Fundamental study on detecting internal defect of timber due to termite and its mechanical improvement with resin

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Abstract

In Japan, wood has been used for many years as a building material. On the other hand, wet condition is the strongest factor to promote degradation of wood, and it may cause corrosion and damage to termite and so on. These biological decompositions proceed more rapidly than ultraviolet deterioration and there exists a significant fatal deterioration due to remarkable strength drop. Especially for valuable timber buildings that have existed since long ago, it is essential to achieve a permanent maintenance of the building by diagnosing the decrease of strength due to deterioration. However, except for important cultural assets, assessment of the durability of Japanese cultural heritage buildings is often entrusted to local public entities, and evaluation criteria detected by visual investigation is sometimes not accurate. In addition, when deterioration progresses only in the inside of wood, it is difficult to judge deterioration visually from outside, and, at present, a sufficient diagnostic method has not been studied. Furthermore, it is common that the restoration and refurbishment method currently implemented for the biodegradation of wooden buildings is to remove degraded parts and partially replace with new healthy wood. It is desirable to reinforce the original part as it is to restore the strength, but it has not been put into practical use yet. In this study, a basic experiment was carried out with the aim of proposing a member that was internally deteriorated due to termite's damage. Quantitative evaluation of this damage degree was proposed and the effect of reinforcing the inside part with resin and its non-destructive evaluation were verified. The findings obtained in this study are shown below. Detection of the internal deterioration of the artificial drilled degradation by the ultrasonic method was able to perform at about 30% of the defect by volume. Although it was difficult to detect the defect of about 10% by volume by the ultra-sonic method, the compressive strength is not markedly decreased. On the other hands, the clear reduction of the strength was observed at the rate of 30% defect the and the ultrasonic method successfully detected the pulse change. In addition, the strength improvement by filling resin was performed and the ultrasonic method successfully evaluated the defect. The relationship between the propagation velocity ratio by the ultrasonic method and the mass ratio was high. Similar results were obtained in the case of the deterioration by termites. Hence, the internal deterioration can be detected by the ultrasonic method. Meanwhile, improvement of the strength by resin filling was also increased the velocity of pulse of the ultrasonic. This might indicate that the strength improvement effect by the resin filling could be evaluated by ultrasonic method. Similar to the compression test with the reinforcement by resin filling, bending Young's modulus and bending load were partially improved and the effect could be evaluated by the ultrasonic surface method. In the future, as a practical research, authors will examine current improvement effect of bending strength, construction method such as resin selection and resin injection method. In addition, quantitative evaluation of resin filling degree and reinforcing effect by the ultrasonic wave propagation speed are considered to be necessary.

Original languageEnglish
Pages (from-to)321-329
Number of pages9
JournalJournal of Structural and Construction Engineering
Volume84
Issue number757
DOIs
Publication statusPublished - Mar 2019

Keywords

  • Internal degradation
  • Reinforcement
  • Resin filling
  • Ultrasonic wave propagation velocity
  • Wooden Building

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