## 3 Results and Discussion
### Comparison of the Experimental Results with Previous Researches  
To show the performance of proposed connectors in this study, the obtained results were compared with other types of connectors, including J-hook [24] and stud bolt connectors [29]. According to Table 8, although, the section area of CSCs is about twice j-hook and stud bolt connectors, this is the least section area that could be used as CSC connector. On the other hand, the number of CSCs for this study is 26% less than ones of J-hook and stud bolt SCS systems. Other specifications are the same except for the specimen SCS6-100, where the strength of NWC core is approximately 48% more than the strength of the NWC core of CSC and stud bolt systems. In addition, the thickness of the concrete core is 100 mm, while other specimens have a thickness of 78 to 80 mm. Besides, it should be noted that, as there is a relation between the modulus of elasticity and the ultimate resistance of the specimens,  
Figure 13: Punching shear failure mode in the specimens. the value of \(\text{E}_{\text{c}}\) for different specimens was also compared, as presented in Table 8. Regarding these results, the modulus of elasticity increased by increasing the compressive strength of the concrete core. Therefore, the maximum load-bearing capacity improved with the increase of the modulus of elasticity (\(\text{E}_{\text{c}}\)). The obtained outcomes are represented in Figures 15-18. According to Figure 15, in the specimen with J-hook connectors and NWC core, bearing capacity is dropped suddenly after the maximum resistance point of about 600 kN. According to this rapid reduction, failure occurs as a punching shear state. Conversely, using CSC shear connectors leads to increase bearing capacity without any drop in resistant; however, specimens with J-hook connectors deformed more. As it is seen in Figures 16 and 17 with LWC and SLWC core respectively, the reduction after the maximum bearing point of about 250 kN occurs for J-hook connectors due to punching shear failure; however, this sudden drop in resistance is not observed in any of the slabs with CSC connectors. Additionally, compared with those manufactured using stud bolt connectors, CSC connectors resulted in higher bearing capacity of SCS slabs (Figure 18). Figure 16: The comparison of the load-displacement curve of SCS slabs with J- hook and CSC connectors with LWC. Figure 17: The comparison of the load-displacement curve of SCS slabs with J- hook and CSC connectors with SLWC core. Figure 15: The comparison of the load-displacement curve of SCS slabs with J-hook and CSC connectors with NWC core. Stiffness is an essential property and shows the resistance of specimens against the failure. This property is defined as an initial slop of the load-displacement curve of the specimens. So, the stiffness of specimens was measured. Moreover, to assess the structural performance of used connectors, the stiffness of specimens was also compared with that of previous investigation using J-hook and stud bolt connectors, as represented in Figures 15-18 [24,29]. The obtained results of the stiffness of specimens are demonstrated in Figure 19. According to this figure, the stiffness of SCS slabs with CSC connectors proposed in this study are higher than those produced with J-hook connectors by [PERSON] and [PERSON] [24] and the stud bolt connectors by [PERSON] and [PERSON] [29], except for J-hook system filled by NWC core; however it should be noted that the thickness of the NWC core of the SCS with J-hook connectors is 100 mm, while the thickness of the other samples is about 80 mm. Structures under the external force should have enough potential to compensate the energy resulted from the applied load. For this aim, the energy absorption of the samples under the quasi-static  
Figure 19: Compression between the stiffness of the specimens with different types of connectors. Figure 18: The comparison of the load-displacement curve of SCS slabs with stud bolt and CSC connectors with NWC core.