The explosive behavior of RC members due to thermal stress and vapor pressure under high temperature was investigated numerically using a developed method. RBSM-TRUSS Network model was adopted as an analytical method, in which 3-dimensional Rigid Body Spring Method (RBSM) based on dynamic equation of motion as structural analysis and truss network model as mass transfer analysis were integrated. Moreover, the effect of rebar such as heat conduction and thermal expansion was modeled. Two RC members were simulated and it was shown that rebar with small cover influence to damage accumulation and explosive behaviour.