Design of Steel Buildings without Fire Protection


Fire safety is an important consideration in the design of multi-storey buildings

and this publication describes ways of achieving the necessary levels of safety

without the use of applied fire protection. According to the Regulations, the

elements of structure of most moderate sized offices require 60 minutes fire

resistance when tested in a standard fire resistance test, whilst those in two storey

offices normally require only 30 minutes fire resistance. The fire resistance

requirements for buildings in the UK are specified in The Building Regulations.






INTRODUCTION

The requirements vary, up to 240 minutes, depending on the building height, size and use.

In most modern steel framed buildings, the members would typically be protected

from the effects of fire by spray or board protection, or intumescent coatings.

These methods have proven more economical than the more traditional approach

of encasing the steel in concrete or masonry.

The required amount of protection to steel frames is dependent on the type of

member, its shape and the fire resistance to be achieved. However, The Building

Regulations do not specify that a structure must have fire protection, only that it

must have fire resistance. This is an important distinction, as many types of steel

members can economically achieve up to 60 minutes fire resistance without

requiring applied fire protection.

At the design stage, most designers do not consider the method of protecting steel

structures from the effects of fire. It is common practice for fire protection to be

regarded as a finish, consequently, the normal sequence is to design, construct and

then fire protect. However, through the influence of BS 5950-8:1990

, advances

have been made, which offer an alternative approach. This involves the use of

fire engineering design which is a more rational rather than prescriptive approach.

Fire engineering design methods may impose some limitations, but have the

advantage of largely eliminating the fire protection trade from site, which can lead

to significant economies and take the fire protection activity off the critical path.

As approximately 80% of steel framed buildings require 60 minutes or less fire

resistance, the scope for application of these methods in practice is appreciable.

In this publication, methods of designing and constructing steel framed buildings

for 30 and 60 minutes fire resistance without applied fire protection are described.

In most instances the structural configurations presented in this guide are covered

by design codes of practice and design guides published by The Steel Construction

Institute or other organisations. Only a summary of the design procedures are

thus included, and the reader is directed towards more specialised documents for

detailed guidance.


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