本文選題：裂紋擴(kuò)展 + 數(shù)值模擬��； 參考：《東南大學(xué)》2015年碩士論文

【摘要】：疲勞破壞是鋼橋構(gòu)件和其連接細(xì)節(jié)的典型破壞模式之一,疲勞裂紋(縫)的萌生和擴(kuò)展不僅影響到結(jié)構(gòu)的安全,也引發(fā)了大量的后期養(yǎng)護(hù)費(fèi)用。因此,科學(xué)準(zhǔn)確地預(yù)測(cè)裂紋的擴(kuò)展對(duì)于疲勞敏感部位的維修和加固具有重要意義。本文針對(duì)大跨斜拉橋的若干疲勞易損細(xì)節(jié),研究了隨機(jī)荷載作用下疲勞裂紋擴(kuò)展的數(shù)值模擬方法,所完成的主要工作如下：(1)疲勞裂紋及其擴(kuò)展的斷裂力學(xué)理論及方法研究。介紹了裂紋擴(kuò)展的三種模式及其成因,對(duì)裂尖漸進(jìn)場(chǎng)的描述方法、斷裂參數(shù)的常用計(jì)算方法、裂紋擴(kuò)展模型、裂紋擴(kuò)展的數(shù)值模擬方法及其適用性進(jìn)行了對(duì)比分析。(2)提出了隨機(jī)車載場(chǎng)和環(huán)境溫度作用下的大跨鋼橋疲勞裂紋擴(kuò)展的數(shù)值模擬方法。通過橋梁收費(fèi)系統(tǒng)和健康監(jiān)控系統(tǒng)的實(shí)測(cè)數(shù)據(jù),建立了一種面向疲勞分析的精細(xì)化車輛荷載概率模型以及環(huán)境溫度模型�；诙喑叨冉：妥幽Ｐ图夹g(shù),采用最小應(yīng)變能密度因子方法判定復(fù)合裂紋的擴(kuò)展方向,應(yīng)用局部網(wǎng)格重劃分實(shí)現(xiàn)了疲勞裂紋擴(kuò)展的數(shù)值模擬。(3)通過實(shí)橋檢測(cè),對(duì)斜拉橋鋼箱梁縱隔板開裂情況進(jìn)行了統(tǒng)計(jì)分析,研究了裂紋的形態(tài)、分布特點(diǎn)及擴(kuò)展規(guī)律。通過有限元分析,研究了縱隔板的作用及其損傷后對(duì)橋梁性能的影響,探討了縱隔板節(jié)點(diǎn)區(qū)域開裂的原因,并發(fā)現(xiàn)較大的應(yīng)力幅和交變荷載是裂紋萌生及擴(kuò)展的主要原因。在此基礎(chǔ)上,通過概率有限元分析,對(duì)潤(rùn)揚(yáng)斜拉橋跨中縱隔板節(jié)點(diǎn)區(qū)域的疲勞壽命進(jìn)行了預(yù)測(cè),其結(jié)果與實(shí)橋檢測(cè)結(jié)果基本吻合。(4)基于本文提出的裂紋擴(kuò)展的模擬方法,對(duì)潤(rùn)揚(yáng)斜拉橋鋼箱梁正交異性橋面板的不同部位進(jìn)行了裂紋擴(kuò)展分析：研究了裂紋擴(kuò)展中各裂紋模式的貢獻(xiàn),得到了應(yīng)力強(qiáng)度因子的時(shí)程曲線�；诰�彈性斷裂力學(xué),對(duì)各細(xì)節(jié)的裂紋擴(kuò)展壽命進(jìn)行了預(yù)測(cè)。上述工作為研究大跨鋼橋在運(yùn)營(yíng)階段的疲勞損傷機(jī)理以及推演裂紋的萌生、擴(kuò)展過程等問題提供了有效的手段,可為大跨鋼橋的優(yōu)化設(shè)計(jì)、維護(hù)方案和加固策略提供參考。
[Abstract]:Fatigue failure is one of the typical failure modes of steel bridge members and their connection details. The initiation and propagation of fatigue cracks (joints) not only affect the safety of structures, but also lead to a large amount of later maintenance costs.Therefore, scientific and accurate prediction of crack propagation is of great significance for the maintenance and reinforcement of fatigue sensitive sites.In this paper, the numerical simulation method of fatigue crack propagation under random load is studied for some fatigue vulnerability details of long-span cable-stayed bridge. The main work accomplished is as follows: 1) the theory and method of fracture mechanics of fatigue crack and its propagation.This paper introduces three modes of crack growth and their causes, the description of progressive field of crack tip, the commonly used calculation methods of fracture parameters, and the crack propagation model.The numerical simulation method of crack growth and its applicability are compared and analyzed. (2) A numerical simulation method for fatigue crack propagation of long span steel bridges under the action of random vehicle field and ambient temperature is proposed.Based on the measured data of bridge toll collection system and health monitoring system, a refined vehicle load probability model and environmental temperature model for fatigue analysis are established.Based on the technique of multi-scale modeling and sub-model, the minimum strain energy density factor method is used to determine the propagation direction of composite crack, and the numerical simulation of fatigue crack propagation is realized by using local mesh re-division.The cracking of the steel box girder of cable-stayed bridge is analyzed statistically, and the shape, distribution and propagation of the crack are studied.Through finite element analysis, the effects of mediastinal plate and its damage on bridge performance are studied, and the causes of cracking in the joint region of mediastinal plate are discussed. It is found that large stress amplitude and alternating load are the main causes of crack initiation and propagation.On this basis, through the probabilistic finite element analysis, the fatigue life of the middle mediastinal plate joint area of the Runyang cable-stayed bridge is predicted. The results are in good agreement with the real bridge detection results. (4) based on the simulation method proposed in this paper, the crack propagation is simulated.Crack propagation analysis of different parts of orthotropic deck plate of steel box girder of Runyang cable-stayed bridge is carried out. The contribution of crack modes in crack propagation is studied and the time-history curve of stress intensity factor is obtained.Based on the linear elastic fracture mechanics, the crack propagation life of each detail is predicted.The above work provides an effective means for studying the fatigue damage mechanism, crack initiation and propagation process of long span steel bridge in operation stage, and can be used as a reference for the optimization design, maintenance scheme and reinforcement strategy of long span steel bridge.
【學(xué)位授予單位】：東南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2015
【分類號(hào)】：U441.4

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