Strengthened Reinforced Concrete Beams Research Articles

An Experimental Study Incorporating Carbon Fiber Composite Bars and Wraps for Concrete Performance and Failure Insight

Corrosion of conventional steel reinforcement is responsible for numerous structurally deficient bridges, which is a multi-billion-dollar challenge that creates a vicious cycle of maintenance, repair, and replacement of infrastructure. Repair of existing structures with fiber-reinforced polymer (FRP) has become widespread due to multiple advantages. Carbon FRP’s superior tensile strength and stiffness make it particularly effective in shear and flexural strengthening of reinforced concrete (RC) beams. This experimental study incorporates carbon fiber polymer composite bars and wraps to study and report on the flexural behavior of RC beams. By employing a combination of CFRP bar and wrap for strengthening RC beams, this study observed an approximate 95% improvement in flexural load capacity relative to control RC beams without strengthening. This substantial enhancement highlights the effectiveness of integrating CFRP in structural applications. Nevertheless, the key observation is the failure mode due to this combination providing significant insights into the changes facilitated by this combination approach.

Mechanical Properties of Fire-Damaged RC Beams Reinforced with Carbon Fiber Mesh

The bearing capacity of reinforced concrete (RC) beam will be weakened by fire. It is necessary to strengthen RC beams after fire. The carbon fiber mesh (CFM) can be used to reinforce RC beams. In this paper, RC beams were exposed to varying temperatures, followed by reinforcement with varying layers of CFM. The influence of the heating temperature and the number of CFM layers on the flexural performance of RC beams was investigated. The results indicated that the cracking loads of RC beams were 18.2, 16.4, 16.3, and 15.5 kN when the RC beams were subjected to room temperatures, 150, 350, and 550 °C. Compared to the unreinforced beams at room temperature, the cracking loads of the RC beams were reduced by 9.89%, 10.44%, and 14.84%. As the quantity of CFM reinforcement layers rises, so does the ultimate bearing capacity. For example, when the temperature was 150 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 31.76% compared to the reference beam. When the temperature was 350 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 19.51% and 28.04% compared to the RC beam without CFM. When the temperature was 550 °C, the ultimate loads of the beams with one and three layers of CFM were increased by 20% and 26.67% compared to the RC beam without CFM. Fire-damaged RC beams can be strengthened by one layer of CFM and mortar if the temperature was below 350 °C. Fire-damaged RC beams can be strengthened by three layers of CFM and mortar if the temperature was below 550 °C. The mechanical properties can be obviously enhanced.

The flexural behavior and efficiency of RC beams strengthened with SNSM bars under the effect of several end conditions and material properties

In this paper, twelve strengthened, and one un-strengthened reinforced concrete (RC) beams were experimentally and numerically investigated in flexure. The strengthened RC beams were upgraded with steel or glass fiber reinforced polymer (GFRP) in the form of side-near surface mounted (SNSM) reinforcement. The tested parameters were the SNSM bar diameter, adhesive materials, SNSM end conditions, and materials of strengthening bars. The three-dimensional elastic-plastic finite element program (ABAQUS) was utilized to simulate numerically the tested beams in the experimental program. Finally, a parametric study was numerically conducted to show the effect of different parameters of the SNSM technique on the flexural response of the strengthened beams. The experimental findings demonstrated that the RC beams strengthened with SNSM steel bars generally had higher load capacity than those strengthened with GFRP. Bent ends of the SNSM steel bars were more efficient than in SNSM GFRP bars or end anchorage by GFRP sheets. The load-carrying capacity enhancement for strengthened beams with SNSM steel bars (10 and 12 mm in diameter) having end anchorage (wrapped by CFRP sheets) was 212.6% and 234.7% compared to the unstrengthened beam. In contrast, the enhancement decreased from 184.5 to 145% and 160.5 to 158.3% as the bond material changed from epoxy to grout for the beams strengthened by 10 mm and 12 mm diameters of SNSM steel bars, respectively. The numerical and experimental findings were in close agreement.

Entire mechanical analysis of prestressed CFRP strengthened RC beams under different prestressed introduced methods

In order to clarify the effect of mechanical tensioning and SMA wire heating recovery on introducing prestress into CFRP sheet strengthened reinforced concrete (RC) beams, an experimental research on the bending performance of prestressed CFRP sheet strengthened RC beams was conducted. Based on the test results, a bending carrying capacity model for RC beams externally strengthened with prestressed CFRP sheets was proposed. The model provides calculation methods for the decompression moment, cracking moment, yielding moment, and ultimate moment, corresponding to different failure modes of the RC beams strengthened with externally bonded prestressed CFRP sheets. Four experimental beams were designed to verify the accuracy of the model with the prestresses of 100 MPa and 200 MPa. The results show that during the yield stage and strengthening stage, the loading-unloading stress-strain relationship curves of SMA wire under different prestrains are basically consistent. When the prestrain of SMA wire is 10%, the maximum recovery stress reaches 448.5 MPa. Under the same prestrain conditions, the maximum recovery stress of CFRP sheets was reduced by 37.8–39.5% when the prestress was introduced through heating recovery of SMA wires. The failure mode of mechanically tensioned prestressed CFRP sheet strengthened beams is the CFRP sheet debonding caused by mid-span bending cracks, while the failure mode of strengthened beams with prestressed CFRP sheet by SMA wire heating recovery is the CFRP sheet end debonding. The cracking moment and yield moment of the strengthened beams are significantly increased by two methods of introducing prestressing. The stiffness improvement of mechanically tensioned prestressed CFRP sheet strengthened beam is relatively large. While, the prestressed CFRP sheet strengthened beam by SMA wire heating recovery gradually experience end peeling failure of the CFRP sheet, and the prestressing effect does not effectively limit the development of cracks, resulting in limited stiffness improvement. The calculation results are in good agreement with the experimental results, proving that the proposed method for analyzing the entire bending process can be used to predict the bending mechanical properties of the prestressed CFRP sheet strengthened beams.

Analytical study on flexural strengthening of narrow RC beams with hybrid anchored CFRP sheets

Premature debonding of fiber-reinforced polymer (FRP) sheets commonly occurs in purely bonded reinforced concrete (RC) beams. A hybrid strengthening method for narrow FRP-strengthened RC beams has been proposed to solve this problem. Experimental results have verified the effectiveness of the novel strengthening system in preventing the end debonding and impeding the intermediate debonding of the FRP sheet. However, the mechanism of its strengthening efficiency has not been studied deeply enough. Therefore, this paper developed a non-linear three-dimensional finite element (FE) model to study the flexural behavior of the FRP-strengthened narrow RC beams hybrid anchored with end self-locking system. The FE model was verified against the available experimental studies and showed good agreement, with a R2 of 0.97. Based on the verified model, parametric studies were performed to study further the influences of four major factors: FRP sheet length, steel rebar ratio, concrete compressive strength, and number of FRP sheet layers. The efficacy of hybrid strengthened beams was reduced with longer FRP bond lengths and higher steel rebar ratios. Conversely, increasing concrete compressive strength and FRP sheet layers to a certain degree enhanced the efficacy. Finally, an analytical model to predict the load-deflection curve of the beam was proposed.

Flexural strengthening of RC beams by advanced concrete canvas

AbstractIn this study, concrete canvas (CC) layers were used as a novel method to strengthen reinforced concrete (RC) beams because of their flexibility, rapid installation, fast curing, and rapid strengthening. Due to the importance of the CC mechanical properties, various combinations of cement including ordinary (OPC) and High Alumina (HAC), as well as silica fume, were investigated to determine the optimal mixture for strengthening RC beams. The results indicate that substituting 75% of HAC with OPC significantly boosted flexural strength by 33%, and increased tensile strength in the warp and weft directions by 25% and 21%, respectively. The study examined six RC beam specimens in a four‐point flexural test, assessing their flexural properties, ductility, cracking behavior, and energy dissipation. The number of CC layers and the bonding method, which involved either the conventional externally bonded reinforcement (EBR) technique or the externally bonded reinforcement on grooves (EBROG) technique were studied. The experimental results revealed the superiority of the EBR method over the EBROG technique due to the uniform bond between CC and the concrete surface. Using the EBR technique, improvements of 35% and 51% were observed in the load‐carrying capacity of the beams strengthened with one and two CC layers, respectively. It is while for the beam with an improved loading capacity of 51%, the crack width decreased from 5.3 to 2.1 mm, and the energy dissipation increased by three times compared to the control specimen. Theoretical analysis also was performed to calculate the load‐carrying capacity of the RC beams strengthened with CC layers.

Flexural performance of reinforced concrete beams strengthened using near-surface-mounted carbon-fiber-reinforced polymer bars: Effects of bonding patterns

The near-surface-mounted (NSM) fiber-reinforced polymer (FRP) technique is effective for enhancing the load carrying capacity of strengthened reinforced concrete (RC) beams. However, this technique significantly reduces the deformability of strengthened RC beams. To overcome this, the present study combines the NSM strengthening method with the partial bonding technique: the strengthening FRP reinforcement is partially bonded onto the concrete substrate). Six full-scale 4.3 m long RC beams strengthened with NSM FRPs using various bonding patterns were tested. The results indicated that mechanical interlocking grooves slightly improve the load carrying capacity, but have a negligible effect on the deformability of the strengthened beams. A decrease in the bond length increased deformability by 27.2 %, with only a 7.6 % drop in load capacity compared to that of the beam with full bonding. An advanced finite element model was developed and validated to confirm an optimal bond length of 930 mm for maximum flexural performance.

Experimental study on the behavior of pre-loaded reinforced concrete (RC) deep beams with openings strengthened with FRP sheets

Purpose Recently, the repairing of reinforced concrete (RC) structures attracted great research attentions, but the research interests were mainly concentrated on common repairing types. To this end, in this paper, a repairing of pre-loaded RC beams strengthened by aramid reinforcement polymers (AFRP) is presented. Furthermore, the purpose of this paper is to study the behavior of pre-loaded RC Deep beams under sustained load. The AFRP has many advantages such as controlling stresses distribution around the openings, controlling failure modes, and enhancing the structural capacity of pre-cracked RC beams. Design/methodology/approach Four specimens were experimentally tested: one specimen without strengthening, which is considered as control specimen, one strengthened specimen using AFRP without pre-cracking and two specimens subjected to pre-cracking load before prior to AFRP application. Furthermore, after validation of experimental data by using ANSYS software, a parametric study was conducted to investigate the effect of pre-damage level on shear capacity of RC beams. For pre-cracked beams, loading was first applied until the cracking stage, followed by specimen repairing with epoxy injection, and then the specimens were loaded again until failure point. Findings The result showed that pre-damage level and AFRP strengthening have great influence on the ultimate strength and failure mode. In addition, the results obtained from experimental tests were compared with those from numerical validation with ANSYS and showed good agreement. Originality/value Based on ACI guidelines, an analytical equation for calculating the shear strength of strengthened RC beams with openings subjected to pre-damage was then proposed, and the calculated results were compared with those from the tests, with differences not exceeding 10%.

The behavior of strengthened RC beams under pure torsion using NSM-CFRP rope

PurposeThe paper aims to introduces an experimental work to investigate the torsional behavior of reinforced concrete (RC) beams strengthened by near-surface mounted (NSM) carbon fiber-reinforced polymer (CFRP) ropes.Design/methodology/approachIn this research, nine rectangular RC beams of 250 mm × 300 mm cross-section and 1,600 mm in length were constructed and tested considering the studied parameters. These parameters include the length of the CFRP rope, the orientation of the CFRP rope, the arrangement of longitudinal and the scheme of NSM-CFRP ropes.FindingsIn comparison to control specimens, the results demonstrate a considerable improvement in the torsional response of RC beams strengthened with the CFRP rope. Additionally, specimens strengthened with 90° vertical ropes increase torsional moment capacity more efficiently than specimens strengthened with 45° inclined ropes since the stress concentration leads to premature debonding of the CFRP rope. Whereas RC beams' ability to withstand torsional moments is reduced as the distance between reinforcing CFRP ropes is increased. According to test results, adding CFRP ropes to RC beams' bottoms had a slightly positive impact on torsional response.Originality/valueThis paper fulfills an identified need to study how the using of the CFRP rope is effective in strengthening RC beam subjected to torsion moment.

Finite element modelling of reinforced concrete beam strengthening using ultra-high performance fiber-reinforced shotcrete combined with reinforcing bars

Ultra-high performance fiber-reinforced shotcrete (UHPFRS) is advanced concrete material for strengthening and repairing concrete structures, especially in narrow and difficult-to-access places. However, there has been little quantitative analysis of its strengthening capacity for concrete structures. Therefore, this paper develops a Finite Element (FE) model to simulate the structural behavior of reinforced concrete (RC) beams strengthened by a UHPFRS layer. The traction-separation model combined with the concrete damaged plasticity (CDP) model can accurately simulate the structural behavior of the NSC-UHPFRS composite beam by calibrating and validating with experimental results. Based on this FE model, a parametric study is conducted to asset the effect of the height, reinforcement ratio, and fiber orientation of the UHPFRS layer on the strengthening capacity of UHPFRS for the RC beam. The findings show that those parameters significantly impact the composite beam's load-displacement characteristics. It also contributes to a better understanding of applying UHPFRS in strengthening RC beams as well as structures to extend the service life effectively.

Overcoming the brittleness of shear failure: A new FRP-RSC strengthening philosophy

Due to the linear elastic stress–strain behavior of carbon fiber reinforced polymer (CFRP), the ductility of CFRP shear-strengthened reinforced concrete (RC) beams will be significantly reduced. Compared with shear capacity enhancement, increasing the ductility of CFRP shear-strengthened RC members is a much more challenging task, and a satisfactory solution has yet to be found. This paper introduces a new methodology that combines the brittle fiber reinforced polymer (FRP) with ductile rubber support composite (RSC) to form the FRP-RSC strengthening system. The variable stiffness RSC can adjust the stiffness of the strengthening system, which is achieved by the changed shear transfer actions in FRP, transverse reinforcement and concrete. Eight specimens were tested to evaluate the effectiveness of the FRP-RSC strengthening method. Experimental tests demonstrated that the displacement ductility with this FRP-RSC technique was 2.15 times that of the conventional externally bonded (EB) FRP strengthening, reaching remarkably 5.24. The mechanisms for enhancements in ductility, deformability and shear capacity were revealed. Poor matches were observed between the predicted FRP shear strength contribution (Vf) per existing models and test data. A new model that can predict Vf of FRP-RSC strengthened RC beams was developed, and better agreements between predictions and experimental results were obtained.

Durability of CFRP strengthened RC beam after six years exposure to natural hygrothermal environment with sustained loads

Exploring the durability of Carbon Fiber Reinforced Plastic (CFRP) strengthened concrete structures is a significant focus in the field of civil engineering. The majority of the present durability studies, which investigate the combined effects of external and environmental loading on CFRP-strengthened concrete structures, are conducted in accelerated aging environments. Nevertheless, this method fails to accurately reflect the real service conditions experienced by these structures in natural hygrothermal environments. In this study, a 6-year-long natural exposure experiment is conducted on CFRP-strengthened reinforced concrete (RC) beams under sustained loads. Additionally, the static and fatigue behavior of the exposed beam is investigated through both experimental and theoretical methods. The results indicated that the ultimate load of CFRP-strengthened RC beam remained unchanged after 6 years of natural exposure, as compared to that of non-exposed beams. However, noticeable changes were observed in their fatigue performance. The fatigue life decreased by 30 %, 75 %, and 86 % at loading levels of 0.60, 0.65, and 0.72, respectively. The fatigue limit decreased by 10 % and exhibited a dense distribution of cracks. Meanwhile, a fatigue life prediction model for RC structures strengthened with CFRP after long-term exposure to natural hygrothermal environment was established. In this model, the degradation of the CFRP-concrete interface behavior was considered. Through finite element analysis, two failure modes were predicted: fracture of the main reinforcement and the CFRP-concrete interface debonding failure under fatigue load. The corresponding fatigue life times were calculated. This model agrees well with the experimental findings.

The Efficiency of Using Machine Learning Techniques in Fiber-Reinforced-Polymer Applications in Structural Engineering

Sustainable solutions in the building construction industry have emerged as a new method for retrofitting applications in the last two decades. Fiber-reinforced polymers (FRPs) have garnered much attention among researchers for improving reinforced concrete (RC) structures. The existing design guidelines for FRP-strengthened RC members were developed using empirical methods that are based on specific databases, limiting the accuracy of the predicted results. Therefore, the use of innovative and efficient prediction tools to predict the behavior of FRP-strengthened RC members has become essential. During the last few years, efforts have been progressively focused on the use of machine learning (ML) as a feasible and effective technique for solving various structural engineering problems. Its capability to predict the behavior of complex nonlinear structural systems while considering a wide range of parameters offers a distinctive opportunity to make the behavior of RC members more predictable and accurate. This paper aims to evaluate the current state of using various ML algorithms in RC members strengthened with FRP to enable researchers to determine the capabilities of current solutions as well as to find research gaps to carry out more research to bridge revealed knowledge and practice gaps. Scopus databases were searched using predefined standards. The search revealed ninety-six articles published between 2016 and 2023. Consequently, these articles were analyzed for ML applications in the field of FRP retrofitting, including flexural and shear strengthening of RC beams, flexural strengthening of slabs, confinement and compressive strength of columns, and FRP bond strength. The results reveal that 32% of the reviewed studies focused on the application of ML techniques to the flexural and shear strengthening of RC beams, 32% on the confinement and compressive strength of columns, 6.5% on the flexural strengthening of slabs, 22% on FRP bond strength, 6.5% on materials, and 1% on beam–column joints. This research also revealed that the application of various ML algorithms has shown a significant improvement in resistance prediction accuracy as compared with the existing empirical solutions. Supervised learning techniques were the most favorable learning method due to their good generalization, interpretability, adaptability, and predictive efficiency. In addition, the selection of suitable ML algorithms and optimization techniques is found to be mainly dictated by the nature of the problem and the characteristics of the dataset. Nonetheless, selecting the most appropriate ML model and optimization algorithm for each specific application remains a challenge, given that each algorithm is developed with different principles and methodologies.

Flexural behavior of reinforced concrete beams strengthened with hybrid carbon-PET FRP laminates

This paper presents an experimental study of the flexural performance of reinforced concrete (RC) beams externally bonded with hybrid fiber-reinforced polymer (FRP) laminates made of carbon and polyethylene terephthalate (PET) fibers. Ten beam specimens were subjected to four-point bending tests, with a focus on assessing the effects of the stacking sequence and the elastic modulus of hybrid carbon-PET FRP laminates on the flexural performance of the strengthened beams. The failure modes, load-bearing capacities, displacement ductility of the specimens and strain distributions in the FRP laminates were examined and discussed. The experimental results showed that the load-carrying capacities of the FRP-strengthened specimens were significantly increased by 10.18∼27.98%, while the displacement ductility decreased by 51.36∼77.85%. The peak load and ductility of the beam specimens strengthened with PC (i.e., PET-C FRP) and CPC (i.e., C-PET-C FRP) stacking sequences were higher than those of their counterparts strengthened with two or three layers of hybrid FRP laminates. The accuracy and reliability of the calculation methods specified in ACI 440.2R-17, CNR DT 200 R1/2014 and GB 50608–2020 for estimating the flexural strengths of the strengthened RC beams were evaluated through a comparison of theoretical predictions with experimental results. The average predicted-to-tested ratios for the flexural strengths of the strengthened beams using ACI 440.2R-17, CNR-DT 200 R1/2014 (based on PE debonding failure), CNR-DT 200 R1/2014 (based on IC debonding failure), and GB 50608–2020 are 0.994, 0.704, 0.946, and 0.930, respectively.

An innovative prestressing system of prestressed carbon fiber sheets for strengthening RC beams under flexure

An innovative prestressing system was developed in this study, which can effectively anchor the prestressed carbon fiber sheets as well as conveniently apply prestress to the carbon fiber sheets. Tensioning tests of the carbon fiber sheet-anchor assemblies were first conducted to verify the anchorage behavior of anchors. Then this prestressing system was used for strengthening reinforced concrete (RC) beams to further verify its feasibility and investigate the effect of the impregnation and curing conditions of the carbon fiber sheets on the flexural strengthening efficiency. The results indicated that the tested ultimate capacity of the carbon fiber sheet-anchor assembly reached 72.1∼97.9% of the theoretical ultimate capacity of the carbon fiber sheet based on different impregnation and curing conditions. The concrete crushing failure and rupture failure of prestressed carbon fiber sheets occurred in the strengthened RC beams. The cracking and yielding loads of the RC beams with prestressed sheets were increased by 56.7∼68.5% and 21.7∼30%, respectively, while those with non-prestressed sheets were increased by 27.3% and 13.7%, respectively. The ultimate load was significantly affected by the impregnation and curing conditions. The prestressed carbon fiber sheets with the uncured full impregnation condition were not superior to the non-prestressed sheets in terms of the ultimate load, whereas the cured full impregnation and partial impregnation conditions were more effective than the uncured full impregnation condition. Finally, theoretical equations were used to calculate the cracking, yielding, and ultimate moments of RC beams strengthened with prestressed carbon fiber sheets.

Strengthening of RC beams with inadequate lap splice length using cast-in-situ and anchored precast ECC ferrocement layers mitigating construction failure risk

Design standards necessitate the use of a sufficient lap splice length when dealing with longer spans of Reinforced Concrete (RC) members. An inadequate lap splice length results in a reduction of both the flexural strength and ductility of reinforced concrete beams. The failure risk of these beams is considered a potential threat which is experimentally identified, numerically analyzed, and carefully mitigated in this research to increase building safety and sustainability to avoid risk of construction failure. The ongoing experimental and numerical research focuses on examining the structural performance of RC beams with insufficient lap splice length, which have been fortified through various applications of Engineered Cementitious Composite (ECC) ferrocement layers. A total of eleven beams, divided into four groups, were purposefully designed and tested under bending loads until they reached the point of collapse. The investigated parameters included the casting technique, installation strategy, and anchorage length (La) for such layers. Cast in situation and pre-casting scenarios were utilized in order to cast the strengthening ECC layers. The La for all layers was designed to be the main studied variable beside type of casting and installation technique. Three La values were studied: 30D, 40D, and 50D where D is the bar diameter of main reinforcement steel in tension side. It was found that, the application of chemical anchor bolts in cast in situation ECC ferrocement layers credited the higher enhancement in both cracking and ultimate stages by about 92–137% and 114–164% for cracking and ultimate levels, respectively. Then, the experimentally measured outcomes were employed for developing nonlinear Finite Element Models (FEMs) to simulate the performance of such ECC ferrocement layers that employed. The variance between numerical results and experimental counterparts ranged in between 6% and 9%, achieving an acceptable variance.

Numerical study on the torsional behavior of CFRP-strengthened RC beams

The present paper offers a numerical study on the behavior of reinforced concrete (RC) beams strengthened with carbon fiber reinforced polymer (CFRP) under pure torsional loading. The failure mode of RC beams significantly changed in accordance with torsional loading. Therefore, the effect of strengthening RC beams by CFRP under torsion is a vital area of study. This paper attempted to fill the gap by conducting a numerical (Abaqus) study, whereby the numerical investigation was in line with the parametric for a previous study of an experimental program. The numerical model achieved agreement with the results of the experimental program, then, this model was used by applying CFRP, instead of GFRP. Additionally, the numerical study was completely in line with the parametric study in terms of sample dimensions, steel reinforcement, number of FRP layers, and width of FRP strips, for the aim of comparing results. The comparative evaluation in this study aims to contrast the behavior of RC beams strengthened by CFRP with the behavior of those strengthened by GFRP under pure torsion. Parameters such as ultimate torsional moment, and the maximum angle of twist were studied. The study revealed that strengthening with CFRP improved the ultimate strength and post-cracking stiffness, in addition to localizing the damage.

Shear Strengthening of Reinforced Concrete Beams Using Engineered Cementitious Composites and Carbon Fiber-Reinforced Polymer Sheets

This study evaluates the performance of Reinforced Concrete (RC) beams enhanced in shear using Engineered Cementitious Composites (ECCs) and Carbon Fiber-Reinforced Polymers (CFRPs). The experimental study encompasses fifteen RC beams. This set includes one control specimen and fourteen beams fortified in shear with Externally Bonded (EB) composites. Two of these specimens were enhanced with ECC layers, while the remaining were augmented with combined CFRP-ECC layers. Variables in the test included the ECC layer thickness, matrix type, number of CFRP layers, and strengthening configurations such as full wrapping, vertical strips, and inclined strips. The results indicated that the shear capacity of the fortified beams increased by 61.1% to 160.1% compared to the control specimen. The most effective structural performance was observed in the full wrapping method, which utilized a single CFRP layer combined with either 20 mm or 40 mm ECC thickness, outperforming other techniques. However, the inclined strip method demonstrated a notably higher load-bearing capacity than the full wrapping approach for beams with double CFRP layers paired with 20 mm and 40 mm ECC thicknesses. This configuration also exhibited superior ductility compared to the rest. Furthermore, the experimental shear capacities obtained were juxtaposed with theoretical values from prevailing design standards.

Textile Types, Number of Layers and Wrapping Types Effect on Shear Strengthening of Reinforced Concrete Beams with Textile-Reinforced Mortar versus Carbon-Fiber-Reinforced Polymer

In the scope of this study, the strengthening of reinforced concrete beams with different types of composite materials was investigated experimentally and analytically. For the experimental part of the study, a total of seventeen reinforced concrete beams, one with high shear strength and sixteen with low shear strength, were fabricated. The beam with high shear strength and one of the beams with low shear strength were chosen as reference beams. The remaining fifteen beam specimens were strengthened with textile-reinforced mortar (TRM) and carbon-fiber-reinforced polymer (CFRP). While light and heavy carbon mesh were used for strengthening with TRM, unidirectional carbon textile was used for strengthening with CFRP. Other experimental parameters were the spacing of strips, the number of layers (one or two) and the way of wrapping (strip or full). Simply supported beam specimens were tested under three-point loading. Beam specimens were compared in terms of failure mode, ultimate load capacity, ductility index and energy dissipation capacity.

Numerical and analytical modeling of SPH‐ECC strengthened RC beams

AbstractMany studies have suggested that engineered cementitious composite (ECC) could be a highly efficient and cost‐effective material for enhancing the flexural strength of reinforced concrete (RC) beams. Recently two effective retrofitting configurations using steel and polyvinyl‐alcohol hybrid fiber reinforced engineered cementitious composite (SPH‐ECC) were proposed (Qasim et al., Eng Struct, 2023, 284, p. 115992) and their high effectiveness for enhancing the flexural strength of RC beam was verified experimentally. However, to examine the performance of these strengthening configurations thoroughly by conducting experiments to cover practical ranges of design parameters is deemed to be too expensive and time consuming. In this study, a numerical parametric study of SPH‐ECC strengthened RC beams was conducted by employing a validated finite element (FE) modeling procedure developed by the authors. The effects of four key design parameters including the compressive strength of concrete and SPH‐ECC, the thickness of SPH‐ECC strengthening layer and the area of reinforcement bars embedded in SPH‐ECC layers on the flexural performance of the strengthened beams were studied. Parametric study results showed that the area of reinforcement bars in the SPH‐ECC layers could significantly affect the flexural strength of the strengthened beams. Furthermore, in order to allow engineers to predict the flexural strength of the strengthened beams quickly, two simple but accurate analytical models were also developed for the two strengthening configurations considered. Their reliability and accuracy were then verified and confirmed by comparing with the parametric study results.