Abstract: An experimental study of the shear behavior of recycledaggregateconcrete (RAC) beams with and withoutshearreinforcement is presented. Nine full-scale simply supported beams were loaded in four- point bending tests until failure. Three different replacement ratios of coarse natural with coarse recycledconcreteaggregate (0%, 50%, and 100 %), and three different shearreinforcement ratios (0%, 0.14%, and 0.19 %) were the main parameters. All natural aggregate concretes (NAC) and recycledaggregate concretes (RAC) were designed and experimentally verified to have similar compressive strength and workability. It was found that the shear behavior and the shear strength of the beams with 50% and 100% of recycledconcreteaggregate was very similar to that of the corresponding natural aggregateconcretebeams. The applicability of different code provisions for the shear strength predictions of the RAC beams with and withoutshearreinforcement was tested by comparison to test results obtained on 85 beams, 58 RAC and 27 corresponding NAC beams. The shear strength of RAC50 and RAC100 beams with and withoutshear
mm and a span length of 1770 mm, while the simply supported span was 1470 mm. A shear span to effective depth ratio of 3.5 was used. This study was found to be stimulating, as it fixated on something, which was quite different as compared to all other studies in the same scope. An assessment of the ability of crimped and hooked-end steel fibres to be used as minimum shearreinforcement in RC beams prepared with two different grades of concrete was completed. To accomplish this, the control samples were made from the beams, which were believed to be satisfactory. The fibre-reinforced beams also showed fluctuating degrees of multiple cracking at ultimate loads. The shear strength of the FRC beams was found to be more than a low value endorsed in the literature. The grade of concrete was found to be of little importance in this regard. A comparison of the strength of the two types of deformed fibres revealed that the beams reinforced with the hooked-end fibres were found to have up to 38% higher shear strength than the crimped fibres. A simple model for shear strength was also suggested for the calculation of the behaviour of fibre reinforced concrete. The proposed model was tested along with seven other shear strength models. The seven models were selected from the literature. The proposed model predicted fairly good values. However, a model proposed by other researchers from the selected literature was found to be projecting a better approximation. Imam et al. (1995) presented an analytical model for predicting the shear strength of reinforced high-strength concretebeams. The dimensions of all the specimens were constant and valued at 200 mm × 350 mm. All beams had span length of 3600 mm. All specimens were singly reinforced without stirrups. The author classified the beams into four groups based on three factors (a/d, V f , and ) in different levels. These beams
Generally reinforced concretebeams are designed for safety in order to resist higher compressive and shear force,but the sudden failure of reinforced concretebeams are due to shear. Hence beams wereprimarily designed for shear. Since shear failure is frequent and sudden with little or no advanced warning, the design for shear must ensure that the shear strength for every member in the structure exceeds the flexural strength. The shear failure mechanism varies depending upon the cross-sectional dimensions, the geometry, the types of loading, and the properties of the member. The shear failure is difficult to predict accurately despite extensive experimental research. Diagonal cracks are the main mode of shear failure in reinforced concretebeams located near the supports and caused by excess applied shear forces. Beams fail immediately upon formation of critical cracks in the high-shear region near the supports. Whenever the value of actual shear stress exceeds the permissible shear stress of the concrete used, the shearreinforcement must be provided to prevent the shear failure. Here we provided the shearreinforcement in form of stirrups.
Fibres are utilised in order to enhance the properties of an inherently brittle and crack-prone cement-based matrix. Para- metric studies on SFRC beams under monotonic loading were carried out by means of NLFEA. The latter were initially calibrated and verified against existing experimental data of Campione et al. (2006). The investigation is focused on simply supported beams, which were designed with reduced shearreinforcement in order to incorporate a shear mode of failure. The spacing between shear stirrups was increased (with the extreme case of beamswithout transverse stirrups being consid- ered as well), while fibres were added to examine their potential as a substitute for the loss in conventional shearreinforcement. Based on the findings of the present investigation, it can be concluded that the addition of steel fibres consistently enhances the load-carrying capacity. The strength increase was by up to ,15% compared to the control beam specimen (i.e. the one with no increase in stirrups spacing and no fibres). Furthermore, fibres were found to increase stiffness, leading to reduced deflections. This shows that there are clear benefits of adding fibres at both the serviceability and ultimate limit states, which are important design considerations. The addition of steel fibres also led to a reduction in crack formation and propagation. It has also
Fiber reinforced polymer (FRP) reinforcement in deep beams has been proposed as an alternative to steel reinforcement to increase the durability of members in corrosive environments. Since FRP reinforcement has lower stiffness than steel reinforcement and typically exhibits higher tensile strength, there is a need for new models capable of capturing the effect of these properties on the shear strength of deep beams. This paper proposes such an approach for members withoutshearreinforcement, which is an extension of a two-parameter kinematic theory (2PKT) for steel-reinforced deep beams. The original approach is modified to account for the effect of large flexural strains on the shear capacity of the critical loading zones in deep beams where the concrete crushes at failure. It is shown that a simple modification based on test data can result in adequate shear strength predictions. It is also shown that the extended 2PKT captures well the effect of reinforcement stiffness, shear-span- to-depth ratio, and section depth on the shear capacity of deep beams with FRP reinforcement.
Shear strength of RC beams is a debate subject of the century. Shearbehaviour of RC beams is a complicated mechanism. Many investigators through experiments have proposed theories on shear mechanism of RC beams. The shear in RC beamswithoutshearreinforcement is resisted by uncracked concrete, aggregate interlock across the cracks and the dowel action of longitudinal reinforcement. Percentage of reinforcement, compressive strength of concrete and effective depth of beam are important design parameters affecting the shear strength of RC beams. The expressions for shear strength in various standard codes of practice are empirical or semi empirical which consider the above parameters to predict the shear strength with appropriate safety and strength reduction factors.
Generally, the first crack suddenly developed in the flexural sagging region at approximately 25% of the ultimate strength, and then a crack in the diagonal direction at approximately 30% of the ultimate strength at the mid-depth of the concrete strut within the interior shear span immediately followed. The first flexural crack over the intermediate support generally occurred at approximately 80% of the ultimate strength. As the load increased, more flexural and diagonal cracks were formed and a major diagonal crack extended to join the edges of the load and intermediate support plates. A diagonal crack within the exterior shear span occurred suddenly near the failure load. Just before failure, the two spans showed nearly the same crack patterns. All tested beams developed the same mode of failure as observed in (Ashour et al. 2007). The failure planes were traced along the diagonal crack formed at the concrete strut along the edges of the load and intermediate support plates. Two rigid blocks separated from original beams at failure due to the significant diagonal cracking. The influence of shearreinforcement on the tested beams behavior was not significant as mentioned before in (Singh et al. 2006). In beam without stirrups (BS2), the failure was sudden and was due to crushing of the concrete compression struts. When sufficient stirrups are present, crack fans develop under the loads, and over the interior support; these cracks diminish the effective width of any direct compression strut which might develop.
Strut-and-tie models are often used for the design of shear critical deep members since they can rationalise the shear transfer within discontinuous or disturbed regions in RC structural elements. Most current codes of practice adopt the strut-and-tie method but provide very little guidance on how to select appropriate strut-and-tie layout and dimensions. Furthermore, the effectiveness factors used to account for the biaxial state of stresses in struts of deep beams are not reliable. This paper reviews the application of strut-and-tie models for the design of RC deep beams and evaluates current formulations of the effectiveness factor. Experimental and numerical studies are used to assess how the effectiveness factor is influenced by different parameters including concrete compressive strength, shear span to depth ratio and shearreinforcement ratio and to arrive at a more reliable strain based effectiveness factor. Various effectiveness factors are examined against an extensive database of experimental results on RC deep beams with and withoutshearreinforcement. The results show that the proposed effectiveness factor yields the most reliable and accurate predictions and can lead to more economic and safe design guidelines.
In comparison among types of FRP, GFRP possesses the lowest tensile strength but it has the advantage of being least expensive. However, this composite material has proven to have high strength and to be noncorrosive and lightweight relative to the conventional steel. Research works related to the use of GFRP bars to replace longitudinal steel bars have been performed [3-6]. Nevertheless, very little research has been conducted to study the shearbehaviour of FRP RC beams due to the difficulty in understanding its mechanism of failure. In addition, due to the incomparable strength of steel and FRP, different consideration of design concepts would affect the shear performance of the beam. Test results have shown that GFRP RC beamswithoutshearreinforcement failed in shear for over-reinforced beams, whereas beam in under-reinforced section failed in flexure with excessive deflection . Even, beam with GFRP stirrups failed in a flexure- shear mode, and it also indicate that as the amount of longitudinal bars increases the shear strength is also increased . Thus, according to previous study, further research is needed in understanding the shear performance of GFRP beams with different test variables.
In this study, the failure modes of BSM are governs by steel yielding before the concrete strain at the compression area reached the maximum permissible value of 0.0035 . For shearreinforcement, 2-legged steel stirrups of 8 mm diameter (mild steel) were spaced at 50 mm and 150 mm centre to centre at the shear region. These two kinds of spacing were calculated based on BS8110 code provisions in order to investigate the shear performance of the beams with minimum and adequate amount of stirrups. In each specimen, strain gauges were position at selected locations at longitudinal bars, stirrups and concrete which were labelled as X (see Fig. 1). The deflection of the beam was measured by at mid-span and two loading points.
Bentz, Vecchio & Collins (2006) observe that the shearbehaviour of reinforced concrete continues to be studied, and discussed as there is no agreed basis for a rational theory, and experiments cannot be conducted for concretebeams subjected to pure shear. Shear failures of PSC beam structures are potentially brittle and could occur without warning due to the low level of shearreinforcement which is often associated with these types of beams. This brittle and explosive nature of failure was evident in the testing of PSC beams within this study. This illustrates the increased importance of being able to accurately and safely predict the shear capacities and ductility of bridge beams.
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 shearreinforcement. 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 shearreinforcement 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.
In conventionally steel RC beams, there are different failure modes depending on the longitudinal and transverse reinforcement ratios and on the shear span to depth ratio. Changes in these failure modes are observed in the case of FRP RC beams with FRP stirrups due to the linear elastic behaviour of the FRP reinforcement. In conventionally RC beams, if the longitudinal reinforcement ratio is low, failure may be often due to a flexural-shear mechanism. Then, as described in , first of all flexural cracks initiate, and subsequently develop inclined through the web. As the load increases, damage concentrates around the so-called shear critical crack. After increasing the applied load, a second branch of the crack develops inside the concrete chord, eventually connecting the first crack and the point where the load is applied, producing failure. For this type of failure, the increment of tensile force in the longitudinal reinforcement due to the inclined crack, which depends on the shear force, will produce yielding of the longitudinal reinforcement. This is not the case for FRP longitudinal reinforcement, which is linear elastic up to failure, and which has an ultimate tensile strength higher than the steel yielding stress. In addition, designers are often required to use FRP longitudinal reinforcement ratios higher than the balanced reinforcement ratios to meet the serviceability criteria.
The experimental programme carried out for this research work consist of total five reinforced concretebeams with a size of 2000 x 200 x 270 mm. Nomenclature of all the tested beam is describe in Table 1. Beam section (2000 x 200 x 270 mm) was design such that it fails in shear only. It comprised of 5 bars of 12 mm diameter Fe-415 as tension steel and 2 anchor bars of 10 mm diameter. 6 mm 2- legged MS stirrups (150 mm x 220 mm out to out) at a spacing of 300 mm center to center distance were used as shearreinforcement. All the beams were casted in mould of size 2000 mm x 200 mm x 270 mm (in to in Dimensions). The moulds were fabricated from MS sheets of 4 mm thickness.
Bazant and Kim  in 1984 presented a statistical analysis of normal weight concretebeamswithoutshearreinforcement using data based on nonlinear fracture mechanics approach to represent the size effect in concretebeams. It was noted that nonlinear fracture mechanics approach predicts the test results more accurately than linear fracture mechanics approach as concrete exhibited brittle characteristics in failure (see Figure 2.25). According to Bazant and Kim, size effect in structure occurred due to the release of strain energy from the beam into the cracking zone as the cracking zone lengthens and hence, the increment size of the structure would lead to higher energy released. A cracking shear capacity (Eqn 2.54) were presented by Bazant and Kim to represent the size effect for diagonal shear failure of concretebeams element with longitudinal reinforcementwithoutshearreinforcement, which it is believed that the energy loss due to cracking is a function of both fracture length and of cracking zone area assumed to have a constant width at its front, proportional to the maximum aggregate size. The cracking shear stress of concretebeamswithoutshearreinforcement is predicted as follow:
The ingredient materials physical and mechanical properties used for casting HSFRC beams such as cement, fine aggregate, coarse aggregate and longitudinal reinforcement are taken as per IS code provisions. The type and shape of the steel fibers used for casting was straight and rounded with aspect ratio (l/d) of 75. To improve the workability of fibrous concrete naphthalene based super plasticizer Conplast337 was utilized. Natural pozzolonas such as, fly ash (Class F) acquired from Kothagudam thermal power station and Ground Granulated Blast Furnace Slag (GGBS) with physical requirements confirming to IS 12089 1987  procured from Vizag were utilized.
The beams in group D failed in shear. Initially, flexural cracks were observed at mid-span in the un-repaired beams at different loads based on the corrosion level: 61 kN (for non-corroded beam), 57 kN and 64kN (for low of 0.77% actual mass loss and high or 4.39% actual mass loss corrosion levels). The loads at which diagonal cracks initiated and propagated for the different beams are presented in Table 3.2. As the load increased, the diagonal cracks widened and the stirrups started to share in resisting the applied load and consequently the beam lost the aggregate interlock. The failure in the un-repaired corroded beams unexpectedly occurred in the non-corroded shear span possibly because the enhancement of shear friction due to the low achieved mass loss led to increasing the shear resistance in the corroded shear span. At the ultimate strength, the beams exhibited brittle shear failures. The failure modes were diagonal tension splitting failure in the control and the corroded beams as shown in Figure 3.21. The corroded beam with high corrosion level experienced stirrups rupture. However, the CFRP repaired beam experienced debonding of FRP with diagonal tension failure (Figure 3.21).
Mechanical strength of various grades of CC and RWGFA concrete results are obtained. The chemical properties of recycled waste glass fine aggregate are similar to the properties of sand and alumina is less than 1% in RWGFA. The behaviour of non absorption water, the mechanical properties of RWGFA concrete cubes are marginally higher strength than conventional cement concrete. The mechanical strength of cubes of seven days and twenty eight days are compared. It is shown in Figure 26 to 28. Flexural behaviour of various grade mix, RWGFA, CC beams are tabulated previously. Load deflection curves of are shown in diagrams. The failure patterns of the RWGFA concretebeams made with recycled waste glass and cement concretebeams made with river sand are shown and the crack pattern of RWGFA beams is similar to conventional cement concrete beam. The comparison of load deflection curve for RWGFA and CC beams are in Diagram 29.
Shear failure in reinforced concrete, also known as diagonal tension failure, is difficult to accurately predict. This remains the case despite decades of experimental research, the development of new behavioral theories, and the use of sophisticated analytical tools. The difficulty lies in the fact that shear failure is really the sum of several internal mechanisms of resistance acting within the concrete. These include the uncracked compression zone, aggregate interlock, dowel action, and residual tensile stresses normal to cracks. The uncracked compression zone is the portion of uncracked concrete that is still able to fully resist shear forces. Aggregate interlock refers to the internal friction generated at a crack due to surface roughness, and can account for over one third of the total shear force. Dowel action results from the vertical forces across the longitudinal steel (Nilson et al., 2004). Collins et al. (1996) demonstrated that cracked concrete possesses tensile stresses that can considerably increase the ability of concrete to resist shear forces.
The term ‘geopolymer’ was first introduced by Joseph Davidovits in 1978. He proposed that binder could be produced by a polymeric reaction of alkaline solution and the aluminium in source materials of geological origin or by-product materials such as fly ash. Because the chemical reaction take place in this case is a polymerization process, davidovits coined the term ‘geopolymer’ to the represent these binder. In this work, low calcium (ASTM CLASS F) fly ash with GGBS (ground granulated blast furnace slag) based geopolymer is used as the binder. Fly ash GGBS based geopolymer paste binds the loose coarse aggregate, fine aggregate and other un-reacted materials to form the geopolymer concrete with or without presence of admixtures. The manufacture of geopolymer concrete is carried out using the usual concrete technology methods. As in case of opc