| A two-scale numerical model is developed to study the behavior of reinforced concrete (RC) frame structures subject to fire loading. In this model, various structural components, such as beams, columns, and beam-column joints, are modeled by elastic elements connected by a set of nonlinear cohesive elements, which represent the potential damage zones. The thermo-dependent constitutive behavior of each cohesive element is determined by nonlinear finite elements (FE) simulations of its corresponding potential damage zone under different loading modes at different temperatures, where the thermo-dependent material properties for the FE simulations are determined based on the existing literature and a set of high-temperature experiments on concrete. The proposed two-scale model is used to simulate the behavior of a RC frame subassemblage under thermomechanical loading and the simulation results are further compared with the prediction by using the conventional finite element model. It is shown that the present model can well capture the nonlinear behavior of RC frame structures under thermomechanical loading, and due to its computational efficiency, the model provides us an efficient means to investigate the global behavior of large-scale RC frame structures under fires. |
