Strenght prediction of the glulam beams based on the information of knots in single lamellas

In this thesis the effect of knots on the structural behaviour in terms of stiffness and strength was studied, in a linear elastic analysis, using Abaqus. Test setups from European standard EN 408 and tests performed in the research centre “Holzforschung München” were modelled, in order to compute mechanical properties and have a qualitative and quantitative estimation of the effect of knots. The attention was then led to the effect of the adhesive layer on the numerical model, for which there is little available literature. Different types of adhesive were used in the modelling procedure to study their effects on the mechanical behaviour of wood. It is shown that the adhesive effect is generally negligible and failure is occurring in wood. All tests results and simulations are referred to thin layers of adhesive. The last part of the study focused on the effect of stress concentrations next to knots. The maximum longitudinal stress was used to predict the glulam strength through the correlation between stress from analysis and strength from tests on single boards. The accuracy of results is not high for slightly defected boards, because other different phenomena outer than knots should be taken into account (fiber deviation, microcracks ecc.). However, predictions are relatively good for the boards with knots and not clusters. The objective of this study was finding an estimation of strength starting from a computationally efficient model, in which few input data are required. Other researches in literature developed tools and models for an accurate analysis of strength, however the required computational resources and input parameters are sensitively increasing.