RIGIDITY OF SOLID-SECTION WOODEN BEAMS AFTER LONG-TERM USE

Abstract

Wood is one of the most widely used construction materials for manufacturing load-bearing roof structures. Therefore, it is important to understand the behavior of wood after long-term service, including the effect of moisture on its performance. Within the scope of the experimental study, twelve beams were manufactured from solid wood that had been in long-term service. These beams were divided into six different series. The first, second, and third series were made from wood with a moisture content of 12%, while the fourth, fifth, and sixth series were made from wood with a moisture content of 15%. The age of the wood ranged from 25 to 75 years. Based on the test results, graphs showing the relationship between deflections and loads were obtained. Using the average deflection values for each beam series, the load-bearing capacity of the beams was determined according to the second group of limit states. As a result of the experiments, new data were obtained on the relationship between the stiffness of beams made from wood that had been in long-term service, with different moisture contents, and loads. Graphs of deflection versus loading were constructed.The load values of the beams for the second group of limit states, which correspond to the limit deflection of 10 mm, were determined. Thus, for beams of series 1–3 with a humidity of 12%, they were within 3.9–4.2 kN, for beams of series 4–6 with a humidity of 15%, they were within 3.0–3.4 kN. It was established that an increase in the humidity of the beams from 12% to15% leads to an increase in deflection regardless of the duration of wood use.The obtained data indicate a certain dependence between the values of deflections and wood moisture content. This  dependence is manifested in the form of an increase in deflections with an increase in wood moisture content. No regularities regarding the influence of wood age on their stiffness were observed in the experimental samples.