Research On Application And Design Parameter Optimization Of Highway Bridge Approach Rigid Wedged Slab

Because of the different settlements and rigidness between the abutment and the subgrade,bridge bump often occurs at the bridge-subgrade transition section,which seriously affects the driving comfort and safety,as well as the durability of the structure and vehicle.The slab is a common method to ameliorate this problem.However,slab's fracture,second bump and other defects often occur when common slab has been used.The rigid wedged slab can overcome these defects as well as make full use of slab's advantages.This paper focus on the rigid wedged slab and a three-dimensional coupling model of the vehicle-transition section is established based on the numerical method.The car's vertical acceleration,dynamic loading coefficient,the difference of verticaldisplacement between the front wheel and the rear wheel and the height of the step on both sides of the slab are selected as the evaluation index to analyze the effect on the riding comfort with the different design parameter values of the rigid wedged slab such as slopes of the surface,maximal thickness,elasticity modulus and length.Besides,the difference of riding comfort when the vehicle driving through the transition section at different speeds is studied,and on this basis the improvement effect of the rigid wedged slab on the riding comfort is analyzed when the speed is high.Furthermore,the road surface roughness of different level is established to study the improvement effect on the riding comfort in conditions of the stochastic irregularity.Through the research above,some conclusions have been draw:(1)The car's vertical acceleration obviously reduces when the slab is set up.The height of the step on the side of the slab far away from the abutment reduces when the slopes of the surface and the length increase.The height of the step on the side of the slab near the abutment reduces when the maximal thickness and the elasticity modulus increase.The dynamic loading coefficient and the difference of vertical displacement between the front wheel and the rear wheel both reduce when the maximal thickness increase.Meanwhile,the length of the slab should not shorter than the vehicle.So in the engineering conditions of this paper,the slopes of the surface is suggested to be 10?20‰,the length is suggested to be more than 7m,the maximal thickness is suggested to be from 0.30m to 0.40m and the elasticity modulus is suggested to select C80 concrete.(2)In the same condition of the slab,the car's dynamic response increase faster when the speed is higher.When the speed is lower than lOm/s(36km/h),the effect of the speed on the car's dynamic response is little.While the speed increase from 20m/s(72km/h)to 30m/s(108km/h),the car's maximum vertical acceleration increases 104.6%,and the front and rear wheel's dynamic loading coefficient increase 55.9%and 57.3%,and the maximal difference of vertical displacement increases 25%.Thus the speed can be limited under 10m/s(36km/h)when the improvement effect of other methods for the car's dynamic response is little.The improvement effect of slab on the car's vertical acceleration reduces when the speed increases.(3)In the condition of assuming that the road surface roughness won't change with the slab,the effect of improving the car's dynamic response through the traditional and the wedged slab is very little.The difference of vertical displacement between the front wheel and the rear wheel has no difference whether the slab is set up or not.