Browsing by Author "Deifalla, A"

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Crack sliding model for non-shear FRP-reinforced slender concrete elements under shear
(Frontiers Media S.A., 2023-03) El-said, Amr; Awad, Ahmed; El-Sayed, Taha A; Özkılıç, Yasin Onuralp; Deifalla, A; Tawfik, Maged
Fiber-reinforced polymer (FRP)-reinforced concrete (RC) elements fail under one-way shear in a devastating and complicated manner with no adequate warning. In recent decades, there has been pioneering research in this area; however, there is no agreement among researchers regarding mechanicallybased models. Thus, in this current study, a plasticity-based model is developed for FRP-RC elements under shear. A selected model was firstly assessed for its accuracy, consistency, and safety against an extensive experimental database. Secondly, a plasticity-based model (i.e., crack shear sliding model) was adapted, refined, and proposed for FRP-RC elements under one-way shear. The two proposed models were found to be reliable and more accurate with respect to selected existing methods. Modeling of FRP’s axial rigidity is more consistent only under Young’s modulus with respect to the experimental database. Several concluding remarks on the selected existing models are outlined and discussed to assist the future development of these models and design codes.
Effectiveness of externally bonded CFRP strips for strengthening flanged beams under torsion: An experimental study
(Elsevier, 2013) Awad, Ahmed; Deifalla, A; Elgarhy, M
All over the world, fiber reinforced polymer (FRP) is currently being used for strengthening concrete elements, thus improving the building sustainability. The most recent report by the American Concrete Institute Committee 440 suggested that any proposed anchorage system should be heavily scrutinized before field implementation [4]. A comprehensive literature review was conducted, which showed that anchored U-jacket strips and un-anchored extended U-jacket strips were never examined for the case of RC flanged beams under significant torsion. The objective of this study is to investigate the behavior of FRP externally strengthened flanged beams subjected to torsion. Eleven beams were tested under significant torsion. Both the anchored U-jacket and the extended U-jacket strips were found to be more effective strengthening techniques compared to the un-anchored U-jacket strips and as effective as the …
Experimental and numerical investigation of the behavior of LWFC L-girders under combined torsion
(Elsevier Ltd, 2020-08) Deifalla, A; Awad, A; Seleem, H; Abdelrahman, A
View references (34) In most of the internationally recognized design codes, the design provisions for Light weight concrete (LWC) elements was developed based on modifying normal weight concrete (NWC) ones. With the many impressive advances in manufacturing of LWC including but not limited to adding fibers to the mix. And LWC structures are spread worldwide in various applications. Thus, design codes need a revisit based on actual testing of LWC beams. Since, experimental testing is essential to establish base for the verification of numerical models and updating the current design codes, this paper focused on investigating the behavior of lightweight Foamed concrete (LWFC) L-beams under combined loading. An experimental program was conducted, which included testing five L-beams. A numerical model was developed, which was implemented to model seventeen LWFC L-beams. The effect of the moment to shear-depth ratio (M/Vd), the torsion to shear-depth ratio (T/Vd), the flange width to web width ratio (B/b), and the transversal reinforcement ratio (ρw) was examined. For LWFC L-beams under combined loading with large moment-to-shear-depth ratio (M/Vd > 2), the following was observed: 1) The strength increased with the decrease of moment-to-shear-depth ratio, 2) Increasing torsion to shear-depth ratio by 67% was not effective, as the failure mode was governed by flexure. On the other hand, for the ones with small moment-to-shear-depth ratio (M/Vd ≤ 2), the following was observed: 1) increasing torsion to shear-depth ratio by 67%, decreased the failure load by 28% and changed failure mode from flexure failure to combined shear, and torsion failure; 2) the Concrete contributed significantly to the strength of beams. In addition, for LWFC L-beams under combined loading, the following remarks were observed: 1) Increasing the flange width 1.7 times lead to an increase in the failure load by 24%, which is insignificant, and 2) Using transversal reinforcement ratio above 1.2% changed the failure mode from ductile to brittle. The selected design code was found to be overly conservative, in particular cases of significant torsion and shear. © 2020 Institution of Structural Engineers
Investigating the behavior of lightweight foamed concrete T-beams under torsion, shear, and flexure
(Elsevier Ltd, 9/15/2020) Deifalla, A; Awad, A; Seleem, Hosam; Abdelrahman, Amr
Compared to conventional normal weight concrete, Lightweight Concrete (LWC) has significantly lower own-weight-to-strength ratio and good thermal insulation. Previous studies showed that the design codes underestimate the strength of LWC beams under pure shear force or pure torsion moment. In addition, the behavior and design of LWC T-beams under combined bending, shear and torsion was never investigated. Thus, this current study explores the effect of various parameters on the behavior of lightweight foamed concrete (LWFC) T-beams under combined shear, torsion and moment. Investigated parameters included the following: shear-span-to-depth ratio, torsion-to-shear-depth ratio, flange-to-web-width ratio, and transversal reinforcement ratio. An experimental program was conducted which included testing five T-beams under various ratios of combined loading. In addition, a numerical model was developed for LWFC T-beams under combined loading and verified using available experimental results. Moreover, a parametric study was performed to further investigate the effect of the selected parameters on the behavior of LWFC T-beams. Last but not least, the most recent internationally recognized design code is selected and used to calculate the T-beams strength, which was compared with the ones from the experimental and numerical investigations. For small values of the shear-span-to-depth ratio, the LWFC T-beams strength increased with the decrease of the torsion-to-shear-depth ratio compared to those with large values of the shear-span-to-depth ratio. In addition, the effect of the flange width was found to be insignificant. Moreover, the failure mode for beams with transversal reinforcement ratio above 1.2%, changed from under-reinforced mode to an over-reinforced one. Last but not least, the strength predicted using selected design code was found to be overly conservative compared to that experimentally measured and that numerically predicted for LWFC T-beams under combined loading.