Varying analysis considering shear lag effects of variable cross-section PC cantilever box girder
|School||Central South University|
|Keywords||Prestressed concrete box girder Variable cross-section Shear Lag Creep Reinforced constraint Finite Difference Method|
Uniform thin wall box in the form of long-span prestressed concrete beam bridge cantilever construction method is commonly used during the construction of box girder in the cantilever state more accurately predict cantilever box girder deformation and the stress control during the construction of linear and bridge after box Beam Alignment important basis to meet the design requirements. Prestressed concrete box girder concrete creep caused by beam deformation changes over time, will add additional deformation of the beam shear lag, therefore, consider shear lag affect the time-varying effect analysis has important engineering significance . Departure from the principle of energy and internal force equilibrium conditions, Prestressed concrete cantilever box girder considering shear lag, the rate of reinforcement, prestressing tendons stress relaxation creep effect for the in-depth study of the bridge cantilever construction method Guo the Chengzhong Liang body linear and concrete reinforced stress changes over time to provide ideas, with theoretical significance and value of the works. First, the use of energy variational method, derived considering reinforced impact shear lag control differential equations using finite difference method to get a variable cross-section cantilever box girder under dead load and pre-afterburner role stress, deflection and shear lag coefficient calculated expression . By the introduction of the time-varying concrete constitutive equation, any time sectional internal force balance equation and deformation compatibility conditions, combined with the shear lag calculations assume considering shear lag, concrete shrinkage and creep, stress relaxation of prestressing tendons with prestressed concrete tendons rate becomes variable cross-section cantilever box girder effect analysis methods, the establishment of a semi-analytical calculation of expression based on the finite difference method; based on the characteristics of analog cantilever construction method derive a set of time-varying effects can be applied to tracking the construction process of the cantilever method becomes Cantilever Box Girder formula. Finally, using the Matlab language programming of this method and formulas cantilever construction method Dongjiang Bridge during construction beam deformation and concrete stress, shear lag coefficient calculation and analysis, and the calculated results without considering shear lag effects of limited element software calculated the comparison shows that the established method varying effect of prestressed concrete cantilever box girder considering shear lag effects of variable cross-section formula can be derived considering shear lag, concrete creep and shrinkage, Deformation of prestressed tendons stress relaxation, reinforcement ratio of beam, concrete time-varying stress calculation.