Investigation of the Mechanical Response of Monolithic Shearwalls with Openings

Abstract

The current research project presents a study combining numerical analyses and experimental campaigns to evaluate the structural performance of cross-laminated timber (CLT) shearwalls with openings.

The results of an extensive numerical analysis using a validated Finite Element model is presented with the aim to investigate the influence of the geometrical and mechanical properties of lintel beams and parapets on the stiffness and strength of multi-storey CLT shearwalls with symmetric door or window openings. The influence of construction techniques, where the opening is cut out of the panel or constructed using separate elements is investigated. The results of the analysis show that in general, monolithic models resulted in significantly higher strength and stiffness values compared to those obtained from models assuming segmented shearwalls. The study particularly highlights the importance of the parapet in the overall behaviour and failure mechanism, even though no structural function is typically associated with it.

A comprehensive experimental campaign involving 36 beams with vertical outer layers and two different lay-ups was conducted to evaluate the applicability of analytical models originally developed for beams with horizontal outer layers. The experimental results reveal significant differences between 3-ply and 5-ply specimens, indicating an inverse correlation between bending strength and lamination thickness, and successfully verifying the adapted analytical models against both newly obtained data and existing literature.

Furthermore, the study addresses an identified gap in the literature regarding panel failure modes in monolithic CLT shearwalls with cut-out openings. An experimental investigation on 12 full-scale shearwalls designed to reach failure within the CLT panel showed that all tested specimens initiated cracking in the lintel or parapet, with ultimate failure occurring at the holddowns. The numerical predictions corresponded well with the experimental load-displacement curves and the observed failure patterns, underscoring the models' capacity to capture the complex failure mechanisms of CLT shearwalls.

This study advances the understanding of how construction methodology interacts to influence the kinematic behaviour and failure modes in CLT shearwalls with openings, providing valuable insights for both the design and analysis of such structural elements.