The main objective of this study is to investigate the effect of spectral shape on damping modification factors η used in equivalent static and response spectrum analyses of structures with damping ratios that are different from 5% critical damping. Record-to-record variability of η is also evaluated through a statistical analysis of 5270 ground motions records from 1137 interface earthquakes recorded in Chile. The effect of spectral shape is studied using recently developed spectral shape metrics SaRatio and epsilon ( ε ) and evaluating their use as possible predictors for η. Similarly to previous investigations, this article also examines the effect of oscillator period, earthquake magnitude, and earthquake duration for different levels of damping ratio. Results suggest that SaRatio is an effective predictor of η, particularly for highly damped structures. However, results also indicate that for rock and firm sites, earthquake faulting mechanism and site class do not have a significant influence on η. A simple period-independent regression model for η as a function of SaRatio and damping ratio is proposed. A comparison between median η from this study and those in current Chilean seismic codes shows that code factors are unconservative.

中文翻译：

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谱形对阻尼修正因子的影响

本研究的主要目的是研究谱形状对阻尼修正系数 η 的影响，该系数用于阻尼比不同于 5% 临界阻尼的结构的等效静力和响应谱分析。还通过对智利记录的 1137 次界面地震的 5270 次地面运动记录的统计分析来评估 η 的记录间变异性。使用最近开发的光谱形状度量 SaRatio 和 epsilon ( ε ) 研究光谱形状的影响，并评估它们作为 η 的可能预测因子的用途。与之前的研究类似，本文还研究了振荡器周期、地震震级和地震持续时间对不同阻尼比水平的影响。结果表明 SaRatio 是 η 的有效预测因子，特别是对于高阻尼结构。然而，结果也表明，对于岩石和坚固场地，地震断裂机制和场地等级对 η 没有显着影响。提出了作为 SaRatio 和阻尼比函数的 η 的简单周期无关回归模型。本研究的中值 η 与当前智利地震代码中的中值之间的比较表明，代码因子是不保守的。