Nonlinear Dynamic Analysis of Frame Elements Subjected to Blast Explosions

A finite element method was recently proposed for performing nonlinear analysis of plane frames subjected to blast loads. This method uses an explicit three-parameter time integration method within a total-load, secant-stiffness analysis framework. Rigorous nonlinear sectional analyses are undertaken, considering the strain rate effects and utilizing nonlinear concrete and reinforcement hysteresis models. Shear effects are included through a 2D implementation of the Disturbed Stress Field Model, which is based on a smeared rotating crack conceptualization. In this study, numerical modeling of 18 previously-tested specimens was undertaken to verify the accuracy, reliability, and practicality of this method for blast load conditions. Some specimens were subjected to multiple blast loads, resulting in 24 simulations in total. Most specimens were subjected to very high peak reflected pressures in the range of 0.35 MPa and exhibited significant damage and nonlinearity. Analysis results (obtained from this method and two other methods from the literature) are compared to the experimental responses in terms of peak displacements, stiffnesses, residual displacements, and crack widths. The three advantages of the proposed method were demonstrated: more accurate modeling of reinforced concrete behaviour, simpler modeling requirements, and shorter analysis times. The proposed method was found to simulate the experimental behaviours of the specimens examined with a high degree of accuracy. The solution algorithm provided unconditional numerical stability, and required much shorter analysis times than continuum finite element methods.