地震來襲時，若橋梁產生嚴重破壞或坍塌，將導致巨大的生命與經濟損失，因此，如何評估橋梁之倒塌抵抗容量乃為一重要之課題(Collapse-Resistant Capacity)。傳統的有限元素分析方法評估橋梁之倒塌抵抗容量(Collapse Capacity)，往往需要耗費可觀的時間和資源，本研究建議採用增量動力分析法(Incremental Dynamic Analysis)，研發一合理且有效之評估方式，能快速推估橋梁之倒塌抵抗容量。本文採用一兩跨連續之鋼構橋梁為範例，進行倒塌抵抗容量評估，橋梁模型使用OpenSees有限元素分析軟體建立，使用劣化模型模擬橋梁結構在反覆載重作用下之勁度與強度劣化、以及非線性反應，並將增量動力分析法所得之橋梁倒塌影響參數，如：頻率、降伏性質、軟化反應、以及韌性，進行多元迴歸分析，使用所得之多元迴歸式，設計者或分析者僅需知道橋梁之側推行為資訊，即可迅速獲得橋梁於地震下之倒塌抵抗容量。為確定本文建立的多元迴歸式所獲得之倒塌抵抗容量具準確性，本文使用三個範例模型分別進行側推分析以及增量動力分析，並比較多元迴歸式與增量動力分析後評估之倒塌抵抗容量差異。;A simplified methodology for predicting the median of collapse capacity of steel bridges subjected to seismic excitations is proposed. The method is based on nonlinear static (pushover) analysis. After examining a wide range of structural parameters of the generic structures, a comprehensive database of collapse fragilities and pushover curves are generated. Based on the obtained pushover curves, closed-form equations for estimation of median of building collapse fragility curves are developed using multivariate regression analysis. Comparing the estimates of the median collapse capacity calculated from the closed-form equations with the actual collapse capacities determined from nonlinear response-history analysis indicates that the simplified methodology is reliable. The effectiveness of this methodology for predicting the median collapse capacity of steel bridge is further demonstrated with four case studies of steel bridge designed based on various structural parameters and different height of piers.
