The Practical Application of Structural Fire Engineering on a Retail Development in the UK

The British Building Regulations allow the application of performance based design methods to ensure the fire resistance of buildings. This has led to significant amounts of research and testing on the fire performance of structures. This research generated the understanding that steel framed buildings have an inherent fire resistance, which has in turn resulted in the development of specialist numerical calculation tools as well as simplified design methods for the fire design of steel-framed structures. The paper describes the practical application of these structural fire engineering methods using a large retail and cinema complex in the UK as a case study. The finite element software Vulcan has been used to analyse the behaviour of large parts of this multi-storey building during a number of likely design fire scenarios in order to optimise the amount of applied passive fire protection to the structure. The building is constructed as a steel composite structure with normal down-stand composite beams supporting a composite floor on trapezoidal metal deck. This type of structure is ideal to utilise the benefits of tensile membrane action during a fire which can be used to omit fire protection from off grid secondary beams. Due to the size and the multiple usage and changing floor construction of the buildings five different sub-frames haven been analysed. In the UK a number of simplified methods are currently applied to justify partially protected steel structures. These methods are based on individual bays only and therefore do not consider the effects of the surrounding structure. In order to investigate the differences further, the behaviour of the large sub-frame models has been compared with the results of individual bay analysis methods.