A brief history behind the coupled wall systems:

A current area of emphasis in structural engineering is the search for better ways to improve the seismic resistance of structures. Over the last few years, Reinforced Concrete Coupled Wall structures with RC coupling beams (Fig. 1) have proved to be one of the better solutions towards seismic resistant design due to their ability of sharing the wall moments and thus increasing the resistance of the whole structure against seismic ground motions. However, modern researches suggest that compared to RC coupling beams, structural steel coupling beams or steel-concrete composite coupling beams increase the performance level of the conventional RC coupled wall systems in terms of ductility and resistance. The resulting structural system is referred to as a Hybrid Coupled Wall (HCW) system as shown in Fig. 2 and may be considered to be a dual frame-wall system. These HCW systems have provided better performance in regions of moderate to high seismicity. However, these available hybrid systems may suffer from some drawbacks such as the need for expensive detailing, costly foundations, difficult restoration works as well as a smaller ductility due to two concrete walls. So, to further improve the combination of the RC wall and steel coupling elements, a new innovative HCW system was proposed in the research project INNO-HYCO (Innovative Hybrid and Composite steel-concrete structural solutions for building in seismic area) funded by the European Commission, which consisted of a RC shear wall with dissipative steel coupling beams and steel side columns as shown in Fig. 3. The reinforced concrete wall carries almost all the horizontal shear force while the overturning moments are partially resisted by an axial compression-tension couple developed by the two steel columns rather than by the individual flexural action of the wall alone.