BENDING PROPERTIES OF WOOD I-JOIST MADE WITH PINUS (<em>PINUS</em> SP.) AND CURUPIXÁ (<em>MICROPHOLIS</em> <em>VENULOSA</em>) FLANGES

Abstract

This study aimed to evaluate the bending properties of I-joist made with medium density fiber (MDF) panel web and flanges of Pinus sp., curupixá (Micropholis velunosa) and combined flanges. The tests comprised 21 beams, being 7 for each group. The join between flange and web was provided by single component polyurethane (PU) structural adhesive in 200 g m^-2. The beams were tested to determine the modulus of rupture (f_m) and modulus of elasticity (E_M) in static bending. The pinus beams showed a mean value of 6638 N mm-² for EM and 19.6 N mm-² for f_m, while curupixá beams showed values of 12190 N mm-² and 22.6 N mm-², respectively. The E_M and f_m values for composite beams were in between the figures described above, i.e. 9027 N/mm² and 20.5 N/mm². There was a significant difference for E_M among the beams with pinus flanges and curupixá flange. However, the f_m was not affected by the type of flange used. It was observed that at least 1/3 of the failure occurred between the flanges and the web joint, especially in beams made with curupixá, which prevented the beam from reaching its maximum static bending resistance. It was concluded that produced beams reached static bending values close to I-Joists, but was higher due to low compatibility between the studied tropical timber and the utilised adhesive.