Shear lag effect on stress concentration in simply-supported stiffened box girder

Abstract

The shear lag effect on stress concentration in a simply-supported stiffened box girder is investigated by three-dimensional finite element analysis. In the analysis, the dependence of the stress concentration on the finite element mesh is circumvented by the multimesh extrapolation method. An extensive parametric study is conducted with respect to the geometry of the stiffened box girder including the cross-sectional area of stiffeners. The influence of the method of load application is also studied. The stress concentration due to the shear lag is sensitive to the way a concentrated load is modeled, while relatively insensitive to the way a uniformly distributed load is modeled. The estimation of the stress concentration by the formula of Eurocode 3 agrees well with the present finite element analysis results for an unstiffened box girder. However, the formula tends to overestimate the influence of the stiffener. Regression analysis is then conducted, taking three approaches. The multiple linear regression equation is the simplest approach and helps identify the degree of the influence of each parameter, yet the accuracy is low, as the mean square error is as large as 16–20%. Though a little more involved, the accuracy of the empirical formula is much higher, with the mean square error about 3%. An artificial intelligence technique, based on the regression model of the multi-layer perceptron, is also examined. The accuracy is the highest of the approaches tested: the mean square error is well below 1%.