Recommendations for performance-based fire design of composite steel buildings using computational analysis

Adoption of performance-based approaches in structural fire engineering is now largely recognized as having the potential to deliver benefits in terms of safety, resilience, sustainability and cost for the built environment. However, there is no systematic design guidelines for defining performance objectives, design fire scenarios, and methods of analysis. This paper focuses on steel framed buildings with composite floor slabs and provides an in-depth analysis of the structure under fire using performance-based fire engineering supported by computational modeling. First, a set of performance objectives and associated fire scenarios are defined. The scenarios include single- and multi-compartment fires as well as fire as a secondary event following a column loss. Then, response of the structure and effects of design changes are studied using different modeling approaches. Single slab, single slab with restraint, and full building models are investigated to understand the influence of continuity in the boundary conditions notably on the development of tensile membrane action. The full building model exhibited the most favorable behavior, while the single panel model without horizontal restraint was the most conservative. Best practices for computational modeling of a steel framed building under fire are discussed and recommendations are provided. The paper demonstrates an iterative design procedure, where systematic design changes are introduced to address the observed failure modes. It is shown that performance-based fire design can harness advanced computational models to examine the fire-structure behavior for multiple design alternatives and hazard scenarios.