Flexural behaviour of circular timber columns strengthened by glass fibre reinforced polymer wrapping system

Prefabricated glass fibre reinforced polymer (GFRP) wrapping systems have been established as an attractive retrofitting technique for structural columns in various applications. Further exploration is needed to evaluate their contribution to the flexural performance of timber columns due to their inevitable exposure to bending under different loads, such as wave actions, wind, and earthquake, among the others. This study investigates the contribution of GFRP wrapping systems to the capacity of timber columns tested under three-point bending. Eight unwrapped and GFRP-wrapped circular timber columns with annular space filled by grout or epoxy ma-terials were tested. The inclusion of carbon FRP (CFRP) straps within the epoxy infill was also investigated. The flexural load-midspan deflection, longitudinal strain responses, and failure modes were carefully studied. Finite element modelling (FEM) and theoretical analyses were performed and compared with the experimental results. The results revealed that GFRP-wrapped columns with epoxy infills exhibited a significant increase in flexural capacity by up to 95% compared with unwrapped columns. The results also showed that the provision of epoxy infill along with CFRP straps within the wrapping system can substantially improve the energy absorption of timber columns whilst, those with grout infills revealed a remarkable increase in ductility compared with unwrapped columns. The results predicted by FEM and theoretical analyses were in good agreement with ex-periments. This study demonstrated that the studied GFRP wrapping system is an adequate strengthening technique that can improve the flexural performance of circular timber columns.

Automated summary

Prefabricated glass fibre reinforced polymer (GFRP) wrapping systems have been established as an attractive retrofitting technique for structural columns. This study focuses on the contribution of GFRP wrapping systems to the flexural performance of timber columns and finds that columns wrapped with epoxy infills exhibit a significant increase in flexural capacity, while those with grout infills show improved ductility.