罕遇地震下RC框架结构最大弹塑性层间位移的实用计算方法

ESTIMATION OF SEISMIC STORY DRIFTS IN RC FRAME STRUCTURES SUBJECTED TO SEVERE EARTHQUAKES

准确预测罕遇地震下结构的最大弹塑性层间位移,是基于性能抗震设计的重要内容。该文针对一阶振型占主导的中低层RC框架结构,首先引入一种能简便有效判断是否能形成整体型屈服机制方法,降低RC框架结构出现薄弱层失效的可能性,减小由此所可能导致的弹塑性地震响应的离散性。然后在此基础上,基于一系列合理的假设,提出了针对具有整体型屈服机制RC框架结构的最大弹塑性层间位移及其均方差的预测方法,给出了预测公式和分析流程。与弹塑性时程统计分析结果对比表明,该文建议方法简便易用,给出的预测值与时程分析结果统计值的均值和方差都符合良好,可作为罕遇地震下RC框架结构最大层间位移计算的实用方法。

Accurately predicting the maximum story drift of structures is the most important content of performance based aseismic design. However, a predicting method that is both simple and effective is currently lacked. In this work, aiming at the low storey reinforced concrete(RC) frames for which the first mode is predominant, a methodology is proposed to determine whether the structure will perform a global failure mode, by which the large dispersion in elasto-plastic analysis due to the soft-story failure mode is avoided. Then, based on a series of rational assumptions, the method to predict the maximum story drifts and the corresponding deviations of RC frames with global failure modes is proposed. The equations and analytical procedures are suggested. Finally, by comparing with the statistic results of elasto-plastic time-history analyses, the predictions using the proposed method agree well with the time-history results, both on average values and on deviations. Hence, the proposed method can be used to predict the maximum story drift of RC frames subjected to severe earthquakes.