Assessment of the structural integrity of glulam using modal analysis and finite element updating

Abstract

The increasing adoption of glued laminated timber (Glulam) as an environmentally conscious material in construction has been driven by its excellent structural properties and lower carbon footprint compared to other conventional materials. However, its organic nature underscores the need to ensure the long-term integrity of these glulam structures. This paper proposes a novel approach to non-destructive testing (NDT) through the combined application of modal analysis and updated finite element modelling. These advanced techniques allow a more accurate and detailed assessment of the structural condition of glulam. Modal analysis identifies changes in natural frequencies and vibration modes caused by potential material degradation, providing valuable structural health information without compromising the integrity of the material. To achieve this objective, the paper proposes to compare the real values measured in the modal analysis with those obtained from the numerical model by formulating an objective function that measures the error between the two. The differences between the two models are reduced using techniques based on Particle Swarm Optimization (PSO). The work presents a specific formulation aimed at achieving greater efficiency in the search for defects in this material. The results of the proposed method are verified by laboratory tests. For this purpose, glulam samples with different defects were tested and their identification was verified by updating the finite element models, demonstrating the ability and accuracy of the method to identify areas where the structural stiffness has decreased due to deterioration.