Enhanced Design Approach for Determining Effective Slab Width in Box Girder Composite Sections

The effective slab width of concrete slabs in Box Girder Composite Sections (BGCSs) has been shown to vary significantly across different loading stages, such as serviceability and ultimate limit states. However, current international design codes do not account for these variations, potentially leading to inaccurate assessments in structural applications. To better understand the behavior of box girders, a nonlinear finite element model of BGCSs was developed using ABAQUS 6.14 [1] and validated against data from three independent experimental research programs. The model successfully predicted the behavior of BGCSs, providing reliable predictions of effective slab width. A comprehensive numerical parametric study was conducted on 216 girders to investigate effective slab widths at the serviceability limit states, considering a range of geometric parameters, including steel girder dimensions and slab thickness. The approach proposed by Lasheen et al. (2018) [2] for determining the effective slab width in doubly symmetric composite steel sections was adopted and enhanced to be applicable for determining the effective slab width in BGCSs at service limit states. The findings of the second phase demonstrated that the effective slab width is influenced by three factors: the slenderness ratio of the steel box section (L/rs), the ratio of the slab thickness to the slab width (ts/Bs), and the ratio of the slab width to the girder span (Bs/L). Consequently, a newly developed design equation is proposed in the current research to accurately calculate the effective slab widths at service limit states.