SV波斜入射下Nam Ngum 5拱坝-库水-地基系统的地震响应分析

Seismic response analysis of Nam Ngum 5 arch dam-reservoir water-foundation system under oblique incidence of SV waves

基于黏弹性人工边界与相应地震动输入方法,推导了任意角度下三维SV波斜入射时的等效节点荷载,构建了考虑地震波斜入射的三维黏弹性静-动力统一人工边界,探究了三维情况下混凝土拱坝在地震波斜入射时的地震动响应,应用于Nam Ngum 5重力拱坝-库水-地基系统的地震响应分析中。研究结果表明:当SV波斜入射角度逐渐增大时,坝体关键点的顺河向位移、主应力以及动水压力峰值均呈现逐渐增大的趋势,横河向位移呈现逐渐减小的趋势;其中25°与0°入射相比,坝顶点顺河向位移从0增加至0.15 m,横河向位移影响较小仅减小0.011 m;坝踵点、坝趾点主应力与斜入射角度存在明显差异,当入射角度为25°时,主拉应力与主压应力峰值相较于垂直入射分别增加了1.41 MPa与3 MPa;坝踵处动水压力峰值也在入射角度为25°时达到最大为0.33 MPa与-0.29 MPa;需要在类似实际工程设计中应考虑地震波斜入射的影响。

Based on the viscous-spring artificial boundary and corresponding ground motion input method,the equivalent nodal load of 3D SV wave with oblique incidence at any angle is derived.A three-dimensional viscous-spring static-dynamic unified artificial boundary is constructed considering the oblique incidence of seismic waves.The seismic response of the concrete arch dam under the oblique incidence of seismic waves in three-dimensional condition is explored,and it is applied to the seismic response analysis of the Nam Ngum 5 gravity arch dam-reservoir water-foundation system.The results show that when the oblique incident angle of the SV wave increases gradually,the displacement along the river,the principal stress,and the peak value of the hydrodynamic pressure of the key points of the dam body show a gradually increasing trend,and the displacement across the river shows a decreasing trend.Among them,when the incidence of 25°is compared with that of 0°,the displacement of the dam apex along the river increases from zero to 0.15 m,and the displacement across the river has little effect and only decreases by 0.011 m.There are obvious differences between the principal stress and the oblique incident angle at the dam heel and dam toe.When the incident angle is 25°,the peak values of the principal tensile stress and the principal compressive stress increase by 1.41 MPa and 3 MPa,respectively,compared with the normal incidence.The peak value of hydrodynamic pressure at the dam heel also reaches the maximum of 0.33 MPa and-0.29 MPa when the incident angle is 25°.It is very necessary to consider the effect of oblique incidence of seismic waves in similar practical engineering design.