PSI - Issue 81

Victor Datsiuk et al. / Procedia Structural Integrity 81 (2026) 73–77

75

Fig. 1. Testing of an experimental beam

3. Results and discussion Based on the results of the conducted experimental tests, the ultimate bearing capacity of bending timber beams that had been in long-term service under different moisture content levels was determined. The obtained results are presented in the form of averaged values, which makes it possible to eliminate the influence of random deviations and to ensure the representativeness of the experimental data. The results were generalized taking into account the service life of the elements, the actual temperature humidity conditions, and the nature of their behaviour under loading. This approach provides a basis for a comparative analysis of the influence of service duration and timber moisture content on the bearing capacity of the beams (Table 2).

Table 2. Results of experimental tests of timber beams after long-term service

Moisture content W, %

Number of specimens n, pcs

Ultimate bearing capacity F u , kN

Specimen No.

Service life T, years

1 2 3 4 5 6

25 50 75 25 50 75

12 12 12 15 15 15

2 2 2 2 2 2

14.7 14.0 13.5 12.8 12.1 11.2

According to the experimental results, the averaged ultimate bearing capacity of pine beams was established (Table 2). For a service life of 25, 50, and 75 years at a moisture content of 12%, the ultimate bearing capacity was 14.7 kN, 14.0 kN, and 13.5 kN, respectively. At a moisture content of 15%, the corresponding values were 12.8 kN, 12.1 kN, and 11.2 kN. An analysis of the experimental data indicates that at a moisture content of 12%, the bearing capacity of bending elements after 75 years of service is approximately 1.09 times lower than that of beams operated for 25 years. At a moisture content of 15%, the reduction in bearing capacity over the same service period reaches approximately 1.17 times. These results confirm the significant influence of both long-term service and operational moisture conditions on the load-bearing performance of timber beams. The failure mode of an experimental beam after long-term service is shown in Fig. 2.