【作者】 罗涛；

【导师】 贺拴海；

【作者基本信息】 长安大学 ， 桥梁与隧道工程， 2010， 博士

【摘要】 弯钢箱梁桥具有外形简洁美观、结构自重轻、受力性能好、抗扭刚度大、加工方便、施工期短、总体造价不太高、能够很好地适应地形地物限制要求等优点,在城市高架桥、立交桥等大型交通枢纽中,尤其在跨线、跨越地裂缝等特殊场合下应用非常广泛,发展前景非常广阔。对于大曲率连续弯钢箱梁桥的研究有着重要的现实意义。本文对于大曲率连续弯钢箱梁桥的极限承载力和剪力滞效应进行了系统的研究。首先,对于大曲率连续弯钢箱梁桥结构承载力的概念、类型和稳定问题的类型、分析原则、计算方法以及极限承载力的求解技术、剪力滞效应的基本概念等分别进行了探讨。其次,运用有限元建模对结构极限承载力进行全过程分析,包括容许应力控制下承载力分析、稳定屈曲特征值分析、非线性状态结构极限承载力分析。把加劲肋的面积平摊在箱梁盖板上,将钢箱梁简化为普通箱梁,再采用变分法求解,并与空间有限元法求解进行对比,提出无悬臂板钢箱梁剪力滞系数的近似计算方法。然后,根据实桥结构的材料特性、空间尺寸、连接方式等,按照1：10的比例制作了全桥缩尺模型,用该模型桥进行试验研究。通过试验和理论计算结果的分析对比,来研究弯钢箱梁桥的破坏形态、极限承载能力以及剪力滞效应的变化规律。最后,根据理论计算结果和试验测试结果的分析对比得出相关结论。弯钢箱梁模型桥最不利截面为5000mm跨跨中截面。模型桥破坏时5000mm跨跨中截面底板焊缝处、外侧腹板焊缝处及内侧腹板处均出现宽度为2～5mm的裂缝。模型桥在集中荷载工况下的最小承载力为63kN,均布荷载工况下的最小承载力为45kN/m2；而模型桥在对应于实桥设计荷载的试验荷载作用下的最大应力为29.61MPa。由相似关系可知,在弹性范围内结构的承载力远大于其设计荷载。考虑材料非线性和几何非线性等因素,集中荷载作用下结构的实际极限承载力为156.7kN,均布荷载作用下结构的实际极限承载力为111 kN/m2。而实桥设计荷载对应的模型桥试验荷载为11.41kN,即模型桥的安全系数达到13.7。模型桥结构在稳定分析中以局部失稳为主,一般出现在腹板与横隔板处；稳定系数较大,在整个过程中不会出现失稳现象。无悬臂板钢箱梁由于自身的构造特点,钢箱梁桥截面纵向正应力沿横截面的变化幅度相对较小,变化规律比较复杂；针对受压区理论值与试验值之间的误差,建议采用β·λ作为受压区的应力提高系数。模型桥在线弹性、弹塑性、完全塑性状态下,跨中截面顶板在全塑性阶段剪力滞效应最明显,底板在全过程中剪力滞效应不明显；支点截面顶板在弹性阶段剪力滞效应最明显,底板在全塑性阶段较显著。无论是集中荷载或均布荷载作用下,对于同一个截面,正、负剪力滞效应可同时出现,对于每一个节点(顶底板与腹板相接处的测点),沿桥纵向正、负剪力滞效应均可能出现。在集中荷载或均布荷载作用下,单、双室模型与三、四室模型相比剪力滞效应相差不大,三、四室模型剪力滞效应较小；三室模型受支座反力影响较大,对支座处结构应加强设计。对于单箱四室截面模型,两种定义的曲梁剪力滞系数λ1、λ2区别不大,但λ1和λ2并不随着箱室数的增加而趋于一致。本文可为大曲率连续弯钢箱梁桥在设计计算中提供参考,并为钢桥规范的修订提供技术资料。更多还原

【Abstract】 The curved steel box girder has many advantages such as succinct and beautiful appearance, light structure weight, best stress performance, good torsion rigidity performance, manufacture process simply and construct in a short time, well meet the demand of the terrain limitation, also, the general cost is not very high and etc.. Therefore, it is widely used in city viaducts and crossroads. Especially in cross lines, cross ground crack such special occasions with brilliant development prospect. Then, there are important realistic meanings in the study on this kind of bridge.In this paper, it has fully research on the ultimate load carrying capacity and the shear-lag effect of the continuous steel box girder with large curvature. First, there is a discussion about the concept of the structure load carrying capacity, type, stability, analysis principle, calculating method and the method to solve the ultimate load carrying capacity, the basic concept of shear-lag effect, etc.. Second, by using the finite element to analyzing the structure ultimate carrying capacity through the whole process. Including analysis of load carrying capacity under the allowable stress control, steady bucking eigenvalue, nonlinear stated ultimate load carrying capacity. Divide the stiffener area to the box girder cover plate equally, and then simplify the steel box girder to the ordinary box girder. Adopt calculus of variations to solve the problem and compare with space finite element. Thus, put forward the approximate calculation of shear-lag coefficient for the non-cantilever plate steel box girder. Next, according to space size, material characteristic, connection way of the original bridge, make the 1/10 of the proportions model bridge. By analyzing the result of experiment and theory calculation to research the rules of the mode of failure, the ultimate load carrying capacity, and the spear-lag effect. At last, according to the experiment and theory results to draw some related conclusions. The most unfavorable section of the carved steel box girder is 5000mm span middle section. There are 2-5mm cracks in width appeared in bottom board weld of the middle section, the outside web weld and the inside web weld in that section when the model bridge is destroyed. Under the concentrated load condition, the minimum load carrying capacity of Model Bridge is 63kN; under the uniform distributed load condition, the minimum load carrying capacity is 45kN/m2; although, the maximum stress of the model bridge which correspond in actual bridge design load test is 29.61MPa. It can be known from elastic range that structure load carrying is over than design load. Considering the factors such as material nonlinear and geometry nonlinear that under the concentrated load condition, the actual ultimate load carrying capacity of structure is 156.7kN, under the uniform distributed load condition, the actual ultimate load carrying capacity is 111kN/m2.The design load of actual bridge correspond in model bridge test load is 11.41kN. In the other word, the safety coefficient of the model bridge is up to 13.7. The structure of the model bridge may lose stability partly in stability analysis. Usually in web and cross board. With highly safety factor, it will not appear lose stability phenomenon. Because of the structure feature of non-cantilever plate steel box girder, the changing range of steel box girder section’s vertical normal stress along with cross section is not very obvious. And the changing rule is more complicated; Due to the compressive region error between theory value and test value, the suggestion is adoptβ-λ, as the compressive region to enhance the stress coefficient. Also this text includes the study of shear-lag effect of the model bridge in elasticity, elasticity and plasticity, complete plasticity.Under the complete plasticity state, the span middle section has the best performance of shear-lag effect, and therefore, the bottom board has not obvious performance through the whole process; On the other hand, the pivot top section board has best performance of shear-lag effect under the elasticity state, the bottom board does a good job on the complete plasticity state either. No matter under the action of concentrated load or uniform distributed load, as the same section, plus or minus shear-lag effect can appear at the same time. Every joint along the bridge vertical direction, plus or minus shear-lag effect may appear at the same time. Under the action of concentrated load or uniform distributed load, there are not much differences between single、double compartments models and three、four compartments model of shear-lag effect actually. The shear-lag effect of three、four compartments model is much low; As the opposite stress of the third compartments model is much strong, thus, we need to enhance structure design at the rack. For the single box forth compartments section model, the two definitions of the curved girder shear-lag effect coefficient-λ1,λ2 are nearly same, but bothλ1,λ2 will not become the same with the number of compartments had been added.This text can offer references in calculating of design for the continuous steel box girder with large curvature and offer the technical data for criterion revision of steel bridge.更多还原