不同荷载形式的双室箱梁剪力滞效应分析

发布时间：2018-03-24 09:36

本文选题：双室箱梁　切入点：剪力滞效应　出处：《长安大学》2015年硕士论文

【摘要】：随着我国铁路、公路等基础交通设施建设的迅猛发展,桥梁工程逐步向大跨度、宽体薄壁方向改进,研究人员经过行业实践经验及理论论证,发现箱形截面梁与其他截面梁相比具有较为优异的受力特性,倍受桥梁设计师的青睐。但是大跨度、宽体薄壁箱梁仍然存在理论计算盲点及误区,在承受竖向荷载时,由于其翼缘板剪切变形在横向的不均匀分布所引起的剪力滞效应问题,平截面假设已不在成立,运用初等梁理论计算纵向正应力已无法表征箱形梁的实际受力状况。大量的理论论证和现场试验调查发现,很多箱形梁出现裂缝的原因就是设计中未考虑剪力滞效应,造成设计应力与实际应力状态不相符,为箱形截面梁的安全耐久运营造成隐患。箱形梁剪力滞效应问题已经引起广大研究人员的重视。通过能量变分法的最小势能原理,推导带翼缘板双室矩形截面梁在简支、悬臂体系下分别作用集中荷载和均布荷载的应力应变计算式。引入附加弯矩概念,考虑轴力自平衡条件,推导竖向挠度计算式。剪力滞效应影响下的双室矩形箱梁竖向挠度有两部分组成,即初等梁弯曲挠度和剪力滞效应附加挠度的叠加。运用有限元分析软件Midas/FEA板单元结构建立数学模型,将计算结果与理论分析计算结果加以对比,相互验证,并将计算结果与初等梁弯曲理论做对比。不同的结构形式、加载方式对箱形梁剪力滞效应的影响是不同的,分别选取简支结构、悬臂结构的双室箱形梁,分别作用集中荷载和均布荷载,且每种荷载考虑三种荷载工况,用有限元分析软件建立数学计算模型,得出最不利截面的纵向正应力值,与初等梁弯曲理论计算的纵向正应力值相除,所得的结果就是箱梁剪力滞系数。对剪力滞系数进行论证分析总结,得出不同加载方式对箱形梁剪力滞效应的影响作用,以及纵向正应力的横向分布规律,以此找出箱形梁危险截面的最不利点和最不利的荷载工况,作为结构设计的控制点。选取跨度为40m的钢筋混凝土带悬臂板双室矩形等截面箱梁为计算算例,采用通用有限元分析程序MIDAS/FEA建立箱形梁桥梁单元数学模型,分析其在不同荷载作用下简支、悬臂梁的正应力的横向分布和挠曲变形规律。
[Abstract]:With the rapid development of railway, highway and other basic transportation facilities in our country, the bridge engineering is gradually improved in the direction of large span and thin-walled body. It is found that box section beam has more excellent mechanical characteristics than other section beams, and is favored by bridge designers. However, there are still theoretical blind points and misunderstandings in theory calculation for large-span, wide-body thin-walled box girder, which are subjected to vertical load. Due to the shear lag effect caused by the transverse inhomogeneous distribution of the flange plate shear deformation, the plane section hypothesis is no longer valid. Using the elementary beam theory to calculate the longitudinal normal stress can no longer represent the actual stress state of the box beam. A large number of theoretical arguments and field tests have found that the reason for the cracks in many box beams is that the shear lag effect is not taken into account in the design. As a result, the design stress does not accord with the actual stress state, which causes hidden trouble for the safe and durable operation of the box section beam. The shear lag effect of the box beam has attracted the attention of the majority of researchers. Through the principle of minimum potential energy of the energy variational method, The formulas for calculating stress and strain of double-chamber rectangular section beams with flange plates acting on concentrated load and uniform load respectively under simply supported and cantilever systems are derived. The concept of additional bending moment is introduced and the self-equilibrium condition of axial force is considered. A formula for calculating vertical deflection is derived. The vertical deflection of a double-chamber rectangular box girder under the influence of shear lag is composed of two parts. That is, the superposition of the bending deflection of elementary beam and the additional deflection of shear lag effect. The mathematical model of Midas/FEA plate element structure is established by using the finite element analysis software, and the calculated results are compared with the calculated results of theoretical analysis, and the results are verified by each other. The results are compared with the bending theory of elementary beam. The effects of different structural forms and loading modes on the shear lag effect of box beam are different. The concentrated load and uniform load are acted on respectively, and each load takes into account three load conditions. The mathematical calculation model is established by using finite element analysis software, and the longitudinal normal stress of the most unfavorable section is obtained. Divided from the longitudinal normal stress value calculated by the elementary beam bending theory, the result obtained is the box girder shear lag coefficient. The effect of different loading modes on the box girder shear lag effect is obtained by the demonstration, analysis and summary of the shear lag coefficient. And the transverse distribution of longitudinal normal stress, so as to find out the most disadvantageous point and the most unfavorable load condition of the dangerous section of box beam. As the control point of structural design, the box girder with double room and rectangular section with cantilever slab with span of 40 m is selected as an example, and the mathematical model of bridge element of box beam is established by using the general finite element analysis program MIDAS/FEA. The normal stress distribution and flexural deformation of simply supported cantilever beam under different loads are analyzed.
【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U441

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