Introduction.
The performance of multi-story Cross-Laminated Timber (CLT) structures depends on their steel-to-wood connections. Adoption is hindered by a lack of standardized design methods, as current practices often use overly rigid idealizations that fail to capture the joint's true compliance and nonlinear failure.
Aims and Objectives.
This paper presents a verified numerical methodology for simulating the nonlinear stiffness of steel-to-CLT connections. The objective is to establish a procedure for calibrating a Cohesive Zone Model (CZM) using experimental data for global structural analysis.
Materials and Methods.
The study uses the CZM in Ansys Mechanical via 'Contact Debonding', governed by a bilinear Traction-Separation Law (TSL). Model parameters were calibrated against experimental pull-out tests (Mode II dominant) on steel screws in CLT. A key finding is that the model's "interface" stiffness requires iterative adjustment and is not equal to the global "system" stiffness, as it must be decoupled from material elasticity.
Results and Discussion.
The calibrated numerical model replicated experimental force-displacement diagrams with high fidelity. The simulation predicted the peak pull-out force (4.55% discrepancy) and its corresponding displacement (5.67% discrepancy), capturing the elastic phase, peak load, and post-peak softening. The validated methodology provides an engineering-accurate (4–6% deviation) tool for modeling nonlinear joint compliance. This approach allows designers to replace inaccurate rigid-body assumptions, reducing uncertainty and enabling a more realistic stiffness assessment of CLT structures.

Keywords: cross-laminated timber, stiffness of joint connections, joint connection, cohesive zone material, nonlinearity