Shear Lag Effect on Box Steel Beams with Wide Curved Flanges

For wide flange box sections, conventional Euler–Bernoulli beam theory with maintaining the cross-section planarity may lead to underestimation of axial stresses. Axial stresses in cross-section flanges may have a non-uniform distribution due to shear pliability, decreasing in value from the flange–web junction to the middle area of the flange. This phenomenon leads to the introduction of an effective flange width with a uniform distribution of original maximum stress. Furthermore, the introduction of flange curvature makes it even more complex due to the varying lever arm of each flange part with respect to the neutral bending axis. Because of this, in some cases, it is hard to predict where the flange’s highest normal stress value will appear. In this paper, the shear lag effect on wide curved box sections is analyzed through parametric numerical analysis using the FEA software Dlubal RFEM 5, together with visual programming performed in Rhino Grasshopper. This study investigates the interaction of the shear lag effect and plane section hypothesis, which can be simplistically represented as a reduction in the impact of shear lag and the activation of a larger part of the flange of a wide-flange beam in the structural system of a continuous beam. The results suggest that for higher flange curvature and higher width to length ratio, this effect is more prominent.