鋼筋混凝土非線性結構動力分析之數值雜訊探討

Numerical Noise in Reinforced Concrete Nonliner Structural Dynamic Analysis

李政達(Jheng-Da Li)

指導教授 ： 楊元森

國立臺北科技大學/工程學院/土木與防災研究所/碩士(2011年)

https://doi.org/10.6841/NTUT.2011.00382

摘要

有限元素結構分析之梁柱元素纖維斷面分析法(fiber section analysis)同時具有考量結構局部材料非線性與運算量需求低的特性，使的該方法近年來被廣為應用在結構之非線性動力數值模擬。然而，以此方法進行鋼筋混凝土結構分析時，梁柱元素內力反應經常會出現高頻而不正常的雜訊。這些雜訊並不符合結構物應有的物理行為，而是數值分析本身所造成的雜訊。這些雜訊的存在一方面可能表示數值模擬不夠準確，另一方面亦可能造成工程師對於結構元件內力的誤判，甚至導致後續不當的結構設計，而影響結構體的耐震性與安全性。
本研究對上述數值雜訊的發生原因進行仔細的探討與測詴，並提供避免雜訊的方法與建議。經由一系列的測詴顯示，雜訊產生最主要的原因是混凝土材料纖維區塊之數值模型在承受極限載重後發生瞬間破壞，產生不當的梁柱內力高頻訊號而導致分析結果的誤差。本研究使用美國太平洋地震工程研究中心研發的OpenSees 軟體，分別建構單柱鋼筋混凝土構架和兩層兩跨鋼筋混凝土構架，並採用 OpenSees 所提供的材料設定(material)、非線性梁柱元素搭配纖維斷面(fiber section)及分析方法(analysis options)，來進行非線性動力歷時分析。本研究的非線性動力歷時分析考慮混凝土與鋼的非線性組成率，以及結構大位移非線性效應。
本研究設定不同的材料參數、地震力及收斂門檻，來模擬混凝土結構物在非線性動力分析時所産生的雜訊，並探討主要發生的原因及對分析結果的影響。最後，本研究會提出在 OpenSees 環境下最佳的參數設定參考值。

關鍵字

數值雜訊 ； OpenSees

並列摘要

Finite element structural analysis of fiber section analysis method considering structural local nonlinear material and low operation has been widely applied to structural of nonlinear dynamic simulation in recent years. However, the beam column element internal reaction forces will cause abnormal high-frequency noises when using the method to do reinforced concrete structural analysis. These noises do not conform to physical behavior of the structural but numerical analyses. These noises may indicate numerical simulations is not accurate. It also may mislead engineers to make a wrong judgment for structural element internal forces, and even lead to improper structural design that affect the structural safety.
This research investigated and tested carefully in the reason motioned above then proposed methods and recommendations to avoid noises. After a series of testing, this research found that the reason causes noises is because concrete fiber sections break immediately when bearing extreme loads and induce improper beam force’s high-frequency signal to make analysis mistake. This research used OpenSees, which is made by Pacific Earthquake Engineering Research (PEER) Center to create a single-column reinforced concrete structure and two-story-two-span structure. This research used material, fiber section, and analysis options offered by OpenSees to analyze nonlinear dynamic analysis. This research’s nonlinear dynamic analysis considered concrete and steel’s constitutive laws of nonlinear composition and structure displacement non-linear effect. This research set different materials, earthquakes, and convergence rates to simulate RC structures’s noises when analyzing nonlinear dynamic analysis. This research investigated the major reason and the influence to analysis result. Finally, this research proposed the satisfactory parameter setting reference by using OpenSees.

並列關鍵字

OpenSees ； Numerical Noise

參考文獻

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