Research On The Structure Of Bridge Anti-collision Wall And Its Anti-collision Property

With the rapid development of transportation industry in China,people pay more and more attention to the safety of driving on bridges.The consequence caused by vehicle falling off a bridge is often serious and fatal.For medium and large vehicles,the weak anti-collision performance of guardrail may lead to the hidden danger of vehicles rushing out of the bridge deck.Therefore,it is urgent and necessary to study the anti-collision performance of common guardrail of expressway bridges in China.This paper,with the medium bus and heavy truck as two representative types and the current road bridge anticollision wall often seen in Sichuan and Chongqing region as the object,studies its anticollision performance and contains the following content:(1)Literature survey was carried out on the common types of anti-collision walls and their functions,the main basis and basic conditions for the design of anti-collision walls were expounded,the main theoretical basis of reinforcement method for anticollision walls was introduced,and the index basis for safety performance evaluation of anti-collision walls was summarized.(2)The basic theory of nonlinear finite element solution is expounded,and the main algorithm and time-step control principle in the process of solving nonlinear problems are introduced.(3)The ANSYS/LS-DYNA software used to analyze and simulate the collision between the vehicle and the anti-collision wall and its solution process are introduced.The vehicle collision analysis model is established in ANSYS/LS-DYNA,and the validity of the vehicle model is verified by the method of frontal collision with the rigid wall.(4)Aiming at the F-type anti-collision wall which is widely used in ChengduChongqing expressway bridge,the enhanced anti-collision wall in the Chinese standard and the type after arc shape optimization of the enhanced anti-collision wall,the research on the anti-collision performance of medium bus and heavy truck at the speed of 80km/h and the impact angle of 20° is carried out.The results show that for the medium bus,the acceleration of the center of mass of the vehicle after collision with the F-type anticollision wall and the standard reinforced anti-collision wall exceeds the standard limit of 20 g,and the injury degree to the occupants is high.When colliding with the enhanced anti-collision wall after arc shape optimization,the acceleration of the center of mass of the bus does not exceed the standard limit,and the injury to the occupants is relatively light.The dynamic displacement of the three types of anti-collision walls is less than the allowable deformation value of the rigid guardrail under the impact of the medium bus.The height difference between the front wheels on both sides of the medium-size bus and the arc shape optimization anti-collision wall is the smallest.For heavy trucks,the climb height is the largest after colliding with the F-type anti-collision wall,and the wheel difference generated by the front wheels on both sides of the truck is the largest,and the roll coefficient is the highest.When it collides with the arc shape optimization anticollision wall,the difference between the climbing height of the wheel and the vertical height of the front wheels on both sides is the smallest and the safety factor is the highest.It can be seen that the anticollision wall after arc shape optimization can alleviate the intensity of collision and reduce the rollover coefficient of heavy truck.The resistance barrier has an obvious effect on restraining large vehicles from climbing along the anticollision wall.The addition of resistance barrier and the arc treatment of the edges and corners of the standard anti-collision wall are convenient and effective,which is of great significance for reconstructing the old guardrail and the ensuring driving safety.(5)The anti-collision performance of the reinforced concrete anti-collision wall after arc shape optimization is analyzed,and the influence of different vehicle types,different speeds,different impact angles and different impact positions on the displacement response of anti-collision wall,the vertical jumping height of vehicle and the acceleration of the center of mass of passenger car is studied.The results show that the maximum dynamic displacement of the anti-collision wall and the acceleration of the vehicle’s center of mass increase with the increase of the impact velocity.The maximum dynamic displacement of the wall and the jump height of the left front wheel of the truck increase with the increase of the collision velocity under the impact of heavy truck.In the range of 15°～25° impact angle,the maximum transverse dynamic displacement of the anticollision wall decreases with the increase of impact angle.The jump height of the front wheel near the collision wall increases with the increase of collision angle.For heavy trucks,when the collision position overlaps with the crack position of the anti-collision wall and its adjacent area,the height difference between the vehicle’s climbing height and the wheel height is significantly higher than that of other areas and the maximum lateral dynamic displacement of the SA class anti-collision wall exceeds the allowable limit in the code.