Theoretical And Experimental Study On The Mechanical Properties Of Curved Composite Box Girders With Corrugated Steel Webs

Two main research contents are studied in this thesis.First,the flexural,torsional and distortional performance of curved box girders(CBGs)with corrugated steel webs(CSWs).Second,the shear buckling and shear strength of CSWs in CBGs.Considering the mechanical characteristic of CSWs,and adopting the theoretical analysis,finite element analysis and model test,the above contents are studied.The main research work and results are as follows:(1)Based on the equilibrium equations of curved girders,the relationships between internal forces and displacements,the flexure-torsion differential equations considering the shear deformation and the structural feature of CSWs are derived for CBGs with CSWs.Using the energy-variation method,the distortion differential equation considering the structural feature of CSWs is derived for CBGs with CSWs.Adopting trigonometric series as the displacement functions,and using the Galerkin method to solve the flexure-torsion differential equations and the distortion differential equation,a practical method which can so lve the displacements,stresses and internal forces of simple and continuous CBGs with intermediate diaphragms and without intermediate diaphragms is proposed.The elastic model tests under various load conditions of 3 CBGs with CSWs are carried out to verify the correctness of the analytical method in solving deflections,torsional angles,normal stresses and shear stresses.(2)The influence of shear deformations of CSWs on the deflections of CBGs with CSWs,and comparisons of mechanical properties of CBGs with CSWs to concrete CBGs are studied theoretically.The results show that the deflections caused by shear deformations of CSWs are large and cannot be ignored.Under external load,the deflections,torsional angles,distortional angles,flexural normal stresses,restrained torsional warping normal stresses and distortional warping normal stresses of CBGs with CSWs are all greater than those of concrete CBGs.The warping normal stresses and the additional shear stresses caused by the restrained torsion and distortion are large and cannot be ignored.(3)The corrugated steel web in horizontally curved girders is treated as an orthotropic cylindrical shallow shell.According to the stability theory of plates and shells,and adopting double trigonometric series as the displacement functions,the analytical formula for the elastic global shear buckling stress is deduced by the Galerkin method.Calculation tables for the global shear buckling coefficient for a four-edge simple support,for a four-edge fixed support,and for the two edges constrained by flanges fixed and the other two edges simply supported are given.(4)The interactive shear buckling of CSWs is treated as the buckling of a folded plate structure composed of two adjacent plates.According to the stability theory of plates and shells,and adopting double trigonometric series as the displacement functions,the analytical formula for the elastic interactive shear buckling stress for a four-edge simple support is deduced by the Galerkin method.Calculation table for the interactive shear buckling coefficient of CSWs when the flat panel width equal to the inclined panel width is given.(5)The shear buckling slenderness ratio λ_s in the Japanese Design Manual for PC bridges with CSWs is revised by adopting the global and interactive shear buckling stresses formulas proposed in this paper,and the suggested formula of the shear buckling slenderness ratio λ_s is given.The results of 102 model tests in the literature are used to verify the correctness of the suggested formula.(6)The destructive model tests of 3 CBGs with CSWs under outer eccentric loading are carried out to study the whole loading process and failure modes of CBGs with CSWs.The whole load-deflection curve,the distribution pattern of concrete crack,the failure mode of CSWs,the variation law of principal tensile strain in concrete slabs,the variation law of shear strain in CSWs,and the variation law of axial strain in steel bars are obtained in the model tests.The research work can provide references and design suggestions for the design and construction of CBGs with CSWs.