Flexural Strengthening Of RC Beams Research Articles

Uncertainty quantification of the flexural strengthening of RC beams with UHPC using improved metaheuristic algorithm

This study presents an artificial intelligence-based model to predict the flexural strengthening of RC beam/slab strengthened with UHPC (RC-UHPC) and perform uncertainty quantification of such values. Improved eliminate particle swamp optimization hybridized artificial neural network (IEPANN) was a model developed on artificial neural network (ANN) optimized by improved-eliminate-particle-swamp optimization (IEPSO). Experimental datasets were used to establish the hybrid ML model. The efficiency of IEPANN was compared against support vector regression (SVR) and multiple linear regression (MLR). The IEPANN demonstrates outstanding performance over MLR and SVR. The flexural strengthening of RC-UHPC depends on materials and geometrical configurations, which have stochastic characteristics. Convergence studies, sensitivity, and probabilistic analyses were conducted on each random parameter. Simulation results indicated that strengthening configuration is the most sensitive to flexural strengthening. Systematic assessment of uncertainties in flexural strengthening may lead to a higher confidence level in model outcomes, and RC-UHPC is examined and designed. It enhances construction reliability.

Finite Element Analysis of Flexural Strengthening of Reinforced Concrete Beams Using Near-Surface Mounted CFRP Rebars

Most of the standing structures today have already deteriorated or are on the verge of deterioration due to an increase in their age and harsh environmental conditions. For this very reason, the structures are in need of being upgraded or replaced. Retrofitting using near-surface mounted (NSM) fiber-reinforced polymer (FRP) rods has now emerged as a promising technique for strengthening the reinforced concrete members by increasing their flexural strength. This study aims to numerically investigate the efficiency of the NSM technique for flexural strengthening of RC beams by using finite element (FE) software, ABAQUS, and also evaluate the impact of variables such as concrete strength, embedded length of FRP rods, filler material used for the FRP rods, and the number of FRP rods provided. Validation of the finite element model was confirmed by first making a comparison with the experimental study presented in the literature for an un-strengthened beam. Thereafter, the validated model was used to simulate reinforced concrete beams strengthened with the NSM technique. The numerical results of the cracking moment, steel yielding moment, ultimate bending moment, and deflection at failure were reported and the impact of the variables was evaluated. The FE analysis results indicated that for the RC beams strengthened with NSM FRP rods, the flexural capacity significantly increased compared to the control beam, while the mid-span deflections of strengthened beams at failure decreased compared to the control beam.

Theoretical analysis on flexural strengthening of RC beams using GFRP composites in terms of strength to the weight ratio: A way forward

Aramid, Glass or Carbon Fibre Reinforced Polymer (GFRP/CFRP) are three types of composites that are commonly used in the civil, mechanical and automobile sectors worldwide. GFRP composites are often used for structural member strengthening, repairs, and rehabilitation. In comparison to CFRP and Aramid FRP composites, GFRP is easily available, inexpensive, good strength to the weight ratio, and has several additional benefits. The strength-to-weight ratio of GFRP composites and steel plates for flexural strengthening of RC beams is investigated in this work. Theoretical analysis for the RC beam strengthened with GFRP composites and steel plates were performed using the established equation based on Indian standards and the ACI code. The self-weight of the beam and the superimposed dead load owing to the block/brick work were taken into account in the design calculations. The beam's load carrying capability is inadequate due to the excessive load, thus it must be strengthened with different materials: GFRP Chopped Strand Mat (CSM) composites or steel plates. The evaluations were conducted under the assumptions that the loss of moment carrying capacity due to concrete deformation caused by bolt holes and failure due to GFRP composite delamination would be disregarded. Strength to weight ratio of GFRP composites and steel plate requirements have been computed and compared for the known dimensions, unit weight and tensile strength of the strengthening materials, and load carrying capability of the strengthened RC beam. Comparative study proves that the flexural strengthening of RC beams using GFRP composites, the strength to weight ratio is much higher than when the identical beams are strengthened with steel plate.

Experimental study on flexural strengthening of RC beams with NSM technique by different orientation of CFRP laminate

This paper gives the brief description on the use of laminates manufactured using Carbon Fiber Reinforced Polymer (CFRP) as strengthening material for the purpose of assessing the flexural strength in RC beams using Near Surface Mounted (NSM) technique. The main objective of this work was to assess the strengthened RC beam by considering the orientation of laminate as the main priority in NSM strengthening. This study gives the brief description about the utilization of tensile strength of laminate and efficiency of adhesive for different orientation of laminate. The strengthening methodologies adopted in this research work are Near Surface Mounted Laminate with Vertical Orientation (NSMLV), Near Surface Mounted Laminate with Vertical Orientation having Anchorages (NSMLVA) and Near Surface Mounted Laminate with Horizontal Orientation (NSMLH). The dimension of beam used was 200 mm (Breadth) X 200 mm (Depth) X 2300 mm (Length) and the effective span of the beam was considered as 2100 mm. All beams were designed as per Indian design code requirement to operate in under reinforcement criteria. A total of eight beams were casted, out of which two were used as control beams and the remaining were strengthened with different NSM techniques. The groove size used for NSMLV and NSMLH technique were different. The premature debonding takes place in NSMLV technique by not utilizing the tensile strength of laminate to greater extent, to overcome this drawback CFRP fabrics were used as the anchorages in four critical locations where debonding is predominate and this method was expressed as NSMLVA technique. This work was mainly focused on improving the ultimate load carrying capacity by satisfying the serviceability requirement as per codal provisions. The four-point bending test was performed for all the test specimens. In comparison with the control beams, all strengthened beams showed improved ultimate loads by satisfying the serviceability requirement. The ultimate load shows an increase of 21.74 %, 40.22% and 71.74% for NSMLV, NSMLVA and NSMLH technique respectively compared to control beams. The Stiffness of beam was increased by 14% and 30% respectively for NSMLVA and NSMLH technique compared to control beams. NSMLH technique maximizes ultimate load, which is 71.74% higher, and fulfills the serviceability requirements. In comparison with NSMLV and NSMLVA, the NSMLH Technique is the most effective method of strengthening which bears debonding to maximum extent and increases ultimate load by greater margin.

Flexural Strengthening of Large-Scale RC Beams with Nonprestressed and Prestressed CFRP Using Different Anchorages.

Externally bonded carbon-fiber-reinforced polymer (CFRP) technology can be used by different methods based on the anchorage device, CFRP type, and prestressing/nonprestressing. However, a direct comparison between the strengthening efficacies of different methods is still lacking. Seven large-scale RC beams were tested in this study to investigate the influences of the anchorage method, CFRP type, prestress, and prestressing system on the flexural strengthening efficacy of RC beams. The test results showed that the ultimate load increased by 38.3%, whereas the cracking and yielding loads were slightly affected when the anchorage method was enhanced from CFRP U-wraps to wedge-clamp anchors. The CFRP plate and CFRP sheet could provide a rather close flexural strengthening efficacy under the same CFRP strengthening amount. Compared to the nonprestressed CFRP plate, the prestressed CFRP plate was highly superior in improving the flexural behavior of RC beams. The cracking, yielding, and ultimate loads of the prestressed CFRP-strengthened specimens were 57.1%, 22.9%, and 5.9%, respectively, higher than those of the nonprestressed CFRP-strengthened specimen with an effective anchorage. The two types of prestressing systems based on the adhesive-friction anchor and wedge-clamp anchor were proven to be effective for flexural strengthening of RC beams with prestressed CFRP plates, and they could provide almost the same strengthening effect.

Experimental study of flexural behaviour of RC beams strengthened using near surface mounted CFRP strips and ropes

In this article, an experimental program was carried out to investigate the flexural behaviour of RC beams strengthened using side and bottom near-surface mounted (NSM) CFRP strip and rope. Thirteen reinforced concrete beams (150x250x1600mm) with flexural deficiency were cast. Different configurations have been used for strengthening RC beams, including side NSM, bottom NSM and both of them. Test results have shown that specimens strengthened with NSM CFRP strips have higher load carrying capacity and higher ultimate deflection than that strengthened with NSM CFRP ropes for the same configuration. FRP debonding, concrete cracks and concrete cover separations are more depicted in specimens strengthened with NSM CFRP ropes than that strengthened with NSM CFRP strips. Using NSM CFRP ropes or strips has increased the elastic stiffness of the strengthened specimens. Flexural strengthening of RC beams using CFRP ropes and strips has increased the load-carrying capacity NSM in a range of (18%–51%) and (30%–80%), respectively, compared to the control specimen. It is also found that beams with bottom strengthening increased the flexural capacity by (25%–32%) compared to RC beams with side strengthening

Effectiveness of Externally Bonded and Near Surface–Mounted CFRP Reinforcement in Flexural Strengthening of RC Beams: Numerical Approach

Externally bonded (EB) reinforcement and near surface–mounted (NSM) reinforcement were extensively studied to strengthen reinforced concrete beams in the last decades. However, few studies compare their effectiveness. This paper aims to study the effectiveness of EB and NSM strengthening techniques using carbon fiber–reinforced polymer (CFRP) strips in strengthening RC beams. In this study, three different parameters were studied, including the strengthening technique (i.e., NSM, EB), CFRP quantity, and NSM-CFRP distribution. In addition, two different bond behaviors were investigated, including perfect and cohesive models. A total of twelve beams were modeled, including six beams with perfect bond behavior and six beams with cohesive bond behavior. Each six tested beams include one control beam, two strengthened beams with EB-CFRP, and three strengthened beams with NSM-CFRP. All beams have the same cross-section dimensions, material properties, and steel reinforcement. The finite-element (FE) models were analyzed using a nonlinear FE analysis by ABAQUS software, and the results were validated with experimental works obtained from literature. In general, the developed FE models accurately predicted the ultimate strengths, strains, maximum deflections, and failure mode when compared to analytical and experimental results. For the same area of CFRP laminates, beams strengthened with the NSM system achieved higher ultimate strength but relatively lower stiffness when compared to beams strengthened with the EB system.

Flexural behaviour of GFRP strengthened RC beams under cyclic loading

The present study aims at investigating the cyclic flexural behavior of GFRP Strengthened RC Beams. For flexural Strengthening of RC beams, a total of fifty-four beams with bonded GFRP strips (600GSM) in varying Length, Width, and different Layers. Three beams without Strengthening (control beam) under cyclic loading. Cyclic loading is the function of incremental Push and Pull Load. Each beam was tested under reversed cyclic loading tested under a two-point loading system. GFRP is a material that has high tensile strength, good ductility, lightweight, so easy to mobilize, making GFRP an option for structural improvement. The test specimens were assessed in terms of load displacement and cracking pattern. The experimental results show that an increase strengthened RC beam load carrying capacity is observed to be in the range of 0 % to 25% for forwarding loading (Positive load) and 33.33 % to 66.66% for reverse loading (Negative load) and deflection is increased in the range 10.55% to 88.68% for forwarding loading (Positive load) and 17.73 % to 157.44% for reverse loading (Negative load) as compared to the control beam.

Flexural strengthening of RC beams using externally bondedaluminum plates: An experimental and numerical study

This research investigated the flexural strengthening of RC beams using Aluminum plates (AP). An experimental program including 8 RC beams were carried out. The width and depth of the beam were 150 and 300 mm respectively while the effective span of the beam was 1560 mm. The tensile reinforcement ratios of the beams were 0.38 and 0.548%. The external APs ratios (the cross sectional area of AP to the beam cross sectional area) were 0.10, 0.37 and 0.74% while the AP length to the beam length was 0.93. A Finite element analysis (FEA) was investigated to study many variables that influenced on the ultimate load and the behavior of the AP-strengthened beams such as AP length, using shear connectors, using various techniques of the end anchorages and using anchored/unanchored U-shaped APs. It was noticed that the improvement ratios of the ultimate load and the ductility of strengthened beams with tensile reinforcement ratio of 0.38% was better than the beams with tensile reinforcement ratio of 0.548%. The AP length to the beam span ratio had a significant effect on the ultimate load, the ductility and the failure mode of the beams. The ultimate deflection and the ultimate load of the AP strengthened beams that used shear connectors increased by 165 and 54 % respectively compared to the beam without shear connectors. Using U-shaped AP jacket accompanied with end anchorages enhanced the ultimate load by 109%. The ultimate load of the beams with bolted U-shaped AP jacket increased by 128%.

Shear and flexural strengthening of RC beams using BFRP fabrics

In a world in which the development of new technologies, materials and techniques plays a fundamental role, and the topic of sustainability is more relevant than ever, the application of eco-friendly Basalt Fiber Reinforced Polymers (BFRP) to structural engineering represents an important area of research. Research and innovation in the field of composite materials have provided a large variety of fiber reinforced polymers to be used for structural strengthening and rehabilitation. This paper presents an experimental research carried out to investigate the effectiveness of BFRP for the strengthening of reinforced concrete beams. Seven concrete beams used as specimens were tested utilizing a four-point bending load scheme. The properties of the unidirectional BFRP fabric used were exploited in different ways to produce shear and flexural strengthening systems. The BFRP fabric proved to be effective for increasing both the shear strength and the flexural capacity of the tested beams. Significant improvement of the ductility of the specimens was obtained as well. A comparison between the results of the shear strength calculations from different design standards and the experimental results is provided.

Comparative study on the flexural strengthening of RC beams using EB CFRP sheets, NSM CFRP bars, P-SWRs, and their combinations

The externally bonded (EB) carbon fiber reinforced polymer (CFRP), near-surface-mounted (NSM) CFRP and the prestressed steel wire ropes (P-SWRs) has been proven to be feasible and reliable flexural strengthening methods for concrete structures. However, debonding issues in EB CFRP sheets (or NSM CFRP bars) and space requirements for edge and spacing clearance of NSM CFRP bars (or P-SWRs) has limited the application of these three strengthening techniques. Therefore, the combinations of these methods need to be investigated and clarified. In this paper, experimental investigations on the flexural performances of seven concrete beams are presented, in which three of the beams were separately strengthened with EB CFRP sheets, NSM CFRP bars, and P-SWRs, respectively, and three of the beams were combinedly strengthened with two of the three techniques. Test results demonstrated that the flexural performances of beams strengthened with the combination with EB CFRP sheets, NSM CFRP bars, and P-SWRs are between the flexural performances of the beams strengthened with the corresponding individual strengthening techniques. It is found that the P-SWRs is favorable for combinations. In case the P-SWRs was combined with EB CFRP sheets or NSM CFRP bars for strengthening, the cracking load was increased to more than 230% and the maximum ultimate load-bearing capacity was increased to 150% when compared with the control beam. The debonding which occurred more or less in the beams strengthened with EB CFRP sheets or NSM CFRP bars or their combination was successfully eliminated by using the combination strengthening technique with P-SWRs. Also, the combination of P-SWRs with EB CFRP sheets or NSM CFRP bars is also favorable to improve the ductility of strengthened beams.

Comparative analysis of natural fiber reinforced polymer and carbon fiber reinforced polymer in strengthening of reinforced concrete beams

This paper presents a multi-objective assessment comparing the performance of natural fiber reinforced polymer (NFRP) and carbon fiber reinforced polymer (CFRP) in the flexural strengthening of RC beams. As NFRP laminates and concrete have similar elastic modulus, the NFRP-strengthened RC beams failed by FRP rupture, achieving higher ultimate loads and ductility than the CFRP-strengthened ones. Increasing NFRP reinforcement ratio and NFRP width significantly increased ultimate load and ductility. Narrow NFRP yielded higher strengthening efficiency than wide NFRP. Due to the large amount of impregnated epoxy resin, the cost advantage of natural fiber was greatly nullified and the total cost efficiency of NFRP laminates ranged between 60% and 160% that of CFRP laminates. Epoxy resin also increased the environmental impact of NFRP laminates, the NFRP and CFRP strengthening achieved similar environmental impact. Flax FRP generally yielded lower environmental impact than jute FRP. Prefabrication of NFRP laminates using vacuum infusion method is recommended to improve cost efficiency and lower environmental impact.

Flexural Strengthening of RC Beams with Prestressed CFRP Strips: Development of Novel Anchor and Tensioning System

Abstract External prestressing with carbon fiber-reinforced polymer (CFRP) strips is currently a well-developed and widely used technique to strengthen reinforced concrete structures subjected to b...

Flexural analysis and design of FRCM-strengthened RC beams

Fabric Reinforced Cementitious Matrix (FRCM) materials are thin, laminated composites consisting of a cementitious matrix that embodies one or multiple layers of continuous synthetic fabrics. FRCM is externally bonded to existing structural members subject to shear, bending, axial, or torsion induced stresses to enhance their performance. In the United States, FRCM material characterization is established by the “Acceptance Criteria AC434,” and the design and analysis of the FRCM-strengthened structural members follows the ACI549.4R-13 design guidelines. This paper investigates the analysis and design of carbon FRCM-strengthened RC beams in flexure. The FRCM-strengthened RC beams were experimentally tested, and the analytical and experimental results are compared in the paper. The ACI 549.4R-13 guidelines and design limitations are also discussed. The analytical and experimental results were in agreement at ultimate capacities. Collective results of studies on flexural strengthening of RC beams with different FRCM systems were used to establish a relationship between FRCM reinforcement ratio and increase in ultimate capacity which will help the designer at design phase to select the optimum FRCM reinforcement ratio for required strengthening demand.

Flexural strengthening of RC beams with NSM CFRP laminates

The paper presents test results of reinforced concrete beams flexurally strengthened with Carbon Fibre Reinforced Polymer (CFRP) laminates using the Near Surface Mounted (NSM) technique. RC beams with a cross section of 200 x 400 mm were tested in four-point bending. Two RC beams were strengthened with one NSM CFRP laminate installed into the concrete cover on the bottom side of the beam. One of the beams was strengthened under the self-weight (B10.1) and the second one under initial preloading equal to 83% of the ultimate load of the reference beam (B10.1o). Failure mechanisms, cracking pattern and flexural behaviour of the beams are described in the paper. All the strengthened beams failed by rupture of the CFRP laminates followed by the internal steel reinforcement yielding. High strengthening efficiency of the NSM strengthening was confirmed by 109% and 130% when compared with the non-strengthened beam, respectively for beams B10.1 and B10.1o.

Trial Think About on Flexural Quality of Fortified Solid Pillars Remotely Reinforced with CFRP Sheets

Fiber Reinforced polymer are ordinarily utilized for the Strengthening of Reinforced Concrete Structures. In that CFRP assumes a crucial job in giving the quality, solidness and malleability of the Reinforced solid Structures when contrasted and different filaments like GFRP, steel and aramid strands. Concentrate on Flexural Strengthening of RC Beams with CFRP (Multiple Layers) is completed. The component of the pillar examples are 100mmx200mmx1500mm. Fortified solid pillars remotely reinforced with CFRP sheets were tried utilizing a symmetrical two point concentrated static stacking framework. Two pillars were tried for Control Beam for Flexural (FB) and two bars tried for it is preloading of 70% for FB. Furthermore, after that it is tried by CFRP base just various layers for preloading of 70% for FB. The outcome appear in expanding quality when contrasted with preloading of 70% for FB. Test information on burden, diversion and extreme heap of every one of the pillar were acquired. The heap versus avoidance bends were contrasted and Control Beam for Flexural (FB), Preloading 70%FB and tried CFRP base numerous layer for preloading of 70% for FB. In this examination (CFRP) Carbon Fiber Reinforced Polymer gives apparent quality, solidness and malleability in flexure

Flexural Strengthening of RC Beams with Steel-Reinforced Grout: Experimental and Numerical Investigation

AbstractThis paper presents an investigation, both experimental and analytical, on RC beams that are strengthened in flexure using externally bonded steel-reinforced grout (SRG) composites. An expe...

Flexural strengthening of RC beams with externally bonded (EB) techniques using prestressed and non-prestressed CFRP laminate

This paper presents a detailed study on flexural strengthening of RC beams with externally bonded technique using carbon fiber-reinforced polymer laminate. The different strengthening methods used in this work are externally bonded laminate (EBL), externally bonded laminate with anchorage (EBLA), and externally bonded prestressed laminate with anchorage (EBPLA). All the beams were designed for under-reinforced condition. Totally, eight beams were cast; out of this, two beams were control beams. Strengthened beams were divided into three sets (EBL, EBLA, and EBPLA) of two beams each. The work was mainly concentrated on the improvement of ultimate load carrying capacity by delaying the debonding failure. The experimentation was done using two-point loading condition. The result shows that the ultimate load for all the strengthened beams was improved when compared to control beams. The beams strengthened with EBPLA technique show maximum increase in ultimate load, i.e., 73.91% with reference to control beams. All the control and strengthened beams satisfy the serviceability requirement. The comparative study was done on the theoretical and experimental results to check the efficiency of different strengthening codes.

Flexural strengthening of RC beams with CFRP grid-reinforced ECC matrix

This paper investigates the flexural performance of a series of RC beams externally bonded with carbon fiber-reinforced polymer (CFRP) grid-reinforced engineered cementitious composite (ECC) matrix. A total of 15 RC beams, including three control and twelve strengthened, were prepared and tested. The test variables included the longitudinal reinforcement ratio, the strengthening configurations that consisted of different cementitious matrices (ECC versus epoxy mortar), different installation methods (prefabricated versus cast-in-place), and different stiffness of CFRP grids. The test results showed that ECC is an ideal cementitious matrix for the strengthening applications where FRP grids are used as the external reinforcement. The flexural strengthening configuration using the epoxy adhesive to bond prefabricated CFRP grid-reinforced ECC plate proved to be the most efficient solution. For such configuration, the plate-end debonding can be avoided and the mid-span debonding can be almost suppressed. Flexural capacity analysis was conducted and demonstrated that the plane section assumption is valid and the full strength composite action can be nearly achieved for the strengthening system. The average ratio of the predicted peak loads to the experimental ones of the strengthened RC beams was 1.05.

TRM versus FRP in flexural strengthening of RC beams: Behaviour at high temperatures

The flexural behaviour of RC beams strengthened with TRM and FRP composites was experimentally investigated and compared both at ambient and high temperatures. The investigated parameters were: (a) the strengthening material, namely TRM versus FRP, (b) the number of strengthening layers, (c) the textile surface condition (dry and coated), (d) the textile material (carbon, basalt or glass fibres) and (e) the end-anchorage of the flexural reinforcement. A total of 23 half-scale beams were constructed, strengthened in flexure and tested to assess these parameters and the effectiveness of the TRM versus FRP at high temperatures. TRM exhibited excellent performance as strengthening material in increasing the flexural capacity at high temperature; in fact, TRM maintained an average effectiveness of 55%, compared to its effectiveness at ambient temperature, contrary to FRP which totally lost its effectiveness when subjected to high temperature. In specific, from the high temperature test it was found that by increasing the number of layers, the TRM effectiveness was considerably enhanced and the failure mode was altered; coating enhanced the TRM effectiveness; and the end-anchorage at high temperature improved significantly the FRP and marginally the TRM effectiveness. Finally, the formula proposed by the fib Model Code 2010 was used to predict the mean debonding stress in the TRM reinforcement, and using the experimental results obtained in this study, a reduction factor to account for the effect of high temperature on the flexural strengthening with TRM was proposed.