Funding information Onassis Foundation; Imperial College London Summary The seismic collapse capacity of ductile single-degree-of-freedom systems vulnerable to P-Δ effects is investigated by examining the respective influence of ground motion duration and acceleration pulses. The main objective is to provide simple relationships for predicting the duration-dependent collapse capacity of modern ductile systems. A novel procedure is proposed for modifying spectrally equivalent records, such that they are also equivalent in terms of pulses. The effect of duration is firstly assessed, without accounting for pulses, by assembling 101 pairs of long and short records with equivalent spectral response. The systems considered exhibit a trilinear backbone curve with an elastic, hardening and negative stiffness segment. The parameters investigated include the period, negative stiffness slope, ductility and strain hardening, for both bilinear and pinching hysteretic models. Incremental dynamic analysis is employed to determine collapse capacities and derive design collapse capacity spectra. It is shown that up to 60% reduction in collapse capacity can occur due to duration effects for flexible bilinear systems subjected to low levels of PΔ. A comparative evaluation of intensity measures that account for spectral shape, duration or pulses, is also presented. The influence of pulses, quantified through incremental velocity, is then explicitly considered to modify the long records, such that their pulse distribution matches that of their short spectrally equivalent counterparts. The results show the need to account for pulse effects in order to achieve unbiased estimation of the role of duration in flexible ductile systems, as it can influence the duration-induced reduction in collapse capacity by more than 20%.

中文翻译：

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地震动持续时间和脉冲效应在延性系统坍塌中的作用

资金信息奥纳西斯基金会；伦敦帝国理工学院 总结 通过检查地震动持续时间和加速度脉冲的各自影响，研究了易受 P-Δ 效应影响的延性单自由度系统的地震倒塌能力。主要目标是提供简单的关系来预测现代延性系统的持续时间相关的倒塌能力。提出了一种新的程序来修改光谱等效记录，使它们在脉冲方面也等效。在不考虑脉冲的情况下，首先通过组合 101 对具有等效光谱响应的长短记录来评估持续时间的影响。所考虑的系统表现出具有弹性、硬化和负刚度段的三线主干曲线。研究的参数包括周期、负刚度斜率、延展性和应变硬化，适用于双线性和收缩滞后模型。增量动态分析用于确定坍塌能力并导出设计坍塌能力谱。结果表明，由于承受低 PΔ 水平的柔性双线性系统的持续时间效应，倒塌能力可能会降低 60%。还介绍了考虑光谱形状、持续时间或脉冲的强度测量的比较评估。然后，通过增量速度量化的脉冲影响被明确考虑以修改长记录，使其脉冲分布与其短光谱等效对应物的脉冲分布相匹配。