i n e t h ~ r m o ~ o u p l e s enclosed i n s t e e l p i p e ( t h e l o c a t i o n of t h e t h e r m o c o u p l e i s shown i n Fig. 1) and was c o n t r o l l e d s o t h a t t h e average of t h e n i n e r e a d i n g s followed 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 m e l a t i o n .

The unexposed s u r f a c e temperature was measured by 1 0 thermocouples, f i v e symmetrically d i s p o s e d a s 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. These were 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 square and 0.4 i n c h t h i c k . The o t h e r f i v e thermocouples were placed under pads recommended a s s u b s t i t u t e s In t h e t'lJinutes of Meeting of Committee E-5 on F i r e T e s t of I ~ l a t e r i a l s and C o n s t r u c t i o n s " (ASTM), 1 2 February 1958.

A s mentioned, o t h e r methods of measuring t h e unexposed s u r f a c e temperature were s t u d i e d :

( i ) t h e s t a n d a r d method of BS S p e c i f i c a t i o n 476

( i i ) a method shown i n Mg. 2a ( c a l l e d h e r e a f t e r FYTethod 11)

(,iii) a method shown i n Pig. 2b (call-ed h e r e a f t e r Method B )

.

The l o c a t i o n of t h e d i f f e r e n t thermocoup,-es on t h e un-

exposed slxcfncs i s shovrn i n Fig. 4.

Although i n p r a c t i c e t h i s t y p e of w a l l i s g e n e r a l l y used a s a l o a d - b e a r t n g element, tlie t e s t was c a r r i e d o u t a c c o r d i n g t o

t h e requirements 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 l 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 t h e t e s t .

The specimen was r e s t r a i n e d on a l l f o u r edges through h y d r a u l i c jacks, u s i n g a n i n s t r u n l e n t , sholvn i n P i e .

3 ,

which had been designed t o i n d i c a t e t h e v a r i a t i o n of t h e width of t h e w a 1 . l . When t h e l i g h t beam was d e f l e c t e d from t h e p o i n t corresponding t o z e r o wall expansion on s c a l e 1 2 , t h e p r e s s u r e on t h e jacks was manuall-y a d j u s t e d t o e l i m i n a t e t h e d e f l e c t i o n .

P u r e l y f o r r e s e a r c h purposes t h e d e f l e c t i o n a t t h e c e n t r e of t h e wall was measured manually a t 10- t o _{15-minute i n t e r v a l s . .}

Since t h e f i r e endurance of t h e w a l l was n o t of primary i n t e r e s t , t h e t e s t was c a r r i e d on a f t e r t h e unexposed t e m p e r a t u r e had exceeded t h e l i m i t i n g v a l u e d e f i n e d i n t h e ASTM S p e c i f i c a t i o n E-119. A f t e r a 2-hour t e s t t h e f u r n a c e was opened and a 2-minute hose t e s t was c a r r i e d o u t . The w a t e r p r e s s u r e a t t h e b a s e of t h e n o z z l e was 30 pounds p e r s q u a r e i n c h gauge.

RESULTS

--

The r e a d i n g s t a k e n from t h e n i n e f u r n a c e - s i d e thermo- c o u p l e s , as w e l l a s t h e a v e r a g e of t h e n i n e i n d i v i d u a l r e a d i n g s , a r e p l o t t e d i n Fig. 1. It has been e s t a b l i s h e d t h a t t h e f u r n a c e -temperature c o n t r o l l e r had n o t been s t a n d a r d i z e d p r i o r t o t h e t e s t , s o t h a t t h e a v e r a g e f u r n a c e t e m p e r a t u r e w a s k e p t 1 5 0 t o 200°F below t h e v a l i ~ e s p r e s c r i b e d by t h e AS!lBI S p e c i f i c a t i o n E-119. Consequently, t h e t e s t cannot be r e g a r d e d a s s t a n d a r d .

F i g u r e 4 shows t h e v a r i a t i o n of t h e r e a d i n g s on t h e ther;nocouples l o c a t e d a t d i f f e r e n t p o i n t s of t h e unexposed s u r f a c e and a r r a n g e d a c c o r d i n g t o a n y of t h e above-mentioned methods. It may be s e e n t h a t a t some p l a c e s s u r f a c e p o i n t s f a i r l y c l o s e t o one a n o t h e r a t t a i n e d markedly d i f f e r e n t t e m p e r a t u r e s , i n s p i t e of t h e f a c t t h a t t h e y were measured by s i m i l a r methods. These d i f f e r e n c e s were p r o b a b l y t h e r e s u l t of a n impinging flame o r a w a l l c a v i t y o p p o s i t e some of t h e p o i n t s . Owing t o l o c a l v a r i a t i o n s , t h e t e m p e r a t u r e s measured by t h e v a r i o u s methods do n o t always confornl t o e x p e c t a t i o n . Since i n such c i r c u m s t a n c e s t h e comparison of 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 i s n o t l o g i c a l , t h e v a r i a t i o n of t h e a v e r a g e unexposed s u r f a c e t e m p e r a t u r e , as measured by t h e d i f f e r e n t methods, i s a l s o p l o t t e d ( F i g . 5 ) . The v a r i a t i o n of t h e r e s t r a i n i n g p r e s s u r e ( l b p e r s q i n . of t h e c r o s s - s e c t i o n a l a r e a of w a l l ) and t h e d e f l e c t i o n a t t h e c e n t r e of t h e w a l l d u r i n g t h e t e s t a r e a l s o p l o t t e d ( s e e Pig. 6 ) .

According t o t h e ASTIVI method of tempera-Lure measurement t h e a v e r a g e t e m p e r a t u r e of t h e unexposed s u r f a c e reached t h e a l l o w a b l e l i m i t

(74

+

_{250 = 324OF) i n 1 h o u r 4 1 minutes.}

Both t h e exposed and 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 , and no s e r i o u s c r a c k s o r o t h e r damages were n o t i c e d . Small m o r t a r and 1- t o 3-inch c o n c r e t e fragments were washed dovin from t h e exposed s u r f a c e d u r i n g t h e hose s t r e a m t e s t .

On t h e day f o l l o w i n g , a permanent s h r i n k a g e of 0.18 i n c h of t h e w a l l w i d t h w a s measured.

DISCUSSION

F r - n Fig, 1 it may be seen t h a t t h e t h e m o c o u p l e s i n t n e upper ow i n s i d e t h e f u r n a c e gave temperature r e a d i n g s throughou-t t l e whole t e s t milch h i g h e r t h a n t h o s e i n t h e bottom row. The d i f f e r e n c e i s more t h a n might be expected f o r t h e case when equ. I h e a t i s suppl-ied through each b u r n e r , and it

has t h e r e f o r e been concluded t h a t t h e a s b e s t o s s e a l i n g was n o t s a t i s f a c t o r y a-t t h e bottom of t h e furnace.

A s a r e s u l t of uneven temperature d i s t r i b u t i o n i n s i d e t h e fm-nace t h e wiexposed s u r f a c e temperature a l s o v a r i e d

s

.

g n i f i 4 a n t l y 'ram bo-ttom t o top. A t t h e time of f a i l u r e t h e d i f f e r e n c e between t h e upper and lower p o r t i o n s was a s high a s 150°P. 1Th'~ts, lt may be seen t h a t if l a r g e temperature d i f f e r e n c e s a r e t o l e r a t e d l n s i d e t h e f u r n a c e , e a r l y f a i l - w e of t h e specimen by l o c a l temperature r i s e on t h e unexposed s u r f a c e can be

expected. I n o r d e r .to prevent such e a r l y f a i l u r e s , it i s sug- geoted t h a t i n t h e c a s e of s t a n d a r d f i r e t e s t s , l i m i t a t i o n be

imposed on t h e maximum l o c a l d e v i a t i o n from t h e average f u r n a c e t e m r e r a t u r e ,

Figure 5 shows t h a t -the temperatuxes y i e l d e d by Methods A and B a r e betw.-en t h o s e obtained by t h e American and B r i t i s h

metlods. It should be emphasized, hovrever, that owing t o t h e

s i g n i f i c a n t l o a 1 temperatlxre d i f f e r e n c e s superimposed on a

s t . a d y temperature i n c r e a s e from t h e bottom t o t h e t o p t h e g e n e r a l v a l i d i t j of t h i s o b s e r v a t i o n i s v e r y questionable.

The r e s u l t s j u s t i f y t h e assumption t h a t t h e load due t o r e s t r a i n t i n t h e c a s e of non-bearing w a l l s may be much h i g h e r t h a n t h e load imposed on load-bearing elements. A f i r e endurance period obtained f o r a load-bearin6 w a l l , t h e r e f o r e , cannot a u t o - m a t i c a l l y be app i e d t o t h e same w a l l i f it i s used a s a non- b e a r i n g element,

METHOD A

METHOD B

th

=

_THERMOCOUPLE

WIRES

W

=

WALL

c =

CEMENT

FIGURE

₂

z

Or:

a

a

Z

-

Or:

e

U)

I

₂

TIME (HR)

5 0 0

4 5 0

-..-

STANDARD AMERICAN METHOD 4 00

---

AMERICAN SUBSTITUTE METHOD

AMERiCAN METHOD (AVERAGE)

-.-.-

. . .

-

SUGGESTED METHOD A SUGGESTED METHOD B

. . -

SUGGESTED METHOD (AVERAGE) 3 5 0

--

BRITISH METHOD 300 2 5 0 200 1 5 0 100 5 0 i

I

1 0 30 60 90 128 TIME (MINI

FIGURE

5

+ _COMPRESSIVE UI

0 0

TOWARD THE 0