Study On Protective Performance Of Combined Movable Barrier In Expressway Construction Area

With the continuous increase of national investment in the construction and maintenance of expressways,there will also be more lane reconstruction and expansion projects and road maintenance projects for expressways.However,due to the particularity of highways,reconstruction and expansion projects are usually carried out without closing the entire road,but only with a single or multiple lanes closed.Due to overtaking,lane changing,and bad weather,passing vehicles are prone to enter the construction area by mistake,posing a significant safety threat to construction personnel and facilities and equipment;Therefore,the adoption of movable guardrails with protective capabilities and protection levels is an inevitable trend in the future.In this thesis,aiming at the safety protection issues in the construction work area,the protective performance of a new type of combined mobile guardrail is studied by combining finite element simulation and real vehicle collision.The mobile guardrail counteracts the impact force of the vehicle by friction between the bottom and the ground.As the magnitude of friction between the guardrail and the ground can be affected by conditions such as road surface and weather,the impact of friction on the protective performance of the combined mobile guardrail is further studied.This thesis mainly conducts the following research:(1)Establish a finite element model of the guardrail;Then verify the reliability of the finite element models for three types of passenger cars(1.5t),medium-sized passenger cars(10t),and medium-sized trucks(10t);Coupling the finite element model of the guardrail and the vehicle;Summarize and explain the safety evaluation indicators of the moving guardrail,and analyze and evaluate the safety performance of the guardrail from the acceleration and speed of the minibus,as well as the vehicle collision process status,impact force changes,vehicle center of gravity height changes,vehicle derived trajectory,and lateral deformation of the moving guardrail for three types of vehicles.(2)Establish collision simulation models for three vehicle types and combined mobile guardrails under Class A collision conditions,calculate the results,and then select corresponding evaluation indicators for evaluation and analysis.Compare them with actual vehicle test data to study and analyze the protective capacity of the guardrail,while verifying the reliability of the finite element model of the guardrail.(3)Choosing small and medium-sized passenger cars as collision vehicles,changing the friction coefficient between the guardrail and the ground can correspondingly change the friction coefficient between the moving guardrail and the ground,which are set to 0.6,0.55,and 0.5,respectively,to conduct a comparative study with the standard guardrail(with a friction coefficient of 0.65).Establish collision simulation models of automobile guardrails with different friction coefficients,analyze and evaluate the collision results with corresponding indicators,and study the changes in the protective ability of guardrails as the friction decreases.The results show that:(1)In the combined mobile guardrail and the ground friction coefficient is set to 0.65(single section of the guardrail and the ground friction size of 5733N)simulation collision results are similar to the real car collision results,combined with the real car and simulation collision data analysis of the evaluation index,the results show that the mobile guardrail protection performance to meet the three(A)level of protection requirements;also verified the reliability of the mobile guardrail model.(2)Change the friction coefficient between the mobile guardrail and the ground,as the friction force decreases,the collision process state of the minibus and medium-sized bus will be more complex and the instability will be enhanced;the maximum height of the center of gravity of the vehicle in the collision process will be reduced compared with the standard guardrail,but the height of the center of gravity will repeatedly fluctuate;the lower the friction force,the larger the impact force will become,the longer the vehicle collides with the guardrail(the longer the collision force is non-zero time),the greater the impact on the stability of the vehicle.The longer the vehicle collides with the guardrail(the longer the collision force is non-zero time),the greater the impact on the stability of the vehicle;small bus in the friction coefficient is reduced to 0.55 and under,the small bus can’t smoothly export,and the vehicle center of gravity velocity in the X direction component is greater than 12 m / s,does not meet the protection capacity requirements;medium-sized bus in the friction coefficient of 0.5 with the guardrail stumbling,the vehicle can’t smoothly export.(3)In the actual use of the combined mobile guardrail,before use should verify the friction of the mobile guardrail and the ground,whether to meet the protection requirements,otherwise there will be security risks,need to take measures to increase the friction of the mobile guardrail and the ground.