Mechanical Analysis Method Of Box Girder Structure—nodal Method

Bridge is an important hub of traffic system,and it is also an important infrastructure of national economic development.In order to meet the needs of urban and road traffic,a large number of elevated box-girder bridges with variable wall thickness and wide flange have been built in China.The cross section geometry of variable flange thickness and wide flange box girder is complicated,which brings the following difficult problems to the theory and method of traditional box girder structural mechanics analysis:(1)The restrained torsion calculation problem of the single box multi chamber complex section short and stocky box girder with variable wall thickness and wide flange.(2)The shear analysis calculation problem of the single box multi chamber complex section short and stocky box girder with a variable wall thickness and a wide flange in the direction of the transverse asymmetric axis.(3)The analysis calculation problem of the shear,bending and torsion coupling dynamic characteristics of the single box multi chamber short and stocky box girder with a variable wall thickness and a wide flange.(4)The shear lag calculation problem of the single box multi chamber complex section box girder with variable wall thickness and wide flange.Therefore,in order to meet these four difficult problems,this paper will study the analytical methods applicable to the analysis of various cross-section box girders(Including the single box multi chamber complex section box girder with variable wall thickness and wide flange).The main contents are as follows:1.The problem of the restrained torsion of the short and stocky box girder with variable wall thickness and wide flange with different thickness and different chamber is studied by using this method.That is,the displacement of the minimum torsional stiffness center of the cross section and torsion angle of the cross section,normal stress and shear stress distribution,and the warping of cross section are studied when the short and stocky box girder is under restrained torsion.And a new method to determine the torsional center of the short and stocky box girder is proposed.2.The transverse shear problem of the short and stocky box girder with variable wall thickness and wide flange with different thickness and different chamber is studied by using this method.That is,the calculation of shear stress in transverse non-symmetric axis and the distribution of shear stress in the cross section of the short and stocky box girder with aspect ratio less than 3 are studied.3.The free vibration of the short and stocky box girder with variable thickness and wide flange with different thickness and different box chambers is analyzed by this method.That is,the bending vibration,shear-torsional vibration of short beam and coupled vibration of bending and torsion are studied.4.The problem of shear lag of box girder with complicated cross section is discussed in depth,especially the difficult problem of normal stress and shear lag under eccentric load.The results show that the mechanical analysis method of box girder structural-Nodal method,can deal with the above 4 difficult problems brought by the complex cross section box girder to the structural mechanics analysis theory of the traditional box girder,and that has important theoretical significance and engineering application value.