Fire response of concrete structural members is dependent on the thermal, mechanical, and deformation properties of concrete. These properties vary significantly with temperature and also depend on the composition and characteristics of concrete batch mix as well as heating rate and other environmental conditions. In this chapter, the key characteristics of concrete are outlined. The various properties that influence fire resistance performance, together with the role of these properties on fire resistance, are discussed. The variation of thermal, mechanical, deformation, and spalling properties with temperature for different types of concrete are presented.

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Properties of Concrete at Elevated Temperatures

Fire is one of the most severe conditions to which structures can be subjected, and hence, the provision of appropriate fire safety measures for structural members is an important aspect of design. The recent introduction of performance-based codes has increased the use of computer-based models for fire resistance assessment. For evaluating the fire resistance of steel structures, high-temperature properties of steel are to be specified as input data. This paper reviews high-temperature constitutive relationships for steel currently available in American and European standards, and highlights the variation between these relationships through comparison with published experimental results. The effect of various constitutive models on overall fire resistance predictions is illustrated through case studies. It is also shown that high-temperature creep, which is not often included in constitutive models, has a significant influence on the fire response of steel structures. Results from the case studies are used to draw recommendations on the use of appropriate constitutive models for fire resistance assessment.

High-Temperature Properties of Steel for Fire Resistance Modeling of Structures

A numerical model, in the form of a computer program, for tracing the behavior of reinforced concrete (RC) beams exposed to fire is presented. The three stages associated with the numerical procedure for evaluating fire resistance of RC beams; namely, fire temperature calculation, thermal analysis and strength analysis, are explained. A simplified approach to account for spalling under fire conditions is incorporated into the model. The use of the computer program for tracing the response of RC beams from the initial pre-loading stage to collapse stage, due to the combined effect of fire and loading, is demonstrated. The validity of the numerical model is established by comparing the predictions from the computer program with results from full-scale fire resistance tests. Through the results of numerical study, it is shown that the type of failure criterion has significant influence on predicting the fire resistance of RC beams.

A numerical model for predicting the fire resistance of reinforced concrete beams

Aluminium alloys as structural material: A review of research

Results from fire resistance experiments on six RC beams are presented in this paper. The test variables included concrete strength (permeability), support conditions, fire scenario, and load ratio. Data from fire tests are used to illustrate the comparative performance of high strength concrete (HSC) and normal strength concrete (NSC) beams under fire conditions. Also, data from the tests is used to validate a macroscopic finite-element model specifically developed for tracing the fire response of RC beams. Results from the tests and numerical studies show that HSC beams have lower fire resistance than that of NSC beams. It is also shown that HSC beams exhibit higher levels of spalling which is largely influenced by the permeability of concrete, type of fire exposure, load level, and restraint conditions. Similarly, the type of fire scenario, axial restraint, and load level have significant influence on the overall fire resistance of RC beams. These factors are to be considered for evaluating the fire resistance of RC beams under fire conditions.

T. Z. Harmathy

Papers

A Comprehensive Creep Model