ABSTRACT

A vertical-to-horizontal (V/H) response spectral ratio of 2/3 is commonly adopted in earthquake engineering for assessing the magnitude of vertical motion. However, higher V/H ratios are found in some earthquake records. This study evaluates the factors that can influence the V/H ratio on the basis of vertical and horizontal site response analyses. Two sets of rock motions representing near-source and far-field conditions are propagated through four selected sites that vary in soil column thickness, groundwater table, soil type, and wave velocity profile. The V/H ratio on the ground surface is calculated and compared with that at the bedrock. Results show that the V/H ratio is amplified by the local site effect, and increases at low wave velocity and high intensity of input motion owing to the different nonlinearities presented in the vertical and horizontal directions. The groundwater table considerably varies the V/H ratio and should be considered in assessing the vertical motion or V/H ratio.

摘要

地震工程中通常采用 2/3 的垂直与水平 (V/H) 响应谱比来评估垂直运动的幅度。然而，在一些地震记录中发现了更高的 V/H 比。本研究在垂直和水平场地响应分析的基础上评估了影响 V/H 比的因素。代表近源和远场条件的两组岩石运动通过土柱厚度、地下水位、土壤类型和波速剖面不同的四个选定地点传播。计算了地表的 V/H 比，并与基岩处的 V/H 比进行了比较。结果表明，V/H比被局部场地效应放大，由于在垂直和水平方向呈现不同的非线性，在低波速和高强度输入运动时增加。地下水位显着地改变了 V/H 比，在评估垂直运动或 V/H 比时应予以考虑。