Experimental testing and analytical modelling of single and double post-tensioned CLT shear walls

• Published in: Engineering structures 2022-04, Vol.256, p.114065, Article 114065
• Main Authors: Brown, Justin R., Li, Minghao, Palermo, Alessandro, Pampanin, Stefano, Sarti, Francesco, Nokes, Roger
• Format: Article
• Language: English
• Subjects: Compressive properties; Cross-laminated timber; Earthquake loads; Energy dissipation; Inhomogeneity; Lamella; Lumber; Mathematical analysis; Particle tracking; Particle tracking technology; Post-tensioning; Post-tensioning systems; Precast concrete; Prediction models; Prototypes; Re-centering systems; Reinforced concrete; Screwed connections; Shear walls; Stiffness; Technology; Timber; Timber wall structures; Wood laminates; Wooden structures
• ISSN: 0141-0296; 1873-7323
• DOI: 10.1016/j.engstruct.2022.114065

•Large-scale experimental study on 8.6 m tall post-tensioned (PT) CLT walls.•With screwed connections, the PT double wall (DW) stiffness was almost four times that of a PT single wall.•Timber compressive strains and ‘end-effect’ were investigated with Particle Tracking Technology.•The Modified Monolithic Beam Analogy was verified for PT CLT single and double wall systems.•Analytical prediction models were extended and validated to capture PT DW kinematic rocking mechanisms with one or two base rocking interfaces. Post-tensioned (PT) timber technology - also called Pres-Lam technology - can provide increased strength/stiffness for mass timber seismic load resisting systems while also providing energy dissipation and re-centering capabilities. Initial experimental tests and practical implementation on PT timber structures in the past 15 years primarily utilized laminated veneer lumber (LVL), with some glulam and cross-laminated timber (CLT) prototypes and real-case applications, and their analytical prediction models were extended and adapted from precast concrete to account for unique characteristics of engineered timber. More recently, CLT has emerged into a more dominant global mass timber product. This paper presents a large-scale experimental study on 8.6 m tall PT CLT single and double wall systems. The PT double walls utilized screwed connections at the in-plane joint and U-shaped flexural plates at the foundation to provide coupling effect and energy dissipation. With screwed connections, the PT double wall partial composite action of approximately 70% was achieved and the system stiffness was almost two times that of two PT single walls without partial composite action but of equivalent length. Analytical prediction models, accounting for the peculiar controlled rocking mechanism and originally developed for PT LVL systems were adopted for PT CLT wall systems, were found to have increased compressive toe strain variability due to the increased material inhomogeneity of CLT with non-edge glued lamella. The timber compressive strains and unique ‘end effect’ bearing phenomenon was investigated for the first time with Particle Tracking Technology (PTT). Extensions to the existing PT double wall analytical prediction model were proposed and validated to capture the unique kinematic rocking mechanism where wall uplift occurs due to the strong and stiff screwed in-plane connection between individual walls.