Drill and laser incising of lamina for fire-resistive glulam

Abstract

Conventional glued-laminated timber (glulam) was not permitted to use to a wooden building in the fire preventive district since the amendments of the Building Standards. We already developed a one-hour fire-proof glulam made of Japanese cedar. We also succeeded to give one-hour fire performance to cross laminated timber by the same concept. The both structures are composed of three parts which are load-bearing part, fire-die-out part and surface part. The fire-die-out part is made of lamina incised by CO₂ laser and impregnated the fire retardant evenly. As the handling of CO₂ laser is not so easy for glulam manufacturer, we felt a growing need for drill incising technology. Therefore, we made pinholes of some diameters up to 2.5 mm to lamina of Japanese cedar, by a drill and investigated differences of hole position on two sides of the lamina. The maximum off-center for length and width directions was 1.8 and 3.3 mm, respectively. These off-centers are 2.3% and 41% of distances between neighboring hole on incising patterns. As the results of impregnating performance and fire-resistive performance of lamina incised by drill, significant differences were not recognized between drill incising and laser incising.

Keywords:

• Incising
• drill
• laser
• fire-resistant
• laminated timber

Acknowledgements

The authors thank Dr. Matsubara, Mr Takezawa and Mr Nakano of TIRI for taking a lot of images by their state-of-the-art equipment.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors thank Sumitomo Forestry and Forest Agency grant entitled “Promotion of CLT utilization to develop new products by new technology in 2014” for their dedicated supports. This work was supported by JSPS KAKENHI [grant numbers 22248019 and 26252024].