## 6 Conclusions  
In this study, the behaviour of SCS sandwich slabs with CSC shear connectors was investigated. For this purpose, three specimens were manufactured and tested. Specimens conducted under quasi-static concentrated load. In all specimens, the thickness of steel plates was the constant and concrete core of slab manufactured with different concrete. Three CSC slabs were manufactured using normal concrete, lightweight like concrete and steel fibres reinforced lightweight like concrete. Then, the load-displacement relationship of specimens, ductility, failure modes, maximum bearing capacity and stiffness of specimens were measured. Moreover, in order to show the performance of SCS slabs with proposed CSC connectors, the obtained outcomes were compared with other types of connectors proposed in previous studies. According to the obtained results, the following conclusions can be drawn:  
1. The typical behaviour of the SCS with NWC core in terms of both stiffness and resistance was better than those produced with plain LWC core and LWC core reinforced by steel fibres. However, the NWC core was about 35% heavier than the LWC and SLWC cores that can be a fundamental problem for specific applications such as ship hull;
2. The experiments results illustrated that in areas where stress concentration was more significant, the failure of the shear connectors from the plug welds was inevitable;
3. The use of LWC core decreased significantly the energy absorption at both yield and ultimate points compared with NWC core, while this characteristic was improved with steel fibres about 8% and 27%, respectively, compared with LWC with no steel fibres;
4. The use of LWC core with and without fibres significantly increased ductility. This is in contrast to samples with J-hook connectors. However, it is too early to conclude with this limited number of samples and it can be a more detailed study on the subject of future studies;
5. Using steel fibers reduced the punching shear in SCSSLWC by controlling cracks propagation;  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**Specimen**} & **P\({}_{\text{R}}\) (kN)** & **P\({}_{\text{R}}\) (kN)** & **m\({}_{\text{pl}}\)** & **m\({}_{\text{pl}}\)** & **F\({}_{\text{P}}\) (kN)** & **F\({}  
Except for the SCSLWC slab with LWC core, in the other specimens, the ultimate flexural capacity based on the experiments were in acceptable agreement with the results of the Eurocode 4 (Equation (6)) and the proposed relation by [PERSON] and [PERSON] [32] (Equation (7)) by below 10% error. It is important to note that the Equation (7) was obtained with the NWC core, and future research is needed to predict the inter-layer shear strength (\(P_{R}\)) for CSC system with LWC core and SLWC core under push-out tests.  
M.G. and J.d.B.; formal analysis, M.G. and M.Y.; investigation, A.K. and M.N.; methodology, A.K. and M.Y.; software, M.G.; supervision, M.Y. and J.d.B.; writing--original draft, A.K. and M.Y.; writing--review and editing. J.d.B. All authors have read and agreed to the published version of the manuscript. This research received no external funding.  
The authors wish to thank the CERIS (Civil Engineering Research and Innovation for Sustainability) research centre and the FCT (Foundation for Science and Technology). The authors declare that they have no conflict of interest.  
The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.