Mountainous Freeway Roadside Guardrail Design Based On Finite Element Analysis

For mountainous freeway, terrain is complicated and there are lot of road sections oflong downhill, small radius and bad sight, so when the vehicle travels on mountainousfreeway, it is hard for driver to operate the vehicle and roadside accidents may occur, then thevehicle may collide with guardrail. Because of the complicated terrain and bad roadsideenvironments, once the travelling vehicle runs off road, fatal consequence may be led to. Thecurrent guardrail of mountainous freeway has some problems and the accidents of running offroad often happen, so it is much necessary to analyze the mountainous freeway roadsideguardrail force condition when being collided with big force to design current mountainousfreeway roadside guardrail to improve the mountainous freeway safety level.Main contents of this paper are as follows:①According to finite element analysistheory, this paper analyzed one rectangular object force condition using the finiteelement analysis software ANSYS. According to finite element analysis theory including thecommonly used elasticity Hooke’s law and balance equation, geometric equations andphysics equations and boundary conditions needed to solve the stress, strain and displacement,this paper indicated that it is hard to solve complicated objects without computer help and itis acceptable to use finite element analysis software, and analyzed one rectangular objectforce condition using the ANSYS.②This paper analyzed the common types of guardrail,features and specification requirements for guardrails and built three-dimensionalmountainous freeway roadside guardrail finite element model. There are three commontypes of guardrail including flexible guardrail, rigid guardrail and semi-rigid guardrail. Themain manifestation of flexible guardrail is rope guardrail, which is harmonious with theenvironment but is set limited defense capability; rigid guardrail is mainly in the form ofcement concrete guardrail, of which the strength is large enough to prevent the vehiclerunning off the road, however, it often occurs that the collision causes serious damage to thevehicle and even leads to casualties of occupants; semi-rigid guardrail is commonly usedbetween flexible and rigid fence, which is the focus of the research. According to differentcollision level requirements of specification and combining the main roadside beam guardrail Gr-SB-2E of Jingmu mountainous freeway, this paper established a three-dimensional finiteelement model, and the model was meshed.③This paper analyzed the impact of the slopegradient, slope length on the collision speed between vehicle and roadside guardrail, theimpact of horizontal curve radius on the angle of the collision, the impact of vehiclefaults on collision angle, the impact of vehicle mass and size on collision force,transformed the impact into collision force and applied to the finite element modelestablished. According to mountainous freeway design requirements, this paper analyzed andcalculated impact different slope gradients, different slope length, different rolling frictioncoefficients on the lost control vehicle speed with different initial speeds; this paper analyzedthe impact of mountainous freeway horizontal curve radius on the collision angle, from theresults the collision angle could be any value from0to90degrees; this paper analyzed theimpact of tire size and the distance between the vehicle and roadside guardrail on thecollision angle after tire burst, from the results the collision angle could be any value from0to90degrees. Then the impact of different vehicle sizes, vehicle mass, collision speed andcollision angle was transformed into the collision force and the collision force was applied tothe guardrail three-dimensional finite element model established.④This paper analyzedthe displacement and stress of mountainous freeway roadside guardrail by large force(large vehicle, large-angle, high-speed collision) and improved the design ofmountainous freeway roadside. After applying load to the established finite element model,this paper used ANSYS to solve computing and display guardrail displacement and stressdiagram, from the results there is large displacement and stress in the guardrail under largeforce (large vehicle, large angle, high-speed collision) and the roadside guardrail is possibleto break.Finally, this paper proposed corresponding improvement design:①change columnspace from the original two meters into one meter,②change guardrail beams from theoriginal three waves into four waves. For improved roadside guardrail, finite element modelwas established, meshed, applied with load, again the calculation process was solved, and thispaper compared the internal stress and displacement, and from the results, the displacement and stress have a significantly smaller to verify the design of the proposed improvements onmountainous freeway roadside guardrail.