橋梁基礎搖擺機制之初步研究

Preliminary Study of Rocking Bridge Foundation

何姿慧(Tzu-Hui Ho)

指導教授 ： 張國鎮

國立臺灣大學/工學院/土木工程學研究所/碩士(2009年)

https://doi.org/10.6342/NTU.2009.00072

摘要

本研究藉由實驗與分析探討橋柱直接基礎搖擺（Rocking）機制對橋柱耐震性能之影響。921地震後，政府交通部門積極辦理橋梁耐震能力評估與補強工程，也提高部份地區之設計地震力，而於部分補強或新建案例中可發現，直接基礎之尺寸寬幅明顯過大，似乎有過於保守之疑慮。歸咎其原因，主要受到設計地震力提高，而與穩定性檢核相關之基礎受壓面積仍需滿足原有規定，所以基礎尺寸需予以擴大。事實上，直接基礎搖擺機制之隔震效益已受到證實，為能採用較經濟之斷面，可採用適當設計之直接基礎，透過搖擺機制產生之周期延長降低地震力，並利用土壤於大地震中塑性變形能力吸收地震能量。本研究包括兩大重點。第一為進行直接基礎橋柱之單向反覆載重試驗與擬動態試驗，第二為建立可考量直接基礎搖擺機制之橋柱基礎-土壤互制數值分析模型，藉由數值模擬結果與實驗結果之比對，修正數值模型，並以修正後之數值模型進行初步參數分析。

關鍵字

直接基礎 ； 搖擺基礎 ； 擬動態試驗 ； 反覆載重試驗 ； 隔震

並列摘要

Some recent studies have shown that rocking of spread foundation has beneficial effect on the dynamic performance of columns by decreasing the plastic deformation occurring at the plastic zone. This implies that the ductility demand of columns can possibly be reduced. However, rocking is still not an acceptable mode of response in design code generally. In order to gain better understanding of the problem of rocking, and in turn have more confidence in taking its benefit into consideration during design and retrofit process, a series of rocking experiments were performed and an analytical model was established. These rocking experiments include two pseudo-dynamic tests followed by a cycling test. From these tests, the rocking behaviors of a column undergoing different levels of earthquake were obtained. In addition, an analytical model which can take the nonlinear interaction between foundation and underlying soil into account was also established using Sap2000N. This analytical model was validated through the comparison with the experimental data. Using this analytical model, a parametric study was performed and the influence of foundation size and soil spring stiffness on rocking behavior was discussed.

並列關鍵字

spread foundation ； rocking foundation ； pseudo-dynamic test ； cyclic test ； seismic isolation

參考文獻

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