【作者】 王存立；

【导师】 张建仁； 刘扬；

【作者基本信息】 长沙理工大学 ， 桥梁与隧道工程， 2005， 硕士

【摘要】 近年来,我国混凝土箱梁桥的建设取得了较大的发展,但大部分该类桥梁在服役一段时间后,出现了不同程度的开裂。较多裂缝的出现影响了桥梁的承载能力和耐久性。研究开裂混凝土箱梁的可靠性,利用可靠指标为这类桥梁的维修加固决策提供理论依据,具有重要的理论价值和现实意义。本论文对开裂混凝土箱梁桥材料强度和几何尺寸的概率模型、抗力计算模式及基于模糊失效准则的可靠度进行了研究,主要工作内容如下: 1、对国内两座混凝土箱梁桥开裂情况进行了现场调查,分析了混凝土箱梁桥主要裂缝的分布规律,研究了箱梁不同部位裂缝的形成原因。2、引入分形几何理论描述混凝土箱梁桥的裂缝,用箱梁裂缝的分维数表示箱梁的开裂程度,并以此为基础建立了开裂区混凝土强度的概率模型。讨论了钢筋锈蚀和裂缝对混凝土碳化速度影响的机理,在此基础上建立了裂缝处钢筋截面积的历时变化模型。3、用空间有限元软件Ansys 计算了一座实桥的极限承载力,并将计算结果与简化平面杆系理论的计算结果进行比较,得出了该座桥梁在汽车荷载作用下的抗力计算模式修正系数。4、基于模糊失效准则建立了混凝土箱梁桥的可靠度计算模型,并计算了一座实桥基于模糊失效准则的可靠度。更多还原

【Abstract】 The great progress has been made in construction of the concrete box-girder bridges in our country recent years. But most of them present many cracks after servicing a period. Cracks weaken carrying capacity and durability of bridges. Therefore it is important to study the reliability of the cracked concrete box-girder bridges and to make a decision of maintainance and strengthing of the bridges by reliability index. This thesis studies the probabilistic model of material strength and size, the calculation model of resistance and the reliability based fuzzy failure criterion about concrete box-girder bridges with cracks. The main work is as follows. 1 The crack situation of two concrete box-girder bridges in China is investigated. And the distribution law of main cracks in box-girder bridges is analyzed. Then the reasons of cracks which formed in different location are studied. 2. The theory of fractal geometry is recommended to describ cracks in the concrete box-girder bridge, and the fractal dimension of cracks in box-girder is used to denote the degree of box-girder crack. Based on above theory, the probabilistic model of strength for cracked concrete is developed. Time-varying model of reinforcement area at crack sites is built after the influence of reinforcement corrosion and crack change the rate of concrete carbonization is analyzed. 3. The ultimate carrying capacity of a bridge is estimated with spatial finite element software-Ansys. Then the computing results are compared with the results computed by simplified plane beam elements, and the modified coefficient of resistance model of the bridge under the action of motor is gained. 4. On the basis of fuzzy failure criterion, model of reliability of concrete box-girder bridge is set up, and the reliability of existing bridge is calculated.更多还原