Rocking Timber Structure with Slip-Friction Connectors Conceptualized As a Plastically Deformable Hinge within a Multistory Shear Wall

Abstract

Recent experiments on a 2.44×2.44 m rigid timber wall panel with slip-friction connectors have demonstrated the feasibility of enabling elastoplastic behavior in structures that would otherwise be essentially rigid. The slip-friction connectors are adopted as the hold-downs that anchor the ends of the wall to the foundation. These replace the traditionally used steel bracket hold-downs, which relied on inelastic damage to the screw or nail connections for energy dissipation. Overturning resistance of the wall directly relates to the slip-force in the slip-friction connectors. On the slip-force being reached, the intention is that the wall rocks in a controlled manner. A numerical study demonstrates the energy dissipation advantages of this approach. A direct-displacement-based design procedure is proposed for a multistory wall with slip-friction connectors. The wall is numerically modeled, and its response to earthquake time-history loadings compared with that of an idealized structure with a single plastic deformable hinge at the base. Results show that when gravity is not considered, the wall structure with slip-friction connectors behaves almost identically to that of its idealized equivalent. Taking into consideration higher mode effects of multi-degree-of-freedom (MDOF) rocking structures, base shears, and response accelerations are capped to the level expected, but residual displacements are significant. However, with self-weight considered, residual displacements of the wall are trivially small, and maximum displacements are also, in general, reduced. For the wall configurations investigated, the results suggest that a rocking timber wall unit at the base of a multistory shear wall will not only provide the load limiting benefits of a plastically deformable hinge, but also minimize maximum drifts, and allow for the structure to restore to its original position.