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In recent years, CFRP is the most popular material in strengthening RC members (columns, beams, slabs…etc.) as well as the textile-reinforced mortar (TRM) was also used as an alternative method for strengthening RC columns. The present study includes fifteen circular RC columns: One control column, ten columns strengthened by one or two layers of CFRP using EBR or EBROG methods, two columns was strengthened by textile-reinforced epoxy on grooves and last two columns were strengthened by textile reinforced mortar without grooves. The parameters of this investigation are type of strengthening technique (EBR, EBROG and TRM), number of CFRP layers, and the grooves configuration. The results showed that the columns strengthened longitudinally with one or two layers of CFRP strips using EBR technique enhanced the load-carrying capacity by 2 and 7.13%, respectively, when compared with control column. However, the load carrying capacity of RC columns strengthened by EBROG increased by the range of 11.65% to 71.4%. in comparison with control column. Finally, TRM strengthening method enhanced the load carrying capacity by about 21% to 58.5%. Also, the results showed that the EBROG and TRM approaches were improved the stiffness and ductility of the columns in comparison with EBR method.

Recently, a new proposed technique named; Externally Bonded Reinforcement on Grooves (EBROG) has been presented as a strengthening method to postpone or eliminate the undesirable debonding failure mode that is accompanying to Externally Bonded Reinforcement (EBR) method. This paper introduces an experimental and analytical study to evaluate the validity and accuracy of the formulas that were introduced by the standard codes and researchers, in estimating the ultimate load of RC continuous beams strengthened with carbon fiber reinforced polymer (CFRP) sheets in flexure. The experimental program includes testing of ten RC beams with cross section of (200×130) mm and two equal spans, each span has a 1050 mm length. The comparison between the ultimate load collected from the test results and that predicted using ten different analytical models is conducted. It is found that the ACI 440.2R-17 and most of other analytical models well predicted the ultimate load of RC beams strengthening with one layer of CFRP sheets using EBR, but most of these models significantly underestimate the ultimate load of tested beams that were strengthened using EBROG method. ACI, Shehata el. al., and Teng et al. models give close predicted load to the experimental results in case of EBR beams strengthened with two layers.

This paper deals with reinforced concrete beams strengthened by CFRP in flexure. The debonding between CFRP and the surface of the beam is the main problem. Many researchers around the world have made extensive efforts to study the phenomenon of debonding for efficient applications. Based on these efforts and different related field applications, code previsions and various models have been proposed for predicting debonding failure. Two code previsions and three typical models are presented in the current study. ACI-440.2R 17, CNR-DT 200 R1/2013, Said and Wu, Lu et al., and Teng et al. have been used to estimate the flexural strength of RC beams strengthened by CFRP with and without grooves. Test results of eleven flexural beams strengthened by CFRP sheet/laminate using externally bonded reinforcement (EBR) and externally bonded reinforcement on grooves (EBROG) methods were used in the current paper. The performance and accuracy of each model were evaluated based on these test results. Most of the prediction models that used in this study give a closer prediction of the flexural strength of beams strengthened by EBR compared to that of the beams strengthened by EBROG. Finally, the prediction results of CNR-DT 200 R1/2013 were the most accurate and approval with test results compared with other models in the current study

This paper offers a finite element method (FEM) to simulate the behavior of steel fiber reinforced concrete (SFRC) beams with corrosion of the longitudinal reinforcement using the ABAQUS package. This work was undertaken with the concrete damaged plasticity model (CDP). The expansion of corrosion product was utilized to represent the steel-concrete boundary to study the behavior of SFRC beams. Three beams with three volume fractions of steel fiber (0.8 %, 1.2 %, and 1.8 %) and three reinforced concrete (RC) beams with and without stirrups were created and tested under four-point loading to assess the shear capacity of beams. Corrosion of rebars at one of the RC beams that does not contain shear reinforcements will be studied. The crack patterns and load deflections of these beams were compared with experimental results found by the authors. The conclusions of this analysis will be valuable in considering the structural behavior of SFRC structures with uniform steel bar corrosion using FEM. Analytical results showed that the suggested model is qualified in better simulation and in accuracy of numerical and experimental results. The differences between analytical and experimental results were less than 8 % for load carrying capacity and 14 % for deflection; these differences are also satisfactory within the limits of the engineering conclusion.

Ductility is one of the most important requirements of RC design besides other requirements such as strength and stiffness. In recent years, concrete beams with a large amount of tensile reinforcement ratio (ρ) have been required in large projects, such as high‐rise buildings and bridges. Using high (ρ) increases the strength and stiffness of the beams and leads to a decrease the ductility. This paper aimed to investigate the effect of using steel fibers reinforced concrete (SFRC) layer in compression zone on the flexural behavior of over‐reinforced concrete beams. Partial replacement of concrete with SFRC layer in compression zone was used to avoid the brittle compression failure of concrete. For this purpose, 12 over‐reinforced concrete beams with a span of 1300 mm and a cross‐section of 120 mm × 180 mm were cast and tested under a three‐point loading. The first beam was used as a reference beam and others as strengthened beams using SFRC layer. The effects of thickness and length of strengthening layer, (ρ), volume fractions of steel fibers, and strengthening methods on flexural performance of tested beams were investigated. The flexural capacity, failure modes, crack patterns, load–deflection relationships, load–strain relationships, ductility index, and toughness were evaluated. The results showed that the suggested technique (SFRC layer in the compression zone) is an effective technique to increase ultimate load, ductility, and toughness by up to 35.72%, 121.01%, and 349.16%, respectively, compared to the reference beam. Furthermore, the failure mode changed from brittle to ductile failure. Also, one of the main advantages of this technique is allows to increase of (ρ) up to 8.55% (4.15ρb) without needing the compressive reinforcement. The results of this study indicate that the using SFRC layer in the compression zone is an appropriate and economical method to provide high flexural capacity and ductility over‐reinforced concrete beams. [ABSTRACT FROM AUTHOR]

The externally bonded reinforcement on grooves (EBROG) method is increasingly recognized as an alternative strengthening method that can overcome the debonding problem. This study aims to experimentally investigate the effectiveness of EBROG as compared to the conventional externally bonded reinforcement (EBR) method in strengthening reinforced concrete (RC) beams. Twelve RC beams have been tested under four point load bending. One of these beams has been designated as a reference beam, seven beams have been strengthened with carbon fiber reinforced polymer (CFRP) sheets, and four beams have been strengthened with CFRP laminates using EBROG or EBR methods. The effect of CFRP type, number of layers, as well as the type of strengthening methods on the flexural performance have been also investigated. The load, deflection, stiffness, and failure modes were recorded and discussed intensively. Overall, test results indicated that the flexural strength and stiffness of the strengthened specimens using EBR or EBROG methods increased compared to the control beam, where the increase in the load carrying capacity of beams strengthened using the EBR method ranged between 24.8 and 48.2% and by the EBROG method ranged between 31.7 and 76.7% of the control beam. The most interesting result obtained is that the failure mode of beams has been changed from debonding of CFRP material to rupture of CFRP in some samples strengthened by EBROG, which demonstrates the superior behavior of this strengthening technique as compared to the traditional strengthening using EBR. [ABSTRACT FROM AUTHOR]