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Bashir H. Osman,Erjun Wu,Bohai Ji,Suhaib S. Abdulhameed 한국콘크리트학회 2017 International Journal of Concrete Structures and M Vol.11 No.1
Strengthening reinforced concrete (RC) beams with openings by using aramid fiber reinforcement polymers (AFRP) on the beams’ surfaces offers a useful solution for upgrading concrete structures to carry heavy loads. This paper presents a repairing technique of the AFRP sheets that effectively strengthens RC beams, controls both the failure modes and the stress distribution around the beam chords and enhances the serviceability (deflection produced under working loads be sufficiently small and cracking be controlled) of pre-cracked RC beams with openings. To investigate the possible damage that was caused by the service load and to simulate the structure behavior in the site, a comprehensive experimental study was performed. Two unstrengthened control beams, four beams that were pre-cracked before the application of the AFRP sheets and one beam that was strengthened without pre-cracking were tested. Cracking was first induced, followed by repair using various orientations of AFRP sheets, and then the beams were tested to failure. This load was kept constant during the strengthening process. The results show that both the preexisting damage level and the FRP orientation have a significant effect on strengthening effectiveness and failure mode. All of the strengthened specimens exhibited higher capacities with capacity enhancements ranging from 21.8 to 66.4%, and the crack width reduced by 25.6–82.7% at failure load compared to the control beam. Finally, the authors present a comparison between the experimental results and the predictions using the ACI 440.2R-08 guidelines.
Osman, Bashir H.,Wu, Erjun,Ji, Bohai,Abdulhameed, Suhaib S. Korea Concrete Institute 2017 International Journal of Concrete Structures and M Vol.11 No.1
Strengthening reinforced concrete (RC) beams with openings by using aramid fiber reinforcement polymers (AFRP) on the beams' surfaces offers a useful solution for upgrading concrete structures to carry heavy loads. This paper presents a repairing technique of the AFRP sheets that effectively strengthens RC beams, controls both the failure modes and the stress distribution around the beam chords and enhances the serviceability (deflection produced under working loads be sufficiently small and cracking be controlled) of pre-cracked RC beams with openings. To investigate the possible damage that was caused by the service load and to simulate the structure behavior in the site, a comprehensive experimental study was performed. Two unstrengthened control beams, four beams that were pre-cracked before the application of the AFRP sheets and one beam that was strengthened without pre-cracking were tested. Cracking was first induced, followed by repair using various orientations of AFRP sheets, and then the beams were tested to failure. This load was kept constant during the strengthening process. The results show that both the preexisting damage level and the FRP orientation have a significant effect on strengthening effectiveness and failure mode. All of the strengthened specimens exhibited higher capacities with capacity enhancements ranging from 21.8 to 66.4%, and the crack width reduced by 25.6-82.7% at failure load compared to the control beam. Finally, the authors present a comparison between the experimental results and the predictions using the ACI 440.2R-08 guidelines.
Bashir H. Osman,Erjun Wu,Bohai Ji,Suhaib S. Abdulhameed 대한토목학회 2017 KSCE Journal of Civil Engineering Vol.21 No.1
The introduction of an opening into a Reinforced Concrete (RC) beam leads to a reduction to both the beam’s stiffness and its overall structural capacity due to stress concentrations and local cracking around the opening. This paper uses both the experimental and finite element (FE) method to analyze the shear behavior of RC beams with opening. The shear span-to-depth ratios ( ), opening size, and opening location were considered as the main parameters. The beams were divided into three series according to the shear span-to-depth ratios. Three reinforced concrete beams without openings and one beam with openings were tested experimentally under two-point loading. These beams were considered as control beams so as to validate the FE model using ANSYS14.5 software. A total of 31 specimens were analyzed using ANSYS14.5 while considering the above mentioned parameters. Results showed that the openings located in a high shear region (the line connecting the load and support points) led to the early collapse of the beam. In addition, by comparing the experimental results with those of the non-linear FE analysis, it was concluded that both results were in accordance. An analytical equation for predicting the shear strength of RC beams with circular openings was then proposed, and the obtained results later compared with those from FE model. Furthermore, the developed FE models can serve as a numerical platform for performance predictions of RC beams with different web opening geometries.