Strengthening fire-damaged concrete by confinement with fibre-reinforced polymer wraps

Extensive research has shown that fibre-reinforced polymer (FRP) wraps are very effective for strengthening concrete columns for increased axial and flexural load and deformation capacity, and this technique is now widely used around the world. The study reported in this paper extends the FRP confinement technique to strengthening fire-damaged circular concrete columns. An experimental programme was undertaken to study the compressive strength and stress–strain behaviour of both unconfined and FRP-confined plain concrete cylinders after being heated to various elevated temperatures for up to four hours and cooled to room temperature. The results show that FRP confinement is highly effective for enhancing the load-carrying capacity of even severely fire-damaged concrete columns. The results also yield insights into the mechanics of FRP confinement of concretes of similar composition but with varying compressive strengths. A modified version of a pre-existing confinement model is proposed for use in designing FRP strengthening schemes for fire-damaged concrete columns.

► Fire-damaged circular concrete columns strengthened with FRP are tested.
► FRP is very effective for enhancing the strength of fire-damaged concrete columns.
► The strength increase due to FRP is independent of the unconfined concrete strength.
► This is also true for the axial strain enhancement due to FRP wrapping.
► A confinement model for FRP strengthening of fire-damaged concrete columns is given.