Three-dimensional stress analysis and design of cross-laminated timber panels using full-layerwise-theory-based finite element method

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Cross-laminated timber (CLT) panels have an increasing market share and extensive application in civil engineering, as full size walls or light floor structures. Due to their low environmental impact, excellent thermal characteristics and high mechanical performance, they are being extensively applied instead of conventional mineral-based building materials. Thick and orthogonal structure of CLT provides the considerable stiffness with the low weight and makes such panels particularly suitable in seismic-prone areas. The ease of assembly allows prefabrication and reduces construction time and cost.Current models for calculating the stress-deformation state of a CLT loaded out-of-plane mainly emerged from the long tradition of using very simple one-dimensional (beam-like) elements in timber structures. The paper tends to overcome some limitations of the current models by using the full-layerwise plate theory (FLWT) of Reddy, serving as a basis for the implementation of layered finite elements. The proposed model accounts for the complex 3D stress state in CLT loaded out-of-plane and implies an original procedure for stress calculation. It is implemented using the original object-oriented MATLAB framework, while the graphical user interface for pre- and post-processing is developed using GiD.The presented approach is validated using the available numerical and experimental data in the literature, and compared against the commonly used methods for the design of CLT. Finally, the 3D stress-deformation state in the CLT slab of complex shape (commonly used in building structures) is obtained using the FLWT-based finite elements. The results are validated against the numerical data from the commercial software, and then used for checking of the ultimate and serviceability limit states for CLT slab according to Eurocode 5. Excellent agreement of the obtained results confirmed the potential of the proposed model to become a promising tool for engineering design of CLT slabs of arbitrary geometry.