The aim of this work was to study if a hollow and 30 % lighter cross laminated timber (CLT) slab has the same structural performance for out of plane bending compared to a conventional CLT slab. Earlier research where such a hollow core CLT (HCCLT) was investigated has shown promising results. However, when producing a HCCLT slab insufficient gluing pressure may occur in some lamellas when using a hydraulic press method. Therefore, it is suggested that a vacuum press technology is applied to produce HCCLT elements.

In this study, a five-layered solid CLT model was developed using a finite element (FE) software (Abaqus). Validation of the model was proven by comparing slab deflection at mid span with corresponding hand calculations. Results for the HCCLT slab, both for ultimate limit state (ULS) and serviceability limit state (SLS), were within standard limits for out-of-plane structural behaviour. The mechanical behaviour in out of plane loading with spaced lamellas in CLT is presented. Thereafter, a FE-model for HCCLT was developed.

In future studies, HCCLT should be manufactured and loaded until failure by certified CLT manufacturers. Delamination tests should be carried out according to FprEN 16351. The empirical collected data from such tests should be used to develop practical calculation methods.