The main objective of this research was studied the flexure behavior of hybrid reinforced concrete beams combining reactive powder concrete (RPC) and lightweight concrete (LWC). The experimental work consists of casting and testing in flexure seven simply supported reinforced concrete beams. The dimensions of (7) beams were geometrically similar, having rectangular cross-section, of dimensions (125×200×1600) mm. Lightweight concrete was used in tension layer and reactive powder concrete was used in compression layer for all hybrid concrete beams. The main variables were; type of concrete (LWC and RPC), thicknesses of RPC layer (h R =0, 50, 100 and 200) mm and longitudinal reinforcement ratios (ρ= 0.0033 and 0.0227). The type of LWC used in the experimental work was porecilenite aggregate. The results showed that the characteristic strength (first and ultimate loads) was increased when the thickness of RPC layer was increased. In addition to that, these parameters were decreased the values of deflection. All beams failed by flexure mode without any shear cracks which achieved by yielding of tensile steel in the tension zone. Also, for all hybrid beams, the slip was absent between the concrete layers. Finally, the reinforcement ratio (ρ) had more effective factor of all parameter used to increase the stiffness value of the beams which increased the characteristic strength and reduced the deflection values.
An experimental study was conducted to investigate the behavior of composite concrete beams damaged and cracked under pure torsion, and then repaired by external strengthening. This was achieved using high strength Carbon Fiber Reinforced Polymer (CFRP) laminates bonded with epoxy four composite modify reactive powder concrete (MRPC) I-beams. Different types of section (Solid & with opening) were tested to obtain the effect of amount of CFRP laminate on beams ultimate torque behavior, angle of twist and failure modes. The results obtained showed that a significant effect of external high strength CFRP laminates on effectively restore of section solid, the range of 89.8% to 91.2% of ultimate torsional strength effectively restored as well as effectively restoring of section opening by 83.48%-86.67% of ultimate torsional strength. The repaired beams give high efficiency in ultimate torsional strength, and indicate that the adopted technique gives a good torsional strength.
Service runs considered as a major nerve of any building. Thus, beam with longitudinal and transverse opening (BLTO) was creative solution for the purpose of serve those runs with other benefits, especially when utilized high strength self-compacting concrete (HS-SCC). This study examined the behavior of eight reinforced concrete (RC) beams. These beams were involved into two groups. All beams had identical in dimensions, reinforcement, concrete type, and hole dimensions. The evaluation used to elect the optimum hollow core section, and position effect of web openings with fixed hollow core section. Due to recorded load capacity, a reduction was produced by hollow core position at mid and bottom section by about (2%-14%), respectively, with comparing by solid section. Therefore, the optimum hollow core section was when it locate in mid beam section which used to unify BLTO sections. BLTO types indicated different loading data according to web opening position. The decrement of opening provision was about (20.4%) by compared with hollow beam (without transverse opening) and about (22%) by compared with the solid beam. The optimum BLTO was when the web opening located in mid-shear zone, while the critical one recorded in web opening position in mid-span and near supports in same BLTO. The registered failure mode of all beams was contained two main types, suddenly flexural failure in compressive zone by concrete cover crushing and flexural-shear failure.
The strength of concrete columns is controlled by the strength of the material and the geometry of the cross section. The use of Reactive Powder Concrete RPC technology has proven most popular with superior strength, stiffness and durability being the major advantages. An experimental investigation was carried into the behavior of RPC 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 the variation of the concrete type (normal or RPC), presence of steel fibers and longitudinal steel ratio. Experimental data on strength, lateral displacement and failure mode was obtained for each test. The comparative analysis of the experimental results showed that the use of RPC caused substantial variation in the ultimate strength and failure modes. Also, inclusion of steel fibers in RPC was an effective way to prevent spalling of the concrete cover and increase the ductility, as well as, high ratio of longitudinal reinforcement delays the buckling of the columns and increases strength.
In this research an investigation has been done on eight reinforced concrete beams. Each beam was strengthened by bolted steel plates attached to their bottom side, of which length and thickness ratio varied, except one beam which has been tested without steel plate as controlling test. Two limits have been introduced upon the maximum plate area used and its minimum length. The first limit is to insure a ductile tension failure, and the latter is to prevent loss of interaction between the two components. Bolts with head were used to provide suitable connection through the specimens of concrete beams and the steel plates through predrilled holes in the steel plates. All beams have similar dimensions and tested simply supported over an effective length of 1600 mm and loaded with central load. Test results show that the plated beam gain an increase in strength over that of unplated beam of about 145%. Also, beams with relatively thin plates, the plate length has little effect upon the ultimate strength, however, for beams with thicker plates the results show a decrease in strength of about 16%.
Reinforced concrete deep beams are structural members having depth much greater than normal in relation to their span, while the thickness in the perpendicular direction is much smaller than either span or depth. The strength of deep beams is usually controlled by shear, rather than flexure. In this study, the previous researches related to reinforced concrete deep beams will be reviewed. These researches approximately started in the second half of the past century. Large numbers of researchers studied the behavior of concrete deep beams and the determination of their capacity. Some of these researches are experimental investigations carried out by testing a number of deep beams with variation in some parameters, while the others are theoretical to estimate deep beam capacity by developing some theories and suggestion of equations for calculating its capacity and comparisons were made with those adopted by some codes. Because of the large number of these researches, their review requires large part of this study, and because the prior studies elaborately reviewed the pioneer researches, only the researches made since year 2000 will be reviewed in this study.
This paper deals with a numerical simulation of reinforced concrete square columns. The behavior of reinforced square columns of normal and high strength concrete was studied, and special attention paid to the concrete strength, ratio of longitudinal steel reinforcement, as well as reinforcement steel grade of this type of columns. In the present study, ABAQUS program was utilized to represent the response of this type of columns. The numerical model of finite element employs the approach of damaged plasticity for concrete. For effectiveness, a column of reinforced concrete was represented that had been comparison with experimental results that presented from the other researchers. In this research the numerical results were done for three types of loading, columns subjected to pure compressive force only (compression failure is done), columns undergo bending moment only (tension failure is done), and finally columns under axial load as well as bending moment such that the tension and compression failure is done at same moment. An interaction equation was derived in this research and can be applicable for any section of columns. The present equation was appeared a very good results when compare its interaction diagram with interaction diagram driven from previous works.
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