Product development and fire performance

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Product development and fire performance

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PRODUCT DEVELOPMENT AND FIRE PERFORMANCE

33v

P R O D U C T DEVELOPMENT AND FIRE P E R F O R M A N C E - 0

by

W . W. Stanzak

U n t i l r e c e n t years f i r e resistant assemblies evolved more through

practice than conscious development, They generally comprised w e l l

known materials such as plaster, brick and concrete, long recognized

f o r t h e i r f i r e e n d u r i n g qualities. Fire research, however, has resulted

in the development of performance requirements for f i r e resistance and

information on how these can be effectively and economically achieved.

This has been in response to increased building volume and the availability

of new building materials. Today, development of products and systems

i s often aimed at specklic building markets f o r which the fire resistance

requirements are well defined,

Demonstration of _Performance

Contemporary building codes recognfze a fire endurance t e s t

a s the only method of demonstrating the performance of a new building

product, element or assembly. Such t e s t s a r e carried out in _accordance with the provisions of

GSA B54.3-1964

standards provides f o r exposing a building element o r a s s e m b l y t o a fire of controlled exLent and severity under conditions pertaining as nearly a s possible o r practical. to those encountered in service. The criteria

of acceptance are prescribed so _{as to define the time during which the}

specimen can prevent undue heat transmission and collapse.

Fire testing is a tirne-consuming and costly undertaking. The

fee for major elements (floors, roofs, bearns, columns, w a l l s ,

partitions) varies with the assembly, but it i s currently i n the o r d e r of

several thousand dollars for a standard test. Other c o s t s to the sponsor

are generally at least as much as t h e fee itself, often m o r e . It is

except with very unsophisticated assemblies,

It

is a success another t e s t may be d e s i r e d either to broaden the scope

of _{application o r to achieve a more economical assembly, )}

The time required from receipt of _{application to completion of}

test need not be long

if

ducts. Many common assemblies, however, contain ready-mixed con-

crete that requires a conditioning period of from six weeks t o three

months, o r _{even longer} in rare c a s e s .

I

3

facility again be c a m e s available,

Pilot Tests

Because af the c o s t s and time involved in a complete full-scale

f i r e t e s t it may often be advantageous to carry out _{one or more pilot} t e s t s to investigate specific aspects of the proposed system. W h e r e

the insulating value of a component under fire - t e s t conditions is un-

known and difficult to predict one or more small-scale t e s t s may often

provide the required information at relatively low cost. Where the

mechanical performance (reaction t o thermal stresses and deformation)

of a major component, such as a suspended ceiling, is in doubt it: is

usually necessary t o go t o the full-scale. It may still be worthwhile,

however, to _{employ a full-scale pilot t e s t designed} to investigate t h i s

one aspect of the proposed system because savings in time and money

c a n be achieved through simplification of the t e s t assembly and the

t e s t procedure and reporting of results.

Pilot t e s t s can often be arranged through negotiation with the

testing laboratory. W h a t t e s t s a r e deemed necessary and in what

o r d e r they should best be _{p e r f o r m e d depends on the design com-}

The l e s s experienced the designer, the more t e s t s he may require to

obtain the needed information. Generally, it is advisable to do the

small -scale heat transmission t e s t s fir st. Extremely careful judge

-

rnent must be exercised in applying data from either type of t e s t to the design of an actual t e s t assembly.

Designing a P i l o t A s sernbly 1 , Small

-

For simple constructions the scaling down is in _{only two d i -}

mensions, length and width. For layer constructions containing large

air gaps, scaling d o w n may be in three dimensions, since the depth

of the air gap does not significantly d e c t fire endurance provided it

exceeds

a

-

fecting heat transrnis sion through the assembly need be present.

Hangers, clips, supports, decorative facings and finishes, etc.

,

b e s t omitted; joints, thermal bridges, atc.

,

f o r reasonable correlation between small-scale and standard t e s t re

-

sults, the depth of the construction should not exceed 20 _per cent of

the lesser lateral dimension.

2 . Full -scale

This type of pilot t e s t can be used to advantage only to investigate a m a ~ o r component of an assembly, not the entire assembly. As it _is

difficult to generalize, this discussion w i l l be l i m i t e d to the pilot testing of

suspended ceilings, the mast popular utilization of the full -scale pilot te st.

The ceiling i s suspended from a _{furnace lid or attached to unloaded}

structural members placed in the t e s t frame. F O P directly meaningful

results the installation must be identical in all respects to that intended f o r the standard test. Otherwise a single pilot t e s t w i l l probably not *At DBR/NRC these facilities can be used to t e s t samples in a vertical

provide sufficient evidence to enable the f i n a l design to be undertaken with

confidence.

Designing a Representative A s s e ~ n b l y

T h e latest f i r e t e s t standard, ASTM E119-69, s t a t e s that "The

test specimen s h a l l be truly representative of the c o n s t r u c t i o n f o r which

classification is desired, as to materials, workmans hip, and details such

as dimensions of parts, and shall b e built under conditions representative

of those obtaining as practically applied in b u i l d i n g construction and op-

eration. 9' T h e s e requirements are not simple. Nevertheless, a genuine

attempt should be made to design a "r epresentativetl assembly f o r the f i r e t e s t .

Fire t e s t s are m o s t frequently sponsored for one of the following

purposes:

(1) to demonstrate suitability of a new component in a c o m m o n l y u s e d

type of construction,

(2) to evaluate a new type of construction using predominantly stand-

ard components,

(3) to evaluate a new type of construction using new types of components.

T h e factors influencing the d e s i g n will be different for each c a s e :

(1) Time is generally of essence in this situation, so that it is p r e f e r -

able to choose an assembly that dries as quickly as p o s s i b l e . F o r

floor constructions the b e s t choice is a _{j o i s t - suppor ted c o n c r e t e slab}

placed on metal rib-lath. This type of a s s e m b l y has a c o n d i t i o n i n g period of approximately six weeks. By a ~ r e e m e n t with the test a u t h o r i t y and other sponsors who have tested assemblies t h e u s e of

the component under t e s t can then be extended to other t y p e s of

Existing information can b e v e r y useful as a guide f o r testing a new building component; the U n d e r w r i t e r s ' Laboratories l i s t i n g s ,

f o r example. Once a suitable assembly has been chosen, only the

particular component under investigation should b e changed; all o t h e r

rl etails a r r as alread

r

T h c rlcveloprncnt of a new typc of stud f a r n o n - b s a r i n ~ w a l l s

may serve t o illustrate. The stud attachrncnt to floor and c e i l i n g , t h c

s c r e w spacing on t h e wallboard, the lateral bracing of the studs (if any),

and joint treatment should all be c a r r i e d out as f o r the previously tested

assembly that provided the desired f i r e r a t i n g .

A rare application of the f i r e t e s t is its use to achieve economic

superiority aver an already tested assembly. O n e example is

the introduction of air spaces i n t o m u l t i p l e -layer constructions

.

H e r e it is important that the assembly be designed in all r e -

spects as it is intended to b e constructed in the f i e l d , although t h e thickness of air s p a c e s may often be reduced. Details of

attachment, suspension, etc

.

,

(3) The scope and extent of aytplication is not accurately known when

an e n t i r e l y new t y p e of construction is to b e evaluated.

An

f o r standards i n this market, for example ,the Central M o r t g a g e

and Housing Corporation. In other respects the design should be

governed by c ansiderations of expediency and existing data, as

indicated previously.

F o r all t h c s e situations i t i s imperative to use only production i t e m s or prototypes of the production items. W h e r e members a r e to

b e spliced in the field, splices should occur in the t e s t assembly. If a

various utilities, this should be represented in t h e t e s t specimen. The

fire test a u t h o r i t y can usually provide guidance as to what is d e s i r a b l e and acceptable.

In spite of thr? g e n e r a l i t y of t h e test s t a n d a r d , certain r e q u i r c -

mcnts art: c a l l e d f o r in t e s t p r a c t l c c . F o r cxarnple, i t i s not acccptahlc

t o _{have rrlurc than one t y p c oi prr~cluct as a m a j o r corrlponent of an a s -}

sembly. For a _{partition this means that only one type} of _{w a l l c a v e r i n ~}

must b e used on the e n t i r e s u r f a c c .

T o

lower half of the wall would n o t be acceptable. The n u m b e r of fixtures,

also,should relate t o the area of the assembly under t e s t . There should

neither b e m a n y more n o r many less than will be encountered in con-

s truc tion practice,

Conclusion

The vagueness of fire t e s t standards leaves the design of t h e

a s s e r r l h l y e s s e n t i a l l y to t h e discretion of those who submit or s p o n s o r it.

In practice, t h e _{d e s i g n is regulated to some extent by recommendations} of the t e s t l a b o r a t o r y , but there is ample opportunity for t h e knowledgeable d e s i g n e r to develop an optimum assembly f o r his particular purposes, in