PERFORMANCE BASED ANALYSIS OF RC ELEMENTS EXPOSED TO FIRE

Abstract

Latest advancements in the domain of fire safety have triggered a shift from conventional prescriptive to performance based approaches. Also, in the era of modern computational technology, mathematical models prove to be a more efficient way of quantifying structural performance rather than full scale testing. Analysing structural elements i.e., beams and columns separately gives an insight of thermal profile and strength & stiffiess degradation during fire accident. Considerable amount of work has been done on material properties at elevated temperatures. However, a large variation exists in available material properties at elevated temperatures. This makes it imperative to conduct comparative studies in order to ascertain their suitability. Validation against experimental results is a very important concern. In this dissertation, an attempt has been made to compare the effect of different constitutive models available in literature on the thermal response of reinforced concrete elements and hence arrive at optimum modeling strategies. Performance based sequentially coupled thermal stress analyses was conducted on RC elements using the commercial general purpose finite element analysis (FEA) package ABAQUS. For axial members, the effect of load level and confinement was also studied. It was observed that including effect of confinement improves accuracy of results and is more important at higher load levels in axial members. Residual behaviour of flexural members was simulated wherein the importance of modelling the complete heating and cooling cycle rather than employing residual models on undamaged specimen was also elucidated. Results improved significantly in case of flexural members when the whole sequence of events was modelled. Further, gap areas were also identified for future studies in this area