EVALUATION OF STIFFNESS OF STRUCTURAL GLULAM BEAMS BONDED BY POLYURETHANE RESIN

Abstract

The objective of the study was to technically evaluate the production of Glulam beams bonded by polyurethane adhesive through the determination of the static and dynamic Modulus of Elasticity. For the confection of the structural beams pieces of lumber of Pinus taeda and polyurethane resin were used. All the pieces that composed the beams were classified visually by the number of growth rings and percentage of latewood, and the presence of defects, and later the layers were classified by the dynamic modulus of elasticity. The beams were mounted and pressed, the value of the dynamic modulus of elasticity was estimated and the static was calculated with base on static test on a universal machine. Data analysis was performed using regression analysis. It was concluded that the visual classification used in the selection of pieces was insufficient to obtain the maximum values of stiffness of the beams; the variations of the values of dynamic modulus of elasticity of the layers were affected by the swing of the values of density and wave propagation speed; the correct positioning of the lamellas through dynamic classification methods had as consequence the increase of the elasticity modulus; and there was a very low correlation between the dynamic and static of the beams, being that it was not possible to elaborate an adequate correlation equation between different ways of obtaining the variable.