Dynamic mechanical responses of reinforced concrete pier to debris avalanche impact based on the DEM-FEM coupled method

Engineering accidents of bridge pier damage and collapse incurred by debris avalanches frequently occur in mountainous areas. This paper presented a three-dimensional DEM-FEM coupled numerical model with the aim of exploring the dynamic mechanical characteristics of a reinforced concrete (RC) bridge pier subjected to a debris avalanche. It allows for considering the debris avalanche particles' discreteness and the continuous me-dium's structural dynamic responses. Moreover, a steel-sand composite structure was introduced to shield the pier from the impacting damage. The coupled model, constructed in the LS-DYNA software, was described in detail as well as its validation. The complicated interaction mechanism between the debris avalanche and the RC pier was interpreted. The critical dynamic responses of the RC pier throughout the collision process were also analyzed. A detailed discussion of influential parameters indicates that the debris avalanche's dry density has the most significant effect on dynamic mechanical characteristics of the bridge pier. Moreover, the numerical simulation of the RC pier with a steel-sand composite protective structure impacted by the debris avalanche was performed, and the results indicate that the composite shield could provide superior anti-collision performances.