RESPONSE OF RC FRAME EXPOSED TO FIRE

Abstract

Performance of concrete at high temperatures is of great importance, in particular for safety evaluation of concrete structures in building fires or in thermal hazard situations. In building, structural members are to be designed to satisfy the requirement for serviceability and safety limit states. One of the major safety requirements in the building design is the provision of appropriate fire safety measures for structural members. Analyzing structural elements i.e., beams and columns separately gives an insight of thermal profile and strength & stiffness degradation. Considerable amount of work has been done on material properties at elevated temperatures. There exists a large variation in these properties. Some of these properties have been codified. There is a need for comparative study of these properties available in literature and judge their suitability. In the age of advanced computational technology, computational methods prove supreme to model the job mathematically. This modelling may be done either by using commercially available finite element analysis packages or generating customized computer program. But the most important job lies in validating the modelling technique and the results obtained from these computational methods. In this dissertation, a detailed study has been made to compare the effect of different thermal properties available in literature on the thermal response of reinforced concrete structural members. Sequentially coupled Thermal stress analyses is conducted using FEM based computational package ABAQUS, on various RC elements to study their response during fire. Stress analysis is carried out using five material models picked from literature. The effect of load level and concrete models (unconfined concrete/confined concrete) is also discussed. By combining the best model of unconfined concrete and confined concrete a very significant improvement is seen in predicting the behaviour of reinforced concrete exposed to fire. The best models (thermal and mechanical) are then - used to study the response of a RC Frame exposed to fire. 11