近斷層地震對結構減震系統效益之影響研究

Impact of Near-Fault Ground Motions on the Responses of Building Equipped with Viscous Damping Systems

游豐碩(Fong-Shou Yu)

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(2016年)

https://doi.org/10.6342/NTU201601971

摘要

結構物之耐震性能提升一般仰賴於被動控制元件，最常見之元件即是安裝黏性阻尼器，以降低結構物受震時的反應。而對於此類結構之設計，必須優先評估其最大之反應，才能對各種梁柱系統進行細部設計，因此規範建議由工址設計反應譜(阻尼比5%之設計反應譜)出發，並對於整體阻尼比異於5%之結構提供阻尼折減係數，來估算結構物之最大反應。在規範之中提供的阻尼折減係數，是由遠域斷層地震之分析所得，因此對於近斷層地震之適用性有待探討。另外，過去對於近斷層地震資料的了解尚不夠充足，對於遠域與近域的分類也不夠完善，因此探討近斷層地震對阻尼折減係數之影響有相當的難度。
本研究由單自由度出發，以近來新文獻所提供分類近斷層地震之方法篩選近斷層地震紀錄，並以數值分析的方式模擬其對於安裝黏性阻尼器之影響，並提出阻尼折減係數之建議公式。同時，一般結構物為多自由度系統，因此本研究將提出之建議公式結合反應譜分析，推廣至多自由度系統，並對三棟案例結構物(三層樓、九層樓、二十層樓)，進行反應最大值估計，並與SAP2000比較。
本研究結果指出，近斷層脈衝週期與結構物自然週期之比值，是影響結構反應的重要參數。不論為安裝線性或非線性阻尼器，對於結構物週期約等於近斷層脈衝週期時，阻尼器對於位移與加速度的折減效果最為顯著；而當結構物週期遠大於近斷層脈衝週期時，阻尼器會使加速度反應放大、位移反應趨近於最大地表位移。對於提供之阻尼折減係數建議公式應用於多自由度結構，對於線性黏性阻尼器而言，會有可接受的評估效果；而對於非線性黏性阻尼器而言，需要再次修正，才能使評估之最大位移趨於準確或保守。

關鍵字

近斷層地震 ； 速度脈衝 ； 脈衝週期 ； 被動控制 ； 液態黏性阻尼器

並列摘要

Passive control systems have been widely used to minimize responses of structures subjected to ground shaking. Among others, fluid viscous dampers (FVDs), including linear and nonlinear types, are one of the most popular passive control systems. The design of FVD system for structures often involves damping reduction factor (a.k.a. B factor), which is the ratio of structural response (acceleration, velocity, or displacement) for a damping ratio of 5% to that of a damping ratio other than 5%. The B factors provided in current building codes were developed based on results of research using far-fault ground motions. The applicability of those factors for near-fault ground motions requires more research.
The research presented in this thesis includes two parts. In the first part, a series of response-history analysis were conducted using single degree of freedom (SDOF) systems and 200+ pulse-like near-fault ground-motion records identified from NGA-West 2 strong-motion database. The B factors appropriate for the design of FVD systems subjected to near-fault ground motions are proposed. In the second part, the application of the proposed B factors on multiple degree of freedom (MDOF) systems was evaluated using 3-, 9-, and 20-story buildings.
The results show that the ratio of pulse period of near-fault ground motion to the natural period of a structure is an important parameter for the B values. When the ratio is close to 1, FVD system is more effective in reducing displacement and acceleration responses. The peak responses of MDOF systems equipped with linear FVD system can be well-predicted using typical response spectrum analysis and the B values proposed in the first part of this thesis. However, the procedures (i.e., response spectrum analysis together with the proposed B values) need to be modified to predict the peak responses of structures equipped with nonlinear FVD systems.

並列關鍵字

near-fault ground motion ； velocity pulse ； pulse period ； damping reduction factor ； structural passive control ； fluid viscous damper

參考文獻

劉家仁 (2015). "近斷層地震對結構隔減震系統效益之影響研究:單自由度系統." 臺灣大學.

曾惠瑜 (2014). "使用非線性黏性阻尼器之彈性結構受近斷層地震作用之分析與設計研究."

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Bertero, V. V., Mahin, S. A., and Herrera, R. A. (1978). "Aseismic design implications of near-fault san fernando earthquake records." Earthquake Engineering & Structural Dynamics, 6(1), 31-42.

Bray, J. D., and Rodriguez-Marek, A. (2004). "Characterization of forward-directivity ground motions in the near-fault region." Soil Dynamics and Earthquake Engineering, 24(11), 815-828.