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

The use of prefabricated glass fibre reinforced polymer (GFRP) wrapping systems in retrofitting reinforced concrete (RC) columns has emerged to enhance the overall axial performance. However, the effect of these systems on columns subjected to bending is still limited although the flexural loading on columns in real life is inevitable. This paper presents experimental, numerical, and theoretical investigations on the flexural behaviour of circular RC columns strengthened by a GFRP wrapping system. A total of eight columns were prepared and tested under three point bending to determine the contribution of the GFRP wrapping system to the overall flexural performance. The annulus between the RC columns and the GFRP wraps was filled with epoxy or cementitious grout to ensure transfer and distribution of stresses. The load-midspan deflection responses and failure modes were presented and evaluated. Furthermore, a nonlinear finite element modelling (FEM) was conducted using ABAQUS software to simulate the performance of unwrapped and GFRP-wrapped columns under flexural loading. A theoretical analysis was also developed using the basic beam theory to obtain the flexural capacity of the tested columns and compare it with experimental and FEM results. A parametric analysis was carried out to assess the effect of varying the thickness of GFRP and infill, as well as the loading mode, on the flexural behaviour of RC columns. The results of experimental tests demonstrated that GFRP-wrapped columns with epoxy infills significantly enhanced the flexural load capacity whereas columns with grout infills showed a prominent enhancement in ductility and energy absorption. The results of FEM and theoretical analyses were in good agreement with experimental results. The results of the developed theoretical model were found to have a good correlation with the results of the parametric investigation. Overall, the GFRP wrapping system imple-mented in this study is an effective repair technique for structural RC columns subjected to flexural loading. The proposed theoretical model can be used by the practising engineers to design a composite repair system for deteriorated reinforced concrete columns.

Automated summary

This paper presents experimental, numerical, and theoretical investigations on the flexural behaviour of circular RC columns strengthened by a GFRP wrapping system. The results demonstrate that the GFRP wrapping system significantly enhances the flexural load capacity and ductility of the columns.