Repairing and strengthening techniques of RC beams: a review

The purpose of this review is to present the techniques for strengthening or repairing of reinforced concrete-beams (RC). The concrete members, like RC beam are might be required to be strengthened to increase the internal strength capacity to resist additional external loads or repaired to increase the design’s structural rigidity and insulate the reinforcement from aggressive conditions. The experimental studies that related to the techniques of repairing and strengthening of RC beams using: external steel plates, fiber reinforced concrete (FRC), reinforced concrete (RC) jacketing, sprayed fiber reinforced polymer FRP, epoxy injection, mortar jackets, near-surface carbon fiber (SNSM-CFRP) strips, near-surface glass fiber (NSM-GFRP) rods, CFRP laminate and sheet; and adding an ultra high performance concrete (UHPC) layer. All the techniques that were discussed showed that there is an improvement in the general behavior of the beams that have been strengthened and repaired, as well as an increase in the maximum load and ductility.


Introduction
A better alternative to tearing down and rebuilding is strengthening and repairing damaged RC members, which can also improve structural performance.In prior research over the past decade, ultrahigh performance concrete (UHPC) and high-performance concrete (HPC) with cementitious grouts have been used as effective restoration approaches.Steel fibers enhance the performance of these materials by increasing the structural element's residual flexural strength and stiffness and decreasing the rate at which cracks propagate.[1].
When a repair is completed successfully, a structural member's performance is improved, its stiffness and strength are restored, the surface validity is extended and the entry of aggressive conditions is managed.For both economic and environmental reasons, it makes sense to prefer maintenance over construction.Repairs for RC beams subjected to settlement cracks under repeated loading conditions are a hot topic right now.In the construction of bridges and other marine constructions, this is an absolute requirement.There has been a significant shift away from the traditional view that the RC concrete is a durable.Many situations have occurred where the performance of concrete has fallen short of expectations.[2].Many concrete structures deteriorate due to factors like overloading, chemical attacks, corrosion of rebar,abrasion,foundation settlement, fatigue effect, abnormal floods, atmospheric effects, changes in use, changes in configuration, and natural disasters, despite the fact that many concrete structures are successfully built every year around the

Techniques of adding an RC or FRC layer
Denarie et al [4] investigates the flexure behavior of UHPC overlay and RC beams by replace the reinforcing steel in an RC beam and compared the ultimate strength with the control RC beam.An increase in stiffness was occurred until the ultimate capacity was reached with a ductile behavior of post peak stage, while the standard RC beams showed a minor hardening behavior.
Another method by Habel et al [5] is using a new layer of "high performance fiber reinforced cementitious" material.The tensile face of the RC beams had been covered with it using bonded strips.Four-point bending was used to test every specimen.The ultimate strength of the strengthen beams was equal to or greater than theirs, and they possessed strong energy absorption and flexural strength.
Martinola et.al [1] strengthened or repaired the RC-beams by adding(HPFRC).The proposed method takes into account the utilization of a 40 mm thick HPFRC jacket.The parameters were cast in the beams with or without rebar, as shown in figure 1.
The addition of an HPFRC jacket to each of the tested beams increased their strength relative to the reference beam.The post-peak stage shows noticeable softening.
H.K. Lee , L.R. Hausmann [6] the purpose of this study is to examine the strength and ductility properties of RC beams that have been strengthened or repaired using sprayed FRP (SFRP) in both damaged and undamaged conditions, as shown in figure 2.
Coating thickness, fiber volume percentage, fiber type(carbon and glass),fiber length, and uncracked and precracked specimens are some of the variables under examination.The findings show that SFRP is efficient in strengthening and repairing RC structures by significantly enhancing both ductility and strength.
Fodhil Kassimi, Kamal H. Khayat, and Ahmed K. El-Sayed [7] evaluate the effect of "fiberreinforced self-consolidating concrete" (FR-SCC) as a repair material by examining the impact of various contents and types of fibers on the mechanical behavior of the repaired beams.Steel, two types of polypropylene, and hybrid fibers-these are the four forms of fiber reinforcement that were used.For the FR-SCC mixtures, each fiber form was used at two different volume proportions of 1.4and 0.5%, and at 0.3 % in the (FR-SCC) mixture.The beams were made using standard vibrated concrete, with the exception of the lower 125 mm of the sample, which represents a damaged part in the tension region.The self-consolidating mixes were utilized to repair the bottom layer after curing.The test findings show that the improved repair mixtures (self-consolidating) are suitable for use in infrastructure repair and rehabilitation because they can successfully improve the flexural capability of the repaired beams.The use of(SFRP) on RC-samples [6].Prabhat Ranjan et.al [8] show how (UHPC) overlay affects the flexural performance of damaged RC beams.It is possible to induce damage by loading the control RC-beams to 90 and 80% of the ultimate load of the reference RC-beam.Twelve of the harmed beams have been retrofitted using UHPC overlay with epoxy.The highest compressive strength is reached by the curing with a hot air method, making it the preferred curing technique for ultra-high performance concrete (UHPC).It is essential to apply epoxy and adequately prepare the surface in order to provide a good bond between the overlay and the damaged beam.UHPC overlay greatly improves the internal capacity and ductility of preloaded RC-beams.
H.M.Tanarslan et al [9] focused on how reinforced concrete (RC) beams that used UHPC laminates to strengthen them behave.Secondly, a material-scale preliminary study was conducted to determine the impact of fiber-volume on the mechanical characteristics of UHPC.By using normal curing, adding up to 2% more fiber volume fractions dramatically raised peak loads; yet, adding more fiber also modestly improved performance.All specimens were enhanced with UHPFRC laminates (30 mm thick) which contain 3% steel fiber with various application types.The parameters under this investigation include: bond type( epoxy or mechanical anchorages) and placing longitudinal reinforcements into the UHPFRC laminates.The findings showed that using UHPFRC cover is a good method for improving the load carrying capability of RC beams, particularly when the anchorage is included.Also, It was discovered that adding reinforcing bars to the overlay might greatly improve the performance of the applied approach.
Mohamed A Sakr et al [10] demonstrate experimental and numerical finite element data that illustrate how well prefabricated (UHPFRC) plates work to strengthen RC beams in shear.The RC beams were strengthened using two techniques: (a) strengthening one side of the web; and (b) strengthening both sides of the web.The investigation into strengthening RC-beams utilizing nonreinforced or reinforced manufactured UHPFRC-plates was also carried out, as illustrated in figure 3. The findings demonstrate that, when compared to a reference beam that failed in shear, UHPFRC plates considerably increased the reinforced RC beams' ductility, internal capacity and mid-span strain of reinforcement.Moreover, the UHPFRC reinforcement plates avoided the bonding failure mode by using steel connectors.Al-Majidi et.al [11] examined the effect of strength the RC beams by using geopolymer-concrete which contains fiber(FRGC) and exposure to accelerate corrosion.This investigation aims to evaluate the enhancements in RC-beam strength achieved by using a newly developed FRGC that cures at room temperature under both typical and accelerated corrosion conditions.They have looked into large-scale beams that have been reinforced with steel bars and extra FRGC layers.Reinforcing materials like steel-fiber-reinforced geopolymer-concrete (SFRGC) and polyvinyl alcohol fiber reinforced geopolymer-concrete (PVAFRGC) have been used to protect the steel bars of the new layer and subsequently boost the flexural strength of existing beams.The results show that the PVAFRGCand-SFRGC strengthening layers effectively decreased the influence of the corrosion exposure on the mass loss of the reinforcing bar, and flexural performance when compared to the reference-RC beams.
Constantin E.Chalioris.et.al [12] examined The effectiveness of a shear-critical-reinforced-mortarthin, U-shaped jacket for use in repairing damaged RC-beams.The test project consists of two parts.In the first, monotonic loads were applied to five beams with different ratios of stirrups until failure.These beams had inadequate shear reinforcement and excessive flexure reinforcement.The first tested sample was designed to-fail in shear were engineered to exhibit a range of strengths, deformation capacities, and degrees of damage.Part Two focuses on, the damaged beams were covered with mild steel transverse stirrups (U-shaped) of minor dimensions and longitudinal steel bars, as illustrated in figure 4. It can be concluded from the overall performance of-the beams that the deformation capability and shear strength of-the repaired beams were greatly enhanced compared to the comparable capacities of-the initial beams.The retrofitted beams also displayed less brittleness and up to six times higher deflections at failure than the initially examined specimens, despite the fact that all of the beams failed abruptly in a shear direction.[12].Ali Hassan et al [13] Examine the shear-response of RC beams that have been repaired with SHCC-material for signs of shear damage .Four specimens were strengthened using a SHCC jacket (U-shaped) that was 20 mm thick and had four lateral reinforcement ratios (1.08, 0.86, 0.65, and 0%), with one beam serving as the control specimen.Three different.beamswere fixed using.SHCCjackets, while the shear cracks in the three remaining beams were filled with epoxy.Three alternative preloading percentages (0.95, 0.85, and 0.75% of the total capacity) were applied to the remaining six beams.The inclusion of SHCC-jacket significantly increased the tested beams' maximum capacity.The improved level of ultimate capacity of the jacketed beams grew along with the rise in the SHCC jacket's reinforcing ratio.Yet, as the preloading amount was raised, the repaired beams' shear strength gain significantly decreased.

Techniques of adding FRP layers
Ian Shaw, Bassem Andrawes [14] The results of an experimental investigation into the effectiveness of repairing and retrofitting damaged ends of pre-stressed bridge girders with FRP composite materials are described.They investigate how repairing the broken ends of the beams using FRP alone and in combination with mortar will effect the beams' recoverable shear capacity.As can be seen from the results of the tests, mortar restoration alone is not sufficient to restore the strength and stiffness of a girder with a reduced shear ability due to the loss of cover concrete in the web.Overall, the CFRP laminate repair outperformed the GFRP repair and the control beam in terms of stiffness and strength gain.Externally bonded shear FRP can be employed to meet or even exceed the shear capacity of the entire girder, even when testing with a low shear span-to-depth ratio.
Karzad et al [15] demonstrate the findings of an experimental examination into the performance of RC beams.strengthenedand repaired utilizing externally bonded (CFRP).One or two layers of CFRP were used to cover the repaired beams.The goals of this research were to assess the efficiency of EB-CFRP in strengthening weak RC.beams under shear and to describe how the strips interacted with traditional shear reinforcement.EB-CFRP strengthened beams repaired using epoxy injection not only recover more quickly, but also have a noticeably higher shear capacity, according to a study of test data.
Tidarut-Jirawattanasomkul et al [16] the application of natural.jute.fabric.reinforced.polymer(JFRP) composite sheets as strengthening layer for RC beams is examined.To model earthquake effect, the beams were exposed to nonreversed cyclic loads.By applying loads up to the yielding of the transverse steel reinforcement and up to shear failure, respectively, two pre-damaged levels were prepared.Testing variables include I the predamaged levels of RC beams before being wrapped in U-shaped JFRP, (ii) whether or not epoxy is injected into the crack, and (iii) the JFRP strengthening ratio (2 and 4 layers) , as illustrated in figure 5.The test findings showed that when shear-damaged RC beams were properly repaired and strengthened with layers of JFRP, they could fully recover to their previous shear strength.The right strengthening ratio and repair are also essential in the actual use of JFRP for RC beams in order to improve the structural performance of damaged beams.

Figure 5.
Repairing and JFRP applying [16].Feng Yu et al [17] in a provided experimental study, the effectiveness of CFRP-sheets as a bending repair technique for RC) beams is studied.On the tension face of the beams, the CFRP sheets were attached.The RC beam repaired with a CFRP sheet under a heavy predamage level is found to fail in two different ways: debonding failure and fracture failure.However, when the thickness of the CFRP sheet or the reinforcement ratio increases, the ultimate flexural bearing capacity of the restored RC beam decreases relative to the pre-damaged level.Deflection development in CFRP repaired RC beams can be slowed by decreasing the pre-damaged level, increasing the thickness of the CFRP sheet layer, or decreasing the reinforcement ratio.
Y. Kopraman, A. Özdemir, N. Kaya [18] studied the behaviors of reinforced concrete beams that had been repaired using fiber reinforced polymers after being damaged (FRP).The test's initial phase of cracking was completed, and two specimens were then repaired with 50 mm-wide, equally spaced CFRP and BFRP strips, respectively.Repaired specimens were examined as the control beam after 10 days of cure.Hence, the impact of various FRP composite types on load-bearing capacity, ductility, the beam's failure mode, and energy dissipation was examined.Figure 6 provided information on the strip scheme of the repaired specimens.FRP strips enhanced the load-carrying behavior of shear deficient side of beams significantly.The specimen repaired with CFRP easily reached bending capacity in each loading direction, while the specimen repaired with BFRP failed similarly to the control beam, showing a minor increase in shear capacity. the specimen repaired with BFRP could not develop the same type of bending cracks as were observed in the support region of the specimen repaired with CFRP. Figure 6.Repair scheme of test specimens [18].Jincheng Yang et al [19], 2021 experimental investigation of the feasibility of reinforcing beams with corroded reinforcement using U-jackets and externally bonded FRP laminates without repairing the damaged concrete cover (see figure 7).Among the six damaged beams, two were unreinforced, three had glass-FRP laminates, and three had carbon-FRP plates on the beam soffits.The six reinforced beams all got CFRP U-jackets put on them.Using a 3D scanning method, the level of local corrosion was assessed.The beams' strength and rigidity were drastically decreased because of pitting corrosion.The flexural stiffness and load-carrying capacity were both enhanced by the FRP strengthening approach (applied directly to the beams without fixing the degraded concrete cover).
Figure 7. Schematic of FRP composites applied to deteriorate concrete beams [19].Aohan Zheng et al [20] conducted an experimental examination of the shear behavior of RC beams reinforced with an engineered-cementitious-composite.(ECC) matrix comprised of fiber-reinforced polymer (FRP) grid and stirrups impacted by corrosion.The stirrup corrosion levels (15%, 10%, and 5% in design), shear span ratios (2.92, 2.31, and 1.73), type of FRP grids (basalt or carbon), and strengthening amounts were the main test variables investigated in this experiment (thickness of 5, 3, and 1 mm).This strengthening technique had some success in regaining the flexural rigidity of the beams with corroded stirrups, but it was not very effective.Yet, the ECC material's enhanced shear bearing capacity and strain-hardening properties could significantly increase the final deflection.
Wildan.A.Obaid,Ali.K.AL-asadi,Hussain.Shaia [21] studied the use of various CFRP laminate configurations for concrete beam strengthening and repair.As shown in figure 8, the preloaded beams were repaired using two distinct procedures employing CFRP sheet (U-warp and W-warp).After that, the beams were tested to see if they would fail under flexural loading system .The findings demonstrated that the repair of shear-deficient concrete beams using (CFRP) sheet is a technology that is highly successful.The capacity of previously damaged beams to be repaired not only aids in their recovery, but also significantly improves their resistance to premature shear failure.The shear strength values for the preloaded beams (45%, 60%) were remarkably similar to the results for the other specimens (70, 80, and 100%), suggesting that preloading the specimens can cause significant damage if the loading percentage goes above 60%.

Techniques of adding External Bonded plate
Sabahattin Aykac et al [22] revealed the results of a series of tests.conducted to investigate the flexural behavior of RC beams with external plating.The effects of plate thickness, securing the plate to the beam with side plates (collars) or anchor bolts, and employing perforated plates rather than solid ones have all been studied.In every specimen that had been strengthened and repaired, the bottom plate had an overall-length of 4 m and spanned the entire width of the beam.The complete drawings for the specimens Su4.5,Sbb1.5,Sbb3,Sub6,PRub6,andRub6 illustrated in figure 9.The results demonstrated that shear-peeling is a frequent mode of failure in externally plated beams, specifically when the outer plates are placed in the shear spans.The RC beams that had been reinforced with thin plates were found to be resistant to shear or flexural peeling before reaching their flexural capacities.
Yong Yang et al [23] RC-T-beams that have had fire damage and are being actively restrained by prestressed steel straps(PSS) are examined for their shear behavior.Investigated was the effect of several factors on the shearfailure mechanism and shearcapacity of the specimens, including the number of layers reinforced with straps, heating time, and the spacing of straps as shown in figure 10.According to the test results, the specimens that had undergone post-fire retrofitting exhibited greater ductility and shear capability than the unstrengthened specimens.It was concluded as a consequence that the suggested PSS modification techniques worked well to contain RC components after the fire exposure.

Techniques of adding NS-FRP
Ahmed M.Ashteyat,Rami Haddad,Yasmeen T.Obaidat [24] Investigate the use of side.near.surface.mounted.fiber.reinforced.polymer.(SNSM-CFRP) strips to strengthen or repair heatdamaged cantilever (self-compacting-concrete) beams(SCC).Using single and double (separated by 10 mm) strips, inserted in two parallel side.grooves,situated at 60 or 25mm from the top of the beams.The test findings revealed that the mechanical performance of the current SCC cantilever beam had been significantly impacted.[23].R.Capozucca,E.Magagnini, M.V.Vecchietti [25] Examine the static and dynamic responses of damaged RC beams that have been repaired with glass-fiber-reinforced-polymer (GFRP) rods using the near surface approach (NSM).Notches in the concrete cover are the standard visual representation of beam damage.After being steadily strengthened with epoxy glue and NSM GFRP rod, the beam has been put through bending tests.For a better understanding of the RC beam, refer to figure 11.The results suggest that up to the point of RC beam failure in flexural test, the NSM-GFRP rod strengthening approach may be adequate, without GFRP rod adhesion loss to the concrete cover.The effectiveness of employing NS carbon fiber reinforced polymer (CFRP) strips of various shapes to repair the structural behavior of heat-damaged reinforced concrete beams is examined in Rami.H. Haddad,Emad M.Yaghmour.[26], 2020.The SNSM CFRP strips were held in place as the beams were constructed by the grooves formed on the parallel sides of the concrete cover's straight, trapezoidal, and parabolic profiles.The results show that utilizing NS-CFRP strips with exterior and internal trapezoidal profiles produces the best performance for enhancing load capacity and stiffness, while using SNSM CFRP strips with a parabolic profile produces the best performance for ductility and toughness.
Yasmin Murad, Tareq Abu-AlHaj [27] examined the behavior of retrofitted beam using (NS-CFRP) ropes on unheated and heat-damaged RC-beams.Ten RC beams were put to the test.While the additional beams were unheated, five beams were heated to 700 C for three hours and suffered some heat damage, some strengthening patterns were used where CFRP-ropes were continually secured along the length of the beam, As shown in figure 12.The continuous strengthening design is remarkably effective at boosting the flexural strength of the RC beams, according to test results.Also, it increased the load carrying capacity of the heat-damaged beams by 47%, but it also reduced their peak.

Conclusions
The repair and strengthening of RC beams has been the topic of many studies.In this review, some researchers examined the behavior of RC beams that had been damaged for a variety of reasons after applying repair techniques, while others examined the behavior of RC beams after adding strengthening layers, and still others examined FRP internally reinforced concrete beams.From the earlier investigations, it is possible to draw several conclusions, including:  SFRC is useful in the strengthening and repair of RC structures, and it can increase the strength and ductility of RC specimens when applied to them. Externally bonded CFRP and GFRP laminate is effective to regain the strength and stiffness of damaged beams  The application of a reinforced additional layer as a strengthening material is very effective in improving the behavior of the strengthen beam. The application of epoxy resin between the UHPC overlay and the damaged.beam is very critical for proper bonding. Epoxy injection for concrete cracks can increase the strength of the concrete and improve the overall behavior of the structural member. The level of damage caused by preloading on the specimens is effective if the loading percentage increases over 60%. Adding steel reinforcement bar into the repairing and strengthening laminate could improve the efficiency of the applied technique. Strengthened the RC beams with thin steel plates, which enhanced the ultimate load and were found to be resistant to shear or flexural peeling before reaching their flexural capacities. Near surface mounted technique also increased the load carrying capacity and ductility of the strengthened and damaged beams.Aderhold J, Davydov V Yu, Fedler F, Klausing H, Mistele D, Rotter T, Semchinova O, Stemmer J and Graul J 2001 J. Cryst.Growth 222 701

Figure 2 .
Figure 2. The use of(SFRP) on RC-samples[6].Prabhat Ranjan et.al[8] show how (UHPC) overlay affects the flexural performance of damaged RC beams.It is possible to induce damage by loading the control RC-beams to 90 and 80% of the ultimate load of the reference RC-beam.Twelve of the harmed beams have been retrofitted using UHPC overlay with epoxy.The highest compressive strength is reached by the curing with a hot air method, making it the preferred curing technique for ultra-high performance concrete (UHPC).It is essential to apply epoxy and adequately prepare the surface in order to provide a good bond between the overlay and the damaged beam.UHPC overlay greatly improves the internal capacity and ductility of preloaded RC-beams.H.M.Tanarslan et al[9] focused on how reinforced concrete (RC) beams that used UHPC laminates to strengthen them behave.Secondly, a material-scale preliminary study was conducted to determine the impact of fiber-volume on the mechanical characteristics of UHPC.By using normal curing,

Figure 3 .
Figure 3. Strengthened of beam samples[10].Al-Majidi et.al[11] examined the effect of strength the RC beams by using geopolymer-concrete which contains fiber(FRGC) and exposure to accelerate corrosion.This investigation aims to evaluate the enhancements in RC-beam strength achieved by using a newly developed FRGC that cures at room temperature under both typical and accelerated corrosion conditions.They have looked into large-scale beams that have been reinforced with steel bars and extra FRGC layers.Reinforcing materials like steel-fiber-reinforced geopolymer-concrete (SFRGC) and polyvinyl alcohol fiber reinforced geopolymer-concrete (PVAFRGC) have been used to protect the steel bars of the new layer and subsequently boost the flexural strength of existing beams.The results show that the PVAFRGCand-SFRGC strengthening layers effectively decreased the influence of the corrosion exposure on the mass loss of the reinforcing bar, and flexural performance when compared to the reference-RC beams.Constantin E.Chalioris.et.al[12] examined The effectiveness of a shear-critical-reinforced-mortarthin, U-shaped jacket for use in repairing damaged RC-beams.The test project consists of two parts.In the first, monotonic loads were applied to five beams with different ratios of stirrups until failure.These beams had inadequate shear reinforcement and excessive flexure reinforcement.The first tested sample was designed to-fail in shear were engineered to exhibit a range of strengths, deformation capacities, and degrees of damage.Part Two focuses on, the damaged beams were covered with mild steel transverse stirrups (U-shaped) of minor dimensions and longitudinal steel bars, as illustrated in figure4.It can be concluded from the overall performance of-the beams that the deformation capability and shear strength of-the repaired beams were greatly enhanced compared to the comparable capacities of-the initial beams.The retrofitted beams also displayed less brittleness and up to six times higher deflections at failure than the initially examined specimens, despite the fact that all of the beams failed abruptly in a shear direction.

Figure 4 .
Figure 4.The installation of the jacketing[12].Ali Hassan et al[13] Examine the shear-response of RC beams that have been repaired with SHCC-material for signs of shear damage .Four specimens were strengthened using a SHCC jacket (U-shaped) that was 20 mm thick and had four lateral reinforcement ratios (1.08, 0.86, 0.65, and 0%), with one beam serving as the control specimen.Three different.beamswere fixed using.SHCCjackets, while the shear cracks in the three remaining beams were filled with epoxy.Three alternative preloading percentages (0.95, 0.85, and 0.75% of the total capacity) were applied to the remaining six beams.The inclusion of SHCC-jacket significantly increased the tested beams' maximum capacity.The improved level of ultimate capacity of the jacketed beams grew along with the rise in the SHCC jacket's reinforcing ratio.Yet, as the preloading amount was raised, the repaired beams' shear strength gain significantly decreased.

Figure 10 .
Figure10.Retrofitted specimen after fire test[23].R.Capozucca,E.Magagnini, M.V.Vecchietti[25] Examine the static and dynamic responses of damaged RC beams that have been repaired with glass-fiber-reinforced-polymer (GFRP) rods using the near surface approach (NSM).Notches in the concrete cover are the standard visual representation of beam damage.After being steadily strengthened with epoxy glue and NSM GFRP rod, the beam has been put through bending tests.For a better understanding of the RC beam, refer to figure11.The results suggest that up to the point of RC beam failure in flexural test, the NSM-GFRP rod strengthening approach may be adequate, without GFRP rod adhesion loss to the concrete cover.

Figure 11 .
Figure11.Dimensions of RC beam with NSM-GFRP rod[25].The effectiveness of employing NS carbon fiber reinforced polymer (CFRP) strips of various shapes to repair the structural behavior of heat-damaged reinforced concrete beams is examined in Rami.H. Haddad,Emad M.Yaghmour.[26],2020.The SNSM CFRP strips were held in place as the beams were constructed by the grooves formed on the parallel sides of the concrete cover's straight, trapezoidal, and parabolic profiles.The results show that utilizing NS-CFRP strips with exterior and internal trapezoidal profiles produces the best performance for enhancing load capacity and stiffness, while using SNSM CFRP strips with a parabolic profile produces the best performance for ductility and toughness.Yasmin Murad, Tareq Abu-AlHaj[27] examined the behavior of retrofitted beam using (NS-CFRP) ropes on unheated and heat-damaged RC-beams.Ten RC beams were put to the test.While the additional beams were unheated, five beams were heated to 700 C for three hours and suffered some heat damage, some strengthening patterns were used where CFRP-ropes were continually secured along the length of the beam, As shown in figure12.The continuous strengthening design is remarkably effective at boosting the flexural strength of the RC beams, according to test results.Also, it increased the load carrying capacity of the heat-damaged beams by 47%, but it also reduced their peak.