预应力及钢筋混凝土桥梁疲劳寿命分析方法研究

发布时间：2019-01-04 15:12

【摘要】：预应力混凝土箱梁桥由于跨越能力强、刚度大、抗扭性能好、便于施工等优点而在桥梁工程界被广泛使用。但在使用过程中,也逐渐暴露出许多耐久性问题,如箱梁桥腹板开裂严重,主体结构长期持续下挠。进一步,腹板混凝土开裂后,为了能够更加全面地反映桥梁的使用性能,腹板的疲劳寿命的评估值得引起重视。这些问题不仅关系到桥梁的正常使用,严重时可能对运营过程中的安全性构成威胁。因此,进行预应力混凝土箱梁桥腹板疲劳开裂及疲劳寿命评估的研究十分迫切。另外,已建的用于小跨径的钢筋混凝土桥梁的疲劳问题也日益受到关注,如何快速准确地评价其疲劳寿命成为近些年桥梁界研究的热门课题。论文对预应力混凝土箱梁桥腹板及多跨钢筋混凝土梁桥的疲劳问题开展了系统地研究,分别提出了预应力混凝土箱梁桥腹板及多跨钢筋混凝土桥梁疲劳寿命评估方法,以便应用于工程实际。具体研究内容与成果如下:(1)通过总结预应力混凝土箱梁桥发展、箱梁桥结构分析理论、腹板斜裂缝成因、腹板疲劳问题研究现状,指出了现有研究中的不足。(2)查阅大量文献,通过介绍混凝土及钢筋的S-N曲线、仅考虑竖向剪力作用的腹板疲劳特性及横向效应下箱梁腹板的疲劳特性说明预应力混凝土箱梁桥的疲劳特性。给出了箱梁腹板疲劳寿命的具体含义。(3)结合箱梁的受力特点,基于梁杆有限元模型、变角度桁架模型及平面框架模型,提出了一种箱梁桥结构简化分析方法。为了准确反映腹板混凝土开裂后箍筋应力的情况,提出了考虑裂缝影响系数的箍筋应力计算公式,同时提出了考虑轴重、裂缝深度、梁高的裂缝影响系数的参数分析方法。基于线性疲劳损伤累积理论及箱梁桥结构简化分析方法,提出了预应力混凝土箱梁桥腹板疲劳寿命评估方法。通过实例研究,探讨了裂缝深度、箱梁横向效应、车辆与预应力耦合作用等对疲劳寿命计算结果的影响。(4)简单地介绍线弹性断裂力学的基本概念。由于现有疲劳寿命评估方法不能充分考虑裂纹萌生阶段及裂纹扩展阶段的寿命,提出了损伤—断裂理论的钢筋混凝土桥梁疲劳寿命评估方法。通过对某旧桥疲劳寿命评估的研究,分析对比了损伤力学,断裂力学及损伤—断裂理论三种方法计算结果的差异,说明了损伤—断裂理论方法的合理性。
[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.
【学位授予单位】：天津大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U441.4

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