Ultrasonic technique for evaluation of bio-defects in wood: Part 2 - In situ and in vitro analyses of old beams using ultrasonic and bending tests.

摘要

Heads of 17 markedly bio-damaged fir beams, proposed for replacement in historical ceilings, were subjected to in situ and in vitro analyses. At in situ tests, average velocities of ultrasonic wave (UW) in transverse directions c (height and width) were significantly lower in parts 0.1-0.2 m off the ends (300-400 m s-1) than in those 0.5-1.0 m off the ends (700-1100 m s-1). Average velocities of UW in longitudinal direction c reached 1875-5598 m s-1. At in vitro tests, tight linear correlations between densities, dynamic MOE_d (determined by ultrasonic), static MOE and MOR (determined by bending) were observed for 153 specimens prepared from the beams. In vitro parameters MOE_d, MOE and MOR corresponded well with in situ ultrasonic parameter c. Relations between in situ and in vitro results could help better evaluate bio-defects in historical timber structures.