Behaviour of coupling beams having vertical slits at the ends

Architectural considerations and functional use result in door openings on the shear walls of tunnel form buildings, which cause coupled shear walls to be connected by short, deep and thin coupling beams. These coupling beams are subjected to higher shear forces and their thickness becomes generally less than 250mm for the tunnel form buildings, and much less than their counterparts in conventional reinforced concrete structures. It is simply not possible to design practically constructible coupling beams in the tunnel form buildings. In a coupled shear wall system, shear forces acting on the coupling beams can be reduced simply by the application of vertical separation joints (slits) at the ends of the coupling beams. As a design alternative, the use of slit connections at the ends of the coupling beams to be able to decrease the shear stiffness and shear forces was analytically investigated. Shear stiffness terms of common slit connected coupling beams (SCCBs) were derived by using plane stress finite elements. To be specific, extensive parametric study with respect to the geometry of a SCCB was carried out. Coupling beam heights, coupling beam lengths, slit heights and slit lengths were varied in an extensive parametric study to demonstrate their influences on the shear stiffness terms.