Dynamic Finite Segment Method For Thin-Walled Box Girder Considered The Shear Lag Effect

Based on the thin-walled bar theory and finite element method,a finite segment approach in structural dynamic analysis of the thin-walled box girder considered the shear lag effect is presented.combining the principle of energy functional variational principle,a set of dynamic analysis theory and calculation method suitable for shear lag effect of thin-walled box girder are established,and the variation law of shear lag effect in dynamic problem is discussed.This method enriching and developing the theories of the dynamic system,and laying a foundation for the study of the shear lag of thin-walled box girders in dynamic analysis.The major achievements of this paper are as follows:1.Based on the finite element method,The homogeneous solutions derived from the differential equations is used as the displacement patterns of finite segment,the shape function of general beam theory in finite segment is derived.The Natural vibration equation of general beam is established and compared with the analytical solutions.the rate of convergence and two methods of boundary constraints are discussed.This method has satisfactory convergence,accuracy and could easily get the natural frequencies and mode shapes of complex structure.2.Based on the Hamilton energy principle,the finite segment method in structural dynamic analysis of the thin-walled box girder considered the shear lag effect is proposed.The homogeneous solution of shear differential equation is taken as the displacement model of finite segment,The free vibration equation of thin-walled box girder is deduced.The stiffness matrix and mass matrix considering the shear lag effect are obtained.The natural frequency of the box girder is transformed into a generalized eigenvalue problem by matrix combination,and the natural frequency and the corresponding modes are obtained.3.Based on the finite segment method and the energy principle,the forced vibration equilibrium equation of the thin-walled box girder considering the shear lag effect is established.After the discrete dynamic load matrix is obtained.The thin-walled box girder time course changes which considered the shear lag effect of displacement,stress and shear lag coefficient is sovled.The method can be easily incorporated into the thin-walled barprocedure systems,which is suitable for the variable shear lag response analysis of complex structures such as variable cross-section box girder,continuous box girder and cantilever beam.4.Based on the technique of finite element,the element of Beam and shell are used to build the model of the thin-walled box girder model upon the Ansys fem general software.The dynamic response and dynamic characteristics are calculated.The method is verified by comparing with the Ansys results.5.the stress characteristics and structural characteristics of thin-walled box girder is Combined.The parameters affecting shear lag effect are analyzed,and the influence of shear lag effect on dynamic characteristics and dynamic response is studied.Get some meaningful conclusions for engineering design reference.