Abstract
This study is the first relatively broad statistical
survey utilising the statistical data collected in the
national accident database, Pronto. As a result valuable
new information relating to fire risks is obtained and
quantitative methods for fire risk assessment of
buildings are presented. This work is a step forward in
the field of risk-analysis-based fire safety design and
overall a step towards a better understanding of the
anatomy of fires.
The use of statistical information is a good objective
way of attempting to characterise fires. This study
concentrates on ignition frequency, economic fire losses
and fire department operation in the event of
building-fires. Ignition frequency was derived as a
function of total floor area for different building
categories. The analysis showed that the variations of
ignition frequency are dependent on initial floor area
distributions of the buildings hit by fire and at risk.
For engineering design purposes, the generalisation of
the theory starting from the initial floor area
distributions, leading to a sum of two power laws, was
found suitable. The parameters and partial safety
coefficients for the model were estimated for three
building groups. The model is suitable for determining
the ignition frequency of buildings with a total floor
area of between 100 and 20 000 m2.
The elements describing the fire department operation
were analysed on the basis of statistical information. In
the presented approach, the buildings in which fire
safety depends completely on automatic extinguishing
systems can be distinguished from those in which the fire
department is able to arrive at the fire scene early
enough to have a good chance of saving the building. The
most important factor affecting the performance of the
rescue force was found to be the travel time to the fire
scene. Thus, to make the task easier for the fire
department, special attention must be paid to rapid fire
detection and locating of the fire seat. Delays in these
actions lengthen the total response time and reduce
significantly the chances of the fire department
successfully intervening in the progress of the fire.
Economic losses were considered as consequences of the
fires. The analysis showed the dependency of loss and
value-at-risk of the building on the floor area. Clear
local peaks were detected for both the ignition frequency
and fire losses. A more detailed analysis of residential
buildings where the phenomenon was most apparent revealed
that the peaks were located around the floor-area region
where the dominant building type of the building stock,
and thus the compartmentation manner, changed. With small
values of the total floor area of the building, the rise
of the loss was very steep, but levelled off to
substantially slower growth with large values. A natural
explanation for the behaviour is compartmentation. Both
the ignition frequency and the fire losses should
therefore be examined in relation to the size of the
ignition compartment, which would be a significantly more
appropriate descriptor than the total floor area of the
building. Hence, it is essential that the information
becomes available to the Finnish accident database, in
which it is not at the moment included. The analysis
shows that the type of building and compartmentation,
rather than the material of the load-bearing member
itself, was the factor having the greatest effect on the
risk of fire.
The use of the information gathered was demonstrated
through a simple example case in which the fire risk was
assessed using the time-dependent event-tree approach.
This study concentrates on the utilisation of statistics
to collect information and gain an understanding of the
elements affecting fire risks in buildings. Many of the
methods used are well known in other application areas;
the available statistical data now offers the possibility
of applying them in connection with fire-risk problems
as well. In risk-analysis-based design, the presented
approach is very useful and the methods can be used for
fire-risk assessment of buildings. Nevertheless, this
study should be considered the first part of a major
research effort and further studies will be needed to
improve the tentative models to obtain more detailed and
reliable risk estimates. In this work a preliminary
exploration is carried out and a good base for further
research is established.
Original language | English |
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Qualification | Doctor Degree |
Awarding Institution |
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Supervisors/Advisors |
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Award date | 1 Jul 2004 |
Place of Publication | Espoo |
Publisher | |
Print ISBNs | 951-38-6392-1 |
Electronic ISBNs | 951-38-6393-X |
Publication status | Published - 2004 |
MoE publication type | G4 Doctoral dissertation (monograph) |
Keywords
- fire risk
- building fires
- fire safety
- statistics
- ignition frequency
- economic losses
- fire department