## 2 Concepts and Theoretical Analysis of SDC Wall
### Binding Bars with Reinforcement Enhancements  
Headed studs, interlocked J-hooks, and binding bars [35], as shown in Figure 3, were invented for SCS composite walls used in high-rise buildings and nuclear building to improve the integrity of composite walls. The overlapped headed shear studs were commonly used in the steel-concrete (SC) composite structure due to its high capacity and construction efficiency. However, the tensile resistance of the overlapped headed studs profoundly depends on the confinement of concrete and this disadvantage appears more when significant cracks developed in the concrete core under extreme loads. Double J-hook connectors have equivalent structural performances and could provide a certain degree of tensile resistance without the confinement of concrete. However, high manufacturing accuracy and complexity contributed negatively to the promotion of double J-hook connectors. Meanwhile, binding bar connectors have been more popular due to the equivalent structural performance and fast installation. [PERSON] et al. [36; 37] studied the axial load behavior of square and rectangular concrete-filled steel tubular (CFT) stub columns with binding bars. Experimental results indicated that the binding bars increased the confinement of the concrete core, delayed local buckling of the tube, and improved the ductility of CFT columns. [PERSON] et al. [38] studied the seismic behavior of the SCS sandwich wall with tie bar (bolted connections). Experiments showed that the specimens failed mainly by local buckling of the steel plates. [PERSON] et al. [39] proposed a composite shear wall with double steel plates (CCSPW) and infilled concrete with binding bars. The results demonstrated great seismic performance of the wall. [PERSON] et al. [40] also experimentally studied the seismic behavior of CCSPW. It was observed that the bolt connections were failed when the horizontal loading reached a peak value which led to buckling of the steel plates. [PERSON] et al. [7] proposed SCS sandwich walls with heads studs and through connectors. The results from the tests revealed that ultimate compressive resistance and the ductility of SCS sandwich walls significantly increased due to the existence of the connectors. However, adopting the binding bars in SCS sandwich walls mobilized additional acts in the drilling holes of the steel plates and raised the stress concentration and compromised the face integrity in the steel plates. Considering the structural behavior and construction efficiency of the above connectors, this manuscript has developed a connection technology, which consists of a binding bar with several screw nuts, two bilateral steel sheets, and a sleeve. The binding bars are bolted to the two steel face plates of SDC walls through the holes. The bilateral steel sheets are threaded connected with the bonding bar inside of both steel plates and the sleeve covers the damping roll. There are four distinct features of the developed connector technology compared with the traditional connectors:  
1. Adopting the binding bars avoids the manufacturing complexity of J-hooks and welding of studs. 2. The steel sheets can reduce the stress concentration effect caused by the holes on the steel plates. This is because of the internal force transmission to the vicinity of the hole can be partially shared by the steel sheets. 3. The steel sheets can also reduce the influence of the initial defects in the steel face plates. When the steel face plates are too thin to guarantee the flatness of the steel plate or the bolt spacing is too large to ensure that the concrete core, rubber layer, and steel face plates work together, steel sheets with outer screw nuts can compact the steel face plates to reduce the influence of initial concave of the steel face plates. 4. The steel sheets and sleeves can provide confinement on concrete and increase the steel content of the cross-section to improve the compressive behavior of composite walls.