【作者】 孟江；

【导师】 贺拴海；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2013， 博士

【摘要】 近年来，随着我国经济的快速增长和交通事业的大力发展，人员和物资流动日益频繁，部分已建高速公路的交通量进入饱和状态甚至出现交通堵塞现象，需要对原有高速公路进行拓宽改建，因此产生了旧桥拓宽问题。当前国内外很多专家学者对高速公路桥梁拓宽改建做了较多的研究工作，且拥有很多比较成功的案例，但尚未对一些关键技术给出明确的指导意见，其中旧桥加宽工程中新桥与旧桥共同作用问题备受学术界及工程技术人员的关注。本文以高速公路上的典型桥梁为依托背景，针对目前旧桥拓宽过程中存在的一些关键问题，对旧桥拓宽方法、拓宽后新旧桥梁耦合受力分析、新旧桥梁上部混凝土收缩、徐变差异影响、下部基础不均匀沉降对上部结构受力的影响及控制方法等方面展开分析研究。具体完成以下主要工作：系统介绍了已有桥梁拓宽及衔接方法，并比较分析了各自的优缺点，在此基础上阐述了各拓宽及衔接方法的适用性。根据所得结果并结合依托工程的结构特点，提出了适合不同连接方法的拓宽拼接装配式梁桥的荷载横向分布计算方法。结合有限元分析软件ANSYS，通过荷载横向传递规律分析和依据内力变形分析两种方法，对拓宽桥梁通行能力进行分析。分析了影响旧桥主梁的荷载横向分布系数的各种因素；分析在刚接与铰接两种拓宽拼接形式下，旧桥主粱横向分布系数的变化。分析表明，拓宽后旧桥内侧边梁在活载作用下的挠度及内力均大大降低；不同衔接方式对旧桥主梁承载力的影响较小。应用ANSYS软件中的CREEP材料模拟徐变，通过有限元法对推迟拼接时间及用温度荷载模拟预应力与混凝土收缩应变进行拓宽后装配式桥梁的收缩徐变分析。分析表明，混凝土收缩徐变的龄期差将引起新旧桥变形差、内力差、新老混凝土结合面的局部应力，得出推迟拼接时间可有效改善混凝土收缩徐变差异对拓宽后桥梁的影响；收缩徐变差异对新梁内力的影响显著，该差异使拓宽桥梁发生横向变形，且离支点截面越远收缩徐变越显著。结合ANSYS软件建立了不同衔接方式拓宽装配式桥梁的有限元模型，对拓宽装配式桥梁发生基础沉降后，主梁产生的附加内力及沉降差对拓宽桥梁的影响分别进行了研究，并给出在活载和基础沉降共同作用下，衔接截面允许变形值。此外，根据不同拼接构造措施下上部结构所能承受的最大基础沉降值，提出新、旧桥梁基础沉降差容许值概念。通过基础沉降计算，给出不同计算理论下，各桥沉降值，将此值与上部结构沉降允许变形值进行比较。根据现场监测结果和理论分析结果表明，将新、旧桥梁的基础沉降差控制在容许值范围内是完全可能的。本文的研究成果已应用于西潼、西宝高速公路，也为以后其它高速公路中装配式梁桥的拓宽设计提供参考。更多还原

【Abstract】 In recent years, with the rapid development of China’s economy and the trafficindustry, the flux of people and goods becomes more and more frequent; someexpressways in use need to be rebuilt and expanded, because the traffic volume ofthese expressways has been saturated or oversaturated to cause traffic jam, thus thematter of widening old bridges arises. Although a great deal of researching work hasbeen carried out on the reconstruction of bridges on expressways in both China andother countries and there are many successful examples, no specific notions have beenset down on some key technologies. And the matter of joint function of the newbridge and the old bridge in old bridge widening projects has caught much attention inacademic filed and among engineering technicians. Based on typical bridges onexpressways and aiming at problems appeared on the reconstruction and wideningwork of bridges, the paper carried out researches on many issues, such as wideningmethod of bridges, coupling stress analysis of old and new bridges afterreconstruction, concrete shrinkage and creep discrepancy influence of old and newbridges, the influence of the base’s uneven settlement on structures and the controllingmethod. And the following work has been completed:The paper systematically introduces the widening and linking methods ofexisting bridges, analyzes their advantages&disadvantages and thereby explains theadaptability of various widening and linking methods. Pursuant to the result acquiredand the structural characteristics of the projects, the paper brings forward a methodto calculate load transversal distribution of coupling bridges suitable for variouslinking methods. Combining ANSYS, a finite elements analyzing software, the paperanalyzes the capacity of widened bridges through analysis on load transversaltransferring rules and internal force deformation. In addition, the paper also analyzesall kinds of factors influencing load transversal distribution coefficients and thechange of transversal distribution coefficient of the old bridge’s main girder. Theresult shows that the deflection and internal force of inner side girders of old bridgesare greatly reduced after reconstruction under the influence of live load, and theinfluence of various linking methods on the capacity of the old bridge’s main girder istrivial.By simulating creep with CREEP materials in ANSYS software, the paper analyzes the postponed coupling time with finite element, simulates pre-stressingforce and concrete shrinkage strain with temperature load, and carries out shrinkageand creep analysis on assembled bridges after reconstruction. The result shows that:The age difference of concrete shrinkage and creep will cause deformation differenceof old and new bridges, internal force difference, as well as partial stress on theconnecting surface of old and new concrete; the influence of shrinkage and creep onthe internal force of new girders are notable, which causes transversal deformation ofwidened bridges; and further from the pivot section, more notable the shrinkage andcreep.The paper creates a finite elements model of assembled bridges reconstructedwith various linking styles with ANSYS software, researches the influence ofadditional internal force produced by the main girder and the influence of settlementdifference on widened bridge after base settlement of assembled bridge afterreconstruction, and brings forward the allowable deformation value of linking surfaceunder the joint function of live load and base settlement. In addition, according to themaximum bearable base settlement value of upper structures built with variouscoupling methods, the paper brings forward the concept of allowable value of newand old bridges’ base settlement. Through calculating base settlement with variouscalculation theories, the paper gets the settlement value of different bridges andcompares them with the allowable deformation value of upper structure settlement.On-spot measurement result and theoretical analysis result show that it is completelypossible to control base settlement difference within allowable scope.Research result of the paper has been applied into Xi’an—Lintong and Xi’an—Baoji expressways; the paper also offers design reference for widening assembledbridges in other expressways.更多还原