Influence of boundary conditions on the natural frequencies and damping of timber beams of sweet chestnut

Steel supports designed for timber structures do not always correspond with the theoretical constraints considered in the structural design. The degree of fixation provided by the supports affects the dynamic properties of structural systems. The objective of this work is to analyse the influence of different support conditions on the natural frequencies and on the damping properties of Castanea sativa Mill. timber beams. Dynamic vibration tests were performed on eight 40 × 100 × 2500 mm3 chestnut timber beams and signal processing was applied to obtain the natural frequencies and the damping ratio. Each beam was considered in three support systems: one simulating the free-free condition, and the other two were obtained by supporting them on different steel fasteners. Experimental natural frequencies were then compared to numerical values. The experimental natural frequencies did not show statistically significant differences between the two steel supports analysed. For the first flexural frequency, experimental values showed statistically significant differences with respect to the numerical results from pinned-pinned condition for the two steel supports studied. The values obtained of damping ratio were slightly higher than the values presented in the Eurocode 5 for beams with joints.