Performance-based fire engineering for steel framed structures [electronic resource] : a probabilistic methodology

The aim of this research is to develop a framework and criteria for Performance-Based Fire Engineering (PBFE) that are consistent with emerging performance-based structural design approaches for other hazards. Current practice for structural fire engineering in the United States is highly prescriptive and empirical, such that the risk of damage and collapse of buildings is unknown. Most codes and practice are based on standard qualification tests of individual structural members or assemblies that are based on a prescribed test fire. In this study, performance-based methods are developed to assess the probability of exceeding structural limit states that can be related to the onset of significant structural damage and collapse. While the proposed framework and approaches are general in nature, they focus on structural design considerations for steel-framed building structures subjected to fire. Proposed design approaches employ criteria and concepts that have been advanced in countries outside the United States, notably Australia, New Zealand, Japan, Britain, and the European Union. This work first collects, critiques, and synthesizes existing international research and relevant building code provisions related to structural fire engineering. Using this knowledge, an overall framework for PBFE is proposed that leverages related recent developments in Performance-Based Earthquake Engineering (PBEE). Related work in earthquake engineering is chosen since the two areas (fire and earthquakes) both address risks associated with low-probability hazards and high consequences. Moreover, as compared to other hazards, the field of earthquake engineering in the United States is further ahead in its approach to performance-based design. The proposed general probabilistic framework encompasses all aspects of a fire event, from ignition to the decision what to do with a structure after a fire. It is of such an organization that it can be investigated in parts and used by the many disciplines and stakeholders involved with all aspects of a structure's design. It is general enough to allow it to be used to comprehensively organize and encompass any part of the broad spectrum of fire engineering. Examining further a portion of this framework, this study examines the variability in the effects of fire on strength limit states for steel structures. Specifically, a reliability-based methodology is introduced to trace how uncertainties in the fire models, heat transfer, and structural behavior affect the strength limit states of steel beams and columns in flexure and compression. The reliability assessment is conditioned on the assumption that a flashover fire has occurred and, thus, it results in a conditional probability that the load effects from gravity exceed the structural resistance at elevated temperatures. By employing a probabilistic description of the input parameters and limit state models, this development illustrates how the broader PBFE framework can be applied to design and assess the strength requirements for steel beams and columns, including rotational column end restraint in columns that extend beyond the fire-affected area. Among the outcomes of the study are recommendations for temperature factors, which amplify the calculated steel temperatures and thereby reduce the effective member strengths to account for uncertainties in the fire loads and their effect on the structure. The assessment of steel member strengths builds on previous work and contributions in PBFE, especially a prior study at Stanford by Takagi, to advance the knowledge of steel framed structures at elevated temperatures.

Advisor: Deierlein Gregory G. (Gregory Gerard)
Baker Jack W. advisor. Thesis advisor
Krawinkler Helmut advisor. Thesis advisor