基础冲刷减小了基础对桥梁基础的约束作用, 导致桥梁基础侧向承载力降低。对于跨海大桥, 基础局部冲刷引起桥梁结构的动力效应则更加显著, 从而影响结构的安全性。本文首先计算可能的最大基础局部冲刷深度, 使模拟的基础冲刷工况符合实际工程; 其次采用m法来计算地基土体弹簧的刚度值, 建立反应基础土体对桥梁基础约束的弹性约束模型, 进而建立考虑基础冲刷桥梁有限元模型。在此基础上以琼州海峡跨海公铁两用斜拉桥作为例子, 计算分析风、浪作用下的基础冲刷对跨海斜拉桥动力效应的影响, 得到了基础局部冲刷深度对结构动力效应的影响规律。跨海斜拉桥考虑12m的最大冲刷深度引起的塔顶位移增加14. 65%, 主要原因是基础冲刷减小了基础土对桥梁基础的约束作用, 导致桥梁基础侧向承载力降低, 因此对于未做地基土处理的斜拉桥跨海桥梁结构, 应加强对基础冲刷的检测与监测或提前对基础土做好预防性维修加固处理, 以保证桥梁结构的安全运营。
The foundation scour reduces the restraining effect of the foundation on the bridge foundation, resulting in the reduction of the lateral bearing capacity of the bridge foundation. For the cross-sea bridge, the dynamic effect of foundation scour on the bridge structure is more significant, thus affecting the safety of the structure. In this paper, the maximum possible local scouring depth of the foundation is first calculated to make the simulated foundation scouring condition conform. to the actual project. Then, the m-method is adopted to calculate the stiffness value of the foundation soil spring and establish an elastic restraint model that reflects the restraint of the foundation soil on the bridge foundation, thus setting up the finite element model of the bridge with regard to the foundation scouring. On this basis, taking Qiongzhou Strait cross-sea highway and railway dual-purpose cable-stayed bridge as an example, the effect of foundation scour on the dynamic effect of cross-sea cable-stayed bridges under the action of wind and waves is analyzed, and the influence law of the local scour depth of the foundation on the dynamic effect of the structure is determined. The maximum scour depth of 12m is considered to increase the displacement of the top of the tower by 14. 65%, mainly because the foundation scours reduces the restraint effect of the foundation soil on the bridge foundation, resulting in the reduction of the lateral bearing capacity of the bridge foundation. Therefore, for the cross-sea cable-stayed bridge without foundation soil treatment, the detection and monitoring of foundation scour should be strengthened or the preventive maintenance and reinforcement treatment of foundation soil should be done in advance to ensure the safe operation of the bridge structure.