Fixed–fixed flexural vibration testing method of actual-size bars for timber guardrails

Abstract

Resonance frequencies of bars with various types of end supports were examined in terms of flexural vibration. Sugi (Japanese cedar, Cryptomeria japonica D. Don) was used for the specimens. Small rectangular bars with dimensions of 25 mm (R) × 5 mm (T) × 300 mm (L), small round bars of 25 mm in diameter and 250 mm in length, actual-size rectangular bars with the dimensions of 45 mm (R) × 95 mm (T) × 1500 mm (L) and actual-size round bars of 180 mm in diameter and 2000 mm in length were made. Varying compression stress was applied to the parts around both ends of test specimen, whereupon flexural vibration tests were performed. The measured resonance frequency rose rapidly early in the increasing compression load process and was nearly stable for the larger compression load. The significant increases in the resonance frequency for round bars are thought to be derived from the wide area between the round bar and jig. It is necessary to compare the resonance frequency of a bar tightly fixed to a post with that of the same bar loosely fixed to the post.