砂箱實驗模擬基樁裸露動力行為分析與探討

Study on Dynamic Behavior of Scoured Pile through Sandbox Test

蔡雨呈(Yu-Cheng Tsai)

指導教授 ： 宋裕祺

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

摘要

臺灣橋梁在颱風豪雨的侵襲下，橋梁基礎裸露的情況時有所聞，再加上台灣位於環太平洋地震帶，地震發生機率頻繁，橋梁隨時都有可能遭受到地震的威脅，而橋梁無論是受洪水或是地震作用其產生的災害，都對橋梁的安全有極大的傷害，本研究為了解基樁在受洪水沖刷後，基樁裸露，若再遭遇地震荷載的雙重作用下，對橋梁安全的疑慮，在目前大多以數值分析軟體模擬橋梁耐洪及耐震能力，但基樁與土壤間互制關係，工程實務上難以模擬，尤其土壤之特性複雜且多變化，是個令工程師頭疼的問題。
本文利用有限元素軟體Midas GTS 建立三維分析模型模擬土壤與基樁間的互制行為，並配合國家地震工程研究中心大型振動台以及翁作新教授等人研發雙軸向多層剪力試驗盒，進行縮尺之橋梁單樁試體振動台試驗，模擬橋梁受沖刷，導致基樁裸露時耐震之行為，並進行實驗與數值分析兩者比對驗證，再以最佳化的方法迴歸出合宜的土壤等值彈簧，希望能透過土壤彈簧的建立可適用於一般結構分析軟體例如SAP2000或MIDAS CIVIL等，以簡化橋梁結構同時受到沖刷及地震多重災害作用下的分析程序，對於提升分析效率應有所助益。

關鍵字

模型樁 ； 砂箱 ； 樁土互制 ； 土壤彈簧

並列摘要

Taiwan located in the southeast Pacific region where earthquake and typhoon occurred frequently. In past decades, the safety and serviceability of the bridges were threatened by either foundation scouring owing to the strict flood or severe seismic disaster. Souring as well known that is the soil erosion near the bridge foundation due to the severe flood. It could lead to the foundation exposure and bridge damage. Furthermore, the bridge dynamic response will be varied owing to the loss of soil lateral support. This could impose additional impact to the bridge and accelerate the occurrence of damage. Hence, the scoured bridge under the seismic excitations must be properly considered and investigated in where the probabilities of having these two hazards are relatively high. However, the structure response under multi-hazard combination and soil structure interaction are quite complicate problems as well as make engineer confused. Therefore, this thesis intends to establish a analytical model which includes the pier, foundation and soil layers by using FEM software firstly.
To confirm accuracy, time history analysis result of the FEM model would be compared with the dynamic response measurement of the biaxial laminar shear box shaking table test performed at NCREE. Subsequently, the dynamic analysis results which carried out from the FEM analytical model considering the varying scour depth would be treated as the database. A mathematical process of data fitting well known as the nonlinear regression was used to determine the optimal soil parameters. Finally, the equivalent soil spring to simplify the analysis procedures can be conducted. The proposed soil spring can readily applied by engineers to investigate the dynamic response of the bridge which subjected to multi-hazard events.

並列關鍵字

model pile ； sandbox ； pile-soil interaction ； soil spring

參考文獻

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