Experimental investigations of fire-damaged RC columns retrofitted with CFRP or steel jackets

Abstract

Due to the increasing number of high-rise buildings and long-span bridges, high strength concrete (HSC) has been widely used in the infrastructures. Therefore, HSC occupies the same large amount of share in the construction market as normal strength concrete (NSC). In general, fire-exposed reinforced concrete (RC) structure leads to serious structural problems due to the loss of strength and stiffness for both concrete and steel bars. Carbon fiber reinforced polymer composites (CFRP) and steel jacketing are two common methods applied to strengthen RC structure columns. Therefore, it is valued to investigate the structural behavior of fire exposed and retrofitted RC columns with CFRP and steel jackets. This paper presents the compressive behavior of RC columns exposed to ISO834 standard fire for 2 h, cooled by air and retrofitted with CFRP and steel jackets. Total 8 RC columns (ϕ300 × 1000 mm) with two different concrete strength, normal and high, were tested. Cross-sectional temperature distribution, load-deflection response were investigated in this studied. It was observed that, temperature gradient was developed in each specimen during fire exposure. HSC columns were more susceptible to spall off compared with NSC columns. CFRP and steel jacket can effectively improve the ultimate capacity and the stiffness for fire damaged RC columns. Repaired fire-damaged RC columns with removing loose concrete has large impact on the stiffness improvement for NSC columns.