Analysis of prestressed fibre-reinforced concrete beams

Abstract

This paper presents the test results of 12 partially prestressed concrete flexural beams reinforced with steel fibres that failed in flexure over partial or full depth. The variables considered were strength grades of concrete (35, 65 and 85 MPa) and the presence of steel fibres in the cross-section of the beam (web, flange or full depth). Three-dimensional finite element analysis of the prestressed beams was carried out to assess the non-linear behaviour of concrete, for example post-peak softening, concrete cracking strain softening, tension stiffening, bond-slip and yielding of reinforcement. Also, the effects of the addition of steel fibres in the concrete (increase in tensile strength and control of crack width due to the bridging of fibres across the crack interface) were modelled. The bond-slip behaviour of longitudinal reinforcements (steel fibres, prestressing wire and deformed bars) was accounted for to capture the structural stiffness of the concrete beam accurately. The effects of steel fibres in the concrete beam section over partial or full depth were also modelled. All prestressed beams were analysed using Ansys. Load–deflection responses and cracks in the prestressed concrete beams were predicted and compared with experimental results. The predicted results were found to be in good agreement with the corresponding test results. The analytical model predicted crack patterns in the concrete quite accurately.