Experimental and numerical evaluation of the compression behaviour of GFRP-wrapped infill materials

Glass Fibre Reinforced Polymer (GFRP) composite wrap has become an effective repair system for deteriorated structural columns. It is essential to provide an infill material in the gap between the retrofitted column and the GFRP wrap. So, the properties of the infill material can significantly influence the contribution of these wraps and thus, can affect the overall performance of the retrofitted structure. However, the research on the effect of GFRP confinement on infill materials with various properties is still limited. This study explores the effectiveness of the GFRP wrapping system and its contribution to the axial compression behaviour of concrete, grout and epoxy infill materials. A total of 18 unconfined and GFRP-wrapped cylindrical columns were cast and tested under concentric axial compression loading. A finite element (FE) modelling was implemented using ABAQUS software to analyse the compression behaviour of GFRP-wrapped infill materials. The experimental results demonstrated that the confinement effect of the GFRP wrapping system is highly influenced by the properties of the infill material. The compressive strength and modulus of elasticity significantly increased due to GFRP wrapping by 149% and 77%, respectively for concrete infill, and by 40 % and 72 %, respectively for grout infill whereas negligible confinement efficiency observed in wrapped epoxy infill. The FE analyses showed a good correlation with the experimental results in predicting the overall compressive behaviour of the various infill materials. This study demonstrates valuable insights on the confinement effect of GFRP wraps in the repair of columns involving infill materials which therefore could be employed to better understand the overall behaviour of columns retrofitted with GFRP wrapping systems.