INFLUENCE OF ANNUAL GROWTH RING STRUCTURE REGULARITIES AND NATURAL DEFECTS ON PHYSICAL AND MECHANICAL PROPERTIES OF CARPATHIAN SPRUCE

Abstract

In the process of technical inspection of buildings and structures constructed with the use of both solid logs and Carpathian spruce lumber massively observed processes of deplanation of the wall fence, exit from functional state of constructive elements of inter-storey floors and rafter systems. During inspection calculations of existing construction elements, which are in exploitation for all types of stress-deformed state, there are often questions to the accepted constructive solutions of cross-sections and nodal joints of building structures made of solid wood. This fact can only be due to the discrepancy between the strength and deformation properties of Carpathian spruce and the declared characteristics in normative documents. The presence of natural defects and structural features of the Carpathian spruce structure indicate that the unequal physical and mechanical properties of the two coniferous species that grow in the northern latitudes and the Carpathian region of Ukraine are not entirely true. The distribution of the ratio of latewood to earlywood has a direct influence on the physical and mechanical properties of wood. This fact is caused by rather cellular structure of wood with large annual growth of early and late wood. Such characteristics can have both positive and negative effects on the properties of Carpathian spruce as a building material. This type of wood with a high degree of natural moisture content and cellular structure requires a special pre-drying procedure for the production of building structures. To establish the factual physic-mechanical properties of Carpathian spruce, the current normative documents were analysed and the existing scientific research on this issue was studied. In the process of conducting a comparative analysis of the results of comprehensive studies of standard samples of Carpathian spruce for compression along the fibres and control samples made from the base species - pine, the fact of partial inconsistency of physical and mechanical parameters of the two varieties of conifers was established. In general view, recommendations are made for changes to the current norms for the construction of solid timber structures. Keywords: : physic-mechanical properties, bulk weight, wood defects, temporary resistance.