S.A. Hadigheh

Interfacial bond strength of resin-impregnated fibre-reinforced polymer laminates bonded to concrete using vacuum and heat: Experimental study

Two processing techniques commonly used in the repair of concrete structures via bond of fibre-reinforced polymer (FRP) onto the substrate are known as the pultruded plate and wet lay-up systems. The pultruded FRP plate and wet lay-up systems both involve the curing of resins of up to several days under ambient conditions to achieve full load capacity and rely on workmanship to achieve good bond. Hence, new techniques for the application of FRP that adopt a vacuum consolidation process and heat to impregnate FRP fibres with resin to improve the curing process, bond strength and speed of application are being developed. In this article, the interfacial bond behaviour of pre-impregnated FRP laminates attached to concrete in the presence of vacuum and heat is studied and compared to more conventional methods of FRP strengthening systems. Further the effects of bondline thickness on the bond performance of pre-preg FRP laminates are also studied whereby three different bondline thicknesses are examined. The interfacial bond thickness was changed by application of resin films between FRP plates and concrete surface.

Application of Heat/resin Injection in the Presence of Vacuum for FRP Attachments on the Concrete Substrate

Advanced processing techniques for the application of Fibre Reinforced Polymer (FRP) materials to repair concrete structures include the adoption of a vacuum consolidation process coupled with heat and/or resin injection to improve the curing process, bond strength and speed of application. The vacuum can contribute to the penetration of the resin into the surface around the exposed aggregates in order to achieve higher bond in strengthened elements. Since, debonding of FRP materials from the substrate is a brittle failure, it is essential to study this phenomenon and propose significant ways to improve the behaviour of the bondline. In this article, the interfacial bond behaviour of FRP laminates attached to concrete in the presence of vacuum and heat/resin injection is studied. The results of single lap shear tests have been utilized to investigate the capability of this system in strengthening of concrete elements. In this regard, several FRP-bonded concrete prisms will be examined in a single lap shear test set-up. Further, the effects of bondline thickness on the bond performance of adhesively bonded joints are studied.

Seismic Behavior of FRP-Retrofitted Reinforced Concrete Frames

Although a significant number of studies have been conducted on the behavior of the reinforced concrete beam-column joints retrofitted with FRP materials, limited investigation considered the overall seismic behavior of the retrofitted frames. In this article, experimental and numerical studies are performed on a scaled-down eight-story and two full scaled low-rise ordinary moment resisting frames (OMRFs) retrofitted with FRP at the joints. Additional, rotational stiffness of the joints is implemented into pushover models to predict seismic performance and behavior factor of the retrofitted frames. Results indicate that FRP retrofitting is more effective than steel braces for low- and medium-rise OMRFs.

Influence of the Processing Techniques on the Bond Characteristics in Externally Bonded Joints: Experimental and Analytical Investigations

AbstractThis paper investigates the bond characteristics between the concrete substrate and fiber-reinforced polymer (FRP) material processed with advanced manufacturing techniques. Tests provide further understanding regarding the interface behavior of the joints manufactured with a heated vacuum bag only (HVBO), vacuum-assisted resin infusion (VARI), wet lay-up, and pultrusion techniques. A specific criterion, the equalization of the processing techniques, is proposed to compare the characteristics of the joints. Based on the outcomes, the advanced processing techniques such as HVBO and VARI can be successfully applied to achieve a high-quality bond in strengthening of the reinforced concrete structures. Furthermore, a new analytical approach is presented to determine the interface behavior, which can be applied to any type of the FRP processing technique.