External Prestressed Carbon Fiber-Reinforced Polymer Straps for Shear Enhancement of Concrete

Abstract

The use of fiber reinforced polymers (FRPs) for the strengthening and repair of existing concrete structures is a field with tremendous potential. The materials are very durable and hence ideally suited for use as external reinforcement. Although extensive work has been carried out investigating the use of FRPs for flexural strengthening (e.g. Meier et al., 1992) a fairly recent development is the use of these materials for the shear strength enhancement of concrete.The current system investigates the use of post-tensioned non-laminated carbon fiber reinforced polymer (CFRP) straps as external shear reinforcement for concrete. Experiments were carried out on an unstrengthened control beam and beams strengthened with external CFRP straps. It was found that the ultimate load capacity of the strengthened beams was significantly higher than that of the control specimen.Existing design codes and analysis methods were found to underestimate the ultimate resistance of the control specimen and the strengthened beams. Nevertheless, the modified compression field theory provided insight into possible failure mechanisms and the influence of the strap prestress level on the structural behaviour.It is concluded that the use of these novel stressed elements could represent a viable and durable means of strengthening existing concrete infrastructure.

Advanced fibre-reinforced polymer (FRP) composite materials in bridge engineering: materials, properties and applications in bridge enclosures, reinforced and prestressed concrete beams and columns

“…∑ a number of debonding models have been developed and have been incorporated into design guidelines (aCI, 2008;CaN/CSa, 2006), but Holzenkämpfer (1994), Neubauer and Rostásy (1997) and Chen and Teng (2001) had undertaken theoretical studies on bond models and a question is now raised, 'how well do the results of these bond models compare with the predictions of the debonding models?' Lees et al (2002) proposed a system which used carbon fibre reinforced thermoplastic tape straps as external post tensioned shear reinforcement for concrete. The tape was thin (typically between 0.12 and 0.16 mm thick) and was composed of high strength carbon fibres oriented in the longitudinal direction.…”

Repair of reinforced concrete deep beams using post-tensioned CFRP rods

“…Previous research has shown that CFRP tendons can be used in new construction [1,2]; hybrid FRP composite tendons have also been used for post tensioning concrete beams [3]. Limited research has been conducted using external post-tensioned CFRP sheets [4,5], CFRP straps [6], or CFRP tendons for repair of RC or PC beams [7][8][9][10][11]. Recently, a new unibody clamp anchor and mechanical stressing system have been developed for post-tensioning CFRP rods [12].…”

Modelling crack propagation in structures: Comparison of numerical methods

“…An in-depth understanding of the behaviour 1374 X.-S. YANG, J. M. LEES AND C. T. MORLEY of cracked reinforced concrete structures is of particular importance in the field of strengthening and repair. In such applications, an existing structure will have been subjected to a complex load history during its lifetime and it is necessary to be able to model any existing damage that may have occurred prior to the application of any strengthening system [1][2][3][4].…”

“…For example, the technique of strengthening existing reinforced concrete structures using external carbon fibre-reinforced polymer (CFRP) reinforcement is most promising [1][2][3]. However, FRP materials are brittle and elastic, so a reliable prediction of the stresses and strains in the FRP reinforcement applied to a cracked concrete structure is important.…”