Spatial separation of buildings

(1)

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Spatial separation of buildings

(2)

R e f Ser I TH1 R4;7

:

COPY nOioi87

+

/

I

[RC I-"J'E~

NATIONAL

RESEARCH

COUNCIL

CANADA

NOT FOR PUBLICATION

DIVISION OF BUILDING RESEARCH

WARNING

THlS I S A SPECIAL DOCUMENT WHICH D.B.R. I S PRIVILEGED

TO HAVE FOR REFERENCE PURPOSES ONLY. I T MUST NOT

.i

BE QUOTED OR LISTED I N ANY REPORT OR PUBLICATION JWC" ,/ d

/--- UNLESS SPECIFIC WRITTEN PERMISSION FOR THIS HAS

/ BEEN OBTAINED THROUGH THE DIRECTOR.

SPATIAL

SEPARATION OF

BUILDlNGS

ANALYZED

THlS REPORT HAS BEEN PREPARED FOR INFORMATION AND RECORD PURPOSES AND I S NOT TO BE CITED AS A REFERENCE IN ANY PUBLICATION

OTTAWA

NOVEMBER 1959

(3)

MATIONffi RESEBRCH COUNCIL CANADA

DIVISION OF BUILDING

RESEARCR

SPATIAL SEPARATION OF BUILDINGS by

( P r e p a r e d for the BRC A s s o c i a t e C o m m i t t e e

on

the N a t i o n a l B u i l d i n g C o d e )

ANALYZED

Internal

Report

No. 187

of the

D i v i s i o n o f Building R e s e a r c h

OT'PAWA O c t o b e r 1959

(4)

One of t h e r e a s o n s why work on t h e N a t i o n a l B u i l d i n g Code of Canada (which i s i s s u e d under t h e a u t h o r i t y of t h e N.R.C. A s s o c i a t e Committee on t h e N a t i o n a l B u i l d i n g Code) i s c a r r i e d o u t by s t a f f of t h e D i v i s i o n of B u i l d i n g Research

-

always t o t h e d i r e c t i o n of t h e A s s o c i a t e Committee

-

i s s o t h a t t h e Code may b e n e f i t by t h e l a t e s t i n f o r m a t i o n on b u i l d i n g d e s i g n , and b u i l d i n g t e c h n i q u e s , a v a i l a b l e through t h e work of t h e D i v i s i o n . Correspondingly, one o f t h e most e f f e c - t i v e ways i n which t h e r e s u l t s . of t h e r e s e a r c h work of t h e D i v i s i o n can be of p u b l i c s e r v i c e i s through a p p l i - c a t i o n in. r e v i s i o n s o f t h e N a t i o n a l B u i l d i n g Code,

Up t o t h i s t i m e , r e l e v a n t i n f o r m a t i o n from t h e D i v i s i o n h a s been passed d i r e c t l y t o t h e A s s o c i a t e Committee f o r t h e i r u s e , t h u s b e i n g confined, i n t h e

first i n s t a n c e , t o n e c e s s a r i l y p r i v a t e Committee papers. I n o r d e r t o make a l l such i n f o r m a t i o n more q u i c k l y

a v a i l a b l e f o r g e n e r a l u s e , it h a s been decided t h a t i n f u t u r e it s h a l l be r e c o r d e d i n t h e r e g u l a r s e r i e s of

D.B.R.

I n t e r n a l Reports. T h i s i s t h e first r e p o r t t o b e prepared and i s s u e d f o r t h i s purpose, b u t i t w i l l be t h e first of a c o n t i n u i n g s e r i e s , The a u t h o r i s a r e s e a r c h o f f i c e r i n t h e F i r e S e c t i o n of t h e D i v i s i o n of B u i l d i n g .Research; he joined t h e staff o f t h e Council a f t e r s e r v i c e w i t h t h e B r i t i s h J o i n t F i r e Research S t a t i o n , b e i n g a g r a d u a t e i n p h y s i c s o f t h e U n i v e r s i t y of London. H e was a n a c t i v e p a r t i c i - p a n t i n t h e S t . Lav~renoe Burns, from which some o f t h e information h e r e i n r e c o r d e d was obtained.

The r e p o r t i s now i s s u e d f o r inforn,ation, and i n t h e hope t h a t t h e D i v i s i o n may b e favoured w i t h

c r i t i c a l comments upon i t s conclusions. It must be understood t h a t t h e s e a r e p r e s e n t e d f o r convenience

o n l y ; t h e use t h a t i s made of t h e i n f o r m a t i o n h e r e i n r e c o r d e d by t h e A s s o c i a t e Committee on t h e N a t i o n a l B u i l d i n g Code i s n a t u r a l l y a m a t t e r f o r d e c i s i o n by

t h e Committee. !l!he D i v i s i o n , however, i s p l e a s e d t o be a b l e t o make i n t h i s way t h i s f u r t h e r c o n t r i b u t i o n t o t h e p r o g r e s s of t h e N a t i o n a l Build-ing Code.

Ottawa

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SPATIAL

SEPARATION OF BUILDINGS

J. H. McGuire

m e spread of f i r e between two buildings may r e s u l t from (1) :

1. Flying brands,

2. Convective h e a t t r a n s f e r , and/or

3 .

Radiative h e a t t r a n s f e r .

Flying brands may i n i t i a t e secondary f i r e s a t sub-

s t a n t i a l d i s t a n c e s from t h e primary f i r e , e . g . , a q u a r t e r of a mile (2), and t h u s i t i s n o t p r a c t i c a l t o consider

s p a t i a l s e p a r a t i o n between buildings a s a means of combatting t h i s hazard. Fortunately o t h e r means a r e a v a i l a b l e ( 2 ) .

Convective h e a t t r a n s f e r w i l l only cause i g n i t i o n i f

t h e temperature of t h e gas stream I s s e v e r a l hundred degrees Centigrade. Such high gas temperatures a r e only t o be found i n o r very near t o the flames emanating from t h e windows of burning buildings.

Since i g n i t i o n by r a d i a t i o n from a burning building can occur a t distances g r e a t e r than those t o nhich t h e flames generally extend ( 3 ) it follows t h a t r a d i a t i v e h e a t t r a n s f e r i s t h e f a c t o r of primary importance i n producing spread of f i r e a c r o s s a space s e p a r a t i o n be-t;ween~buildings. !The w r i t e r r e c e n t l y v i s i t e d t h e scene of a f i r e i n a dwelling i n which t h e neighbouring houses were i g n i t e d . The s e p a r a t i n g d i s -

t a n c e s i n each case were 14 f t 8 i n . and it might t h e r e f o r e be thought t h a t the spread o f f i r e could have been caused d i r e c t l y by the flames o r a t l e a s t by h o t gases. % a t it was, i n f a c t , r a d i a t i v e h e a t translter i s c l e a r l y demonstrated by t h e following ( 4 ) :

"...

the secondary f i r e s on the s i d e w a l l s of t h e

two

neighbouring dwellings had only been i n i t i a t e d on t h e v e r t i - c a l f a c e s d i r e c t l y exposed t o r a d i a t i o n from the burning dwelling. The undersides of the eaves were only discoloured where flames from t h e secondary f i r e had played on them;

t h e under edges o f c e r t a i n exposed boards were not discoloured a t a l l . "

That -the r a d i a t i o n l e v e l i s the f a c t o r of prime importance i n determining t h e separation which should be e s t a b l i s h e d between buildings h a s , of course, been known

f o r a long time and it i s t h i s p r i n c i p l e which forms the b a s i s f o r t h e r e l e v a n t s e c t i o n of t h e 1953 National Building Code

( 5 ) .

(6)

W i t h a view t o s i m p l i f y i n g t h i s code a number of assumptions were adopted. Now t h a t t h e code h a s been

i n

u s e f o r some

y e a r s and t h e u n d e r l y i n g p r i n c i p l e

i s

more g e n e r a l l y understood a n a t t e m p t can be made t o r e f i n e t h e space s e p a r a t i o n r e q u i r e - ments. !Ithe o b j e c t of t h i s r e p o r t

i s

t o a t t e m p t t o make s u c l ~

a

development w i t h o u t unduly complicating t h e code.

The 1953 N a t i o n a l B u i l d i n g Code

It i s s c a r c e l y p o s s i b l e t o formulate a code t h a t could be s u c o e s s f u l l y implemented i f it

i s

t o r e f e r d i r e c t l y t o t h e

space s e p a r a t i o n of b u i l d i n g s . The requirements of t h e 1953 code a r e , t h e r e f o r e , very w i s e l y r e f e r r e d t o t h e boundary of t h e l o t upon which t h e b u i l d i n g w i l l be e r e c t e d . !the e x t e r i o r

w a l l of a b u i l d i n g would meet t h e requirements of t h e approp- r i a t e s e c t i o n of t h e code:

( i ) i f , having no windows,

i t s

f i r e r e s i s t a n c e time complied w i t h column 2 of Table I ( s e e below), t h e independent v a r i a b l e being f i r e l o a d , o r

(ii) i f , i t s f i r e r e s i s t a n c e complied w i t h column 2

of !i!able I, except t h a t up t o 20 p e r c e n t of i t s a r e a were occupied by window space o r o t h e r u n p r o t e c t e d opening, and i f

i n

a d d i t i o n

i t s

s e p a r a t i o n from t h e l o t l i n e were a t l e a s t half t h e value g i v e n by column

3

of Table I, o r

(iii) i f

i t s

s e p a r a t i o n from t h e l o t l i n e were a t l e a s t t h a t g i v e n by column 3 of Table I.

TABLE

I

NBC REQUIREDBENTS FOR CONSTRUCTION

AEJD SPACE SEPARA(PI0BS

P o s s i b l e Developments Column 1 F i r e Load 10 l b / f t 2 20 l b / f t 2 30 _{l b / f t 2}

The code has a l r e a d y i n t r o d u c e d t h e concept t h a t

d i s t a n c e s of s e p a r a t i o n must be r e l a t e d t o percentage window opening b u t only t h r e e v a l u e s of window opening a r e l i s t e d : z e r o , 20 p e r c e n t and 100 p e r c e n t . It

might

be d e s i r a b l e t o i n c l u d e i n t e r m e d i a t e v a l u e s .

Column 2

Fire Resistance Time

1 hour 2 h o u r s 3 h o u r s Column

3

Spaoe S e p a r a t i o n ( r e f e r r e d t o l o t l i n e ) 1 5 f e e t 20 f e e t 25 f e e t b

(7)

A more important f a c t o r f o r which provision i s

d e s i r a b l e i s t h a t t h e d i s t a n c e from a b u i l d i n g

a t

which a p a r t i c u l a r l e v e l of r a d i a t i o n i s given

i s a

f u n c t i o n

of

t h e dimensions of t h e b u i l d i n g i n a d d i t i o n t o t h e percentage

windoin opening. If two sources have t h e same temperature,

e m i s s i v i t y , and shape t h e n t h e d i s t a n c e s from t h e trvo a t which t h e i n t e n s i t i e s a r e t h e same a r e r e l a t e d by t h e dimen-

s i o n a l s c a l e f a c t o r . This property i s i l l u s t r a t e d i n Fig. 1 wliere t h e r a d i a t i n g s u r f a c e s a r e r e l a t e d by t h e s c a l e f a c t o r

3

f t

-+

2 f t = 18 i n c h e s

+

12 Inches = 1.5. The two r e c e i v i n g s u r f a c e s have t h e same l e v e l of r a d i a t i o n i n c i d e n t upon them s i n c e t h e i r o r i e n t a t i o n and r e l a t i v e geometrical l o c a t i o n a r e t h e same and t h e i r d i s t a n c e s from t h e r a d i a t i n g s u r f a c e s a r e a l s o r e l a t e d by t h e f a c t o r 1.5.

It must be emphasized t h a t although t h e d i s t a n c e a t

which a p a r t i c u l a r i n t e n s i t y i s given i n c r e a s e s w i t h both s i z e of b u i l d i n g and percentage window opening t h e r e l a t i o n - s h i p s a r e n o t l i n e a r and hence t h e d i s t a n c e i s n o t a f u n c t i o n of t h e product, i . e . of t h e t o t a l window area.

The p o s s i b l e a p p l i c a t i o n of a p r i n c i p l e such as t h i s r e q u i r e s s knowledge of t h e l e v e l s of r a d i a t i o n t o be expected from b u i l d i n g f i r e s and of t h e l e v e l s of r a d i a t i o n t h a t w i l l i g n i t e common b u i l d i n g m a t e r i a l s .

Available Infoxmation

The formulation of a s e p a r a t i o n code, based on t h e p r i n c i p l e s discussed above h a s been considered by Bevan

and Webster (1). They r e p o r t t h a t c o n s i d e r a t i o n o f t h e maximum temperature t o which timber can be r a i s e d without undue r i s k of f i r e suggested

a

r a d i a t i o n l e v e l of 0.2 cal/cm2/sec i s t h e

maximum t o which timber should be subjected. It was assumed

t h a t t h e window openings of a b u i l d i n g c o n s t i t u t e t h e r a d i a t i n g a r e a s and t h a t t h e i r blaok body temperature i s 1000°C. On t h i s b a s i s t h e c o n f i g u r a t i o n f a c t o r * P of t h e window openings, a t a n exposed b u i l d i n g , should be reduced t o 0.056. The v a l i d i t y of t h e c o n f i g u r a t i o n f a c t o r concept i n t h i s a p p l i c a t i o n i s discussed i n Appendix A.

*

!J!he c o n f i g u r a t i o n f a c t o r of a r a d i a t i n g a r e a with r e s p e c t t o a n elemental r e c e i v i n g a r e a may be defined a s t h e r a t i o of t h e i n t e n s i t y of r a d i a t i o n a t t h e r e c e i v i n g element t o t h e i n t e n s i t y n e a r t o t h e r a d i a t o r . Its value i s dependent s o l e l y on t h e geometrical r e l a t i o n s h i p between t h e r a d i a t o r and t h e r e c e i v i n g element and may l i e between z e r o and u n i t y .

(8)

This t h e o r e t i c a l approach was supported by obser- v a t i o n s a t two f i x e s . In t h e first the behaviour of a s e r i e s

of exposed window frames was a s shown i n Table I1 (Table

3

of the Bevan and FJebster Report)

.

TABLE 11.

DANLhGE RELATED ICO CONPIGURAiCIOM

PACTOR ,-

Such p r a c t i c a l r e s u l t s suggest t h a t t h e configuration f a c t o r should undoubtedly be reduced t o l e s s than 0.093 i f

n o t t o l e s s than 0.067. I n t h e second example a timber boarding had i g n i t e d a t a configuration f a c t o r of 0.092. This merely

confirms t h a t such a value of

I?

i s t o o . h i g h t o be s a f e .

.

I? 0.067 0.067 0.081 0.093 0.112

A conflagration t h a t occurred a t Winnipeg i n June 1956 ( 6 ) probably gives t h e most valuable information on t h e acceptable l i m i t o f t h e configuration f a c t o r since values can be derived f o r both of the conditions: i g n i t i o n occurring and n o t occurring. A plan of t h e buildings involved i s shorin i n Fig. 2. When the f i r e was confined t o the Time Building alone and a l l the v ~ a l l s of t h e building remained intac3-t the

maximum value of the configuration f a c t o r of t h e window openings a t t h e !I?. Eaton Building mas approximately 0.05. Shortly

afterwards t h e e a s t vial1 of t h e Time Building collapsed, t h e Msmorr Building i g n i t e d and, when both buildings were burning f u r i o u s l y a number of the window surrounds of the

T.

B t o n Building e i t h e r caught f i r e o r began charring. Sparks and f l y i n g brands would have been p s s i n g n e a r

t o

t h e building most of the time and t h e a v a i l a b l e evidence l e a d s t o t h e con-

Condition of Window Frame Paint b l i s t e r e d

Paint b l i s t e r e d , l i t t l e charring Surface charring

Burned Burned

clusion t h a t the mechanism involved was p i l o t i g n i t i o n . llhe maximum configul-ation f a c t o r a t the

T.

_{Eaton Building a t}

about t h i s time was about 0.1.

A l l t h e above information r e l a t e s t o f i r e s which have been a a c i d e n t a l l y i n i t i a t e d and which have been combatted

by f i r e departments. Further p e r t i n e n t information was obtained from some experimental f i r e s which were c a r r i e d out during the winter of 1957-6 i n buildings rendered d e r e l i c t a s a r e s u l t

(9)

Radiation. measurements were made a t t h r e e l o c a t i o n s r e l a t i v e t o each b u i l d i n g and i n a d d i t i o n a t o t a l r a d i a t i o n measure-

ment was made a t one windovi f o r each f i r e . Table 111, which i s t a k e n from t h e r e l e v a n t r e p o r t s

( 3 ,

7 ) ,

l i s t s t h e maximum i n t e n s i t i e s which were recorded. To make t h i s i n f o r m a t i o n a p p l i c a b l e t o t h e p r e d i c t i o n of r a d i a t i o n i n t e n s i t i e s from

o t h e r b u i l d i n g s a s d i s c u s s e d i n Appendix A , t h e c o n f i g u r a t i o n f a c t o r s of t h e window openings a t each of t h e p o i n t s of

measurement were c a l c u l a t e d . Dividing t h e r a d i a t i o n i n t e n s i t i e s ( I ) by t h e s e v a l u e s of I?, t h e c o x f i g u r a t i o n f a c t o r , gave t h e

h y p o t h e t i c a l r a d i a t i o n l e v e l s

I/F

emanating from t h e windows. It must be emphasized t h a t t h e s e d e r i v e d l e v e l s a r e n o t r e a l , b u t a r e t h o v a l u e s t h a t would have been r e q u i r e d t o produce t h e measured r a d i a t i o n l e v e l s had t h e window openings been t h e s o l e source o f r a d i a t i o n . !Phis f a c t i s

i l l u s t r a t e d by cornpasring t h e v a l u e s w i t h t h o s e corresponding t o t h e m a x i m u m b l a c k body temperatures r e g i s t e r e d by t h e t o t a l r a d i a t i o n pyrometer(7).il3ne h y p o t h e t i c a l v a l u e s exceed t h e maxima g i v e n by t h e t o t a l r a d i a t i o n pyrometor by a s much a s a f a c t o r of 10. !The d i f f e r e n c e between t h e s e two v a l u e s i s a s s o c i a t e d

w i t h t h e i n t e n s e flaming from t h e windows of t h e b u i l d i n g s , which made a g r e a t e r c o n t r i b u t i o n t o t h e maximum l e v e l of r a d i a t i o n t h a n d i d t h e window openings themselves. That t h e concept i s u s e f u l a s a means of comparison, however, i s

demonstrated by t h e o r d e r of a g r e e m e n t f o r each b u i l d i n g

between t h e v a l u e s of I/F d e r i v e d from t h e r e a d i n g s of t h e two r a d i o m e t e r s a t d i f f e r e n t d i s t a n c e s from, b u t on t h e s a m e side

o f , t h e b u i l d i n g . I n one c a s e ( t h e s c h o o l ) t h e agreement i s

very poor.

mis

r e s u l t s mainly from t h e f a c t t h a t t h e windows of t h e school annex made a s u b s t a n t i a l c o n t r i b u t i o n t o t h e o o n f i g u r a t i o n f a c t o r f o r t h e more d i s t a n t radiometer b u t n o t f o r t h e n e a r e r . At t h e time when t h e r a d i a t i o n from t h e main body of t h e b u i l d i n g was a maximum t h e f i r e i n t h e annex was

n o t f u l l y developed. The v a l u e of

I/F

r e f e x r i n g t o t h e more d i s t a n t r a d i o m e t e r i s t h u s much lower t h a n f o r the _{n e a r e r}

one.

The m a x i m u m v a l u e s o f I/F f o r houses Nos. 4 and 7

a r e of t h e same o r d e r , a s a r e t h o s e f o r houses ITos. 3 and

5.

I t would t h e r e f o r e seem t h a t t h e use of clapboard e x t e r i o r oladding on a house does n o t a p p r e c i a b l y i n c r e a s e t h e h a z a r d

it p r e s e n t s t o its neighbours. It m i l l be seen t h a t where a house i s l i n e d throughout w i t h a h i g h l y combustible m a t e r i a l ,

a s in t h e cases of houses t h r e e and f i v e , v a l u e s of I/F

of about 37 cal/cm2/sec can be obtained. iahere t h e l i n i n g s a r e incornbustible a s i n t h e c a s e of houses Nos. 4 and

7

and

the _two_{l a r g e r b u i l d i n g s t h e maximum l e v e l s are a b o u t h a l f}

(10)

ma I11 W I I U M RADIATIOH INTENSITIES Building and Burn No. 2 3 4 5 E x t e r i o r Cladding Brick Brick Clapboard ( b r i c k i n f i l l i n g t o timber frame) Cla2board (on cedar s h i n g l e s ) I n t e r i o r Lining Downstairs: f i b r e b o a r d ( w a l l s & c e i l i n g s ) except f o r plj-wood wainscot i n k i t c h e n U p s t a i r s : p l a s t e r Fibreboard P l a s t e r - Pressed paper

.

I n t e n s i t y ( I ) cal/cm2/sec 0.47 0.18 0.08 1.25 >0.18 0.46 0.56 0.17 0.46 1.05 0.32 0. 35 P l a s t e r , wooden 201 leeward c e i l i n g and 40' leeward 7-8 mph waingcot 20 1 windward 0.3 >0.41 0.42 0.9 0.38 0.08 0.83 0.17 >0.5 Radiometer Location 15' leeward 30' leeward 151 windward 151 leeward 30' leeward 151 windward 20' leeward 40' l e e n a r d 201 windward 201 leeward 401 leeward 201 s i d e 7 8 School P Conf'igu- r a t i o n F a c t o r of Openings 0.05 0.016 0.04 0 034 0.013 0.034 0.032 0.011 0.028 0.027 0.008 0.012 Wind Speed 4-5 mph 13-14 m p h 11-12 mph 10-14 mph I/Y cal/cm2/sec 9 11 2 3 7 >14 14

-

1 8 1 5 16 37 40 29 0.075 0.031 0.075 0.058 0.018 0.044 0 ₀₄₉ 0.019 0.088 Brick Brick 1 2 >13 6 1 6 21 2 17 9

>

6 = a s t e r P l a s t e r , wooden c e i l i n g 151 leeward 30' leeward 15' windvrard 201 e a s t 40' e a s t 201 west 1 3 mph v e r y low

(11)

2

House No. 2 gave a maxiaum value of o n l y 11 cal/crn /sec a l t h o u g h i t i n c l u d e d f i b r e b o a r d and plywood l i n i n g s downstairs. It i s thought t l i a t t h i s was due p a r t l y t o t h e f a c t t h a t t h e u p s t a i r s l i n i n g s were i n c o u b u s t i b l e and p a r t l y t o t h e low v e l o c i t y of t h e p r e v a i l i n g wind, Induced v e n t i l a t i o n r a t e measurements

( 3 ) ,

and t h e o r e t i c a l c o n s i d e r a t i o n s i n d i c a t e d t h a t t h e i n l e t v e l o c i t i e s i n a dwelling f i r e d i d n o t u s u a l l y exceed

7

mph, a s l o n g as t h e r o o f remained i n t a c t . Ambient wind v e l o c i t i e s of t h e o r d e r of 1 0 t o 14 rnph a s p r e v a i l e d i n

c a s e s of burns 3, 4 ,

5 ,

and

7 ,

i n c l u s i v e , could t h e r e f o r e have had a s u b s t a n t i a l e f f e c t on t h e r a t e of burning,

Before t h e r e s u l t s of t h e s e measurements can be a p p l i e d t o t h e q u e s t i o n of t h e s e p a r a t i o n o f b u i l d i n g s t h e p e r m i s s i b l e l e v e l s of r a d i a t i o n a t a n exposed b u i l d i n g must be d i s c u s s e d .

The most l i k e l y m a t e r i a l t o be exposed i s t i m b e r and s i n c e , i n f a c t , t h e minimum i n t e n s i t i e s t h a t w i l l cause t h e i g n i t i o n of most common m a t e r i a l s a r e of t h e same o r d e r it i s

s u f f i c i e n t t o l i s t t h o s e r e l a t i n g t o timber ( 8 ) , ( s e e % b l e I V ) .

I n t e r p r e t a t i o n of R e s u l t s

It i s u s u a l i n a b u i l d i n g f i r e f o r a l a r g e number of s p a r k s and f l y i n g brands t o be d i s c h a r g e d and t h e s e a r e capable of producing t h e p i l o t i g n i t i o n of s u i t a b l y i r r a d i a t e d m a t e r i a l s .

! h e O t t a w a & f e l l i n g house f i r e ( 4 ) i s a p r a c t i c a l example i n which it was c o n c l u s i v e l y demonstrated t h a t p i l o t i g n i t i o n was

t h e mechanism by vihich f i r e s p r e a d t o t h e neighbouring house. Considering Table IV, t h e s e p a r a t i o n betvieen b u i l d i n g s

s h o u l d t h e r e f o r e be based on t h e lovrer of t h e two i n t e n s i t i e s s p e c i f i e d . I f , i n a d d i t i o n , from t h e r e s u l t s of t h e S t .

Lawrence b u r n s , we t a k e 37 cal/cm2/sec a s t h e maximum v a l u e of I/F l i k e l y t o be encountered a b u i l d i n g i n c l u d e s a s u b s t a n t i a l p r o p o r t i o n of combustible l i n i n g m a t e r i a l s t h e n w e o b t a i n a v a l u e of 0.008 f o r t h e p e m i i s s i b l e upper l i m i t of t h e c o n f i g u r a t i o n f a c t o r w i t h r e s p e c t t o t h i s c l a s s of b u i l d i n g , Using t h e r e s u l t t h a t t h e r a d i a t i o n l e v e l s from b u i l d i n g s w i t h o u t combustible l i n i n g s a p p e a r t o be lower by a f a c t o r of 2 , tlie p e r m i s s i b l e upper l i m i t w i t h r e s p e c t t o t h i s c l a s s of b u i l d i n g becomes 0,016. 0.3 _cal/crn2/sec _{P i l o t i g n i t i o n ( w i t h a n i g n i t i n g}

source i n tl!e gas stream) M I N I F m INTEPIJSITIES FOR I G r J I T I O N

--

-

I n t e n s i t y . 0.8 cal/cm2/sec Mechanism of I g n i t i o n Spontaneous i g n i t i o n

(12)

A s a _{b a s i s f o r a t a b l e of s e p a r a t i o n s t h e s e two v a l u e s}

1 are

f a r 200 low t o be economically p r a c t i o a l . They a r e a l s o

very much lower t h a n t h e c r i t i c a l v a l u e s c a l c u l a t e d f o r t h e

p r a c t i c a l examples quoted. This f a c t alone suggests t h a t h i g h e r v a l u e s would be accoptable. F u r t h e r examination of t h e S t . Lawrence r e s u l t s shows t h a t t h e high l e v e l s of r a d i a - t i o n r e f e r r e d

t o

were only a t t a i n e d between 16 and

35

minutes

from t h e s t a r t of t h e f i r e , although evidence of t h e f i r e , e.g., smoke, was v i s i b l e from o u t s i d e w i t h i n a few minutes of t h e onset. Had such f i r e s occurred i n p r a c t i c e a f i r e department appliance would almost c e r t a i n l y have been i n attendance by t h e time r a d i a t i o n had reached i t s maximum. Under t h e s e circumstances

it

i s probable t h a t t h e r a d i a t i o n l e v e l s would never have been so high and i n any event t h e spread of f i r e by r a d i a t i o n a t t h i s time would have been prevented by t h e w e t t i n g down of exposed combustibles.

A b u i l d i n g code could t h e r e f o r e be considered accep- t a b l e i f i t almost eliminated t h e spread of f i r e by r a d i a t i o n u p t o t h i s time. ! b e l e v e l s of r a d i a t i o n up t o 16 minutes a f t e r t h e s t a r t of t h e f i r e a r e i n f a c t l e s s t h a n t h e maximum v a l u e s obtained by a f a c t o r of about 4 except i n t h e case of house No.

5

where

$

t h e maximum value was reached i n 1 0 t o

11 minutes. The w a l l s and c e i l i n g s of t h i s house were

l i n e d w i t h pressed paperboard. If, on econolnic grounds,

a b u i l d i n g code w i l l allow some element of r i s k t h e n con- f i g u r a t i o n f a c t o r s of 0.07 and 0.035 should be accepted,

based on t h e lower v a l u e s of r a d i a t i o n l e v e l a l r e a d y discussed. The value 0.07 r e l a t e s t o t h e most commonly occurring occupancy and t h o lower value of .035 need only be invoked i n t h e c a s e s of b u i l d i n g s which because of s u b s t a n t i a l q u a n t i t i e s of corn- b u s t i b l e w a l l l i n i n g s o r f o r o t h e r reasons a r e l i k e l y t o produce h i g h r a d i a t i o n i n t e n s i t i e s

.

While t h e St. Lawrence experiments imply t h a t t h e c o n f i g u r a t i o n f a c t o r v a l u e s suggested above a r e t o o h i g h t o give 100 p e r c e n t s a f e t y , t h e o t h e r examples quoted, where o f

course f i r e f i g h t i n g was c a r r i e d o u t , suggest t h a t s e p a r a t i o n s based on such v a l u e s would e a s i l y have eliminated t h e spread of f i r e i n t h e s e cases. Thus i n t h e case of t h e Winnipeg c o n f l a g r a t i o n t h e Time Building included a s u b s t a n t i a l number of combustible p a r t i t i o n s b u t t h e

T.

Eaton Building d i d n o t become involved u n t i l t h e c o n f i g u r a t i o n f a c t o r r o s e from 0.05 t o 0.1 owing t o c o l l a p s e of a w a l l . Bevan and Webster

reco~nmend a s i n g l e value of 0.056 b u t with t h e a d d i t i o n a l d a t a on r a d i a t i o n l e v e l s now a v a i l a b l e i t would be d e s i r a b l e t o economize on space s e p a r a t i o n by t a k i n g advantage of t h e f i n d i n g -that t h e r a d i a t i o n l e v e l s from b u i l d i n g s w i t h incom- b u s t i b l e l i n i n g s a r e lower than t h o s e from b u i l d i n g s with com- b u s t i b l e l i n i n g s .

(13)

Implementation of R e s u l t s

The main o b s t a c l e that must be overcome i n a p p l y i n g t h e p r i n c i p l e of a l i m i t i n g c o n f i g u r a t i o n f a c t o r t o t h e f o r m u l a t i o n of

a

b u i l d i n g code governing s p a t i a l s e p a r a t i o n

i s

t h a t t h e concept of a c o n f i g u r a t i o n f a c t o r , as d i s c u s s e d s o f a r , r e l a t e s t o t h e s e p a r a t i o n of b u i l d i n g s . The space s e p a r a t i o n which

it

i s customary t o d i s c u s s i n a b u i l d i n g code, on t h e o t h e r hand,

i s

t h e s e p a r a t i o n between a b u i l d i n g and t h e boundary of t h e l o t on which it

i s

e r e c t e d . It i s d i f f i c u l t t o conceive of any o t h e r d e f i n i t i o n of s p a t i a l

s e p a r a t i o n which could be i n c l u d e d i n

a

code i n such a way as t o be c a p a b l e of r a t i o n a l implementation.

It i s probable t h a t this i n c o m p a t i b i l i t y w i l l always e x i s t b u t i t need n o t p r e c l u d e t h e a p p l i c a t i o n of t h e configura- t i o n f a c t o r t o t h e f o r m u l a t i o n of a s e p a r a t i o n code. 5 e most obvious way of d e f i n i n g a d i s t a n c e from a boundary when t h e

d i s t a n c e c a l c u l a t e d

i s

t h a t which should e x i s t between b u i l d i n g s i s t o h a l v e t h e c a l c u l a t e d v a l u e . Where i d e n t i c a l b u i l d i n g s a r e t o be e r e c t e d on e i t h e r s i d e of

a

boundary no i n c o n s i s t e n c y a r i s e s and t h e same v a l u e of s e p a r a t i o n of b u i l d i n g s

i s

a r r i v e d a t whiohever way t h e c a l c u l a t i o n i s made, Where, f o r

, example, one b u i l d i n g

i s

v e r y l a r g e and a n o t h e r v e r y small t h i s

!

i s

n o t t h e c a s e . For a l a r g e b u i l d i n g , c o n f i g u r a t i o n f a c t o r i _{c o n s i d e r a t i o n s might g i v e t h e r e s u l t}_that_{t h e n e a r e s t a d j a c e n t}

I b u i l d i n g should be a t l e a s t 80 f t away. lZle v a l u e d e r i v e d

1

from a t a b l e r e f e r r i n g t o s e p a r a t i o n s from t h e l o t l i n e would t h u s be

40

f t , For a small d w e l l i n g t h e corresponding

d i s t a n c e s might be 1 5 f t and 7 f t 6 i n . r e s p e c t i v e l y . On t h e b a s i s of a code requirement r e l a t i n g t o d i s t a n c e s from l o t b o u n d a r i e s t h e s e p a r a t i o n between t h e s e two b u i l d i n g s , were t h e y a d j a c e n t , would t h e n be 47 f t 6 i n , W i t h t h i s arrangement t h e l a r g e r b u i l d i n g would be i n no danger a s a

r e s u l t of a f i r e i n t h e d w e l l i n g , b u t i n t h e e v e n t of a f i r e

I

i n t h e l a r g e r b u i l d i n g t h e d w e l l i n g might w e l l be i g n i t e d .

I

For

a

v a r i e t y of r e a s o n s t h i s i n c o n s i s t e n c y should be a c c e p t e d . F i r s t l y , i t i s d i f f i c u l t t o conceive of any o t h e r - w i s e r a t i o n a l code r e q u i r e m e n t s which would e l i m i n a t e

it.

Secondly, i n any one a r e a of a c i t y one g e n e r a l l y f i n d s b u i l d i n g s of a similar n a t u r e r a t h e r t h a n , f o r example, a sequence of f a c t o r i e s w i t h d w e l l i n g houses i n t e r s p e r s e d . The s i t u a t i o n d e s c r i b e d w i l l t h e r e f o r e o n l y a r i s e a t such l o c a t i o n s a s t h e o u t s k i r t s of f a c t o r y a r e a s . fIlhirdly,

it

w i l l be n o t i c e d t h a t

it

i s t h e s m a l l e r b u i l d i n g t h a t s u f f e r s t h e h i g h e r r i s k . The r e s u l t of a c c e p t i n g t h e i n c o n s i s t e n c y w i l l t h e r e f o r e be t h a t when c e r t a i n l a r g e b u i l d i n g s on t h e o u t s k i r t s of f a c t o r y a r e a s a r e d e s t r o y e d by f i r e a small

number of d w e l l i n g s , probably n o t exceeding one, w i l l a l s o be i n v o l v e d i n t h e f i r e . This s t a t e of a f f a i r s of course

(14)

Since s e p a r a t i o n requirements a r e dependent on per- oentage window opening, d i s s i m i l a r i t i e s i n t h i s r e s p e c t between a d j a c e n t b u i l d i n g s could a l s o be d i s t u r b i n g ,

!be r e l a t i o n s which have been derived between t h e s e p a r a t i o n , width and h e i g h t

of

b u i l d i n g s , and percentage window opening a r e given i n Tables V and V I . Table V r e f e r s t o p a r t i c u l a r l y hazardous c o n d i t i o n s which m i g h t

include t h e c a s e s (a) where more t h a n 25 per c e n t of t h e

w a l l and c e i l i n g l i n i n g s a r e combustible, ( b ) where t h e f i r e l o a d i s h i g h , o r ( c ) where t h e c o n t e n t s of a b u i l d i n g a r e p a r t i c u l a r l y flammable. The c a l c u l a t i o n s have been based on a configuration f a c t o r of approximately 0.035 with a f u r t h e r

3 f t

6 i n . added t o each r e s u l t i n g d i s t a n c e of s e p a r a t i o n . The e f f e c t of t h i s a d d i t i o n i s t h a t t h e s h o r t e r : d i s t a n c e s a r e g r e a t e r t h a n t h e y m i g h t have b e e n i f a pure conZiguration f a c t o r b a s i s had been adopted. This policy h a s been adopted f i r s t l y because t h e h o r i z o n t a l p r o j e c t i o n s of flames

from

windows w i l l n o t f o l l o ~ v a l i n e a r geometrical r e l a t i o n s h i p .and secondly because f i r e f i g h t i n g becomes p r o g r e s s i v e l y

more d i f f i c u l t with r e d u c t i o n i n space s e p a r a t i o n .

Table

VI r e l a t e s t o a l l o t h e r c o n d i t i o n s n o t covered

by Table V and hence w i l l be t h e more f r e q u e n t l y used. The c n l c u l a t i o n s have been based on a c o n f i g u r a t i o n f a c t o r of approximately O,O7 with a f u r t h e r 2 f t 6 i n . added t o each r e s u l t i n g d i s t a n c e of s e p a r a t i o n .

Both t h e h e i g h t s and t h e widths l i s t e d i n t h e t a b l e s r e f e r t o f i r e r e s i s t i n g compartments. Pox t h e purpose of implementing t h i s t a b l e a compartment should be considered f i r e r e s i s t i n g i f i t s bounding w a l l s and c e i l i n g s and t h e c e i l i n g of t h e s t o r y beneath meet t h e requirements based on f i r e l o a d given elsewhere i n t h e code.

I n applying t h e t a b l e s a note i s necessary a s t o t h e

adoption of a value of percentage window opening. The t a b l e s

r e l a t e t o uniformly d i s t r i b u t e d openings and cases may t h u s a r i s e where t h e value adopted i n u s i n g t h e t a b l e s should r e f e r t o a very l o c a l i z e d a r e a where t h e window d e n s i t y i s high. A

f u r t h e r p o i n t i s t h a t t h e adoption of a value of window opening of l e s s t h a n 100 per c e n t i s only v a l i d where t h e f i r e r e s i s - tance time of t h e remainder of t h e w a l l , from t h e p o i n t of view of p e n e t r a t i o n only, meets t h e requirements based on t h e f i r e load concept given elsewhere i n t h e code.

Where t h i s i s n o t t h e c a s e , then t h e window opening

should be taken as 100 per c e n t even i f , a p p a r e n t l y , t h e r e a r e no openings a t a l l i n t h e w a l l i n question..

(15)

TABLE V

SESPARATIOB FRON LOT LINE: PARTICULARLY HAZARDOUS COITDITIONS Width of dompartment ( f e e t )

-

30' Percentage of Window Openings 100 80 60 40 20 . lo' 29 25.5 22 18.5 1 3 20' 38.5 35 31 26 17.5 44.5 40 35 29 20 49.5 45 39 3 1 5 22 54 48 42 3 4 23.5 58 51.5 44.5 35.5 24.5 62 54.5 47 37 2 5 65.5 58 50 40 26 68 60 52 41 26.5 73.5 65.5 57 44 20 81.5 72 62 48 29.5 89.5 79.5 6 6 51.5 30 Height 30' 47 42.5 37 31 21.5 40'

/

50' 60' 53.5 48 42 3 5 24 60 53.5 47 38.5 26.5 65 58.5 51 42 28.5 70.5 63 55 45 30.5 75 67.5 59 47.5 32 79.5 71.5 62.5 50 3 3 84 75.5 of 40' 53.5 48 42 35 24 ( f e e t 60' 65 58.5 51 42 28.5

---

100 80 60 40 20 100 . 80 60 40 20 100 80 60 40 20 100 80 Compartment 50' 60 53.5 47 38.5 26.5 62 55.5 49 40 28 69 61.5 54 44 31 7 5 67 59 48 33 81 72.5 63.5 51.5 35 86 77.5 67.5 54.5 I 37 91 82 71.5 57.5 38.5 96 86.5 75 67 59 48 3 3 83.5 75 65.5 53.5 36.5 91 82 71 58 40 98 88 76.5 62.5 43 104.5 94 82 66.5 45.5 110.5 99.5 86.5 70 48 116.5 104.5 91 73.5 49.5 127.5 114 99.5 80 53.5 142 127 I10 88 59 163.5 146.5 90' 79.5 71.5 62.5 50 33 32.5 29 25.5 20.5 14 36 32.5 28 22 1 5 38.5 3 4 29.5 2 4 16 41 1 36.5 69 61.5 54 4 4 31 76.5 69 60 49 3 4 83.5 75 65.5 53.5 36.5 81 70.5 57.5 39 96 86 75 61 41.5 101 91 79.5 64 43.5 106.5 96 ) 70' 70.5 63 5 5 45 30.5 100' 84 75.5 65.5 52 34 91 82 71.5 57.5 38.5 101.5 91 79.5 64 43.5 110.5 99.5 86.5 70 48 119 107 93.5 7 6 51.5 127.5 114 99.5 81 55 135.5 121 105.5 86 58.5 142 127 110.5 90 61 155.5 139 120.5 98 66.5 173 155 134 108.5 73 31.5 25 16.5 43 38

2

17 44.5 39.5 34 27 17 46 41 3 5 27.5 17 49.5 44 37 29 17 53 47 39 30.5 17 58 50 41 31 17 7 0' 60

1 ::

83.5 67 45 116.5 104.5 91 7 3 48.5 130 115.5 100 80 57 149 133.5 113 89.5 58 124.5 99 65 80' 75 67.5 59 47.5 32 81 72.5 63.5 51.5 35 90 81 70.5 57.5 39 98 88 76.5 62.5 4 3 105.5 95 82.5 67.5 46 112.5 101 88 72 49 119 107 93.5 76 51.5 125.5 112.5 98 80 54 137 123 107.5 87 58 153 137 119 96 64 176 157.5 96 86.5 75.5 60 40 106.5 96 83.5 67 45 116.5 104.5 91 73.5 49.5 125.5 112.5 98 80 54 134 120 104.5 8 5 57.5 142 127 110.5 90 61 149.5 134 116.5 9 5 6 4 163.5 146.5 127 103.5 69.5 1 8 2 163 141 114.5 77 80' 90' 100' 9. 120' 150' 200'

..

g5.5

1

a2.5 86 77.5 67.5 54.5 37 96 86 75 61 41.5 104.5 94 82 66.5 45.5 112.5 101 88 72 49 120 108 94 76.5 5 2 127.5 114 99.5 81 55 134 120 104.5 85 57.5 147 131.5 114 92.5 62.5

-164 146 127 102.5 68.5 188 160 100 80 60 40 20 100 80 60 40 20 100 80 60 40 20 100 80 60 40 20 100 80 60 40 20 100 80 60 40 20 34 91.5 82 71 5 6 3 6 101 89.5 77.5 60.5 39 115 103 85 66.5 41 135 108.5 71 40 104.5 94 82 6 5 4 3 115.5 103.5 90 70.5 46.5 134 119.5 100 79 50 145 116 77

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TABLE V I

SEPARATION FROM LOT LINE : N O X U L COIJDITIONS Width of Compartment ( f e e t ) Percentage of Window O p e n i ~ s Height 30' 33.5 30 25.5 20 14.5 38 3 4 29.5 2 3 16 41.5 37.5 32.5 1 7 25'5 45 41 35 27.5 18 48.5 43.5 37.5 29.5 1 9 51.5 46 39.5 31 19.5 54.5 48.5 41 32 20 57 50 42.5 33.5 20 61.5 54.5 45.5 36 2 0 67 59.5 49.5 38 21 74 65 53.5 40.5 22.5 . 10' 1 9 1 7 1 4 . 5 1 2 8 . 5 21.5 1 9 . 5 1 6 . 5 1 3 9 24 21 17.5 1 4 9 26 22.5 1 9 14.5 9 28 24 20 l5 9 29 25 2 1 15.5 9 3 0 26 22 1 6 9 30.5 26.5 22.5 1 6 9 3 2 28 22.5 1 6 9 33.5 29 23 16.5 9 3 4 29 1 7 24 9 30' 20' 26.5 24.0 2 . 0 16.5 11.5 30.5 28 24 1 9 12.5 33.5 30 26 21 13.5 37 33 28 22.5 1 4 3 9 35 30 24 14.5 41 37 3 2 25 14.5 43.5 39 32.5 25.5 1 5 45.5 40 33 26 1 5 48.5 42 34.5 27 1 5 53.5 46.5 37 28 1 5 57.5 50.5 40.5 29.5 1 6 o f 40' 38.0 3 4 29.5 23 1 6 43 39 33.5 27 18 48 43.5 37 ::.5 52 47.5 40.5 32.5 21 56 51 43.5 34.5 22 59.5 5 4 46 36.5 23 63 56.5 48 38 2 4 6 6 59 50 39.5 2 4 71.5 64 53.5 4 2 2 5 78.5 69.5 50.5 45.5 26 88 77 64 49.5 28 100 8 0 6 0 40 20 80' 51.5 46 39.5 31 19.5 59.5 5 4 46 23 36.5 67 60 51.5 40.5 26.5 73.5 6 6 56 4 5 29 8 0 7 1 60.5 48.5 3 1 85.5 ,76 64.5 51 33 90.5 80.5 68 54 35 95 84.5 71.5 56.5 36.5 103.5 9 2 78 61.5 38 114.5 1 0 1 86 67.5 41.5 114.5 97.5 7 6 46.5 Compartment 50' 41.5 37.5 32.5 25.5 1 7 48 43.5 37 30 19.5 53.5 48 41 3 3 21.5 59 52.5 45 36 23.5 6 3 56.5 48.5 38.5 2 5 67 60 51.5 40.5 26.5 7 1 63.5 54.5 42.5 27.5 7 4 66.5 56.5 44 28 81 72 61.5 47.5 29 89 79 67 52 31 1 0 0 . 5 1 1 1 87.5 73.5 57 33.5 I 90' 54.5 48.5 41 32.5 20 40' ( f e e t ) 60' 45 41 35 27.5 18 52 47.5 40.5 32.5 21 59 52.5 45 3 6 23.5 64.5 57.5 49.5 39 25.5 69 62 53 42 27.5 73.5 66 56 45 29 78 69.5 59 47 30 82.5 73 62 48.5 31 89.5 79 67.5 53 3 2 99 86.5 73.5 58 34.5 97.5 82.5 64 38 100' 57 50 42.5 33.5 20 100 80 60 40 20 70' 48.5 43.5 37.5 29.5 1 9 5 6 51 43.5 22 34.5 63 56.5 48.5 38.5 25 69 62 53 42 27.5 7 5 66.5 56.5 46 29 8 0 7 1 60.5 48.5 3 1 84.5 75.5 63.5 51 32.5 89 79.5 67 53 3 4 97 8 6 73 57.5 35 107.5 94.5 8 0 6 3 38 1 2 0 . 5 1 2 9 106.5 90.5 7 0 42.5 50' 63 38 24 7 1 1 0 0 8 0 60 63.5 54.5 42.5 27.5 7 8 69.5 59 47 30 84.5 75.5 63.5 51 32.5 90.5 80.5 68 5 4 3 5 95.5 85 7 2 57 37 100.5 89.5 75.5 60 38.5 109.5 97.5 8 3 65.5 41 121.5 107.5 9 2 72 44.5 137 122.5 104.5 81.5 50 66.5 56.5 44 28 82.5 73 62 48.5 3 1 89 79.5 67 53 34 95 84.5 71.5 56.5 36.5 100.5 89.5 75.5 60 38.5 106 94 79.5 63.5 40.5 115 103 87 69.5 44 128 114 97 76.5 47.5 145 130.5 111.5 86 57.5 40 20 60' 1 0 0 8 0 60 40 20 70' I 80' I 1 0 0 80 60 40 20 100 8 0 60 20 100 8 0 90' 100' 120' 150' 200'

18

20 1 0 0 8 0 60 40 20 1 0 0 80 60 40 20 1 0 0 8 0 60 40 20 100 8 0 60 40 20

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S p e c i a l Cases

If t h e e x t e r i o r w a l l of a p r o j e c t e d b u i l d i n g

i s

n o t t o be p a r a l l e l Nth t h e l o t boundary t h e n t h e p o s s i b i l i t y o f r e l a x i n g t h e s e p a r a t i o n requirement a t t h e c a n e r of t h e b u i l d i n g

m u s t

be considered. Using t h e same b a s i s of c a l -

c u l a t i o n a s p r e v i o u s l y t h e d i s t a n c e s r e l a t e d t o t h e c o r n e r s of b u i l d i n g s prove t o be, i n g e n e r a l , between 65 and

95

p e r c e n t of t h o s e l i s t e d i n t h e t a b l e s . A s f i r e f i g h t i n g n e a r t o t h e c o r n e r o f a b u i l d i n g i s e a s i e r some r e l a x a t i o n

i s

d e s i r - a b l e and a f a c t o r of 80 p e r c e n t i s suggested. The r e s u l t i n g l i m i t i n g boundary l o c a t i o n i s i l l u s t r a t e d i n Fig.

3.

M g u r e

3

a l s o g i v e s t h e c o n d i t i o n s r e q u i r e d beyond t h e extreme c o r n e r s of t h e b u i l d i n g . I n t h e c a s e i l l u s t r a t e d on t h e l e f t of Fig.

3,

it mrLght be consid.ered some h a r d s h i p t h a t t h e boundary may n o t l i e i n a l i n e w i t h t h e i m p e r f o r a t e f i r e r e s i s t a n t w a l l . This r e s t r i c t i o n can be e l i m i n a t e d simply by ensu.ring t h a t t h e r e a r e no window o ~ e n i n g s i n t h e s e c t i o n

CE of t h e a d j o i n i n g w a l l . So f a r as s e p a r a t i o n r e q u i r e m e n t s a r e concerned t h a t w a l l t h e n t e r m i n a t e s a t E and t h e boundary r e s t r i c t i o n would be a s i l l u s t r a t e d by t h e d o t t e d l i n e EBP

(Fig. 3 ) . It might o f t e n b e d e s i r a b l e t o a p p l y a similar argument t o t h e case. i l l u s t r a t e d on t h e r i g h t of t h i s Figure.

The e x t e r i o r w a l l o f a b u i l d i n g i s o f t e n i r r e g u l a r i n shape a s i n t h e two c a s e s i l l u s t r a t e d i n Fig.

4.

In such c a s e s t h e p r e l i m i n a r y c o n s i d e r a t i o n s should be r e f e r r e d t o a l i n e j o i n i n g t h e e x t r e m i t i e s of t h e e x t e r i o r w a l l . Where t h e b u i l d i n g i s e n t i r e l y c o n t a i n e d w i t h i n t h i s l i n e no f u r t h e r s t e p s a r e r e q u i r e d , f o r s o f a r a s l e v e l s of r a d i a t i o n a r e

concerned t h e i r r e g u l a r e x t e r i o r w a l l i s e x a c t l y r e p r e s e n t e d by a n imaginary w a l l having t h e same percentage window openings and l o c a t e d on t h e l i n e r e f e r r e d t o . Where a p o r t i o n of t h e b u i l d i n g p r o j e c t s beyond t h i s l i n e t h e r e p r e s e n t a t i o n can break down under c e r t a i n c o n d i t i o n s . A p r e c i s e d e s c r i p t i o n of t h e s e c o n d i t i o n s i s n o t c a l l e d f o r i n t h i s r e p o r t b u t h a s been d i s c u s s e d elsewhere

(9).

I t i s s u f f i c i e n t t h a t t h e

s e p a r a t i o n r e q u i r e m e n t s w i l l be approximately f u l f i l l e d i f

t h e l o t boundary f o l l o w s t h e o u t e r l i m i t of ( a ) t h e boundary

a s c a l c u l a t e d above and ( b ) a boundary r e f e r r e d s o l e l y t o t h e p r o j e c t i n g p o r t i o n s of t h e b u i l d i n g . Such composite l o t

b o u n d a r i e s a r e i l l u s t r a t e d i n F i e . 4.

Conclusion

Development o f t h e g e p a r a t i o n a s p e c t o f t h e N a t i o n a l B u i l d i n g Code by t h e i n c l u s i o n of t h e dimensions of a n e x t e r i o r

w a l l a s a n independent v a r i a b l e w i l l l e a d t o a more economic u s e o f space a s a means of r e d u c i n g t h e s p r e a d of f i r e .

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Acknowledgment

The c o n f i g u r a t i o n f a c t o r o a l c u l a t i o n s i n v o l v e d i n t h e d e r i v a t i o n of Tables V and

VI

were c a r r i e d o u t by P. Huot of t h e F i r e S e c t i o n , D i v i s i o n of B u i l d i n g Research, N a t i o n a l Research Council.

References

(1) Bevan, R.C., and C.T. Webster. I n v e s t i g a t i o n s on B u i l d i n g F i r e s , P a r t 111, R a d i a t i o n from B u i l d i n g F i r e s .

Mational B u i l d i n g S t u d i e s , Technical Paper No,

5,

London, -England, H. IY!. S

,

0. 1950.

( 2 ) Galbreath,

M.

Note on Lanark F i r e ( i n pr ? p a r a t i o n ) . ( 3 ) S h o r t e r G.W., and J.H. McGuire. Summary Report of

S t , Lawrence Burns, ( t o be p u b l i s h e d a s DBR I n t e r n a l Report No, 1 5 8 ) .

( 4 )

McGuire,

J.H.,

and G.W. S h o r t e r . An Example o f t h e

Spread o f F i r e by R a d i a t i o n . N a t i o n a l Research Council, M v i s i o n of B u i l d i n g Research, DBR I n t e r n a l Report

No. 145. 1958.

( 5 )

N a t i o n a l B u i l d i n g Code of Canada ( 1 9 5 3 ) , P a r t 3: Use and Occupancy. N a t i o n a l Research Council, A s s o c i a t e

Committee on. t h e N a t i o n a l B u i l d i n g Code.

( 6 ) S h o r t e r , G, W.

,

and C,G. B u r n e t t . F i r e I n v e s t i g a t i o n s

by t h e F i r e Research S e c t i o n , 1950-1954. N a t i o n a l Research Council, D i v i s i o n of B u i l d i n g Research,

DBR

I n t e r n a l Report No.

78.

March 1956.

(7

) Stephenson, D. G. Radiant Temperature of Openings, S t . Lawrence Burns. ( t o be p u b l i s h e d a s DBR I n t e r n a l Report No. 1 5 6 . )

(8) Lawson, D,I., and

D.L,

Simms. The I g n i t i o n o f Wood by R a d i a t i o n . B r i t . J o u r . Appl. Phys., Vole 3 , P.288-292, September 1952.

(9)

McGuire, J.H. Heat T r a n s f e r by R a d i a t i o n ,

Fire

Research

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R A D I A T I N G SURFACES R A D I A T I N G SURFACES \

',

6

FT \ \ \ \ \ \ R E C E I V I N G

23

R E C E I V I N G

1

E L E M E N T E L E M E N T

F I G U R E I

.

G E O M E T R I C A L R E L A T I O N S H I P S

(20)

133'

P O I N T AT \qHICH C O N F I G U R A T I O N FACTORS EVALUATEP F I G U R E 2 P L A N OF AREA I N V O L V E D I N WINNIPEG F I R E

(21)

-

FIR& SESISTANT \\IALI

NO O P L N l N G S

+

_I I

D

1

i

---_

I

----t

_- ;r(C

d

=

Dl

0 s

D2

\VH1CH WEq IS T H E L A q G L q FIGURE

3

BOUNDARY C O N D I T I O N S AT THE C O R N E R S OF BULLDLNGS

I

D2

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B U I L D I N G I / / / BUILDING / L I M I T S F I G U R E 4 B O U N D A R Y C O N D I T I O N S F O R I R R E G U L A R L Y S H A P E D B U I L D I N G S

(23)

APPENDIX

A

!PHE COXFIGURATION FACTOR CONCEPT

5 e r a d i a t i o n l e v e l I a t a d i s t a n c e from a source e m i t t i n g r a d i a t i o n a t a l e v e l I i s r e l a t e d t o I. by t h e e x p r e s s i o n I = I. x F, where F

fs

t h e c o n f i g u r a t i o n f a c t o r * and h a s t h e property t h a t it i s dependent s o l e l y on t h e geo- m e t r i c a l r e l a t i o n s h i p of r e c e i v e r and source.

The p r a c t i c a l a p p l i c a t i o n of t h e above expression t o b u i l d i n g f i r e s i s complicated by t h e f a c t t h a t very l i t t l e d a t a a r e a v a i l a b l e on t h e r a d i a t i n g n a t u r e of the flames emanating from burning b u i l d i n g s . Even i f information were a v a i l a b l e

it

would be d i f f i c u l t t o apply s i n c e t h e e m i s s i v i t y of flames i s a v a r i a b l e and hence a n i n t e g r a l form of t h e above expression i s r e q u i r e d .

The most simple method of overcoming t h i s d i f f i c u l t y i s t o r e p r e s e n t t h e r a d i a t i o n coriditions a t t h e s i d e of a b u i l d i n g by a l e v e l of r a d i a t i o n h i g h e r t h a n i s found i n p r a c t i c e b u t emanating only from t h e window openings. An

assumption of t h i s n a t u r e must, i n f a c t , be accepted i m p l i c i t l y

i f a b u i l d i n g code

i s

t o d i s c u s s percentage window openings i n s t e a d of t h e p r e c i s e geometry of openings i n a b u i l d i n g facade. Even i f percentage window opening i s maintained c o n s t a n t , v a r i a t i o n i n t h e geometry of window openings w i l l

a f f e c t t h e l e v e l s of r a d i a t i o n a t a d i s t a n c e from a building. I n g e n e r a l , however, t h e e x t e n t of t h e v a r i a t i o n can be

neglected.

On t h e assumption t h a t only t h e windows a r e r a d i a t i n g t h e r e l a t i o n s h i p s between i n t e n s i t i e s of r a d i a t i o n a t v a r i o u s p o i n t s a r e given q u i t e simply i n terms of t h e a p p r o p r i a t e c o n f i g u r a t i o n f a c t o r s . If I be t h e measured r a d i a t i o n l e v e l a t some p o i n t P away from a burning b u i l d i n g t h e n on t h e asswnption t h a t only t h e windows a r e r a d i a t i n g , b u t a t a

r a d i a t i o n l e v e l Iw which w i l l produce a r a d i a t i o n l e v e l IP a t t h e p o i n t

P,

t h e n

i s t h e c o n f i g u r a t i o n f a c t o r of t h e window a r e a

w i t h r e s p e o t t o a n elemental r e c e i v i n g a r e a a t p o i n t P and depends only upon t h e geometrical r e l a t i o n s h i p of t h e window a r e a and t h e elemental a r e a a t

P.

-- -- -

9 The c o n f i g u r a t i o n f a c t o r of a r a d i a t i n g a r e a w i t h r e s p e c t

t o a n elemental r e c e i v i n g a r e a may be defined a s t h e r a t i o of t h e i n t e n s i t y of r a d i a t i o n a t t h e r e c e i v i n g element t o t h e i n t e n s i t y n e a r t o t h e r a d i a t o r . Its value i s dependent s o l e l y on t h e geometrical r e l a t i o n s h i p between t h e r a d i a t o r and t h e r e c e i v i n g element and may l i e between zero and u n i t y .

(24)

Now s i n c e IW i s n o t a r e a l i n t e n s i t y , it may be p r e f e r a b l e

t o

r e f e r t o i t simply a s t h e r a t i o 1p/FpW o r

aimply

I/P, i t being understood t h a t F i n this

oaae

i s

t h e c o n f i g u r a t i o n f a c t o r r e l a t i n g t h e window

area t o

t h e elemental a r e a a t t h e p o i n t a t which t h e measured

intensity was

I.

The r e a l o b j e c t of t h i s procedure i s t h a t it now permits a n estimate t o be made of t h e r a d i a t i o n l e v e l a t any p o i n t Q from t h e r a d i a t i o n l e v e l Ip measured a t

P.

b u t

Iw

was given by

I ~ / F ~

F ~ w

i n t h i s case i s t h e c o n f i g u r a t i o n f a c t o r of t h e

window a r e a with r e s p e c t t o a n elemental r e c e i v i n g a r e a a t

p o i n t Q.

Now, i f a number of measured o r estimated r a d i a t i o n l e v e l s corresponding t o I a r e k n o m f o r a number of d i f f e r e n t c a s e s , it i s p o s s i b l e , usfng t h e approach o u t l i n e d , t o compare t h e s e by c a l c u l a t i n g t h e e q u i v a l e n t window r a d i a t i o n l e v e l s , I/F i n each case. A value of I/F r e p r e s e n t a t i v e of a par- t i c u l a r f i r e s i t u a t i o n may then be s e l e c t e d . I n considering t h e p o s s i b i l i t y t h a t a f i r e i n one b u i l d i n g w i l l i g n i t e a n o t h e r by r a d i a t i o n , and having e s t i m a t e d an e q u i v a l e n t window r a d i a t i o n l e v e l f o r burning b u i l d i n g s and e s t a b l i s h e d t h e maximum t o l e r a b l e r a d i a t i o n l e v e l a t t h e b u i l d i n g t o be p r o t e c t e d , it becomes p o s s i b l e t o r e f e r t o l i m i t i n g v a l u e s of P f o r which t h e r a d i a t i o n l e v e l s a % t h e b u i l d i n g t o be p r o t e c t e d w i l l be k e p t w i t h i n t h e d e s i r e d limits. P i n t h i s case i s t h e c o n f i g u r a t i o n f a c t o r r e l a t i n g window a r e a s of t h e compartment on f i r e t o t h e exposed

s u r -

f a c e of t h e b u i l d i n g t o be p r o t e c t e d . This t h e n , i n e f f e c t , means t h a t t h e l e v e l of r a d i a t i o n imposed on one b u i l d i n g can be described i n terms of t h e s i z e , arrangement, and geometry of t h e windows of t h e compartment on f i r e a s r e l a t e d t o t h e s u r f a c e s t o be p r o t e c t e d .

In

t h e work described i n t h i s r e p o r t , it h a s been assumed t h a t t h e r a d i a t i o n from t h e flames and openings a t t h e s i d e of a b u i l d i n g w i l l be l i n e a r l y r e l a t e d t o t h e a r e a

of t h e openings. 'Phis approximation may tend t o break down

where l a r g e percentage window openings a r e considered and t h e p r e d i c t e d l e v e l s of r a d i a t i o n may t h e n be exaggerated f o r two reasons: