XFEM BASED SIMULATION ON THE MECHANISM OF PINCHING EFFECT OF RC COLUMNS

It is of great significance to predict the behavior of a RC column under seismic loading and make assessments on the safety of a structure. The accurate calculation on the behavior of concrete members mainly relies on numerical simulation analysis at present due to complicity of material and mechanical response. However, the majorities of conventional methods are normally based on the finite element method, taking concrete as continuum and using simplified parameters to describe the hysteretic behavior of RC members. To exhibit the mechanism of seismic damage, a novel numerical method based on extended finite element method is proposed. The extended finite element method and fracture criterion is engaged to simulate the discontinuous behavior of concrete, namely crack initiating and propagating and closure. The bond-slip relationship between concrete and rebar are taken into account in the interval of cracks. Specific hysteretic performance is not specified by material property inputting, but by reflecting in mechanical response. Simulation result is verified by test, which shows good agreements in all aspects. Besides, the further analysis is conducted on the aseismic behavior of RC columns in a micro-level and three main causes are raised to explain the mechanism of pinching effect.