Analysis And Development Of Anti-collision Ability Of SAm Movable Barrier Of Expressway Central Separation

In recent years,the occurrence of major accidents at expressway central separation is frequency.Additionally to requiring mobility,movable barrier of expressway central separation must also have sufficient anti-collision ability,once the vehicle through it will be caused malignant secondary accidents.In many provinces and cities of China,the standard section barrier of the new expressway central separation belt adopts SSM level concrete barrier.According to the new regulations in 2017,the movable barrier of expressway central separation can be lower than the adjacent road sections by up to 2 protection levels,so the protection level of the movable barrier should reach the SAM level.However,most of the movable barrier in China are Am level,which is difficult to meet the requirements of the new expressway for the protection grade of movable barrier.Aiming at the problems of poor anti-collision ability and low protection level of the conventional movable barrier,this paper presents a new type of SAm concrete movable barrier.In order to ensure the moving ability of the concrete movable barrier,this paper uses a moving device installed in the interior of the barrier,which makes the barrier move flexibly by lifting the main body of the barrier and installing casters at the bottom of the barrier.In order to ensure the anti-collision ability of the concrete movable barrier,this paper presents a new type of connection mode of the concrete barrier,which can reasonably restrain the barrier and the ground by embedding the connection plate at both ends of the barrier and inserting the column.The movable barrier designed in this paper is restrained by the connection device at both ends of the barrier and the ground,which is obviously different from the main body of the conventional concrete barrier.Therefore,this paper takes the longitudinal reinforcement as the main bar,and makes a special calculation and Analysis on the stress and reinforcement of the barrier.The finite element simulation software Hypermesh and l S-DYNA were used to simulate the collision process.Using Hypermesh to make reasonable mesh and constraint setting for barrier model,and adjusting the parameters of vehicle model according to the standard of vehicle model establishment.Then using LS-DYNA to simulate the collision process between vehicle and barrier.The simulation result demonstrated that the barrier could effectively block and guide the collision vehicles,the vehicle speed,acceleration of vehicle center of gravity and maximum deformation of barrier met the requirements of safety performance evaluation standard of expressway barrier.Finally,this paper carry out the full-scale collision test of the SAM level concrete movable barrier,according to the crash results of three types of vehicles to evaluate the safety performance of barrier from buffering,containmen and redirective performance.The test results demonstrated that the occupant impact velocity is less than 12 m/s,and the occupant ridedown acceleration is less than 200 m/s~2 in the process of collision between small vehicle and guardrail in terms of buffering performance.And none of the three vehicles overturned or crossed the barrier during the collision with the barrier,and the maximum displacement of the barrier did not exceed the width of the median separator and the vehicle did not show serious damage after the collision in terms of containment and redirective performance.Therefore,the concrete movable barrier designed in this paper could meet the safety performance evaluation standard of SAm level.