Study On Structural Systems In Long-span And Multi-tower Suspension Bridges

Multi-tower suspension bridges can realize the continuous super-long-span crossing and breakthrough the length limit of single span, which is the most feasible project in the cross-sea projects in the new century. But now, there are only a few construction examples, none of which are over 1000m all over the word. The 1080m Taizhou Yangtze river bridge and Ma an Shan Yangtze river bridge in China are under constructing. The main reason why this structural system has not been widely applied is that the grasp and understanding is not enough for the structure and there are many technical bottlenecks.Based on the summary of all-ready built examples and proposed design projects in domestic and abroad area, the problems on the actual application process are analyzed and the existing static and dynamic research situation are summed up.The calculation methods are summed up, based on which a multi-tower and a two-tower suspension bridge finite element models are erected to analyze the difference between their static and dynamic characteristics.Finite element models of hinge system, floating system, the longitudinal elastic restraint system, the vertical support system and the consolidation system are established. Through comparative analysis of the five systems, the main conclusions are got as follows:if a certain stiffness of longitudinal elastic restraint are set between the middle tower and the girder, it can decrease the bending moment of the column bottom and horizontal displacement of the girder under the action of static and dynamic force, besides, the bending moment of the girder is less than the consolidation system, it should be the recommended system.Finite element models of all elastic link devices, all dampers, center elastic link devices sides dampers, center dampers sides elastic link devices are established. Through parametric analysis on these four systems under the action of static and dynamic forces, some conclusions are got:The horizontal displacement of the girder is too large under the action of static forces in the condition of all dampers, The bending moment of the side tower bottom is too large under the action of dynamic forces in the condition of all elastic link devices, the two binding systems are undesirable, dampers and elastic link devices combination is a better choice.