Computational modelling and analysis of crashworthiness of different anti-ram bollard designs in frontal truck collisions
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Vehicles intruding into buildings have become a growing problem in today's world. Several types of bollards are introduced to safeguard the buildings from vehicle borne threats. Bollard (barrier/ perimeter) security systems are structures developed to impede vehicle borne threats to buildings and highway safety devices. The real-time full-scale testing of anti ram bollards, subjected to different vehicular impacts requires much effort and is highly expensive in performing the physical testing and thereby changing the design parameters. A computational analysis though can aid in narrowing the effort and evaluate the dynamic performance of different bollard designs. In this study, finite element models of bollard systems are developed according to the standards of ASTM-WK2534 and also validated with the experimental results. A medium-sized Ford single truck model is utilized, for the reconstruction of impact against various bollard systems at different speeds in frontal impact. The simulation results are correlated with the test results in terms of the kinematics of the truck, the nature of deformations, and the amount of vehicle penetrations. The validated results of a single vertical bollard, K4-rating and K8-rating bollard designs are shown to be in good agreement with the ones from the test results. The material, height, design of the bollards and the impact speed are then changed in a parametric study to arrive at the threshold velocity where each blade can be effective to study various bollard systems. The material of the bollard outer section, namely steel over aluminum is shown to provide better resistance during the impact. The study also showed that the addition of concrete inside the bollards could also improve effectiveness. In addition to the typical vertical bollard designs, a horizontal bomb barrier design is also modelled, simulated and analyzed. The simulated results show better resistance during an impact by absorbing more energy over a large area with very less deformation in the structure, as compared to the single vertical bollard design.
Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering