Research On Multi-strand Finished Cable Prestressed Anchorage System For Long-span Suspension Bridges

Anchorage system is the key structure of long-span suspension bridge.Because of the tedious maintenance and replacement process,the traditional prestressed anchorage system is difficult to reduce the maintenance cost and traffic impact.Therefore,this paper introduces a multi-strand finished cable prestressed anchorage system,which uses the finished cable with a variety of anti-corrosion coating as the key bearing structure,which not only improves the replaceability and durability,but also does not need to interrupt the traffic flow and reduce the maintenance cost.In order to promote the application of multi strand finished cable prestressed anchorage system in China,based on the structural characteristics of the anchorage system,this paper proposes a systematic design process including the design and operation stages,and studies the reliability and health monitoring scheme during the normal operation and cable replacement construction of the anchorage system.The main research contents and conclusions of this paper are as follows(1)Firstly,the theory of cable replacement of prestressed anchorage system of suspension bridge is introduced.Based on this,several existing replaceable prestressed anchorage systems are introduced,and their replaceable performance is systematically evaluated.The results show that the prestressed anchorage system with multi strand finished cable has the characteristics of high efficiency of cable replacement,strong anti-corrosion performance,simple construction operation and no interference with the existing traffic,which makes it have obvious advantages in application and promotion(2)Based on the characteristics of the anchorage system,a systematic design process including design and operation stage is proposed.Taking the Nizhou Waterway Bridge as the engineering background,the main cable strand force of the anchorage span is identified and the prestressed design that meets the normal operation of the anchorage system and the safety of the cable replacement construction is carried out.The results show that when the prestress of the cable body is tensioned by σk=0.6fpk,the effective prestress of the cable body can meet the safety requirements of the safety requirements of the single cable extraction and replacement under the condition that no more than one cable body fails to work(3)The tension and replacement test research of the multi-strand finished cable prestressed anchorage system was carried out.The results show that the anchorage system is safe and reliable in the process of stringing,tensioning and replacement.At the same time,the effect of the cable force between the cables is minimal.The performance test study of the force-transmitting members under the anchor is carried out.The results show that the maximum value of the concrete crack width under the anchor is 0.08mm when the anchorage system is working normally,which is less than the crack width limit of 0.25mm under this condition.The maximum stress of the reinforcement under the anchor is 80MPa,which is far less than the material yield strength of 335MPa.All the components under the anchor meet the structural safety requirements(4)Based on the test results of tension and replacement,the cable replacement conditions for the actual engineering application of the multi-strand finished cable prestressed anchoring system were determined,and the numerical simulation analysis of the cable replacement construction process was performed.The results show that the structural performance of the connector and the anchor force-transmitting member under each cable change condition meets the structural safety index,which effectively guarantees the normal operation of the prestressed anchor anchor system with multiple finished cables and the safety of the cable replacement process(5)Based on the above research,the early warning threshold value analysis of the replacement of the multi-strand finished cable prestressed anchorage system are carried out The results show that during the operation of the bridge,when the cable force loss of a single finished cable that meets the design requirements is satisfied,the range of cable force for single-anchor cable replacement of western anchorage is 1842.78kN<F’≤2243.4kN,and the range of cable force for double-cable cable replacement is 3537.9kN<F’≤4205.4kN;the range of cable force for the single-strand anchor of the east anchor is 1976.32kN<F’≤2243.4kN,and the range of cable force for the double-strand anchor is 3804.94kN<F’≤3938.44kN.