不規則橋梁之側推分析與耐震評估

Pushover Analysis and Seismic Assessment for Irregular Bridges

廖晧荏(Hao-Jen Liao)

指導教授 ： 黃仲偉

中原大學/工學院/土木工程研究所/碩士(2011年)

https://doi.org/10.6840/CYCU.2011.00088

摘要

非線性靜力側推分析因觀念簡單，且實務上常用之結構分析套裝軟體也提供此功能，近年來已儼然成為橋梁耐震評估之必要工具。然而目前業界所採用之單模態側推分析流程中，無論是側向力之空間分佈或是目標位移之計算，均是基於結構反應由其基本模態所控制，且振動模態與側向力分佈在結構進入塑性後仍維持不變之基本假設。很明顯地，這兩種假設對於高階模態相對重要之不規則結構並不合適。文獻上為考量高階模態之貢獻的多種側推分析改良方法，多為針對建築結構所設計。然而橋梁結構系統與建物結構系統的本質並不相同，這些改良式側推分析方法在橋梁結構之適用性仍待進一步評估。
本文首先探討傳統單模態側推分析對於不規則橋梁之適用範圍，並針對各式不規則橋梁探討不同側向力分佈型式對耐震評估之影響以及合理位移監測點位的選擇。其次，根據文獻上的模態側推分析，本文提出了簡易式的模態側推分析用以探討高階模態對不規則橋梁耐震評估之影響。最後，為釐清結構進入塑性動力特性改變對側推分析之影響，本研究自行開發相對應的塑性分析與耐震評估程式，針對各式不規則橋梁改採適應性側推分析。目標皆在使橋梁側推分析得以在充分之理論基礎與統一流程之條件下推廣至實際應用。

關鍵字

高階模態 ； 側推分析 ； 適應性側推分析 ； 耐震評估 ； 不規則橋梁

並列摘要

Pushover analysis provides a simple process to study the nonlinear behavior of structures and has rapidly become popular for seismic assessment of bridges in recent years. However, pushover analyses which are originally developed for building structures have two inherent drawbacks in that it is restricted with a single mode response and the lateral force distribution during the pushover process is invariant. As such, the pushover analysis can be reliably applied only on the regular structures and it can not account for the force redistribution after structure yields. Several researchers in the past few years have proposed some improved methods to overcome this problem. Unfortunately, most of these refined methods were aimed at solving problems related to buildings, not to bridges. Due to the intrinsic difference of seismic responses between buildings and bridges, further clarification of the circumstances under which these improved methods can produce reliable estimates for bridges in the practice is needed.
This research firstly attempts to specify quantitatively the scope of applicability for current pushover analyses on continuous irregular bridges. The effects of different load patterns of lateral forces and monitoring points on the seismic assessment are discussed. Secondly, a simplified modal pushover method is proposed to study the contributions of high modes of irregular bridges on the seismic assessment. Thirdly, a single-run procedure with fully adaptive and multi-modal considerations is developed. The numerical results from current pushover analyses are compared with those from adaptive pushover analyses. Finally, this research develops an in-house program, including modal and nonlinear analyses, to modify the drawbacks of current pushover analysis.

並列關鍵字

pushover analysis ； seismic assessment ； irregular bridges ； adaptive pushover analysis ； software development ； high modes

參考文獻

陳彥豪，基礎裸露橋梁耐震能力評估，台灣大學土木工程研究所碩士論文，2004。

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ATC-40. Seismic Evaluation and Retrofit of Concrete Buildings, Volume 1, Applied Technology Council, Redwood City, California. (1996).