臺灣地震紀錄垂直向與水平向加速度反應譜譜值比之研究

Analysis of Vertical-to-Horizontal Spectral Acceleration Ratios for Shallow Crustal Ground-Motion Records in Taiwan

邱莉珺(Li-Chun Chiu)

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/NTU201600787

摘要

抗震設計目前的做法主要是基於水平方向地表加速度歷時對結構物的影響做設計，但垂直方向的地表運動對某些類型的結構之耐震反應與安全與否仍然很重要，例如對軸力二次效應敏感之結構、房屋樓板、隔震系統（水平勁度、傾覆位移與軸力有關）等。在建立垂直向之設計反應譜時，使用垂直方向與水平方向的加速度反應譜譜值比(V/H)與水平方向反應譜來建立垂直方向反應譜，是建立垂直向反應譜可行的方法。許多耐震規範（如IBC及ASCE 7-10）將設計上使用之V/H定為2/3，但是在歷史之強震資料中，發現V/H值有超越2/3的可能。本研究針對臺灣強震歷時紀錄之垂直向與水平向加速度反應譜譜值比V/H進行探討，了解這些地震紀錄之V/H特性，並以此探討現今規範規定之適當性。
臺灣位處太平洋環地震帶，板塊錯動之能量釋放會導致地震發生頻繁，其中包含可能造成重大災害之脈衝型近斷層地震。目前文獻缺少對於脈衝型近斷層地震垂直向地震動特性探討之研究，故本研究中除了對於臺灣之地殼地震記錄分析之外，也分別對於全球及臺灣脈衝型近斷層地震紀錄進行分析，以了解脈衝型及非脈衝型地震資料V/H之異同以及臺灣與其他地區是否存在區域差異。
本研究使用目前較重要或較新的七個V/H強地動模型及兩個相對簡化的V/H簡易模型做殘差分析，以觀察其殘差值的方式了解各強地動衰減式模型及參數模型在上述不同地震資料庫上之相符程度，並且使用高維度可視化技術中的Sammon映射方法，將研究中的高維度資料映射至二維Sammon映射圖中，以此方法觀察各模型的適用性，並且識別出在臺灣進行抗震設計時適用性較高之V/H強地動衰減式模型及V/H簡易模型。

關鍵字

垂直向與水平向反應譜譜值比 ； 地殼地震 ； 脈衝 ； 近斷層地震 ； 強地動衰減式模型 ； Sammon映射

並列摘要

Seismic design of structures often focuses on the demand from horizontal ground motions; however, the impact of vertical ground motions can be significant for seismic responses of ordinary buildings, highway bridges, and isolation systems. A practical procedure to determine vertical design spectrum is to scale a PSHA-based horizontal design spectrum using a vertical-to-horizontal ratio (V/H). Many seismic design codes (such as IBC and ASCE 7-10) specify a constant value of 2/3 for V/H at all periods. However, there are evidences that the V/H ratios might be greater than 2/3 in the short period range. This study explores the V/H ratios for shallow crustal ground motions in Taiwan and evaluates the adequacy of modern ground-motion models and the requirements of current Taiwan building code on V/H.
Pulse-like near-fault ground motions may cause significant damage to structures. This study analyzes the V/H ratio of pulse-like near-fault ground motions recorded worldwide and in Taiwan to understand the regional differences of the ratio.
Seven sets of ground-motion prediction models and two relatively simple models were used to predict the V/H ratios for ground motions in different databases of this study. The residuals between the predicted and recorded V/H values were computed and analyzed using both statistic approach and Sammon’s Map, which is a high-dimensional visualization technique to map the high-dimensional space data into a two-dimensional space. The results were used to evaluate the pros and cons of the application of the models on Taiwan data.

並列關鍵字

vertical-to-horizontal spectral-acceleration ratio ； shallow crustal earthquake ； pulse-like ； near-fault ground motion ； ground-motion prediction equation ； Sammon’s Map

參考文獻

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