Study On Temporary Consolidation Measures For Tower Girder Of Steel-concrete Composite Beam Cable-stayed Bridge

The steel-concrete composite beam cable-stayed bridge has the advantages of light weight,large span capacity,easy factory production and quick assembly.The main beam of cable-stayed bridge is usually constructed by cantilever.For floating or semi-floating cable-stayed bridge,the main beam should be temporarily anchored during construction.Because the cantilever construction of the superstructure system will cause unbalanced load on both sides of the main tower,and the main beam under the action of unbalanced load,the main beam structure may have longitudinal or lateral drift,instability,or even overturn,resulting in serious safety problems.Therefore,some measures must be taken to temporarily consolidate the main beam and the main tower column,so as to resist the unbalanced load.But the bridge design and construction code does not have the explicit stipulation about the tower beam temporary consolidation;the existing related papers,the literature is limited,only a few papers are all about the separation type tower beam consolidation system,the integral type tower beam consolidation system research is not involved in the research domain now,therefore the steel-concrete composite beam cablestayed bridge tower beam temporary consolidation is worth the research topic.Based on the second bridge of Poyang Lake(steel-concrete composite beam cablestayed bridge)stayed bridge),the stress course of the temporary consolidation of the tower beam is determined simulation analysis of the whole construction process.By using the finite element software MIDAS FEA the stress distribution stress distribution of concrete column and steel bar,and then the parameter sensitivity analysis is made,and reasonable optimization measures are put forward.The main research contents and related conclusions are as follows:(1)Based on the engineering background of Poyang Lake steel-concrete composite beam cable-stayed bridge,the stress course of temporary consolidation of tower beam in the whole construction process is analyzed by using finite element software MIDAS CIVIL simulation,and the most unfavorable stress condition of temporary consolidation is determined,that is,one stage of cable 11.Combined with the actual situation in the field,the phenomenon of reaction force mutation in the whole construction process of temporary consolidation of tower beam is analyzed.(2)The influence of different simulation methods and constraint stiffness on the internal force and displacement of the main beam,the reaction force of temporary consolidation of the tower beam and the cable force are discussed.The rotating stiffness of temporary consolidation of tower and beam,the stiffness of cable tower and lower beam are the sensitive factors affecting the stress and deformation of the structure.(3)Finite element software MIDAS FEA is used to study the stress distribution of concrete columns and finished steel bars.It is found that the normal tensile stress of the temporary consolidated concrete column of the original design tower beam exceeds the limit value of the normal tensile stress of the concrete in the construction stage;the outer three pairs of short finished rolled rebar do not play the performance of the prestressed steel bundle;the temporary consolidation and demolition of the tower beam after the middle span closure is time-consuming and laborious.(4)According to the stress distribution law of concrete column and finished steel bar,the design parameters of temporary consolidation of tower beam are studied,and reasonable measures are put forward to improve the consolidation force of tower beam.It is found that weakening the lower beam,tensioning and finishing rebar,changing the tensile strength of finishing rebar,changing the diameter and spacing of finishing rebar,adding prestressed steel bundle and finishing rebar can improve the consolidation force of tower beam.