Flexural reinforcement with FRP systems - experimental results vs. Expected results based on actual design guidelines

Abstract

Due to the specific characteristics of the fibre reinforced polymers (FRP), the structural behaviour of concrete elements reinforced by FRP systems as well as to other questions related to the use of the externally bonded reinforcement (EBR) technique, it is necessary to respect specific rules on the application of these systems to reinforce concrete elements. Actually, some recent manuals were published with the main objective of providing design guidelines for the use of FRP reinforcement in accordance with the actual design format for concrete structures such as American Concrete Institute Committee 440, CEB-FIB Task Group 9.3 and ISIS Canada Network of Centres of Excellence. The objective of this work is to appraise the suggested methodologies of the design manuals for the new strengthening technique by external bond of unidirectional FRP systems. A validation analysis was performed in this paper by a comparison of experimental test results with analytical prediction behaviour by the proposed design equations. A comparative analysis in ultimate limit state was carried out based on national and international studies recently published. Moments at ultimate, effective strains on the FRP, failure modes and type of system (prefabricate or cast in-situ) were compared. It was possible to conclude about some relevant parameters for design, as it is the definition of a value to the effective strain on the FRP reinforcement, the control of premature failure modes and the correct characterization of the FRP properties. From the discussion of the results obtained some conclusions are forwarded with regard to validate the proposed design models for composite reinforced behaviour