Structural Performance of CLT Shear Walls with Hyperelastic Hold Downs

Abstract

Cross-laminated timber (CLT) provides a solution for numerous structural applications, including entire seismic force resisting systems. The primary objective of the research presented herein was to develop a CLT shear wall system with hyperelastic elastomeric hold downs (HDs) that provide the required uplift resistance and deformability, so that the CLT panels develop coupled-panel rocking behavior, without strength and stiffness degradation in the HDs. Secondary objectives consisted of the mechanical characterization of the hyperelastic HD as a function of its geometry, and the determination of minimum edge and end distances to avoid brittle failure in the CLT, for development of capacity-based design procedures for this system. To achieve these objectives, the individual components (HDs, steel rods, spline joints, and CLT panels) were tested along with a total of 66 full-scale shear walls. The tests demonstrated that (1) the HDs remain elastic under rocking kinematics provided that the elastic limit of the steel rod is not exceeded, (2) sufficient CLT width can prevent undesired brittle CLT failure before steel yielding in the rods, and (3) the shear wall strength and stiffness is a function of HD size and the panel-to-panel shear connection properties. The hyperelastic HD assembly provides design engineers with a low-damage alternative to contemporary HD solutions for platform-type CLT shear walls.