氣候變遷下跨河橋梁可靠度分析-自強大橋為例

Abstract

本篇研究探討氣候變遷下河川洪峰流量改變對橋梁結構安全之影響，選定自強大橋作為案例。整個研究分為三個部分，第一部分為模擬氣候變遷下自強大橋流量的變化，採用GCM模式（General Circulation Model）用歷史氣象資料（包含1986-2005年雨量、氣溫）來繁衍未來各情境下的氣溫資料，再通過GWLF降雨逕流模式（Generalized Watershed Loading Function）將繁衍出的未來氣象資料進行集水區流量模擬。第二部分為模擬自強大橋處的流速及水位，藉由HEC-RAS輸入GWLF模擬的流量結果進行二維水理分析計算得到流速及水位來推算各橋墩的沖刷深度。第三部分建立SAP2000自強大橋模型，探討橋梁在不同沖刷深度及地震強度下之力學行為，藉由側推分析搭配非線性歷時分析得到位移韌性需求值，再根據規定之韌性容量值建立易損性曲線。

This study aims to assess the safety impact of a bridge considering the influence of climate change. To demonstrate the proposed methodology, Tzu-Chiang bridge is selected as the research object. This study consists of three parts. First, generating future meteorological data under climate change scenarios via GCM(General Circulation Model) with history meteorological data (include 1986-2005 years daily rainfall and temperature), and converting the generated future meteorological data into the watershed runoff using GWLF (Generalized Watershed Loading Function). Second, acquiring stream level and flow velocity at bridge site via 2D HEC-RAS model using the outcomes of GWLF, the goal of this part is to estimate the scouring depth of each pier. Third, establishing SAP2000 bridge model to assess the structural behaviors with different scour depths and earthquake intensity. the demands of displacement ductility are derived from pushover analysis and time history analysis. The capacity of displacement ductility is adopted form FEMA to establish the fragility curves.