Fire test of a 'tri-seal' floor and ceiling assembly

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Fire test of a 'tri-seal' floor and ceiling assembly Harmathy, T. Z.

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NATIONAL RESEARCH COUNCIL 'CANADA

D I V I S I O N OF BUILDING RESEARCH

PIRE TEST OF A "TRI-SEAL" FLOOR AND CEILING ASSEMBLY

F i r e Study N o .

5

o f the

D i v i s i o n o f B u i l d i n g R e s e a r c h

OTTAWA

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PREFACE

This publication presents t h e r e s u l t s of a t e s t c a r r i e d out by the Division of Building Research of the National Research Council with the use of i t s f i r e research f a c i l i t i e s . The t e s t was c a r r i e d out a t t h e request of t h e i n d u s t r i a l company concerned upon payment of the r e g u l a r t e s t fee. The i n i t i a l r e p o r t was submitted p r i v a t e l y t o t h i s company i n accordance with r e g u l a r DBR/NRC practice.

The t e s t r e s u l t s obtained a r e now published i n t h i s form with the agreement of the sponsor of t h e t e s t so t h a t the information may be a v a i l a b l e f o r general use. This procedure i s unlike t h a t normally followed i n the case of o t h e r t e s t s c a r r i e d out on proprietary products o r construc- t i o n s . It has been adopted i n t h e case of f i r e r e s i s t a n c e t e s t s because of the considerable c o s t of each t e s t which makes it desirable t o eliminate, a s f a r a s possible, the n e c e s s i t y f o r repeating such t e s t s on t h e same o r s i m i l a r constructions. Special care has been taken t o describe a l l the p e r t i n e n t f e a t u r e s of the materials, the construction and the method of t e s t , i n order t o make t h e r e s u l t s a s useful a s possible.

Ottawa

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FIRE TEST OF A "TRI-SEAL" FLOOR AND CEILING ASSEh'IBLY

This r e p o r t describes a f i r e t e s t conducted on a "Tri-Seal" f l o o r and c e i l i n g assembly of the Gypsum, Lime

and Alabastine Limited, on November 11, 1959. The t e s t was

requested by t h e Toronto Office of t h e Gypsum, Lime and

Alabastine Limited,

The main s i z e s and a l l construction d e t a i l s of t h e specimen are shown i n Figs. 1 and 2. S p e c i f i c a t i o n of the p a r t s and m a t e r i a l s i s given below. Note t h a t t h e item numbers correspond t o the p a r t numbers i n t h e f i g u r e s .

1. Reinforced. frame, made from r e f r a c t o r y castable supplied

by the Division of Building Research of the National

Research Council.

Concrete s l a b 2 in. t h i c k , made from ready-mixed concrete

of 2500 lb/sq i n . nominal compressive s t r e n g t h , supplied by a l o c a l f i n n . The a c t u a l s t r e n g t h of two specimens taken by B.R.C. p e r s o m e l from two d i f f e r e n t batches during the placement of t h e concrete was found t o be 3300 lb/sq i n . and 2700 lb/sq i n . , r e s p e c t i v e l y , a t 28

days. (The t e s t s were performed on cylinders made i n

conformance t o ASTM C31-49 and loaded according t o ASTM

C39-49.) On t h e day before t h e t e s t the r e l a t i v e

humidity i n the concrete ( a t a distance

13

i n . from t h e

s u r f a c e ) was found t o be l e s s than 40 per cent.

3. Clipped s t e e l mat, f a b r i c a t e d i n conformance t o ASmI

A184-37 from &in. b i l l e t - s t e e l b a r s (ASTM A15-54T) of s t r u c t u r a l grade, with 12- by 12-in. spactng.

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Metal f l o o r forms with inverted V-shaped corrugation along both edges, made by cold pressing from No. 28

gauge high s t r e n g t h low a l l o y cold-rolled s t e e l sheet (ASTM A374-54T), c u t t o 10-ft by approximately 17-in. s i z e s .

"Macomber Allspan" s t e e l f l o o r j o i s t s of 1 2 - f t c l e a r span, conforming t o s i z e No. 210A of Macomber Design Manual MA-59.

I*-in. galvanized roofing n a i l s with 3/8-in. diameter head.

Bridging angle of 1&- by 1&- by 3/16-in. s i z e s , conforming t o A I S I C1020.

&-

by 2-in. hexagonal head b o l t s , with nuts.

"Tri-Seal Loop Channels", a s shown i n Fig. 3, made from No. 25 gauge galvanized cold-rolled carbon s t e e l s t r i p s , conforming t o temper No. 4 of ASTM A109-49T.

Galvanized double-strand t i e wires of W and M gauge No. 18.

Pieces of perforated gypsum l a t h , with the f i b r e of paper coverings p a r a l l e l t o t h e s h o r t dimension (commonly known a s "Perforated Tri-Seal Lath"), i n 3/8- by 16- by 48-in. dimensions, conforming t o ASTM C37-54.

Cold-drawn s t e e l r e i n f o r c i n g wires of W and M gauge No. 12, conforming t o ASTM A82-34.

Base c o a t , 9/16 i n . t h i c k , made from m i l l aggregated p l a s t e r of a composition of 100 lb n e a t gypsum p l a s t e r and 2.2 cu f t p e r l i t e aggregate.

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14. 1/16 i n . f i n i s h c o a t , made from standard lime putty- p l a s t e r of p a r i s mixture.

1 . Ekxpanded metal l a t h i n 12-in. wide s t r i p s , approximately 2.5 lb/sq yd.

16. Red c l a y b r i c k s and mortar. 17. Asbestos wool.

A s may be seen from Fig. 1, t h e edges of the

specimen were simply supported. A clearance of 1 t o 13 in. w a s l e f t between the reinforced frame and t h e edges i n order t o eliminate any r e s t r a i n i n g f o r c e s r e s u l t i n g from h o r i z o n t a l thermal expansion of t h e specimen during t h e t e s t . The gap around t h e edges was f i l l e d with loosely packed asbestos wool.

The plastered surface of the c e i l i n g immediately before the t e s t i s shown i n Fig. 10.

The f l o o r and c e i l i n g assembly was of ordinary good workmanship. During t h e conditioning period s e v e r a l cracks developed on t h e surface of t h e concrete s l a b ; t h e l a r g e s t continuous crack was approximately 30 i n . i n

length and 1/16 in. i n width.

The age of t h e ,specimen was approximately 120 days a t t h e time of the t e s t .

TESTING PROCEDURE

The t e s t was c a r r i e d out i n accordance with AS!T!M

Specification E119-58. Furnace temperature was measured by

nine symmetrically disposed thermocouples enclosed i n 13/16-in.

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equipped with a carbon s t e e l cap a t t h e t i p . The h o t junction of t h e thermocouples was placed 1 2 i n . away from t h e exposed face of t h e sample. Both t h e i n d i v i d u a l temperatures a t nine p o i n t s of t h e furnace and t h e average of t h e nine temperatures were recorded. The f u e l i n p u t i n t o t h e furnace was c o n t r o l l e d i n such a way t h a t t h e average temperature c l o s e l y followed t h e prescribed temperature time c o r r e l a t i o n .

The unexposed s u r f a c e temperature was measured by nine thermocouples (Nos. 1 t o 9 ) covered with standard a s b e s t o s pads, 6 i n . square and 0.4 i n . t h i c k , symmetrically disposed a s shown i n Fig. 4. I n a d d i t i o n , f o u r thermocouples were cemented t o t h e unexposed s u r f a c e i n a way shown i n Pig. 5.

The l o c a t i o n of t h e s e thermocouples (Nos. 11 t o 1 4 ) i s a l s o shown i n Fig. 4.

I n o r d e r t o study t h e flow of h e a t through t h e specimen, twelve a d d i t i o n a l themnocouples were i n s t a l l e d w i t h i n t h e s t r u c t u r e . These thermocouples (Nos. 15 t o 26) were a l s o symmetrically disposed and a r e shown i n t h e general thermocouple l a y o u t drawing ( Pig. 4 )

.

The s u r f a c e of t h e specimen was s u b j e c t e d t o a v e r t i c a l load of 125 lb/sq f t , a p p l i e d through a hydraulic loading device c o n s i s t i n g of 30 jacks. The load was t r a n s -

f e r r e d t o t h e specimen a t n i n e t y p o i n t s ( s e e Pig. 11) s o t h a t t h e c o n d i t i o n of uniform load d i s t r i b u t i o n was reasonably well approximated.

A mechanical device was used t o measure t h e v e r t i c a l 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 specimen.

A d e t a i l e d d e s c r i p t i o n of t h e f i r e t e s t f a c i l i t i e s of t h e National Research Council i s a v a i l a b l e (1).

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RESULTS

Uniformity of t h e furnace temperature was very good throughout t h e t e s t ; maximum deviation from t h e average was always l e s s than 100°F. A p l o t of t h e average tempera- t u r e a g a i n s t time i s shown i n P i g .

7.

Variation of t h e unexposed surface temperature was roughly i n d i c a t i v e of s t r u c t u r a l d i s i n t e g r a t i o n of the c e i l i n g construction. Where the d i s i n t e g r a t i o n developed more r a p i d l y , moderately higher temperatures were recorded on the unexposed surface. I n Pig. 7 the v a r i a t i o n of both t h e average and the maximum temperatures of the unexposed surface a r e shown.

Thermocouples'~cemented t o the surface recorded somewhat lower temperatures, the average of which i s a l s o p l o t t e d i n t h e same f i g u r e .

Temperatures obtained from various points i n the i n t e r i o r of the s t r u c t u r e showed a very remarkable spread. This was obviously due t o t h e i r r e g u l a r d i s i n t e g r a t i o n of t h e p l a s t e r l a y e r and t h e gypsum l a t h . Generally speaking, the thermocouples placed n e a r e r t h e centre o r the exposed surface recorded higher temperatures than those f a r t h e r f r o m t h e centre o r t h e exposed surface. C h a r a c t e r i s t i c curves a r e shown i n Pig. 7.

The v a r i a t i o n of t h e c e n t r a l (maximum) d e f l e c t i o n and t h e r a t e of d e f l e c t i o n a r e p l o t t e d i n Pig. 8. _Deflection of 0.45 in. a t zero time i s due t o t h e imposed 125 lb/sq ft load before t h e s t a r t of t h e t e s t . After 2 hours of t e s t t h e d e f l e c t i o n a t t h e centre became l a r g e r than t h e a v a i l a b l e

s b h of the jacks, so t h a t two jacks around t h e centre became i n e f f e c t i v e . Thus the slope of the d e f l e c t i o n curve shows a sudden decrease a f t e r 120 minutes t e s t i n g .

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The f i r e t e s t was terminated a t 2 hours and 7 minutes. According t o ASTM E119-58 t h e t e s t i s regarded a s successful f o r a 2-hour period.

COMMENT

The process of d i s i n t e g r a t i o n of the fire-exposed c e i l i n g s t r u c t u r e appears t o have been a s follows:

Within

5

minute of the s t a r t of the t e s t the f i n i s h p l a s t e r began t o peel from t h e c e i l i n g i n large patches. I n o t h e r places moisture s t a i n s appeared on t h e surface, A f t e r 12 minutes the base p l a s t e r coat commenced t o crack along t h e "Tri-Seal Loop Channels", Cracks gradually opened t o a $-inch width a s the pieces of gypsum l a t h and adhering base coat began t o sag. After 25 minutes o t h e r cracks running a t r i g h t angles t o the previous ones, mostly a t the j o i n t s of t h e pieces of gypsum l a t h , a l s o appeared. Where the various pieces sagged d i f f e r e n t l y , these l a t t e r cracks grew r a p i d l y , and a t 27 minutes the first gap on the c e i l i n g , about _.. 1 inch i n width, became

v i s i b l e . I n quick succession other gaps formed and a t 35 minutes the f i r s t l a r g e r s e c t i o n of the gypsum l a t h , approximately 1 6 by 36 i n . i n s i z e , f e l l off the c e i l i n g together with the adhering base coat. The gap and hole formation on t h e c e i l i n g marked the beginning of a rapid temperature r i s e i n s i d e t h e c e i l i n g - f l o o r assembly, a s may be seen i n Fig. 7, and r e s u l t e d i n an increased r a t e of d e f l e c t i o n (Fig. 8 ) .

From t h i s point on t h e d i s i n t e g r a t i o n o f t h e base coat and gypsum l a t h ,developed rapidly, Many new gaps formed perpendicular t o t h e d i r e c t i o n of the "Tri-Seal Loop Channelsw, but t h e t i e wires prevented separate pieces from f a l l i n g down. It was n o t u n t i l 55 minutes a f t e r t h e s t a r t of t h e t e s t t h a t a second, l a r g e r piece of c e i l i n g gave way. A t 1 hour and 18 minu- t e s another l a r g e piece f e l l down and t h e s t e e l j o i s t s became v i s i b l e .

The d i s i n t e g r a t i o n process of t h e c e i l i n g i s i l l u s - t r a t e d i n P i p - 9 - w h e r p +he + n + c a l AC r e -

----

1 - - - - ,

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p l o t t e d versus time. This curve i s believed t o be c o r r e c t within

-

+

10 per cent.

Figure 6 shows t h e s t a t e of t h e c e i l i n g a f t e r the t e s t . The diagram was reconstructed from two photographs

taken immediately a f t e r termination of the t e s t ; one of these i s shown a s Fig, 1 2 . The area of complete d i s i n t e g r a t i o n i s cross-hatched. Within t h i s area s e v e r a l fragments of gypsum l a t h and p l a s t e r were s t i l l hanging on t h e t i e wires, b u t these pieces no longer c o n s t i t u t e d s i g n i f i c a n t s h i e l d i n g f o r t h e

s t e e l j o i s t s .

A s may be seen from Fig. 1 2 , the base coat adhered

very well t o t h e gypsum l a t h throughout t h e t e s t . The two l a y e r s acted a s a s i n g l e u n i t , apparently because of the perforations of the l a t h . It may a l s o be seen t h a t t h e t i e wires played an important p a r t i n the f i r e endurance of the

s t r u c t u r e . They held the pieces of p l a s t e r and gypsum l a t h - I

i n position even a f t e r most of t h e i r s t r e n g t h had been l o s t , and in t h i s way, though i n d i r e c t l y , protected t h e load-bearing s t e e l j o i s t s from t h e r a d i a t i n g heat.

A s mentioned e a r l i e r , several cracks were observed on the surface o f the concrete s l a b before the t e s t . A f t e r

80 minutes a number of o t h e r cracks gradually developed, from some of which steam was issuing, A t such places where the surface was below b o i l i n g point, the steam p a r t l y con- densed i n t h e cracks and slowly f i l l e d them up with moisture, a s i s shown i n Fig. 11.

Robertson and Ryan ( 2 ) developed c r i t e r i a f o r defining t h e load f a i l u r e of f i r e t e s t specimens i n terms of d e f l e c t i o n and r a t e of deflection. It has been proposed t h a t the point a t which both

and

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can be regarded a s an i n d i c a t i o n of load f a i l u r e . I n these c o r r e l a t i o n s

D = maximum d e f l e c t i o n , i n . R = r a t e of d e f l e c t i o n , i n . / h r

L = span of t h e p r i n c i p a l s t r u c t u r a l element, i n .

d = d i s t a n c e between t h e upper and lower extreme f i b r e s of the p r i n c i p a l s t r u c t u r a l element, i n . I n t h i s case L = 144 i n . , d = 10.125 i n . , t h e r e - f o r e bhe c r i t i c a l d e f l e c t i o n i s

-

D o r i t

-

00 1 4 4 ~ = 2.56 i n . and the c r i t i c a l r a t e o f d e f l e c t i o n

-

144* R c r i t 150

x

_{10.125 = 13.65 in./hr = 0.228 in./min.} These c r i t i c a l values a r e marked with arrows i n

Fig. 8, It may be seen t h a t by the end o f t h e t e s t t h e maximum d e f l e c t i o n exceeded the c r i t i c a l value by more than t h r e e times, although t h e r a t e of d e f l e c t i o n remained below t h e above defined l i m i t . According t o t h e Robertson-Ryan c r i t e r i a , t h e r e f o r e , t h e f l o o r and c e i l i n g assembly was n o t due t o c o l l a p s e a t t h e time when t h e t e s t was terminated.

1. Shorter, G. W., and T. 2. Harmathy. F i r e Endurance Test F a c i l i t i e s a t t h e National Research Council, N.R.C., Division o f Building Research, DBR F i r e Study No. 1, Ottawa, July 1960. NRC 5732.

2. Robertson, A . P., and J. V. Ryan. Proposed C r i t e r i a f o r Defining Load F a i l u r e o f Beams, Floors and Roof

Constructions During F i r e Test. J. Res. Natl. Bureau Stds.,

_-

63C, p.121-124 (1959).

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- _A_' _-- _"

- .

--

I.. . -

. I I

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THERMOCOUPLES ON THE UNEXPOSED SURFACE UNDER STANDARD ASBESTOS PADS

CEMENTED TO THE SURFACE

THERMOCOUPLES W I T H I N THE STRUCTURE

@

ON TOP OF GYPSUM L A T H

V

ON THE BOTTOM CHORD OF STEEL JOISTS

A

ON THE TOP CHORD OF STEEL JOISTS

0

_{ON TOP OF METAL FLOOR FORMS}

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F

LEGEND

Th

THERMOCOUPLE W I R E S

F

FLOOR

C

CEMENT

FIGURE

5 NON

-

STANDARD UNEXPOSED SURFACE

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FIGURE 6

THE STATE OF THE C E I L I N G A F T E R FIRE T E S T

(DISINTEGRATED PORTIONS CROSS HATCHED)

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T I M E ( M I N I

TEMPERATURES W I T H I N THE STRUCTURE TEMPERATURES ON THE UNEXPOSED SURFACE I AVERAGE NEAR THE GYPSUM L A T H , NEAR THE CENTRE A MAXIMUM OBTAINED B Y STANDARD METHOD 2 AVERAGE NEAR THE GYPSUM LATH, FAR FROM THE CENTRE B AVERAGE OBTAINED B Y STANDARD METHOD 3 AVERAGE N E A R THE CONCRETE SLAB, NEAR THE CENTRE C AVERAGE OBTAINED B Y METHOD SHOWN IN