Prestressed fibre reinforced polymer (FRP) laminates for the strengthening of reinforced concrete structures

Abstract

Recent development in the field of strengthening has seen the application of prestressing of FRP laminate prior to bonding in order to exploit its high tensile strength. The method of prestressing the laminate induces an initial tensile strain in the concrete beams upmost fibre, thus reducing the deflection of the beam throughout the design loads. This alteration of the beams structural characteristics provides advantages in beam serviceability requirements. Structurally the beam can withstand greater ultimate loads, while yielding of internal reinforcement and cracking moments are delayed substantially, compared to unlaminated beams. Extensive experimental investigations have been undertaken by many researchers with variables ranging from anchorage type, number of laminates applied to beam, tensile reinforcement ratio and the initial prestress level of laminates before bonding. Despite the large amount of experimental data in the field, current analytical models generally employ elementary procedures in predicting beam behaviour and as a result the analytical results exhibit poor correlation with the experimental results. This implies the necessity for the development of a generic model that can accurately predict beam behaviour that will be the basis of the present study. The focus of this paper is the development of a new analytical model that can accurately predict the behaviour of an RC beam strengthened with an externally bonded (EB) prestressed fibre reinforced polymer (FRP) laminate. The model will be critically compared to an experimental database for calibration purposes then applied in a parametric study.