【摘要】：鋼橋平面外變形是鋼橋抗疲勞設(shè)計(jì)的一大難點(diǎn),鋼橋腹板間隙微小的平面外變形可以產(chǎn)生很大的彎曲應(yīng)力,導(dǎo)致腹板間隙疲勞裂紋的萌發(fā)和擴(kuò)展,萌生于主梁腹板上的疲勞裂紋嚴(yán)重威脅了橋梁的設(shè)計(jì)使用壽命。許多學(xué)者通過(guò)靜力分析或者在靜力分析的基礎(chǔ)上疊加一個(gè)動(dòng)力沖擊系數(shù)來(lái)考慮車輛荷載的動(dòng)力效應(yīng)對(duì)腹板間隙應(yīng)力的影響。然而,在橋面不平整度較差的情況下,規(guī)范中的疲勞動(dòng)力沖擊系數(shù)可能低估了車輛動(dòng)力沖擊效應(yīng),往往導(dǎo)致腹板間隙的實(shí)際疲勞壽命低于設(shè)計(jì)壽命。為了更準(zhǔn)確的研究橋面不平整度退化過(guò)程中車輛荷載動(dòng)力效應(yīng)對(duì)腹板間隙疲勞壽命的影響,本文的研究?jī)?nèi)容和主要結(jié)果如下:(1)根據(jù)AASHTO橋梁設(shè)計(jì)規(guī)范建立了 4座不同跨徑的I型簡(jiǎn)支鋼梁橋的有限元模型和疲勞車的三維模型;通過(guò)疲勞車移動(dòng)加載分析了腹板間隙的應(yīng)力分布規(guī)律,并研究了橋梁跨徑和腹板間隙長(zhǎng)度對(duì)腹板間隙應(yīng)力的影響程度。結(jié)果表明腹板間隙長(zhǎng)度對(duì)腹板間隙應(yīng)力的影響較小,橋梁跨徑是影響腹板間隙應(yīng)力的主要因素。(2)在假定的交通量和環(huán)境條件下,研究了橋面不平整度的退化過(guò)程,得到橋面不平整度從一個(gè)等級(jí)退化到另一個(gè)等級(jí)過(guò)程中所需的時(shí)間和通過(guò)車輛的數(shù)量,以及橋面不平整度處于不同等級(jí)所占的時(shí)間比例。(3)根據(jù)橋梁和車輛接觸點(diǎn)的作用力和位移關(guān)系建立三維車橋耦合振動(dòng)模型,采用模態(tài)疊加技術(shù)和四階倫格庫(kù)塔法求解,通過(guò)數(shù)值分析獲得不同橋面不平整度等級(jí)下腹板間隙的應(yīng)力和應(yīng)力幅水平,和不平整度退化過(guò)程中車輛荷載動(dòng)力效應(yīng)對(duì)I型簡(jiǎn)支鋼梁橋腹板間隙的應(yīng)力和應(yīng)力幅沖擊系數(shù)。結(jié)果表明:基于腹板間隙應(yīng)力幅計(jì)算的沖擊系數(shù)大于傳統(tǒng)基于應(yīng)力的沖擊系數(shù);AASHTO規(guī)范中采用的疲勞沖擊系數(shù)0.15在不平整度較差時(shí)低估了車輛荷載動(dòng)力效應(yīng)對(duì)腹板間隙疲勞壽命的影響,基于此本文提出用于腹板間隙疲勞壽命評(píng)估的應(yīng)力幅沖擊系數(shù)建議值。(4)本文采用基于MATLAB編寫(xiě)的雨流計(jì)數(shù)程序統(tǒng)計(jì)疲勞車通過(guò)時(shí)腹板間隙產(chǎn)生的應(yīng)力幅,基于S-N曲線并結(jié)合Palmgren-Miner線性累積損傷準(zhǔn)則對(duì)鋼橋腹板間隙進(jìn)行疲勞壽命評(píng)估。研究結(jié)果表明:定期進(jìn)行橋面維護(hù)可以有效減小腹板間隙的疲勞損傷并延長(zhǎng)腹板間隙的疲勞壽命。本文建議的腹板間隙應(yīng)力幅沖擊系數(shù)和路面養(yǎng)護(hù)時(shí)間對(duì)評(píng)估和延長(zhǎng)腹板間隙的疲勞壽命具有重要意義。
[Abstract]:The out-of-plane deformation of steel bridge is a difficult point in anti-fatigue design of steel bridge. The small out-of-plane deformation of web gap of steel bridge can produce great bending stress, which leads to the sprouting and propagation of fatigue crack in web gap. The fatigue cracks on the web of the main beam seriously threaten the design life of the bridge. Many scholars consider the influence of dynamic effect of vehicle load on web clearance stress by static analysis or superposition of a dynamic impact coefficient on the basis of static analysis. However, in the case of poor deck irregularity, the fatigue dynamic impact coefficient in the code may underestimate the vehicle dynamic impact effect, which often results in the actual fatigue life of the web gap being shorter than the design life. In order to study more accurately the influence of vehicle load dynamic effect on the fatigue life of web clearance in the process of deck irregularity degradation, The research contents and main results are as follows: (1) according to the design code of AASHTO bridge, the finite element models of four simple-supported steel beam bridges with different spans and the three-dimensional models of fatigue vehicles are established. The stress distribution law of web clearance is analyzed by moving load of fatigue vehicle, and the influence degree of bridge span and web gap length on web gap stress is studied. The results show that the web gap length has little effect on the web gap stress, and the bridge span is the main factor affecting the web gap stress. (2) under the assumed traffic volume and environmental conditions, the degradation process of the unevenness of the bridge deck is studied. To get the time and the number of vehicles needed to reduce the unevenness of the bridge deck from one grade to another, (3) the three-dimensional vehicle-bridge coupled vibration model is established according to the force and displacement relationship between the bridge and vehicle contact points, and the modal superposition technique and the fourth-order Ranger-Kutta method are used to solve the model, and the three-dimensional vehicle-bridge coupling vibration model is solved by the modal superposition technique and the fourth-order Ranger-Kutta method. By means of numerical analysis, the stress and stress amplitude levels of web clearance under different deck irregularity grades, and the stress and stress amplitude impact coefficient of vehicle load dynamic effect on web clearance of I type simply supported steel beam bridge during the process of irregularity degradation are obtained. The results show that the impact coefficient calculated based on the web gap stress amplitude is larger than the traditional stress-based impact coefficient. The fatigue impact coefficient 0.15 adopted in the AASHTO Code underestimates the influence of the dynamic effect of vehicle load on the fatigue life of web clearance when the irregularity is poor. Based on this, this paper puts forward the recommended value of stress amplitude impact coefficient for fatigue life assessment of web clearance. (4) in this paper, the rain flow counting program based on MATLAB is used to calculate the stress amplitude produced by webs clearance when fatigue car passes through. The fatigue life of steel bridge web gap is evaluated based on S-N curve and Palmgren-Miner linear cumulative damage criterion. The results show that the fatigue damage of web gap can be effectively reduced and the fatigue life of web space can be prolonged by regular maintenance of bridge deck. The stress amplitude impact coefficient and pavement maintenance time suggested in this paper are of great significance for evaluating and prolonging fatigue life of web clearance.
【學(xué)位授予單位】：湖南大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：U441

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