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

Impact of Near-Fault Ground Motions on the Efficiency of Passive Control Systems: Single Degree of Freedom System

劉家仁(Chia-Ren Liu)

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(2015年)

https://doi.org/10.6342/NTU.2015.01253

摘要

被動控制元件被運用來提高結構的耐震能力，以維護主結構的使用性與安全性。對於遠域地震，被動控制元件已經被研究以及測試，並證明能夠有效的發揮作用，達到提高結構耐震能力的目標；然而過去近斷層地震紀錄不若現在豐富，因此裝設被動控制元件之結構受近斷層地震之影響，仍無法被定量、有系統的分析而得到結論。近斷層地震與遠域地震不同之處，在於其地表速度歷時中，具有一明顯長週期之速度脈衝週期，地震能量在短時間內輸入結構之內。而被動控制元件，主要分為隔震與減震兩大範疇。對於隔震結構，由於位移集中在隔震器上，近斷層速度脈衝會造成隔震器產生過大的位移，導致隔震器破壞，甚至使上部結構有傾覆；對於減震結構，由於近斷層地震大部分能量在短時間內輸入結構，減震元件能否發揮在遠域地震作用下同樣的效果，有待進一步研究。
本研究使用單自由度系統，以數值分析的方式模擬近斷層地震作用下，隔減震結構之影響。在隔震結構方面，本研究針對鉛心橡膠隔震器進行探討；在減震結構方面，則針對加裝液態黏性阻尼器之彈性構架作為代表。評估隔減震系統在近斷層地震作用下之效益，是以近斷層地震歷時中所擷取出脈衝之週期，與結構物本身之自然週期的比值作為變數，來探討對結構反應的影響。
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，應是影響結構物最大反應的重要參數。在減震系統方面，當結構物週期與近斷層脈衝週期之比值靠近1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，阻尼器反而會使加速度反應被放大。對於隔震系統，當等效週期與脈衝週期之比值等於1時，位移反應會被放大。在已知脈衝週期的情況，本研究提出了評估隔減震結構之建議公式，以有效掌握隔減震結構在近斷層地震作用下之反應。
關鍵字:近斷層、近斷層脈衝週期、被動控制、液態黏性阻尼器、鉛心橡膠隔震支承

關鍵字

近斷層 ； 近斷層脈衝週期 ； 被動控制 ； 液態黏性阻尼器 ； 鉛心橡膠隔震支承

並列摘要

ABSTRACT
Passive control systems are used to improve seismic capacity of the structure and maintain the function and security of the main structure during an earthquake. In the far-fault region, passive control systems have been studied and proven to be an effective way to improve structural seismic capacity; however, the past record of near-fault earthquake is not as rich now, the advantage of structure equipped passive control elements cannot be estimated quantifiably subject near-fault earthquake.
The difference between near-fault and far-fault earthquake is that near-fault record has a long period and pulse-like signal in velocity record. Seismic energy input structure in a very short time with pulse-like signal. The passive control systems are divided into two categories, isolation systems and damping systems. For the isolated structure, the displacement of isolator may be too large to control and leads isolator damage subject near-fault earthquake. For the damping structure, the input energy apply in the structure instantly. Whether the dampers can dissipate energy as good as far-fault region is a problem.
In this study, single degree of freedom system is adopted to analyze the impact of near-fault ground motions on the efficiency of passive control systems. In the isolated systems, the study focus on lead rubber isolators ; in damping system, the elastic framework equipped liquid viscous dampers is adopted.
The results is that the ratio of near-fault pulse period(Tp) and structure natural period is an important parameter of the maximum response. In the damping system, when the ratio is close to 1, the reduction of displacement and acceleration is the most effective than other ratio. When the structure natural period is much larger than the near-fault pulse period, the acceleration response will be magnified . For the isolation systems, when the ratio of the equivalent period and near-fault pulse period is about 1, the displacement reaction may be amplified than predict.
Seismic assessment of passive control system have been proposed in this study when near-fault pulse period is known.
Keywords: near-fault, near-fault pulse period, passive control, liquid viscous dampers, lead rubber bearing

並列關鍵字

near-fault ； near-fault pulse period ； passive control ； liquid viscous dampers ； lead rubber bearing

參考文獻

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