Fixed-fixed flexural vibration testing method of beams for timber guardrails

Resonance frequencies of beams with various types of end supports were examined for flexural vibration. Rectangular beams with dimensions of 300 (L) × 25 (R) × 5 or 10mm (T) were used as the test specimens. Various compressing stresses were applied to the parts around both ends of a test beam and flexural vibration tests were conducted. The measured resonance frequency started to increase from the resonance frequency of a beam with simply supported ends and was stable around the resonance frequency of a beam with fixed ends as the compressing stress increased. The stable resonance frequency was lower than the theoretical value because perfect fixation of a beam to a post was difficult. From these results, the temporal change in resonance frequency itself, rather than the stable resonance frequency, is effective to examine whether a beam has enough strength as a guardrail.