基于多尺度有限元模型的下承式钢箱拱桥稳定极限承载力分析

发布时间：2018-05-24 16:58

本文选题：稳定 + 非线性　；参考：《合肥工业大学》2017年硕士论文

【摘要】：拱桥的拱肋在活载作用下为压弯构件,其稳定问题突出。本文以安徽淮南孔李淮河三跨连续下承式钢箱拱桥为工程背景,采用有限元方法,建立该桥的三维整体有限元模型,进行了线弹性稳定(分枝点失稳)和极限承载力(极值点失稳)计算和分析。鉴于钢桥由局部板件连接而成,受压的局部板件极易发生局部屈曲,依据薄板屈曲理论和加劲板屈曲理论,对主拱肋各截面加劲板件进行了局部弹性稳定的理论计算。最后,根据需要详细分析的部位,建立了孔李淮河大桥的多尺度有限元模型,进行了局部—整体相关屈曲的极限承载力计算,可供桥梁结构分析局部构件破坏参考。论文的主要研究工作和结论:1.建立了淮南孔李淮河大桥结构尺度的三维有限元模型,进行了整体弹性稳定和参数分析。结果表明,淮南孔李淮河大桥的主拱失稳的阶次靠前,是整体稳定的重点,桥面竖向荷载对弹性稳定结果影响比较大,横向风荷载影响较小。面内稳定性主要由拱肋面内抗弯刚度决定,面外稳定性主要由拱肋面外抗弯刚度决定,而拱肋扭转刚度对面内和面外弹性整体稳定性的影响都较小。2.考虑结构的几何和材料双重非线性,对淮南孔李淮河大桥整体极限承载力进行了计算和分析。结果表明,几何非线性对在该拱桥的极限承载影响较小,材料非线性是该拱桥整体极限承载力的控制因素。通过分析拱肋的屈服路径发现,主跨L/6处的拱肋和拱顶处的拱肋截面最先失效,是该桥拱肋极限承载力的关键部位。在稳定极限承载力状态下,拱肋关键截面的屈服所导致的截面抗弯刚度的改变和大变形,引起吊杆内力的重分布,并导致了拱肋关键截面的弯矩出现卸载现象。3.在桥梁极限承载力状态,此时作用的荷载非常大,部分局部板件会首先会发生局部屈曲,而传统的杆系有限元整体模型无法考虑局部板件的屈曲。论文根据前面整体极限承载力和局部稳定理论计算结果,确定小尺度建模的目标部位。然后,用板壳单元建立目标部位的局部板件尺度模型,用杆梁单元建立非目标部位的全桥的结构尺度模型;最后,采用位移协调方程实现其界面连接形成多尺度有限元模型。该建模思路可以为钢箱拱桥局部—整体相关屈曲极限承载力的研究提供建模参考。4.依据多尺度有限元模型,对孔李淮河大桥局部—整体相关屈曲极限承载力进行了计算分析。结果表明,所建立的多尺度有限元模型,可以实现局部板件尺度和整体结构尺度的协同计算,可以考虑局部板件屈曲和整体结构屈曲的相互作用,并可以详细揭示局部板件的失效模式。拱肋局部板件屈曲后,并不意味着拱肋立即丧失承载力,桥梁整体仍能继续承受更大的荷载,并且不同部位的局部屈曲对整体极限承载力的影响不同。
[Abstract]:The arch rib of the arch bridge is a bending member under the action of live load, and its stability problem is prominent. In this paper, based on the engineering background of the three-span continuous through steel box arch bridge in Huainan, Anhui Province, the three-dimensional integral finite element model of the bridge is established by using the finite element method. The linear elastic stability (branch point instability) and ultimate bearing capacity (extreme point instability) are calculated and analyzed. In view of the fact that the steel bridge is connected by local plates, local buckling of compressed local plates is easy to occur. Based on the theory of thin plate buckling and stiffening plate buckling, the local elastic stability of stiffened plates with different sections of the main arch rib is calculated based on the theory of thin plate buckling and stiffening plate buckling. Finally, the multi-scale finite element model of Kongli Huaihe River Bridge is established according to the location that needs to be analyzed in detail, and the ultimate bearing capacity of the local and global buckling is calculated, which can be used as a reference for the analysis of the failure of the local members of the bridge structure. The main research work and conclusion of this paper: 1. A three dimensional finite element model for the structural scale of Huainan Konglihuai River Bridge is established, and the overall elastic stability and parameter analysis are carried out. The results show that the order of instability of the main arch of Huainan Konglihuai River Bridge is the key point of overall stability. The vertical load on the bridge deck has a great influence on the elastic stability results, while the influence of the transverse wind load is relatively small. The in-plane stability is mainly determined by the in-plane bending stiffness of the arch rib, and the out-of-plane stability is mainly determined by the out-of-plane bending stiffness of the arch rib. Considering the geometric and material nonlinearity of the structure, the overall ultimate bearing capacity of the Lihuai River Bridge is calculated and analyzed. The results show that the geometric nonlinearity has little influence on the ultimate bearing capacity of the arch bridge, and the material nonlinearity is the controlling factor of the overall ultimate bearing capacity of the arch bridge. By analyzing the yield path of the arch rib, it is found that the arch rib at the main span L / 6 and the arch rib section at the top of the arch are the first failure, which is the key part of the ultimate bearing capacity of the arch rib of the bridge. Under the condition of stable ultimate bearing capacity, the bending stiffness and deformation of arch rib caused by the yield of key section of arch rib cause the redistribution of internal force of suspender and the unloading phenomenon of moment of key section of arch rib. In the state of ultimate bearing capacity of the bridge, the load acting on the bridge is very large, part of the local plate will first occur local buckling, but the traditional finite element global model of the bar system can not consider the buckling of the local plate. According to the calculation results of global ultimate bearing capacity and local stability theory, the target location of small scale modeling is determined in this paper. Then, the local scale model of the target part is established by using the plate and shell element, the structure scale model of the whole bridge at the non-target position is established by the bar and beam element, and the multi-scale finite element model is formed by using the displacement coordination equation to realize the interface connection. The method can be used as a reference for the study of the ultimate bearing capacity of local and global buckling of steel box arch bridge. Based on the multi-scale finite element model, the ultimate bearing capacity of local-global correlation buckling of Kongli-Huaihe River Bridge is calculated and analyzed. The results show that the multi-scale finite element model can realize the cooperative calculation between the local plate size and the global structure scale, and the interaction between the local plate buckling and the global structure buckling can be considered. The failure mode of local plates can be revealed in detail. The local buckling of arch rib does not mean that the arch rib loses its bearing capacity immediately, and the whole bridge can continue to bear larger load, and the effect of local buckling on the ultimate bearing capacity of the bridge is different.
【学位授予单位】：合肥工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U448.22;U441

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