1st Croatian Conference on Earthquake Engineering 1CroCEE 2021

Mass timber products are increasingly used in mid-rise to high-rise buildings. Cross-laminated timber (CLT), in particular, is highly used and plays a major role in timber construction. Balloon-type construction appears to be a particularly advantageous system when using CLT panels –it enables to avoid the compression perpendicular-to-grain in floor diaphragms and the disruption of load patterns in CLT walls. Conversely, balloon-type construction requires high-performance connections to transfer high forces and dissipate energy when under seismic loads. Since most of the knowledge draws to low-rise CLT buildings, there is a lack of design guidance and provisions for mid-rise to high-rise CLT buildings.
In this paper, the seismic response of a 15-story CLT building equipped with multiple-shear slotted-in steel plate hold-down connections is studied. Special attention is paid to examining how such CLT shear-wall connections affect the overall seismic response of the lateral force-resisting system (LFRS). Linear static analysis and linear dynamic analysis were conducted separately to find and compare the fundamental period of the building, the base shear, and the uplift forces.
The results give valuable insights into the structural behaviour of balloon-type CLT construction. Specifically, the analyses confirm that the building is prone to effects of the lateral flexibility and transfers high uplift loads to the foundations under design-level seismic actions. Simplified representations of connection properties showed inappropriate predictions of lateral inter-story drifts, uplift forces, and base shear. Specified design assumptions are needed since seismic parameters and equivalent-static design methods for CLT assemblies are not covered by current building codes. As LFRS of multi-story mass timber CLT buildings largely relies on connection properties and related behaviour, further research is needed to accurately evaluate the effective structural performance of connections such as stiffness, strength, and ductility, and draw anticipated failure modes.