The level of safety for different building designs in case of fire.

A risk analysis for a building. The project was sponsored by the Ministry of Local Government and Regional Development (KRD) and carried out by carried out by the Norwegian Fire Research Laboratory. The objective was to estimate the safety level for three different building designs, and to test a method for predicting the level of safety.

A risk analysis for a building

The project was sponsored by the Ministry of Local Government and Regional Development (KRD) and carried out by carried out by the Norwegian Fire Research Laboratory. The objective was to estimate the safety level for three different building designs, and to test a method for predicting the level of safety.

The project was sponsored by the Ministry of Local Government and Regional Development (KRD) and carried out by carried out by the Norwegian Fire Research Laboratory. The objective was to estimate the safety level for three different building designs, and to test a method for predicting the level of safety.
The Norwegian Building Code from 1997 gives two alternative ways for documentation of safety requirements, either to use pre-accepted solutions in the design or to prove that the safety with regard to fire is satisfactory by means of analysis and/or calculations.

The Guidance to the Building Code from 1997 describes several pre-accepted solutions, which satisfies the Code. These are often previously used construction designs, which is still acceptable since the level of safety level was not to be changed by the introduction of 1997 code. Most of these design solutions do not have a documented impact to the level of safety. This study quantifies this level of safety by studying some examples.

The chosen building was a Care Centre for elderly. In the first alternative the building was designed with fire cell to resist fire for 60 minutes. In alternative 2 the fire resistance for each cell was 30 minutes. In alternative 3, the safety classes were identical to alternative 2, but in addition a residential sprinkler was installed in each room.
 
 

The figure shows the ground floor and the first floor of an existing Care Centre for elderly

The intention was to find the level of safety  for these three alternatives, and to evaluate the usefulness/applicability of a calculation method estimating the risk to lives during fire.
The chosen calculation method for estimating risk to life during fire in buildings is described in SINTEF report no. STF38 A97421 from 1998 (Hokstad,P., Mostue, B.Aa., Opstad,K., Paulsen,T.). The report is written in Norwegian.

This risk analysis method estimates the risk to life of occupants in case of fire, measured by FAR value (Fatal Accident Rate = number of fatalities due to fire per 108 person hours in the building) and frequency of disasters. The result is compared to given acceptance criteria based on the ALARP-principle (As Low As Reasonably Practicable). However this study shows that it is recommendable to compare analysis results from different building solutions, rather than measure the result of an analysis against a numerical value for acceptable level (an acceptance criteria).

The results of the calculation show that the Care Centre designed as in alternative 1 (60 minutes fire resistance) and alternative 3 (30 minutes fire resistance and residential sprinkler installed) have the same level of safety, and a higher level of safety than in alternative 2 (30 minutes fire resistance without sprinkler).

To carry out a complete risk analysis for fires in buildings is a demanding task, and it requires high competence within several fields. The risk analysis method is meant to be an objective tool for predicting risk to life during fire in buildings. The method used is exceptional because it takes into consideration what kind of people staying in the building, what kind of activity goes on in the building and also building conditions. The risk analysis method provides the user with quality guidance in how to carry out the analysis and which conditions affect risk to life in case of fire. The method requires however expert knowledge within fire development and on the effect of fire on building constructions and on human behaviour.

• Report STF22 A00828 published 2000-07-06 by  Norwegian Fire Research Laboratory 
• Contact person:
  Bodil Aamnes Mostue
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