Papers by Dr.Hassan Falah
There are few researches about tapered reinforced concrete elements and it shear failure mechanis... more There are few researches about tapered reinforced concrete elements and it shear failure mechanisms is not well understood. In the present paper, tests were carried out on six beams, simply supported under the effect of two points loading at the ends. Five beam specimens where tapered (non-prismatic shape) while, the last one has a rectangular prismatic shape. The dimensions of the tapered beams were kept constant for all tested beams. The adopted variables were the shape of the tested beams, amount of shear reinforcement and strengthening by CFRP strips. Test results show that the tapered beams without web reinforcement have a superior shear capacity for about (12%) as compared with the prismatic beam, and the strengthening by CFRP strips for tapered beams, enhance the shear capacity for about (30%). Also, the increase of load capacity for tapered beam with half-minimum, and minimum web reinforcement, according to ACI-318 Code for prismatic beam, were (20%) and (33%) respectively as compared with tapered beam without web reinforcement.
The solution of using glass fiber reinforced polymer (GFRP) bars, as reinforcement in concrete st... more The solution of using glass fiber reinforced polymer (GFRP) bars, as reinforcement in concrete structures to overcome the problems created by steel reinforcement, is now widely accepted because of both its low cost and good results shown by large investigation efforts. In this paper twelve tests had been conducted on reinforced concrete column specimens of (120 x 120 x 1000 mm effective dimensions) equally enlarged from both ends for the purpose of applying eccentric load, three specimens were made of high strength concrete , reinforced with traditional deformed steel bars and stirrups to be considered as references, while the remaining nine specimens were of high strength concrete with 0, 0.5, 1.0% steel fiber, reinforced longitudinally with GFRP bars and wrapped with carbon fiber reinforced polymer (CFRP) textile replacing the steel stirrups .In addition to the similarity in behavior under load and in the failure patterns of the specimens reinforced with GFRP bars and the specimens reinforced with traditional steel, the results show that Steel reinforced columns has 13% higher ultimate load than corresponding GFRP reinforced columns, also an approximate linear increase in the first crack and failure load with the presence of steel fiber in concrete in range from 20% to 42% for 1% fiber content and in range of 21% to 26 % for the first crack and ultimate load respectively . The ductility of the specimen reinforced with GFRP bars is 90% higher than that of steel reinforced specimens of 𝝆=2.18% and 10% more for those of 𝝆=5.58%.
This work is devoted to studying the mechanical properties of reactive powder concrete(RPC) and m... more This work is devoted to studying the mechanical properties of reactive powder concrete(RPC) and modified reactive powder concrete (MRPC) as a material as well as studying the punching shear behavior of RPC and MRPC slabs. The experimental program includes investigating the effect of steel fiber volumetric ratio (V f) and absence of coarse aggregates on some important mechanical properties of RPC and MRPC such as compressive strength, uniaxial stress-strain relationship in compression, splitting tensile strength and modulus of rupture. Additional experimental tests are also conducted to study the effect of V f , steel reinforcement ratio (ρ) and slab thickness on the punching shear behavior (in terms of load-deflection response, load-strain response and ultimate failure load) of simply supported reinforced RPC slabs having dimensions of 1000×1000× 50 or 70 mm under concentrated load at the center of the slab. Keywords : MRPC , steel reinforcement ratio (ρ) , steel fiber volumetric ratio (V f)
This work is devoted to study the mechanical properties of reactive powder concrete(RPC) and modi... more This work is devoted to study the mechanical properties of reactive powder concrete(RPC) and modified reactive powder concrete (MRPC) as a material as well as studying the punching shear behavior of RPC and MRPC slabs. The experimental program includes investigating the effect of steel fiber volumetric ratio (V f) and absence of coarse aggregates on some important mechanical properties of RPC and MRPC such as compressive strength, modulus of elasticity (E), splitting tensile strength and modulus of rupture. Additional experimental tests are also conducted to study the effect of V f , steel reinforcement ratio (ρ) and slab thickness on the failure characteristics of the punching shear (in terms of observation of failure, shape of the failure zone, size of the failure zone, failure angles, critical section perimeters and ultimate punching shear stress) of simply supported reinforced RPC slabs having dimensions of 1000×1000× 50 or 70 mm under concentrated load at the center of the slab.
This paper presents an experimental investigation on shear behavior of GFRP reinforced high stren... more This paper presents an experimental investigation on shear behavior of GFRP reinforced high strength concrete beams externally strengthened in shear using CFRP with various configurations: full side sheets, U-strips, vertical side strips and diagonal side strips; and three steel fiber ratios (0%, 0.5% and 1%). Results show that using GFRP bars as tension reinforcement instead of traditional steel bars slightly increases ultimate load but shows lower stiffness. Although internal steel stirrups are still the most effective way to enhance shear capacity of concrete beams, externally bonded CFRP U-strips can also be an effective alternative for durability and/or architectural considerations with about 85% strength efficiency and comparable load-deflection behavior. A combination of U-strips and sufficient amount of steel fiber is shown to perform better than steel stirrups in terms of increasing carrying capacity and decreasing deflections of GFRP reinforced concrete beams.
An experimental investigation was conducted to investigate the behavior of ultra-high strength re... more An experimental investigation was conducted to investigate the behavior of ultra-high strength reactive concrete (RPC) columns before and after strengthening with carbon fiber reinforced polymer (CFRP) sheets jacketing under eccentric axial load. Twelve columns were tested up to failure, strengthened and retested to examine strengthening efficiencyand to evaluate the effects of variation of the concrete type (normal or RPC), presence of steel fibers and main steel reinforcement ratio. Experimental results showed thatCFRP jacketing increases the ultimate failure load of strengthened columns up to 185%, highly stiffens them (reduces lateral displacements) and allow more ductile failure than the original columns. Also, inclusion of steel fibers in RPC columns increases failure loads up to 86%, prevents palling of the concrete cover and increase the ductility.
This paper presents an experimental investigation consisting of casting and testing twelve rectan... more This paper presents an experimental investigation consisting of casting and testing twelve rectangular simply supported reinforced concrete deep beams. Three of the tested beams are made with conventional concrete (CC), three with ultra-high performance concrete (UHPC) and six as hybrid beams of the two concrete (UHPC &CC). UHPC is used in compression in the hybrid beams. The effect of these parameters on the behavior of the test beams included deflection, failure mode, and ultimate loads is investigated. Experimental results generally show that stiffer loaddeflection behavior is obtained with the increase of UHPC layer thickness (h R /h) and steel fibers volumetric ratio (V f ) for hybrid beams with UHPC in compression.
An experimental investigation was conducted to investigate the behavior of ultra-high strength mo... more An experimental investigation was conducted to investigate the behavior of ultra-high strength modified reactive concrete (MRPC) columns subjected to axial load with initial eccentricity. Twelve columns were prepared with 120mm square section at the midsection and were hunched at the ends to apply eccentric loading. The specimens were tested up to failure to evaluate the effects of variation of the concrete type (normal or MRPC), presence of steel fibers and longitudinal steel ratio. Experimental data on strength, lateral displacement and failure mode was obtained for each test. Comparative analysis of the experimental results showed the use of MRPC caused substantial variation in the ultimate strength and failure modes. Also, inclusion of steel fibers in MRPC was an effective way to prevent spalling of the concrete cover and increase the ductility, as well as, high ratio of longitudinal reinforcement delay the buckling of the columns and increase its strength.
way slabs cast using high strength self-compacting concrete (HSSCC) with using steel fibers to ev... more way slabs cast using high strength self-compacting concrete (HSSCC) with using steel fibers to evaluate their flexural behavior and strength. The slabs were subjected to concentrated transverse loads (loads were distributed across the entire width of the slab) at the third points. All tested slabs have dimensions of 1000×450×50 or 70 mm. The parameters considered are slab thickness, steel reinforcement ratio (ρ) and steel fiber volumetric ratio (V f ). The effect of these parameters on the behavior of the tested slabs included investigation of deflection, failure mode, and ultimate loads. Two different failure modes were predicted either flexural tension mode or flexural shear mode or a combination of these two.
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Papers by Dr.Hassan Falah