Study On Gravity Anchorage Structure And Replaceable Main Cable Anchorage System Of Super-long Span Suspension Bridges

The structural function of gravity anchorage is to use its own weight to balance the huge tension transmitted by the main cable of suspension bridge,but the problems of crack resistance,shear resistance and load transmission caused by the cable strands dispersed anchorage are related to the safety and durability of anchor structure.Therefore,it is of great significance to carry out researches on the stress mechanism,structural design of anchorage structure and replaceable of main cable anchorage system.Based on the gravity anchorage of Zhangjinggao Yangtze River Bridge,theoretical analysis and finite element numerical simulation are used to study the anchorage and its anchorage system.The main work and research results are as follows:(1)In the view of gravity anchorage’s structure and mechanical characteristics,using the topology optimization method to solve the anchorage structure’s topology configuration in the twodimensional plane and three-dimensional space with the minimum strain-energy principle,the loadtransfer of anchorage in different stress stages is studied.The force transmission path of the anchor body in different stress stages is studied,combining with the principal stress trace of the structure,and the strut-and-tie models(STMs)is constructed,which provides reference for the reinforcement design of the anchorage structure.(2)A simplified structure design method of gravity anchorage is proposed,and based on the balance criterion of force,the determination method of the dip Angle of the supporting pier of splay saddle is deduced.Using elastic and elastic-plastic finite element models to analyze the effects of geometric design parameters of gravity anchorage(including distance between front and rear anchor surfaces,depth of anchorage zone,diffusion angle of prestressed tendons and inclination angle of main cable center line)on structural stress,deformation and ultimate failure mode,and the corresponding variation rules are obtained.(3)By establishing a three-dimensional finite element model of the southern anchorage of Zhangjinggao Yangtze River Bridge,the stress distribution of the anchorage in the stage of prestressed tension and the stage of main cable tension is analyzed.The results show that: The overall stress level of the anchorage is low,but there is local stress concentration,especially the tensile stress around the anchorage area,around the edge of the anchorage rear chamber and the top of the supporting pier of splay saddle is large.The average shear stress of the four most unfavorable sections of the south anchorage of Zhangjinggao Yangtze River Bridge is calculated according to the relevant specifications,the shear capacity of the two key interfaces of the foundation roof and slurry-wall is checked,the reinforcement design of the supporting pier of splay saddle is carried out by using the STMs method,and the design suggestions of the suspension bridge anchorage are put forward.(4)The durability of main cable anchorage system are analyzed and the necessity of replaceable anchorage system is discussed.On the basis of summarizing the structural characteristics of several existing replaceable prestressed anchorage systems,three new replaceable main cable anchorage systems and schemes are proposed to solve the problems of low replacement efficiency and inability to replace connectors and tie rod components.