Study Of Dynamic Responses And Security Measures In Vehicle-pier Of Pedestrian Overcrossings Collision

With the rapid development of transportation industry in our country, the construction of overpass structures such as pedestrian overcrossings, became an important way to ease traffic pressure. At Present, collisions of motor vehicle dashing against pedestrian overcrossings occur frequently, so the problem that how to protect the bridge pier from vehicles’directly hitting must be solved when building pedestrian overcrossings. So far, there are not so many studies on pier collisions and pier security measures in our country, the paper take it as a key on research.The research establishs the vehicle-bridge pier collision finite element model which based on the LS-DYNA finite element softwarestudying on the dynamic response on the different conditions such as different speed, different weight and different impact angles. Analysis results shows that the dynamic response of a bridge pier and the vehicle speed, vehicle weight have linear correlation, while vehicle impact angle has a great influence on it, the bridge pier under a big impact spot stress and the pier top have a relatively high speed for frontal impact compared to other angles, local failure of the bridge pier is very large when impact from the side, the pier top displacement is larger than frontal impact.To establish the vehicle-rigid guardrail collision finite element model which based on LS-DYNA finite element software, we enhance crashworthiness of the rigid guardrail by increasing the barrier height, thickness and improving the concrete strength. Through this calculation, two size of rigid guardrails are proposed which can effectivly stand the vehicle collisons weighed35t and55t respectively.Trying to analyze the crashworthiness of semi-rigid guardrail by computer simulation of vehicles dasging against semi-rigid guardrail and results show that semi-rigid guardrail can’t stand the impact of small vehicles (5t), collision avoidance effect is poor, impact resistant ability is weak and there is large deformationin the collision. Therrfor, it is not suitable totake as a protective structure for the pedestrian overcrossings bridge pier.Through the comparative analysis between the crashworthiness of rigid guardrail and semi-rigid guardrail, I finally recommended rigid fence as a pedestrian bridge pier safety protection structure, and gives the right rigid guardrail structure size and concrete strength.