Structural performance of Reinforced Concrete (RC) beams during fire depends on large number of factors. One of the factors which significantly influence the performance of RC beams during fire is its support condition. Continuous RC beams have higher fire endurance as compared to simply supported beams. Axially restrained beams may show better performance during fire depending on the line of action of axial force induced due to the restraint thermal expansion. This paper presents the results of numerical analysis of RC beams during fire, with emphasis on boundary conditions used for simulating various support conditions. The beams were exposed to standard fire as per ISO:834. The beams were analyzed for three different levels of support stiffness (axial and rotational restraints), modeled using spring elements. The results reported include axial forces & moments induced in support and the movement of line of action of induced axial force. Analysis shows that restrained RC beams may survive for more than 4hrs during fire with assumptions that the surrounding structure is able to accommodate additional forced induced due to thermal restrain and no severe spalling occurs.

Keywords: Fire, Thermal stress analysis, Boundary conditions, Support conditions.