Glulam assessment by means of NDT

Glued laminated (glulam) timber structures have a good durability, however they are subjected to possible decay phenomena caused by surrounding conditions as weathering. In these cases, an assessment of the structural reliability is required and consequently a procedure of investigation able to estimate physical and mechanical characteristics of the glulam is needed too. Non-destructive tests are very simple to be carried out directly on the structure and can be useful for this purpose if it’s possible to correlate the results with the density and the mechanical proper- ties of timber with a fair reliability. Thus, the aim of the experimental campaign performed in the Laboratory PRiSMa (Proof testing and Research in Structures and Materials) of the Roma Tre University, was to improve the knowledge about the effectiveness of NDT techniques for the glulam assessment. The springers of some three-hinged arches made in glulam were dismissed and substituted with steel components because of the degradation due to weathering exposition. Therefore, the dis- missed springers were cut to extract some specimens for experimental tests. Nowdays, 8 bending tests on beam specimens and 10 compression tests perpendicular to the grain on prismatic speci- mens were performed. All the mentioned specimens were subjected to preliminary NDT as the penetration tests with the woodpecker and the resistograph, and the ultrasound pulse velocity measurement along all direc- tions (longitudinal and perpendicular to the grain). Results were processed to evaluate the correlation between the mechanical and physical charac- teristics of timber (density, compressive/flexural strength, elastic modulus) and the non-destructive measures. Results of the destructive tests have also been compared with the mechanical character- istics of the original glulam strength class in order to evaluate the decay due to weathering. Some good results have been obtained encouraging the research to go on with some more tests.