# Study of Innovative Connector for Steel-Concrete Composite Structures
## 1 Introduction  
The most popular structural solution of the steel-concrete composite beams are beams with slabs concreted on profiled steel sheets. The sheet metal, apart from cooperating with concrete in the use phase of the slab, is also a working platform and formwork lost in the execution phase [1; 2; 3]. From a structural point of view, the slab serves as reinforcement for positive bending moments. In composite beams, it is important to ensure the proper connection of the steel and concrete parts. In bent elements, the natural adhesion occurring between the steel section and the concrete slab does not ensure the transfer of forces that appear at the contact area of the two materials. The purpose of the fasteners is to transfer the longitudinal delamination forces arising at the contact surface and to prevent the slab from detaching from the steel beam [4; 5]. To this day, in building construction, headed studs are most often used to join the slab with the steel beam [6; 7; 8; 9; 10]. They absorb both shear and tensile forces, and their loadcapacity is the same in all directions. In addition, they do not constitute a significant obstacle to the reinforcement of the slab. As shown in [11; 12], note that, in solid slabs, the pin acts as a cantilever. In plates on corrugated sheets, the greatest loads act on the upper part of the stud, protruding above the plane of the upper corrugation of the sheet. In this area, the stud presses against the concrete and causes it to crush. However, on the other side of the stud, a crack in the concrete appears. Despite the many known methods of connection used in the composite structures, research is still being carried out to create new solutions. The authors of the article [3] presented the possibility of connecting the steel beam with the slab using a non-welded hat connector. Connectors made of the hat section 80 \(\times\) 85 \(\times\) 3 made of S235 steel were fastened to the beam with four driven nails and a diameter of \(\phi\) = 4.5 mm. The test results showed that a fastener made of a 100 mm long sheet corrugation cannot be used because its slip capacity is only 2.6 mm. A connector made of a 60 mm long sheet corrugation can be used to join steel-concrete beams, as its slip is 7.1 mm. An innovative type of shear connector was also presented by the authors of [13]. Instead of shear studs, a continuous hat channel was used. The structural system consisted of: steel beams made of two cold-formed profiles, corrugated steel sheet, hat channels, and the concrete slab with transverse reinforcement. Self-drilling fasteners were used to connect all steel parts. The authors of the paper [13] claimed that the hat channel was able to effectively transfer the shear between the steel and the concrete to achieve the connection. The Hiliti Stripcon connector made of the corrugated sheet connecting the beam with the slab on the corrugated sheet is shown in [1]. The connector is made of an 80 mm wide S280 GD steel sheet. In each corrugation of the sheet, the connector is fastened with four Hiliti driven nails. In addition, to increase the mechanical connection, holes were used in the connector plate. A characteristic feature of this solution is the greater ability to slip compared to headed studs. A completely different approach to joining the steel profile with the prefabricated reinforced concrete slab is presented in the works [14; 15; 16], where glue was used as a connector. Experimental results show that it is possible to make a composite structure glued with glue. The connection provided by the epoxy adhesive is non-slip at the steel-concrete interface. In the case of joining with polyurethane glue, the connection is flexible. The failure of the composite beams was caused by the plasticization of the steel girder or cracking of the concrete slab. One of the solutions that deserves special attention is the system of connectors made of a properly shaped steel beam web, the so-called \"composite dowels\".