PSI - Issue 5

Antonin Lokaj et al. / Procedia Structural Integrity 5 (2017) 1363–1369 Antonin Lokaj et al. / Structural Integrity Procedia 00 (2017) 000 – 000

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Figure 7 shows shear stresses in the plane of loading in solid timber element. The stress reaches the maximal value of 5.17 MPa in joints with plywood and 3.93 MPa with LVL.

Fig. 7. Shear stress in the timber element in connection with (a) plywood; (b) LVL

3.3. Calculation according to standards With calculation of the bearing capacity using bending moment of loaded joint according to standards (Eurocode 5, 2004; CSN 73 1702, 2007) it is possible to determine the maximal value of vertical force in the glued line of value 4.25 kN for given loading mechanism, where the uniform distribution of shear stress is not ensured. This force corresponds the value of bending moment in the joint 0.85 kNm. If a uniform distribution of the shear stress in the glued joint is ensured, then the minimal carrying capacity will be given with a failure in the inner layer of the glued element and the vertical force value will be 6.80 kN for the given load mechanism according to Fig. 1, which corresponds with the bending moment of 1.36 kNm. 4. Conclusions The average value of the joint carrying capacity with the flexural bindings found by the laboratory tests is much higher than the value determined conservatively according to the relevant standards. It is evident from Figure 6 that the deformation response of the glued joints to the load is linear over the entire loading time. Once the bonding capacity is reached, an immediate fragile fracture occurs. The low ductility of glued joints is one of causes of the relatively conservative values of the carrying capacity of these joints determined according to the applicable standards for the design of timber structures. To increase the safety of these glued joints, it would be desirable to add joints with plastic bonding possibility.

Acknowledgements

This outcome has been achieved with funds of Conceptual development of science, research and innovation assigned to VSB - Technical University of Ostrava by Ministry of Education Youth and Sports of the Czech Republic in 2017.