Matrix Analysis on Flexural Behavior of Thin-walled Box Girder

On the basis of the shape function matrix which is established through assuming the homogeneous solution to the governing differential equation for shear lag of the thin-walled box girder as the element displacement function,the formula of the equivalent nodal force of the element under vertical concentrated loads is derived by applying the principle of virtual work.The reasonable warping displacement function of shear lag is proposed for the box girder with the twin-cell cross-section.The plexiglass model of the cantilever box girder with variable cross-sections is calculated,thus validating the effectiveness of the finite segment element in analysis of the box girder with variable cross-sections.The flexural behavior of the prestressed concrete continuous box girder with variable cross-sections is analyzed through a practical example.The results show as follows: The finite segment element has high computing efficiency for the box girder with variable cross-sections;under the action of vertical concentrated loads,the shear lag moment diagram of the box girder is a smooth curve and the absolute value of the shear lag moment is not greater than that of the bending moment at any cross-sections;the shear lag effect increases the mid-span deflection of the continuous box girder significantly,which shall be treated seriously in engineering practice.