Flexural Behaviour of Composite High Strength Concrete – Fibre Reinforced Polymer Beams
This paper presents the results of an experimental study conducted to examine the effectiveness of Glass Fibre Reinforced Polymer (GFRP) laminates in enhancing the flexural capacity of high strength concrete beams. In this study, a total of ten beams of size 150 mm x 250 mm in crosssection with a total length of 3000 mm were cast and tested. Eight beams were strengthened with chopped strand mat glass fibre reinforced polymer and uni-directional cloth glass fibre reinforced polymer of 3mm and 5mm thickness. The study parameters included the reinforcement ratio, GFRP laminate material and their thickness. All the beam specimens were subjected to four-point bending test in a loading frame. Deflection and strain measurements have been made through appropriate instrumentation. The results show that the GFRP strengthened beams exhibit increased strength, flexural stiffness and composite action until failure. Keywords— GFRP, HSC beams, laminates, strengthened
Behavior of Precracked RC Beams Strengthened with Carbon FRP Sheets
Experimental data obtained from strengthened, precracked, reinforced concrete (RC) specimens are presented together with the results of material characterization. Strengthening was attained with the adhesion of carbon fiber-reinforced plastic (CFRP) sheets to the concrete surface. The CFRP was applied as in situ (i.e., working under the beam). Several variables were investigated, including: two CFRP material systems, two concrete surface preparations, two RC cross sections, and the number and location of CFRP plies. For two specimens, the presence of applied load (simulating the total service load) as well as external prestressing during the adhesion of the CFRP reinforcement, were investigated. It is shown that the effect of CFRP strengthening was considerable, but the effect of some of the tested variables was modest. An existing analytical model has been extended to simulate the load-deflection behavior as well as the failure mode of the precracked RC specimens. Different failure mechanisms from ductile to brittle were simulated and verified, adopting the mechanical properties of the constituent materials obtained via standard tests or using a simple test for concrete-adhesive interface.
Flexural strengthening of concrete beams using externally bonded composite materials
In this study, a series of reinforced concrete beams were tested in four-point bending to determine the ability of externally bonded composite fabrics to improve the beams' flexural capacity. The fabrics used were made of aramid, E-glass and graphite fibres, and were bonded to the beams using a two-part epoxy. The different fabrics were chosen to allow a variety of fabric stiffnesses and strengths to be studied. The external composite fabric reinforcement led to a 36 to 57% increase in flexural capacity and a 45 to 53% increase in flexural stiffness. For the beams reinforced with E-glass and graphite fibre fabrics, failures were a result of fabric tensile failure in the maximum moment region. The beams reinforced with aramid fabric failed due to the crushing of the compression concrete. In addition to the test results, an analytical model based on the stress-strain relationships of the concrete, steel and composite fabrics is presented. Using the model, beam response is computed and compared with the experimental results. The comparisons indicate that the flexural behaviour of composite-fabric-reinforced concrete beams can be accurately predicted using the described method.