Impact of Loading Protocol on the Repair Efficiency of Heat-damaged Concrete Beams with SNSM CFRP Ropes

Impact of Loading Protocol on the Repair Efficiency of Heat-damaged Concrete Beams with SNSM CFRP Ropes | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article Impact of Loading Protocol on the Repair Efficiency of Heat-damaged Concrete Beams with SNSM CFRP Ropes Rami Haythem Haddad, Rawan S. Obeidat This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-4434850/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 09 Jan, 2025 Read the published version in Materials and Structures → Version 1 posted 5 You are reading this latest preprint version Abstract The influence of static-load distribution and symmetry on the flexural performance of concrete beams, strengthened/repaired using side near-surface-mounted (SNSM) CFRP ropes with parabolic and straight profiles is investigated. For this, eighteen reinforced concrete beams (150 × 250 × 1600 mm) were fabricated using a ready-mix concrete of 35 MPa strength grade before cured for 28 days in wet burlap for 28 days. Nine beams were exposed to an elevated temperature at 450 o C for three hours, while the remaining ones were left in laboratory air, as controls. Six specimens from each group were retrofitted using SNSM of straight and parabolic profiles then tested with references ones under four- and six-point symmetrical and six-point asymmetrical loadings with load response versus deflection and strain in SNSM ropes acquired. Furthermore, cracking initiation and propagation leading to failure was monitored and reported. Generally, the study revealed that the mechanical performance of the concrete beams was influenced by the loading regime as well as by the rope profile (straight, parabolic) as well as heat-damage. The flexural performance factor (PF) varied from 5.4 to 7.9 for strengthened compared to 10.9 to 16.3 for repaired and heat-damaged specimens. Furthermore, all strengthened/repaired beams failed by concrete-cover separation following the sudden rupture of the SNSM CFRP ropes except for that repaired with a straight profile of SNSM CFRP rope and subjected to asymmetrical loading. Concrete Beams Flexure strengthening CFPR ropes SNSM Loading Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 10 Figure 11 1. Introduction Concrete is one of the most common construction materials due to its superior features of durability and compressive strength, as well as its low coefficient of thermal expansion. Over time, reinforced concrete (RC) structures could be subjected to devastating environmental impacts, such as fire, sulfate attack, freezing and thawing, or corrosion of steel reinforcement. Under fire, concrete becomes physically damaged with limited chemical changes at a temperature of about 450°C [ 1 ]. The resulting damage is manifested by extensive surface cracking and possible spalling of concrete elements with significant losses in their mechanical performance [ 2 – 4 ]. Extended exposure of concrete elements to fire attack may destroy their concrete cover and undermine the mechanical performance of embedded steel reinforcement and its bond to concrete [ 5 – 9 ]. It is proved that the temperature level of a fire and its duration are the two most significant determinants of heat damage in concrete [ 10 ]. The current database revealed that most fire-damaged structural elements are repaired to restore their mechanical performance and raise the structural safety of relevant facilities [ 11 ]. Since more than two decades ago, most concrete structural elements have been repaired using externally bonded fiber-reinforced polymer (FRP) composites due to their exceptional qualities, including their high strength-to-mass ratio and anticorrosive qualities [ 12 , 13 ]. However, this repair methodology's practical and economic efficiency was undermined by the premature separation of the FRP composites [ 14 ]. As an alternative, near-surface-mounted (NSM) FRP composites emerged as a new repair method that contributes to resolving the bond problem associated with externally bonded FRP composites. NSM CFRP composites in the form of rods, strips, or ropes are inserted in epoxy-filled grooves created in the concrete cover of a flexural element [ 11 , 15 – 19 ]. The NSM FRP technique typically outperforms the externally bonded FRP method due to its lesser sensitivity to detachment and damage from the sun, fire, and direct loads. Furthermore, its implementation requires shorter time and effort while maintaining the aesthetic view [ 15 ]. Several experimental investigations have been conducted to assess the flexural performance of beams strengthened with NSM FRP composites [ 11 , 17 , 18 ]. According to Sharaky & Salam [ 17 ], the stiffness and bearing capacity of fully bonded NSM FRP-enhanced beams were higher than those of partially bonded ones. They claimed that concrete-cover separation starts at the cut-off points to cause the failure of strengthened beams and that end anchorage had a negligible impact on the composite behavior of the beams inside the constant-moment zone. Later, Haddad & Almomani [ 11 , 18 ] examined how the configuration and staggering of the NSM CFRP strips affected the effectiveness of repairs. Results demonstrated that NSM CFRP strips contributed to increasing the load capacity, yet reducing the ductility of the concrete beams, depending on the embedment length. To reduce or eliminate the tendency towards premature concrete-cover separation, some research attempts were made to insert NSM CFRP composites within the side covers (SNSM) of the beams [ 20 – 23 ]. According to Hosen et al. [ 20 ], the SNSM approach significantly improved the flexural performance of RC beams, increasing the ultimate and yield load-carrying capacities of the beams by a factor of 2.38 and 2, respectively, with an improvement in the cracking load by about (3.17 times). Abdallah et al. [ 21 ] compared the strengthening efficiency of concrete beams with SNSM CFRP rods to that with bottom NSM techniques to conclude that the SNSM approach had caused higher reductions in the ductility and deflection at the ultimate load. Haddad and Harb [ 24 ] examined the effectiveness of mounting SNSM CFRP ropes at straight, trapezoidal, step-wise, and parabolic profiles on control and heat-damaged beams. The findings revealed that trapezoidal and parabolic profiles were effective in delaying concrete-cover separation and hence promoting the benefit of strengthening or repair. Heat-damaged (at 500 o C) and repaired beams demonstrated a shear-type failure instead of a typical flexural failure. Most of the database for FRP-strengthened/repaired beams was acquired under the effect of symmetric loading at three or four contact points. This limited the benefit of relevant findings, because the distribution of shear and bending stresses, along the span of the NSM CFRP retrofitted beams, determines the tendency toward concrete-cover separation. A few researchers have looked at the impact of load uniformity on the behavior of RC beams, strengthened in flexure with externally bonded (EB) FRP plates/sheets [ 25 – 28 ]. Pan et al. [ 25 ] found that the load uniformities influence the detachment tendency in concrete beams with EB FRP composites, hence affecting their load-carrying capacity. In contrast, Fu et al. [2018] stipulated that load uniformity led to greater load-carrying capacity and deformation capabilities for beams of different shear span ratios and strengthened with EB composites. Mazzotti and Savoia [ 27 ] claimed that using FRP sheets is more effective than using pultruded plates for strengthening under a uniformly distributed load in the form of eight contact points. Thomsen et al. [ 28 ] showed that RC beams, strengthened with EB FRP plates, often perform more effectively under distributed loads compared to the case with four-point bending loading situations. The first-ever experimental and numerical study into how load uniformity affects the behavior of NSM FRP-strengthened concrete beams was carried out by Zhang et al. [ 29 ]. They concluded that the load uniformity was influential when the failure of the strengthened beams was governed by concrete-cover separation. A few researchers tackled the impact of load symmetry on the performance of FRP-strengthened RC beams [ 30 – 34 ]. Razaqpur et al. [ 31 ] examined the effect of the asymmetrical loading on FRP shear-strengthened beams with different shear span-to-depth ratios. They stipulated that moment and shear interaction can be considered for shear span-to-depth ratios of less than 2.5, yet disregarded for greater ratios where shear behavior becomes dominant. The impact of asymmetrical loading in continuous concrete beams with glass FRP was studied by Rahman et al. [ 32 ]. Three loading scenarios were considered: loading both spans equally, loading one span at a load ratio of 1.5 of the other’s, and loading one span only. Compared to beams tested under symmetrical loading, those tested under asymmetrical loading experienced reduced crack widths, strains, and deflections in the greater load span. Additionally, moment redistribution was negatively impacted by the asymmetrical loading circumstances. Hawileh et al. [ 33 ] focused on examining the shear capacity of CFRP-reinforced concrete beams using three-dimensional finite element (FE) models. The researchers concluded that the FE models that they developed provided reliable insights into the shear behavior of CFRP-reinforced concrete beams under asymmetrical loading conditions. Finally, Tiejiong et al. [ 34 ] explored potential alternatives to address the issue of corrosion by replacing steel bars with FRP bars in externally pre-stressed concrete continuous beams exposed to different loading regimes. Compared to symmetric-loading conditions, asymmetric-loading conditions caused higher mid-span deflection, but lower tendon stress. 2. Problem Statement In any structure, concrete beams are the most susceptible elements to fire attack, especially central ones; receiving significant damage when the fire period extends beyond 2 hours. Repair of these elements with EB-CFRP composites provided limited advantages in terms of strength and stiffness recovery; owing to the premature detachment of the composites. In contrast, NSM CFRP composites proved to be more effective, especially when implemented on the side at the straight or variable profile [ 20 – 24 , 35 – 37 ]. Recent studies indicated that SNSM CFRP ropes used in retrofitting concrete beams tended to fail by the composite’s rupture; especially when implemented on the side at a variable profile [ 24 , 37 ]. The above behaviors were noticed for one case of loading which involves subjecting the beams to two equal loads at two contact points around the center of the beams. The impact of distributed and asymmetric loadings on the performance of concrete beams with EB-FRP composites was investigated previously. However, no approved works have tackled the impact of the latter two loading regimes upon the behavior of concrete beams with SNSM CFRP ropes. 3. Objectives and Scope The present work sheds light on the impact of loading distribution and asymmetry upon the efficiency of retrofitting heat-damaged beams with straight and parabolic profiles of SNSM CFRP ropes. For comparison purposes, identical intact beams were strengthened using similar CFRP rope configurations before tested under the same loading conditions. The implementation of SNSM CFRP ropes at a parabolic profile aimed at delaying or preventing concrete cover separation throughout the high shear zone. Eighteen reinforced concrete beams with dimensions of (150 × 250 × 1600 mm) in (width, depth, and length), respectively, were cast using a ready-mix concrete (RMC) having a strength grade of 35 MPa before being cured for 28 days in wet burlap until becoming matured. The eighteen beams were divided into three groups of six each. In each group, two beams were designated for determining the flexural performance of the intact beam and that heat-damaged at 450 o C, while two intact and two heat-damaged beams were strengthened/repaired with straight and parabolic profiles of SNSM CFRP ropes. The specimens in groups I, II, and III were tested under the effect of four-point symmetric, six-point symmetric, and six-point asymmetric loadings, respectively. A summary of test specimens and their designations is provided in Table 1. The relatively large specimen size used in the present work helped minimize possible experimental error related to materials variability. Hence, we believe that the differences in the mechanical properties among the present beams reflected mainly the impact of heating, repair regime and loading protocol [24-34]. 4. Experimental Work 4.1 Aggregate Properties and Concrete Mixture A ready-mix concrete (RMC) with a strength grade of 35 MPa was used in casting all specimens of this study. The mixture was prepared using Type-II Portland Cement and tap water, with coarse limestone aggregate (at a maximum aggregate size of 19 mm), medium-size coarse aggregates, crushed sand, and silica sand at proportions of 20%, 24%, 20%, and 36%, respectively. A superplasticizer having a commercial designation of Flocrete SO720 was added to the mixing process at a dosage of 9 liter/m 3 to improve workability during the casting process. The physical aggregate properties of all aggregate components were determined by the concrete’s manufacturer according to the ASTM testing procedure [ 38 , 39 ]. The bulk specific gravity (dry) for coarse, medium and fine limestone aggregate are 2.59, 2.58, 2.58, respectively, whereas that for silica sand is 2.60. The relevant absorptions are 2, 1.9, 2.6, and 0.9%, respectively. The fineness of the blend of fine limestone and silica sand is 2.8. Tests on trial mixes showed that the mixture attained a slump of 170 mm during casting time and an average compressive strength of 35 MPa and 42 MPa at ages of 7 days and 28 days, respectively. The proportions of gross water, cement, coarse aggregates, medium aggregates, crushed sand, and silica sand were used at 167, 325, 374, 449, 370, and 675kg/m 3 , respectively. The concrete was batched at the ready-mix plant by weight with 2 m 3 delivered for casting. In this study, uniaxial-compression tests were carried out on standard concrete cylinders (100 × 200 mm) to determine the compressive strength before and after exposure to 450 o C [ 40 ]. Cylindrical specimens (150 × 300 mm) were also cast to determine the compressive stress-strain diagram for the present concrete before and after being damaged by heating [ 41 ]. The results showed that there was a noticeable degradation in the compressive strength of concrete after being heated at 450°C for 3 hours at a residual of 29%, the compressive strength of the intact cylinders averaged 42 MPa, as compared to 30 MPa for those heat-damaged. The stress-stain response acquired indicated an increase in strain at ultimate stress from about 0.0025 for intact concrete to about 0.0035 for heat-damaged concrete. The stress-strain relation of the concrete before and after heating is depicted in Fig. 1. 4.2 Reinforcement Detailing and Properties The steel reinforcement was determined according to ACI 318 to ensure that flexural failure occurs before shear failure in all RC beams [ 42 ]. All beams were strengthened with the same type and quantity of deformed steel bars, employing 2Φ12 bars for tension reinforcement and other 2Φ12 bars for hungers. Such reinforcement ensures that flexural failure occurs before shear failure. The high shear zones of the beams were strengthened with Φ10 stirrups at a center-to-center spacing of 100 mm to prevent shear failure, regardless of the loading scheme. The first two groups, designated for symmetrical-loading protocols, had no shear reinforcement at their 400-mm "zero-shear region", whereas the third group of beams, designated for asymmetrical loading, had stirrups over their entire span. Figure 2 depicts reinforcement detailing of the beams, longitudinally and laterally. A uniaxial tensile test was carried out to evaluate the mechanical characteristics of the used steel bars before and after being exposed to elevated heat [ 43 ]. The yield stress, ultimate strength and failure strain at room temperature were found to be 515 MPa, 629 MPa and 16.3% for main (bottom and top) steel bars and at 537 MPa and 622 MPa and 10.7% for the stirrups’ bars. These mechanical properties were slightly affected by the exposure to 450 o C. 4.3 Carbon Fiber-reinforced Polymer Carbon fiber-reinforced polymer ropes were used in this work. The ropes carry the commercial name "Sika Wrap FX-50C" as provided by SIKA Company. They are solid in rolls of 25-m rope length. Their tensile strength, elastic modulus, and strain at failure were reported by the manufacture at 2 kN/mm 2 , 230 kN/mm 2 and 1.6%, respectively. The ropes were saturated with Sikadur-52 resin before being bonded in grooves to concrete using Sikadur-330 epoxy. The manufacturing tensile and adhesion strengths for the first resin are 27 and 10 N/mm 2 as compared to 30 and 4 N/mm 2 for the second epoxy, respectively. The elastic modulus for the latter epoxy is reported at 4.5 kN/mm 2 . 4.4 Concrete Preparation A ready-mix concrete (RMC) with a strength grade of 35 MPa was ordered from the supplier. Wooden formwork with interior dimensions of (150× 250× 1600) mm was used to cast the beam specimens. Concrete was placed in the molds in three layers; each compacted by a poker-type vibrator. Finally, a trowel was used to level the final surface. After 24 hours, the beams were de-molded and then wrapped in wet burlap for a further 27 days for curing. Concrete cylinders (100 mm in diameter by 200 mm) were cast and cured at the same conditions to evaluate the compressive properties of intact and heat-damaged concrete. 4.5 Heat Treatment The beam specimens, designated for heat treatment, were subjected to 450°C for three hours using a large electric furnace following the heating protocol shown in Fig. 3. Upon completion of heat treatment, the furnace cover was left partially open, so that the specimens cool at a rate of 0.40 o C/min. 4.6 Installation of NSM-CFRP Ropes To apply the current strengthening/repair method, parabolic and straight man-made grooves were marked on either side of the specimens. An electrical saw was used to create these grooves at a width of 17 mm and a depth of 17 mm along the beams’ sides with their fan-shaped anchorage created on both end faces. All grooves were cleaned by a vacuum machine before dried using a volatile chemical compound. At the time of installation, the saturating resin (Sikadur®-52) was prepared by blending both of its ingredients using an electric mixer before the CFRP ropes, already cut to the desired lengths, were fully saturated in Sikadur®-52 with excess adhesive removed. After that, another resin (Sikadur®-330) designated for bonding the SNSM-CFRP ropes, was prepared by mixing its two ingredients using an electric mixer. Then, the clean and dry grooves were filled to mid-height with the prepared resin before the ropes (saturated with Sikadur®-52) were precisely placed into the grooves and extended to the anchorage zone at both end surfaces to create a fan-shaped pattern. Finally, another layer of epoxy was applied on the surface of the ropes to fill the grooves at the beams’ sides and over the anchorage ends with extra epoxy scraped off and the surface leveled. The specimens were left to cure for seven days at 23°C according to the manufacturer's instructions. Figure 4 illustrates the end view of the strengthened/repaired beams after the installation of NSM CFRP ropes and their anchorage. 4.7 Test Setup RC beams, belonging to groups I, II, and III, were tested under four-point symmetric, six-point symmetric, and six-point asymmetric loadings, respectively. The loading-cell measurement versus deflection was recorded using a data-recording device with a 2000-kN capacity. Three linear variable displacement transducers (LVDTs) were employed; two were fixed to the two parallel CFRP ropes at the main steel level to measure their elongation, whereas one was positioned at the mid-span of the bottom surface of the beam to measure the vertical deflection. Visual monitoring of crack initiation and propagation leading to failure was performed during testing. The test setup for the two configurations of CFRP under the various loading distributions is schematically presented in Fig. 5. 5. Results and Discussion 5.1 Evaluation of Heat Damage RC beams, designated for heat treatment, were subjected to an elevated temperature of 450°C for three hours. At this level of heating, damage introduced in concrete was mainly caused by the expulsion of capillary and gel water from the concrete’s pore system, generating a high vapor pressure that caused significant distributed cracking on the concrete surface. As seen in Figure 6, the specimens with additional reinforcement exhibited more prominent cracks in terms of intensity. It should be noted that most of the cracks became infeasible after cooling; therefore, the marking presented was made while the beams were still warm. The properties of concrete are also altered negatively by the exposure to this heating regimen, as will be explained later. 5.2 Cracking and Failure Mode under Loading Crack development and patterning were observed and noted and failure modes were determined while the transverse load was applied at a rate of 0.3kN per second. Cracks’ initiation and development until the failure of control and heat-damaged beams at 450 o C under different loading protocols are described herein. 5.2.1 Control and Heat-damaged B eams Under symmetrical loading, control (C4PL/C6PL) and heat-damaged RC beams (HD 450 -4PL/HD 450 -6PL) demonstrated a flexural mode of failure, as shown in the photos of Figure 7 (a-f). For control specimens, flexural cracks first emerged at loads of 29 and 45 kN around the middle of the span of the beams for loading conditions of 4PL and 6PL, respectively. As the load was increased, cracks started developing in the high-shear zones before both flexural and shear cracks spread more quickly upward into the compression zone with further loading, reflecting the quick shift in the neutral axis caused by the yielding of reinforcing steel. This process continued until the crushing of compression concrete at failure points of 112 kN and 191 kN, respectively. On the other hand, beams, pre-damaged at an elevated temperature of 450 o C, then tested under symmetrical-loading conditions (4PL/6PL), experienced their first flexural cracks around the mid-span at loads of 28kN and 40 kN, respectively. Afterward, more cracks appeared in the high-moment and shear regions that developed towards the compression zone with increasing load, resulting in a common flexural failure at load values of 97kN and 173 kN, respectively. Comparison between the impact of the two symmetrical loading regimes in terms of cracks development and failure modes in tested beams demonstrated that load-generated cracks tended to be more concentrated in the middle region of the span for the beams subjected to 4-point loading (4PL), yet tended to be more distributed along the span of those beams loaded with 6PL, allowing these beams to experience more deflection. Under A6PL asymmetrical loading distributions, a similar failure mechanism was recognized for control and heat-damaged (at 450°C) beams (C-ASY/HD450-ASY), as shown in the photos of Figure 7 (c, f). Flexural cracks first emerged with loads of 40 kn and 16 kN for each of the control and heat-damaged specimens, respectively. These initiated below the point at which a higher load was applied on the right portion of the beam. As loads increased, more flexural cracks appeared between the 4 points of loading along the beam span but remained more concentrated under the higher load. Here, the cracks showed higher width and extension rate (upward) into the compression zone. With further load increase, the neutral axis shifted quickly upwards due to the yielding of reinforcing steel. This process continued until the crushing of compression concrete at a final load of 174 kN and 150 kN for control and heat-damaged specimens, respectively. This took place below the point at which the higher portion of the total load was applied, respectively. Heat-damaged specimen (HD450-ASY) experienced concrete-cover separation in the segment of the beam where the higher portion of the load was applied due to the increased vertical shear, hence resulting in horizontal shearing stresses. It is clear that under asymmetrical-loading distribution, the control and heat-damaged beams underwent more deflection and higher cracking intensity (within the failure zone) compared to beams subjected to symmetrical loading. 5.2.2 Strengthened Undamaged Beam s The cracking patterns for different strengthened beams are depicted in the photos of Figure 8 (a–f). Flexural cracks emerged at loads of 34, 36, 49, and 50 kN around the middle span of beams C-SSP-4PL, C-SPP-4PL, C-SSP-6PL, and C-SPP-6PL, respectively. As the load increased, cracks appeared in the high-shear zones before flexural failure and shear cracks propagated at a higher rate upwards into the compression zone. This process continued until ultimate loads of 177, 197, 299, and 305 kN were attained, respectively. The rupture of the CFRP ropes occurred suddenly; resulting in high reactive forces that caused concrete-cover separation at the center of these beams. Simultaneously, the moment of inertia of the beams’ section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating a flexural ductile failure. The impact of distributing the load at four instead of two points around the middle upon cracking extent and failure mode can be understood by comparing photos of Figure 8 (a-d). Regardless of the strengthening configuration, the cracking spreading along the span was more obvious in the beams loaded under 4 points. This is attributed to the extension of some of the flexural cracks, developed near the end supports, at an inclination toward the compression zone. The mechanism of failure under asymmetrical loading was similar for both strengthened beams (C-SSP-ASY/C-SPP-ASY), as shown in the photos of Figure 8 (e, f). Flexural cracks emerged at loads of 57 kN and 50 kN for the beams with straight and parabolic profiles, respectively. Specifically, the cracks initiated below the higher portion of the load on the right side of the beam, then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 loading points along the beam span and remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. This process continued until ultimate loads of 300 kN and 289 kN were reached, respectively. The rupture of the CFRP ropes occurred suddenly at this time, resulting in strong reactive forces that caused concrete-cover separation in the right portion of the beam below the main load application point. Simultaneously, the moment of inertia of the beams’ section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure. 5.2.3 Heat-damaged at 450°C and Repaired Beams The cracking patterns of different repaired beams are depicted in the photos of Figure 9 (a–f). Flexural cracks emerged at loads of 33, 29, 52, and 47 kN around the middle span for beams HD450-RSP-4PL, HD450-RPP-4PL, HD450-RSP-6PL and HD450-RPP-6PL, respectively. As the load was increased, cracks appeared in high-shear zones before flexural failure and shear cracks propagated at a higher rate upwards into the compression zone. This process continued until ultimate loads of 160, 161, 282, and 292 kN were attained, respectively. The rupture of the CFRP ropes occurred suddenly, resulting in high reactive forces that caused concrete-cover separation at the center of these beams. Simultaneously, the moment of inertia of the beams’ section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure. The impact of distributing the load at four instead of two points around the middle upon cracking extent and failure mode can be understood by comparing the photos of Figure 9 (a-d). Regardless of the repair scheme, the cracking spreading along the span was more obvious in the beams subjected to loading at a higher number of points. It is also clear that the developed shear cracks extended more toward the supports for these beams to generate an increased number of cracks between the supports. The mechanism of failure under asymmetrical-loading distributions is shown in the photos of Figure 9 (e, f) for the beams HD450-RSP-ASY and HD450-RPP-ASY. For the HD450-RPP-ASY specimen, flexural cracks emerged at loads of 36 kN below the higher portion of the load on the right side of the beam and then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 points of loading along the beam span, but they remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. This process continued until an ultimate load of 247 kN was reached. The rupture of the CFRP rope occurred suddenly at this time, resulting in strong reactive forces that caused concrete-cover separation in the right portion of the beam below the load-application point of higher proportion. Simultaneously, the moment of inertia of the beams’ section was reduced to shift the neutral axes quicker into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure. Specimen HD450-RSP-ASY showed a different mode of failure, where flexural cracks emerged at a load of 40 kN below the higher portion of the load on the right side of the beam and then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 points of loading along the beam span, but they remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. The end concrete cover eventually delaminated at a failure load of 270 kN, following the formation, then a horizontal crack propagated toward the middle span from the right side of the beam where higher load portions acted. 5.3 Mechanical Response The mechanical performance of RC beams is assessed under different loading protocols (4PL/6PL/A6PL). The load-deflection response is evaluated along with its characteristics; namely, ultimate load capacity, yielding load, first-crack load, stiffness, toughness, and displacement ductility. The slope of the linear segment and the area underneath the load-deflection curve reflect stiffness and toughness, respectively, whereas the deflection ratio at the failure point to that at steel yielding reflects displacement ductility. All mechanical characteristics were summarized in Table 2 for all beams (control, heat-damaged, strengthened, and repaired beams) for the three loading protocols considered in this study. 5.3.1 Control and Heat-damaged Beams The load-deflection curves of the control and heat-damaged beams showed similar patterns under the three types of loading. These curves initially followed an approximately linear pattern up to reinforcing-steel yielding before departing from linearity. The load-deflection characteristics of Table 2 indicate that the intact RC beams demonstrated different loading capacities under the three loading protocols: flexural load capacity reached 191, 174 and 112 kN for beams C-6PL, C-ASY, and C-4PL, respectively. These correspond to moment capacities of 33.4, 34.5, and 30.8 kN.m, respectively. The stiffness of the control beam specimens reached 25, 23, and 14 GPa for beams C-6PL, C-ASY, and C-4PL, respectively. More evenly distributed stresses were present in specimens subjected to six points of loading, whether in symmetrical or asymmetrical distribution. Accordingly, normal compressive and tensile stresses were distributed along the span to reduce stress on top and bottom concrete. Consequently, premature beam cracking and failure were prevented to enhance stiffness and moment capacity. In contrast, ductility and toughness were the highest for beam C-6PL, yet the lowest for beam, as reported in Table 2. The uniformly distributed loads under 6PL allowed a better distribution of induced stress to allow more deflection of the beams before failure. The results of Table 2 showed a drop in flexural load capacity for beams HD450-6PL, HD450-4PL, and HD450-ASY by 10%, 14%, and 14% in comparison to relevant intact ones, respectively. Surprisingly, the stiffness of the present beam was unaffected by heating to 450°C for three hours, although the load capacity was tangibly decreased. Apparently, the elastic modulus of the reinforcing steel, not affected by heating, dictated the stiffness of the concrete section. Upon heating, the rotational ductility was decreased by 1%, 4%, and 16% and the toughness decreased by 3%, 17%, and 29% of their original values. The A6PL loading distribution resulted in higher stresses under the application point where the higher proportion of the load acted and tended to reduce the original ductility and toughness for the relevant beam, noticeably. It is also clear that distributing loading in a symmetric manner is more beneficial in maintaining the latter two properties upon heating. 5.3.2 Strengthened Undamaged Beams Figure 10 shows the load versus displacement curves for strengthened beams under 4PL, 6PL, and A6PL, as compared to those of the intact beams, respectively. These curves followed an approximately linear pattern initially up to a certain point before departing from linearity. The major characteristics of these curves were obtained and listed in Table 2. The strengthening techniques adopted resulted in a significant increase in the flexural load capacity for the beams C-SSP-4PL, C-SPP-4PL, C-SSP-6PL, C-SPP-6PL, C-SSP-ASY, and C-SPP-ASY by 58, 76, 57, 60, 73 and 66% compared to the original values, respectively. In contrast, the relevant residuals for stiffness and toughness were increased by (14, 27, 13, 20, 33, and 35%) and (1, 43, 42, 45, 90 and 64%), respectively. As expected, the relevant ductility was decreased to (67, 86, 83, 94, 97 and 95%) of the original values, respectively. These findings showed that under the static symmetrical loading distributions, the parabolic profile with NSM CFRP ropes achieved higher enhancements in load capacity, stiffness, toughness, and ductility than those of the straight profile, owing to the higher embedment length of the curved NSM CFRP ropes coupled with a lower tendency of the beams towards concrete-cover separation. This is referred to the deviation of the parabolic profile from the critical separation zone near both end supports. Under asymmetric loading, the straight profile imparted higher improvements to load capacity and toughness than those of the parabolic profile because of the lower contribution of the ropes of the latter profile under the critical-loading point to flexural resistance. The results depicted in Figure 10 reflect the negative impact of using a parabolic profile of NSM CFRP ropes on load capacity and stiffness in cases involving higher distribution of acting loads. The comparison between the present beams under asymmetric A6PL and symmetrical 6PL is in favor of the first in terms of all the considered mechanical characteristics, regardless of the rope profile considered. This can be easily explained from a statics point of view. Exposing a simply supported beam to a larger portion of its load at locations closer to the support points would generate a lower moment, which helps delay concrete failure. As a result, the load at failure and the corresponding ductility would be higher compared to those under symmetric loading. It is also logical to anticipate that the contribution of the straight NSM CFRP ropes to mechanical characteristics is higher under asymmetric loading, which is due to the higher resisting moment arm of the NSM CFRP rope along the entire beam span. This allowed more resistance to flexural stresses, which helped delay crack propagation to yield higher deflection at the failure point. 5.3.3 Heat-damaged at 450°C and Repaired Beams Figure 11 shows the load versus displacement curves for heat-damaged and repaired beams as compared to those of the control beams under the different loading protocols (4PL, 6PL, and A6PL). These curves followed an approximately linear behavior up to a certain point before bending over until the failure point. The major characteristics of these curves were obtained and listed in Table 2. The repair techniques adopted resulted in a significant increase in the flexural load capacity for the beams (HD450-RSP-4PL, HD450-RPP-4PL, HD450-RSP-6PL, HD450-RPP-6PL, HD450-RSP-ASY, and HD450-RPP-ASY) by (43, 43, 48, 53, 55 and 42%) compared to their original value, respectively. In contrast, the relevant residual stiffness was increased by (32, 25, 17, 34, 34 and 37%). Except for the beam (HD450-RSP-4PL), other beams achieved an increase in relevant toughness (4% to 54%), depending on the loading and repair profile adopted. Beams subjected to symmetric loading lost partially their displacement ductility in the range of (7% to 22%), whereas those subjected to asymmetric loading showed an increase of (31% and 16%) for straight and parabolic profiles, respectively. The results of Table 2 reflect the negative impact of localizing loading on the heat-cracked concrete beams. As a result, beams subjected to loading at four instead of two points along their spans attained the same load capacity and stiffness, yet higher toughness and ductility (deflection). It was also revealed that under asymmetric loading, the beams were able to withstand higher loads and deflected more to achieve the highest residuals in the four characteristics studied. It is also evident that the use of straight instead of parabolic profile of NSM CFRP ropes in repair is advantageous for asymmetric loading, but has an unclear impact on the cases with symmetric loading. 5.4 Efficiency of Strengthening/Repairing Techniques 5.4.1 Performance Factor The overall performance factor (PF), as determined using Equation (1), was used to examine the impact of the loading protocol in conjunction with the strengthening profile [44]. According to the definition of PF in Equation (1), the ratio between the ultimate strength and ultimate deflection to their values at service stress (corresponding to strain in concrete at 0.001) provides a clear picture of the ability of the strengthening/repair technique to achieve the required serviceability and safety. The PF values were calculated using Equation (1) before being listed in Table 3. The results of Table 3 demonstrate that the strengthening/repair procedures employed were effective as the PF values varied from 5.44 to 7.87 for strengthened specimens compared to values from 10.88 to 16.3 for repaired specimens. The drastic increase in PF for the concrete heat-damaged beams before being repaired is attributed to the enhancement in their deformability. The PF gives a clearer picture regarding the impact load distribution than that drawn based on mechanical characteristics. It is clear that load distribution had a positive impact on both strengthened and repaired beams’ performance; especially when the straight profile of NSM CFRP ropes was used. This could be attributed to the increased deformability of the beams as the load stresses are distributed more uniformly along the beam span. The results show also that applying asymmetrically distributed loading yielded the highest PF, especially when a straight profile of the NSM CFRP ropes was implemented. The results of Table 3 revealed that the contribution of the parabolic profile of the NSM CFRP ropes seemed to be undermined in repaired beams as compared to that in strengthened beams when subjected to symmetric loading. In contrast, the use of a straight profile of NSM CFRP ropes is advised for beams strengthened or repaired to resist asymmetric loading. 5.4.2 Strain Induced in CFRP Ropes The strain in CFRP ropes was measured experimentally using two LVDTs, which were mounted to the ropes on either side of the beams. For part of the beams, the readings were not correctly collected. Therefore, the principle of strain compatibility and equilibrium was used to determine the theoretical strain in the ropes based on the achieved load capacity with results listed in Table 4. The residual strains computed with respect to the ultimate strain capacity, provided by the CFRP rope manufacturer, declined for heat-treatment and repaired beams in comparison with those strengthened with similar repair configurations and test conditions. The residual strain in the CFRP ropes at the failure point ranged from 82% to 100% for strengthened beams but was reduced to lower limits for heat-damaged beams at roughly 52% to 95%. Only for the repair case where concrete-cover delamination occurred under loading, the residual strain degrades below 70%. 6. Conclusions Based on the experimental work previously described, the following conclusions can be drawn: Exposing concrete beams to 450 o C for three hours resulted in significant distributed cracking on a concrete surface that degraded the load capacity by as high as 14% and the toughness by as much as 29%, regardless of the loading protocol applied. Strengthening with NSM CFRP ropes boosted the flexural load capacity, stiffness, and toughness under different loading protocols by (57-76)%, (13-35)%, and (1-90)%, yet resulted in degrading the displacement ductility to (67-97) % of their original values, respectively. Under static symmetrical loading distributions, the concrete beams strengthened with a parabolic profile of NSM CFRP ropes achieved higher enhancements in load capacity, stiffness, toughness, and ductility than those with a straight profile. In contrast, beams, strengthened with straight NSM CFRP ropes seemed to behave better under asymmetrical loading than those with parabolic profile due to their higher resisting moment arm along the entire span. Repairing the beam post-heated at 450 o C using both straight and parabolic profiles of SNSM-CFRP ropes resulted in a significant increase in the flexural load capacity and stiffness in the ranges of (42-55%) and (17-37%) compared to their original values, respectively. Heat-damaged and repaired concrete beams subjected to symmetric loading lost partially their displacement ductility in the range of 7% to 22%, whereas beams, subjected to asymmetric loading showed an increase of 31% and 16% for straight and parabolic profiles, respectively. Intact and heat-damaged (at 450 o C) beams, strengthened/repaired using SNSM CFRP ropes, experienced flexural failure followed by bottom concrete-cover separation caused by the reactive forces generated from the rapture of CFRP rope at the point failure, except for that heat-damaged and repaired with straight rope profile and subjected to asymmetric loading. Declarations Acknowledgement The authors acknowledge the financial support by the deanship of research at Jordan University of Science and Technology (Irbid-Jordan) under project number 498/2022. Conflict of interest The authors testify that they have no conflict of interest in publishing this article at Materials and Structures. 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Experimental and numerical investigation on low-strength RC beams strengthened with side or bottom near surface mounted FRP rods. Struct Infrastruct Eng. 2022;1–16. Murad Y, Abu-AlHaj T. Flexural strengthening and repairing of heat damaged RC beams using continuous near-surface mounted CFRP ropes. In: Structures. 2021. p. 451–62. Available from: https://doi.org/10.1016/j.istruc.2021.04.079 Haddad RH, Harb AN. CFRP ropes for retrofitting heat-damaged concrete beams. J Build Eng. 2021;43:102522. Available from: https://doi.org/10.1016/j.jobe.2021.102522 ASTM C. Standard test method for density, relative density (specific gravity) and absorption of fine aggregate. 2012. ASTM A. Standard Test Method for Relative Density (Specific Gravity) and Absorption of Coarse Aggregate. ASTM West Conshohocken, PA; 2015. ASTM Committee C09. Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. ASTM Standards. ASTM C39/C39M-10. West Conshohocken, USA: ASTM International; 2010. 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Tables Tables 1 to 4 are available in the Supplementary Files section Supplementary Files ListofTablesmodified.docx Cite Share Download PDF Status: Published Journal Publication published 09 Jan, 2025 Read the published version in Materials and Structures → Version 1 posted Reviewers agreed at journal 26 Jun, 2024 Reviewers invited by journal 02 Jun, 2024 Editor invited by journal 26 May, 2024 Editor assigned by journal 20 May, 2024 First submitted to journal 17 May, 2024 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. We do this by developing innovative software and high quality services for the global research community. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-4434850","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":309624315,"identity":"4ceaaa85-e349-465e-be50-50077eaf567f","order_by":0,"name":"Rami Haythem Haddad","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA20lEQVRIiWNgGAWjYDACCSDiYWCWY2wAc5mB+ABxWoyBWkC6SNCSCFQO00IAmM9ufnjjTY11evOM9OcPGCqsExsYD+O3RubOMWPLOcfScxtn5Bg2MJxJB1p3LAG/uyQSzKR52A6DtDA2MLYdBmo5Y0BAS/o3aZ5/h9MZZ6Q/bGD8R5SWHDNp3rbDCYwzEgwbGBuI01JsObcv3bCx543hjIRj6cZthP2SvvHGm2/W8obt6Q8+fKixlu2XIBBicAAMLgYGkPFsEkTqYJCHs/gbiNQyCkbBKBgFIwUAAJTISm/7tMVdAAAAAElFTkSuQmCC","orcid":"https://orcid.org/0000-0003-1700-9805","institution":"Jordan University of Science and Technology","correspondingAuthor":true,"prefix":"","firstName":"Rami","middleName":"Haythem","lastName":"Haddad","suffix":""},{"id":309624316,"identity":"9af2cbae-b34a-49a4-9adf-75b952bb1991","order_by":1,"name":"Rawan S. Obeidat","email":"","orcid":"","institution":"Jordan University of Science and Technology","correspondingAuthor":false,"prefix":"","firstName":"Rawan","middleName":"S.","lastName":"Obeidat","suffix":""}],"badges":[],"createdAt":"2024-05-17 07:12:49","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-4434850/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-4434850/v1","draftVersion":[],"editorialEvents":[{"content":"https://doi.org/10.1617/s11527-025-02569-1","type":"published","date":"2025-01-09T15:56:54+00:00"}],"editorialNote":"","failedWorkflow":false,"files":[{"id":58362404,"identity":"ebf61975-f58c-4abb-a456-7630a7781a71","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":15663,"visible":true,"origin":"","legend":"\u003cp\u003eThe stress-strain relation of the concrete before and after heating.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/9d0d4c30a307844d0d7ca5d6.png"},{"id":58362411,"identity":"8edf250d-2a4f-4f08-a33b-1356e02d51eb","added_by":"auto","created_at":"2024-06-14 11:40:02","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":63496,"visible":true,"origin":"","legend":"\u003cp\u003eReinforcement details of the beams under symmetrical and asymmetrical loading protocols.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/a72806ca20892dcc00e2bae5.png"},{"id":58362416,"identity":"2794f9c2-24fe-4220-9b44-f48c326a3914","added_by":"auto","created_at":"2024-06-14 11:40:03","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":17792,"visible":true,"origin":"","legend":"\u003cp\u003eHeat treatment protocols adopted in the present study.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/8da6e4cb7a95f464f7c9adf0.png"},{"id":58362410,"identity":"2ff3bd3a-d733-4592-b12f-d59c35a1855e","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":55420,"visible":true,"origin":"","legend":"\u003cp\u003eSections for strengthened beams explain the position of ropes and end anchorage system used for both straight and parabolic profiles of CFRP ropes used.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/6ea9d63d5364af7246edad50.png"},{"id":58362406,"identity":"dc1ca7b2-9178-4417-98a7-2011b2838bcf","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":116109,"visible":true,"origin":"","legend":"\u003cp\u003eTesting setup of present beams under different loading configurations.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/30c974cb4084a73b335f2d77.png"},{"id":58362407,"identity":"8cbbe368-d269-4572-8c24-14df7aa773ed","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"png","order_by":6,"title":"Figure 6","display":"","copyAsset":false,"role":"figure","size":247487,"visible":true,"origin":"","legend":"\u003cp\u003eSurface cracking patterns on the surfaces of the heat-treated RC beams.\u003c/p\u003e","description":"","filename":"6.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/e02acd9e08df4866279a48d9.png"},{"id":58362415,"identity":"abc9865f-f1a1-492d-b46d-6ee604521360","added_by":"auto","created_at":"2024-06-14 11:40:03","extension":"png","order_by":7,"title":"Figure 7","display":"","copyAsset":false,"role":"figure","size":372031,"visible":true,"origin":"","legend":"\u003cp\u003eFailure modes for control and heat-damaged beams under different loading protocols (4PL/6PL/6PL-Asymmetric).\u003c/p\u003e","description":"","filename":"7.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/29fbb4765b0596d8ffa7a9a0.png"},{"id":58362412,"identity":"ed488b9d-626b-4513-962d-5ac6613e5f6e","added_by":"auto","created_at":"2024-06-14 11:40:02","extension":"png","order_by":8,"title":"Figure 8","display":"","copyAsset":false,"role":"figure","size":490452,"visible":true,"origin":"","legend":"\u003cp\u003eFailure modes for strengthened beams under different loading protocols (4PL/6PL/6PL-A6PL).\u003c/p\u003e","description":"","filename":"8.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/9337459a1aa84d31aaf9dc29.png"},{"id":58362413,"identity":"4b8e5207-70bf-4c20-9e20-010891e539ad","added_by":"auto","created_at":"2024-06-14 11:40:02","extension":"png","order_by":9,"title":"Figure 9","display":"","copyAsset":false,"role":"figure","size":489244,"visible":true,"origin":"","legend":"\u003cp\u003eFailure modes for repaired beams under different loading protocols (4PL/6PL/6PL-Asymmetric).\u003c/p\u003e","description":"","filename":"9.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/34ebe05f3abd2335b98fe700.png"},{"id":58362414,"identity":"d9769b18-cad7-408c-997c-f5a7b9dc4d62","added_by":"auto","created_at":"2024-06-14 11:40:02","extension":"png","order_by":10,"title":"Figure 10","display":"","copyAsset":false,"role":"figure","size":43384,"visible":true,"origin":"","legend":"\u003cp\u003eLoad-deflection curves for control-strengthened beams under different loading protocols (4PL/6PL/6PL-Asymmetric).\u003c/p\u003e","description":"","filename":"10.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/180d60f09bbbd656fc2827c5.png"},{"id":58362409,"identity":"13355ba7-6df5-47ae-a551-a37bb0d2a505","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"png","order_by":11,"title":"Figure 11","display":"","copyAsset":false,"role":"figure","size":44398,"visible":true,"origin":"","legend":"\u003cp\u003eLoad-deflection curves for heat-damaged and repaired beams under different loading protocols (4PL/6PL/6PL-Asymmetric).\u003c/p\u003e","description":"","filename":"11.png","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/84dbd68f2884ef3dd6d390d2.png"},{"id":73693765,"identity":"bb6b3541-dc61-4d16-8698-9cd7f849fb69","added_by":"auto","created_at":"2025-01-13 16:05:43","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":3937224,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/0f715f0e-1d29-4948-aea3-0a00544de418.pdf"},{"id":58362405,"identity":"606aca45-3d94-4870-94e0-5b779d56a4ae","added_by":"auto","created_at":"2024-06-14 11:40:01","extension":"docx","order_by":1,"title":"","display":"","copyAsset":false,"role":"supplement","size":38819,"visible":true,"origin":"","legend":"","description":"","filename":"ListofTablesmodified.docx","url":"https://assets-eu.researchsquare.com/files/rs-4434850/v1/1d2c212fa8cebb019517dd47.docx"}],"financialInterests":"","formattedTitle":"Impact of Loading Protocol on the Repair Efficiency of Heat-damaged Concrete Beams with SNSM CFRP Ropes","fulltext":[{"header":"1. Introduction","content":"\u003cp\u003eConcrete is one of the most common construction materials due to its superior features of durability and compressive strength, as well as its low coefficient of thermal expansion. Over time, reinforced concrete (RC) structures could be subjected to devastating environmental impacts, such as fire, sulfate attack, freezing and thawing, or corrosion of steel reinforcement. Under fire, concrete becomes physically damaged with limited chemical changes at a temperature of about 450\u0026deg;C [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. The resulting damage is manifested by extensive surface cracking and possible spalling of concrete elements with significant losses in their mechanical performance [\u003cspan additionalcitationids=\"CR3\" citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Extended exposure of concrete elements to fire attack may destroy their concrete cover and undermine the mechanical performance of embedded steel reinforcement and its bond to concrete [\u003cspan additionalcitationids=\"CR6 CR7 CR8\" citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. It is proved that the temperature level of a fire and its duration are the two most significant determinants of heat damage in concrete [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. The current database revealed that most fire-damaged structural elements are repaired to restore their mechanical performance and raise the structural safety of relevant facilities [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e].\u003c/p\u003e \u003cp\u003eSince more than two decades ago, most concrete structural elements have been repaired using externally bonded fiber-reinforced polymer (FRP) composites due to their exceptional qualities, including their high strength-to-mass ratio and anticorrosive qualities [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e, \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. However, this repair methodology's practical and economic efficiency was undermined by the premature separation of the FRP composites [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. As an alternative, near-surface-mounted (NSM) FRP composites emerged as a new repair method that contributes to resolving the bond problem associated with externally bonded FRP composites. NSM CFRP composites in the form of rods, strips, or ropes are inserted in epoxy-filled grooves created in the concrete cover of a flexural element [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan additionalcitationids=\"CR16 CR17 CR18\" citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. The NSM FRP technique typically outperforms the externally bonded FRP method due to its lesser sensitivity to detachment and damage from the sun, fire, and direct loads. Furthermore, its implementation requires shorter time and effort while maintaining the aesthetic view [\u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Several experimental investigations have been conducted to assess the flexural performance of beams strengthened with NSM FRP composites [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. According to Sharaky \u0026amp; Salam [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e], the stiffness and bearing capacity of fully bonded NSM FRP-enhanced beams were higher than those of partially bonded ones. They claimed that concrete-cover separation starts at the cut-off points to cause the failure of strengthened beams and that end anchorage had a negligible impact on the composite behavior of the beams inside the constant-moment zone. Later, Haddad \u0026amp; Almomani [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e] examined how the configuration and staggering of the NSM CFRP strips affected the effectiveness of repairs. Results demonstrated that NSM CFRP strips contributed to increasing the load capacity, yet reducing the ductility of the concrete beams, depending on the embedment length.\u003c/p\u003e \u003cp\u003eTo reduce or eliminate the tendency towards premature concrete-cover separation, some research attempts were made to insert NSM CFRP composites within the side covers (SNSM) of the beams [\u003cspan additionalcitationids=\"CR21 CR22\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. According to Hosen et al. [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e], the SNSM approach significantly improved the flexural performance of RC beams, increasing the ultimate and yield load-carrying capacities of the beams by a factor of 2.38 and 2, respectively, with an improvement in the cracking load by about (3.17 times). Abdallah et al. [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e] compared the strengthening efficiency of concrete beams with SNSM CFRP rods to that with bottom NSM techniques to conclude that the SNSM approach had caused higher reductions in the ductility and deflection at the ultimate load. Haddad and Harb [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e] examined the effectiveness of mounting SNSM CFRP ropes at straight, trapezoidal, step-wise, and parabolic profiles on control and heat-damaged beams. The findings revealed that trapezoidal and parabolic profiles were effective in delaying concrete-cover separation and hence promoting the benefit of strengthening or repair. Heat-damaged (at 500\u003csup\u003eo\u003c/sup\u003eC) and repaired beams demonstrated a shear-type failure instead of a typical flexural failure.\u003c/p\u003e \u003cp\u003eMost of the database for FRP-strengthened/repaired beams was acquired under the effect of symmetric loading at three or four contact points. This limited the benefit of relevant findings, because the distribution of shear and bending stresses, along the span of the NSM CFRP retrofitted beams, determines the tendency toward concrete-cover separation. A few researchers have looked at the impact of load uniformity on the behavior of RC beams, strengthened in flexure with externally bonded (EB) FRP plates/sheets [\u003cspan additionalcitationids=\"CR26 CR27\" citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Pan et al. [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e] found that the load uniformities influence the detachment tendency in concrete beams with EB FRP composites, hence affecting their load-carrying capacity. In contrast, Fu et al. [2018] stipulated that load uniformity led to greater load-carrying capacity and deformation capabilities for beams of different shear span ratios and strengthened with EB composites. Mazzotti and Savoia [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e] claimed that using FRP sheets is more effective than using pultruded plates for strengthening under a uniformly distributed load in the form of eight contact points. Thomsen et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] showed that RC beams, strengthened with EB FRP plates, often perform more effectively under distributed loads compared to the case with four-point bending loading situations. The first-ever experimental and numerical study into how load uniformity affects the behavior of NSM FRP-strengthened concrete beams was carried out by Zhang et al. [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]. They concluded that the load uniformity was influential when the failure of the strengthened beams was governed by concrete-cover separation.\u003c/p\u003e \u003cp\u003eA few researchers tackled the impact of load symmetry on the performance of FRP-strengthened RC beams [\u003cspan additionalcitationids=\"CR31 CR32 CR33\" citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Razaqpur et al. [\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e] examined the effect of the asymmetrical loading on FRP shear-strengthened beams with different shear span-to-depth ratios. They stipulated that moment and shear interaction can be considered for shear span-to-depth ratios of less than 2.5, yet disregarded for greater ratios where shear behavior becomes dominant. The impact of asymmetrical loading in continuous concrete beams with glass FRP was studied by Rahman et al. [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Three loading scenarios were considered: loading both spans equally, loading one span at a load ratio of 1.5 of the other\u0026rsquo;s, and loading one span only. Compared to beams tested under symmetrical loading, those tested under asymmetrical loading experienced reduced crack widths, strains, and deflections in the greater load span. Additionally, moment redistribution was negatively impacted by the asymmetrical loading circumstances. Hawileh et al. [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e] focused on examining the shear capacity of CFRP-reinforced concrete beams using three-dimensional finite element (FE) models. The researchers concluded that the FE models that they developed provided reliable insights into the shear behavior of CFRP-reinforced concrete beams under asymmetrical loading conditions. Finally, Tiejiong et al. [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] explored potential alternatives to address the issue of corrosion by replacing steel bars with FRP bars in externally pre-stressed concrete continuous beams exposed to different loading regimes. Compared to symmetric-loading conditions, asymmetric-loading conditions caused higher mid-span deflection, but lower tendon stress.\u003c/p\u003e"},{"header":"2. Problem Statement","content":"\u003cp\u003eIn any structure, concrete beams are the most susceptible elements to fire attack, especially central ones; receiving significant damage when the fire period extends beyond 2 hours. Repair of these elements with EB-CFRP composites provided limited advantages in terms of strength and stiffness recovery; owing to the premature detachment of the composites. In contrast, NSM CFRP composites proved to be more effective, especially when implemented on the side at the straight or variable profile [\u003cspan additionalcitationids=\"CR21 CR22 CR23\" citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan additionalcitationids=\"CR36\" citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. Recent studies indicated that SNSM CFRP ropes used in retrofitting concrete beams tended to fail by the composite\u0026rsquo;s rupture; especially when implemented on the side at a variable profile [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e, \u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e]. The above behaviors were noticed for one case of loading which involves subjecting the beams to two equal loads at two contact points around the center of the beams. The impact of distributed and asymmetric loadings on the performance of concrete beams with EB-FRP composites was investigated previously. However, no approved works have tackled the impact of the latter two loading regimes upon the behavior of concrete beams with SNSM CFRP ropes.\u003c/p\u003e"},{"header":"3. Objectives and Scope","content":"\u003cp\u003eThe present work sheds light on the impact of loading distribution and asymmetry upon the efficiency of retrofitting heat-damaged beams with straight and parabolic profiles of SNSM CFRP ropes. For comparison purposes, identical intact beams were strengthened using similar CFRP rope configurations before tested under the same loading conditions. The implementation of SNSM CFRP ropes at a parabolic profile aimed at delaying or preventing concrete cover separation throughout the high shear zone.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eEighteen reinforced concrete beams with dimensions of (150 × 250 × 1600 mm) in (width, depth, and length), respectively, were cast using a ready-mix concrete (RMC) having a strength grade of 35 MPa before being cured for 28 days in wet burlap until becoming matured.\u0026nbsp;The eighteen beams were divided into three groups of six each. In each group, two beams were designated for determining the flexural performance of the intact beam and that heat-damaged at 450\u003csup\u003eo\u003c/sup\u003eC, while two intact and two heat-damaged beams were strengthened/repaired with straight and parabolic profiles of SNSM CFRP ropes. The specimens in groups I, II, and III were tested under the effect of four-point symmetric, six-point symmetric, and six-point asymmetric loadings, respectively. A summary of test specimens and their designations is provided in Table 1. The relatively large specimen size used in the present work helped minimize possible experimental error related to materials variability. Hence, we believe that the differences in the mechanical properties among the present beams reflected mainly the impact of heating, repair regime and loading protocol [24-34].\u003c/p\u003e"},{"header":"4. Experimental Work","content":"\u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003e4.1 Aggregate Properties and Concrete Mixture\u003c/h2\u003e \u003cp\u003eA ready-mix concrete (RMC) with a strength grade of 35 MPa was used in casting all specimens of this study. The mixture was prepared using Type-II Portland Cement and tap water, with coarse limestone aggregate (at a maximum aggregate size of 19 mm), medium-size coarse aggregates, crushed sand, and silica sand at proportions of 20%, 24%, 20%, and 36%, respectively. A superplasticizer having a commercial designation of Flocrete SO720 was added to the mixing process at a dosage of 9 liter/m\u003csup\u003e3\u003c/sup\u003e to improve workability during the casting process. The physical aggregate properties of all aggregate components were determined by the concrete\u0026rsquo;s manufacturer according to the ASTM testing procedure [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e, \u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. The bulk specific gravity (dry) for coarse, medium and fine limestone aggregate are 2.59, 2.58, 2.58, respectively, whereas that for silica sand is 2.60. The relevant absorptions are 2, 1.9, 2.6, and 0.9%, respectively. The fineness of the blend of fine limestone and silica sand is 2.8. Tests on trial mixes showed that the mixture attained a slump of 170 mm during casting time and an average compressive strength of 35 MPa and 42 MPa at ages of 7 days and 28 days, respectively. The proportions of gross water, cement, coarse aggregates, medium aggregates, crushed sand, and silica sand were used at 167, 325, 374, 449, 370, and 675kg/m\u003csup\u003e3\u003c/sup\u003e, respectively. The concrete was batched at the ready-mix plant by weight with 2 m\u003csup\u003e3\u003c/sup\u003e delivered for casting.\u003c/p\u003e \u003cp\u003eIn this study, uniaxial-compression tests were carried out on standard concrete cylinders (100 \u0026times; 200 mm) to determine the compressive strength before and after exposure to 450\u003csup\u003eo\u003c/sup\u003eC [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]. Cylindrical specimens (150 \u0026times; 300 mm) were also cast to determine the compressive stress-strain diagram for the present concrete before and after being damaged by heating [\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. The results showed that there was a noticeable degradation in the compressive strength of concrete after being heated at 450\u0026deg;C for 3 hours at a residual of 29%, the compressive strength of the intact cylinders averaged 42 MPa, as compared to 30 MPa for those heat-damaged. The stress-stain response acquired indicated an increase in strain at ultimate stress from about 0.0025 for intact concrete to about 0.0035 for heat-damaged concrete. The stress-strain relation of the concrete before and after heating is depicted in Fig.\u0026nbsp;1.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec6\" class=\"Section2\"\u003e \u003ch2\u003e4.2 Reinforcement Detailing and Properties\u003c/h2\u003e \u003cp\u003eThe steel reinforcement was determined according to ACI 318 to ensure that flexural failure occurs before shear failure in all RC beams [\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. All beams were strengthened with the same type and quantity of deformed steel bars, employing 2Φ12 bars for tension reinforcement and other 2Φ12 bars for hungers. Such reinforcement ensures that flexural failure occurs before shear failure. The high shear zones of the beams were strengthened with Φ10 stirrups at a center-to-center spacing of 100 mm to prevent shear failure, regardless of the loading scheme. The first two groups, designated for symmetrical-loading protocols, had no shear reinforcement at their 400-mm \"zero-shear region\", whereas the third group of beams, designated for asymmetrical loading, had stirrups over their entire span. Figure\u0026nbsp;2 depicts reinforcement detailing of the beams, longitudinally and laterally.\u003c/p\u003e \u003cp\u003eA uniaxial tensile test was carried out to evaluate the mechanical characteristics of the used steel bars before and after being exposed to elevated heat [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. The yield stress, ultimate strength and failure strain at room temperature were found to be 515 MPa, 629 MPa and 16.3% for main (bottom and top) steel bars and at 537 MPa and 622 MPa and 10.7% for the stirrups\u0026rsquo; bars. These mechanical properties were slightly affected by the exposure to 450\u003csup\u003eo\u003c/sup\u003eC.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003e4.3 Carbon Fiber-reinforced Polymer\u003c/h2\u003e \u003cp\u003eCarbon fiber-reinforced polymer ropes were used in this work. The ropes carry the commercial name \"Sika Wrap FX-50C\" as provided by SIKA Company. They are solid in rolls of 25-m rope length. Their tensile strength, elastic modulus, and strain at failure were reported by the manufacture at 2 kN/mm\u003csup\u003e2\u003c/sup\u003e, 230 kN/mm\u003csup\u003e2\u003c/sup\u003e and 1.6%, respectively. The ropes were saturated with Sikadur-52 resin before being bonded in grooves to concrete using Sikadur-330 epoxy. The manufacturing tensile and adhesion strengths for the first resin are 27 and 10 N/mm\u003csup\u003e2\u003c/sup\u003e as compared to 30 and 4 N/mm\u003csup\u003e2\u003c/sup\u003e for the second epoxy, respectively. The elastic modulus for the latter epoxy is reported at 4.5 kN/mm\u003csup\u003e2\u003c/sup\u003e.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003e4.4 Concrete Preparation\u003c/h2\u003e \u003cp\u003e \u003cdiv class=\"BlockQuote\"\u003e \u003cp\u003eA ready-mix concrete (RMC) with a strength grade of 35 MPa was ordered from the supplier. Wooden formwork with interior dimensions of (150\u0026times; 250\u0026times; 1600) mm was used to cast the beam specimens. Concrete was placed in the molds in three layers; each compacted by a poker-type vibrator. Finally, a trowel was used to level the final surface. After 24 hours, the beams were de-molded and then wrapped in wet burlap for a further 27 days for curing. Concrete cylinders (100 mm in diameter by 200 mm) were cast and cured at the same conditions to evaluate the compressive properties of intact and heat-damaged concrete.\u003c/p\u003e \u003c/div\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec9\" class=\"Section2\"\u003e \u003ch2\u003e4.5 Heat Treatment\u003c/h2\u003e \u003cp\u003eThe beam specimens, designated for heat treatment, were subjected to 450\u0026deg;C for three hours using a large electric furnace following the heating protocol shown in Fig.\u0026nbsp;3. Upon completion of heat treatment, the furnace cover was left partially open, so that the specimens cool at a rate of 0.40\u003csup\u003eo\u003c/sup\u003eC/min.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec10\" class=\"Section2\"\u003e \u003ch2\u003e4.6 Installation of NSM-CFRP Ropes\u003c/h2\u003e \u003cp\u003eTo apply the current strengthening/repair method, parabolic and straight man-made grooves were marked on either side of the specimens. An electrical saw was used to create these grooves at a width of 17 mm and a depth of 17 mm along the beams\u0026rsquo; sides with their fan-shaped anchorage created on both end faces. All grooves were cleaned by a vacuum machine before dried using a volatile chemical compound. At the time of installation, the saturating resin (Sikadur\u0026reg;-52) was prepared by blending both of its ingredients using an electric mixer before the CFRP ropes, already cut to the desired lengths, were fully saturated in Sikadur\u0026reg;-52 with excess adhesive removed. After that, another resin (Sikadur\u0026reg;-330) designated for bonding the SNSM-CFRP ropes, was prepared by mixing its two ingredients using an electric mixer. Then, the clean and dry grooves were filled to mid-height with the prepared resin before the ropes (saturated with Sikadur\u0026reg;-52) were precisely placed into the grooves and extended to the anchorage zone at both end surfaces to create a fan-shaped pattern. Finally, another layer of epoxy was applied on the surface of the ropes to fill the grooves at the beams\u0026rsquo; sides and over the anchorage ends with extra epoxy scraped off and the surface leveled. The specimens were left to cure for seven days at 23\u0026deg;C according to the manufacturer's instructions. Figure\u0026nbsp;4 illustrates the end view of the strengthened/repaired beams after the installation of NSM CFRP ropes and their anchorage.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec11\" class=\"Section2\"\u003e \u003ch2\u003e4.7 Test Setup\u003c/h2\u003e \u003cp\u003eRC beams, belonging to groups I, II, and III, were tested under four-point symmetric, six-point symmetric, and six-point asymmetric loadings, respectively. The loading-cell measurement \u003cem\u003eversus\u003c/em\u003e deflection was recorded using a data-recording device with a 2000-kN capacity. Three linear variable displacement transducers (LVDTs) were employed; two were fixed to the two parallel CFRP ropes at the main steel level to measure their elongation, whereas one was positioned at the mid-span of the bottom surface of the beam to measure the vertical deflection. Visual monitoring of crack initiation and propagation leading to failure was performed during testing. The test setup for the two configurations of CFRP under the various loading distributions is schematically presented in Fig.\u0026nbsp;5.\u003c/p\u003e \u003c/div\u003e"},{"header":"5. Results and Discussion","content":"\u003ch3\u003e5.1 Evaluation of Heat Damage\u003c/h3\u003e\n\u003cp\u003eRC beams, designated for heat treatment, were subjected to an elevated temperature of 450\u0026deg;C for three hours. At this level of heating, damage introduced in concrete was mainly caused by the expulsion of capillary and gel water from the concrete\u0026rsquo;s pore system, generating a high vapor pressure that caused significant distributed cracking on the concrete surface. As seen in Figure 6, the specimens with additional reinforcement exhibited more prominent cracks in terms of intensity. It should be noted that most of the cracks became infeasible after cooling; therefore, the marking presented was made while the beams were still warm. The properties of concrete are also altered negatively by the exposure to this heating regimen, as will be explained later.\u003c/p\u003e\n\u003ch3\u003e5.2 Cracking and Failure Mode\u0026nbsp;under Loading\u003c/h3\u003e\n\u003cp\u003eCrack development and patterning were observed and noted and failure modes were determined while the transverse load was applied at a rate of 0.3kN per second. Cracks\u0026rsquo; initiation and development until the failure of control and heat-damaged beams at 450\u003csup\u003eo\u003c/sup\u003eC under different loading protocols are described herein.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.2.1 Control and Heat-damaged B\u003c/strong\u003e\u003cstrong\u003eeams\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUnder symmetrical loading, control (C4PL/C6PL) and heat-damaged RC beams (HD\u003csub\u003e450\u003c/sub\u003e-4PL/HD\u003csub\u003e450\u003c/sub\u003e-6PL) demonstrated a flexural mode of failure, as shown in the photos of Figure 7 (a-f). For control specimens, flexural cracks first emerged at loads of 29 and 45 kN around the middle of the span of the beams for loading conditions of 4PL and 6PL, respectively. As the load was increased, cracks started developing in the high-shear zones before both flexural and shear cracks spread more quickly upward into the compression zone with further loading, reflecting the quick shift in the neutral axis caused by the yielding of reinforcing steel. This process continued until the crushing of compression concrete at failure points of 112 kN and 191 kN, respectively. On the other hand, beams, pre-damaged at an elevated temperature of 450\u003csup\u003eo\u003c/sup\u003eC, then tested under symmetrical-loading conditions (4PL/6PL), experienced their first flexural cracks around the mid-span at loads of 28kN and 40 kN, respectively. Afterward, more cracks appeared in the high-moment and shear regions that developed towards the compression zone with increasing load, resulting in a common flexural failure at load values of 97kN and 173 kN, respectively. Comparison between the impact of the two symmetrical loading regimes in terms of cracks development and failure modes in tested beams demonstrated that load-generated cracks tended to be more concentrated in the middle region of the span for the beams subjected to 4-point loading (4PL), yet tended to be more distributed along the span of those beams loaded with 6PL, allowing these beams to experience more deflection.\u003c/p\u003e\n\u003cp\u003eUnder A6PL asymmetrical loading distributions, a similar failure mechanism was recognized for control and heat-damaged (at 450\u0026deg;C) beams (C-ASY/HD450-ASY), as shown in the photos of Figure 7 (c, f). Flexural cracks first emerged with loads of 40 kn and 16 kN for each of the control and heat-damaged specimens, respectively. These initiated below the point at which a higher load was applied on the right portion of the beam. As loads increased, more flexural cracks appeared between the 4 points of loading along the beam span but remained more concentrated under the higher load. Here, the cracks showed higher width and extension rate (upward) into the compression zone. With further load increase, the neutral axis shifted quickly upwards due to the yielding of reinforcing steel. This process continued until the crushing of compression concrete at a final load of 174 kN and 150 kN for control and heat-damaged specimens, respectively. This took place below the point at which the higher portion of the total load was applied, respectively. Heat-damaged specimen (HD450-ASY) experienced concrete-cover separation in the segment of the beam where the higher portion of the load was applied due to the increased vertical shear, hence resulting in horizontal shearing stresses. It is clear that under asymmetrical-loading distribution, the control and heat-damaged beams underwent more deflection and higher cracking intensity (within the failure zone) compared to beams subjected to symmetrical loading.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.2.2 Strengthened Undamaged Beam\u003c/strong\u003e\u003cstrong\u003es\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe cracking patterns for different strengthened beams are depicted in the photos of Figure 8 (a\u0026ndash;f). Flexural cracks emerged at loads of 34, 36, 49, and 50 kN around the middle span of beams C-SSP-4PL, C-SPP-4PL, C-SSP-6PL, and C-SPP-6PL, respectively. As the load increased, cracks appeared in the high-shear zones before flexural failure and shear cracks propagated at a higher rate upwards into the compression zone. This process continued until ultimate loads of 177, 197, 299, and 305 kN were attained, respectively. The rupture of the CFRP ropes occurred suddenly; resulting in high reactive forces that caused concrete-cover separation at the center of these beams. Simultaneously, the moment of inertia of the beams\u0026rsquo; section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating a flexural ductile failure. The impact of distributing the load at four instead of two points around the middle upon cracking extent and failure mode can be understood by comparing photos of Figure 8 (a-d). Regardless of the strengthening configuration, the cracking spreading along the span was more obvious in the beams loaded under 4 points. This is attributed to the extension of some of the flexural cracks, developed near the end supports, at an inclination toward the compression zone.\u003c/p\u003e\n\u003cp\u003eThe mechanism of failure under asymmetrical loading was similar for both strengthened beams (C-SSP-ASY/C-SPP-ASY), as shown in the photos of Figure 8 (e, f). Flexural cracks emerged at loads of 57 kN and 50 kN for the beams with straight and parabolic profiles, respectively. Specifically, the cracks initiated below the higher portion of the load on the right side of the beam, then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 loading points along the beam span and remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. This process continued until ultimate loads of 300 kN and 289 kN were reached, respectively. The rupture of the CFRP ropes occurred suddenly at this time, resulting in strong reactive forces that caused concrete-cover separation in the right portion of the beam below the main load application point. Simultaneously, the moment of inertia of the beams\u0026rsquo; section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure.\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003e5.2.3 Heat-damaged at 450\u0026deg;C and Repaired\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Beams\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eThe cracking patterns of different repaired beams are depicted in the photos of Figure 9 (a\u0026ndash;f). Flexural cracks emerged at loads of 33, 29, 52, and 47 kN around the middle span for beams HD450-RSP-4PL, HD450-RPP-4PL, HD450-RSP-6PL and HD450-RPP-6PL, respectively. As the load was increased, cracks appeared in high-shear zones before flexural failure and shear cracks propagated at a higher rate upwards into the compression zone. This process continued until ultimate loads of 160, 161, 282, and 292 kN were attained, respectively. The rupture of the CFRP ropes occurred suddenly, resulting in high reactive forces that caused concrete-cover separation at the center of these\u0026nbsp;beams. Simultaneously, the moment of inertia of the beams\u0026rsquo; section was reduced to shift the neutral axes quickly into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure.\u0026nbsp;The impact of distributing the load at four instead of two points around the middle upon cracking extent and failure mode can be understood by comparing the photos of Figure 9 (a-d). Regardless of the repair scheme, the cracking spreading along the span was more obvious in the beams subjected to loading at a higher number of points. It is also clear that the developed shear cracks extended more toward the supports for these beams to generate an increased number of cracks between the supports.\u003c/p\u003e\n\u003cp\u003eThe mechanism of failure under asymmetrical-loading distributions is shown in the photos of Figure 9 (e, f) for the beams HD450-RSP-ASY and HD450-RPP-ASY. For the HD450-RPP-ASY specimen, flexural cracks emerged at loads of 36 kN below the higher portion of the load on the right side of the beam and then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 points of loading along the beam span, but they remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. This process continued until an ultimate load of 247 kN was reached. The rupture of the CFRP rope occurred suddenly at this time, resulting in strong reactive forces that caused concrete-cover separation in the right portion of the beam below the load-application point of higher proportion. Simultaneously, the moment of inertia of the beams\u0026rsquo; section was reduced to shift the neutral axes quicker into the compression zone, leading to compression concrete crushing while the primary steel reinforcement was yielding or undergoing strain hardening, indicating flexural ductile failure. Specimen HD450-RSP-ASY showed a different mode of failure, where flexural cracks emerged at a load of 40 kN below the higher portion of the load on the right side of the beam and then appeared in the high-shear zones as the load was increased. With higher load, more cracks appeared between the 4 points of loading along the beam span, but they remained concentrated under the region where the higher portion load acted, showing higher crack width and spreading upwards into the compression zone. The end concrete cover eventually delaminated at a failure load of 270 kN, following the formation, then a horizontal crack propagated toward the middle span from the right side of the beam where higher load portions acted.\u003c/p\u003e\n\u003ch3\u003e5.3 Mechanical Response\u003c/h3\u003e\n\u003cp\u003eThe mechanical performance of RC beams is assessed under different loading protocols (4PL/6PL/A6PL). The load-deflection response is evaluated along with its characteristics; namely, ultimate load capacity, yielding load, first-crack load, stiffness, toughness, and displacement ductility. The slope of the linear segment and the area underneath the load-deflection curve reflect stiffness and toughness, respectively, whereas the deflection ratio at the failure point to that at steel yielding reflects displacement ductility. All mechanical characteristics were summarized in Table 2 for all beams (control, heat-damaged, strengthened, and repaired beams) for the three loading protocols considered in this study.\u003c/p\u003e\n\u003ch4\u003e\u003cstrong\u003e5.3.1 Control and Heat-damaged Beams\u003c/strong\u003e\u003c/h4\u003e\n\u003ch4\u003eThe load-deflection curves of the control and heat-damaged beams showed similar patterns under the three types of loading. These curves initially followed an approximately linear pattern up to reinforcing-steel yielding before departing from linearity. The load-deflection characteristics of Table 2 indicate that the intact RC beams demonstrated different loading capacities under the three loading protocols: flexural load capacity reached 191, 174 and 112 kN for beams C-6PL, C-ASY, and C-4PL, respectively. These correspond to moment capacities of 33.4, 34.5, and 30.8 kN.m, respectively. The stiffness of the control beam\u0026nbsp;specimens reached 25, 23, and 14 GPa for beams C-6PL, C-ASY, and C-4PL, respectively.\u0026nbsp;More evenly distributed stresses were present in specimens subjected to six points of loading, whether in symmetrical or asymmetrical distribution. Accordingly, normal compressive and tensile stresses were distributed along the span to reduce stress on top and bottom concrete. Consequently, premature beam cracking and failure were prevented to enhance stiffness and moment capacity.\u0026nbsp;In contrast, ductility and toughness were the highest for beam C-6PL, yet the lowest for beam, as reported in Table 2. The uniformly distributed loads under 6PL allowed a better distribution of induced stress to allow more deflection of the beams before failure. The results of Table 2 showed a drop in flexural load capacity for beams HD450-6PL, HD450-4PL, and HD450-ASY by 10%, 14%, and 14% in comparison to relevant intact ones, respectively. Surprisingly, the stiffness of the present beam was unaffected by heating to 450\u0026deg;C for three hours, although the load capacity was tangibly decreased. Apparently, the elastic modulus of the reinforcing steel, not affected by heating, dictated the stiffness of the concrete section. Upon heating, the rotational ductility was decreased by 1%, 4%, and 16% and the toughness decreased by 3%, 17%, and 29% of their original values. The A6PL\u0026nbsp;loading distribution resulted in higher stresses under the application point where the higher proportion of the load acted and tended to reduce the original ductility and toughness for the relevant beam, noticeably. It is also clear that distributing loading in a symmetric manner is more beneficial in maintaining the latter two properties upon heating.\u003c/h4\u003e\n\u003ch4\u003e\u003cstrong\u003e5.3.2 Strengthened Undamaged Beams\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eFigure 10 shows the load \u003cem\u003eversus\u003c/em\u003e displacement curves for strengthened beams under 4PL, 6PL, and A6PL, as compared to those of the intact beams, respectively. These curves followed an approximately linear pattern initially up to a certain point before departing from linearity. The major characteristics of these curves were obtained and listed in Table 2. The strengthening techniques adopted resulted in a significant increase in the flexural load capacity for the beams C-SSP-4PL, C-SPP-4PL, C-SSP-6PL, C-SPP-6PL, C-SSP-ASY, and C-SPP-ASY by 58, 76, 57, 60, 73 and 66% compared to the original values, respectively. In contrast, the relevant residuals for stiffness and toughness were increased by (14, 27, 13, 20, 33, and 35%) and (1, 43, 42, 45, 90 and 64%), respectively. As expected, the relevant ductility was decreased to (67, 86, 83, 94, 97 and 95%) of the original values, respectively. These findings showed that under the static symmetrical loading distributions, the parabolic profile with NSM CFRP ropes achieved higher enhancements in load capacity, stiffness, toughness, and ductility than those of the straight profile, owing to the higher embedment length of the curved NSM CFRP ropes coupled with a lower tendency of the beams towards concrete-cover separation. This is referred to the deviation of the parabolic profile from the critical separation zone near both end supports. Under asymmetric loading, the straight profile imparted higher improvements to load capacity and toughness than those of the parabolic profile because of the lower contribution of the ropes of the latter profile under the critical-loading point to flexural resistance. The results depicted in Figure 10\u0026nbsp;reflect the negative impact of using a parabolic profile of NSM CFRP ropes on load capacity and stiffness in cases involving higher distribution of acting loads.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThe comparison between the present beams under asymmetric A6PL and symmetrical 6PL is in favor of the first in terms of all the considered mechanical characteristics, regardless of the rope profile considered. This can be easily explained from a statics point of view. Exposing a simply supported beam to a larger portion of its load at locations closer to the support points would generate a lower moment, which helps delay concrete failure. As a result, the load at failure and the corresponding ductility would be higher compared to those under symmetric loading. It is also logical to anticipate that the contribution of the straight NSM CFRP ropes to mechanical characteristics is higher under asymmetric loading, which is due to the higher resisting moment arm of the NSM CFRP rope along the entire beam span. This allowed more resistance to flexural stresses, which helped delay crack propagation to yield higher deflection at the failure point.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.3.3 Heat-damaged at 450\u0026deg;C and Repaired\u003c/strong\u003e\u003cstrong\u003e\u0026nbsp;Beams\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eFigure 11\u0026nbsp;shows the load \u003cem\u003eversus\u003c/em\u003e displacement curves for heat-damaged and repaired beams as compared to those of the control beams under the different loading protocols (4PL, 6PL, and A6PL). These curves followed an approximately linear behavior up to a certain point before bending over until the failure point. The major characteristics of these curves were obtained and listed in Table 2. The repair techniques adopted resulted in a significant increase in the flexural load capacity for the beams (HD450-RSP-4PL, HD450-RPP-4PL, HD450-RSP-6PL, HD450-RPP-6PL, HD450-RSP-ASY, and HD450-RPP-ASY) by (43, 43, 48, 53, 55 and 42%) compared to their original value, respectively. In contrast, the relevant residual stiffness was increased by (32, 25, 17, 34, 34 and 37%). Except for the beam (HD450-RSP-4PL), other beams achieved an increase in relevant toughness (4% to 54%), depending on the loading and repair profile adopted. Beams subjected to symmetric loading lost partially their displacement ductility in the range of (7% to 22%), whereas those subjected to asymmetric loading showed an increase of (31% and 16%) for straight and parabolic profiles, respectively.\u003c/p\u003e\n\u003cp\u003eThe results of Table 2\u0026nbsp;reflect the negative impact of localizing loading on the heat-cracked concrete beams. As a result, beams subjected to loading at four instead of two points along their spans attained the same load capacity and stiffness, yet higher toughness and ductility (deflection). It was also revealed that under asymmetric loading, the beams were able to withstand higher loads and deflected more to achieve the highest residuals in the four characteristics studied. It is also evident that the use of straight instead of parabolic profile of NSM CFRP ropes in repair is advantageous for asymmetric loading, but has an unclear impact on the cases with symmetric loading.\u003c/p\u003e\n\u003ch3\u003e5.4 Efficiency of Strengthening/Repairing Techniques\u003c/h3\u003e\n\u003ch4\u003e\u003cstrong\u003e5.4.1 Performance Factor\u003c/strong\u003e\u003c/h4\u003e\n\u003cp\u003eThe overall performance factor (PF), as determined using Equation (1), was used to examine the impact of the loading protocol in conjunction with the strengthening profile [44]. According to the definition of PF in Equation (1), the ratio between the ultimate strength and ultimate deflection to their values at service stress (corresponding to strain in concrete at 0.001) provides a clear picture of the ability of the strengthening/repair technique to achieve the required serviceability and safety. The PF values were calculated using Equation (1) before being listed in Table 3.\u003c/p\u003e\n\u003cp\u003e\u003cimg 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\"\u003e\u003cbr\u003e\u003c/p\u003e\n\u003cp\u003eThe results of Table 3 demonstrate that the strengthening/repair procedures employed were effective as the PF values varied from 5.44 to 7.87 for strengthened specimens compared to values from 10.88 to 16.3 for repaired specimens. The drastic increase in PF for the concrete heat-damaged beams before being repaired is attributed to the enhancement in their deformability. The PF gives a clearer picture regarding the impact load distribution than that drawn based on mechanical characteristics. It is clear that load distribution had a positive impact on both strengthened and repaired beams\u0026rsquo; performance; especially when the straight profile of NSM CFRP ropes was used. This could be attributed to the increased deformability of the beams as the load stresses are distributed more uniformly along the beam span. The results show also that applying asymmetrically distributed loading yielded the highest PF, especially when a straight profile of the NSM CFRP ropes was implemented. The results of Table 3 revealed that the contribution of the parabolic profile of the NSM CFRP ropes seemed to be undermined in repaired beams as compared to that in strengthened beams when subjected to symmetric loading. In contrast, the use of a straight profile of NSM CFRP ropes is advised for beams strengthened or repaired to resist asymmetric loading.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003e5.4.2 Strain Induced in CFRP Ropes\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe strain in CFRP ropes was measured experimentally using two LVDTs, which were mounted to the ropes on either side of the beams. For part of the beams, the readings were not correctly collected. Therefore, the principle of strain compatibility and equilibrium was used to determine the theoretical strain in the ropes based on the achieved load capacity with results listed in Table 4. The residual strains computed with respect to the ultimate strain capacity, provided by the CFRP rope manufacturer, declined for heat-treatment and repaired beams in comparison with those strengthened with similar repair configurations and test conditions. The residual strain in the CFRP ropes at the failure point ranged from 82% to 100% for strengthened beams but was reduced to lower limits for heat-damaged beams at roughly 52% to 95%. Only for the repair case where concrete-cover delamination occurred under loading, the residual strain degrades below 70%.\u003c/p\u003e"},{"header":"6. Conclusions","content":"\u003cp\u003eBased on the experimental work previously described, the following conclusions can be drawn:\u003c/p\u003e\n\u003col\u003e\n \u003cli\u003eExposing concrete beams to 450\u003csup\u003eo\u003c/sup\u003eC for three hours resulted in significant distributed cracking on a concrete surface that degraded the load capacity by as high as 14% and the toughness by as much as 29%, regardless of the loading protocol applied.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eStrengthening with NSM CFRP ropes boosted the flexural load capacity, stiffness, and toughness under different loading protocols by (57-76)%, (13-35)%, and (1-90)%, yet resulted in degrading the displacement ductility to (67-97) % of their original values, respectively.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eUnder static symmetrical loading distributions, the concrete beams strengthened with a parabolic profile of NSM CFRP ropes achieved higher enhancements in load capacity, stiffness, toughness, and ductility than those with a straight profile. In contrast, beams, strengthened with straight NSM CFRP ropes seemed to behave better under asymmetrical loading than those with parabolic profile due to their higher resisting moment arm along the entire span. \u0026nbsp;\u003c/li\u003e\n \u003cli\u003eRepairing the beam post-heated at 450\u003csup\u003eo\u003c/sup\u003eC using both straight and parabolic profiles of SNSM-CFRP ropes resulted in a significant increase in the flexural load capacity and stiffness in the ranges of (42-55%) and (17-37%) compared to their original values, respectively.\u0026nbsp;\u003c/li\u003e\n \u003cli\u003eHeat-damaged and repaired concrete beams subjected to symmetric loading lost partially their displacement ductility in the range of 7% to 22%, whereas beams, subjected to asymmetric loading showed an increase of 31% and 16% for straight and parabolic profiles, respectively.\u003c/li\u003e\n \u003cli\u003eIntact and heat-damaged (at 450\u003csup\u003eo\u003c/sup\u003eC) beams, strengthened/repaired using SNSM CFRP ropes, experienced flexural failure followed by bottom concrete-cover separation caused by the reactive forces generated from the rapture of CFRP rope at the point failure, except for that heat-damaged and repaired with straight rope profile and subjected to asymmetric loading.\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgement\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors acknowledge the financial support by the deanship of research at Jordan University of Science and Technology (Irbid-Jordan) under project number 498/2022.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConflict of interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors testify that they have no conflict of interest in publishing this article at Materials and Structures.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eAnupama Krishna D, Priyadarsini RS, Narayanan S. 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Available from: https://doi.org/10.1016/j.istruc.2021.04.079\u003c/li\u003e\n \u003cli\u003eHaddad RH, Harb AN. CFRP ropes for retrofitting heat-damaged concrete beams. J Build Eng. 2021;43:102522. Available from: https://doi.org/10.1016/j.jobe.2021.102522\u003c/li\u003e\n \u003cli\u003eASTM C. Standard test method for density, relative density (specific gravity) and absorption of fine aggregate. 2012.\u003c/li\u003e\n \u003cli\u003eASTM A. Standard Test Method for Relative Density (Specific Gravity) and Absorption of Coarse Aggregate. ASTM West Conshohocken, PA; 2015.\u003c/li\u003e\n \u003cli\u003eASTM Committee C09. Standard Test Method for Compressive Strength of Cylindrical Concrete Specimens. ASTM Standards. ASTM C39/C39M-10. West Conshohocken, USA: ASTM International; 2010.\u003c/li\u003e\n \u003cli\u003eCEN Technical Committee 250. Part 1-2: General Rules - Structural Fire Design. Eurocode 4: Design of Composite Steel and Concrete Structures. EN 1994-1-2:2005. European Commission; 2005.\u003c/li\u003e\n \u003cli\u003eACI. Building Code Requirements for Concrete and Commentary. ACI 318M-19. 2019;628.\u003c/li\u003e\n \u003cli\u003eASTM Committee A01. Standard Specification for Deformed and Plain Carbon-Steel Bars for Concrete Reinforcement. ASTM Standards. ASTM A615/A615M-15a. West Conshohocken, USA: ASTM International; 2015.\u003c/li\u003e\n \u003cli\u003eSpadea G, Bencardino F, Swamy RN. Optimizing the performance characteristics of beams strengthened with bonded CFRP laminates. Mater Struct Constr. 2000;33(2):119\u0026ndash;26.\u003c/li\u003e\n \u003cli\u003eHognestad E. Fundamental concepts in ultimate load design of reinforced concrete members. J Proceedings. 1952. p. 809\u0026ndash;30.\u003cspan dir=\"RTL\"\u003e\u003c/span\u003e\u003c/li\u003e\n\u003c/ol\u003e"},{"header":"Tables","content":"\u003cp\u003eTables 1 to 4 are available in the Supplementary Files section\u003c/p\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":true,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"materials-and-structures","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"maas","sideBox":"Learn more about [Materials and Structures](http://link.springer.com/journal/11527)","snPcode":"11527","submissionUrl":"https://www.editorialmanager.com/maas/default2.aspx","title":"Materials and Structures","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false},"keywords":"Concrete, Beams, Flexure strengthening, CFPR ropes, SNSM, Loading","lastPublishedDoi":"10.21203/rs.3.rs-4434850/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-4434850/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe influence of static-load distribution and symmetry on the flexural performance of concrete beams, strengthened/repaired using side near-surface-mounted (SNSM) CFRP ropes with parabolic and straight profiles is investigated. For this, eighteen reinforced concrete beams (150 \u0026times; 250 \u0026times; 1600 mm) were fabricated using a ready-mix concrete of 35 MPa strength grade before cured for 28 days in wet burlap for 28 days. Nine beams were exposed to an elevated temperature at 450\u003csup\u003eo\u003c/sup\u003eC for three hours, while the remaining ones were left in laboratory air, as controls. Six specimens from each group were retrofitted using SNSM of straight and parabolic profiles then tested with references ones under four- and six-point symmetrical and six-point asymmetrical loadings with load response versus deflection and strain in SNSM ropes acquired. Furthermore, cracking initiation and propagation leading to failure was monitored and reported. Generally, the study revealed that the mechanical performance of the concrete beams was influenced by the loading regime as well as by the rope profile (straight, parabolic) as well as heat-damage. The flexural performance factor (PF) varied from 5.4 to 7.9 for strengthened compared to 10.9 to 16.3 for repaired and heat-damaged specimens. Furthermore, all strengthened/repaired beams failed by concrete-cover separation following the sudden rupture of the SNSM CFRP ropes except for that repaired with a straight profile of SNSM CFRP rope and subjected to asymmetrical loading.\u003c/p\u003e","manuscriptTitle":"Impact of Loading Protocol on the Repair Efficiency of Heat-damaged Concrete Beams with SNSM CFRP Ropes","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-06-14 11:39:56","doi":"10.21203/rs.3.rs-4434850/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"reviewerAgreed","content":"","date":"2024-06-26T04:04:18+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2024-06-02T14:25:20+00:00","index":"","fulltext":""},{"type":"editorInvited","content":"Materials and Structures","date":"2024-05-26T09:53:01+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2024-05-20T17:25:17+00:00","index":"","fulltext":""},{"type":"submitted","content":"Materials and Structures","date":"2024-05-17T16:33:09+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"materials-and-structures","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"maas","sideBox":"Learn more about [Materials and Structures](http://link.springer.com/journal/11527)","snPcode":"11527","submissionUrl":"https://www.editorialmanager.com/maas/default2.aspx","title":"Materials and Structures","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"Springer Hybrid","inReviewEnabled":true,"inReviewRevisionsEnabled":false}}],"origin":"","ownerIdentity":"6a468c20-0453-4e6c-85fc-d75ad3294da8","owner":[],"postedDate":"June 14th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2025-01-13T15:58:37+00:00","versionOfRecord":{"articleIdentity":"rs-4434850","link":"https://doi.org/10.1617/s11527-025-02569-1","journal":{"identity":"materials-and-structures","isVorOnly":false,"title":"Materials and Structures"},"publishedOn":"2025-01-09 15:56:54","publishedOnDateReadable":"January 9th, 2025"},"versionCreatedAt":"2024-06-14 11:39:56","video":"","vorDoi":"10.1617/s11527-025-02569-1","vorDoiUrl":"https://doi.org/10.1617/s11527-025-02569-1","workflowStages":[]},"version":"v1","identity":"rs-4434850","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-4434850","identity":"rs-4434850","version":["v1"]},"buildId":"qtupq5eGEP_6zYnWcrvyt","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}