ELIMINATING THE COUPLING BEAMS OF UPPER STORIES IN TORSIONAL IRREGULAR MID-RISE RC-COUPLED SHEAR WALL STRUCTURES

Based on valid seismic codes, the structure drift should be controlled to satisfy service requirements. Although one of the most conventional choices is to apply dual reinforced concrete frames, placing openings in shear walls are sometimes unavoidable due to architectural demands. In the other hand, since the coupling beam (C-beam) between walls may reduce the net height of story, it is desirable to omit mentioned C-beam. Combination of moment-resisting frames shear mode and RC-shear wall flexural mode behaviors of dual RC-frames, will lead to special mode shape in which the frames and the shear wall support each other in bottom stories while, in upper stories the excessive deformation of the shear wall may increase the lateral load carried by the moment-frames. It seems that reduction of shear walls flexural stiffness by eliminating the coupling beams in upper stories may lead to less bending moment and shear force in frames. Further, eliminating the coupling beams can decrease the limitations of interior design at least in the upper stories. Therefore, in this paper five torsional irregular dual RC mid-rise buildings in same site and different stories (3