弯梁桥中V-T联合受荷桩承载力分析

Bearing Capacity Analysis of V-T Combined Loaded Piles in Curved Girder Bridges

为探讨弯梁桥中基桩在竖向力V和扭矩T共同作用下的受力特性,考虑土体剪切模量和桩侧极限摩阻力沿深度线性增加(Gibson地基),并计入加载路径和桩-土接触面位移非协调性的影响,基于桩身荷载传递函数和剪切位移法建立桩身位移控制方程,引入相应的力和位移边界条件后,导出桩周土处于不同受力状态时的桩身内力位移解析解,由此求得不同加载路径下V-T联合受荷桩的承载力,进而获得桩身承载力包络图。研究结果表明:对于V-T联合受荷桩,桩身承载力随长径比增加而增加,但随桩侧土体剪切模量与极限摩阻力分布常数之比和桩土刚度比的增大而逐渐减小;桩顶可承受的竖向力随扭矩增加不断减小而趋于0,且V→T承载力包络线始终处于T→V承载力包络线外侧。

To discuss the mechanic behavior of piles in curved girder bridges under combined loading of vertical force Vand torsion T,the control equation of pile displacement was first set up by the pile shaft load transfer function and shear displacement method,in which the increase of soil shear modulus and ultimate shaft friction along with deep line（Gibson subsoil）was considered,and loading paths and non-coordination deformation along the pile-soil interface were considered as well. The corresponding force and displacement boundary conditions were introduced to deduce the analytical solution for the inner force displacement of pile shaft under various bearing stages of subsoil.Based on the obtained solution,the bearing capacity of loaded pile was obtained under various loading paths of V-T,from which failure envelopes were plotted correspondingly.The results show that for V-Tcombined loaded piles,the bearing capacity will increase with the increase of aspect ratio,while decrease with the increase of the ratio of the constant coefficient of the subsoil shear modulus distribution function to that of the ultimate friction resistance distribution function,and stiffness ratio of pile shaft to subsoil.To increase the value of torsion at the pile top will result in a decreasing vertical bearing capacity with a final zero value.Furthermore,the failure envelopes under V→Tloading path remains outside of that under T→Vloading path.