A research of stress/strain condition of reinforced timber structures with natural weakenings

Abstract

In recent decades building structures are faced with more serious demands in a broad sense of this term, but in this case the lumber quality is gradually lowered due to large volumes of consummation along with sufficient time, needed to reproduce a stock lumber. As a result, there is a need for a more detailed and in-depth study of the influence of low-grade wood defects on the work of wooden structures. One of the methods to improve characteristics of structures, made with low-grade lumber is a reinforcement of these. The objective of the research below is to determine a degree of influence of a cross-sectional natural weakenings (such as knots) to a stress/strain condition of reinforced timber beams. The main research methods are as follows: mathematical calculations, computer modeling in the software "Cosmos/M" and an experiment. The methodic of an experiment planning is based on the "Latin Squares" principle [1]. The square is designed for three primary factors, each of which consists of three variants. The results of the research work are shown in form of graphs and tables. The main conclusions made after the research: the deformation of the reinforced beams is from 15 to 20% lower, as compared with non-reinforced; crushing of reinforced beams with weakened cross-section takes place without a sharp state of a former because of a supporting influence of reinforcement in tensioned zone and reliable connection of reinforcement with wood, which is ensured by a glued joint until the crushing of the timber. The safety factor of reinforced timber structures varies from 3 to 5.07.