Fire engineering and structural design – common misconceptions and good practice

Most structures in Europe are constructed using limit state design methods. Most of these structures are protected against some form of specified fire scenario. However, only a small minority of projects link these two major considerations together to form part of a unified structural fire design process. The Eurocodes provide designers with the necessary procedures to undertake an accurate and economical structural fire design, yet few engineers ever consider undertaking such an assessment. This article will focus on the load actions and combinations to be considered that enable the engineer to perform an adequate structural assessment for the accidental limit state in fire. It will also cover important considerations to ensure that any structural fire engineering strategy is appropriately aligned, and the key information is available within the contract chain to facilitate this performance-based approach.

Fire is a basic hazard which can devastate buildings, cities and regions. It is therefore an essential part of an engineer’s skill set to understand and control the risk. Control is a key word, for the risk can never be eliminated, as the recent Grenfell Tower fire in London reminds us. That event was truly a nightmare: an out-of-control fire destroying a whole residential tower, killing 71 occupants. In the same contemporary timeframe, wild fires in California destroyed approx. 9000 structures and left over 40 dead, reminding us of the consequences of regional fires. How these catastrophes happened is yet to be established. It is said that lessons should be learned, and so they should, since the history of fire engineering is largely one of reaction to disasters. As a start, it’s worth observing, as some of the papers in this special issue do, that the basic skills of ‘fire engineering’ are probably absent among many of us. That situation stems partly from an omission of basic training; perhaps from a feeling that this is a speciality for others, and perhaps because advances have been rapid. This is unsatisfactory and unsafe. Fire protection needs to be ensured overall between the architects, plant engineers and structural engineers who make up any project team: we have collective obligations to make buildings ‘safe’.

Designers of the built environment are currently focused on creating new materials for construction, or innovating new construction methods with traditional construction materials. This is part of the very complex challenge of balancing environmental issues, such as energy use, with the ongoing market demand for reducing construction costs and time. This has led to a rapid rise in the uptake of timber, such as glued laminated timber (glulam) and cross-laminated timber (CLT), particularly in the design of multistorey residential buildings. This paper focuses on the design of tall timber construction for which many hybrid and composite forms of timber are being developed, resulting in a wide range of structural typologies.