不規則橋梁機率式耐震與倒塌風險評估之研究

Probabilistic Assessment of Seismic Performance and Collapse Risk for Irregularly Bridge

劉光晏(Kuang-Yen, Liu) ； 呂依涵(Yi-Han Lu)

《結構工程》 36卷2期 (2021/06) Pp. 115-137

https://doi.org/10.6849/SE.202106_36(2).0005

摘要

本研究探討既有群樁基礎橋梁，因沖刷導致基礎裸露前、後之耐震性能及倒塌機率。首先，針對土壤結構互制行為進行實驗與分析比較。根據群樁基礎單柱結構之雙軸向大型振動台實驗結果，比較美國石油協會（API）、日本道路橋示方書（JRA）及本研究之等值線性土壤彈簧法。研究結果顯示，在綜合考量時間成本與結果準確度下，API土壤彈簧法是較佳之樁土互制模擬方式。爰此，將API土壤彈簧應用至一座四跨全橋模型，採用增量動力分析法（IDA）並參考FEMA P58流程，探討不同橋基裸露程度之破壞模式、構件轉角韌性容量與不同等級地震之耐震能力與破壞機率，最後再與公路橋梁耐震評估與補強設計規範草案（2018年版）之靜力側推分析法進行比較。案例分析顯示，FEMA P58要求等級Ⅲ地震作用下倒塌機率小於10％，對於橋梁結構過於嚴格。短柱位置之樁基礎發生裸露時，對整體耐震性能有明顯降低。採用側推分析進行勁度不規則橋梁之耐震能力評估時，其結構反應較動力分析有不保守的疑慮。

關鍵字

橋梁 ； 勁度不規則 ； 基樁裸露 ； 土壤彈簧 ； 機率式倒塌評估

並列摘要

This study investigates the seismic performance and collapse risk of a group pile foundation irregularly bridge after scouring, which use API soil spring method to build a group pile foundation, four-span bridge models, and use probabilistic assessment to discuss the seismic performance due to different scouring places. This methodology was presented by previous researcher. For numerical analysis, this study uses SAP2000 to do incremental dynamic analysis (IDA). Afterward, based on the result, also establish fragility curve considering IO, LS, and CP performance. This study also uses pushover analysis to evaluate the seismic performance of bridge after scouring. The result shows the first yielding point for group pile will appear at the top of the pile. Second, Seismic performance for the bridge will have the greatest influence when scouring was taken place at the pier which has the biggest stiffness difference compare to its nearby pier. Last, pushover analysis for irregularly bridge may underestimate its reaction compare to nonlinear time history analysis. All in all, this simplified probabilistic procedure can be used as a reference for future seismic performance evaluation for bridges.

並列關鍵字

Scouring Effect ； Soil Spring ； Group Pile Effect ； Probabilistic Assessment Method ； Collapse Risk Analysis ； Incremental Dynamic Analysis ； Static Pushover Analysis

參考文獻

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Tang, Liang,Ling, Xianzhang(2014).Response of a RC pile group in liquefiable soil: A shake-table investigation.Soil Dynamics and Earthquake Engineering.67,301-315.

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