Explicit Modelling of Large Deflection Behaviour of Restrained Reinforced Concrete Beams in Fire

This paper presents a dynamic explicit finite element (FE) simulation method to predict the highly nonlinear response of axially and rotationally restrained reinforced concrete (RC) beams at ambient temperature and in fire condition. Catenary action, developed during the large deflection behaviour of RC beams, is an important mechanism of resisting progressive collapse. This paper explains the numerical simulation challenges, including temporary instabilities, local failure of materials, non-convergence and long simulation time, and proposes methods to resolve these challenges. The effectiveness of the proposed simulation model is checked by comparison of the simulation results against relevant test results of restrained RC beams at ambient temperature and in fire. It has been found that using the explicit simulation method can follow the whole range behaviour of restrained RC beams until complete structural failure. Either load factoring or mass scaling may be used to speed up the simulation process. Damping can be applied to minimise significant dynamic effects following beam bending failure. This paper will give guidance on how to select the appropriate load factoring, mass scaling and damping values.