Experimental and Numerical Analysis of Mixed I-214 Poplar/Pinus sylvestris Laminated Timber Subjected to Bending Loadings

Measurement and Analysis of the Vibration Responses of Piano Soundboards with Different Structures

The effect of structure on the vibration response was explored for four piano soundboards with different but commonly adopted structures. The vibration response was obtained using the free-vibration method, and the values of the dynamic modulus of elasticity and dynamic shear modulus obtained using the free-vibration frequency method (EF and GF) were compared with the dynamic modulus of elasticity obtained using the Euler beam method (EE) and dynamic shear modulus obtained using the free-plate torsional vibration method (GT), respectively. It was found that the soundboards with different structures had different vibration modes and that excitation at different locations highlighted different vibration modes. For all the soundboards analyzed, the EE and GT were higher than EF and GF by 2.2% and 24.3%, respectively. However, the trends of the results of these methods were the same. The four piano soundboards with different structures possessed varying dynamic moduli of elasticity and dynamic shear moduli. These rules are consistent with the grain directions of the soundboards and the anisotropy of the wood (the direction of the units of the soundboards). The results show that the vibration mode of the piano soundboard is complex. The dynamic elastic modulus of the soundboard can be calculated using the Euler beam method. The results provide a reference for studies on the vibration response, material selection, production technology, and testing of piano soundboards.

Predicted and Experimental Bending Behaviour of Glulam Bonded by RPF Adhesive

In this study, alder, spruce, and beech woods were used for homogeneous symmetric, inhomogeneous symmetric (combined) and inhomogeneous non-symmetric glued laminated timber (glulam) beams glued with resorcinol phenol formaldehyde (RPF) adhesive. The aim of this paper is to determine and compare the modulus of elasticity of glulam beams using three methods, i.e., analytical calculation, numerical model (FEM) and experimental testing. As an additional characteristic, the bending strength (MOR) of the beams was determined during experimental testing. Analytical calculation was used to calculate the modulus of elasticity (MOE) of glued laminated timber based on the knowledge of the modulus of elasticity of solid wood and to estimate the location of the neutral axis during bending. According to calculations, for symmetrical combinations, the deviation from the real neutral axis does not exceed 5%. In the case of the modulus of elasticity, the deviation is an average of 4.1% from that of the actual measured beams. The numerical model includes finite element modelling, where the deflection of the modelled beams can be calculated with a deviation of up to 10%. The last method was experimental testing of glued beams using four-point bending, in which, among homogeneous beams, beech glulam beams achieved the highest MOE and MOR, while alder glulam beams achieved the lowest. The combination of wood species resulted in an increase in both MOE and MOR compared to homogeneous spruce and alder beams.

Mechanical Characterization of Glued Laminated Beams Containing Selected Wood Species in the Tension Zone

The aim of this study was to determine the mechanical properties of laminated beams containing selected wood species in the tension zone using a four-point bending test. Three beam types were manufactured with respect to the timber used in the tension zone, i.e., beams containing oak or beech timber of I and II quality class and pine timber with no defects (as defects had been removed). The manufactured beams were assessed with respect to bending strength and the modulus of elasticity. The obtained results were compared with the performance of BSH (Industrial beams GL made in Germany-Brettschichtholz) industrial beams. We concluded that beams made from pine timber are an appropriate alternative to spruce beams. The static bending strength of the beams made with hardwood faces was 70% higher than that of beams made with pine wood. All types of beams manufactured in the laboratory met the requirements of at least the GL24c class.