Timber Strength Grading as Necessary Basis for Structural Design in Ex-YU Region

Abstract

Classification of timber for various commercial purposes is essential for its proper application in order to ensure the reliability and economic use. Visual grading of structural timber is commonly used in a number of EU countries, with different grading national standards optimized for locally available wood. Countries in the ex-YU region are traditional partners in wood trade and had the same standards for visual grading, but in most of the regions these standards are not completely compliant with EN requirements. Consequently, that leads to the fact that the most of regionally available structural timber is not assigned into strength classes, which is the starting point for the limit-state concept in design of timber structures. The aim of this paper is to emphasize the lack of strength classification of structural timber in the ex-YU region, which is a prerequisite for the design of timber structures made by civil engineers. Based on an overview of visual classification types with regional experience in grading, relevant EN standards, and differences in design concepts with possible consequences of grading approach, it can be concluded that “quality” grades and “strength” classes are not easily comparable.