Effects of long-term loading on Moabi wood beams in the tropical environment of Gabon: variability in properties and effects of exposure conditions on mechanical properties in 3-point bending tests

Abstract

This work is devoted to 3-point bending tests performed on tropical specimens of Moabi (Baillonella toxisperma) from Gabon. The beams are formerly subjected to long-term loading in three media (air-conditioned, unsheltered and sheltered outdoor) in a tropical environment. The beams were sawn into nine 340 mm long sections and subdivided into three sections in the vertical direction (top section, middle section and bottom section). From each section, two specimens were extracted for the bending test, two for the tensile test and four for the compression test. In the present study, 81 bending specimens with a cross-section of 15 x 15 mm2 and a length of 300 mm were used. The tests for the determination of the local modulus of elasticity and failure strength in bending were carried out according with NF EN 408. The results obtained show a strong influence of time and exposure environments on the mechanical parameters (bending strength and modulus of elasticity). There is also a strong variability of these mechanical parameters along the length of the beams with a clear correlation between the sampling areas and the level of exposure; this confirms quite well the level of complexity of the wood material.