This paper presents an approach for evaluating the residual strength of fire-exposed reinforced (RC) concrete beams. Data from post-fire residual strength tests on three RC beams are presented. Two of the beams were made of high-strength concrete and the third beam was of normal-strength concrete. Results from the tests indicate that RC beams retain most of their room-temperature flexural capacity after exposure to fire. Data from fire tests and numerical studies are utilised to develop a simplified approach for evaluating the post-fire residual strength of RC beams. The validity of the approach is established by comparing residual strength predictions with measured values obtained from the tests. The paper shows that the proposed approach is capable of predicting the residual strength of fire-exposed RC beams with sufficient accuracy for practical applications.
The use of concrete filling offers a practical alternative for achieving the required fire resistance in steel hollow structural section columns. However, the current prescriptive-based approach which evaluates fire resistance based on standard fire exposure does not account for realistic fire scenarios in the design of concrete-filled hollow structural section (CFHSS) columns. This article presents a methodology for evaluating the fire resistance of CFHSS columns under design fire scenarios without the need for costly computational models. The proposed approach is a derivative of the equal area concept, and evaluates the equivalent fire resistance of the column by comparing the time temperature curve of the standard fire exposure with that of the design fire exposure. The method has been validated against the results generated from finite element analysis (coupled heat transfer and strength analysis) on numerous CFHSS columns under a large number of design fires. The applicability of the approach in design situations is illustrated through a numerical example, and it is concluded that the proposed approach offers an attractive alternative for deriving equivalent fire resistance of CFHSS columns exposed to design fire scenarios.
The current approach of evaluating fire resistance is mainly through standard fire tests. The specifications for standard fire tests have a number of drawbacks and require only a limited amount of data to be collected during tests, and this is hindering the development of calculation methodologies for evaluating fire resistance. This paper discusses the various drawbacks in the current specifications for undertaking fire resistance tests. The improvements needed to make the standard fire resistance tests more effective and the collected test data more useful are outlined. Strategies for implementing the proposed recommendations (improvements) in test standards are illustrated with examples. Finally, the applicability of the proposed recommendations is illustrated by undertaking fire resistance tests on a midsized column and a midsized beam under improved test specifications. Data collected from these fire resistance tests is used to calibrate finite element based computer models, thus demonstrating the effectiveness of collecting additional test data.
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