Study On Construction Monitoring Of Three-Tower Four-Span Self-Anchored Suspension Bridge

The Three-Tower Self-Anchored Suspension Bridge is a special type of suspension bridge.Compared with traditional ground anchor suspension bridges,it does not require the construction of large-volume anchorages.Its main cable is directly anchored to the main beam,which also requires lower geological conditions and has stronger competitiveness.Compared with ordinary two-tower self-anchored suspension bridges,the three-tower self-anchored suspension bridge has an additional bridge tower in the center of the bridge,which has stronger span,stability,and bearing capacity.However,there are currently few multi-tower self-anchored suspension bridges built domestically and internationally,and research on them is not sufficient.Therefore,it is necessary to conduct research on it.This thesis takes a three-tower,four-span self-anchored suspension bridge as the engineering background to study the calculation method of the cable system,finite element simulation method,design principles and control factors of hanger tension,system conversion effect,concrete shrinkage and creep effect,parameter sensitivity,and main cable line shape calculation based on BP neural network.The main research contents are as follows:(1)The calculation method and process of the three-tower self-anchored suspension bridge cable system were studied,and the calculation theory of the bridge-forming main cable and the calculation method of the empty cable shape were analyzed.Based on the geometric model of the position of the saddle of the suspension bridge and the intersection of the main cable unit,the stress-free length correction formula of each cable strand at the intersection of the main cable saddle and the main cable element is derived,and the calculation method of the stress-free length of the sling is studied.(2)Based on Midas/civil,the finite element simulation method of the three-tower self-anchored suspension bridge is studied,mainly including the simulation of the bridge completion state,main cable saddle pushing simulation,and hanger tension simulation.The design principles and control factors of the hanger tension scheme for the three-tower self-anchored suspension bridge are analyzed and summarized,and a hanger tension scheme design method based on the "simplify first and refine later" method is proposed.This method is applied to design two feasible hanger tension schemes for the background engineering.(3)Comparing the structural response of the three-tower self-anchored suspension bridge in the system conversion process,it is found that the variation law of the hanger force during tensioning conforms to "strong coherence," and the main cable line shape change conforms to "weak coherence."(4)The shrinkage creep effect of three-tower four-span self-anchored suspension bridge was analyzed and studied,and it was found that the effect of shrinkage creep effect increased with the extension of the termination time of shrinkage creep calculation,and the change rate was faster in the early stage and slower in the later stage.After pouring,the influence of shrinkage creep effect of concrete on the bridge structure decreases with the delay of loading age.According to the influence of concrete shrinkage creep on the three-tower self-anchored suspension bridge,effective control measures are proposed.(5)The parameter sensitivity of the three-tower four-span self-anchor suspension bridge was analyzed,the sensitivity of different parameters was obtained,and the parameters that were sensitive to the change of the main cable shape were selected to establish the main cable BP neural network prediction model,and the model was tested.