勁度不規則橋梁側推分析與耐震評估

Pushover Analysis and Seismic Assessment for Stiffness Irregular Bridges

黃仲偉(Chang-Wei Huang) ； 洪曉慧(Hsiao-Hui Hung) ； 廖皓荏(Hao-Ren Liao) ； 陳常麒(Chang-Chi Chen)

《中國土木水利工程學刊》 26卷4期 (2014/12) Pp. 343-357

https://doi.org/10.6652/JoCICHE.201412_26(4).0007

摘要

近年來非線性靜力側推分析已成為最普遍的結構系統耐震評估方法，相較於非線性動力歷時分析，非線性靜力側推分析的優點在於計算簡單，可迅速提供地震力作用下之最大位移與破壞機制。然而目前工程界常用之側推分析與耐震評估流程中是假設結構反應由基本模態所控制，利用基本模態空間分佈的側向力進行側推分析得到結構之容量曲線；再將耐震容量曲線轉換為等價單自由度系統的耐震容量震譜；由容量譜曲線與非線性設計反應譜的交點來決定橋梁的性能點。然而上述假設對於高階模態相對重要之不規則結構並不適當，可能無法正確反映不規則橋梁的動力特性。本文以勁度不規則之多跨連續橋為例，提出適當的側向力空間分佈與目標位移控制點位的選取，以此改良的靜力側推分析方法來考慮高階模態的效應。最後利用增量動力分析的方式，探討涵蓋彈性範圍至塑性破壞等不同大小的地震強度下，傳統單模態側推、改良式靜力側推與動力非線性分析之差異，用以評估不同方法的適用性。數值模擬結果顯示以均勻分佈之側向力分佈搭配多點觀測容量譜轉換方式最佳，可克服傳統單模態側推無法準確評估不規則橋梁整體變形趨勢的限制，本研究的結果可供國內各單位應用於勁度不規則橋梁耐震評估。

關鍵字

靜力側推 ； 側向力分佈 ； 位移控制點 ； 勁度不規則橋梁 ； 耐震評估

並列摘要

Static pushover analyses have become the most common approach in seismic assessments. Compared with nonlinear dynamic time history analyses, static pushover analyses have advantages on low computation cost and providing the capacities of lateral displacements and failure mechanisms of structures efficiently. The usual procedures of the pushover analysis are based on the assumption that structural behaviors are dominated by the first mode. The load pattern of lateral forces is determined from the first mode of the structure to get the pushover curve in the pushover analyses. The pushover curve is then transferred to the corresponding capacity spectrum curve on the basis of single-degree-of-freedom assumption. The performance point of the structure is the intersection of the capacity spectrum curve and nonlinear design spectrum curves. However, such procedures are not suitable for irregular structures in which the contributions of higher modes are relatively important. This paper aims to study the limitations of the standard static pushover analysis for stiffness irregular bridges. The effects of the lateral load pattern and monitoring point for target displacement in static pushover analyses are investigated. Finally, the incremental dynamic analyses are included to study the performances of the conventional static pushover analysis and modified static pushover analysis under different earthquake intensities. Numerical results demonstrate that the results of conventional static pushover analyses could be improved by the uniform load pattern and multiple monitoring points. These results could help engineers in dealing with the seismic assessments for stiffness irregular bridges.

並列關鍵字

pushover analysis ； load pattern ； monitoring point ； stiffness irregular bridge ； seismic assessment