APPLICABILITY OF LOW GRADED GLUED LAMINATED BEAM TO JAPANESE CONVENTIONAL HOUSE

摘要

For many years, we have been studying the safety margin of structural members of Japanese conventional houses. We have found that columns and beams possess sufficient safety margins for allowable stresses with some exceptions, even for houses located in an area with heavy snowfall.Japan has been importing huge quantities of wood from overseas for several decades, but the stability of imports is being threatened gradually as other countries change policy and due to the great increase in wood demand in developing countries. For example, Russia decided to tax the export of logs. This decision has been suspended for softwood, but the suspension could be cancelled in the near future. This would have a major impact on Japanese companies and the amount of softwood logs imported from Russia had decreased very sharply. Many Japanese companies are therefore shifting to domestic woods such as Japanese cedar and developing reliable supply routes. Although these logs are cheap, Japanese cedar does not have good physical properties. These are the driving forces affecting the structural member market in Japan.This research examined the structural safety margin of beams for Japanese conventional houses assuming that the beams are replaced with glued laminated beams of grade E55-F200 in the Japanese Agricultural Standard (JAS). This grade was added when JAS was updated in 2007; it is the lowest grade for products using the lowest elasticity of lamina made from Japanese cedar.