Top PDF Influence of Shear Reinforcement on Reinforced Concrete Continuous Deep Beams

Influence of Shear Reinforcement on Reinforced Concrete Continuous Deep Beams

Influence of Shear Reinforcement on Reinforced Concrete Continuous Deep Beams

with a / h =1.0. The influence of shear reinforcement on the first flexural and diagonal crack loads was not significant (see Table 3) as also observed in simple deep beams given in appendix A. Just before failure, the two spans showed nearly the same crack patterns. All beams developed the same mode of failure as observed in other experiments 3 . The failure planes evolved 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 crack. An end block rotated about the exterior support leaving the other block fixed over the other two supports as shown in Fig. 3.
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Influence of shear reinforcement corrosion on the performance of under reinforced concrete beams

Influence of shear reinforcement corrosion on the performance of under reinforced concrete beams

Main reinforcement consisted of high yield (ribbed) bars with a nominal characteristic strength of 460 N/mm 2 . Shear reinforcement was 6mm di- ameter plain round mild steel bars of nominal cha- racteristic strength 250 N/mm 2 at a spacing of 65 mm. Cover was 50 mm to the shear reinforcement for the beams presented in this paper, as this also formed part of a larger investigation where the cover was varied. Two longitudinal hanger bars for the links were provided at the top of the beam cross sec- tion. These were 6 mm diameter plain round mild steel bars with a nominal characteristic yield strength of 250 N/mm 2 . The steel reinforcement was weighed before casting to enable the actual percentage corro- sion to be calculated at a later stage. In order to pre- vent corrosion in the main reinforcement, shrink wrap tubing was provided at the points of contact with the shear reinforcement to break the electrical circuit and hence prevent current flow to the main reinforcement during the accelerated corrosion process. Inspection of the main reinforcement at the end of the tests showed that this was an effective method of preventing accelerated corrosion of the main reinforcement.
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Influence of inclined web reinforcement on reinforced concrete deep beams with web openings.

Influence of inclined web reinforcement on reinforced concrete deep beams with web openings.

Details of geometrical dimensions and reinforcement used in test specimens are given in Table 1 and Fig. 3. The opening size and amount of inclined reinforcement were selected as the main variables to evaluate the relation of the effective inclined reinforcement factor and shear strength of deep beams with openings. Beams tested were classified into two groups according to the opening width: T-series and F-series for opening widths of 0 . 25 a and 0 . 5 a , respectively, where a indicates the shear span. The opening depth varied between 0 . 1 h and 0 . 3 h , where h indicates the overall depth of the beam tested. When the opening completely interrupts the natural load path joining the edges of load and support plates, the shear strength of beam is significantly reduced as indicated by Kong and Sharp 1 Mansur and Tan 12 . In each beam tested, the opening center was positioned in accordance with that of the shear span area. Inclined shear reinforcement was arranged in layers above and below openings, each consisting of three bars of 10 mm diameter. The angle of all inclined reinforcement was chosen to be 45° to the longitudinal axis of beams and placed symmetrically at the top chord above openings and bottom chord below openings. The effective inclined reinforcement ratio  od as calculated using the right hand side of Eq. (4) varied from 0.0 to
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Shear Behaviour of Reinforced Concrete Continues Deep Beams

Shear Behaviour of Reinforced Concrete Continues Deep Beams

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 shear reinforcement 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.
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Influence of Fiber Content on Shear Capacity of Steel Fiber Reinforced Concrete Beams

Influence of Fiber Content on Shear Capacity of Steel Fiber Reinforced Concrete Beams

Abstract: For shear-critical structural elements where the use of stirrups is not desirable, such as slabs or beams with reinforcement congestion, steel fibers can be used as shear reinforcement. The contribution of the steel fibers to the shear capacity lies in the action of the steel fibers bridging the shear crack, which increases the shear capacity and prevents a brittle failure mode. This study evaluates the effect of the amount of fibers in a concrete mix on the shear capacity of steel fiber reinforced concrete beams with mild steel tension reinforcement and without stirrups. For this purpose, twelve beams were tested. Five different fiber volume fractions were studied: 0.0%, 0.3%, 0.6%, 0.9%, and 1.2%. For each different steel fiber concrete mix, the concrete compressive strength was determined on cylinders and the tensile strength was determined in a flexural test on beam specimens. Additionally, the influence of fibers on the shear capacity is analyzed based on results reported in the literature, as well as based on the expressions derived for estimating the shear capacity of steel fiber reinforced concrete beams. The outcome of these experiments is that a fiber percentage of 1.2% or fiber factor of 0.96 can be used to replace minimum stirrups according to ACI 318-14 and a 0.6% fiber volume fraction or fiber factor of 0.48 to replace minimum stirrups according to Eurocode 2. A fiber percentage of 1.2% or fiber factor of 0.96 was observed to change the failure mode from shear failure to flexural failure. The results of this presented study support the inclusion of provisions for steel fiber reinforced concrete in building codes and provides recommendations for inclusion in ACI 318-14 and Eurocode 2, so that a wider adoption of steel fiber reinforced concrete can be achieved in the construction industry.
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Shear resistance of oil palm shell concrete beams with and without shear reinforcement

Shear resistance of oil palm shell concrete beams with and without shear reinforcement

Moody et.al [28 & 29] in 1954 presented experimental works on 40 NWC beams casted without shear reinforcement and 2 NWC beams casted with shear reinforcement, which were segregated into three series to observe the influence of the variables: (i) percentage of longitudinal and web reinforcement and method of anchorage, (ii) size and percentage of longitudinal reinforcement and cylindrical concrete strength and (iii) concrete mixture and method of curing. The concept of redistribution of internal stresses was introduced for the predictions of shear failure for NWC beams. For each of the 3 series, the sizes of the beams were different and the beams were tested with one or two concentrated load. It was observed that all beams failed in shear. It is observed that the shear capacity of the NWC beam specimens increased with the increment of concrete strength and percentage of longitudinal steel. It was also noted that the test results indicated that the beam strength tested at higher a/d ratio is governed by the first cracking load whilst the beam strength tested at lower a/d ratio is governed by the load, which caused destruction to the concrete compression zone. Hence, it is suggested by Moody et. al that instead of cracking load, ultimate load should be taken as the measured value for shear capacity.
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Behaviour and Analysis of Reinforced Concrete Continuous Deep Beams

Behaviour and Analysis of Reinforced Concrete Continuous Deep Beams

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 [11]. 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 shear reinforcement on the tested beams behavior was not significant as mentioned before in [14]. 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.
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Shear Strength of Reinforced Concrete Beams Without Stirrups

Shear Strength of Reinforced Concrete Beams Without Stirrups

Kotsovos 6 mentioned that tests on reinforced beams under a single point load indicated that diagonal failure of beams without shear reinforcement occurs closer to the support (Figure 3). It also proposed that the reasons for diagonal failure are related to the transfer of both longitudinal compressive force C, due to bending action and the shear force V to the support. Experimental results discovered that the mode of diagonal failure is affected by shear span to depth ratio, presence of shear reinforcement and amount of longitudinal reinforcement. It is also found that the compressive strength of concrete has little influence on the mode of diagonal failure.
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Behaviour of Reinforced Concrete Continuous Deep Beams in Shear

Behaviour of Reinforced Concrete Continuous Deep Beams in Shear

Figure 4 shows the cracking patterns at failure for the tested beams (BS1, BS4, and BS8) with (a/d) of 1.0, 0.77, and 1.25 respectively. In the figure, each crack is marked by a line representing the direction of cracking. The crack propagation was significantly influenced by the (a/d) ratio as shown in Fig. 4. Specimens with larger (a/d) showed earlier development of flexural cracks, and a less well defined shear cracks. 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 [13]. 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 shear reinforcement on the tested beams behavior was not significant as mentioned before in [13,14]. 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.
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Strength and Serviceability of Reinforced Concrete Deep Beams with Large Web Openings Created in Shear Spans

Strength and Serviceability of Reinforced Concrete Deep Beams with Large Web Openings Created in Shear Spans

Al-Bayati, et al., (2016) tested eleven simply supported reinforced self-compacting concrete deep beams under symmetrically two-point load to investigate the influence of the circular web openings on their behavior. Variables which were investigated involve the location of opening, opening size, the area of the transverse inclined reinforcement around openings and the shear span to effective depth ratio (a/d). In this study, all beams had the same overall dimensions, concrete compressive strength and flexural reinforcement. Based on the test results presented in this work it was concluded that, as the opening was positioned at the center of the shear span, the behavior of the beams was significantly influenced regardless the value of the (a/d) ratio and the opening size. Also it was found that, when the opening of a large diameter shifted away from the load path either to the top or to the bottom regions of the beam, the cracking and ultimate loads were dramatically reduced [9].
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Experimental investigation on the shear behaviour of concrete beams reinforced with GFRP reinforcement bars

Experimental investigation on the shear behaviour of concrete beams reinforced with GFRP reinforcement bars

In this study, the comparison was made between the shear performance of steel and GFRP RC beams which identified as BSM and BGM respectively. Totally sixteen RC beams were designated with different amount and types of longitudinal reinforcement bars, a/d and steel stirrup ratios (refer Table 1). Eight specimens were longitudinally reinforced with 16 mm diameter of steel bars, while another eight specimens reinforced with 16 mm diameter of GFRP bars. The beam dimension was 200 mm wide, 400 mm deep with 2000 mm and 3000 mm long due to two types of shear span length (a = 550 mm and 1100 mm). The beams were designed accordingly to available design codes and guidelines in the literature [8-10]. Two design codes of “Structural Use of Concrete – BS8110- 1:1997” and “Building Code Requirements for Structural Concrete and Commentary – ACI 318-08” were used for the design of steel RC beams. Since the designation of FRP reinforced concrete beams are slightly differ from conventional beams, the code provisions according to the “Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars – ACI 440.1R-06” was used.
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Improvement of ductility in shear failures of reinforced concrete deep beams by diagonal confinement.

Improvement of ductility in shear failures of reinforced concrete deep beams by diagonal confinement.

In simulation of beams, the Load-Deflection curves are obtained to study the comparative effect of inclined strut confinement. The maximum deflection at mid span is tracked & plotted to its respective applied load. Plain concrete beams are compared with beams having only flexure reinforcement & with beams having inclined confined strut with flexure reinforcement. After a few simulations on 350mm deep beam, it has been observed that a wire of 2mm diameter with 25mm pitch & also with 50mm pitch does not have significant effect on ductility compared with 8mm diameter wire as shown in Fig.4. Similarly the wire of 12mm diameter with 50mm pitch does not have any significant effect on ductility as shown in Fig.8. Hence for further simulations of 500mm, 750mm & 1000mm deep beams, wires of 2mm & 12mm diameter have not been used. Fig.4, Fig.5, Fig.6 and Fig.7 shows the load versus deflection curves for beams of depth 350mm, 500mm, 750mm & 1000mm respectively.
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Structural Behavior of Concrete Flange Continuous Deep Beams with Carbon Fiber Reinforced Polymer (CFRP)

Structural Behavior of Concrete Flange Continuous Deep Beams with Carbon Fiber Reinforced Polymer (CFRP)

The beams are set in three groups as shown in Table 1, the group of steel reinforced represent by symbol RC and the carbon fiber reinforced represent by CFRP. Three type of shear span to depth (a/d) ratio were applying on the experiment beams (1.0, 1.25, and 1.5) and concentrated loads were placed at mid-span of the beam.

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Behavior and Analysis of Self-Consolidated Reinforced Concrete Deep Beams Strengthened in Shear

Behavior and Analysis of Self-Consolidated Reinforced Concrete Deep Beams Strengthened in Shear

Copyright © 2012 Kh. M. Heiza et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In this study, a new shear strengthening technique for reinforced self-compacting concrete (RSCC) deep beams was suggested and compared with some traditional techniques. An experimental test program consists of sixteen specimens of RSCC deep beams strengthened by different materials such as steel, glass, and carbon fiber reinforced polymers (GFRP and CFRP) was executed. Externally bonded layers (EBLs) and near-surface mounted reinforcement (NSMR) were used as two different techniques. The effects of the new technique which depends on using intertwined roving NSM GFRP rods saturated with epoxy were compared with the other models. The new technique for shear strengthening increases the load capacity from 36% to 55% depending on the anchorage length of GFRP rods. Two-dimensional nonlinear isoperimetric degenerated layered finite elements (FEs) analysis was used to represent the SCC, reinforcement, and strengthening layers of the tested models. The analytical results have been very close to the experimental results.
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Experimental investigation on the shear behaviour of concrete beams reinforced with GFRP reinforcement bars

Experimental investigation on the shear behaviour of concrete beams reinforced with GFRP reinforcement bars

In this study, the comparison was made between the shear performance of steel and GFRP RC beams which identified as BSM and BGM respectively. Totally sixteen RC beams were designated with different amount and types of longitudinal reinforcement bars, a/d and steel stirrup ratios (refer Table 1). Eight specimens were longitudinally reinforced with 16 mm diameter of steel bars, while another eight specimens reinforced with 16 mm diameter of GFRP bars. The beam dimension was 200 mm wide, 400 mm deep with 2000 mm and 3000 mm long due to two types of shear span length (a = 550 mm and 1100 mm). The beams were designed accordingly to available design codes and guidelines in the literature [8-10]. Two design codes of “Structural Use of Concrete – BS8110- 1:1997” and “Building Code Requirements for Structural Concrete and Commentary – ACI 318-08” were used for the design of steel RC beams. Since the designation of FRP reinforced concrete beams are slightly differ from conventional beams, the code provisions according to the “Guide for the Design and Construction of Structural Concrete Reinforced with FRP Bars – ACI 440.1R-06” was used.
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Effectiveness of Web Reinforcement around Openings in Continuous Concrete Deep Beams.

Effectiveness of Web Reinforcement around Openings in Continuous Concrete Deep Beams.

on a theoretical analysis of simply supported deep beams using strut-and-tie model. However, the influence of web reinforcement around openings on the load capacity of continuous deep beams would be dissimilar to that of simple deep beams. Experimental studies 12-14 showed that the failure mechanism and load capacity of continuous deep beams are different from those of simple deep beams owing to the coexistence of high shear and high moment in interior shear spans and the development of tensile strains in both longitudinal top and bottom reinforcements. This would cause a significant reduction in the effective strength of concrete struts that are the main load transfer element in deep beams.
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Finite element analysis of reinforced concrete deep beams strengthened 
		in shear with CFRP

Finite element analysis of reinforced concrete deep beams strengthened in shear with CFRP

A paper presents a numerical analysis using ANSYS finite element program to develop a model for expecting the performance of seven lightweight aggregate reinforced concrete deep beams with 28 days compressive strength 26MPa and density of 1950Kg/m 3 strengthened in shear by externally bonded CFRP. All beams have same dimensions (150mm width, 400mm depth and 1400mm length), longitudinal steel reinforcement ratio ρ=0.0115 and shear steel reinforcing 5@100mm. CFRP strips 50mm width are used for strengthening. The effective variable parameters were: a/d ratio, CFRP spacing, orientation and number of layers. The results obtained from the ANSYS finite element model got good agreement when compared to the experimental results [1] which were done for the same deep beams with the same material properties, internal reinforcement and strengthening schemes. The results show that the ultimate load and deflection predicted by numerical analysis is less than experimental results by 9% and 5.7% in average respectively. By using CFRP strips in shear strengthening, the ultimate load has increased by 18%, 13.6%, 32% and 27.3% for vertical, horizontal, inclined and double vertical layers, respectively for a/d=1. For a/d =0.8 the increase is 10% for vertical strips. It is recommended that the CFRP is placed such that the principal fiber orientation is either normal to the longitudinal beams axis or normal to the line joining the applied load and supports (strut path) to resist higher tensile stresses and strains distributed along it.
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Shear Strengthening of Self-Compacting Reinforced Concrete Deep Beams With External Bonded Layers

Shear Strengthening of Self-Compacting Reinforced Concrete Deep Beams With External Bonded Layers

Increasing the shear strength of Reinforced self-compacting concrete RSCC deep beams may be required in many cases such as changing of building use, the need to perform an opening in deep beams for air conditioning, corrosion of reinforcement and finally due to construction or design errors. A very limited amount of experimental data exists on strengthening of RC deep beams in shear [22]. Strengthening using advanced composite materials such as fiber-reinforced polymer (FRP) rods, strips or woven wraps are being increasingly recognized for enhancing flexural and shear strength of concrete members instead of the traditional materials represented by steel bars or strips [21.22]. Repair and strengthening of structural members with composite materials, such as carbon, glass, kevlar and aramid fiber-reinforced polymers, have recently received great attention [23.24]. Reduced material costs, coupled with labor savings inherent with its lightweight and comparatively simple installation, its high tensile strength, low relaxation, and immunity to corrosion, have made FRP an attractive alternative to traditional retrofitting techniques. Field applications over the last years have shown excellent performance and durability of FRP-retrofitted structures [23.24]. Nowadays, carbon and glass fiber strips, rods and wraps woven in one or multi- directions are widely used as strengthening materials.
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Evaluation of shear behavior of deep beams with shear reinforced with GFRP plate

Evaluation of shear behavior of deep beams with shear reinforced with GFRP plate

performance. However, unlike slender beams, non- linear strain distribution is nominal in deep beams. 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 deep beams, 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 deep beams. To verify the performance of the proposed shear reinforcement, this paper aims to experimentally investigate the shear performance of GFRP plate shear reinforced deep beams. 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.
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Two-Parameter Kinematic Approach for Shear Strength of Deep Concrete Beams with Internal FRP Reinforcement

Two-Parameter Kinematic Approach for Shear Strength of Deep Concrete Beams with Internal FRP Reinforcement

Deep reinforced concrete beams with small shear-span-to-depth ra- tios (a = d ≤ approximately 2.5) are often used to support heavy loads in bridges and other types of public infrastructure. Concerns about the durability of such structures owing to corrosion of their steel reinforcement resulted in a search for alternative solutions. One such solution, which in the last decade has been a focus of significant research activity, is the use of internal fiber-reinforced polymer (FRP) reinforcement. Compared to conventional steel reinforcement, FRP bars are not susceptible to chloride-induced corrosion and typically have higher tensile strength. At the same time, FRP reinforcement exhibits lower modulus of elasticity and brittle-elastic behavior. These properties raised questions of whether conventional methods for the design and analysis of deep beams require modifications, and whether new approaches can offer improved predictions of the shear behavior of beams with FRP reinforcement.
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