Research On Cable Force Optimization Of The High And Low Tower Horizontal Rotary Cable-stayed Bridge During Construction

High and low tower cable-stayed bridge has novel shape and beautiful form.When crossing the existing railway and highway,the construction can be carried out by the horizontal rotation method,so that a reasonable and economical bridge span layout can be obtained under the same span.It has become one of the competitive bridge types in plain areas of China.Taking baoding city high and low tower cable-stayed bridge as the engineering background and the cable force optimization in the construction process of cable-stayed bridge with large tonnage,long cantilever and asymmetry is studied.And the structural stress,deformation and cable force optimization of the tensioning cable on the support are analyzed.The main research contents and conclusions of this paper are as follows:(1)This paper summarizes the development and research status of high and low tower cable-stayed bridge,the horizontal rotation method and cable force optimization at home and abroad.In view of the particularity of the support-horizontal rotation combined construction process and the stress state of the high and low tower cable-stayed bridge,the cable force optimization of the bridge stage and construction process needs to be further studied.(2)Through the study of the difference and similarity between the support-horizontal rotation combined construction method and the cantilever laying method,the internal force formula of the beam is derived and the uncertainty of the effective stress and the uncertainty of the time when the beam is taken off is put forward.Then,according to the expected state of the structure,the stress control target of the structure in the main construction stage is established.Finally,according to the characteristics of the construction method,the idea of cable force optimization based on the orderly-erecting analysis method and the principle of cable force optimization in corresponding stage are put forward.(3)In view of high and low tower concrete cable-stayed bridge has its particularity when the beam is cast-in-place and the cable is tensioned on the full bracket.The formula for calculating the effective stress of beam with friction resistance is derived.The influence rules of the stress,cable force and deflection of the beam are studied,such as the friction resistance of the bracket template,different falling orders,the temperature difference between the cable and the beam,the vertical temperature gradient of the beam and the hydration heat effect of cast-in-place concrete of the beam.It is found that the first four factors have a certain influence on the structural stress and deflection of the beam in the initial tension and falling stage.In addition,the coupling effect of the above factors should be considered in cable force optimization.(4)The optimization method of the rational completion state and the determination method of the rational horizontal rotation state of the high and low tower concrete cablestayed bridge are put forward.Then,in the case of beam element analysis "distortion",the stress state of the beam in the tower beam consolidation area is analyzed by using solid element,in order to reduce the shortage of the experience method of judgment.Finally,the cable force optimization of cable-stayed Bridges in the initial tensile stage on bracket is studied when the coupling effect of influencing factors is considered.(5)The multi-objective cable force optimization method for cable-stayed bridge second cable adjustment stage is proposed.Through the rational use of mathematical model and fgoalattain multi-objective optimization function,the goal of "minimum error with the target value and minimum number of tunings" can be satisfied.Finally,the cable force optimization of cable-stayed bridge in the second stage is studied.