四种地下结构抗震设计简化分析方法对比

在地下结构抗震设计简化分析方法中，强制反应位移法将土层变形施加在有限元模型侧边界模拟地震作用，反应加速度法将土层加速度施加到整个有限元模型上模拟地震作用，此外还有仅将土层加速度施加到土层模型上模拟地震作用的方法。上述方法均规避了反应位移法中关于弹簧刚度的取值问题，提高了计算效率。本文以1个双跨箱形结构为例，用动力时程分析的计算结果作为校核，分析了强制反应位移法、反应加速度法和仅将土层加速度施加到土体中的简化分析方法在不同侧边距条件下的计算精度，再结合常用的反应位移法，对比分析了4种简化分析方法的误差。分析结果表明:使用强制反应位移法时，侧边距取为1倍结构宽度导致的误差最小，反应加速度法和仅在土体施加加速度的简化方法对侧边距取值不敏感，反应位移法在角点造成的误差最大。

Comparison of Four Simplified Analytical Methods for Seismic Design of Underground Structures

The theoretical basis of the simplified analytical method for seismic design of underground structure is that the deformation of underground structure depends on the deformation of foundation soil during earthquake, which fails to reflect the dynamic characteristics of the structure. Based on the most commonly used seismic displacement method, three kinds of simplified analytical methods are discussed in this paper. The forced displacement method is by applying the ground deformation to the boundary of the soil finite element model to simulate seismic load. The response acceleration method is by applying the ground acceleration to the integral finite element model to simulate seismic load. The third method is only by applying the ground acceleration to the soil finite element model to simulate seismic load. The above three simplified analytical methods can avoid calculating the value of the spring stiffness and improve the computational efficiency. Taking a double-span box structure as example, the calculations by applying three kinds of simplified analytical methods above with different lateral margins are carried out, and the analysis results are verified with the results of the dynamic time history method to calculate precisions. Combined with seismic displacement method, the error of four kinds of the simplified analytical methods is compared. The results show that the lateral margin should be equal to structure width when using the forced displacement method, and the response acceleration method and the method with only soil acceleration are not sensitive to the value of the lateral margin, and the error caused by the seismic displacement method reaches the maximum at the corner.