An Overview Of Optimising Passive Fire Protection Using A Limiting Temperature By Structural Assessment

Abstract

The British Standards and the Eurocodes both cover the design of steel structures in fire. These provide designers with the opportunity to exploit the properties of structural steel to its maximum capacity in the fire limit state, termed Structural Fire Engineering. This allows fire protection measures to be integrated into structural design as part of the passive fire protection specification. If used effectively in the specification process it can bring significant benefits to the project, including robust and safe designs, quantified structural performance and cost savings.The suitability of a member in a structural design is generally governed by serviceability limitations such as deflection. Generally this approach provides a conservative working stress for the steel sections of approximately 50% of their overall capacity. Within the UK, this simplified approach led to the development of prescribed limiting steel temperatures of 550°C for columns and 620°C for beams.Best-practice industry guidance published in the UK encourages designers to specify a limiting steel temperature together with the fire resistance period as part of the overall steelwork specification. Passive fire protection is generally specified post design-stage at a contractor or applicator level and sometimes very little is known about the limiting steel temperature.This paper provides an overview of the fire protection specification and provides advice on structural fire engineering to determine a limiting steel temperature and the benefits that can be gained from doing so. The paper highlights how supplier expertise in fire engineering approaches and product performance knowledge can bring value to a design and play an important role in providing safe, cost effective and compliant solutions.