Assessment of cracking, creep and shrinkage effects in indeterminate steel-concrete composite flexural members at service load

Abstract

Steel-concrete composite (SCC) flexural member utilization in the construction industry is continuously increasing due to their increased structural stiffness, lower self-weight, and faster construction compared to conventional members. The most commonly utilized SCC flexural members consist of an integrated concrete slab and steel beam through shear connectors. Continuous SCC flexural members are preferred over simply-supported SCC members due to their higher span-to-depth ratio as a result of moment redistribution at the supports. However, the continuous members are subjected to hogging moments near the interior supports leading to cracking in the concrete slab which may cause an increment in the deflection of the SCC member. Further, there is more change in the deflection due to the creep and shrinkage effects on the members. The majority of available numerical methods require exorbitantly high computational time due to discretization across the cross-section and along the span length of the members. Hence, in the present study, a novel methodology i.e. analytical at the cross-sectional stage and numerical at the structural stage is proposed that requires no discretization and lesser computational time. The expressions are derived in the proposed methodology for service load analysis of indeterminate SCC flexural members incorporating the instantaneous effects of concrete cracking and its progression due to the time-dependent effects of creep and shrinkage. The proposed methodology exhibits higher accuracy than existing analytical-numerical procedure due to the inclusion of time-dependent effects in cracked SCC cross-sections. Moreover, it is applicable for various types of loading and requires lesser computational time than FE methods that require discretization along and across the SCC members. From the existing experimental studies, two samples of two-span continuous beams B1 and B2 having identical dimensions are considered for the validation study. Beam B1 is subjected to self-weight and imposed loading while beam B2 is subjected to only self-weight loading. The results from the proposed methodology, when validated against the available experimental studies, show a good agreement with a marginal error, suitable for design applications. The proposed methodology shows an improvement in the results by 3.64 % and 4.55 % for beams B1 and B2 at 340 days, respectively, compared to existing computational efficient procedure when validated with available experimental results. © 2024 Institution of Structural Engineers