Effect of breathing cracks on the dynamic behavior of cross-laminated timber panels

This study examines the nonlinear vibration behavior of cross-laminated timber (CLT) panels with cracks, both experimentally and analytically. Nonlinearity is caused by cracks opening and closing during vibration. Specifically, cracks caused by shrinkage occur between the narrow surface joints of the outer wood layers, resulting in a so-called 'breathing crack' effect under dynamic loading, even in the absence of global structural damage. An experimental study of a CLT plate excited by a sine sweep was carried out to quantify the nonlinear effects using higher-order frequency response functions. The experimental excitation signal contains unintended higher harmonics caused by the interaction between the shaker and the nonlinear structure. These higher harmonics also indicate nonlinear behavior, leading to deviations from ideal theoretical conditions. The experimental results are compared with a modal model of the plate in which the modal stiffness is displacement-dependent, in order to account for the nonlinear effects. The extent to which the analytical model can reproduce the experimental observations is also investigated. This study contributes to a better understanding of the vibrational behavior of cracked CLT plates and can be used in the context of Structural Health Monitoring.