Finite Element Modeling of Mass Timber Diaphragms : Validation based on experimental results

Sammanfattning

Cross-laminated timber diaphragms are designed using a rigid diaphragm approach, assuming rigid-body behavior. However, studies have shown that while the panels tend to behave rigidly, the connections exhibit significant flexibility. Various methods exist to account for this flexibility in mass timber diaphragms. This thesis aims to develop linear finite element (FE) models to evaluate the out-of-plane behavior of mass timber diaphragms using experimental data from full-scale shake table tests conducted at the University of California, San Diego (UCSD). Four mass timber systems, Cross-laminated timber, Glue-laminated timber, Nail-laminated timber, and Dowel-laminated timber, were individually modeled. The FE models, developed in OpenSeesPy, are shell-based and incorporate orthotropic material properties, panel-to-beam connections, and panel-to-panel connections. Limitations of the study include the assumption of linear material and connection behavior. Additionally, the validation is restricted to out-of-plane response and vertical accelerations measured during the testing conducted at UCSD. Model validation was performed using Operational Modal Analysis based on experimental data from the tests conducted at UCSD. Mode shapes were extracted using ARTeMIS and compared with those from the FE models using the Modal Assurance Criterion. Additionally, a convergence study is carried out to ensure that the mesh is sufficiently accurate. The validated models can represent the out-of-plane behavior observed in the diaphragms during the UCSD testing, thus, the chosen modeling approach is proven suitable for this type of modeling. Furthermore, the FE models provide a platform for future dynamic analyses and can be integrated into a complete structural model of the test building. They also serve as a framework for incorporating non-linear material and connection behavior, as well as more detailed connection modeling. Ultimately, this study contributes to a deeper understanding of the flexible behavior observed in mass timber diaphragms and supports the development of more accurate modeling approaches.