【作者】 张丽芳；

【导师】 朱金福；

【作者基本信息】 南京航空航天大学 ， 道路与铁道工程， 2009， 博士

【摘要】 目前,交通网络逐渐完善,公路桥梁数量激增,旧桥数量也随之增长,导致桥梁管理与维修任务日渐繁重。由于设计施工、长期受力、环境及自然灾害等各种因素影响,运营中桥梁的正常使用功能和安全性存在隐患和缺陷,桥梁管理部门必须借助合适的方法和手段尽早获知桥梁的状态,以提高桥梁的服务性能并避免桥梁垮塌等危及生命财产安全的事故发生。因此,如何快速、准确地实现桥梁评估成为桥梁养护管理的焦点,探索合适的方法对提高评估效率具有重要意义。本文以我国公路桥梁中常见的桥面连续简支梁桥为主要研究对象,应用理论分析及数值模拟方法探讨了该类桥梁的受力及变形特点,与普通简支梁桥的受力特点进行对比,为后续基于简支梁桥的评估打下基础。在分析简支梁弯曲刚度计算公式基础上,结合两片简支T梁室内试验,探讨了裂缝开展与刚度退化的关系,提取出裂缝平均开展高度和裂缝平均间距两个指标作为裂缝统计参数,并采用钢筋应变不均匀系数来表征刚度的退化。针对一室内试验模型梁开展数值仿真分析,通过相关分析得到裂缝统计参数与钢筋应变不均匀系数之间的回归公式,从而建立裂缝统计参数与刚度退化之间的关系模型,该模型与试验结果吻合良好。以改进和完善桥梁评估方法为目的,在分析旧桥安全性及使用性能影响因素的基础上,提出对桥梁进行安全性及使用性能的定量和定性评估方法。针对目前普遍应用的常权评估模型对评估指标间的均衡性反映迟钝现象,本文提出变权模糊综合评估方法,并建立相应评估模型。在承载力定量检算评估中,提出在对桥梁设计承载力进行理论计算的基础上,依据桥梁结构质量检测结果(缺损状况、材质状况与耐久性指标),标定截面折减系数Zd、构件状态恶化系数Zt对理论承载力进行修正得到估算承载力的方法;在安全性定性评估中建立了由承载力检算结果、实际活载状况及构件状况等因素评估安全等级的变权模糊综合评估模型。对使用性能的定量评估以裂缝宽度和挠度为指标,并结合调查资料对挠度限值加以修正;在使用性能定性评估中,建立了以刚度退化率、动力性能、交通状况及构件恶化状况作为评价因素集的变权模糊综合评估模型,其中对动力性能评估从理论和数值仿真角度出发,在研究车桥耦合振动方程基础上提出桥梁评估中动力性能应考虑桥面平整度、桥头引道沉降、梁的刚度退化等因素,并在Matlab下编制程序实现了车桥耦合振动的模拟计算,在分析计算结果基础上提出评估指标、等级划分标准及权重。最后将以上评估方法定制成评估表格并用于实桥的评估,完善了评估体系。更多还原

【Abstract】 At present, transportation networks are being well established, more and more bridges have been built and at the same time the number of old bridges also rises which leads to heavy work in management and maintenance. Due to the design and construction deficiency, loads, environment action and natural disaster, the bridges in service have fault in performance function and safety. Bridge management department should acquire the bridge status as soon as possible in order to improve the bridge service ability and avoid accident such as collapse. How to evaluate bridges quickly and accuately becomes the focal point, so it is important to search suitable bridge evaluating methods.Simply supported beam bridge with continuous deck is taken as research object, the performance of such type of bridge under loads is analyzed by theoretical and numerical method. By comparing with ordinary simple supported bridges, the evaluating of the aimed bridge can be simplified as simple supported bridge assessment with some modification.Based on the analysis of bending stiffness formula, and the experimental results of two T type simple supported beams, the relationship between crack development and the stiffness degradation is discussed. Crack average depth and spacing are taken as two indexes of crack statistics parameters, and non-uniformly distributed strain coefficient of reinforcement is used to present the degradation of stiffness. By numerical analysis of a rectangle beam, a regression equation of crack statistics parameters and non-uniformly distributed strain coefficient of reinforcement is obtained, so the relationship between crack statistics parameters and stiffness degradation can be established and it is verified by test results.In order to improve the assessment method of bridges, quantitative and qualitative evaluating systems of bridge safety and performance are carried out based on analysis of the factors which affect bridge safety and performance. To avoid the dullnesss in constant weight evaluation model which is widely used now, variable weight evaluation model is presented in this paper and used in the evaluating of bridges.In bearing capacity quantitative check, a method based on theory bearing capacity is presented. Theoretical bearing capacity is taken as basic value, then multiplied by section reduction coefficient Zd and structure condition deterioration coefficient Zt which is determined according to bridge investigation results. In safety evaluation, a fuzzy assessing model based on varied weight is established. The bearing capacity reduction degree which can be obtained in quantitative check and actual traffic condition, boundary condition and structure state are taken as assessing factors to obtain the safety grade. In quantitative assessment of service performance, maximum crack width and deformation of beam are taken as indexes and the limited deformation value is modified based on measured data. In qualitative assessment of service performance, a fuzzy assessing model is established with indexes of stiffness reduction rate, vibration property, traffic condition and structure deterioration condition. For assessing vibration property, the bridge and vehicle coupled vibration equation is studied and the results show that the pavement roughness, approach deformation and beam stiffness variation should be considered. Then calculation programming is made in Matlab software and the factors mentioned above are simulated. So the evaluation index, grade division and weight are proposed. At last, several tables are worked out for engineering application and they are verified by several actual bridges.更多还原