Creep response of glued-laminated beam reinforced with pre-stressed sub-laminated composite

In the past decades, the use of fibre-reinforced polymer (FRP) for enhancement of strength and stiffness of wood-based structural members has been established as an economical method. New developments have been ongoing to further improve the structural performance of glued-laminate beams. Recently, a novel integral sub-laminated composite, referred to as pre-stressed FRP–wood composite laminate (PWCL), was patented (KarisAllen and Tynes, 2000 [1]). This system is comprised of pre-stressed high performance fibres, sandwiched and glued within layers of pre-compressed wood strands. The resulting sub-laminated system may be attached to the tension zone of timber/glulam beams. A concern involved with the use of such pre-stressing scheme has been the issue of creep, which could affect the long-term performance of such composite beams. This paper presents the results of a study conducted to investigate the long-term performance of glulam beams reinforced with PWCL sub-laminate. Experimental investigations were conducted to determine the creep parameters of FRP composites and wood species employed in the fabrication of PWCL. The main objective was to develop a finite element model (FEM) to simulate the pre-stressing process and to predict the creep response of an entire reinforced glulam system, including the PWCL, under an externally applied load and constant environmental condition. The FEM was constructed in the Abaqus environment and the residual stress distribution was modeled in a step-wise scheme, corresponding to each step of PWCL and beam fabrication as well as the in situ response of the composite beam. The integrity of the creep model used in the simulation was verified by the experimental results obtained from tests performed on FRP reinforced small-size wood.