Impact analysis of I-Lam sandwich system for over-height collision protection of highway bridges

Due to increased traffic volumes and incidence of impact damaged to bridge structures, there is a pressing need to develop a collision protection system for highway bridges against over-height truck impact. In this study, a linear elastic model for the impact response of bottom face sheet-rigidly supported sandwich structures including shear-off effect is developed. The solutions for a discrete model and concentrated and distributed loading cases for collision protection I-Lam system are obtained, of which the contact force history and maximum deflection are predicted. Compared to the LS-DYNA finite element analysis (FEA), the relatively simple analytical methods proposed accurately predict the impact response. The discrete model shows a better correlation with FEA predictions, while the model with distributed forces overestimates the deflection of the top face sheet but under-evaluates the peak contact force. The developed models including the shear-off mechanism can be used to approximate the impact response of rigidly supported sandwich structures hit by an over-height truck. The two important impact factors, i.e. the maximal deflection and peak contact force, can be used in primary design and optimization of collision protection sandwich structures.