高矢跨比索拱结构体系设计与研究

Design and research of high rise-span ratio cable arch structural system

以中铁青岛世界博览城十字展廊工程为背景,对高矢跨比索拱结构的力学性能进行了研究,发现索拱结构可有效改善高矢跨比纯拱结构的力学性能,尤其是风荷载作用下水平向抗侧刚度得以显著的提高。采用三角形刚性撑杆的索拱结构力学性能改善最为显著,但张拉构造措施较为复杂,且必然存在一定的预应力损失,于是提出了采用三角形柔性撑杆的弦撑式索拱结构,并进一步探讨了影响此结构形式力学性能的多个关键因素。通过对索桁架顶部结构高度取值研究,发现该值在一定区间变化时,其中起控制作用的性能目标并无显著影响。通过对上弦梁分格数量和尺寸研究,发现随着网格数量不断增加,上弦梁构件应力比逐渐降低。当上弦梁拱脚根部以上区域分格数量超过8时,构件应力比趋于稳定。对拱脚支座水平刚度进行研究,结果表明高矢跨比索拱结构对其边界水平向刚度的要求较低,支座刚度对索拱结构力学性能的影响,实际工程中多数情况下可以忽略。通过对支座是否允许滑动和不同的滑动时机分析,发现索拱结构支座允许滑动,将导致外部荷载作用下支座滑移幅度过大,支座节点难以处理。下弦索可施加的索力有限,无法满足腹索索力始终不松弛的性能目标。最后建议索拱结构两侧均采用不可滑动的铰接支座,并对下部支撑结构进行必要的施工阶段承载力验算,从而保证索拱结构的安全。

Taking the Qingdao World Expo City Cross Gallery Project by China Railway Engineering Group as the background,the mechanical properties of the high rise-span ratio cable arch structure were studied,and it was found that the cable arch structure can effectively improve the mechanical properties of the high rise-span ratio cable arch structure,especially the lateral stiffness of the horizontal direction under the wind load.The mechanical properties of the cable arch structure with triangular rigid struts were improved most significantly,but the tensioning structure measures were complicated and there was a certain loss of prestress.Therefore a chord-supported cable arch structure with triangular flexible struts was innovatively proposed,and a number of key factors affecting the mechanical properties of this structure were further discussed.Through the study of the value of the top structure of the cable truss,it is found that when the value changes in a certain interval,there is no significant influence on the performance objectives of the control function.Through the research on the grid size and scale of the upper string beam,it is found that as the number of grids continues to increase,the stress ratio of the upper string beam member gradually decreases.When the number of grids in the area above the root of the upper chord beam arch foot exceeds 8,the member stress ratio tends to be stable.Research on the horizontal stiffness of the arch foot support shows that the high rise-span ratio cable arch structure requires lower boundary horizontal stiffness.The impact of the support stiffness on the mechanical properties of the cable arch structure can be ignored in most cases in actual engineering.Through the analysis of whether the bearing is allowed to slide and the different sliding timings,it is found that the cable arch structure bearing is allowed to slide,which causes the bearing to slide excessively under the action of external load,and the bearing node is difficult to handle.The cable force that can be applied by the lower chord cable is limited,which cannot meet the performance goal of not slackening the abdominal cable force.Finally,it is suggested that non-sliding hinged supports should be used on both sides of the cable arch structure,and the necessary construction stage bearing capacity of the lower supporting structure should be checked to ensure the safety of the cable arch structure.