Performance Based Structural Fire Engineering for Modern Building Design

Abstract

Performance-based structural fire engineering (PB SFE) is internationally a fast growing field of engineering where the design of the fire protection strategy and structural detailing of a building is based on calculating the structure’s behaviour under realistic fire scenarios. While current practice in the United States is primarily prescriptive in nature, performance based structural fire engineering is beginning to have an impact on building design particularly as architects conceive more complex designs and engineers have an increased understanding of structural fire response from the WTC collapse and more recently the Windsor tower fire in Madrid. Historically, the determination of structural fire resistance is established in a standard furnace test. These standard tests have existed in the same form for over 100 years. The tests are a necessary part of our regulatory systems because they provide invaluable data on the relative performance of materials and small-scale assemblies in fire. However, the primary concern with prescriptive fire resistance ratings is the reliance on the assumption that a structural system tested at a relatively short span, in a furnace, can robustly translate into a basis for design at the scale required in real buildings where continuity, connections, alternative load paths, and restraint play a significant role in structural performance in fire. The concern with the reliance on these standard fire tests as a basis for design particularly as buildings become larger and more complex, has led to the development of alternative design techniques. Over several decades, various researchers have investigated the phenomenon of real structural fire performance and developed various analytical methods for use in the design domain. Through the use of PB SFE, the structure can be designed to resist a realistic fire with less reliance on passive fire protection. The assessment allows the design engineer to check for any structural design weaknesses/strengths in fire, to identify robust design features, to determine an optimised passive fire protection strategy and if necessary, to provide structural details to enhance the structural performance in fire. This paper presents a case study of performance based structural fire engineering conducted in the U.K. The case study demonstrates how structural fire engineering, using either simple or advanced forms of analysis, can provide a robust and fire safe solution. Note: The advanced finite element analysis presented here is currently being conducted in the U.S. and will be subject of a separate publication.