構架式不規則橋梁之側推分析與耐震評估

Pushover Analysis and Seismic Assessment for Irregular Portal Frame Bridges

吳權祐(Chuan-Yu Wu)

指導教授 ： 黃仲偉

中原大學/工學院/土木工程研究所/碩士(2012年)

https://doi.org/10.6840/cycu201200131

摘要

文獻上對於橋梁之側推分析或耐震評估多集中在探討橋墩為單柱（single column）型式之橋梁，但在工程實務上橋墩的型式亦涵蓋構架（portal frame）型式。兩者之差異主要在於靜力側推分析中構架的左、右兩柱所受之軸力並不相同，而軸力會影響橋柱截面所對應之彎矩－曲率關係，進而影響侧推分析所得之容量曲線。此外，構架式橋墩在墩頂也會產生塑鉸，增加結構之複雜度。另一方面，目前工程界常用之側推分析流程中，無論是側向力之空間分佈或是目標位移之計算，均是假設結構反應由基本模態所控制。然而對於容易激發較高振態效應的不規則橋梁而言，單純假設基本很模態控制並不合理。且對於多跨連續之不規則橋梁，其側向位移之觀測點也不容易決定。而觀測點的選取會影響容量曲線轉換為耐震容量震譜曲線的代表性。因此若未能有效考慮較高振態以及合理觀測點位之影響，可能導致側推分析結果的嚴重誤差。本研究針對自行設計之六種數值橋梁，利用有限元素商業軟體SAP 2000進行垂直行車向之靜力非線性側推分析，以動力分析結果為比較基準，探討不同側向力分佈型式與橋梁觀測點對構架式橋墩之橋梁側推分析結果的影響；此外，也將比較簡易式模態側推分析（SMPA）與多模態側推分析（MPA）對側推分析中高階模態效應評估之差異，最後比較不同耐震評估方式對各種不規則構架式橋梁詳細耐震評估之影響。

關鍵字

不規則橋梁 ； 側推分析 ； 構架式橋墩 ； 耐震評估 ； 高階模態

並列摘要

In the literature, the pushover analysis and seismic assessment focused on bridges with single-column-bent piers. In practical, there are many bridges with portal frame piers in Taiwan. In latter cases, the axial forces of the right and left columns are different, which affect the relationship between the moment and curvature of the cross section of each column. The pushover curve is then influenced by the moment-curvature curves of cross sections. Furthermore, the plastic hinges could occur at the top or bottom of each column for bridges with portal frame piers, which increases the complexity of the structural analyses. Besides that, the pattern of lateral force and displacement monitoring point are based on the assumption that responses of the considered structure are mainly controlled by its first mode in traditional pushover analyses. As such, the pushover analysis may not be reliable for the irregular bridges which higher modes are important and the selection of the displacement monitoring point is not easy. In this study, six irregular numerical bridges are established using the commercial finite element software, SAP2000, to carry out the pushover analyses and seismic assessments. The influences of the pattern of lateral load and the selection of displacement monitoring point in the pushover analyses are investigated. In addition, modal pushover analyses (MPA) and simplified modal pushover analyses (SMPA) are carried out to study the effects of higher modes for irregular bridges. Finally, three different seismic assessment methods are discussed and these corresponding results are compared with nonlinear dynamic analyses.

並列關鍵字

seismic assessment ； portal frame piers ； irregular bridges ； pushover analysis ； higher modes

參考文獻

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