Transcript Eurocode 1: Actions on structures

Eurocode 1: Actions
on structures –
Part 1–2: General actions –
Actions on structures exposed to fire
Annex E (informative)
→ Fire load densities
Part of the One Stop Shop program
Introduction
• Fire load density evaluation
• FLD used is a “design value” based on
– Measurements or
– Values given in national regulations
• Determined by
– Classification of occupancies and/or
– Individual project analysis
Design value
• The design value of the fire load:
q f ,d  q f ,k  m   q1   q 2   n
Characteristic fire
load density per unit
floor area
Combustion
factor
Fire activation risk
factors for
Compartment
size
and Type of
occupancy
Fire-fighting
measures risk
factor
Determination of fire
load densities
• Fire load density needs to be determined
taking into account
– Type of building / occupancy
– Protected fire loads
– Calorific value of fuel
• This process is used to determine the
value of q f ,k for previous equation
q f ,d  q f ,k  m   q1   q 2   n
q f ,k from occupancies
• For a large number of buildings, e.g.
offices, residencies, hotels, and the paper
industry,
 q 2  1.0
In which case, Table E.4 may be used to
determine the value of q f , k
• Separate fire load densities within the building
should be added to the tabular value if
necessary
q f ,d  q f ,k  m   q1   q 2   n
q f ,k from basic principles
• To obtain
q f ,k  Q fi,k / A
Compartment
area
we must obtain a value for
Q fi,k   M k ,i  H ui  i  Q fi,k ,i
Characteristic
fire load
Net calorific
value
Optional factor
for protected
loads
Amount of
combustible material
q f ,d  q f ,k  m   q1   q 2   n
Combustion factor
• Having determined a value for q f ,k we
next need a value for m - the combustion
factor
• The value of 0.8 is taken for cases mainly
consisting of cellulosic fuels
• In other cases the combustion behaviour should be
looked at as a function of occupancy and type of fire load
q f ,d  q f ,k  m   q1   q 2   n
Fire activation risk factors
1. Due to size of compartment:
2. Due to type of occupancy:
 q1
 q2
The factors vary from just under 1.0 to just over 2.0 –
the particular value used is taken from Table E.1
included in the Annex
q f ,d  q f ,k  m   q1   q 2   n
Fire-fighting measures risk factors
•
This factor is a function of active fire10
fighting measures
 n    n ,i
•
i 1
Takes into account
– Fire suppression systems
– Automatic fire detection and alarm systems
– Manual fire suppression systems
•
The values for the individual factors
i  1  10 are given in Table E.2
q f ,d  q f ,k  m   q1   q 2   n
Worked example
• Work out the design fire load for a 6,500m2
office space, with no additional fuels
present in the space.
– The office is sprinkler protected
– Heat detectors are the only source of A&D
system within the space
– No other special provisions are present apart
from the normal fire-fighting measures
Worked example - workings
q f ,d  q f ,k  m   q1   q 2   n
• From Table E.4, we can see the value of
q f ,k can be taken as 420 MJ/m2
• This value may be taken because the
value of  q 2 is 1.0 (Table E.1)
• The value of
m can be taken as 0.8
• The value of  q1 is 2.0, as it is between
the 5,000 and 10,000m2 brackets (Table
E.1)
Worked example - workings
q f ,d  q f ,k  m   q1   q 2   n
10
 n ,i is therefore
• The value of  n  
i 1
averaged from 0.61, 0.87, and 1.0 which
results in  n having a value of 0.83
Worked example - answer
q f ,d  q f ,k  m   q1   q 2   n
• Putting these values back into the original
equation gives us a design value of the fire
load for our test case scenario highlighted
in the worked example as:
q f ,d  420 0.8  2.0 1.0  0.83
q f ,d  558
MJ/m2