Research On Key Technologies Of Single-Tower Long-Span Self-Anchored Suspension Bridge Boom Tension And Linear Control

The main cable of the self-anchored suspension bridge is anchored directly to the stiffener beam,eliminating the need to build huge concrete anchor ingots,and the structural alignment looks softer and lighter.Self-anchored suspension bridges are more adaptable and can be adapted to various terrain and geological conditions have attracted much attention from the engineering community in recent years,and are very competitive in the construction of urban large and medium-span bridges.However,the self-anchored structure is complex and difficult to construct,especially since the nonlinearity of the structure in the process of boom tension is significant,the structural response law is particularly complex,and multiple simulation calculations must be carried out to formulate a reasonable sling tension scheme.Relying on the 2×350m single-tower selfanchored suspension bridge project of the second ring road of Jibei Ring Expressway,this paper studies the key technologies of sling tension control and construction of selfanchored suspension bridges,and the main research contents are as follows:(1)because of the construction sequence of the first girder and then the cable of the self-anchored suspension bridge,combined with the actual geological conditions of the bridge,the erection technology of the jacking method combined with the bracket assembled steel box girder used for the main girder was studied.The jacking model is established,and the forces of the jacking platform,temporary pier,guide beam and steel box girder during the jacking process are calculated.The local stress analysis of the ejection beam section was carried out by Midas FEA,which ensured the safety of the jacking process.(2)Taking the knot-line method as the theoretical basis,the finite element model of the bridge state was established by using Midas Civil,and the accurate equilibrium state consistent with the design was obtained;The empty cable shape,sling and stress-free length of the main cable were obtained by flip analysis.Taking the reference cable strand frame as an example,a control method for the cable strand line shape is proposed.(3)Combined with the supporting project,the conversion of a self-anchored suspension bridge system based on sling tension was studied.Using Midas Civil to simulate three different tension sequences of slings,by setting the tension sequence comparison parameters,the three sling tension sequences are compared and analyzed,and finally,the optimal tension sequence from the anchor end to the direction of the main tower is determined,and on this basis,the tension scheme is formulated,that is,first tension 1# sling(cable force does not exceed allowably),then cycle tension 2#,3# and1# slings in turn,and after the completion of 1# cable tension,recycle tension 4#,3# and2# slings.And so on until the tension is complete.The solution to the problem of sling force overrun during simulated sling tension is given,and the nonlinear large displacement,strong coherence of the sling and the linear shape of the steel box girder during the tension process are discussed.(4)Based on formal installation-inverted disassembly,the setting method of pre-arch of the stiffener beam of the self-anchored suspension bridge is given.By simulating different beam weight deviations(-5%,-3%,-1%,1%,3%,5%),the influence of beam weight deviation on the linear shape of the main beam,the shape of the main cable and the sling force was studied,and it was concluded that the beam weight deviation had a greater impact on the linear shape of the main beam and had little effect on the sling force and the shape of the main cable,and it was proposed that the beam weight deviation should be controlled within 3% during processing.(5)Based on the influence matrix method,the method of adjusting the linear shape of the main beam of the self-anchored suspension bridge by adjusting the sling force was studied,and combined with the supporting project,the linear deviation of the main beam caused by the beam weight deviation of 3% was taken as an example,and the linear deviation of the main beam was adjusted,and the adjusted main beam linear shape reached the ideal target value,which can be considered as a success,which provides ideas and methods for solving problems related to the same type of bridge in the later stage.Based on the actual engineering project,this paper uses Midas Civil to establish a finite element model of a single-tower self-anchored suspension bridge,simulates and analyzes the whole process from the erection of the main girder to the sling tension to the final bridge state,puts forward a reasonable sling tension scheme and studies the key technologies of construction control,which provides guidance for the construction of the bridge and provides a reference for the research of similar bridges in the later stage.