# Shrinkage-Induced Response of Composite Steel-Concrete Slabs: A State-of-the-Art Review
## 2 Time-Dependent Concrete Response in Composite Steel-Concrete Slabs  
The time-dependent response of composite slabs is influenced by the presence of the profiled steel sheeting that prevents the concrete to dry from its underside, while enabling it to dry from its upper surface. This non-symmetric exposure drying condition is depicted in Figure 2. In particular, the exposure drying conditions of the top and bottom surfaces are depicted in Figure 2a. Under these conditions, the qualitative profile induced by shrinkage can be described by the non-linear curve shown in Figure 2b that highlights the significant drying that takes place in the vicinity of the top exposed surface. For design purposes, this non-uniform distribution can be simplified into a linearly varying distribution, as also depicted in Figure 2b. This simplification is considered acceptable for routine design [11; 12; 13] as long as the service response of the composite slab under consideration is not significantly affected by possible concrete cracking. In fact, in the linearly varying distribution, the self-equilibrating eigenstresses produced by the non-linear profile are not captured and, therefore, neglected. Extensive work has been carried out in the last decade to characterize the shrinkage response of the concrete induced by the non-symmetric drying conditions. In these works, shrinkage strains were monitored experimentally for small-scaled concrete samples that were cast on different profiled steel sheeting to replicate the actual drying behavior of composite slabs [14; 15; 16; 17]. Additional specimens were also cast without the steel sheeting to remove the contribution of its stiffness in the evaluation of the total deformation (that could be regarded as free shrinkage strain measurements) while the barrier to moisture egress was provided to the underside of the slab by the presence of epoxy resin or plastic sheets [14; 15; 16; 17; 18; 19; 20]. In these tests, all four sides of the small-scale slab samples were sealed to reproduce the continuity of the slab and the real drying scenario that occurs in a composite  
Figure 2: Typical exposure conditions of composite steel-concrete slab and qualitative representations of the shrinkage profiles: (**a**) exposure drying conditions, (**b**) shrinkage profiles. floor. The details of the small-scale slab samples tested to date are summarized in Table 1 and typical experimental setups are depicted in Figure 3.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \multirow{2}{*}{**Ref. **} & \multirow{2}{*}{ \begin{tabular}{c} **Sample** \\ **ID** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(f_{c}\)\({}^{1}\)** \\ **[MPa]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(t_{0}\)\({}^{1}\)** \\ **[days]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(t_{k}\)\({}^{1}\)** \\ **[1]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(L\)\({}^{1}\)** \\ **[1]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(b\)\({}^{1}\)** \\ **[1]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **\(D\)\({}^{1}\)** \\ **[1]** \\ \end{tabular}  } & \multirow{2}{*}{ \begin{tabular}{c} **Profiled Steel** \\ **Sheeting** \\ \end{tabular}  } & \multirow{2}{*}{**Remarks**} \\ \cline{4-4} \cline{6-11}  & & S1 & & & & & & None & Solid slab \({}^{2}\) \\ \multirow{2}{*}{[14]} & S2 & 33.7 & 8 & 239 & 900 & 900 & 180 & None & Solid slab \({}^{3}\) \\  & S3 & & & & & & & \
\begin{tabular}{c} Condeck HP\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\)\({}^{\circledR}\) \\ \hline \multirow{4}{*}{[15]} & \begin{tabular}{c} **S120** \\ **[18]** \\ \end{tabular}