Non destructive vibration tests on timber truss elements

The paper presents a series of vibration tests carried out on timber truss prismatic elements. Free vibrations due to dynamic excitation by impulse loads were measured and analysed to evaluate their mechanical characteristics. They were firstly compared with the results of static tests and ultrasonic tests and then validated by means of analytical and 3D numerical models. The vibration tests were then extensively carried out on the prismatic elements subjected to a constant axial load, with varying that both in tension and in compression, between a large loading field. A correlation between the first bending natural frequency and the stress state magnitude has been proposed and compared with analytical and numerical solutions, for different restraint degrees. The experimental tests aimed also to validate finite elements numerical models used in static and dynamic analyses of timber trusses before and after rehabilitation.