- 學位論文
樁基礎橋梁耐洪與耐震防災管理機制之訂定與探討
Establishment of Management System on Disaster Prevention for Pile-bridge Subjected to Flood and Earthquake
摘要
台灣位於歐亞大陸板塊與菲律賓海板塊交界處，又屬海島型氣候，國內多數橋梁飽受地震及颱風威脅，本文考慮橋梁受洪水、地震多重災害進行研究。每當梅雨、颱風季節，豪雨夾帶大量洪水造成橋基沖刷，橋梁基礎裸露事件時有所聞，情況嚴重時造成橋梁直接崩塌，輕微時則使橋基受損。颱風侵襲過後耐震能力損失之分析與探討，係本研究之研究重點。 本研究主要針對樁基礎橋梁在洪水造成橋基裸露後，耐震能力之變化進行討論。本文首先將基礎裸露深度與水位高度視為定數，並逐步放大洪水側推力至橋梁破壞狀態，以獲得洪水力對橋梁位移之關係圖。之後，再重新修訂基礎裸露深度與水位高度值，重複洪水力之側推分析，最終可以建立裸露深度、水位高、位移量之三維曲面圖，作為災後橋梁在洪水侵襲下是否達到降伏狀態與破壞狀態等之判別依據。 此三維曲面圖之應用層面有：(1)藉由現地監測資料得到此三種參數，判別橋梁安全性，達到封橋機制之功能；(2)颱風過後則以橋梁受洪水狀態下最大位移判別樁基礎是否已達降伏，作為樁塑鉸修正之依據，並重新進行耐震能力評估，瞭解颱風造成橋梁耐震能力損失後，其耐震能力是否符合規範要求。本文所得結果可供為颱洪時封橋決策判斷之依據以及颱洪過後橋梁耐震能力快速評估之用。
並列摘要
This thesis intends to study the seismic capacity left of the existing bridges subjected to attack of flood. The pushover analyses considering the flood action on bridge pile were carried out to have relationships between lateral displacements at top of pile, high water level, flood speed and scouring depth of pile. The relationships obtained can be expressed as a management surface serving as estimation of disaster based on the predicted data from Central Weather Bureau before a specific typhoon visit. In addition, the lateral displacements at top of pile excited by flood can be explored by monitoring instruments on bridge in flood and served as the justification of if the pile body reaches structural inelastic behavior. In case of inelastic behavior, the plastic hing properties of pile body have to be modified because structural unloading caused by release of flood should change original characteristics defined for undamaged member. Therefore, the seismic capacity of the bridge suffered is little than the original one and can be obtained through the pushover analysis on the damaged structure with modified plastic hing. Through the process proposed, the deterioration of seismic capacity of bridge subjected to different levels of flood attack can be shown and is important to making policy on repairing or retrofitting of the bridges with insufficient seismic capacity for the administrations of bridge management.