Effect of nonstructural mass on debris impact demands: Experimental and simulation studies

Tsunamis, floods, and hurricane storm surge and waves generate debris such as shipping containers, trees, and vehicles. Impact forces imposed on buildings and bridges from such debris can lead to extensive structural damage. A reliable estimation of debris impact demands is vital for the safe design of structures against water-borne debris. The objectives of this study are to investigate the effect that supplemental non-structural mass attached to debris has on the generated impact demands and to develop a simple model that accurately estimates the peak impact force, impulse, and duration. An experimental study is carried out on a loaded shipping container subjected to in-air axial impacts. A nonlinear dynamic finite element model of a standard shipping container including contents is developed and validated by comparing with the full-scale impact experiments. Parametric studies are carried out to investigate the effects of impact velocity, nonstructural mass attachment, and magnitude of payload mass during both elastic and inelastic axial impact of a shipping container. The results indicate that the peak impact force is not affected by a non-rigidly attached payload mass. The experimental data and simulation results are used to develop and justify a simplified method for estimating the impact force. The simplified method is found to provide an accurate estimate of debris impact demands.