An elastoplastic solution for earthquake resistant rigid timber shear walls

Abstract

In terms of seismic performance, timber structures have been observed to perform well, in spite of timber being an inherently non-ductile material. This is due mainly to the ductility of the steel-to-timber connections, and the way in which they interact with the timber material. If these connections are detailed to deform plastically, while keeping the timber members elastic, the overall structure achieves ductility. For nailed sheathing-to-framing shear walls and floor diaphragms, the New Zealand structural timber code, NZS3603:1993 [1] allows ductilities of up to four to be assumed. The issue with such an approach is that in a design level earthquake, the deformations required to achieve ductility often renders the structure irreparable, or at least requiring expensive repairs. Recent developments in engineered lumber products have seen the availability of mass timber panels of tremendous strength and stiffness. These include CLT (cross laminated timber) and LVL (laminated veneer lumber) panels. Under typical loading conditions these panels are essentially rigid, and the experiments of Popovski and Karacabeyli [2] demonstrate that the hysteretic behaviour is largely governed by the plastic deformations in the steel bracket connections attaching the walls to the floor. The hysteretic loops bear some resemblance to those of sheathing to framing shear walls, the main difference being they are more tightly pinched. The seismic performance of such walls is adequate, however, damage is still a consequence after an earthquake.