Analytical Modeling of Posttensioned C-Shaped CLT Core Walls

Abstract

Post-tensioned (PT) timber technology, also referred to as Pres-Lam (prestressed laminated timber) provides a low damage seismic design solution. So far PT timber research and practical implementation have focused on moment resisting frames, planar shear walls and coupled planar shear wall—or column-wall-column—systems and their analytical prediction models were adapted and extended from precast concrete to account for the unique characteristics of engineered timber. Following a recent experimental study on a PT cross-laminated timber (CLT) C-shaped core-wall system aiming to enhance lateral strength and stiffness, this paper presents an analytical framework/model to capture three unique kinematic rocking mechanisms for a PT C-shaped CLT core-wall system connected primarily with self-tapping screws. Depending on the relative stiffness of the screwed connections to the PT and the energy dissipaters, the model considers different kinematic responses, and that a staged kinematic response could occur at different imposed core-wall base connection rotations. It also accounts for the material inhomogeneity of CLT with nonedge glued lamella and implements a nonlinear spring model for the screwed connections calibrated from component testing and expected elastic core-wall deformations. The study showed that, for the given specimen configurations presented, the compressive flange wall could be neglected for a PT C-shaped CLT core wall. The analytical model was verified against three large-scale 8.6 m high PT C-shaped core-wall experimental tests and the model prediction error was within 10%. The analytical model was limited to capturing the envelope (push-over) curve of a four wall PT C-shaped CLT core-wall system.