Compressive strength of spruce glulam

Tests on glulam were simulated to determine the compressive strength. Based on the values obtained, three strength models were derived. They describe the compressive strength in terms of the density of the sawn timber used, the moisture content of the glulam and, optionally, of the knot area ratio. One of the models, based on density and moisture content, provides satisfying accuracy for engineering applications. Accordingly, glulam with 12 % moisture content has a predicted strength which is 50 % higher compared to glulam with 20 %. If the moisture content amounts to 20 % and the characteristic density of the sawn timber exceeds 350 kg/m³, the predicted strength is lower compared to corresponding nominal values in current product standards. It is suggested to separate the compressive strength for glulam with a maximum moisture content of 12 % which corresponds to service class 1 and of 20 % for service class 2. By this, significantly higher strength values could be used for compression members in service class 1.