【作者】 林广平；

【导师】 黄卫；

【作者基本信息】 东南大学 ， 道路与铁道工程， 2006， 博士

【摘要】 钢桥面铺装作为大跨径桥梁建设的一项关键技术,是近几年来国内外的一个研究热点。疲劳破坏是钢桥面铺装层最主要的破坏形式之一。本文在回顾钢桥面铺装研究的基础上,结合多个大跨径钢桥面铺装工程研究课题,指出基于唯像学疲劳方程的钢桥面铺装层设计方法存在的局限性,从钢桥面铺装层在使用期间带裂缝工作的实际出发,采用断裂力学理论研究钢桥面铺装层的疲劳寿命。本文以正交异性钢桥面铺装层表面裂缝的疲劳扩展为研究对象,以正交异性钢桥面铺装层表面裂缝应力强度因子的计算方法、应力强度因子的变化规律和影响因素、Paris疲劳扩展模型的计算参数、铺装层疲劳寿命预测等为基本研究内容,具体做了以下几个方面的工作、并得到相应的成果:1、正交异性钢桥面系三维裂缝有限元模型的建立和应力强度因子计算在铺装层内引入三维表面裂缝,建立了带裂缝的正交异性钢桥面系有限元模型;构造了12结点三维等参奇异单元,并证明了该单元内应力、应变分布的r-1/2奇异性,将该奇异单元布置在裂缝前沿模拟奇异应力、应变场,计算得到了铺装层三维表面裂缝前沿的应力强度因子值;基于通用有限元软件的二次开发技术,编制了通用的命令流和程序,完成了建模和计算工作。2、正交异性钢桥面铺装层三维表面裂缝应力强度因子分析计算和对比了完好铺装层和带裂缝铺装层的正交异性钢桥面系模型的铺装层表面最大拉应变值,发现裂缝的存在使铺装层表面最大拉应变值减小,说明表面最大拉应变值不适合作为开裂铺装层疲劳破坏的控制指标,开裂铺装层的疲劳破坏由裂缝前沿奇异应力场强度所控制,以应力强度因子来表征;铺装层三维表面裂缝是复合型裂缝,等效应力强度因子反映了三种基本开裂模式的综合作用,文中同时计算和分析了三种基本应力强度因子和等效应力强度因子。根据应力强度因子沿裂缝前沿不同位置的变化,找到最大应力强度因子来代表整个裂缝前沿的应力强度因子,并根据应力强度因子值随轴载作用位置的变化规律,确定了带裂缝桥面系的轴载作用最不利荷位。正交异性钢桥面系众多结构参数都影响铺装层的受力状态,并影响到铺装层裂缝的疲劳扩展行为,表现为裂缝的应力强度因子随结构参数的变化而变化。通过大量的数值计算,分别探讨了正交异性钢桥面系的加劲肋开口宽度、加劲肋高度、加劲肋壁厚、加劲肋间距、横隔板厚度、横隔板间距、桥面板厚度、铺装层厚度、铺装层模量等众多结构参数对应力强度因子的影响规律。铺装层表面裂缝的扩展行为随着裂缝扩展的深度而变化,表现为表面裂缝的应力强度因子值是裂缝深度的函数。通过大量的数值计算和数据拟合,将表面裂缝应力强度因子表示为裂缝深度的二次多项式,二次多项式系数随桥面系结构参数的不同而变化,建立BP神经网络模型,以预测任意桥面系结构的表面裂缝应力强度因子二次多项式,BP神经网络的训练样本采用正交试验设计方法、依据工程实际选取。根据应力强度因子的深度函数式,确定了铺装层表面裂缝疲劳扩展的临界深度。3、建立和求解带铺装层钢箱梁多层热传导偏微分方程组,分析温度变化对铺装层表面裂缝疲劳扩展行为的影响裂缝的应力强度因子会随温度应力的变化而变化,反映了环境温度变化对裂缝疲劳扩展行为的影响。本文建立和求解了带铺装层钢箱梁的多层热传导偏微分方程组,在给定气候条件和桥面系热力学参数的条件下,得到了铺装层的温度分布;考虑沥青混合料应力松弛效应的条件下,推导了铺装层内温度应力计算公式,并计算了温度应力作用下的裂缝应力强度因子。计算分析表明,正常的日循环变温过程中,表面裂缝应力强度因子远小于材料的断裂韧性值,温度应力不会导致铺装层裂缝的失稳扩展,但会引起裂缝的疲劳扩展,而持续快速降温过程可能导致铺装层裂缝的失稳扩展,使铺装层发生脆性断裂破坏。4、正交异性钢桥面板第一体系应力对铺装层受力状态和裂缝扩展行为的影响正交异性钢桥面板作为主梁的上翼缘直接参与主梁的作用,桥梁自重、全桥车辆轴重等荷载使桥梁的主梁产生很大的内力,而使正交异性钢桥面板承受着巨大的第一体系应力。以初始应力模拟正交异性钢桥面板第一体系应力,将初始应力施加于局部钢桥面系模型的钢桥面板上,分析了正交异性钢桥面板第一体系应力对完好铺装层表面应变值的影响,文中定义了一个桥梁主跨影响系数,以定量表示正交异更多还原

【Abstract】 As a critical technology to the long span bridge construction, paving the steel bridge deck has become a research hotspot abroad and domestically in recent years. Based on the summarization of current research on the steel bridge deck surfacing, the limitation of the current designing method of the deck-paving was pointed out. Based on the fact that the deck-pavement works with cracks during its work-life, the fracture-mechanics theory can be applied to study the fatigue-life of the steel bridge deck pavement.In this thesis, the surface crack of the orthotropic steel bridge deck pavement was the research object. The variation and the effect parameters of the SIF (stress intensity factor) at the crack and the calculating parameters of the Paris’s model was the central researching content. combined with several research projects of the deck-paving, the following tasks was accomplished in this thesis:1 The finite element model of the steel deck system with a three-dimensional crack was created and the SIF of the crack was calculatedThe three-dimensional finite element model of the orthotropic steel bridge deck system with a surface-crack was established; the 12-noded three-dimensional singular element, the r-1/2 singularity of which was testified, was constructed. The 12-noded three-dimensional singular element being laid along the crack front to model the singular stress and strain field, the SIF was calculated. The general command flow and computer code was compiled to finish the modeling and calculation based on the secondary developing function of the general finite element software.2 The SIF of the surface crack of the orthotropic steel bridge deck pavement was analyzedThe maximum tensional strains of the pavement surface with or without a crack on the pavement were calculated and compared. It was found that the crack on the pavement can reduce the maximum tensional strain, which showed that the controlling index of the cracked pavement is not the maximum tensional strain, but the singular stress field intensity at the crack front. The surface crack of the pavement is the composite crack, the equivalent SIF reflects the composite effect of three basic cracking models; In this thesis, three basic SIF and the equivalent SIF were calculated and analyzed.The SIF changed along the crack front. Thus, the maximum SIF along the crack front was found and was regarded as the representation of SIFs along the crack front. The SIF varying with the loading position of the axle load was analyzed and the worst loading position of the vehicle axle load was determined.Lots of the structural parameters of the orthotropic steel bridge deck system affect the mechanical condition, thus affect the fatigue cracking of the pavement crack, which can be exhibited by the SIF varying with the parameters. Through amount of numerical calculation, the effect of all the structural parameters on the SIF was analyzed.The expanding state of the pavement crack changes with the cracking depth, which can be showed by that the SIF is the function of the crack depth. By amount of numerical calculation and data fitting, the SIF was expressed as the quadratic polynomial of the crack depth. The coefficient of the quadratic polynomial changes with the structural parameters of the deck system. To forecast the quadratic polynomial of any deck system, a BP neural network model was created.According to the expression of the SIF to the crack depth, the critical expanding depth of the pavement surface crack was determined.3 The multi-layered heat exchange partial differential equation group of the steel girder with pavement was built and solved. The effect of the varying temperature on the expand of the pavement surface crack was analyzedThe varying temperature can cause thermal stress in the pavement, and the crack SIF changes with the thermal stress, which indicates the effect of the varying temperature on the expanding of the crack. In this thesis, the multi-layered heat change partial differential equation group of the steel box girder with pavement更多还原