Fabrication and structural performance of a prototype cross-laminated timber groin vault floor system

Floors constitute a substantial portion of a building’s overall structure and environmental impact. Timber is seen as a more sustainable alternative to conventional steel and concrete structures, particularly with the advent of engineered mass timber. However, the span of timber floors is often limited due to timber’s low stiffness, often requiring very deep floors to satisfy ultimate and serviceability limit states. Additionally, timber exhibits greater compressive strength compared to its tensile strength, which governs its bending capacity. This paper presents a prototype parabolic cross laminated timber floor system that aims to exploit timber’s higher compressive strength and ductility by leveraging the geometric stiffness benefits provided by vaulted structures. To the authors’ knowledge, this study represents the first experimental investigation of a vaulted timber floor system. A quarter scale prototype floor was fabricated by bending initially straight lamellas into the final curved form utilising the singular curvature benefits of a groin vault. The system was subsequently subjected to destructive load testing, undertaken to validate the numerical model and to verify the robustness of the proposed fabrication methodology. The experimental results demonstrate that the structural stiffness of the vaulted floor was accurately predicted by the numerical model, while the measured ultimate strength exceeded the predicted values, therefore validating the analysis approach. Additionally, this study confirms that cross-laminated timber groin vaults can be reliably fabricated using a practical forming method and validated through destructive testing, providing a scalable, carbon-efficient floor system that combines the sustainable advantages of timber with the structural efficiency of vaulted forms, and paves the way for utilising timber vaulted floors in long span structural applications.