Shear Behavior Of Reinforced Concrete Beams Research Articles

Mesoscale modelling on shear behavior of RC beams at low temperature: Influences of structural size and shear span-to-depth ratio

The low-temperature brittle failure of materials could aggravate the brittle characteristics of shear failure of RC beams, which urgently needs scientific research. This paper aims to investigate the shear behavior and corresponding size effect of reinforced concrete (RC) beams at low temperature by numerical analysis. Firstly, a two-stage thermo-mechanical coupled mesoscale simulation method was developed, which considered the meso-structure characteristics of concrete as well as the ice-strengthening effect. Based on the mesoscale simulation method validated through a series of tests, the progressive shear failure process of RC beams at room and low temperatures was captured. The influences of temperature (T = 20, −30, −60 and −90 °C), structural size (cross-sectional height H = 300, 600, and 1200 mm) and shear span-to-depth ratio (a/h0 = 1.0, 1.6, and 2.3) on key indexes of shear behavior were quantitatively analysed. The results indicate that compared to that at room temperature, the shear failure process of RC beams at low temperature is more rapid, exhibiting more obvious brittle characteristic. When the temperature drops from 20 °C to −90 °C, the nominal shear strength of RC beams is enhanced with a maximum increase of 57.0 % (for H = 300 mm) while the mid-span displacement is reduced with a maximum decrease of 46.8 % (for H = 300 mm). Compared to that at room temperature, the size effect on nominal shear strength of RC beams at low temperature is enhanced, with a maximum increase of 20.4 %. Finally, considering the influences of low temperature and shear span-to-depth ratio on the nominal shear strength, an improved size effect analytical model for was established, which can predict the shear capacity of different sized RC beams at low temperatures. This paper can provide a reference for the safe application of reinforced concrete structures in low temperature environments, and lay a foundation for the formulation of reinforced concrete structure design specifications at low temperature.

Experimental study of the influence of inclined pre-cracks on shear behavior of RC beams without transverse reinforcement

Extended growth of existing cracks in reinforced concrete (RC) structures may negatively impact structural performance and cause great risks to structural safety. However, the influence of inclined pre-cracks on shear behavior of RC structures as well as the mechanism behind it are still unclear. In this paper, an experimental investigation is conducted in order to study the correlation between inclined pre-cracks and the shear behavior of RC beams without transverse reinforcement. Eight beams with identical geometric designs and different pre-cracking conditions were categorized into four series and successfully tested: (i) reference beams without pre-cracks, (ii) beams with pre-cracks in the bending span induced via loading, (iii) beams with pre-cracks in the shear span induced via loading, and (iv) beams with artificial pre-cracks in the shear span. The deformation and strain fields were measured by digital image correlation (DIC) technique with a strong focus on the shear-transfer mechanism and cracking propagation. The obtained results reveal that inclined pre-cracks in the bending span may not develop into the critical shear crack (CSC) and exert minor effects on the shear capacity. In contrast, pre-cracks near supports within the shear span tend to develop into the CSC and influence its path and kinematics. This further affects the activation of arch action and aggregate interlock, ultimately resulting in a 3–24% reduction in the load-bearing capacity of this series compared to the reference beams. To summarize, this study reveals the relationship between inclined pre-cracks and shear behavior of RC structures, providing new insight for assessment.

Verification and Parametric Analysis of Shear Behavior of Reinforced Concrete Beams using Non-linear Finite Element Analysis

Many researchers have tackled the shear behavior of Reinforced Concrete (RC) beams by using different kinds of strengthening in the shear regions and steel fibers. In the current paper, the effect of multiple parameters, such as using one percentage of Steel Fibers (SF) with and without stirrups, without stirrups and steel fibers, on the shear behavior of RC beams, has been studied and compared by using Finite Element analysis (FE). Three-dimensional (3D) models of (RC) beams are developed and analyzed using ABAQUS commercial software. The models were validated by comparing their results with the experimental test. The total number of beams that were modeled for validation purposes was four. Extensive parametric analysis has been carried out on another twelve beams to explore the influence of specific parameters, such as using different strengths of concrete, different flexural reinforcement bars, and laminate in the shear regions. It is concluded from the results that when a different compressive strength was assigned to RC beams, a decrease by 31 of beam ultimate strength was recorded when using C25 concrete strength. On the other hand, an improvement of 29% was observed by assigning concrete compressive strength C50. As well as another decrease of 18 and 26 kN was observed when GFRP was used with beams that had stirrups and beams that had both stirrups and SF. However, the beams recorded a higher number for ductility with using GFRP. In addition, using laminate with the beam that had both stirrups and SF was not beneficial; hence, the failure load was increased by only 3%, particularly with the beam that had both stirrups and SFs

Shear behavior of RC beams strengthened with high-strength steel strand mesh reinforced ECC: Shear capacity, cracking and deformation

An experimental and theoretical study on the shear behavior of reinforced concrete (RC) beams strengthened with high-strength steel strand mesh reinforced engineered cementitious composites (HSSM-ECC) was reported in this paper. Four-point bending test was performed on a total of ten strengthened beams and three referential beams, considering the test variables of the shear-span ratio, the reinforcement ratio and diameter of HSSM, the water-binder ratio and thickness of ECC layer, and strengthening configuration. Test results showed that the shear performance of the strengthened beams was significantly enhanced, and the multi-cracking pattern was observed in the strengthened beams, which effectively reduced the crack width and the brittleness of RC beams in shear. In addition, the effect mechanism of test variables on the shear behavior of strengthened beams was discussed in detail. Finally, considering the effects of dowel action of longitudinal rebars and flexural-shear combination, a comprehensive analysis model for predicting shear capacity, shear deformation, and maximum shear crack width based on modified compression field theory was proposed, which was found to be acceptable for more accurate prediction of shear capacity, shear deformation, and maximum shear crack width of strengthened beams by comparing with the test results and other existing models.

SHEAR BEHAVIOUR OF REINFORCED-CONCRETE BEAMS INCORPORATING IRON FILINGS AS SAND REPLACEMENT

This study examined the influence of partial sand replacement with iron filings on the mechanical and physical characteristics of concrete, as well as conducted experimental tests of the shear behaviour of reinforced-concrete beams. Four replacement rates were used in this study, i.e., 5 %, 10 %, 20 %, and 30 % with a reference mixture containing no iron filings. At ages 7, 14, and 28 days, mechanical property tests (slump, density, ultrasonic pulse velocity, compressive strength, and splitting strength tests) were conducted. In addition, the shear behaviour of five reinforced-concrete beams with the same replacement rates (0 %, 5 %, 10 %, 20 %, and 30 %) were experimentally tested. Tests were conducted to determine the ultimate load failure, final deflection, energy absorption, stiffness, ductility index, compressive stress, and crack formations. According to the results, the correlation between the slump test and iron filings is positive; however, that for absorption is negative. With a higher percentage of iron-filing replacement, the density and ultrasonic pulse velocity increased. For specimens with 30,00 % iron filings, the densities, pulse velocities, and slumps were raised by 6,27 %, 2,44 %, and 58,33 %, respectively, compared to the reference specimens, whereas the absorption rate decreased by 20,00 %. Having 20,00 % iron filings produced the maximum compressive and splitting strengths of 28,00 %, which was 4,60 % higher than the reference mixture, whereas 30,00 % iron filings produced the highest flexural strength, which was 9,50 % higher than the reference mix. The findings of beam testing revealed that increasing the iron-filing content in concrete beams increased the final failure load, final deflection, ductility index, and energy absorption by 6,70 %, 10,29 %, 11,30 %, and 35,00 %, respectively. The initial and secant stiffnesses decreased at rates of 12,60 % and 3,10 %, respectively.

Structural performance of RC beams with openings shear strengthened by hybrid techniques (EBR/EBRIG)

Creating the openings in the existing reinforced concrete (RC) beams causes sudden deterioration, especially in the shear zone. This study investigates the effectiveness of a novel strengthening technology using externally reinforced fibre-reinforced polymer (FRP) strips in groves (EBRIG) on the shear behaviour of RC beams, compares it to that of externally reinforced (EBR) strips, and uses hybridisation between them to address the weakness brought on by the presence of an opening in the shear zone. Also, an innovative anchorage mechanism is suggested and studied to postpone the beginning of the strengthening system’s debonding. The strengthening material used in this research is glass fibre-reinforced polymers (GFRPs). For this study, 11 RC beams with an opening and a control beam without an opening, each measuring 120 × 300 × 2600 mm in size, were cast and subjected to the four-point loading test. All test beams had the same geometry and reinforcement details. The effect of the following parameters was investigated in this study: the dimension of the opening (square ‘150 × 150’ or rectangle ‘100 × 300’ mm), the strengthening technique used (externally bonded reinforcement [EBR], EBRIG and hybrid technique ‘EBRIG + EBR’) and the wrapping configuration of the strengthening (fully warped strips or U-shaped sheets with anchors). All techniques used raised the efficiency of shear resistance to approximate the fading effect of the opening, especially the technique of hybridising EBRIG and EBR. All strengthened beams showed an increase in the ultimate shear capacity ranging from 74% to 142% compared with the reference beams with the opening. The EBRIG technique shows numerous advantages over the EB system and can employ the strength of FRP materials. It also deals with the problems of weather factors that were facing EBR, and this is because of the covering that protects in the EBRIG technique. The technique to hybridize EBRIG and EBR was more effective at withstanding shear.

Predicting the shear behavior of reinforced concrete beams with Fe-Based shape memory alloy stirrups

Existing studies using Fe-based shape memory alloys (SMAs) for shear reinforcement have focused on strengthening aged structures. Studies on using Fe-SMAs as shear reinforcements for new structures have not been reported. Accordingly, this study performed experiments to evaluate the shear behavior of reinforced concrete (RC) beams with Fe-based SMA stirrups. Ten specimens were prepared for the experiments. The activation of the Fe-SMA stirrup, stirrup spacing, and shear span-to-depth ratio were considered as variables. The Fe-SMA stirrups were activated via electrical resistance heating. Activating the Fe-SMA stirrups applied compressive forces to the specimen, reduced the occurrence of diagonal shear cracks, and improved shear stiffness. However, it did not significantly affect the shear strength. The shear contribution of the Fe-SMA stirrup increased with an increase in the shear span-to-depth ratio and amount of shear reinforcement. In addition, the simulation results using the modified compression field theory (MCFT)-based section analysis model were consistent with the experiment results. Therefore, the model can predict the shear behavior of RC beams with Fe-SMA stirrups.

Experimental study and analysis of RC beams shear strengthened with FRP/SMA composites

In practice, the prestressing is difficult to apply to achieve shear reinforcement of reinforced concrete (RC) beams due to the limited operating space used for installing mechanical tensioning equipment. So, how to efficiently introduce prestressing into RC beams is a practical problem. In this study, the authors utilized the recovery effect of shape memory alloys (SMA) wires to successfully introduce prestressing into RC beams and externally bonded with fiber reinforced polymer (FRP) sheets, forming a FRP/SMA composite shear reinforcement technology. After that, shear behavior of RC beams strengthened with FRP/SMA composites was investigated by a series of experiments. In order to further illustrate the effect of FRP/SMA composite shear reinforcement on RC beams, other reinforcement materials, such as SMA wires and FRP sheets, have also been separately applied in shear reinforcement experiments. Moreover, carbon fiber reinforced polymer (CFRP) and basalt fiber reinforced polymer (BFRP) are respectively applied to prepare FRP/SMA composites. For beams strengthened with FRP/SMA composites, the prestressing generated by the recovery effect of SMA wires can effectively suppress the formation of diagonal cracks in RC beams. The ultimate load and the corresponding displacement of strengthened beams significantly increased due to the constraint effect of FRP on the propagation of shear cracks. The shear capacity of CFRP/SMA composites strengthening beams was higher than that of BFRP/SMA composites strengthening beams, as CFRP/SMA composites better limited the propagation of cracks. Based on the test results, an analytical model has been proposed to predict the shear capacity of strengthened beams, and its effectiveness has been confirmed through comparison with experimental results.

Contribution of steel fibers to the flexural and shear behavior of RC beams damaged by alkali‐silica reaction

AbstractThe study of damage processes in concrete and their effects on the residual properties represents a key point related to the service life of reinforced concrete (RC) structures. The use of steel fibers in RC beams mainly improves the cracking control and the shear bearing capacity. Considering the shear behavior, the presence of fibers not only leads to partial or total substitution of secondary reinforcement, but they can also result in a modification of the failure behavior from a shear failure (brittle) to a bending (ductile) one. The contribution of fibers on flexural and shear behavior of sound and damaged RC beams was investigated using alkali‐silica reaction as a damaging tool. First, the evolution of deformations and cracks were measured on creep tests of RC beams with and without fibers and reactive aggregates. Second, the flexural and shear behavior of damaged and undamaged beams incorporating steel fibers were compared. Results showed that alkali‐silica reaction damage can provoke a reduction of RC beam ductility, while the flexural strength is preserved. Regarding shear, it was observed that even in damaged concrete, fibers were able to control the crack propagation and increase the bearing capacity.

Structural behavior of reinforced geopolymer concrete beams – A review

A potential novelconstructionmaterial that is relativelyeco-friendly in manufacturing and has a comparatively low carbon footprint is geopolymer concrete (GPC). GPC is a largely unexplored topic in the literature due to its novelty as a material, particularly in terms of itsstructural behaviour. Reinforced concrete (RC) beams are the most common concrete application in the construction industry. Therefore, this review study intends to provide a greater understanding of GPC by summarizing and discussing the most updated data on the structural performance of reinforced geopolymer concrete (RGPC) beams. The evaluation highlights the flexural and shear behaviour of RC beams made with GPC and compared with those of ordinary Portland cement concrete (OPCC). The reported literature demonstrated that the structural behaviour of RGPC beams is comparable to that of conventional OPCC beams. Further, the failure mode of RGPC beams in flexure and shear was nearly identical to that of OPCC beams. Review of the literature showed that GPC beams might be employed safely with the existing standards. However, to assure its viability in the industry, full-scale investigations on the structural behaviour are required for mass use in a variety of application areas and to promote cleaner and sustainable choices in the construction industry. Overall, this review offers guidance for researchers and civil engineers in conducting future studies on GPC.

Experimental Study of the Shear Behavior of RC Beams Strengthened with High-Performance Fiber-Reinforced Concrete

In this study, the efficacy of strengthening of reinforced concrete (RC) beams in shear by utilizing high-performance fiber-reinforced concrete (HPFRC) was explored. The shear strengthening was achieved by epoxy bonding of prefabricated HPFRC strips or plates onto the beams. The beams were strengthened utilizing two different strengthening schemes: (i) plates side strengthening (ii) vertical strips applied at shear critical sections. The behavior of the two configurations was compared to the behavior of non-shear reinforced and shear-reinforced RC beams. The high-performance concrete (HPC) utilized contains 1.5% of steel fibers per volume of HPC mortar and is known as HPFRC. Parameters determined were the flexural strength and compressive strength of HPFRC mortar. The obtained results revealed that HPFRC realized a 28-day flexural strength of 20 MPa and a compressive strength of 108 MPa. Moreover, HPFRC strengthened RC beams experienced an increased in strength capacity of about 50% for plates and 36% for vertical strips compared to the RC beams with no stirrups. The results for HPFRC strengthened beams with plates were superior compared to those of the stirrup-reinforced beams, whereas the results of HPFRC strips strengthened beams were almost identical to the stirrup-reinforced beams. Also observed, was an improvement in the ductility of the beams with the best results achieved when employing HPFRC plates and strips.

Predicting shear behavior of reinforced-concrete beams shear-strengthened using near-surface mounted fiber-reinforced polymer method

This paper presents analytical research results to predict the shear behavior of reinforced concrete (RC) beams shear-strengthened with near-surface mounted (NSM) FRP. In this study, a section analysis method based on the modified compressive field theory (MCFT) was proposed to predict the shear behavior of RC beams shear-strengthened with NSM FRP reinforcement. The analytical method was applied to derive the analytical effective strain of the FRP shear reinforcement of 71 specimens collected from the existing literature. Then, the correlation between this analytical FRP effective strain and the major variables for shear strengthening design was analyzed through nonlinear regression analysis. From the results, a model capable of predicting the effective strain of NSM FRP reinforcement was finally proposed. This FRP effective strain model predicted the effective strain of NSM FRP reinforcement more accurately compared to models proposed by other researchers. In addition, the section analysis method using this model predicted the shear behaviour of other researchers beams shear-strengthened with NSM FRP reinforcement very well.

Mechanism of shear strengthening for RC beam by drilling web openings based on experiment and 3D RBSM analysis

In practice, web openings are usually drilled in reinforced concrete (RC) beams to accommodate pipes and cable installations. But introducing web openings always causes shear degradation of RC beams. This study aims to establish a rational position design of multiple small web openings, which can improve the shear behavior of RC beams, by controlling the path of critical diagonal crack. Three-point bending tests on four RC beams without and with web openings (shear span depth ratio: 2.59 and 3.56) were firstly carried out to evaluate the strengthening effect attributed to the proposed placement of web openings. Besides, the Three Dimensional Rigid-Body-Spring Method (3D RBSM), a discrete numerical methodology, was applied to simulate the test process, and the strengthening effect due to the placement of web openings was parametrically investigated. Finally, the decoupling of shear components (beam and arch actions) was conducted to comprehensively understand the shear strengthening mechanism due to drilling web openings, by using RBSM-based methodology. The test and numerical results confirmed that the proposed position design of web openings could evidently improve the shear strength and deformation ability of RC beams, because the multiple web openings could increase the angle of critical diagonal crack, by predetermining it propagation path. Moreover, it was clarified that the strengthening mechanism of shear behavior owing to web opening setting was dependent on the more dramatic development of arch action with the increasing angle of critical diagonal crack. The present paper provided a rational design to solve the problem of shear degradation caused by small web openings in the field of concrete member design, and proved a possibility to strengthen the shear behavior of existing concrete beams by drilling web openings.

Prediction of shear strength of CFRP-strengthened reinforced recycled aggregate concrete beams using various strengthening methods

Fibre reinforced polymer (FRP) strengthening is a possible option when the load carrying capacity of a structure needs to be increased for various reasons. On the other hand, the focus nowadays aims to save the environment by reducing the waste material. A suggestion was made to use waste concrete as an aggregate. If this new material was used more, it would be possible to use recycled concrete aggregate (RCA) and carbon fibre reinforced polymer (CFRP) to strengthen reinforced concrete (RC) structures and make them more environmentally friendly. An experimental investigation study on the shear behaviour of RC beams strengthened with CFRP strips was carried out. Tests were conducted on six reinforced concrete beams, with variations in the replacement ratio of RCA and strengthened by different configurations of CFRP under four-point loading. The results indicated that the load carrying capacity was increased, on average, by 18.09 and 35.04% for beams strengthened with CFRP with an inclined strip (IS) and continuous strip (CS) configurations respectively. The results also indicated that the increases in the stiffness were 21.08 and 37.31 for beams strengthened with CFRP in the IS and CS configurations, respectively. In addition the ductility of the beams increased after strengthening.

Experimental and theoretical analysis on shear behavior of RC beams reinforced with GFRP stirrups

The objective of this paper is to experimentally study the shear behavior of reinforced concrete (RC) beams reinforced with glass fiber reinforced polymer (GFRP) stirrups. Six specimens including five RC beams reinforced with GFRP stirrups (GFRP-S-RC beams) and one beam strengthened with steel stirrups (RC beam) are fabricated. The effects of several parameters (i.e., stirrup type, the shear span ratio, and stirrup spacing) on the failure modes, shear crack width, shear capacity, strain variation of stirrup and longitudinal rebar, and the mid-span deflection are investigated. Similar to the conventional RC beam, three different types of shear failure modes including the shear compression failure, the diagonal compression failure, and the diagonal tension failure are observed on the GFRP-S-RC beams. The shear capacity of GFRP-S-RC beams decreases as the shear span ratio or stirrup spacing increases. GFRP stirrups exhibit a slight opposite effect on the shear capacity. The average and maximum strain of the stirrup both increase as the shear span ratio increases. The increase in the shear span ratio and the stirrup spacing adversely affects the ultimate deflection and longitudinal steel strain. A modified formula for the allowable strain of FRP stirrup is proposed. Considering the effect of uneven stress of stirrups, a model for predicting the shear capacity of GFRP-S-RC beams is proposed, and it shows good agreement with various test data.

Flexural and shear strengthening of reinforced concrete beams using FRP composites: A state of the art

During the past few decades, strengthening and rehabilitation of reinforced concrete (RC) structures using fiber reinforced polymer (FRP) composites have been considered one of the most promising techniques to achieve the required strengthening and structure life span. Old structures require maintenance and repair because of harsh environments, natural disasters, changes in applied loads, corrosion of reinforcement, and poor maintenance. Many studies have been carried out on flexural and shear strengthening of RC structures using different FRP materials under different schemes. Externally bonded (EB), anchorage, and near-surface mounted (NSM) approaches were the main strengthening techniques addressed by researchers, both experimentally and theoretically. The goal of this work is to give a summary of the literature on the flexural and shear behavior of RC beams reinforced with FRP materials under various schemes. The efficiency of various types of FRP materials and processes has also been considered. Moreover, it illustrates a cost comparison of different strengthening schemes and the limitations of FRP strengthening. This paper also outlines knowledge gaps and possible research directions for FRP-strengthened structures, leading to a greater understanding and the establishment of design guidelines.

Nonlinear Numerical and Analytical Assessment of the Shear Strength of RC and SFRC Beams Externally Strengthened with CFRP Sheets

This study investigates numerically utilizing nonlinear finite element (ANSYS software) and analytically the shear response of the Reinforced Concrete (RC) beams. Different beams are considered in the current study, such as RC, steel fibre reinforced concrete (SFRC) without web reinforcement, and RC externally reinforced in the shear zone with carbon fibre reinforced polymer (CFRP) sheets. Nonlinear finite element model (FEM) is designed to simulate the performance of the designed beams. The results of FEM are compared to experimental measurements and standard design codes (ACI 440.2R-17, FIB 14, CNR-DT200, and ACI 318-19). According to the experimental approach and nonlinear finite element, the enhancement in the load carrying capacity of SFRC beam due to CFRP strengthening decreases with a volume fraction of steel fibres of 2%. However, the effect of CFRP strengthening on the shear behaviour of RC beams was observed in increased load carrying and ultimate deflection capacities as a result of the CFRP strengthening. The results show that CFRP has a significant contribution to shear strength. At each load increment, the created model accurately reproduced the initial and progressive crack patterns. A comparison of nonlinear finite element and analytical models was conducted using the codes ACI 440.2R-17, FIB 14, CNR-DT200, and ACI 318-19. Numerically, the FEM results showed a high agreement with ACI 440.2R-17 standard code, with correlation approach to 99%. The comparison experimental load capacity of beams to FEM and ACI 440.2R-17 shows that the FEM can be significantly used to estimate the shear strength of beams in the X-Y directions with simulating different scenarios of CFRP and SFRC characteristics. The discrepancy between the nonlinear FEA and the theoretical predictions from the ACI 440.2R-17 code is less than 1%, from the FIB14 code is less than 2%, from the CNR-DT200 code is less than 15%, and from the ACI 318-19 code is less than 30%. The ultimate load capacity evaluated based on ACI 440.2R-17 code provision shows a good agreement with the experimental data as compared to the others’ code provision. The results of the finite element analysis and analytical models were in good agreement with the experimental results. The most significant advantage of finite element analysis over experimental approaches was that it can aid in the investigation of different output results that cannot be measured experimentally, such as shear stress in the XY direction throughout the beam strengthened in shear with different CFRP properties and steel fibre reinforced concrete (SFRC).

Shear strength of recycled-aggregate concrete beams with glass-FRP stirrups

The combined use of recycled concrete aggregate (RCA) and glass fiber reinforced polymer (GFRP) reinforcement in reinforced concrete (RC) structures is deemed plausible to achieve sustainable construction. This paper aims to examine the effect of such a combination (RCA + GFRP reinforcement) on the shear behavior of RC beams. Six medium-scale RC beams (150 × 260 × 2200 mm) critical in shear were tested under three-point loading until failure. The test variables were the aggregate type (natural/recycled) and the shear reinforcement (steel/GFRP/none). The failure modes, cracking patterns, load-carrying capacities, deformational and strain characteristics were analyzed and compared among the tested specimens. It was found that using 100% RCA in the concrete mix reduced the shear strength of RC beams (by 12% on average). Minor effects were observed on the shear strength of the beam specimens (∼2%) with altering the transverse reinforcement (GFRP versus steel). Theoretical load-carrying capacities of the tested beams were obtained as per contemporary design guides and compared with the experimental results.

Shear behavior of RC beams prepared with basalt and polypropylene fibers

Basalt and polypropylene fibers are relatively cheap, durable, and corrosion-resistant materials, and they can increase the shear strength of reinforced concrete (RC) beams. Although recent studies investigated the mechanical behavior of fibrous concrete, limited research was conducted to explain the shear behavior of RC members prepared with basalt or polypropylene fibers. This research is designed to study the shear behaviour of RC beams prepared with basalt and polypropylene fibers and to find the optimum percentage for each type of fiber. Eight RC beams were tested to explain the shear behavior of RC beams prepared with basalt and polypropylene fibers. The beams and cylinders were cast with three various proportions of basalt and polypropylene fibers 0.6%, 1.3%, and 2.5% of the total cement weight. Test results showed that the best proportions for basalt and polypropylene fibers were 2.5% and 0.6% of the total cement weight, respectively. The inclusion of polypropylene or basalt fibers considerably enhanced the ductility of thebeams. Polypropylene fibers are superior to basalt fibers in enhancing the shear strength and ductility of the RC beams. The inclusion of 0.6% polypropylene fibers enhanced the shear strength, peak deflection, ductility, and initial stiffness up to 23.2%, 39.74%, 195%, and 2.56%, respectively with respect to the reference beam prepared with ordinary concrete. The inclusion of 2.5% basalt fibers increased the shear strength, peak deflection, ductility, and initial stiffness up to 20%, 64%, 121%, and 21.2%, respectively, compared to the beam prepared with the ordinary plain concrete. Finite element (FE) models were then created to capture the behavior of the beam specimens. The proposed FE models can satisfactorily predict the observed behavior.

Shear behavior of RC beams reinforced with internal trussed steel strips at shear span zone

This paper presents an experimental study on the shear performance of reinforced concrete (RC) beams provided with pre-prepared steel trusses in the shear span zone. Those steel trusses were assembled using electrical welding for steel strips of 2 mm thickness. For comparison purpose, corresponding steel trusses were assembled from equivalent rounded steel bars and used to reinforce the shear span zone of corresponding reinforced concrete beams, and then the shear behavior of beams reinforced with either trussed strips or trussed bars was compared. Accordingly, an experimental program consisted of fifteen reinforced concrete beams included one control beam have been prepared where the shear span-to-depth ratio was the same for all beams (2.3). Experimental test results showed that the beams reinforced with trussed steel strips showed better shear performance from the viewpoint of both the ultimate capacity and the developed major shear crack width compared with those of the beams reinforced with equivalent trussed bars. That is because the internal trussed strips have higher surface area than that of the equivalent rounded bars, which enabled the reinforced beam to maintain the confinement of the concrete core inside the section thus decreased the major shear crack width and increased the ultimate strength of reinforced concrete beam. Consequently, the ultimate capacity for reinforced concrete beams reinforced with internal trussed strips was higher than the corresponding capacity of beams reinforced with equivalent trussed bars by an average value of about 16%. Besides, the internal steel strips hindered the appearance of shear cracks and decreased the major shear crack width compared to the case of using equivalent rounded bars. Moreover, the experimental findings showed comparable results against the available analytical models from the viewpoints of ultimate shear capacity and maximum shear crack width.