Development of One-hour Fire-resistive Building Materials Made of Combustible Japanese Cedar Using Laser Incising

Abstract

Conventional glued-laminated timber (glulam) was not permitted any more to be applied to a wooden building in the fire preventive district since the amendments of the Building Standard Law in 2000. The Japanese Government set the self-sufficiency rate of the domestic wood supply at 50% within ten years in 2011 and enacted the new legislation to promote wooden structures and wooden interior decorations in public buildings as long as possible. Therefore, it is strongly desired to develop fireproof structural materials usable in urban area to achieve goals. Therefore, one-hour fireproof glued-laminated timber (glulam) and cross laminated timber (CLT) were developed made of Japanese cedar (Cryptomeria japonica D. Don) which is the major species in Japan and combustible by incision to fire-die-out part of lamina with CO2 laser. The structure in cross-section of the glulam consists of three zones, namely, load-bearing part (untreated glulam), fire-die-out part impregnated fire-retardant chemicals and surface part (untreated lamina). An one-hour fire-resistive CLT was also developed using the same concept as the glulam and its performance was confirmed by the fire-resistance test. The first wooden building whose main structural members were made of the fireproof glulam marketed as FR wood® was also introduced briefly.