EXPLORE NOVEL WAYS TO STRENGTHEN GLULAM BEAMS BY USING COMPRESSED JAPANESE CEDAR Buan Anshari 1 , Zhongwei Guan 2 , Kohei Komatsu 3 , Akihisa Kitamori 4 , Kiho Jung 5 ABSTRACT: This paper presents the study on structural behaviour of glue-laminated (glulam) timber beams reinforced by compressed wood (CW) in terms of load carrying capacity, strength and stiffness. Glulam beams were strengthened by inserting CW blocks into the pre-cut rectangular holes on the top of the beams. This practice was to make use of moisture-dependent swelling nature of the compressed wood. The CW block was placed in a way in which its radial direction was coincident with the longitudinal direction of the beam to be strengthened. After reinforcement process, all beams were put in chamber with Relative Humidity (RH) fluctuated between 40% until 80% and a constant temperature of 20 0 C until the maximum swelling of the CW block was reached. The test results showed that a pre- camber was produced in the mid-span of the beam reinforced. At both the top and the bottom extreme fibres of the beam significant initial tensile and compressive stresses were generated respectively. Bending tests indicated that the load carrying capacity of the reinforced beams increased significantly in comparison to the beam without reinforcement. KEYWORDS: glulam, compressed wood, moisture-dependent swelling, pre-stressing, pre-camber 1 INTRODUCTION Glued-laminated timbers or glulam have been used in Europe since the end of the 19th century. Glulam timbers are made of wood laminations glued together to form a specific piece of wood for a specific load. The interest to use this technology is to decrease product variability and make it less affected by natural growth characteristics like knots. Besides, the glulam technology offers almost unlimited possibilities of shape and design for construction, and is widely used for load bearing structures in houses, warehouses, pedestrian bridges, etc. 1 Buan Anshari, Research Student, Department of Engineering, University of Liverpool, Brownlow Street, L69 3GQ, Liverpool, U.K. Email: Buan.Anshari@liv.ac.uk 2 Zhongwei Guan, Senior Lecturer, Department of Engineering, University of Liverpool, Brownlow Street, L69 3GQ, Liverpool, U.K., Email: Zhongwei.Guan@liv.ac.uk 3 Kohei Komatsu, Professor, Laboratory of Structural Function, Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan Email: kkomatsu@rish.kyoto-u.ac.jp 4 Akihisa Kitamori, Assist. Professor, Laboratory of Structural Function, Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan Email: kitamori@rish.kyoto-u.ac.jp 5 Kiho Jung, Mission Researcher, Laboratory of Structural Function, Research Institute for Sustainable Humanosphere, Kyoto University, Uji, Kyoto 611-0011, Japan Email: jungkiho@rish.kyoto-u.ac.jp Theirs applications on high load constructions are still limited due to lower bending strength and stiffness, high costs, durability and maintenance drawbacks compared to concrete and steel structures. However, wood as a natural material will become a more competitive building material in the future due to its environmentally friendly and aesthetic aspects [1], also more advanced reinforcing techniques. Reinforcement of structural wood products has been studied for more than 40 years. In the earlier stages of the research, the focus was mainly on using metallic reinforcement, including steel bars, pre-stressed stranded cables and bonded steel and aluminium plates. Recently, research on glulam beams reinforced with fiber and fiber-reinforced polymers (FRP) has been increased significantly, due to the high specific strength and stiffness of the FRP materials. Many attempts have been conducted to reinforce wood or glulam timber beam by using fibre reinforced plastics. Plevris and Triantafillou [2] studied the effect of reinforcing fir wood with carbon/epoxy fiber-reinforced plastics (CFRP). The study revealed that even very small area fractions of fiber-composite reinforcement resulted in significant improvement of the member’s mechanical behaviour. Triantifillou and Deskovic [3] also studied the effect of prestressed CFRP reinforcement bonded to European beech lumber. The method used in this study involved external bonding of pretensioned FRP sheets on the tension faces of beams through the use of epoxy adhesives. Borri et al. [4] discussed the use of FRP