【作者】 吴铭；

【导师】 刘元久；

【作者基本信息】 西南交通大学 ， 桥梁与隧道工程， 2008， 硕士

【摘要】 近几年来,随着我国城市交通基础设施和高速公路迅猛发展,城市中跨越道路的人行天桥大量涌现。传统的钢筋混凝土桥有碍景观,跨度受限,钢箱梁结构的桥用钢量太大,迫切要求我们研制出一种新的人行天桥结构。这种结构应该和现代化的都市在景观上相协调,实现各种平、立、剖面的造型,并要经济美观。空腹式网架人行天桥就满足上述要求,而且已经在应用于实际工程。近年来网架结构倒塌事故时有发生,而且破坏前无明显预兆,因而有必要对其承载力进行分析。本文利用ANSYS软件对空腹式网架人行天桥进行了承载力分析。本文研究的内容有以下几方面:1.对成桥状态进行了强度和刚度分析;2.然后对结构进行了四种工况的追踪分析,考虑残余应力和非线性,做出了Factor-δ曲线,确定结构的极限承载力,并得出结构杆件的屈曲破坏顺序。3.判断风载对极限承载力大小的影响。4.分析了结构中几个典型的螺栓球节点,通过应力分析,判断球节点会不会先于杆件破坏。通过上述研究,可以得到以下结论:(1)主要受压杆件的连续失稳将导致整个网架的溃坍,其破坏具有突然性。(2)一般来说,网架的受压杆件,尤其是三层网架结构中受压腹杆的失稳破坏将终止网架的承载能力的继续增加;而受拉杆件的屈服将不影响网架的继续承载。压杆的破坏所造成的邻近区域的杆件内力重分布现象十分严重。(3)设计中有意识地采取弱拉杆强压杆的措施,让受拉杆件率先破坏,并使这种趋势有一定程度的延续,这样可以使网架的塑性得到发展,从而有效地提高网架的极限承载能力。(4)螺栓球节点在球体与螺栓或套筒接触处会产生的应力集中现象,需要特别注意,采取适当措施,避免球节点先于杆件破坏而降低了结构的承载能力。更多还原

【Abstract】 With the rapid development of Urban Transportation Infrastructure and high-way in our country recently, the pedestrian bridges for span the road were constructed abundantly. As the traditional Reinforced Concrete Bridge is a hindrance to the view, the span is limited,and the consumption of steel material of Box Beam Structure is too large,it is exigent to develop a new Structure of pedestrian bridges. This structure should be harmonize with the modern city. Achieve all kind of plane ,vertical and section structure pattern and should be economical,beautiful. Open-Web Space Truss Pedestrian Bridge can meet demands mentioned above,and has been used in the engineering.In recent years, Grid structure collapse accidents often occurs there are no significant premonition before structure failure,so it is necessary to analyze the carrying Capacity of this structure. This paper applies Ansys to analyze the carrying capacity of Open-Web Space Truss Pedestrian Bridge. The contents of this dissertation are: 1 .Analyse the strength and stiffness of finished bridge state. 2.Tracing analyze the structure state in four Condition. Generating "Factor-δ"curve by considering residual Stress and nonlinearity to ascertain the ultimate carrying capacity of the structure. 3.Analyze the effect of Wind load to the ultimate carrying capacity. 4.Some typical spherical nodes were analyzed. It was shown that the spherical node should not failure than the bar component. Based on above analysis, some conclusions were drawn as following.(1) Domino effect caused by unstability of the main compression bar can result in the collapse of the grid,and the collapse is abrupt.(2) Generally,the compression bar of the grid, especially the unstable failure of compression web bars in a three-layer space truss will terminate the icrease of grid’s carrying capacity and the yielding of tension bar will not effect this kind of carrying capacity. Compression bar collapse result very serious internal force redistribution in the neighboring region .(3) Using the weak tension bar and strong compression bar consciously in design, let the tension bar collapse first and make this trend had certain extent of continuity, this can keep the plasticity of grid to develop, and effectively raise the ultimate carrying capacity.(4) Bolt-sphere joints in where the ball and bolt or sleeve contact will occur the phenomenon of stress concentration. It requires special attention and takes appropriate measures to prevent the spherical joint collapse before the bar, consequently reduce the carrying capacity of the structure.更多还原