Analytical Model Development for CLT Diaphragms Loaded Perpendicular to the Length of Panels

The main objective of this study was to develop an analytical model for predicting the diaphragm deflection and the induced shear force at the panel joints when the applied load is perpendicular to the panel length. An equivalent finite-element model was developed to capture the elastic behavior of the diaphragm made from the panels and the connections in between. The analytical model's predictions were compared with predictions from finite-element models. The results of an experimental test were used to partially validate the analytical and numerical models in the absence of full-scale diaphragm test data. A sensitivity analysis was carried out with the aim of finding the most influential parameters in the behavior of the cross-laminated timber (CLT) diaphragm. The connection's stiffness and diaphragm size were varied. The difference in diaphragm deflection was investigated, and it was found that under realistic material properties and geometry, the diaphragm deflection was not strongly related to the connection's stiffness. However, the floor's geometry was the key influencing parameter. A parametric study was performed, and the contribution of each deflection component was quantified for each specific case. It was observed that the floor's flexibility was dominated mainly by the shear deflection of the cross-laminated timber panels as well as the slip in the panel joints as the length of the diaphragm increased. This study proposes a method that designers may use to estimate the in-plane displacement of the cross-laminated timber diaphragm when it is loaded perpendicular to the panel's length.