考虑桩土作用的高墩大跨连续结构几何非线性效应分析

Analysis on Geometric Nonlinear Effect of High-pier and Long-span Continuous Structure Considering Pile-soil Interaction

在迅速崛起的西部高原山区高墩大跨桥梁多以百米左右的高墩大跨连续刚构桥为主,其几何非线性问题变得越来越重要。为了研究桩土作用下该结构的几何非线性效应,以西部某高墩大跨连续刚构桥为依托工程,利用大型有限元软件进行了考虑桩土效应的几何非线性施工全过程模拟。对比分析了该类型桥梁在桩土作用下几何非线性效应对结构应力和位移在施工阶段及成桥后的影响程度,并研究了不同墩高情况下几何非线性效应对该类型桥梁的变形及结构内力的影响规律。分析结果表明:几何非线性效应对主梁断面顶、底板应力的影响随着悬臂长度的增加而逐渐增大;考虑比不考虑几何非线性效应的主梁竖向位移值小,且位移曲线平顺连续;几何非线性效应对主梁弯矩和主墩剪力影响较大,且剪力分布的非线性随墩身高度的增加而明显,呈先增大后减小的现象;几何非线性效应对边跨主梁弯矩的影响效应随墩高的增加而减小,对墩顶及中跨主梁弯矩的影响随墩高的增加而增大。为了更好地控制结构应力及线形,建议高墩大跨连续结构在设计及施工控制中应着重计入几何非线性效应的影响。

The high-pier and long-span bridges in the west plateau mountainous area have been constructed rapidly, most of them are long-span continuous rigid frame bridges of 100 meters or so, and their geometric nonlinearity is becoming more and more important. In order to study the geometric nonlinear effect of the structure under pile-soil interaction, based on the project of a high-pier and long-span continuous rigid frame bridge in western China, its whole geometric nonlinearity constuction process is simulated by using a large finite element software, the influence degrees of geometric nonlinear effect on the structural stress and displacement of this type of bridge at construction stage and after completion under pile-soil interaction are comparatively analysed, and the influence rules of geometric nonlinear effect on the stress and displacement of this type of bridge with different pier hights are studied. The analysis result shows that （ 1 ） the influence of geometric nonlinear effect on the stresses in the top and bottom slabs of the main girder increases with the increase of cantilever length; （2） the vertical displacement of the main girder considering the geometric nonlinear effect is smaller than that without considering the geometric nonlinear effect, and the displacement curve is smooth and continuous ; （ 3 ） the influence of geometric nonlinear effect on the bending moment of the main girder and shear force of the main pier is greater, the nonlinearity of the shear force distribution is obvious, it increases at first and then decreases with the increase of pier height; （4） the influence of geometric nonlinear effect on the bending moment of the main girder at side span decreases as pier height increases, its influence on the bending moments of the main girder at pie top and central span increases as pier height increases. In order to better control the structural stress and geometric shape, it is suggested that the influence of geometric nonlinear effect should be considered in the design and construction control of high- pier and long-span continuous structures.