Insights into damping ratios in buildings

Cruz Cristian; Miranda Eduardo

摘要

This paper analyzes how soil-structure interaction affects the overall damping ratio of multistory buildings and compares theoretical results with empirical data inferred from seismic responses of buildings in California. A method is presented for obtaining effective periods and damping ratios of a replacement fixed-base multiple-degree-of-freedom structure capable of reproducing the response of a structure with a rigid, circular foundation, sitting on an elastic half-space. Sensitivity analyses are then conducted to assess the parameters influencing the soil-structure interaction. It is shown that for a given shear wave velocity of the soil, the aspect ratio is the parameter that primarily affects the effective damping ratio. For the fundamental mode, the effective damping ratio decreases approximately hyperbolically with increasing building height, causing an increment of effective damping in squatty structures, while for slender structures the effective damping ratio is reduced. These analytical results are compared with damping ratios inferred from seismic responses of buildings in California. It is shown that the variation of effective damping ratio with building height, computed analytically, closely follows the median trend of the empirical data, indicating that the reduction in damping ratios with increasing building height that has been reported in various studies is primarily due to soil-structure interaction. Finally, it is shown that effective damping ratios of higher modes increase with increasing effective modal frequency, matching the trend in empirical data. The results of this investigation are of paramount importance, as they suggest that soil-structure interaction primarily controls the overall damping ratio of buildings subjected to earthquakes.

机译：本文分析了土壤结构互动如何影响多层建筑的总体阻尼比率，并将理论结果与加利福尼亚州建筑物的地震响应推断出来的理论效果。提出了一种用于获得有效时段和阻尼比的替代固定基础的多程度自由度结构，能够再现具有刚性圆形基础的结构的响应，坐在弹性半空间上。然后进行敏感性分析以评估影响土壤结构相互作用的参数。结果表明，对于土壤的给定剪切波速度，纵横比是主要影响有效阻尼比的参数。对于基本模式，有效的阻尼比随着建筑物高度的增加而大致均匀地降低，导致蹲下结构中有效阻尼的增量，而对于细长的结构，减少了有效阻尼比。将这些分析结果与加利福尼亚州建筑物的地震反应推断出来的阻尼比率。结果表明，在分析上计算的有效阻尼比的变化与建筑物高度进行了分析，密切遵循经验数据的中值趋势，表明在各种研究中报告的建筑物高度增加的阻尼比率主要是由于土壤 - 结构相互作用。最后，表明，较高模式的有效阻尼比随着有效的模态频率的增加而增加，符合经验数据的趋势。本调查的结果至关重要，正如他们认为土壤 - 结构相互作用主要控制受地震的建筑物的总体阻尼比例。

Insights into damping ratios in buildings

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