考虑双向地震激励的标准化地震输入能量反应谱研究

以往地震输入能量谱的研究几乎都是以单自由度体系和单向地震输入为前提, 没有考虑地震动的多维性和结构非线性反应的空间耦合性。于是, 建立单质点双自由度体系, 假设体系的弹塑性关系为满足二维屈服面函数的理想弹塑性形式, 基于此模型提出双向地震动作用下标准化的地震输入能量反应谱理论。以硬土、中硬(软)土和软土三类场的地震记录作为体系的双向激励, 建立统计平均的等延性系数标准化地震输入能量谱。分析场地类别、延性系数、两水平主轴方向周期比对标准化地震输入能量谱的影响。分析表明：各类场地分别具有独自的谱形特征和规律性;延性系数对硬土场地和中硬(软)土场地的谱值影响较明显, 而对于软土场地, 除长周期外影响很小;周期比 ζ 对谱值具有一定影响;基于单自由度体系建立的输入能量谱在某些情况下会高估能量反应。

STUDY ON STANDARD EARTHQUAKE INPUT ENERGY SPECTRUM FOR BI-DIRECTIONAL EARTHQUAKE EXCITATIONS

Traditional studies on earthquake input energy spectra are based on the theory of single degree of freedom system (SDOF) subjected to single directional earthquake excitations, in which the multi-dimensionality of earthquake excitations and the coupling of non-linear structural responses are not considered. In this study, a single-mass dual-degree of freedom system subjected to bi-directional earthquake excitations is proposed. The two-dimensional yield surface elasto-plasticity theory is enforced. The standard earthquake input energy spectrum under bi-directional earthquake excitations is presented. The statistical average spectra are established based on strong earthquake motion records for hard, medium and soft soil sites, respectively. The influences of the soil site, ductility factor and the period ratio on average spectra are analyzed. Results indicate that standard earthquake input energy spectra for each soil site show different characteristics. The influences of the ductility factor on spectra are obvious in hard and medium soil sites, but are not as significante in soft soil sites, excluding with long periods. The period ratio is also found to impose centain effects on the spectra. In some instances, the earthquake input energy responses are found to be overestimated when the SDOF system is adopted.