Study On Mechanical Properties Of The Thin-walled Girder Bridges Considering Self-equilibrium

Thin-walled girder bridge has the advantages of good mechanical properties and low construction cost.With the development of theoretical analysis,experimental research and numerical simulation,thin-walled girder bridge has been widely used in bridge construction.However,many problems,such as excessive deflection and concrete excessive stress cracks,have been observed in the bridges in service.These problems suggest that further improvement on the material design and theoretical analysis of thin-walled girder bridge is highly demanded.Besides,it also indicates that the current understanding of the internal mechanism of thin-walled structure girder bridge under stress work is not deep enough.The design standard cannot meet the design requirements at the current stage.Therefore,theoretical research on the working mechanism of thin-walled structure girder bridges is highly needed.In the past several decades,research on thin-walled girder bridge paid more attention to the shear lag effect,the finite element method solution,the application of new materials and the structural mechanical performance.The influence of section self-equilibrium condition on the computational mechanical properties are rarely studied.Therefore,this study focused on three major mechanical problems of thin-walled girder bridge,i.e.shear lag effect and cross-section on the balance of thin-walled open structure mechanical characteristics analysis;the detailed mechanical analysis on structure of the thin wall based on its mechanical properties;and the simulation and mechanical analysis on the corrugated steel web curve characteristics analysis.In this paper,the static and dynamic characteristics of thin-walled structure beam bridge were analyzed in detail,and the theoretical analysis,finite element numerical simulation and experimental verification of thin-walled structure beam bridge were carried out.The main research work is as follows:Energy variational principle was used for thin-walled straight girders with T-section.Compared with the traditional calculation methods,static mechanical governing differential equations of single-ribbed and multi-ribbed T-girders,considering the self-balance of shear hysteresis warpage stress,shear deformation,and shear hysteresis effect,were established.Besides,differential equations and natural boundary conditions were derived to obtain the analytical solutions.For the fins of the single-ribbed,double-ribbed,and multi-ribbed T-girders with different spans and width ratios under uniformly distributed and concentrated loads,the variation laws,such as the normal stress,shear lag coefficient,and the contribution of section self-equilibrium condition,were comprehensively analyzed.The contribution rates under the condition of self-equilibrium to the normal stress and vertical displacement were studied.Furthermore,the dynamic governing differential equations and boundary conditions of single-ribbed T-shaped curved girders were established,and the analytical solutions of the dynamic characteristics of single-ribbed T-shaped curved girders were proposed.Compared with the results based on the traditional calculation theory,it was found that the self-equilibrium condition of shear hysteresis warping stress has big effects on the bridge’s natural frequency,the amplitude of dynamic stress,and the coefficient of dynamic shear hysteresis.Finally,the accuracy of the proposed theoretical method was verified by finite element simulations.Shear lag warping stress from the equilibrium condition was introduced based on the energy variational principle for thin-walled trapezoidal section box girder structure.At the same time,considering the factors such as shear deformation and the shear lag effect,the governing differential equations and boundary conditions of thin-walled trapezoidal box girder were established through three different shear lag longitudinal displacement differential functions.Theory analytical solution was derived through a series of deductions,which further improves the thin-wall held section shear lag calculation theory.Through case studies,the effects of factors,such as type of load,span and wing width/thickness,on wing plate stress of trapezoidal box girder,the shear lag coefficient,balance conditions’ contribution,and the vertical deflection trapezoidal box girder were discussed.The results showed that the application of self-balancing condition can significantly improve the calculation accuracy of the positive stress of the box girder wing,especially for the box-girder bridge with small span and low girder and high girder.The influence of self-balancing condition is more prominent when the span width ratio is small.Therefore,this study had great benefits for both theoretical research and practical application.To accurately analyze the vertical bending static characteristics of the composite trough girder with corrugated steel webs,factors such as corrugated steel webs,the shear lag,and shear deformation of the trough girder,were considered.At the same time,the self-equilibrium conditions of shear lag warping stress and bending moment were introduced.Based on the principle of minimum potential energy,the elastic governing differential equations and natural boundary conditions of groove girders were established.An analytical solution for the static characteristic analysis of the composite trough girder was proposed.Compared with the traditional calculation method,the calculation accuracy of the deduced analytical theory is improved.Moreover,compared with the bottom of the groove girder,the effect of the fold on the mechanical properties of the web rib girder is more prominent.Compared with simply support boundary conditions,the folding effect of continuous groove girder is more significant.Under concentrated load or continuous boundary conditions,the shear lag effect of composite trough girder is more significant.A fast ABAQUS parameterization and fine modeling platform subprogram was developed and built for curved continuous box girder with corrugated steel webs,considering the complicated modeling and a large amount of pre-processing work.The bearing capacity of the box girder was studied based on the developed subroutine.The influence of the bending angle of steel webs,the radius of curvature and the height of the girder on the stress of the roof and floor and the influence of different bearing constraints on the internal force of the section and the dynamic characteristics were analyzed.The above theoretical analysis and case studies reveal the mechanical response mechanism and internal law of thin-walled structure girder bridge accounting for section self-balancing condition.Results showed that with the introduction of section self-balancing condition,the calculation accuracy can be significantly improved,which indicated the necessity of introducing this condition.In bridge engineering construction,thin-walled structure bridge,which has a small span,low height,and wide flange,has been widely used.The mechanical properties of the structure are very complex.In order to better understand its mechanical characteristics and working capacity,research on thin-walled structure bridge considering section self-balancing condition is highly desired.Thus,the detailed analysis of the mechanical properties of thin-walled structure bridge has significant engineering and practical benefits.