Експериментальні дослідження міцності дерев’яних клеєних балок з вадами деревини

Abstract

The article investigates the influence of natural wood defects and imperfections in finger joints on the strength and modulus of elasticity of glued laminated timber beams of the strength class C24 (KVH). The relevance of the topic is due to the widespread use of such beams in modern construction as environmentally friendly, energy-efficient and durable load-bearing structures. The aim of the work was to determine the actual strength characteristics of KVH beams made of spruce wood at the production facilities of Milwood LLC, to evaluate the effectiveness of the current technological process, and to develop practical recommendations for its improvement.The results of experimental tests of ten glued laminated timber beams samples for bending and determining the modulus of elasticity showed that, despite the generally high average strength values, there is significant variability in the results obtained. The coefficient of variation of the elastic modulus exceeded 10%, and the coefficient of variation of bending strength reached about 12%.It has been established that the most critical defects leading to premature destruction of beams are the presence of knots (especially in the tension zone), the emergence of the core on the surface of the lumber, as well as insufficient gluing quality at the dowel joints. These factors often cause delamination or detachment along the glue joint, which significantly reduces the load-bearing capacity of the structure. In most cases, the onset of destruction of the glued laminated timber beams was observed precisely in areas with a concentration of defects or violations of the technological parameters of gluing.The obtained results confirm the need to strengthen the quality control system for raw wood and production processes. In particular, it is recommended to improve the procedures for visual sorting of sawn timber, optimize cross-cutting to reduce the number of knots in critical areas, and improve the technology of glue application and the formation of adhesive joints between elements. The implementation of these measures will contribute to improving the uniformity of mechanical properties, reliability and durability of glued wooden structures.