# Study of Innovative Connector for Steel-Concrete Composite Structures
## 4 Discussion
The adoption of two nails and increasing the thickness of the sheet from 1.00 to 1.25 mm resulted in an increase in the slip by 25%, because in model no. 4, it was 14.40 mm. Therefore, the slip of model no. 2 is 47% higher than that of model no. 4. Reducing the number of nails (while maintaining the nominally identical sheet thickness) increases the slip, because the stiffness of the fastener decreases. An increase in the thickness of the sheet (while maintaining the same number of nails) also increases the slip capacity. This is because the use of a thicker sheet causes the nails to become more loaded than in the case of a thinner sheet. Push-out test is recommended by the EN 1994-1-1 [20] standard to verify the behavior of new types of connectors (other than headed studs) that can be used in real-world conditions. The recommended test is intended to replicate the pure shear performance of the connectors. However, it should be taken into account that, under real conditions, connectors used in steel-concrete composite beams may be sheared as a result of the movement of the slab relative to the beam, as well as compressed and sometimes even stretched. Additionally, the push-out shear test may contain potential biases, because the movement of the I-beam, in addition to shearing the connectors, may also cause the slabs to detach due to the resulting lateral forces. The proposed solution of fastener for composite structures met the assumed load capacity expectations and it is easy in fabrication. The use of traditional headed stud fasteners required special mounting equipment. Such devices require high-current electrical power, which negatively affects the environment. At the same time, resourceful people with appropriate qualifications are necessary for the installation of headed studs. These limitations are eliminated in the proposed connector solution in the form of the corrugated sheet fastened with shot nails. A device for driving nails is available in every construction factory and even on construction sites. This is due to the universal use of driven nails, which are used in various types of building structures. These types of devices do not require electricity, which reduces the negative impact on the environment, unlike traditional solutions requiring welding. To make a steel-concrete composite beam with traditional headed connectors, the corrugated sheet is required. This sheet is attached to the I-beam with nails, and headed studs are needed to connect the sheet with the concrete slab. In the proposed solution, head studs were eliminated. This contributed to reducing the weight of the composite beam and shortening the time needed to manufacture the beam, because one operation was eliminated, i.e., the assembly of studs. Reducing the assembly time also translates into lower production costs. In both solutions, the weight of the sheet metal and nails as well as the time necessary to attach the sheet to the I-beam are estimated to be similar. The conducted research proved the thesis that it is possible to provide the steel-concrete connection without the use of additional connecting components. In the tested connector, the friction joint is created thanks to the use of especially shaped folds of the sheet in the so-called dovetail. The shape of such a cross-section improves the stability of the sheet, as well as acts as hooks connecting to the concrete, preventing the global buckling of the slab. An additional advantage of this sheet is the ability to easily suspend finishing elements by using dedicated hangers fixed in the fold. The formwork is not performed during the manufacturing of steel-concrete composite structures with the analyzed connector, because the corrugated sheet performs this function. The proposed solution is not an alternative to headed studs, but it a solution that can be used in other applications. Design the resistance of the headed stud is about 60 kN. Design resistance of the connector made of dovetail sheet and shot nails is about 30 kN.