【摘要】：預(yù)應(yīng)力混凝土箱梁橋由于跨越能力強(qiáng)、剛度大、抗扭性能好、便于施工等優(yōu)點(diǎn)而在橋梁工程界被廣泛使用。但在使用過程中,也逐漸暴露出許多耐久性問題,如箱梁橋腹板開裂嚴(yán)重,主體結(jié)構(gòu)長(zhǎng)期持續(xù)下?lián)稀＿M(jìn)一步,腹板混凝土開裂后,為了能夠更加全面地反映橋梁的使用性能,腹板的疲勞壽命的評(píng)估值得引起重視。這些問題不僅關(guān)系到橋梁的正常使用,嚴(yán)重時(shí)可能對(duì)運(yùn)營(yíng)過程中的安全性構(gòu)成威脅。因此,進(jìn)行預(yù)應(yīng)力混凝土箱梁橋腹板疲勞開裂及疲勞壽命評(píng)估的研究十分迫切。另外,已建的用于小跨徑的鋼筋混凝土橋梁的疲勞問題也日益受到關(guān)注,如何快速準(zhǔn)確地評(píng)價(jià)其疲勞壽命成為近些年橋梁界研究的熱門課題。論文對(duì)預(yù)應(yīng)力混凝土箱梁橋腹板及多跨鋼筋混凝土梁橋的疲勞問題開展了系統(tǒng)地研究,分別提出了預(yù)應(yīng)力混凝土箱梁橋腹板及多跨鋼筋混凝土橋梁疲勞壽命評(píng)估方法,以便應(yīng)用于工程實(shí)際。具體研究?jī)?nèi)容與成果如下:(1)通過總結(jié)預(yù)應(yīng)力混凝土箱梁橋發(fā)展、箱梁橋結(jié)構(gòu)分析理論、腹板斜裂縫成因、腹板疲勞問題研究現(xiàn)狀,指出了現(xiàn)有研究中的不足。(2)查閱大量文獻(xiàn),通過介紹混凝土及鋼筋的S-N曲線、僅考慮豎向剪力作用的腹板疲勞特性及橫向效應(yīng)下箱梁腹板的疲勞特性說明預(yù)應(yīng)力混凝土箱梁橋的疲勞特性。給出了箱梁腹板疲勞壽命的具體含義。(3)結(jié)合箱梁的受力特點(diǎn),基于梁桿有限元模型、變角度桁架模型及平面框架模型,提出了一種箱梁橋結(jié)構(gòu)簡(jiǎn)化分析方法。為了準(zhǔn)確反映腹板混凝土開裂后箍筋應(yīng)力的情況,提出了考慮裂縫影響系數(shù)的箍筋應(yīng)力計(jì)算公式,同時(shí)提出了考慮軸重、裂縫深度、梁高的裂縫影響系數(shù)的參數(shù)分析方法。基于線性疲勞損傷累積理論及箱梁橋結(jié)構(gòu)簡(jiǎn)化分析方法,提出了預(yù)應(yīng)力混凝土箱梁橋腹板疲勞壽命評(píng)估方法。通過實(shí)例研究,探討了裂縫深度、箱梁橫向效應(yīng)、車輛與預(yù)應(yīng)力耦合作用等對(duì)疲勞壽命計(jì)算結(jié)果的影響。(4)簡(jiǎn)單地介紹線彈性斷裂力學(xué)的基本概念。由于現(xiàn)有疲勞壽命評(píng)估方法不能充分考慮裂紋萌生階段及裂紋擴(kuò)展階段的壽命,提出了損傷—斷裂理論的鋼筋混凝土橋梁疲勞壽命評(píng)估方法。通過對(duì)某舊橋疲勞壽命評(píng)估的研究,分析對(duì)比了損傷力學(xué),斷裂力學(xué)及損傷—斷裂理論三種方法計(jì)算結(jié)果的差異,說明了損傷—斷裂理論方法的合理性。
[Abstract]:Prestressed concrete box girder bridges are widely used in the field of bridge engineering because of their advantages such as strong span capacity, high stiffness, good torsion resistance and easy construction. However, in the process of use, many durability problems are gradually exposed, such as the box girder bridge webs cracking seriously, the main structure persistent deflection for a long time. Furthermore, the fatigue life evaluation of web concrete is worthy of attention in order to reflect the performance of the bridge more comprehensively after cracking. These problems are not only related to the normal use of bridges, but also may pose a threat to the safety during operation. Therefore, it is urgent to study the fatigue cracking and fatigue life evaluation of prestressed concrete box girder bridge web. In addition, the fatigue problem of small span reinforced concrete bridges has been paid more and more attention. How to evaluate their fatigue life quickly and accurately has become a hot topic in the field of bridge research in recent years. In this paper, the fatigue problems of prestressed concrete box girder bridge web and multi-span reinforced concrete girder bridge are studied systematically, and the fatigue life evaluation method of prestressed concrete box girder bridge web plate and multi-span reinforced concrete bridge is put forward respectively. In order to be applied to engineering practice. The specific research contents and results are as follows: (1) through summing up the development of prestressed concrete box girder bridge, the theory of box girder bridge structure analysis, the causes of web slanting cracks, the current research status of web fatigue, It points out the shortcomings of the existing research. (2) referring to a large number of documents, the S-N curves of concrete and steel bar are introduced. The fatigue behavior of prestressed concrete box girder bridge is explained by the fatigue characteristics of web only considering vertical shear force and the fatigue characteristic of box girder web under transverse effect. The concrete meaning of the fatigue life of box girder web is given. (3) based on the finite element model of beam bar, variable angle truss model and plane frame model, a simplified analysis method of box girder bridge structure is proposed. In order to accurately reflect the stress of stirrups after cracking of web concrete, a formula for calculating the stress of stirrups considering the influence coefficient of cracks is put forward. At the same time, a parameter analysis method for the coefficient of influence of cracks considering axle load, crack depth and beam height is put forward. Based on the theory of linear fatigue damage accumulation and the simplified analysis method of box girder bridge structure, a method for evaluating the fatigue life of prestressed concrete box girder bridge web plate is proposed. The effects of crack depth, transverse effect of box girder and coupling effect of vehicle and prestress on fatigue life calculation results are discussed by examples. (4) the basic concept of linear elastic fracture mechanics is briefly introduced. Because the existing fatigue life assessment methods can not fully consider the life of crack initiation and crack propagation, a new method of fatigue life assessment for reinforced concrete bridges based on the theory of damage and fracture is proposed. Based on the study of fatigue life assessment of an old bridge, the difference of the calculation results of damage mechanics, fracture mechanics and damage fracture theory is analyzed and compared, and the rationality of the damage fracture theory method is proved.
【學(xué)位授予單位】：天津大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2014
【分類號(hào)】：U441.4

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