Analysis of mechanics response for climbing section of asphalt pavement under moving load
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摘要: 以解放CA141为代表车型, 分析了车辆在驶入爬坡路段后的4种可能行为, 根据其动力性能参数计算出上坡时加减速换挡的加速度, 据此建立了移动荷载下三维沥青路面瞬态动力学分析有限元模型, 对不同行驶工况下路面内的压应力、剪应力及竖向位移特性进行分析。计算结果表明: 在移动荷载作用下, 路面结构的应力响应不仅具有波动特性, 同时在一定区域内呈现交变特性, 出现了拉压应力逆转变化, 压应力分布主要集中在路表 0~6cm范围内; 由于速度的降低及水平力的增大, 路表处最大剪应力由轮隙向轮心处迁移, 沿道路深度方向, 最大剪应力峰值由中面层位置向路表迁移; 车辆的变速及低速行驶是引起爬坡路段车辙变形的主要原因。Abstract: Jiefang CA141 was selected as a representative vehicle, the four possible kinds of driving behaviors at climbing section were analyzed, and the acceleration was calculated based on the parameters of dynamics performance when vehicle shifted to accelerate or decelerate at climbing section.A 3D finite element model was established for the transient dynamics analysis of asphalt pavement under moving load.The compressive stresses, shear stresses and vertical displacement characteristics under different driving behaviors were analyzed.Calculation result shows that under the effect of moving load, the mechanics response of pavement structure not only has fluctuation, but also presents alternating feature within a certain region, and there is reversal of changes on tension and compression stresses in the area.Specifically, compressive stress concentrates in the area of 0~6 cm for road surface, the maximum shear stress moves from wheel joint to wheel centre as the speed of vehicle reduces and the horizontal force increases, and its peak shifts from middle surface layer to road surface along depth direction.The speed variation and low speed are the main reasons for pavement rutting at climbing section.
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Key words:
- asphalt pavement /
- climbing section /
- moving load /
- mechanics indexes
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Table 1. Parameters of structure layer materials
Layer Thickness/cm Elastic modulus/MPa Poisson's ratio α-damp β-damp Density/(kg·m-3) Upper layer 4 1 300 0.35 0.4 0.005 2 613 Mid layer 6 1 100 0.35 0.4 0.005 2 613 Lower layer 8 700 0.35 0.4 0.005 2 613 Semi-rigid base 18 1 500 0.35 0.4 0.005 2 083 Subbase 31 1 500 0.35 0.4 0.005 1 932 Subgrade 200 35 0.40 0.4 0.005 1 926 
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Table 2. Vehicle parameters of CA141
Parameters Values Maximal power P/kW 99 Maximal torque M/(N·m) 372 Torque at the maximal power T/(N·m) 315.1 Rotational velocity at the maximal power ω/(r·min-1) 3 000 Rotational velocity at the maximal torques/(r·min-1) 1 300 Mass of vehicle m/kg 9 310 Air drag coefficient K 0.9 Windward acreage A/m2 4.383 Working radius R/m 0.485 Mechanical efficiency η 0.835 Load ratio U 1 Coefficient of wheel inertial force δ 0.04 Coefficient of engine inertial force κ 0.045 Transmission ratio t 5.897 Variable-ratio i and coefficients of wheel inertial force ζ First gear 7.640/3.667 Second gear 4.834/2.092 Third gear 2.856/1.407 Fourth gear 1.895/1.202 Fifth gear 1.377/1.125 Sixth gear 1.000/1.085
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Table 3. Shifting speeds of CA141
Gear First gear Second gear Third gear Fourth gear Fifth gear Speed/(km·h-1) 4.8~11.9 11.9~20.4 20.4~36.4 36.4~60.3 60.3~94.4
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Table 4. Accelerations of CA141 under different working conditions
Speed/(km·h-1) 80 50 30 Moving condition Deceleration Acceleration Deceleration Uniform speed Gear Fifth gear Fourth gear Fourth gear Third gear Acceleration/(m·s-2) -0.950 2.940 -2.655 0
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