Design Procedures for Predicting Long-Term Responses of Continuous Steel-Concrete Composite Slabs

Although the effect of nonuniform shrinkage on the time-dependent behavior of simply supported composite slabs has been extensively investigated, continuous composite slabs have not garnered enough attention. This paper aims to propose the routine design procedures for continuous composite slabs, including the hogging moment over the interior support and the mid-span deflection. Thus, the long-term test data on two-span continuous composite slabs provided by the authors and the related literature were collected to benchmark the current design methods in international specifications. The routine design procedures for calculating the long-term moment distribution and the mid-span deflection of two-span composite slabs were proposed considering the time-dependent range of hogging moment zones. Moreover, the effects of different shrinkage distributions and hogging moment ranges on the long-term performance of these slabs were further quantified. The results showed that the mid-span deflection and the hogging moment over the interior support increased significantly over time; both could not be accurately predicted using the typical design methods described in international specifications. The hogging moment declined by 28.0% when a uniform shrinkage profile was adopted for the design of composite slabs, and the mid-span deflection decreased by 15.0% when a constant range of the hogging moment zones was used. The design procedures proposed herein well described the long-term behavior of continuous composite slabs by accounting for the combined effects of the nonuniform shrinkage and time-dependent hogging moment range. The calculated hogging moment and mid-span deflection differed from the measured ones on average by 2.0% and 9.0%.