混凝土宽箱梁汽车偏载效应分析

Study on Eccentric Load Effect of Wide-flange Concrete Box-girder Under Offset Loaded Vehicles

为探讨汽车偏心加载条件下混凝土宽箱梁的偏载效应,以某座主梁宽度为38 m、主跨为210 m的部分斜拉桥为工程背景,利用实体有限元模型对比分析了汽车荷载对称布置和偏心布置情况下箱梁控制截面应力、弯矩和剪力的空间分布特征,并以偏载系数和剪力滞系数为评价指标讨论了汽车荷载的偏载效应和剪力滞效应。通过分析发现:汽车荷载的局部轮载和剪力滞效应造成控制截面上顶板正应力分布极不均匀,剪力滞系数最大可达1. 47,而车辆偏心布置时截面正应力偏载系数最大可达1. 2,大于桥梁设计中常使用的偏载系数1.15;汽车偏心布置时靠近车辆一侧的边腹板所承担的弯矩和剪力均有所增大,其中弯矩偏载系数为1. 1左右,而剪力偏载系数为1. 8(远大于1. 15),工程中应该引起足够重视。

In order to analyze the eccentric load effects of wide-flange box-girder under offset loaded vehicles,an FE model with solid elements was established based on a short-pylon cable-stayed bridge with main span 210 m and girder width 38m.It was discussed that the differences on spatial distribution characters of section stress,bending moment and shear force reduced by symmetric and asymmetric vehicles.Subsequently,the partial effect and shear-lag effects of vehicle load on stresses and initial forces obtained through stress integration was discussed.It was found that bending normal stresses in roof flange are seriously inhomogeneous affected by local wheel pressure and shear-lag effect,and the maximum eccentric load coefficient of normal stress under offset loaded vehicle is 1.2 that is larger than the recommended 1.15.It was also shown that the proportion of bending moments and shear forces corresponding to the web under offset loaded vehicles is larger than that of symmetric vehicles,and that the maximum eccentric load coefficient of shear force is 1.8,which is far larger than recommended 1.15 and need to be addressed.