地震歷時調整縮放與挑選之研究

A Study of Selection and Scaling of Ground Motions for Structural Response History Analysis

謝采洵(Tsai-Hsun Hsieh)

指導教授 ： 蔡克銓

國立臺灣大學/工學院/土木工程學研究所/碩士(2012年)

https://doi.org/10.6342/NTU.2012.00040

摘要

結構動力歷時分析可提供較詳細之耐震性能評估結果，於高層建築、特殊構造建築及不規則建築經常被使用，本研究分別針對地震歷時之調整縮放及挑選進行探討。
平面不對稱之結構具有平面扭轉之效應，須進行三維動力歷時分析方能探討其平面扭轉之效應。本研究提出用於三維結構分析之多振態調整法，此方法適切考慮前幾振態之效應，分別使用不同權重係數考慮各振態之貢獻，再運用最小平方誤差法進而計算各地震歷時之調整縮放倍率，使自然地震反應譜與平滑化設計反應譜的效應在所考慮的主要振態更為相近。多振態調整法又分成以基底剪力或頂層位移為設計檢核參數兩種（MMSV法或MMSD法）。本研究透過一棟二十層平面不對稱結構進行反應譜動力分析及動力歷時分析，並與其他常見之調整縮放方法進行比較；彈性分析中，經MMSV法調整後進行動力分析所得樓層剪力及層間側位移角需求最近似於平滑化設計反應譜所期望之需求；經MMSD法調整後則對於樓層側位移及樓層旋轉角與平滑化設計反應譜所期望之需求較為接近；當結構物明顯進入非彈性時，使用MMSV法調整後之地震歷時進行動力歷時分析，在樓層剪力、層間側位移角、樓層側位移及樓層旋轉角皆較其他方法更接近平滑化設計反應譜所期望之需求。
針對地震歷時挑選部分，本研究先利用多振態挑選法定義反應譜差異因子，於不同振態給以不同之權重係數並正規化，挑選在前幾振態與平滑化設計反應譜最為相近之自然地震反應譜，本研究分別針對二維及三維結構分析進行探討，探討挑選後之自然地震反應譜與目標反應譜相似程度，並研究動力歷時分析後所得結構受震反應可否達成目標反應譜期望之值，經研究發現，以頂層位移為設計檢核參數之多振態挑選法及習見方法挑選之自然地震反應譜與目標反應譜較為相近，且進行動力歷時分析所得之受震反應亦與目標反應譜所期望之需求較為相近。第二部份探討正規化及權重對於反應譜差異因子之影響，結構為彈性反應時的判定範圍考慮0.2T1至T1（T1：結構第一振態週期），結構若進行非彈性反應則考慮0.2T1至1.5T1，本研究分別針對短中長三個不同之第一振態週期的結構進行地震歷時挑選，並以一棟二十層平面對稱結構進行動力歷時分析；經研究發現，針對反應譜差異因子進行正規化或權重修正，挑選後之自然地震反應譜與目標反應譜相似程度並無一致之趨勢，唯無論是否進行正規化或考慮權重皆在反應譜匹配程度上有相當不錯的結果；動力歷時分析結果則顯示未針對反應譜差異因子進行正規化或考慮權重之修正，其結構受震反應與目標反應譜期望之需求較為接近。

關鍵字

地震調整 ； 地震選取 ； 多振態調整法 ； 調整倍率 ； 動力歷時分析 ； 反應譜差異因子 ； 多振態挑選法

並列摘要

Nonlinear response history analysis (NLRHA) has become a frequently used procedure for the seismic demand evaluation for tall or irregular buildings. This study consists of two parts: ground motion scaling and ground motion selection.
Bi-directional response history analyses (RHA) are adopted so that the torsional effects in the two-way asymmetric-plan buildings are included. This research investigates a multi-mode ground motion scaling (MMS) method in which the dynamic properties of the first few vibration modes are incorporated. The method considers the complete quadratic combination (CQC) rule in computing the scale factor and peak seismic demands in each of the two principal building axes. Multi-mode ground motion scaling method is divided into two approaches. One is the MMSV (base shear is chosen as the key design parameter) and the other is MMSD (roof displacement is chosen as the key design parameter). Using a 20-story two-way asymmetric-plan building, this study compares the effectiveness of the MMSV, MMSD with other common scaling procedures. It is illustrated that the MMS method is effective in reducing the scatter in the peak seismic demands computed from both the bi-directional RHA and response spectrum analysis (RSA). The MMSV method performs well in reducing the scatter of elastic shear force and inter-story drift demand estimates, while MMSD performs well in floor displacement and floor rotation demand estimates. For the inelastic building responses, MMSV provide rather good results in reducing the scatter of the peak seismic demands.
For the NLRHA, it often requires the selection of input ground motions to represent the effects of the target response spectrum. In this study, the sum of squared errors (SSE) is used to determine the degree of the matching between the spectra. This study first applies multi-mode selection method, considers different weighting factors for different modes in calculating the SSE. It is demonstrated that MMSD (multi-mode selection method using roof displacement as the key design parameter) and common method perform well in spectrum matching and NLRHA for both 2-D and 3-D structural analyses. The second part of the research on ground motion selection is about the further modifications of the SSE. The SSEs are modified by weighting factors or normalization. It is found that the modified SSE using weighting factors or normalized shows little effect in both spectrum matching and reducing the scatter of the seismic response estimates.

並列關鍵字

earthquake selection ； earthquake scaling ； multi-mode scaling ； scale factor ； response history analysis ； the sum of squared errors ； multi-mode selection.

參考文獻

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