Future University In Egypt (FUE)
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Altagamoa Al Khames, Main centre of town, end of 90th Street
New Cairo
Egypt
Faculty of Engineering & Technology

Ahmed Farouk Mohamed Hassan Deifalla

Basic information

Name : Ahmed Farouk Mohamed Hassan Deifalla

Education

Certificate Major University Year
PhD Civil Engineering McMaster University - Canada 2008
Masters Civil Engineering - Structural Engineering Cairo University - Faculty of Engineering 2001
Bachelor civil engineering Cairo University - Faculty of Engineering 1998

Researches /Publications

Refining the torsion design of fibered concrete beams reinforced with FRP using multi-variable non-linear regression analysis for experimental results - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

01/01/2021

There is very little guidance for practitioners regarding the torsion design of fiber-reinforced polymer (FRP) and hybrid reinforced concrete beams, especially those with fibered concrete (FC). The purpose of this study is to improve the handful of methods used for predicting the torsion cracking and ultimate strength of reinforced concrete (RC) beams with FRP reinforcements. An experimental database of 46 RC beams with FRP or hybrid reinforcements and tested under torsion were compiled from seven different studies. Two proposed models (PM1 and PM2) based on the existing torsional model for FRP reinforced concrete beams and calibrated to fit the experimental data using multilinear non-linear regression. The cracking and ultimate torque predicted using the proposed models are more accurate compared with that calculated using selected ones existing in the literature. The PM1 is consistent with the existing design codes, yet more accurate compared to them. While the PM2 is non-iterative yet capture the actual variation of the strength with the effective parameters.

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Design of lightweight concrete slabs under two-way shear without shear reinforcements: a comparative study and a new model - 01/1

Ahmed Farouk Mohamed Hassan Deifalla

01/11/2020

Developing design models that are accurate compared to experimentally measured strength, yet physically sound, continues to be the ultimate research goal. For this purpose, the two-way shear design provisions of the American design codes have been updated. While that of the European design codes are being investigated. The two-way shear failure of slabs is a sudden one, which can be catastrophic. In addition, lightweight concrete (LWC) is gaining a lot of attention due to its economic advantage, however, very limited studies focus on investigating LWC slabs under two-way shear loading. The purpose of this study is to examine existing design codes and ongoing proposals for the case of LWC slabs under two-way shear. A comprehensive literature review of the available two-way shear testing for LWC slabs was conducted. An extensive database with a total of 129 tested LWC slabs was compiled. Selected design codes were used to calculate the two-way shear strength of the tested slabs. The Strength ratio (SR) was compared for selected codes, which is calculated as the ratio between the experimentally measured strength and that calculated using different design codes. In addition, the effect of various parameters on the SR was assessed. Concluding remarks were outlined and discussed. Moreover, a design formula for LWC slabs under two-way shear, which is physically sound and simple was developed and validated using experimental results. It was found to be more accurate, and more consistent compared to existing design codes with regard to experimentally measured strength. It is worth noting, that the investigated draft of the Eurocode is not final. However, these findings could help develop future design provisions for two-way shear of LWC slabs, which have to be physically sound, more consistent, and more accurate compared to existing one.

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Strength and Ductility of Lightweight Reinforced Concrete Slabs under Punching Shear - 01/1

Ahmed Farouk Mohamed Hassan Deifalla

01/10/2020

Preventing a sudden punching failure and achieving an economic design, require reliable mechanical models that make physical sense. In addition, Lightweight (LW) concrete is gaining a lot of attention due to its economic advantage. Moreover, all design codes offer punching shear provisions for LW concrete as a viable alternative for the conventional Normal weight (NW) concrete. However, these punching shear provisions were developed for NW concrete slabs. The purpose of this study is to develop a mechanical model for the punching shear behavior of LW concrete slabs, that make physical sense. Inspired with the well-established critical shear crack theory, a punching shear mechanical model for LW concrete slabs was developed, validated, and proposed. In addition, using the proposed model, a parametric study was conducted in order to investigate the effect of concrete density, slab depth, flexure reinforcement ratio on the strength and ductility of LW concrete slabs under punching loads. The proposed model accounted for the effect of concrete type using both the aggregate size and the concrete density. Thus, resulted in a more consistent and more accurate strength and rotation predictions compared to existing models and design codes with respect to the experimental results of LW concrete slabs. The results of the parametric study showed that increasing the concrete density, decreasing the slab depth leads to an increase in the failure strength, the failure rotation, and the ductility. In addition, increasing the flexure reinforcement ratio increase the strength but decreases the failure rotation and ductility.

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Investigating the Behavior of Lightweight Foamed Concrete T-Beams under Torsion, shear, and Flexure - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

Awad A, Elrahman AA, Seleem H

01/09/2020

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.

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Experimental and numerical in- vestigation of the behavior of LWFC L-girders under combined torsion - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

Awad A, Seleem H, AbdElrahman A

01/08/2020

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.

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Experimental and numerical in- vestigation of the behavior of LWFC L-girders under combined torsion - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

Awad A, Seleem H, AbdElrahman A.

01/04/2020

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.

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Performance of Steel Fiber Reinforced Concrete Corbels - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

Saleh A, Fathy A, Moaz Nasser M

01/02/2019

Seven full-scale reinforced concrete corbel specimens were tested to study performance of steel fiber reinforced concrete corbels with and without fibers were investigated. The test variables were steel fiber content (Vf %) and shear span-to-depth ratio (a/d), which Constants of concrete compressive strength (fcu), area of main steel reinforcement (As) and presence of horizontal stirrups. Test results showed that, addition of steel fibers or/and horizontal stirrups improves both shear strength and ductility of the tested corbels, and results in a more ductile failure mode. The Experimental results observed that the ultimate strength of reinforced concrete corbels along with fibers can be predicted by adding the fibers contribution to strength using the shear friction equation to the ACI Building Code provisions. It is found that considerable improvement in ultimate shear strength and first crack in the corbels. This study shows that there is a considerable increase in the ultimate shear strength of steel fiber reinforced concrete corbels is obtained by the addition of steel fibers for a specific range and with a fiber content of 1,2 and3 percent, an increase in the shear strength was obtained and decrease shear span to depth ratio from 0.80 to 0.65.

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Behavior of stiffened and unstiffened CFT under concentric loading, An experimental study - 01/0

Ahmed Farouk Mohamed Hassan Deifalla

Fattouh F M, Fawzy M M and Hussein I S

01/01/2019

Concrete-filled steel tubular (CFST) beam-columns are widely used owing to their good performance. They have high strength, ductility, large energy absorption capacity and low costs. Externally stiffened CFST beam-columns are not used widely due to insufficient design equations that consider all parameters affecting their behavior. Therefore, effect of various parameters (global, local slenderness ratio and adding hoop stiffeners) on the behavior of CFST columns is studied. An experimental study that includes twenty seven specimens is conducted to determine the effect of those parameters. Load capacities, vertical deflections, vertical strains and horizontal strains are all recorded for every specimen. Ratio between outer diameter (D) of pipes and thickness (t) is chosen to avoid local buckling according to different limits set by codes for the maximum D/t ratio. The study includes two loading methods on composite sections: steel only and steel with concrete. The case of loading on steel only, occurs in the connection zone, while the other load case occurs in steel beam connecting externally with the steel column wall. Two failure mechanisms of CFST columns are observed: yielding and global buckling. At early loading stages, steel wall in composite specimens dilated more than concrete so no full bond was achieved which weakened strength and stiffness of specimens. Adding stiffeners to the specimens increases the ultimate load by up to 25% due to redistribution of stresses between stiffener and steel column wall. Finally, design equations previously prepared are verified and found to be only applicable for medium and long columns.

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