Engineering and Technology Journal

The present paper investigates experimentally the impacts of fiber layer orientation on the structural behavior of CFRP strengthened steel-plated girders that are subjected to shear. Three of these girders were considered strengthened girders whereas the last one represents the reference girder. Each of the four steel-plated girders was tested aside and in different periods of time using the shear buckling test. A point load was applied to the center of the top flange of the four girders using Avery hydraulic machine. A laminated carbon fiber reinforced polymer sheet (CFRP) was fully adhesively attached to the web area of the three girders. The attached carbon fiber sheet took different patterns: either on one side or on both sides. Such a step helps to evaluate the most effective strengthening technique of each of the girders using CFRP composite. To check the behavior and the increase in the ultimate shear capacity of the girders, several parameters were examined. Results have revealed that both the unstrengthen and strengthened girders of different orientations of CFRP showed a similar stiffness behavior at a relatively low load levels. However, when the load is increased, the stiffness behavior significantly is increased in the three strengthened girders, compared to the strengthened girders. It has further shown that the ultimate shear load of the three strengthened girders were higher than that of the reference girder. Such a result can clearly be exemplified by the obtained ranges: 19.56% and 25% depending on the orientation of the CFRP laminates. Following Von Mises stresses, the researcher was able to predict the ultimate shear load of the four girders and to figure out the arrived at results from the four experimental tests.

A total of fourteen beams, 100×150 mm in cross-section were tested in the laboratory over an effective span of 2000 mm. Two of them were used as reference beams. Twelve fiber reinforced concrete beams were provided with externally bonded CFRP laminates at the soffit of the beam. The variables considered included number of CFRP layers, yield strength of steel reinforcement (fy) and steel reinforcement ratio (). All the beams were tested until failure. The test results showed that the ultimate load carrying capacity increased by 56% as average by increasing of the ratio of steel reinforcement from (0.0127 to 0.0324). The deflection ductility index DDI values averaged (1.80) and (1.75) for one-layer strengthened beams and two-layer ones, respectively. The corresponding energy ductility index EDI values averaged (1.75) and (1.73), respectively. The DDI and EDI for the control beams were 4.61 and 6.24, respectively. With the exception of the control beams, all of the beams exhibited poor ductility. Failures in all strengthened beams were accompanied by the release of large amounts of energy (known as elastic energy) relative to inelastic energy. Therefore, a reasonable factor of safety should be used in the design of FRP strengthened reinforced concrete members.

This study presents an experimental and nonlinear finite element analysis of creating square openings in existing RC beams and strengthening with CFRP laminate. Flexural strengthening of reinforced concrete beams is now becoming more and more important in the field of structural maintenance and retrofitting. In the experimental programming, three RC beams were cast. Two beams were tested in the un-strengthened condition the first act as the solid Control beam, and the other have openings, the third one have opening and strengthening with CFRP laminate. The beams were also modeled using a FEM packaged (ANSYS 11). The results indicate that the strengthened beam recorded the highest failure load and its mode of failure was ductile. The numerical results seemed to be able to predict the behavior of the beams.