【作者】 程海根；

【导师】 强士中；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2003， 博士

【摘要】 剪力滞问题在很早以前就有学者对其进行研究，当时局限于航空领域的金属结构方面，直到20世纪70～80年代，由于忽略剪力滞效应导致多座桥梁破坏才引起各国学者的注意。经过20多年的发展，对剪力滞问题的研究也取得了一些成果，解决了部分实际工程问题，但许多问题并没有完全得到解决。随着我国交通事业的发展，在一些新建桥梁中有关剪力滞的新问题不断出现，需要进一步的研究。本文针对等截面箱梁、变截面箱梁、组合梁以及斜拉桥箱型主梁的剪力滞效应展开分析，主要就以下几个方面进行了研究。 针对等截面箱梁在荷载作用下考虑剪力滞效应时的变形特点，根据箱梁纵向位移函数，采用基于能量变分法基础上的最小势能原理推导出系统的总势能表达式，然后通过变分法得到带有不同边界条件的一组微分方程。对于变截面箱梁，利用等截面箱梁所得到的微分方程和边界条件演化为变截面箱梁的微分方程，采用差分法来求解变截面箱梁的微分方程和相应的边界条件。结合叠加原理，可以将上述方法应用于求解连续梁的剪力滞效应。通过试验和计算分析可知，悬臂梁和连续梁在均布荷载作用下，由于剪力滞引起的附加弯矩沿跨度方向出现变号现象，导致负剪力滞效应出现。但悬臂梁在集中力作用下却没有负剪力滞现象出现，说明负剪力滞现象和梁的约束条件以及外荷载作用形式有关。通过分析可知，影响箱梁剪力滞效应的主要因素有截面形式、宽跨比、约束条件以及荷载形式等因素，其中宽跨比对剪力滞效应的影响最大。 由于钢—混凝土组合箱(T)梁中混凝土材料具有收缩、徐变的特点，且钢与混凝土板之间的连接件并非完全刚性，两者之间存在滑移，因此钢—混凝土组合梁的剪力滞效应具有时间效应。针对组合梁上述特点，在一定的假设条件下，笔者提出了组合梁考虑剪力滞效应时的纵向位移模式。根据所提出的位移模式，结合虚功原理推导出组合梁剪力滞效应微分方程以及相应的边界条件。通过算例分析可以看出，钢—混凝土组合梁剪力滞效应受剪力连接件刚度、环境相对湿度等因素的影响。受压翼缘混凝土板的应力随着时间的增加而减小，但减小的幅度随剪力连接件的刚度增加而减小。环境相对湿度对受压翼缘混凝土板应力的影响也有此规律，即应力减小的幅度随环境相对湿度的增加而减小。 斜拉桥主梁在荷载作用下承受弯矩与轴力的共同作用，由于轴向力的存在，分析其剪力滞效应不同于一般的箱型截面。根据小变形理论和叠加原理，将弯矩和轴力作用分开处理，利用能量变分法来求解弯矩和轴力共同作用下的剪力滞效应，在分析弯矩作用时考虑了梁柱效应。通过算例分析可知，轴压比对剪兰二颐一、…一~国夔丝丝墨丝翅鱼塑通丝丝鱼一一一一一一一一力滞系数有影响，其中剪力滞系数人.随轴压比的增加而增加。 通过算例分析和试验研究证明，宽跨比是影响箱梁剪力滞效应的一个主要因素。箱梁剪力滞系数随着宽跨比的增加而增加，并且与轴压比有关，轴压比大时宽跨比的影响程度也大。其它诸如截面高度、翼板外伸板长度、截面形式等因素对箱梁剪力滞效应都有一定的影响，但影响的程度各有不同。更多还原

【Abstract】 Shear lag problems were studied by some scholars long before, where only the shear lag problems of the aviation structures were studied at that time. Until in the 1970s-1980s, some country scholars paid attention to shear lag problems due to neglecting shear lag effect which caused several bridges damaged. Some research outcomes about shear lag problems were attained and part of project problems were solved during^ the twenty years. With the development of communication, some new problems about shear lag effect appear continuously. These problems need farther research. In this dissertation, the shear lag effect is studied about the constant depth box girders, the variable depth box girders, the composite box girders and the main box girders of the cable-stayed bridges. The main contents are the followings.A general potential energy equation is derived according to the principle of minimum potential energy and a set of differential equations with different boundary conditions are derived according to differential method considering the deformation properties and the longitudinal displacement functions of the constant depth box girders under a load. As for the variable depth box girders, difference method is applied to solve the differential equations and the boundary conditions of the variable depth box girders, which are derived according to the differential equations of the constant depth box girder. Those methods can be applied to solve the shear lag effect of the continuous box girders with the principle of superposition. The negative shear lag effect of the cantilever and continuous girders appears due to the symbolic change of the additional bending moment caused by shear lag effect under a uniformly-distributed load. And the negative shear lag effect of the cantilever girders does not appear under a concentrated load, this is to say that the negative shear lag effect is related to the constraints and the load forms. According to the results of experiments and calculations, the main factors which have effects on the shear lag effect of the box girders are the cross-sectional forms, the width/span ratio, boundary conditions and load forms, especially the width/span ratio.The shear lag effect of the steel-concrete composite (T) girders is related to time due to the shrinkage & creep of concrete, and the slippage between the steel beam and the concrete slab which are joined by the part-rigidity shear connectors. The longitudinal displacement patterns of the composite girder are put forward by author according to its structural properties and hypothetic conditions. A set of difFerential equations and the corresponding boundary conditions are derived according to virtual work principle and the longitudinal displacement patterns. It is concluded that the rigidity of the shear connectors and the surrounding relativehumidity have effects on the shear lag effect of the steel-concrete composite girders according to the results of examples. The concrete slab stress of the pressed flange decreases with the increment of time. But the diminished stress value decreases with the increment of the shear connector rigidity. The surrounding relative humidity has the same effect on it as the shear connector rigidity. This is to say that the diminished value of the concrete slab stress decreases with the increment of the surrounding relative humidity.There are bending moments and axial forces at the girder sections of the cable-stayed bridges under loads. Due to the existence of the axial forces, the method of analyzing the shear lag effect of the cable-stayed bridges is different from that of analyzing the general box girders. The bending moments and the axial forces are separately considered according to little deformation theory and the principle of superposition. Energy differential method is adopted to solve the shear lag effect of the cable-stayed bridges caused by the bending moments, where the beam-column effect is considered. According to examples, the shear lag coefficient has relation to the applied axial force/u更多还原