FLEXURAL BEHAVIOUR OF CONTINUOUS REINFORCED CONCRETE BEAMS STRENGTHENED WITH EXTERNALLY BONDED FIBER REINFORCED POLYMERS

Abstract

Nowadays, modern methods are used as fiber reinforced polymers (FRP) in repairing and strengthening different structural elements with different materials (Steel, reinforced concrete, masonry, timbre …etc.), and it proved an excellent alternative for the traditional methods due to their ease in handling, lightweight, and non-corrosive materials. Many experimental studies reported that this technique is very effective for strengthening and repairing beams due to their high strength capacity. The survey of the literature showed the need for research on the behavior of strengthened continues reinforced concrete beams with different strengthening techniques. To meet this need, this study was utilized to predict the behavior of the strengthened continuous reinforced concrete beams under a wide range of parameters under monotonic increasing load. This research aims to investigate the effect of strengthening schemes on the flexural strength of a continuous RC beams under a wide range of parameters as changing the length of the CFRP sheets used, a number of layers, width, reinforcement ratio as well as the concrete compressive strength. Seven beams were constructed and studied experimentally and analytically. An analytical study based on non-linear FE computer program ANSYS was utilized to verify and complete the experimental work and to understand the behavior of the strengthened continuous beams. A parametric study was investigated by using 540 different specimens to discuss analytically more parameters and to investigate the effect of each parameter on the flexural capacity and behavior of the strengthened continuous beams. The test results showed that using CFRP sheets increase the specimen's capacity and it is considered the easiest method for field applications, however, the failure of the specimens by deboning of CFRP sheets is possible and may cause a sudden failure. It is clear that CFRP sheets control the cracks propagation and width to a great extent. Using one CFRP layer on the tension side of the beams enhances the performance and capacity, and controlled the crack. Rupture failure occurs usually by using single CFRP layer. The common mode of failure above the support is a rupture, while de-bonding occurs at mid-span. In case of using small areas of CFRP sheets, the number of layers is not effective. Numbers of layers affects the modes of failure to a great extent. When the number of layers increased the mode of failure is likely to be de-bonding. All specimens were investigated by using symmetrical strengthening configuration, and the same CFRP sheets length and width in both sagging and hogging regions.