System effects in T-shaped timber shear walls: Effects of transverse walls, diaphragms, and axial loading

This paper investigates the effects of transverse shear walls (TSWs), out-of-plane bending stiffness of diaphragms (FDIA), and axial loading (AXL) on the lateral response of strong wood-frame shear walls (SWs) used for multistory light frame timber buildings (LFTBs) located in highly active seismic zones. Experimental tests were conducted to understand the requirements for SW-to-TSW connections to achieve desirable TSW effects in non-planar SWs and to characterize the lateral cyclic response of T-shaped SW assemblies with and without diaphragms and axial load. Both slotted and screwed connections were evaluated as SW-to-TSW connections, and both showed sufficient stiffness and strength to achieve TSW effects. However, the slotted connection is preferred because it has a more ductile failure mode. Tests on T-shaped SW assemblies with and without diaphragms and axial load revealed that TSWs significantly enhance the lateral stiffness and strength but reduce the deformation capacity with respect to that of planar SWs. FDIA and AXL effects further influence the stiffness and strength, overcoming the limitation of smaller deformation capacity in T-shaped SWs without diaphragms. Diaphragms also make the T-shaped SW response more symmetrical and improve the evolution of the secant stiffness, the cumulative dissipated energy, and the equivalent viscous damping over increasing levels of lateral drift. Numerical analyses of a theoretical building model with T-shaped SWs show significant reductions in lateral drift (up to 46%) and uplift (up to 100%) compared to the case with planar SWs only, emphasizing the importance of considering system effects in the seismic design of LFTBs.