Self-tensioning long-span T-shaped spruce and oak web floors with a CLT upper flange. An experimental approach

Abstract

A device is described that makes it possible to automatically apply a post-tensioning force on deflected elements in response to applied gravitational loads. The behaviour of transverse T-section beams is analysed. They are composed of a laminated oak or spruce rib and a cross-laminated timber upper flange (CLT). Fourteen 9 m span beams were subjected to a four-point bending test until failure. Six of the beams include the self-tensioning system to comparatively verify its efficacy. A numerical analysis model was also developed to describe the behaviour of the proposed device, considering a non-linear regime and interaction between moving parts. The post-tensioned elements attained a noteworthy increase in their final load in comparison with the unreinforced beams. On the other hand, in their service situation they showed a major reduction in their average relative deflection. The conclusions indicate that there is a relevant improvement in their behaviour under deformation, even with a reduced structural width. This improvement is highly useful in long-span wooden floors, where restricted deformation is usually the predominant dimensioning criterion to prevent damage to partition walls.