CICE 2010 - The 5th International Conference on FRP Composites in Civil Engineering September 27-29, 2010 Beijing, China Performance Evaluation of SFRP-Confined Circular Concrete Columns Mohammad A. Mashrik, Raafat El-Hacha (relhacha@ucalgary.ca ) & Khoa Tran Department of Civil Engineering, University of Calgary, Calgary, Alberta, Canada ABSTRACT: This paper presents the results of an experimental investigation that evaluates the effectiveness of using Steel Fibre Reinforced Polymer (SFRP) sheets to confine small-scale plain concrete circular col- umns. Different parameters were investigated including: number of SFRP layers (1, 2, and 3) and concrete compressive strength (25, 30, and 35 MPa). A total of thirty-five circular specimens (150 mm diameter × 300 mm height) were tested and divided into three groups according to concrete compressive strength. In each group, two/three specimens were tested without wrapping for comparison purposes, and two/three specimens for each number of layers. The specimens were tested under monotonic concentric uni-axial compressive load. Results showed that SFRP confinement improved the performance of the concrete cylinders in terms of axial strength, stress-strain behaviour, and ductility. 1 INTRODUCTION Deterioration of concrete structures due to aging, weathering, overloading, design or construction de- fects, seismic activity, poor maintenance etc is a sig- nificant problem all around the world. The cost of replacing the deteriorated structures is prohibitive. In this regard, Fibre Reinforced Polymer (FRP) sheets can provide an economic and efficient solu- tion to repair and rehabilitate the deteriorated struc- tures. FRP sheets can be bonded onto flexural mem- bers to increase flexural and shear capacity, or wrapped around the axial members (columns) to im- prove axial strength and ductility (El-Hacha et al., 2010). Recently, Steel Fibre Reinforced Polymer (SFRP) sheets have been introduced as an alterna- tive to more conventional Carbon and Glass Fibre Reinforced Polymer (CFRP and GFRP) sheets. SFRP sheets are advantageous over CFRP or GFRP sheets in a way that the steel cords that make up the SFRP sheets have some inherent ductility (Min- naugh, 2006). The behaviour of small-scale circular plain concrete columns wrapped with SFRP sheets, is the focus of this paper. 2 OBJECTIVE The main objective of this study is to investigate the effectiveness of using SFRP sheets to confine small- scale plain concrete circular columns. 3 EXPERIMENTAL PROGRAM 3.1 Test Specimens The experimental program involved testing 35 circu- lar plain concrete columns (150 mm diameter by 300 mm height) under monotonic concentric uni-axial compressive load until the ultimate strength of con- crete and SFRP sheets was reached. 3.2 Materials 3.2.1 Concrete Three types (based on concrete compressive strength) of ready mix Portland cement concrete was used to cast the cylinders. The target compressive strengths at 28 days were 25, 30, and 35 MPa. 3.2.2 Strengthening Materials Steel Fibre Reinforced Polymer (SFRP) sheet was used to wrap the concrete cylinders using epoxy ad- hesive. The SFRP sheet is made of unidirectional brass coated ultra high strength twisted steel wires forming cords that are assembled into a sheet that can be impregnated using various resin systems. The SFRP wraps used to strengthen the specimens in this project were Hardwire type 3×2-20 manufactured by Hardwire LLC. The thickness of the sheet was 1.23 mm giving net area per width 0.38 mm 2 /mm. The ulti- mate tensile strength and effective Modulus for the