Numerical Analysis of Reinforced Concrete Frames Subjected to Fire under Loading

Research over the last decade has shown that composite floor structures can have a significantly greater fire resistance than is suggested by conventional tests on isolated elements, this is largely due to the interaction between the beams and floor slabs and beams-column connections in the fire compartment and the restraint afforded by the surrounding structure. This research was carried out to investigate the effect of fire on the behavior of reinforced concrete frames especially the connection between beam and column, where a special model for a fire furnace was designed in HBRC in order to investigate the aim of the current research. An experimental program consisted of thirteen statically independent two hinged reinforced concrete frames is designed to study the deformational behavior of RC frames subjected to fire under short term loading in terms of deflection and strain distribution, temperatures distribution along the critical cross sections at different limit states with the following variables: fire durations (1,2 and 3 hours), and fire temperatures (300,600 and 800°C) with concrete strength (250 and 600 kg/cm2). Modes of failure, ultimate capacity, deflection and strain of steel reinforcement and concrete at critical sections were examined experimentally and theoretically. The non-linear finite element analysis for reinforced concrete structure is largely dependant on the stress-strain relationships, failure criteria used, simulation of steel reinforcement and interaction between steel and concrete [1]. A model for predicting the behavior of reinforced concrete frames failure was developed based on experimental results obtained from the experimental program carried out by the authors. This model has been incorporated into a new reinforced concrete element for the non-linear analysis program, using ANSYS Ver.10 program. In this paper, a general description of the finite element method, theoretical modeling of concrete and reinforcement are presented. In order to verify the analytical model used in this research using test results of the experimental data of the experimental branch, the finite element analysis were performed then to be able to proposed a guide charts which can be used to predict the moment capacity of joint in beam-column connection in RC frames subjected to fire taking into consideration the different fire durations, fire temperature, and concrete strength.