Internal Stirrups Research Articles

Improving shear performance of regular web openings concrete beams using steel mesh reinforced strain hardening cementitious composites: An experimental and numerical study

The majority of studies focused on shear strengthening methods for single or double transversely opened reinforced concrete (RC) beams; however, no studies examined beams with multiple openings. This study looked at the shear response of 10 RC beams with multiple openings that were strengthened with externally strain-hardening cementitious composites (SHCC) and supplied with various layers of steel mesh fabric (SMF). The square or circular shape of the openings, the use of internal stirrups, and the use of one, two, or three layers of SMFs to support the SHCC layer are investigated. Analysis was done on the beams' stiffness, ductility, ultimate load and corresponding deflection, load-displacement response and failure pattern. In the experimental program, the shear span-to-depth (a/d) ratio was 2.4 for each of the ten beams. To further examine the impact of the same key parameters on the shear response of the beams at an a/d of 1.2, a non-linear finite element model was built. The experimental results showed that dense stirrups beam, one layer SMF-beam, two layers SMF-beam, and three layers SMF-beam achieved improvements in the ultimate load of 21.3 %, 34.6 %, 38.6 %, and 47.3 %, as well as increases in the rigidity of 6.4 %, 9.4 %, 51.7 %, and 53.6 %, and gains in the ductility of 78.4 %, 28.5 %, 547 %, and 357 % when compared to comparable control beam with circular openings. The numerical results indicate that strengthening SHCC layers outperforms better for RC beams with a smaller a/d rate and that follow the arch action in the critical shear zone.

Shear performance of reinforced concrete beams strengthened in shear using NSM bars and reinforced HSC layers

AbstractThe reinforced concrete (RC) beams could be upgraded in shear using steel and fiber‐reinforced polymer (FRP) having several shapes (bars, strips, or sheets). Using near‐surface mounted (NSM) Glass FRP (GFRP) bars is still limited compared to carbon FRP (CFRP) elements as shear reinforcement. Moreover, using reinforced high‐strength concrete layers (HSCL) as NSM shear strengthening for the RC beams is still limited. Herein, three RC beams internally reinforced in shear using different shear areas (without, 100 mm stirrups apart, and 200 mm stirrups apart) were experimentally tested as reference beams (CB). Other eight beams strengthened in shear using NSM HSCL, and bars were experimentally tested. Moreover, an extended finite element (FE) simulation was implemented through a verified FE model to study the effect of other NSM aspects on shear‐strengthened beam response. The results explained that, regardless of the internal stirrups area and external NSM characteristics, the shear‐strengthened beams showed higher load efficiency than the corresponding CB. The NSM upgraded shear beam had slightly higher load efficiency than the un‐strengthened beam having the same steel area as internally shear stirrups. Moreover, increasing the internal shear stirrups decreased the total efficiency of the NSM shear strengthening and the internal stirrups regardless of the NSM characteristics. Furthermore, the NSM HSCL was more efficient than the corresponding NSM bars in increasing the load capacity and stiffness of the shear‐strengthened beams. The reported analytical model predicted well the shear capacity of the tested beams.

Effect of main and NSM reinforcing materials on the behavior of the shear strengthened RC beams with NSM reinforced HSC layers and bars

It became common practice to utilize near-surface mounted (NSM) bars to improve the shear capacity of steel-reinforced concrete (RC) beams. Consequently, carbon fiber-reinforced polymer (FRP) is usually used to improve RC beams' shear performance. Conversely, the use of Glass FRP (GFRP) for enhancing the shear behavior of the steel-RC and GFRP-RC beams is still limited. This study used NSM GFRP or steel bars to strengthen RC beams reinforced in tension with steel or GFRP bars. In addition, a new NSM technique was conducted using high-strength concrete (HSC) layers reinforced with GFRP or steel bars bonded within grooves to enhance beams' shear capacity. The results of seventeen beams used in the tests showed that NSM HSC layers improved the shear performance of RC beams more than NSM bars. Also, the beams reinforced in tension with steel bars had higher shear efficiency and were stiffer than those reinforced with GFRP bars. Conversely, the shear efficiency of steel RC beams strengthened in shear with internal stirrups or NSM reinforcement (or both) increased by 142.8–211.7% compared to GFRP RC beams without internal and NSM shear reinforcement. Conversely, the shear capacity of the steel-RC beams strengthened in shear with internal stirrups or NSM reinforcement (or both) increased by 153.5–279.9% compared to the corresponding beam without GFRP RC beam without internal and NSM shear reinforcement. The numerical analysis using the ABAQUS program showed great effects of the tension reinforcement and the NSM materials on the strain of longitudinal bars, stirrups and NSM reinforcement.

Shear strength of square concrete-filled steel tubular columns reinforced with internal steel stirrups

A concrete filled steel tubular (CFST) column internally reinforced with steel stirrups has significantly enhanced fire resistance over a conventional CFST column without stirrups. Resistance to shear may be a vital load case to be considered when designing CFST columns. However, there is comparatively little research into the shearing behaviors of CFST columns and the existing design equations do not adequately describe the contributions of different components to the total shear resistance. In this study, thirty-five square CFST columns, with and without stirrups were fabricated and tested to failure under combined shear load and axial compression. The portions of observed shear resistance contributed by the steel tube, concrete infill and stirrups were isolated. The concrete contained demolished concrete lumps (DCLs). The tube’s thickness, the ratio of shear span to depth, the axial load ratio, the replacement ratio of DCLs, the center-to-center spacing between stirrups, and the gap between steel tube and stirrups were varied in the experiments. The test results showed that: (1) the shear capacity was much greater at a smaller shear span-to-depth ratio, but the ratio had little effect on the contribution of the steel tube to shear resistance when ranging from 0.15 to 0.50; (2) the shear capacity gradually increased as the axial loading increased, but the shear contribution of the steel tube decreased; and (3) the internal stirrups contributed little to the shear resistance, and there was little difference in shear capacity as the gap between the stirrups and tube increased from 15 mm to 35 mm. A method to adequately capture the respective contribution of different components in the column was proposed. The new method generally gave more accurate predictions than the methods currently in use, and its predictions were generally conservative.

Cisalhamento em vigas de concreto armado com armadura transversal interna contínua

Abstract: Reinforced concrete elements with a high longitudinal and transverse reinforcement ratio may present conflicts on both of them, resulting in reduced labor productivity and a poor job when assembling the transversal reinforcement, reducing its effectiveness. Thus, this research presents a type of internal transverse reinforcement as an alternative to mitigate this conflict between the transverse and longitudinal bars. A total of 5 reinforced concrete wide beams were made, one of them as a reference with closed stirrups, and the other ones with internal stirrups, varying the inclination of the internal transverse reinforcement in 60° and 90°, and the number of vertical legs of the internal transverse reinforcement used. Comparing the results of the beams with internal stirrups with the reference beam, it was observed that the internal stirrups provided increases of up to 14% in shear strength when compared with the closed stirrup.

Effectiveness of SHCC strips reinforced with glass fiber textile mesh layers for shear strengthening of RC beams: Experimental and numerical assessments

In the present study, the potential of the use of strain-hardening cementitious composite strips internally reinforced with glass fiber textile mesh layers (GFTM-SHCC) as a strengthening system for shear-critical reinforced concrete (RC) beams is examined. For this purpose, thirteen simply supported beams incorporating two bare control specimens were tested under a three-point loading scheme. The GFTM-SHCC strips were applied inside 20 mm grooves within the beams' substrate so as to prevent the likelihood of premature debonding failure and to significantly enhance the utilization of the adopted strengthening system. The considered key parameters were the layers' number of the GFTM within the SHCC strip (2, 4, or 6), the spacing between GFTM-SHCC strips (90, 150, or 225 mm), the GFTM-SHCC orientation angle (45°, 60°, or 90°), and the strengthening configurations (side-bonded, U-wrapped, or fully-wrapped). Moreover, the location of the strengthening strips relative to the internal stirrups, if they exist, (aligned or un-aligned), was of interest.The effectiveness of GFTM-SHCC was evaluated in terms of failure patterns, ultimate shear capacity, and the gain in ductility. Experimental results revealed the effective implementation of the GFTM-SHCC strengthening strips in improving the ultimate shear capacity and the deformation characteristics of the tested specimens; however, their behavior relied on the test parameters. The shear carrying capacity and the ductility of the strengthened RC beams using GFTM-SHCC strips were in the range of 47–142% and 21–172%, respectively, higher than their counterpart control specimens. Furthermore, among all strengthening configurations, fully-wrapped strengthened RC beams demonstrated the highest gains in shear capacity, while inclined GFTM-SHCC strips with orientation angles of 45° and 60° outperformed vertical strips significantly. An analytical model to predict the ultimate shear capacity of the strengthened RC beams was derived and verified against the experimental results. To further assess the potential of the GFTM-SHCC strips for the shear strengthening of RC beams, a three-dimensional (3D) non-linear finite element model (FEM) was created using ABAQUS software and verified against the experimental records. After affirmation of the satisfactory predictive performance of the numerical model, a parametric study was performed to compare the shear responses of RC beams strengthened with intermittent GFTM-SHCC strips with continuous ones (strengthened along the whole shear span zone).

Effect of Internal Stirrups on the Eccentric Compression Behavior of FRP-Confined RC Columns Based on Finite-Element Analysis

Fiber-reinforced polymers (FRPs) have been widely used in the retrofitting and rehabilitation of reinforced concrete (RC) columns because they can provide substantial lateral confinement to concrete. Conventionally, the presence of internal stirrups is neglected in the retrofitting design due to a lack of understanding on the effect of internal hoops when both external FRP and internal steel confinement exist, particularly under eccentric loading. In this study, a finite-element (FE) method is developed to investigate the eccentric compression behavior of FRP-confined RC columns. A reliable concrete plastic-damage model that accurately considers the confining stiffness ratio between the FRP and steel is proposed for the first time, which facilitates the study of a difficult problem: the behavior of RC columns with the dual confinement system under eccentric loading. The accuracy of the model is verified by test results. An extensive parametric study of various affecting factors is carried out to investigate the confinement mechanisms of the concrete columns in terms of the axial stress and confining pressure distributions, lateral principal stress ratio, local stress–strain response, and interaction between the FRP/steel hoops and concrete. It is found that the nonuniform confining pressures under eccentric compression are significantly affected by the internal stirrups. With the existence of discrete transverse steel reinforcement, the axial resistance of the concrete core is increased, thereby improving the ultimate load capacity of the columns. An ultimate axial load model for RC columns that considered combined FRP–steel confinement is subsequently proposed. More accurate results are obtained using the proposed model compared with those calculated from existing design codes.

Shear strengthening of reinforced concrete deep beams with highly ductile fiber-reinforced concrete jacket

This paper presents an experimental work on the shear behavior of reinforced concrete (RC) deep beams strengthened with highly ductile fiber-reinforced concrete (HDC) jackets. The test variables included the shear-span-to-effective-depth ratio, presence or absence of internal stirrups, the internal shear reinforcement ratio, the thickness of the U-shaped jacket (15 mm and 25 mm), the types of the matrix (HDC and mortar), and the presence or absence of stirrups in jackets. A total of seventeen beams were loaded under three-point bending test in two batches. The failure modes, load-deflection curves, and load-strain curves were described and analyzed. The test results revealed that the shear strengthening effectiveness of the HDC jacket for RC beams was obvious. The RC beams strengthened with HDC had a better cracking pattern and failure mode compared with the reference specimens and the beam strengthened by mortar. The shear capacity of the beams strengthened with HDC was improved by 13.6%–145.5%. The shear capacity of the HDC jacket-retrofitted specimen increased significantly by configuring stirrups in the jacket or increasing the jacket thickness. The shear strengthening effectiveness of HDC jacket revealed an upward trend with an increase in shear-span-to-effective-depth ratio. The strength of stirrups in HDC jacket was effectively utilized, mainly because HDC jacket showed a good synergistic performance with the internal RC beam. Furthermore, in order to calculate the shear capacity of the beams strengthened with HDC, the direct strut-and-tie model (DSTM) was adopted and modified. The results of the calculation correlated well with existing experimental results.

Axial compressive behavior of square steel tubular columns filled with steel stirrups reinforced recycled lump concrete

Without increasing the total steel usage, a square concrete filled steel tubular (CFST) column with internal steel stirrups and relatively thinner steel tube exhibits a superior fire resistance over a traditional CFST column without stirrups, but there are few studies on the former’s axial compressive behavior at ambient temperature. Fourteen square concrete filled steel tubular columns with internal steel stirrups and six control columns without stirrups were tested under pure axial loading. The concrete filling was incorporated with lumps of recycled concrete, which can be a feasible solution for recycling and reusing waste concrete. The test results showed that: (1) with the same total steel usage, the internal stirrups slightly decrease a column’s ultimate capacity, but they significantly improve the ductility and post-peak deformability; (2) including lumps of recycled concrete in the fill has little effect on the axial compressive behavior up to a replacement ratio of 30%. The experimental data are compared with the predictions of existing design standards and empirical methods, and one of the methods is extended to predict the ultimate capacity of columns with internal stirrups containing lumps of recycled concrete.

Influence of Compressive Strength of Concrete on Shear Strengthening of Reinforced Concrete Beams with Near Surface Mounted Carbon Fiber-Reinforced Polymer

This paper investigates the effect of using near-surface mounted carbon fiber-reinforced polymer (NSM-CFRP) on the shear strengthening of rectangle beams with low strength concrete (f′c = 17 MPa), medium strength concrete (f′c = 32 MPa), and high strength concrete (f′c = 47 MPa). The experimental program was performed by installing NSM-CFRP strips vertically in three different configurations: aligned with the internal stirrups, one vertical NSM-CFRP strip between every two internal stirrups, and two vertical NSM-CFRP strips between every two internal stirrups. All tested beams were simply supported beams and tested under a three-point loading test. The experimental results were compared with the theoretical capacities that were calculated according to the ACI 440.2R-17 and finite element analysis (FEA) that was conducted using ABAQUS software to simulate the behavior of all beams. The experimental results indicated that using NSM-CFRP limited the failure mode of all beams to pure shear failure with no debonding or rapture of the carbon strips. Moreover, the use of NSM-CFRP proved its efficiency by increasing the shear capacity of all beams by a range of 4% to 66%, in which the best enhancement was recorded for the case of using two unaligned NSM-CFRP strips. In general, the experimental shear capacities increased with the increase in the compressive strength of all beams. On the other hand, the ACI 440.2R-17 was conservative in predicting the theoretical shear capacities, and the FEA results agreed well with the experimental results.

Experimental study on shear response of GFRP reinforced concrete beams strengthened with externally bonded CFRP sheets

An experimental investigation into the shear behavior of Glass Fiber Reinforced Polymer (GFRP) reinforced concrete beams is presented. The study also looks at the effectiveness of shear strengthening of such beams using externally-bonded Carbon Fiber Reinforced Polymer (EB-CFRP) sheets and investigates the possibility of interaction between internal and externally bonded shear reinforcement. A total of 18 beams, 2.4 m long with a rectangular cross-section of 300x200, reinforced with GFRP bars and stirrups were tested. Three types of concrete were used in this study; ordinary Portland cement (OPC) concrete, Fiber Reinforced concrete (FRC), and Geopolymer concrete (GPC). Six beams, two for each concrete type, severed as control while the other twelve were strengthened using “U” shape EB-CFRP sheets. The CFRP sheets were placed in two different arrangements, above and in-between internal stirrups locations. The results indicate that GFRP is a viable reinforcement for GPC, OPCC, and FRC, whereas EB-CFRP proves to be a feasible strengthening technique for such composite systems. The gain in shear strength for EB-CFRP strips beams on the location of internal stirrups is 5–10% lower as compared to the other arrangement. The difference in the strength gain may indicate a possible interaction between the internal and external shear reinforcement.

Size Effect in FRP Shear-Strengthened RC Beams: Design Models versus Experimental Data

Numerous studies on the size effect have been devoted to reinforced concrete (RC) beams. They have shown that increasing the beam size leads to a decrease in ultimate shear strength (stress) at failure. This is reflected in the design model of most current international codes and guidelines, where the size effect is taken into consideration by reducing concrete contribution to the shear resistance (force). In contrast, the size effect of RC beams strengthened with externally bonded (EB) fibre-reinforced polymer (FRP) is not fully documented, and very few experimental studies have been devoted to the phenomenon. The objective of this study was to evaluate the accuracy of the current code and guideline models in terms of the size effect on the EB-FRP contribution to shear resistance. To this end, a database of experimental findings on the size effect in EB-FRP-strengthened beams was built based on the reported literature, as well as our own experimental tests. The data were analysed and compared with the predictions of six current codes and design guidelines to assess their accuracy. Experimental results clearly revealed the presence of a size effect related to EB-FRP as well as the existence of interaction between internal stirrups and EB-CFRP. Based on analysis of the collected experimental test results, the study clearly revealed that the predictions of current codes and guidelines overestimate the contribution of EB-FRP systems to shear resistance. The size effect tends to exacerbate this overestimation as the effective depth (d) of the beams increases. Therefore, until the size effect for RC beams strengthened in shear with EB-FRP is captured by the prediction models, current codes and design guidelines are to be used with caution.

Simulating the passive confinement of rectangular concrete prisms allowing for size effect

Tests have shown that providing passive confinement to concrete, either through the use of internal stirrups, external fibre-reinforced polymer (FRP) wraps, FRP tubes or steel tubes, can increase the concrete strength and, in particular, the concrete ductility, thereby allowing greater absorption of energy and consequently ductile failure. The problem of including the benefits of passive confinement in design is in generalising the effect of passive confinement because it varies with the member size, the configuration of the confining reinforcement and material properties. In this paper, all aspects of the complex fundamental mechanics of passive concrete confinement are explained both qualitatively and quantitatively through the use of shear–friction and bond–slip mechanics. The mechanics model was found to have a good correlation with test results. An analysis-oriented procedure is described for quantifying the passive stress–strain of concrete for rectangular sections and it is envisaged that this can be used to develop simplified rules for design, in particular for new types of members and those with new materials.

Torsional Strengthening of Low-Strength RC Beams with Post-Tensioned Metal Straps: An Experimental Investigation

This article investigates the behaviour of low-strength reinforced concrete beams under pure torsion with and without strengthening. Four beams were cast and tested in torsion: i) a control beam without vertical reinforcement, ii) two beams with internal stirrups designed for shear and torsion demands using different stirrup spacing (50 and 100 mm), and iii) a beam having steel stirrups with a spacing of 100 mm strengthened using high ductile post-tensioned metal straps (PTMS). The main objective of the PTMS strengthening solution was to investigate the enhancement of torsional strength confined along the beam. The failure modes, torsional capacities, rotation, and strengthening performance in torsion are discussed in in this study. The experimental results indicate that the PTMS improved the cracking torque capacity by up to 15 % compared to the control beam. Moreover, the PTMS also increased the ultimate torque by up to 19 % compared to the unstrengthened beam. Current code equations to predict the torsional capacity of RC beams are also compared with the experimental results. It is found that the predictions obtained by current ACI equation gives a good agreement and yield in general conservative values compared to the experimental ones.

Performance and failure analysis of carbon fiber-reinforced polymer (CFRP) strengthened reinforced concrete (RC) beams

At present, the strengthening and retrofitting of reinforced concrete (RC) beams using carbon fiber-reinforced polymer (CFRP) are receiving extensive attention. The use of strengthening technique for RC beams vary according to purpose. In general, this technique aims to increase load-carrying capacity, either through flexural or shear strengthening. The present study aims to investigate the load–deflection response of CFRP-strengthened RC beams through experimentation with five various strengthening configurations and two different types of surface treatment. The RC beams that were tested in this work were small scale. Results indicate that compared with control beams, CFRP-strengthened beams notably reinforced ultimate load and deflection, as well as ductility, because of the stiffness and grip provided by CFRP. Among the five configurations, the continuous U-wrapping and strip wrapping systems were proven effective for strengthening. A close interaction between internal stirrups and external CFRP strips, which will negatively affect the overall strength of the beams if the reinforcements were placed simultaneously along a similar section of the beam. The failure pattern of the strengthened beams considerably depends on strengthening configuration and internal steel reinforcement, which control the ultimate effectiveness of strengthening. In addition, the ultimate capacity of the beams was predicted in accordance with the ACI 440.2R-17 guidelines and was finally compared with the experimental ultimate loads of the CFRP-strengthened beams. Experimental results show that the predicted values were extremely conservative.

Experimental study on shear strengthening of shear critical RC beams using iron-based shape memory alloy strips

Shape memory alloys (SMAs) have been introduced into structural engineering in recent years. This paper presents research results about developing a new methodology to actively strengthen reinforced concrete (RC) beams by low-cost iron-based SMA strips (Fe-SMA). These strips can transversally prestress, or confine, the cross-section of beams thanks to the shape memory effect of Fe-SMA, without having to apply prestressing force. Activation of strips is carried out by heating them up to 160 °C and then cooling them. An experimental campaign was carried out at two levels: characterization of Fe-SMA strips, and the practical application of the strengthening technique on small-scale beams without internal stirrups. The retrofitted beams with activated strips failed by bending, and the appearance of shear cracks was clearly delayed. Meanwhile, the reference beams failed due to shear.

CFRP grid embedded in mortar for strengthening of shear-critical RC beams

A carbon fibre-reinforced polymer (CFRP) grid embedded in mortar (CGM) is an innovative strengthening system that has similar benefits to fibre-reinforced polymer (FRP) strengthening systems for concrete structures, but overcomes such drawbacks as poor compatibility with concrete substrate and lack of vapour permeability. A study was conducted to investigate the effectiveness of the CGM composite system to strengthen shear-critical reinforced-concrete beams. The results show that a CFRP grid embedded in mortar is effective in enhancing the load-carrying capacity of shear-critical reinforced-concrete beams. However, the effectiveness of CGM strengthening reduces with the presence of stirrups. In addition, the CGM strengthening slightly reduces the shear strength contribution from internal stirrups. The experimental shear strength contributions were also compared with predicted values based on North American FRP design guidelines with some modifications.

BEHAVIOR OF CORRODED RC BEAMS WITHOUT STIRRUPS REPAIRED WITH CFRP SHEETS

In reinforced concrete structures located in hot and humid areas, steel reinforcement is generally vulnerable to deterioration due to corrosion. Corrosion of reinforcement in many cases is considered the main cause of concrete structures deterioration, which in turn requires large budgets for repair and maintenance. This paper presents the experimental results of damaged/repaired reinforced concrete beams. The experimental program consisted of testing reinforced concrete rectangular beam specimen’s with/without shear reinforcement and exposed to accelerated corrosion of the longitudinal steel reinforcement on the tension side. Bonding external U-shaped CFRP sheets to restore the strength loss due to corrosion repaired corroded beams without shear reinforcement. The test results showed that corroded beams without stirrups failed in a brittle manner with drop in maximum deflection at failure of approximately 60% compared to the uncorroded beam. Corroded beams with stirrups lost some strength, but failed in ductile manner. Using externally bonded U-shaped CFRP sheets restored the ductility of corroded beams without stirrups and prevented bond failure at the steel concrete interface due to the absence of internal stirrups.

Numerical Simulation and Experimental Testing of Concrete Beams Strengthened in Shear with Fabric-Reinforced Cementitious Matrix

AbstractThis paper presents results of finite element (FE) modeling and experimental testing of reinforced concrete beams strengthened in shear with fabric-reinforced cementitious matrix (FRCM). The studied parameters included the number of FRCM layers (one and two layers), matrix type (mortar and epoxy), and amount of internal stirrups (no stirrups and stirrups with spacings of 0.6d and 0.3d, where d is the depth of the tensile steel). Test results showed that the shear-strength gain after strengthening was in the range of 51–145%. The shear-strength gain decreased with an increase in the amount of internal stirrups. Doubling the number of FRCM layers resulted in a nonproportional increase in the shear strength. The use of epoxy adhesive rather than a cementitious mortar as a matrix insignificantly increased the shear-strength gain. The effect of increasing the amount of FRCM or varying the matrix type on the shear strength was less pronounced for the specimens with internal stirrups. The FE models devel...

Structural behavior of corroded RC beams with/without stirrups repaired with CFRP sheets

Strengthening/repair of existing reinforced concrete structures has become one of the important issues in the field of civil engineering. In reinforced concrete structures located in hot and humid areas, steel reinforcement is generally vulnerable to deterioration due to corrosion. Corrosion of reinforcement in many cases is considered the main cause of concrete structures deterioration which in turn requires large budgets for repair and maintenance. This paper presents the experimental results of damaged/repaired reinforced concrete beams. The experimental program consisted of testing 12 reinforced concrete rectangular beam specimens with/without shear reinforcement and exposed to accelerated corrosion. The corrosion level was varied between 5 and 7.5 % which represents mass loss of the longitudinal steel reinforcement on the tension side. Corroded beams without shear reinforcement were repaired by bonding longitudinal carbon fiber reinforced polymer (CFRP) sheets to the tension side in addition to external U-shaped CFRP sheets to restore the strength loss due to corrosion. Corroded beams with stirrups were repaired by bonding longitudinal CFRP sheets to the tension side only. The test results showed that using externally bonded U-shaped CFRP sheets restored the ductility of corroded beams without stirrups and prevented bond failure at the steel concrete interface due to the absence of internal stirrups. In addition, combining U-shaped and longitudinal CFRP sheets enhanced the ultimate load by 37 % and the stiffness by 25 % in corroded beams without stirrups. For corroded beams with stirrups ductile failure was observed. Corroded beams with stirrups strengthened with CFRP sustained higher failure loads; however, the stiffness was unchanged.