Analysis of the shear lag effect of cantilever box girder

Abstract

The theoretical method for solving the shear lag effect of cantilever box girder is applicable through exerting the principle of minimum potential energy and combining the variation method, from which the computation expressions of longitudinal displacement function and maximum angle displacement difference function are deduced. The computational formulas of the shear lag coefficient, additional bending moment and deflection are also deduced under condition that the cantilever box girder is acting both on the concentrated force load and uniformly distributed load. The simulated analysis model is built using a finite element method. The analysis indicates that if the external load produces a constant shear flow within the section of the cantilever beam, only the positive shear lag effect will be produced ;but if such load produces a varying or reverse shear flow within the section of the cantilever beam, the negative shear lag effect will be produced. As the magnitude of the shear lag coefficient is proportional to the wide-span ratio, the structural deflection will be increased either by a positive or negative shear lag effect. . The theoretical analysis is consistent with the analysis conclusion of the finite element method.