Abstract
This paper presents the study on structural behaviour of glulam beams pre-stressed 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 pre-stressing process, all beams were placed in a chamber with Relative Humidity (RH) fluctuated between 40% until 80% and a constant temperature of 20⁰C until the maximum swelling of the CW block was reached. The glulam beams with the size of 3800 mm long, 200 mm deep and 120 mm wide were reinforced by 3, 5, 7 CW blocks respectively, all with the same thickness of 45 mm. In addition, there were two beams which were reinforced at the bottom extreme fibre with one lamella made of compressed wood. There were also three beams without any reinforcement for control purpose. 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.
Highlights
Glued-laminated timber or glulam have been used in Europe since the end of the 19th century (Andre 2006)
This paper aims to investigate how the moisture dependent swelling of the compressed wood, which was inserted in a pre-cut hole on the top of beam, could enhance the structural performance of a glulam beam reinforced
The beam reinforced by seven 45mm thick compressed wood (CW) blocks and a CW lamella at the bottom layer has the highest stiffness of 1032 kN/m, which is a 45.81% increase in comparison to the beam without any CW reinforcement
Summary
Glued-laminated timber or glulam have been used in Europe since the end of the 19th century (Andre 2006). Glulam timber is made of wood laminations glued together to form a specific piece of wood for a specific load. Reinforcement of structural wood products has been studied for more than 40 years. Research on glulam beams reinforced with fiber and fiberreinforced polymers (FRP), such as carbon, aramid and glass fibres 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. Nikolaos and Thanasis (1992) studied the effect of reinforcing fir wood with carbon/epoxy fiber-reinforced plastics (CFRP). 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
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