Analytical Approach for Predicting Deflection in Composite Deck Slabs Subjected to Service Load

Abstract

Steel-concrete composite (SCC) deck slabs have been utilized significantly in building and bridge structures due to their economy, ease, and speed of construction. SCC deck slabs are slender due to a high span-to-depth ratio and hence are susceptible to serviceability criteria like deflection and cracking. Various methods are available in the existing literature for the prediction of deflection in SCC flexural members. However, these methods are based on computing the effective moment of inertia of the span without considering the cracked zone length. Therefore, in this paper, a novel analytical approach is proposed to derive a simplified equation for the prediction of deflection by idealizing cracked and uncracked zones within the span. The derived equations take into account the length of the cracked zone along with the cracking and tension-stiffening effect of the concrete slab. The cracked zone length is determined using the smeared crack approach in the span where the tensile stresses exceed the tensile strength of concrete. The results obtained from the equations are compared with the experimental results available in the literature. Further, the results are compared with available existing codal provisions considering concrete cracking in SCC members. The error in the predicted deflections obtained using the proposed approach and existing codal provisions with respect to experimental results is obtained by evaluating root-mean-square error (RMSE) values for the theoretical actual bending moment (Mact) equal to 1.5 and 2 times the cracking moment (Mcr). The proposed approach predicts deflections, having RMSE values of 0.87 and 1.39 mm with respect to experimental results for Mact=1.5Mcr and Mact=2Mcr, respectively. These RMSE values are significantly lower than those predicted by existing codal provisions (1.97 and 1.99 mm, and 4.19 and 3.63 mm). The comparison demonstrates improved accuracy of the proposed approach in predicting deflections. The proposed approach exhibits an improvement in the predicted deflection compared to existing codal provisions due to the idealization of a span consisting of cracked and uncracked zones. The proposed approach requires less computational effort because it eliminates the need for discretization both across and along the SCC member. © 2025 Elsevier B.V., All rights reserved.