Circular and square columns strengthened with FRCM under concentric load

Fiber-reinforced cementitious matrix (FRCM) systems have recently emerged as an innovative technique to strengthen and retrofit reinforced concrete structures. These non-corrosive systems involve the use of high strength reinforcing textiles sandwiched between layers of cementitious mortars. This paper aims to study the effect of retrofitting newly constructed short columns with FRCM using PBO type of textiles. The experimental program consisted of testing 4 rectangular columns and 4 circular columns under concentric loading. All columns had a reinforcement ratio of 0.02 and were cast with concrete of 30 MPa compressive strength. For each type of cross-section, columns were wrapped with 1, 2 or 4 layers of PBO FRCM. Overall, the strengthened columns exhibited higher load carrying capacity than their control unwrapped counterpart with an increase ranged between 5.1% and 36%. The confining effect of FRCM layers was more pronounced in the circular columns than in the square ones. It was also noticed that all columns exhibited similar responses in terms of load -strain relationship irrespective of the column shape and the number of FRCM layers used. Furthermore, the displacement levels increased as the number of layers increased which indicated an increase in ductility of columns wrapped with FRCM.