Procedure for parameter identification and mechanical properties assessment of CLT connections

Connections in cross-laminated timber (CLT) structures are crucial components that can affect the behaviour of the whole structure. A novel framework that integrates the unscented Kalman filter (UKF) as an estimation tool with a hysteretic model is developed to identify the model parameters of a nonlinear system. The UKF estimates the mean and covariance of the model parameters using unscented transformation (UT) by a set of deterministically chosen sample points. The proposed framework is applied to identify the unknown model parameters of CLT connections using available experimental data, where the cycle behaviour of CLT connections is simulated using a spring element assigned to the hysteretic model. The comparison of hysteretic curves between the test and model shows that the results identified with UKF are precise. Two different approaches are proposed: an assessment according to the EN 12512 standard, and a damage accumulation assessment. The EN 12512 standard assessment is evaluated from the elastic stiffness, ductility ratio, and energy dissipation, whereas the damage accumulation assessment considers the effects of low amplitude and accumulated damage. Together, these two methods fully evaluate the identified result and the mechanical characteristics of CLT connections. The proposed procedure of parameter identification using the UKF (together with the mechanical properties assessment) can be applied to other connections in timber engineering.