P2PE: A finite element formulation for panel-to-panel cross-laminated timber connections

Abstract

This paper presents a new multi-spring finite element formulation called P2PE that simulates the cyclic behavior of panel-to-panel Cross-Laminated Timber (CLT) connections. The formulation comprises five types of uncoupled linear/nonlinear springs representing the fasteners and contact between panels. For instance, the in-plane fastener behavior is simulated with a co-rotational spring and the Modified Richard–Abbott (MRA) model, which is adapted to account for the asymmetry, pinching, degradation, and low-cycle fatigue of timber connections. The model was implemented into ANSYS through user-element/materials, including all computer implementation steps, and can be freely downloaded. The model's response and sensitivity were studied in three demonstrative CLT diaphragms, and it was validated at the connection and assembly stage with benchmark tests. In the first stage, the fastener model was verified with four cyclic CLT connections, while in the second stage, the model was validated with three medium-to-large scale CLT assemblies. The model accurately predicts the stiffness, strength, deformation, slip, and failure mechanisms of both stages. Finally, a parametric analysis of in-plane bending CLT diaphragms was assessed by varying their panel dimensions. This analysis demonstrated that diaphragms with slender panels have larger capacities, fastener energy dissipation, and shear slips but lower ductilities than shorter ones.