Eurocode 1: Actions
on structures –
Part 1–2: General actions –
Actions on structures exposed to fire
Annex G (informative)
→ Configuration factor
Part of the One Stop Shop program
Introduction
• Measurement of the fraction of the total radiative
heat leaving a given surface that arrives at a
given receiving surface
• The value of the configuration factor depends on
– Size of radiating surface
– Distance between two surfaces
– Relative orientation of surfaces
• “Position” effect and “Shadow” effect
• Calculation of temperatures in external members
Position and Shadow effects
• Position effect
– Radiative heat transfer to an infinitesimal area of
convex member surface is determined by the position
and size of the fire only
• Shadow effect
– Radiative heat transfer to an infinitesimal area of
concave member surface is determined by the
position and size of the fire as well as by the radiation
from other parts of the member
• Combination of position and shadow effects
– Rules for quantifying the shadow effect are given in
material orientated parts of the Eurocodes
External members
• For the calculation of temperatures in external
members, all radiating surfaces assumed
rectangular
– E.g. windows, doors, etc. in compartment walls
• See Annex B – Thermal actions for external
members – the simplified calculation method
• The configuration factor determined in this
Annex is used within Annex B
Configuration factor
Rectangular envelope should first be drawn around
cross-section of member
P
P
P
P
P
P
P
P
The configuration factor  is then determined
for the mid-point P of each face of the rectangle
Configuration factor setup
From point P, there are normally 4 zones visible on
the radiating surface
Receiving surface
a
Radiating surface
2
1
3
x
P
b
4
  1   2   3   4 
Configuration factor setup
Shadowing can result in some zones from not
being visible from point P
Radiating surface
Receiving surface
a
1
b
x
2
P
No contribution is thus taken from these zones and
the configuration factor is taken as   1   2 
Determination of factor
• If the surface receiving is parallel to the radiating
surface
1

2
h
a
s

a

 1  a 2


0.5

b

tan
 1 a2

1

- Height of zone on
radiating surface
- Distance from P to x

b

0.5 
2
1

b



w
b
s

0.5

a

tan
 1  b2

1



0.5 


- Width of zone on
radiating surface
- Distance from P to x
This process is repeated for all visible zones of the
radiating surface – normally 4 for parallel surfaces
Determination of factor
• If the surface receiving is perpendicular to the
radiating surface
1  1
1

tan a  
2
2 
1

b


h
a
s
- Height of zone on
radiating surface
- Distance from P to x

0.5

a

tan
 1  b2

1

w
b
s


0.5 


- Width of zone on
radiating surface
- Distance from P to x
This process is repeated for all visible zones of the
radiating surface
Determination of factor
s
w
• If the surface receiving is
at an angle  to the
radiating surface
2
h
1
1  b cos 
1  1

tan a  
2
2 
1

b
 2b cos 


a
a cos 
2
 sin 2  
0.5
P
x

0.5


a
tan 
 1  b 2  2b cos 

1



0.5 



 b  cos  

 
cos

1 

1
  tan 
 
 tan
 a 2  sin 2  0.5 
 a 2  sin 2  0.5  




 