摩擦單擺隔震系統受脈衝型地震作用之評估與設計

Design of Frictional Pendulum (FP) Bearing Systems Subjected to Pulse-Like Ground Motions

楊亞衡(Ya-Heng Yang)

指導教授 ： 黃尹男

國立臺灣大學/工學院/土木工程學研究所/碩士(2019年)

https://doi.org/10.6342/NTU201902642

摘要

脈衝型地震動在其地震歷時中可以觀察到明顯的脈衝特性，對於長周期結構系統，此一地震動特性可能提高結構之設計需求並造成嚴重的結構損壞。因此，為確保結構系統在脈衝型地震動作用下的安全性，將脈衝型地震動特性納入現行耐震設計與耐震評估方法有其必要性。
本研究探討摩擦單擺支承系統(Friction-pendulum bearing system)受脈衝型地震動作用下的耐震設計與耐震評估。其中，對於隔震系統之等效側力設計流程(Equivalent lateral force procedure)為探討重點之一。此外，在脈衝型地震動作用下，美國太平洋地震工程研究中心 (the Pacific Earthquake Engineering Research, PEER) 所提供之耐震評估方法中，地震動強度(intensity measure, IM)對於結構反應之預測能力，亦是探討之重點。
本研究建立一個脈衝型地動資料庫，並建立摩擦單擺支承系統的非線性動力歷時模型，模擬之結果作為討論耐震設計與評估之基準。隔震系統之等效側力設計流程在脈衝型地震動作用下的探討，分成三大部分：(1)反應譜形之影響、(2)阻尼折減係數以及(3)等效線性系統之假設。依據探討之結果，本研究建議阻尼折減係數與等效阻尼比應考量脈衝型地震動之特性，其中，所建議之修正阻尼折減係數與與等效阻尼比均考量正規化週期比(結構物自然週期與脈衝型地震動之脈衝週期的比值)。另一方面，本研究亦建議，依照修正後之等效側力設計流程所計算之隔震位移可做為耐震評估中的地震動強度，對於摩擦單擺支承系統之水平隔震位移有良好的預測能力。

關鍵字

摩擦單擺 ； 隔震 ； 近斷層 ； 脈衝型地震動 ； 阻尼折減係數 ； 等效線性 ； 地震動強度 ； 易損性分析

並列摘要

Pulse-like ground motions are characterized by containing dominant pulses in ground-motion time series. Such ground motions have a higher potential to produce severe damages and large structural demands for long-period structural systems. Therefore, it is vital to account for this pulse-like effect in current seismic codes to ensure the safety of the systems.
This thesis provides an evaluation for the design and seismic assessment of friction-pendulum (FP) bearing systems when subjected to pulse-like ground motions. The equivalent lateral force procedure for the design of FP-bearing systems was evaluated. The predictive capacity of intensity measures (IM), which is one of the key parameters in the Pacific Earthquake Engineering Research (PEER) seismic risk assessment methodology, to structural responses under the influence of pulse-like ground motions was also investigated in the thesis.
A pulse-like ground motion database was compiled and the results of nonlinear dynamic analysis for FP-bearing systems was presented and used as a benchmark to evaluate the efficacy of the equivalent lateral force procedure as well as the predictive capacity of investigated IMs. The efficacy of the equivalent lateral force procedure for the cases subjected to pulse-like ground motions was evaluated from three aspects: the influence of spectral shape, damping reduction factor, and the equivalent linear method. Based on the analysis results, the study proposed modification for damping reduction factor and equivalent damping ratio to account for the pulse-like effect. The predictive results using the proposed equivalent approach were also utilized as an alternative IMs to estimate isolation displacements.

並列關鍵字

Friction Pendulum ； isolation ； near fault ； pulse-like ground motion ； damping reduction factor ； equivalent linear ； intensity measure ； fragility analysis

參考文獻

AASHTO. (1999). Guide Specifications for Seismic Isolation Design. Washington, DC.

AASHTO. (2010). Guide Specifications for Seismic Isolation Design. Washington, DC.

Abrahamson, N. A. (2000, March). Near-fault ground motions from the 1999 Chi-Chi earthquake. In Proceedings of US–Japan workshop on the effects of near-field earthquake shaking. San Francisco, California (pp. 20-21).

Agrawal, A. K., & He, W. L. (2002, January). A close-form approximation of near-fault ground motion pulses for flexible structures. ASCE Engineering Mechanics Conference.

Akkar, S., Yazgan, U., & Gülkan, P. (2005). Drift estimates in frame buildings subjected to near-fault ground motions. Journal of Structural Engineering, 131(7), 1014-1024.