独塔斜拉桥混凝土宽箱梁受力特性研究
发布时间：2018-07-31 18:57
【摘要】：由于宽箱梁翼缘板较宽,存在剪切滞后的现象,使得宽箱梁纵向正应力沿横向分布非均匀,即剪力滞效应。对于混凝土宽箱梁,如果在设计与施工中忽略剪力滞效应的影响,有可能出现应力集中导致混凝土开裂。因此对宽箱梁的剪力滞效应进行研究很有必要。本文依托南京六合跨滁河大桥工程,分析了混凝土宽箱梁的受力特性,重点研究了混凝土宽箱梁的剪力滞效应。本文首先综述了目前研究剪力滞的理论与方法。运用Midas/Civil建立斜拉桥空间杆系模型,进行受力特性分析,得到了几种不利状态下主梁的内力及应力分布规律。该桥主梁在承载能力极限状态和正常使用极限状态下均满足规范要求；主梁在承载能力极限状态下,主跨主梁弯矩受拉索影响较大,而边跨弯矩则主要受移动荷载影响。其次,采用Midas/FEA建立了斜拉桥实体单元模型,针对成桥恒载状态,通过提取主要典型截面的纵桥向正应力并绘制剪力滞系数曲线图,研究了主梁的剪力滞效应。由于斜拉桥主梁的剪力滞效应,使得纵向正应力沿横截面分布不均匀；变截面处顶板的剪力滞效应相对一般截面较强；变截面底板剪力滞效应受斜拉索影响较大,随着与斜拉索距离的增加逐渐减小；主跨和边跨的剪力滞效应的分布规律相似,但是边跨的剪力滞效应比主跨稍强。最后,用Midas/FEA建立参数化有限元模型,分析了横隔板厚度、横隔板间隔、倒角、顶板厚度、底板厚度、纵向预应力的大小、混凝土强度等主要参数对斜拉桥剪力滞效应的影响。通过对多个参数化有限元模型的对比分析可以看出,增大横隔板、顶板、底板厚度,减小横隔板间隔,增加倒角,都能够减小箱梁顶板的剪力滞效应；底板厚度的改变对箱梁剪力滞效应的影响较小；变换以上参数对宽箱梁底板的剪力滞效应影响均较小；纵向预应力减小了斜拉桥宽箱梁的剪力滞效应,对结构偏于有利,但是随着预应力值的加大,剪力滞系数改变的幅度会减小；混凝土强度的改变对于斜拉桥宽箱梁剪力滞效应几乎无任何影响。本文对独塔斜拉桥混凝土宽箱受力特性进行了研究,对类似截面形式的宽箱梁的设计和施工均有一定的参考价值。
[Abstract]:Due to the wide flange plate of the wide box girder and the phenomenon of shear lag, the longitudinal normal stress of the wide box girder is distributed inhomogeneously along the transverse direction, that is, the shear lag effect. If the shear lag effect is neglected in the design and construction of the wide concrete box girder, the stress concentration may lead to concrete cracking. Therefore, it is necessary to study the shear lag effect of wide box girder. In this paper, based on the Nanjing Liuhe Bridge, the stress characteristics of the concrete wide box girder are analyzed, and the shear lag effect of the concrete wide box girder is studied. In this paper, the theories and methods of shear lag are reviewed. The spatial bar system model of cable-stayed bridge is established by using Midas/Civil, and the internal force and stress distribution of the main beam under several unfavorable conditions are obtained. The main beam of the bridge meets the requirements of the code under the limit state of bearing capacity and the limit state of normal use, and the moment of the main girder of the main span is greatly affected by the cable, while the moment of the side span is mainly affected by the moving load under the limit state of the bearing capacity of the main beam. Secondly, the solid element model of cable-stayed bridge is established by using Midas/FEA. Aiming at the dead load state of the bridge, the shear lag effect of the main girder is studied by extracting the normal stress of the longitudinal bridge of the main typical section and drawing the curve of shear lag coefficient. Due to the shear lag effect of the main girder of the cable-stayed bridge, the longitudinal normal stress distributes unevenly along the cross section, the shear lag effect of the roof plate at the variable section is stronger than that of the general section, and the shear lag effect of the variable section bottom plate is greatly affected by the cable. The shear lag effect of the main span and the side span is similar, but the shear lag effect of the side span is slightly stronger than that of the main span. Finally, the parametric finite element model is established with Midas/FEA, and the influence of the main parameters, such as the thickness of transverse partition, the interval of transverse partition, the chamfer, the thickness of roof, the thickness of bottom slab, the size of longitudinal prestress and the strength of concrete, on the shear lag effect of cable-stayed bridge is analyzed. Through the comparison and analysis of many parameterized finite element models, it can be seen that the shear lag effect of box girder roof can be reduced by increasing the thickness of transverse partition, roof and bottom, reducing the interval of transverse partition and increasing chamfer. The influence of the thickness of the bottom plate on the shear lag effect of the box girder is small, the influence of the above parameters on the shear lag effect of the wide box girder bottom plate is small, and the longitudinal prestress reduces the shear lag effect of the wide box girder of the cable-stayed bridge, which is favorable to the structure. However, with the increase of prestressed value, the amplitude of shear lag coefficient will decrease, and the change of concrete strength has little effect on the shear lag effect of wide box girder of cable-stayed bridge. In this paper, the mechanical characteristics of concrete wide box of single tower cable-stayed bridge are studied, which has certain reference value for the design and construction of wide box girder with similar cross-section.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U448.27;U441
本文编号：2156530
[Abstract]:Due to the wide flange plate of the wide box girder and the phenomenon of shear lag, the longitudinal normal stress of the wide box girder is distributed inhomogeneously along the transverse direction, that is, the shear lag effect. If the shear lag effect is neglected in the design and construction of the wide concrete box girder, the stress concentration may lead to concrete cracking. Therefore, it is necessary to study the shear lag effect of wide box girder. In this paper, based on the Nanjing Liuhe Bridge, the stress characteristics of the concrete wide box girder are analyzed, and the shear lag effect of the concrete wide box girder is studied. In this paper, the theories and methods of shear lag are reviewed. The spatial bar system model of cable-stayed bridge is established by using Midas/Civil, and the internal force and stress distribution of the main beam under several unfavorable conditions are obtained. The main beam of the bridge meets the requirements of the code under the limit state of bearing capacity and the limit state of normal use, and the moment of the main girder of the main span is greatly affected by the cable, while the moment of the side span is mainly affected by the moving load under the limit state of the bearing capacity of the main beam. Secondly, the solid element model of cable-stayed bridge is established by using Midas/FEA. Aiming at the dead load state of the bridge, the shear lag effect of the main girder is studied by extracting the normal stress of the longitudinal bridge of the main typical section and drawing the curve of shear lag coefficient. Due to the shear lag effect of the main girder of the cable-stayed bridge, the longitudinal normal stress distributes unevenly along the cross section, the shear lag effect of the roof plate at the variable section is stronger than that of the general section, and the shear lag effect of the variable section bottom plate is greatly affected by the cable. The shear lag effect of the main span and the side span is similar, but the shear lag effect of the side span is slightly stronger than that of the main span. Finally, the parametric finite element model is established with Midas/FEA, and the influence of the main parameters, such as the thickness of transverse partition, the interval of transverse partition, the chamfer, the thickness of roof, the thickness of bottom slab, the size of longitudinal prestress and the strength of concrete, on the shear lag effect of cable-stayed bridge is analyzed. Through the comparison and analysis of many parameterized finite element models, it can be seen that the shear lag effect of box girder roof can be reduced by increasing the thickness of transverse partition, roof and bottom, reducing the interval of transverse partition and increasing chamfer. The influence of the thickness of the bottom plate on the shear lag effect of the box girder is small, the influence of the above parameters on the shear lag effect of the wide box girder bottom plate is small, and the longitudinal prestress reduces the shear lag effect of the wide box girder of the cable-stayed bridge, which is favorable to the structure. However, with the increase of prestressed value, the amplitude of shear lag coefficient will decrease, and the change of concrete strength has little effect on the shear lag effect of wide box girder of cable-stayed bridge. In this paper, the mechanical characteristics of concrete wide box of single tower cable-stayed bridge are studied, which has certain reference value for the design and construction of wide box girder with similar cross-section.
【学位授予单位】：南京理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：U448.27;U441
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