Fire behaviour of CFRP-strengthened short SHS steel columns with and without insulation

Carbon Fibre Reinforced Polymers (CFRP) have been used as a potential strengthening material due to the many advantages they possess over conventional strengthening materials in recent times. Their successful applications in strengthening concrete columns have also led to CFRP being used as an external strengthening material in steel columns. However, the lack of knowledge of the fire performance characteristics of CFRP has hindered the CFRP usage in steel columns, which require structural fire ratings. Therefore, this two phase experimental investigation was aimed at investigating the effect of fire on the structural performance of CFRP strengthened short Square Hollow Section (SHS) steel columns. In the first phase, CFRP strengthened short SHS columns were exposed to steady state fire conditions and tested under axial compression until failure. The test results exhibited a severe degradation of the ultimate axial compression capacity beyond the glass transition temperature of the adhesive (66°C) and showed that the effect of CFRP has diminished completely at 225°C. In the second phase, CFRP strengthened short SHS columns were insulated with a spray applied insulation material and exposed to standard fire under three load conditions. The standard fire test results showed that the CFRP strengthened and insulated columns were able to achieve more than 60 min of fire rating under 0.2 load ratio suggesting satisfactory fire resistance level. This paper presents the details of the investigation and its results.