【作者】 王俊峰；

【导师】 黄平明；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2022， 博士

【摘要】 我国公路混凝土桥梁众多,部分桥梁服役时间较长,病害频发,工作重心正由建设向运维转移。在役混凝土桥梁的管养工作可以分为两大部分:(1)当前时刻混凝土桥梁的服役状态评估;(2)混凝土桥梁的长期性能预测。对于混凝土桥梁而言,其长期承担车辆荷载的反复作用及环境荷载的侵蚀。加之车辆荷载水平不断攀升、充分发挥材料性能的设计理念不断深入,导致混凝土桥梁的疲劳问题越来越突出,影响其正常服役状态与预期使用寿命,成为管养工作中不可避免的重要因素。鉴于此,本文开展了足尺混凝土梁静力及疲劳破坏试验,针对混凝土桥梁疲劳寿命预测与裂缝分布分形特征开展研究,进而协助该类结构的性能评估及管养政策制定。论文主要研究内容和结论如下:(1)以某在役混凝土梁桥拆除构件为试验对象,开展多组静力及疲劳破坏试验。首先对试验梁的外观技术状况进行检测,并对主要材料进行取样试验,梁体技术状况良好。详细介绍了试验全过程,揭示了该类构件在静力及疲劳荷载下各项力学性能指标的发展规律,为后续的疲劳寿命预测提供基础S-N曲线及为裂缝分形特征研究积累试验数据;(2)以车辆动态称重数据为来源,基于K-means++无监督分类算法、马尔可夫链蒙特卡洛模拟方法及Copula理论,建立了联合车型分类及参数相关性的多车道随机车流模拟方法,最后以某八车道高速公路动态称重数据进行案例分析,为后续车辆加载奠定基础。实例分析表明本文提出的车型分类方法效果较好,考虑车型序列相关性后的模拟车流可以准确反映实测车流的真实结构,考虑轴重、轴距相关性后的车辆总重分布及全轴距分布较传统方法更接近真实分布;(3)针对混凝土桥梁的荷载及抗力时变特性,分别建立时变车辆荷载模型、时变路面不平度模型及时变钢筋锈蚀模型,为疲劳寿命预测奠定基础。首先收集我国各地高速公路车辆荷载统计数据,估计车流量增长模型的参数,提出车型结构的演变模型。然后基于国际路面不平度指数衰变规律,推导路面粗糙度随时间的演变模型。最后根据混凝土桥梁所处的环境不同,分别建立钢筋锈蚀碳化模型及氯离子侵蚀模型;(4)对经典疲劳损伤累积准则进行综述,选取P-M准则作为基本准则,考虑每一级循环荷载所造成的疲劳损伤对下一级加载的影响,获得损伤材料的S-N曲线,提出改进疲劳损伤累积算法,并利用两组带筋混凝土梁变幅疲劳试验对其进行验证;最后融合时变车载及钢筋锈蚀模型建立混凝土桥梁疲劳寿命预测方法,并以某在役桥梁为例进行分析。结果表明改进疲劳损伤累积算法的预测精度较常规算法提升较大,本文的预测方法充分考虑了混凝土桥梁疲劳全寿命周期内的时变因素,预测结果更加合理;(5)开展混凝土梁桥裂缝多重分形方法的使用流程及适用性研究,基于足尺混凝土梁破坏试验数据对裂缝分布分形特征进行分析,提出基于裂缝分形特征的混凝土桥梁损伤分级谱,拟合分形维数与梁体力学性能的函数关系,建立混凝土桥梁裂缝分布分形维数发展模型。通过裂缝开展情况反演桥梁当前时刻的力学性能,凝练基于裂缝分形特征的混凝土桥梁服役状态快速评估思路,并通过实桥分析验证了该思路的有效性及便捷性。更多还原

【Abstract】 There are many highway concrete bridges in China,most of them have been in service for a long time.The center of work gradually shifts from construction to the maintenance.The maintenance work of concrete bridges in service can be divided into two parts :(1)evaluation of the service status of concrete bridges at the current moment;(2)long-term performance prediction of concrete bridges.Concrete bridges bear the long-term erosion of vehicle load and environmental load.Due to the rising vehicle load and the implementation of design concept of making full use of material properties,the fatigue of the concrete bridge is becoming more and more outstanding,which affects the normal service condition and its expected service life,which is an inevitable and important factor in the maintenance work.In view of this,the static and fatigue experiments on full-scale concrete beams were carried out,and fatigue life prediction and crack fractal characteristics of concrete bridges were studied,so as to assist the performance evaluation and management policy formulation of such structures.The main research contents and conclusions are as follows:(1)Several static and fatigue experiments on the dismantled members of a concrete beam bridge in service were carried out.Firstly,the appearance and technical condition of the test beams were detected,and the performance tests of main materials were conducted.The experiment beams were in good technical condition.The process of experiments was introduced detailedly.The development law of each mechanical property index was demonstrated.The basic S-N curve was provided for the fatigue life prediction of concrete bridges.And the crack database was accumulated for subsequent study on fracture fractal characteristics.(2)Taking the data from weigh in motion as the data source,a multi-lane random traffic flow simulation method based on unsupervised classification algorithm “K-means++”,Markov Chain Monte Carlo simulation method and Copula theory was established.An eight-lane expressway was used for case analysis,laying the foundation for subsequent vehicle loading.The case analysis showed that the simulated traffic flow considering the correlation of vehicle sequences can accurately reflect the real structure of the traffic flow,and the distribution of total weight and full wheelbase considering the correlation of axle load and wheelbase were closer to the real distribution than the traditional method.(3)According to the time-varying characteristics of load and resistance of concrete bridges,the time-varying vehicle load model,road roughness model and steel corrosion model were established,which lays the foundation for the fatigue life prediction.Firstly,the statistical data of vehicle load in some areas of China were collected,the parameters of the growth model of traffic volume were estimated,and the evolution model of traffic structure was put forward.Then the evolution model of road roughness was derived based on the decay law of international roughness index.Finally,according to the environment of the concrete bridge,the carbonization model and the chloride erosion model were established respectively.The corrosion rate of the carbonization model was smaller than that of the chloride erosion model.(4)The classical fatigue damage accumulation criteria were reviewed,the P-M criterion was selected as the basic criterion.The S-N curve of the damaged material was obtained by considering the influence of the fatigue damage of each stage load on the next stage,and the improved fatigue damage accumulation algorithm was proposed.The algorithm was verified by two fatigue experiments of concrete beams.Finally,the prediction method of fatigue life of concrete bridges was established by integrating the model of time-varying load and corrosion of reinforcement,and a bridge in service as a case to analyze.The results showed that the prediction accuracy of the improved cumulative fatigue damage algorithm was higher than that of the conventional algorithm.The method in this paper fully considers the time-varying factors of the whole life cycle of concrete bridges,and the prediction results were more reasonable.(5)The application process and applicability of multifractal method for cracks on concrete beam bridges were studied.Then the fractal characteristics were analyzed based on the experimental data,the function relations between fractal dimension and the mechanical behavior were fitted.The development model of fractal dimension of concrete bridge cracks was established.A rapid evaluation method of service status of concrete bridges based on the fractal characteristics of cracks was proposed,and the validity and convenience of the idea were verified by the analysis of a real bridge.更多还原