橋梁直接基礎搖擺之極限分析

Dynamic Analysis of Bridges with Rocking Isolation in Ultimate States

黃敏彥(Min-Yen Hunag)

指導教授 ： 李姿瑩

國立中央大學/工學院/土木工程學系/碩士(2013年)

摘要

近年地震對台灣造成許多的災害，使耐震設計規範之設計地震力提高，導致部分補強和新建案例之直接基礎尺寸明顯過大。其主要原因乃設計地震力提高，穩定性檢核時基礎受壓面積仍須滿足原有規定，所以基礎尺寸必須擴大。依據過去地震經驗發現直接基礎之搖擺機制可降低傳遞至上部結構之地震力，並且透過搖擺機制產生振動周期延長降低地震力，也可藉由土壤於大地震下之塑性行為吸收地震能量。本研究旨在開發土壤元素模型(Soil Element)建立土壤與基礎互制之構件，模擬橋梁於強震中土壤與基礎之高度非線性行為。
本研究採用向量式有限元素(Vector Form Intrinsic Finite Element)為結構動力分析方法，此方法適用於處理大變形、大變位、材料非線性與剛體運動等問題。為了模擬土壤與基礎互制關係，本研究引入溫克勒模型(Winkler-based models)，溫克勒模型可用以模擬垂直向土壤(q-z spring)、側向被動土壤(p-x spring)與土壤結構間摩擦力(t-x spring)，經由算例分析驗證此土壤彈簧之正確性，並且藉由單跨梁橋證實直接基礎搖擺機制之隔震作用，最後以五跨連續梁橋作為模型，探討其參數變化對橋梁之影響，並模擬至極限狀態，瞭解橋梁在在極限狀態下之橋梁反應。

關鍵字

向量式有限元素 ； 極限狀態 ； 橋梁 ； 動力分析 ； 直接基礎 ； 搖擺機制

並列摘要

In recent years, the earthquake caused many disasters in Taiwan, so seismic design specification to improve the design seismic forces. Therefore the spread foundation wide obviously is too large in some reinforcement and new cases. The main reason is improving the design seismic forces. And the foundation of pressured area have to satisfy the specification, therefore the size of foundation must be expanded. Based on the past experience, the rocking mechanism of spread foundation can reduce the seismic force of the main structure, besides it can extend the period of structure and decrease the seismic force. In addition, the soil will generate the plastic behavior and absorb the seismic energy under the extreme earthquake. This study aims to develop new soil element model and build the soil and foundation of components.
The Vector Form Intrinsic Finite Element (VFIFE), a new computational method is adopted in this study because the VFIFE has the superior in managing the engineering problems with material nonlinearity, discontinuity, large deformation and arbitrary rigid body motions of deformable bodies. In order to simulate the interaction between soil and foundation, the study use Winkler model (Winkler-based models). Winkler model can simulate the vertical soil (q-z spring), lateral passive soil (p-x spring) and the friction force between soil and foundation (t-x spring). Through numerical simulation of examples to verify the soil element model are feasible and accurate. Besides, using the single-span bridge to confirm the rocking mechanism of spread foundation has the isolation effect. Finally, five-span continuous bridge as a model to investigate the effect of the parameter changes, and to understand the bridge behavior in ultimate condition.

並列關鍵字

VFIFE ； ultimate state ； bridge ； dynamic analysis ； spread foundation ； rocking mechanism

參考文獻

[40] 賴姿妤 (2011)，「樁基礎沖刷橋梁模型之振動台試驗研究」，碩士論文，國立台灣大學土木工程研究所，張國鎮。

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