Nine continuousconcretedeepbeamsreinforced with glass fibre reinforced polymer (GFRP) bars were experimentally tested to failure. Three main parameters were investigated, namely, shear span-to-overall depth ratio, web reinforcement and size effect. The experimental results confirmed the impacts of web reinforcement and size effect that were not considered by the strut-and-tie method (STM) of the only code provision, the Canadian S806-12, that addressed such elements. The experimental results were employed to evaluate the applicability of the methods suggested by the American, European and Canadian codes as well as the previous studies to predict the load capacities of continuousdeepbeamsreinforced with GFRPbars. It was found that these methods were unable to reflect the influences of size effect and/or web reinforcement, the impact of which has been confirmed by the current experimental investigation. Therefore, a new effectiveness factor was recommended to be used with the STM. Additionally, an upper-bound analysis was developed to predict the loadcapacity of the tested specimens considering a reduced bond strength of GFRPbars. A good agreement between the predicted results and the experimental ones was obtained with the mean and coefficient of variation values of 1.02 and 5.9%, respectively, for the STM and 1.03 and 8.6%, respectively, for the upper-bound analysis.
FRP has been used extensively for strengthening structural components including the application of FRP sheets or plates as external reinforcement to the exterior surface of beams  and slabs . Also, FRP sheets have been used to repair damaged reinforcedconcrete (RC) columns . The use of FRP as external reinforcement not only provides additional strength but also provides confinement to a deteriorated structure. FRP bars have also been used as internal reinforcement in reinforcedconcretebeams  and slabs . The use of FRP bars in civil infrastructures is advantageous especially for structures located in marine and salt environments. As FRP is a non-corrosive material, they are resistant to corrosion due to the exposure to de-icing salts. It is noted that, for conventional steel RC structures, exposure to harsh environments including moisture and temperature reduces the alkalinity of the concrete and causes corrosion of the steel reinforcement and ultimately results in the loss of serviceability and strength. Internal FRP reinforcement is also beneficial in increasing the load carrying capacity of beams, especially for beams constructed with high strength concrete . Also, increasing the FRP tensile reinforcement ratio is a key factor in enhancing load carrying capacity and controlling deflection .
Comparisons between test results and predictions obtained from the strut-and-tie model recommended by ACI 318-05 as developed above are shown in Table 3 and Fig. 11: Fig. 11 (a) for simple deepbeams given in appendix A and Fig. 11 (b) for continuousdeepbeams including Rogowsky et al.’s and Ashour’s test results. In simple deepbeams, the width of strut can be calculated from w t ' cos ( l p ) E sin , and the total load is 2 F E sin . Although Eq. (7) proposed by ACI 318-05 is recommended for deepbeams having concrete strength of less than 40 MPa, the loadcapacity of H-series beams were also predicted using this equation to evaluate its conservatism in case of high-strength concretedeepbeams. The mean and standard deviation of the ratio,
Generally, both prediction equations underestimated the flexural capacity of all the tested beams. The average theoretical strengths of the beams based on ACI 440.1R-06 and CSA S806- 12 are 76 % and 81%, respectively, of the experimental flexural strengths. Generally, this finding can be attributed to three major factors. First, the assumed concrete compressive strains (0.003~0.0035) used in the predictions are lower compared to the actual strain recorded during the flexural tests, which reached higher values ranging from 0.0042 to 0.0048. Second, the prediction equations did not include the contribution of the reinforcement in the compression zone. Finally, the confinement effect due to the lateral ties (stirrups) provided in the pure bending-moment zone were not considered.
shown that strut and tie models could be usefully applied to deepbeams and corbels. From that point, the present authors began their efforts to systematically expand such models to entire structures and all structures. The approaches of the various authors cited above differ in the treatment of the prediction of ultimate load and the satisfaction of serviceability requirement. Form a practical viewpoint, true simplicity can only be achieved if solutions are accepted with sufficient accuracy. Therefore, it is proposed here to treat in general the ultimate limit state and serviceability in the cracked state by using one and the same model for both.
This paper presents experimental and analytical study related to the flexural behavior of concretebeams longitudinally reinforced with GFRPbars. The specimens consist of simply supported reinforcedconcretebeams with two point load. Totally 16 concretebeams includes 8 beamsreinforced with steel and 8 beamsreinforced with GFRPbars were tested to failure. Flexural capacity of the beam was observed experimentally and analytically. A computer program of cross sectional analysis using discrete element model was developed in this study to determine the flexural capacity of the beams. In addition, available stress-strain model proposed by the other researchers was used in order to simulate the behavior of material in calculation process. Finally, the flexural capacity obtained from analytical calculation was compared to that obtained from the test in term of moment-curvature curves and load deflection curves. The results show that beam reinforced with GFRP experienced larger ultimate load and larger deflection at same load level compared to beam reinforced with steel.
The shear capacity of deepbeams is a major issue in their design. The behavior of reinforcedconcretedeepbeams is dif- ferent from that of slender beams because of their relatively larger magnitude of shearing and normal stresses. Unlike slen- der beams, deepbeams transfer shear forces to supports through compressive stresses rather than shear stresses. There are two kinds of cracks that typically develop in deepbeams: ﬂexural cracks and diagonal cracks. Diagonal cracks eliminate the inclined principal tensile stresses required for beam action and lead to a redistribution of internal stresses so that the beam acts as a tied arch. The arch action is a func- tion of a/d (shear span/depth) and the concrete compressive strength, in addition to the properties of the longitudinal reinforcement. It is expected that the arch action in FRP rein- forced concrete would be as signiﬁcant as that in steel rein- forced concrete and that the shear strength of FRP- reinforcedconcretebeams having a/d less than 2.5 would be higher than that of beams having a/d of more than 2.5 . The application of the reinforcedconcretedeepbeams within structural engineering practice has risen substantially over the last few decades. More specially, there has been an increased practice of including deepbeams in the design of tall buildings, offshore structures, wall tanks and foundations. They differ from shallow beams in that they have a relatively larger depth compared to the span length. As a result the strain distribution across the depth is non-linear and cannot be described in terms of uni-axial stress strain characteristics . Prediction of behavior of deepbeams by design codes which contain empirical equations derived from experimental tests has some limitations. They are only suitable for the tests con- ditions they were derived from, and most importantly, they fail to provide information on serviceability requirements such as structural deformations and cracking. Likewise, the strut and tie model, although based on equilibrium solutions thus pro- viding a safe design, does not take into account the non-linear material behavior and hence also fails to provide information on serviceability requirements. Cracking of concrete and yielding of steel are essential features of the behavior of
ABSTRACT: The main purpose of this study investigated the effects of hybrid use of micro glass fiber (GF), micro polypropylene fiber (PF) and macro steel fiber (SF) on the flexural capacity, energy absorption, ultimate load carrying, failure mode and ductility behavior of lightweight aggregate concrete (LWC) beamsreinforced with glass fiber reinforced polymer (GFRP) bars. A total of eight beams with a rectangular cross-section and 100 mm wide × 200 mm deep × 1500 mm long, were cast and tested up to failure under four-point bending. The correction factor (φ) calculated compared with American design codes of ACI 440.1R-06 and ISIS design manual No. 3. The φ factor for beams made of hybrid PF, SF into the LWC mixes (PSLWC) and reinforced with 0.9 ρ fb ; where ρfb is the balanced reinforcement ratio of the GFRPbars is approximately 1.38
The loads and reactions have been measured using a load cell of capacity 2000 kN and 0.1 kN accuracy. The load cell readings were recorded automatically using the data logger. The corresponding vertical deflections of test beams at the locations of the mid- span point were measured using LVDT's of 100 mm capacity and 0.01 mm accuracy. Electrical strain gauges of length 10 mm, with resistance 120.4 ± 0.4 ohm, and a gauge factor of 2.11 were used to measure the strains in the main longitudinal top and bottom flexural steel, vertical stirrups, and horizontal shear reinforcement. The gauges were fixed on the steel bars before casting. The surface of the steel was cleaned and smoothed, and the gauges were installed on the steel bars using adhesive material and then they were covered with a water proofing material for protection. For all beams, two gauges were fixed on the top bar at the interior support and on the bottom bar at the mid span. In addition, four gauges were fixed on two vertical stirrups and horizontal shear reinforcement at intersection points of these stirrups and horizontal reinforcement with the strut lines joining the point load with the internal and external supports. The load, deflections, and steel strains were measured and recorded automatically by connecting the load cell, LVDT's, and the electrical strain gauges to data acquisition system.
Load deflection curves of the tested beams are shown in Fig. 2. It is shown that as the ratio of longitudinal reinforcement increases and as the ratio of shear span-effective depth decreases, beam capacity increases. Fig. 2 also shows that beam capacity slightly increases as the concrete compressive strength increases. It is revealed that ratio of longitudinal reinforcement influences the type of failure and stiffness of the beams after the occurrence of the first flexural crack. In addition, in the case of beamsreinforced with GFRPbars, stiffness of the beams drastically decreases even though the beams have higher longitudinal reinforcement. This was due to low modulus elasticity of GFRPbars.
The present paper reports test results of nine two-span RC deepbeams . The tested variables were shear span-to-depth ratio, vertical web reinforcement ratio, horizontal web reinforcement ratio, and concrete compressive strength. The specimens were tested in a compression machine where increasing monotonic static loads were at each mid-span. All tested beams were loaded until failure. The failure planes evolved along the diagonal crack formed at the concrete strut along the edges of the load and intermediate support plates. The test results were measured at different loading levels for the mid-span deflection, mid- span bottom steel strain, middle-support top steel strain, middle-support stirrups strain, and end-support stirrups strain. Also, the cracking patterns were identified. The effects of testing variables on the first diagonal crack load, ultimate shear load, deflection, stiffness, and failure mechanisms were studied. Finally, the obtained test results are compared to the predictions of finite element analysis for continuousdeepbeams and a well agreement between the experimental and analytical results was found.
geopolymer concrete and this has been the key motivation of this undertaking. This study presents an investigation of the flexural response of geopolymer concretebeamsreinforced with sand-coated glass FRP (GFRP) bars subjected to four-point static bending test. Three full-scale beams with nearly same amount of bottom GFRPbars but with varying diameter were cast and tested. The crack patterns and failure modes, load versus deflection relationships, bending-moment and deflection capacities, and strains in the bars and geopolymer concrete are presented. Furthermore, the experimental flexural capacity of beams are compared with the predicted values using the current standards and with their GFRP- reinforcedconcrete (GFRP-RC) counterparts to verify the suitability of the proposed system for structural applications.
Abstract: This paper reports and compares experimental studies on flexural performance of concretebeamsreinforced with hybrid fiber reinforced polymer (FRP) and steel HRB bars with this study and other literatures. The objective of this study is to examine the effect of hybrid FRPs on structural behavior of retrofitted RC beams and to investigate if different sequences of BFRP and GFRPbars of the hybrid FRPs have influences on improvement of strengthening RC beams, Total 3 steel reinforcedconcretebeams and 8 hybrid reinforcedbeams were designed using only HRB steel bars and hybrid G/BFRP-steel bars respectively. The flexural bearing capacity, the maximum crack width and the deflection of the test beams were obtained and analyzed. Results show that the ultimate bending moment of hybrid reinforced is slightly less than that of steel reinforcedconcrete beam with the same reinforcement ratio. It can be concluded that it is feasible to replace the corner steel bars of concrete members with FRP bars without reducing the flexural bearing capacity. However, the deflection and maximum crack of hybrid reinforcedconcretebeams are much higher than those of steel reinforcedconcretebeams at the same load levels. The theoretical calculation method can effectively predict the flexural bearing capacity, crack spacing, maximum crack width and deflection of hybrid reinforcedconcretebeams, which can be used in engineering design reference.
performance. However, unlike slender beams, non- linear strain distribution is nominal in deepbeams. The direct compression strut formed between the load- ing point and support tends to increase shear strength. This created a distinctive failure mode compared to slender beams. In deepbeams, shear reinforcement controls the concrete strut and increases load-carrying capacity. Therefore, an increase in shear performance is expected by applying the high tensile strength of FRP shear reinforcement in deepbeams. To verify the performance of the proposed shear reinforcement, this paper aims to experimentally investigate the shear performance of GFRP plate shear reinforceddeepbeams. Also the strut-and-tie modeling approach used in the steel reinforcement was examined to see its validity for deep beam shear reinforced with GFRP plate.
analytical investigation of flexural behaviors of concretebeamsreinforced with glass-reinforced-polymer (GFRP) bars were studied. The GFRP rebar having the tensile strength of 902 MPa and Young’s modulus of 46 GPa. The beams were 1800 mm long with a rectangular cross section of 150 mm in width and 200 mm in depth. Totally Four beams were tested. One beam was reinforced with glass-FRP bars, two beams were reinforced with both glass-FRP bars and steel and one was reinforced with steel, serving as a control specimen. The beams were tested to failure in four-point bending over a clear span of 1600 mm. The test results were reported in terms of ultimate load carrying capacity, deflection and cracks. The experimental results were used to predict the load vs. deflection of Concretebeamsreinforced with hybrid bars. The measured load vs. deflections was analyzed and compared with the predicted FEM model using ABAQUS. The results indicate that the reaction forces and deflections obtained from the finite element model (FEM) were well matched with the experimental results.
Grace et al (1998) reported that continuously supported T-section concretebeamsreinforced with different combinations of longitudinal reinforcing bars and stirrups made of glass FRP (GFRP) and carbon FRP (CFRP) demonstrated the same loadcapacity as steel reinforcedconcretebeams but lower ductility and different failure modes. Continuously supported FRP reinforcedconcretebeams tested by Ashour and Habeeb (2008), and Habeeb and Ashour (2008) exhibited a small amount of moment redistribution, whereas El-Mogy et al. (2010) reported that moment redistribution in continuous FRP reinforcedconcretebeams is possible if the reinforcement configuration is suitably selected. More recently, Mahroug et al. (2014a&b) concluded that continuous CFRP and BFRP reinforcedconcrete slabs developed earlier and wider cracks and larger deflections compared with the counterpart steel reinforcedconcrete slab. It was also observed that combined shear and flexural failure was the dominant mode of failure for all continuous FRP reinforcedconcrete slabs tested. These investigations also showed that ACI 440 1R-06 equations can reasonably predict the loadcapacity and deflection of simply supported GFRPbeams but significantly underestimate deflections of continuously supported FRP reinforcedconcretebeams after first cracking.
The loadcapacity and behavior of a reinforcement concretedeep beam at each loading stage based on the geometric property of the section, steel arrangement, load and support condition. The current study used to inspect the structural response of continuous reinforcement concretedeep T-beamsreinforced with the carbon fiber reinforced polymer (CFRP) failed in shear. The study analyzed three concretedeep T- beams, these beams contain CFRP reinforcement and three concretedeep T- beams, these beams contain steel reinforcement for comparison. The deflection, failure mode, crack pattern also studied at analysis. the shear failure is predominant for all analysis T-beams. And the result shows when keeping the rate of the CFRP reinforcement constant and increasing a/d ratio substantially affects the shear strength and the collapse loads decreasing, also the CFRP reinforced T-beams can be showed the shear strength value higher than those of similar steel reinforced T- beams.
Ashour et al., (2004) tried 16 strengthened cement (RC) continuousbeams with various reinforcements of inner steel bars and outside CFRP covers. Every single test example had the same geometrical measurements and were ordered into three gatherings as per the measure of interior steel support. Every gathering incorporated one non-reinforced control beam intended to fizzle in flexure. Three types of failure modes were watched, to be peeling failure of the concrete cover, laminate rupture and cover detachment. The ductility of every single reinforced beam was diminished in examination with their particular reference beam. Moreover, rearranged routines for assessing the flexural loadcapacity and the interface shear stresses between the concrete and the adhesive material were displayed. As in past studies, they watched that expanding the CFRP sheet length did not counteract peeling failure of the CFRP laminates.
continuousbeams. It was observed that CSA/S806-02 design code progressively underestimates the deflections of FRP reinforcedcontinuousconcretebeams at loads higher than the cracking load. However, it has been reported that the deflection prediction by the CSA S806-02 equation showed very good agreement with the experimental results for three types (E-glass, C-glass and Z-glass) of GFRPbars (El- Gamal et al., 2010). Moreover, the equations given in CSA S806-02 were found to be the most accurate and conservative when used for calculating the deflection of CFRP reinforcedconcrete members (Carols et al., 2006). Ilker et al. (2012) studied the deflection of simple and continuousconcrete structures reinforced with FRP bars. Their study found that while Bischoff‟s model gives good predictions for simply supported FRP reinforcedconcrete beam deflections, it progressively underestimates deflections of continuous FRP reinforcedconcretebeams. Moreover, in another major study, Barris et al. (2009) found that the predicted deflections provided by the Bischoff approach showed good agreement with the experimental data. However, for additional levels of applied load, this theoretical approach underestimates the deflections. Habeeb and Ashour (2008) investigated the deflection prediction of simply and continuously supported GFRPreinforcedconcretebeams. They introduced a correction factor, G (=0.6) to the second term of the equation proposed
and complexity of manufacturing process. More practical solutions have been suggested such as; confinement of concrete in compression zone , addition of fibres to concrete [15-17] and use of a hybrid combination of FRP and steel re-bars [18-26]. Such hybrid reinforcement system shows improved serviceability and ductility, and enhancement of load-carrying capacity compared to traditional reinforcement [19,21]. In spite of the fact that the literature shows some research on simply supported beamsreinforced with hybrid FRP and steel rebars [18-25], none of these research projects was carried out to investigate the structural behaviour and failure modes of multi- span continuous hybrid reinforcedconcretebeams which are considerably different from those of simply supported ones. Therefore, concretecontinuousbeams are not well represented by statically determinate specimens tested in previous studies. For instance, the moment redistribution characteristics and the changes in the beam curvature from sagging to hogging do not exist in simply supported beams. Moreover, the majority of concrete structures in practice are multi-span continuous members.