Characterization of the out-of-plane behavior of CLT panel connections

The increasing damage caused by natural hazards has stimulated the research for new construction systems that can perform well during these events. Cross Laminated Timber (CLT) is a relatively new and robust construction material that has been extensively investigated under seismic load conditions, during which it exhibited good performance. However, its potential as a resilient alternative for natural hazard events that primarily engage the out-of-plane response of the building (e.g., hurricanes, flooding, storm surge, and tsunamis) has not yet been explored. A critical step to assess the performance of platform type CLT buildings to these events is to understand and characterize their out-of-plane behavior as they are critical in the effective load transfer to the in-plane resisting elements. However, there is a major lack of knowledge on the behavior of CLT panel connections subjected to out-of-plane load conditions. This creates a significant barrier in the adoption of CLT structures for resilient wood buildings and communities. The objective of this study is to advance the current understanding and characterize the behavior of CLT panel connections under out-of-plane-induced load conditions. A secondary objective is to identify key connection design parameters and quantify their influences on the out-of-plane behavior. To achieve these objectives, high-fidelity nonlinear numerical models of CLT panel connections are developed, experimentally validated, and investigated under two tsunami-induced out-of-plane load conditions. A numerical investigation with 48 numerical models is performed and the analysis of variance (ANOVA) method is used to quantify the influences of three key connection design parameters on the out-of-plane behavior of CLT panel connections. The results indicated that the crushing of the wall panel's wood fibers dictated the behavior in one of the out-of-plane directions considered while the axial withdrawal of the nails on the wall side of the connections dictated the behavior in the other direction. A simplified equation and a mechanics-based procedure were developed for estimating the load capacity and quantifying the nail contribution to the capacity of the connections under the out-of-plane load conditions considered.