Research On Key Technology Of The Three Tower Self-anchored Combination System Bridge Of Cable-stayed And Suspension Construction Control

As a new and unique type of bridge, the three tower self-anchored suspension andcable-stayed combination system bridge combines characteristics of the both withdistinctive styling, smooth linear and artistic structure. However, combined force ofmain cable also leads to difficulties in structural design, computational analysis andstructure system transformation. At present, scholars at home and abroad are mainlyfocus on research of cooperative system bridge (suspension cable and stayed cableexist in the same span), but rarely on combination system bridge (suspension cable andstayed cable exist out of the same span), and even without any researches on thetechnical problems of reasonable finished status and reasonable construction status inconstruction control of the three tower self-anchored suspension and cable-stayedcombination system bridge. In this paper, some technical issues, such as the realizationof linear design, security during system transformation and optimization of majorconstruction progress, etc are researched on the basis of the construction controlproject—Long Gang Bridge in Hanzhong, Shanxi Province. The main research resultsare as below:(1) A comprehensive optimization algorithm method, which combining cableanalytic program and finite element program MIDAS/Civil, is put forward to determinereasonable finished status of the combination of three tower self-anchored suspensionand cable-stayed system bridge. With this method, final reasonable status can beachieved by choosing reasonable objective function, design variable and state variableto reflect design idea, considering compression of tower and beam, utilizing structuraloptimization method to obtain fundamental finished status, and taking stress balancemethod to adjust and arrange beam tendons and checking the fundamental finishedstatus.(2) In respect of Long Gang Bridge’s mechanical characteristic, the generalprinciple while tensioning suspension rope in self-anchored suspension segments israised. Through computational optimization, the tensioning plan which can avoidrepeated tension and suspension rope bending in the position of sleeves is given withcorresponded responses during the construction process under the plan.(3) In the light of some shortages in the former design, which are the tower andbeam provisional constraints force being too large to ensure the bridge construction safety when removing the constraints in self-anchored suspension segments and thefull framing being vulnerable in flood season in the construction process, in this paper,optimal closure plan is given to avoid provisional constraints setting and allow partialbrackets being removed in advance to reduce risks of brackets collapsing under flood.