弹性和柔性地基上动力人工边界及地震动输入方法

为完善粘弹性边界在弹性地基地震动输入中的应用,并实现柔性地基的地震动输入,系统研究了弹性和柔性地基上动力人工边界及其地震动输入方法,对均质弹性地基,分析了弹簧刚度系数不同取值方法、网格尺寸和模型截断边界范围的影响,在将底边界和侧边界均设置为粘弹性边界时,现行弹簧刚度系数的不同取值方法均可行,网格尺寸应小于波长的1/20,截断边界范围不需考虑上部结构尺寸;对规则水平成层柔性地基,底边界可设置为粘弹性边界,当侧边界设置为截断自由边界时截断边界宽度应不小于地基高度的15倍,当侧边界设置为粘弹性边界时截断边界宽度应不小于地基高度的2倍。对不规则成层柔性地基,底边界可设置为粘性边界,侧边界可设置为截断自由边界,其宽度应不小于地基高度的10倍。分析表明,这些动力人工边界的设置方法可将最大相对误差控制在5%左右,满足实际工程的精度要求。

Seismic Wave Input Methods of Artificial Boundary on Elastic and Flexible Foundations

In order to improve the application of viscoelastic boundary in the vibration input of elastic foundation and realize the ground motion input of flexible foundation, the study of dynamic artificial boundary and its seismic wave input method on elastic and flexible foundations is systematically carried out. For the homogeneous elastic foundation, the effects of different values of spring stiffness coefficient, mesh size and model truncation boundary are analyzed. When the bottom boundary and the side boundary are both set to viscoelastic boundaries, the current different methods for determining the spring stiffness coefficient are feasible. The mesh size should be less than 1/20 of the wavelength, and the truncation boundary range does not need to take into account the upper structure size. For the layered flexible foundation at regular levels, the bottom boundary can be set to the viscoelastic boundary. When the side boundary is set to truncation free boundary, the width of the truncation boundary should be no less than 15 times the height of the foundation. When the side boundary is set to the viscoelastic boundary, the width of the cutoff boundary should be no less than 2 times the height of the foundation. For irregularly layered flexible foundations, the bottom boundary can be set to the viscous boundary, and the side boundary can be set to the truncation free boundary, the width of which should be no less than 10 times the height of the foundation. The above-mentioned setting methods of dynamic artificial boundary can control the maximum relative error to about 5%, and meet the requirement of engineering precision.