阻尼修正条件均值谱及其在时程分析地震波选择中的应用

目前时程分析选波常采用目标谱法,即选择反应谱与目标谱有较好匹配的地震波,条件均值谱(CMS)已成为目前国内外广受关注及认可的目标谱。通常的CMS是基于5%阻尼比建立的,当结构阻尼比并非5%时,则需要对CMS进行阻尼修正。本文旨在建立1种CMS阻尼修正方法和计算公式,以便于不同阻尼比结构抗震时程分析的选波工作。以美国SAC Steel Project计划提出的针对洛杉矶地区设计的9层抗弯钢框架为场地和结构实例,建立了3种地震危险性水平(50年超越概率50%、10%和2%)下2%阻尼比的CMS目标谱,并进行了时程分析地震波选择及结构反应的计算。研究表明:提出的CMS的阻尼修正方法可不受衰减关系影响,适用的阻尼比范围(0.5%~30%)及周期范围(0.01s^10s)均较广泛,可用于各种类型的结构的抗震分析。

Selection of ground motions for structural time-history analysis based on the CMS adjusted by damping scaling factors

In recent studies, spectral matching is the most commonly proposed method for selecting earthquake records in time-history analysis of structures. The Conditional mean spectrum (CMS) has attracted widespread attention and has been used in many applications. The CMS is usually developed at a 5% viscous damping ratio. However, structural systems can have other damping ratios. This paper developed the equation of the CMS adjusted by damping scaling factors. The 9-story steel moment resisting frame structure representative of buildings in Los Angeles for the SAC Steel Project was used as the structural model. The CMS target spectra with 2% damping ratio represented seismic hazard levels with the 50%, 10%, and 2% probabilities exceeded in 50 years, were developed. The seven optimal records were selected and scaled based on the CMS with 2% damping ratio and then the structural mean dynamic responses were estimated. The method adjusting the damping ratios of the CMS has the wider ranges of damping ratios (0.5%~30%) and periods(0.01s~10s), which can be used for structures constructed with various building materials.