鉛心橡膠隔震系統位移反應評估及地震歷時挑選研究

Abstract

隔震系統對於提升房屋耐震性能方面展現卓越的成果，使其成為國內外耐震設計中的重要選擇。美國太平洋地震工程研究中心(PEER)開發了建築物風險評估的架構，當中提出的變數之一為強度指標(Intensity Measure, IM)，它用以掌握地震紀錄的主要特徵，並能有效預測結構物的位移反應，然而，對於隔震結構非線性位移反應評估所適用的強度指標相關研究尚不充分。本研究的目標為驗證現有針對一般建築物常用之IM，對於評估隔震建築最大隔震位移之適用性，並探討以非線性歷時分析進行隔震設計時，地震歷時之筆數與處理方式對於隔震位移的影響。本研究使用21種參數組合（包含不同特徵強度、黏滯型阻尼器速度項指數及阻尼器提供之阻尼比）之單自由度鉛心橡膠隔震系統，將非脈衝與脈衝型地震歷時，縮放至4個地震強度等級，以單向輸入之非線性歷時分析所得結果，與各種IM建立迴歸模型，最終得出兩項理想強度指標，分別為瞬時功率IP(Teff)和譜加速度相關指標Saavg。該兩項指標皆可大幅降低預測結構反應的變異性，具備高效率。同時，以迴歸模型殘差隨地震參數變動的趨勢來檢驗其充分性。此外，本研究亦對於結合不同IM所建立的雙變量迴歸模型進行探討，期望能更完整地掌握地震對結構反應的影響。接著，本研究建立一棟15層樓隔震建築做為案例模型，以進一步探討適合隔震設計之用的地震歷時紀錄處理方式。首先，探討在多自由度系統下考慮Saavg挑選地震紀錄是否能有效降低非線性動力分析所需之地震筆數。最後，比較台灣現行耐震設計規範與美國規範對於歷時分析所使用之地震紀錄要求方面，對於推估隔震位移所產生之差異，並提出了修改建議，旨在幫助工程師減少非線性動力分析耗費的時間，並避免過度保守的設計。

Isolation systems have demonstrated exceptional effectiveness in enhancing the seismic performance of buildings, making them a significant choice in seismic design both domestically and internationally. The Pacific Earthquake Engineering Research Center (PEER) has developed a framework for building risk assessment, which includes the concept of Intensity Measure (IM),which is used to capture the primary characteristics of earthquake records and effectively predict the displacement response of structures. However, research on proper IMs for assessing the nonlinear displacement responses of isolated structures remains insufficient. This study aims to evaluate the applicability of commonly used IMs for general buildings in assessing the maximum isolation displacement of isolated buildings. Additionally, it investigated the impact of the number and processing method of earthquake records on isolation displacement when using nonlinear response-history analysis for seismic isolation design. This study employed SDOF lead-rubber-bearing systems with 21 parameter combinations, using both non-pulse and pulse-like ground motions scaled to four intensity levels. Nonlinear response-history analysis results were used to establish regression models as functions of various IMs. Two ideal intensity measures, Instantaneous Power, IP(Teff) and spectral acceleration-related measure Saavg, were identified. Both significantly reduce the variability in predicting structural responses, with regression model residuals showing no significant trends with changes in seismological parameters, demonstrating high efficiency and sufficiency. Subsequently, a 15-story isolated building was modeled as a case study to further explore the appropriate processing methods for ground motion records used in isolation design. First, it investigated whether selecting ground motions based on Saavg in MDOF system can effectively reduce the number of earthquakes required for nonlinear dynamic analysis. Finally, the study compares the requirements between Taiwan and U.S. building codes on ground-motion scaling for the design of isolation systems and evaluates their impact on the estimation of isolator displacement.