基于结构等效周期选择和谱匹配地震动记录对RC框架结构地震易损性分析的影响

Influence of seismic fragility analysis of RC frame structures under ground motion records selected and spectral matching via equivalent period of structures

选择合适的地震动记录和地震动强度指标是结构地震易损性分析的基础。首先,分别以加速度反应谱S_(a)(T_(1))值和S_(a)(T_(eq))值为强度指标选取两组地震动记录各20条,并运用谱匹配方法对其进行基于目标设计谱的匹配;其次,输入匹配前后4组地震动记录分别对一个5层和一个11层钢筋混凝土(RC)框架结构模型进行增量动力分析,进而分析谱匹配方法以及不同强度指标对最大层间位移角、结构地震易损性、最大残余层间位移角和抗倒塌储备系数的影响。分析结果表明:输入谱匹配后的两组地震动记录,结构地震易损性结果的离散性明显降低且各损伤状态下50%超越概率对应的谱加速度S_(a)(T_(1),5%)和S_(a)(T_(eq),5%)未发生明显偏差;随着结构损伤程度的增大,以S_(a)(T_(eq))为强度指标可以更有效地减小易损性分析结果的离散性;以抗倒塌储备系数为参考指标,S_(a)(T_(1),5%)作为强度指标进行地震动记录的选取有可能高估结构抗倒塌能力,应考虑以S_(a)(T_(eq),5%)为强度指标更优。

It is the fundamental issue to choose the appropriate intensity measures(IMs)and ground motion records for seismic fragility analysis of structures.First,2 suites of 20 ground motion records were respectively selected based on spectral acceleration corresponding to the fundamental period of the structure S_(a)(T_(1))and spectral acceleration corresponding to the equivalent period S_(a)(T_(eq)).And these ground motion records were spectrally matched to the targeted design spectrum.Then,incremental dynamic analysis(IDA)was respectively conducted on a 5-storeyz&11-storey reinforced concrete(RC)frame structure model under the aforementioned 4 suites of ground motion records.Influence of spectral matching method and different IMs were analyzed on maximum inter-story drift ratios(θmax)and seismic fragility analyses,maximum residual inter-story drift ratios(RIDR max)and collapse margin ratio(CMR).The analytical results indicate that under the 2 suites of spectrum-matched ground motion records,the dispersion of seismic fragility of structure was significantly reduced.And the dispersion of S_(a)(T_(1),5%)and S_(a)(T_(eq),5%)corresponding to the 50%exceedance probability for each damage state were no obvious biases.With the increase of structure damage states,S_(a)(T_(eq))as an IM can more effectively reduce the dispersion of seismic fragility analysis results.With CMR as reference indexes,selection of ground motion records with S_(a)(T_(1),5%)as an IM may overestimate the structure collapse resistance,consideration should be given to S_(a)(T_(eq),5%)for better IM.