Glulam beam made from hydrothermally treated poplar wood with reduced moisture induced stresses

Moisture induced stresses were studied in glulam beams, which were made from hydrothermally treated poplar (Populus deltoides) wood in the current research work to understand whether the hydrothermal wood modification can reduce those stresses or not. Wood blocks with dimensions of 6 (R) × 10 (T) × 73 (L) cm3 were cut and hydrothermally treated in a stainless steel reactor at temperatures of 140 and 160 °C for a holding time of 30 min. The treated wood blocks were dried to achieve moisture content of 12%. Afterwards, the glulam beams (4-ply) were manufactured by using polyurethane (PUR) adhesive. In order to evaluate cross sectional moisture induced stresses (MISes) and bending properties of glulam beams; wood density, equilibrium moisture content (EMC) of wood, 4-point bending of the glulam beams (according to ASTM D 198-02), 3-point bending of the treated and untreated wood (according to ASTM D 143-09) and the moisture induced stresses in cross section of the glulam beams were determined. The results showed that the hydrothermal treatment reduced the cross sectional moisture induced stresses as well as relevant moisture gradients and also it caused increase of the bending strength as well as stiffness of the treated wood and the glulam beams.