悬索桥新型复合索鞍设计

虎跳峡金沙江大桥为主跨766 m的独塔地锚式悬索桥。由于取消了香格里拉岸的桥塔,中跨主缆仅通过索鞍支承、转向及散索后锚于锚碇,该索鞍不仅需具备主索鞍的支承功能,还需具备散索和纵向活动功能,其功能及受力要求均较高。结合该桥建设条件,提出一种主要由鞍体、辊子组、承板、格栅等构成的新型复合索鞍,其中,鞍体承担支索、转索和散索的作用;辊子组连接于鞍体与支墩之间,当中跨主缆缆力发生变化时,辊子发生滚动;承板布置在辊子组的顶面和底面,与辊子组接触;格栅预埋在支墩顶面,将索鞍传递的竖向荷载均匀分布到混凝土中。经有限元和试验验证,新型复合索鞍鞍体最大等效应力为151.8 MPa,辊子与承板之间的最大接触应力为578 MPa,受力满足设计要求。

Design of a New Type of Composite Saddle for Suspension Bridge

The main bridge of Jinshajiang River Bridge over the Tiger Leaping Gorge is a single-tower,earth-anchored suspension bridge with a main span of 766 m.In the preliminary design,there was also a tower on the Shangri-La side,but after schemes comparison,this Shangri-La side tower was dismissed.For the selected single-tower suspension bridge,the main cables of intermediate span could only be supported and steered by saddles,and splayed to be anchored to the anchorages,which proposed high demands for the function and load bearing capacity of the main cable saddles.Besides the basic supporting ability,the saddles should be able to splay the main cable strands and move in the longitudinal direction.To suit the construction condition of the bridge,a new-type composite saddle that consists of the main components of saddle body,rollers,bearing plates and grille was proposed.The saddle body can support,steer and splay the main cable.The rollers connect the saddle body and the supports,when the main cable forces in the intermediate span begin to change,the rollers will move.The bearing plates are installed both on and beneath the rollers and contact with the rollers.The grille is embedded in the head of the support,which can evenly transfer the vertical loads from the saddle to the concrete.Verified by finite element analysis and tests,the maximum stress in the body of the new-type composite saddle is 151.8 MPa,the maximum contact stress between the rollers and bearing plates is 578 MPa,proving that the load bearing performance of the saddle can meet the design requirements.