Flexural Performance Of Reinforced Concrete Beams Research Articles

Flexural performance of RC beams using hybrid anchored ​CFRP sheets with bond defects

Hybrid anchorage technique can effectively prevent end debonding and impede intermediate debonding of CFRP sheet in strengthened reinforced concrete (RC) beams. However, its effectiveness in the presence of bond defects at the CFRP-concrete interface is unclear. Therefore, this study conducted four-point bending tests on CFRP-strengthened RC beams, considering two factors: bond defects (with and without) and strengthening methods (externally bonded and hybrid anchorage). The results showed that bond defects can lead to premature intermediate debonding of the CFRP sheet, resulting in a 22.49% decrease in debonding load due to local stress concentration around them. Owing to the effectiveness of the hybrid anchorage method, the propagation of the intermediate debonding is significantly impeded, leading to a 4.32% and 21.61% higher in ultimate load and deflection, respectively. This is because the hybrid anchorage can control the distribution of local cracks and improve the overall stress distribution of CFRP. A finite element analysis was performed and compared against the experimental results which shows good agreement. Then, parametric analyses were conducted to further analyze the flexural behavior of the strengthened beams with bond defects. Finally, an analytical model was proposed to predict the flexural capacity of the hybrid strengthened beams with bond defects.

Experimental study on the flexural behavior of reinforced concrete beam strengthened with novel prefabricated HSSM-UHPC thin plate

Ultra-high performance concrete (UHPC) has been used to strengthen reinforced concrete (RC) structures recently. Although UHPC has high compressive strength, the tensile strength is still low and, the high curing condition on site requirements of UHPC may hinder the further application in complex condition. In this study, a novel prefabricated UHPC thin plate, which is reinforced with high-strength steel wire strand meshes (HSSM), is proposed for rapidly strengthening RC beams. In order to understand the flexural performance of RC beams strengthened with the prefabricated HSSM-UHPC thin plate, four-point bending tests were conducted on three beams including one unstrengthened RC control beam (CB), one cast-in-place HSSM-UHPC strengthened beam (SUB) and one prefabricated HSSM-UHPC strengthened beam (PSUB). The failure modes of the beams were investigated and, the crack development process of the test beams was detailly observed by digital image correlation (DIC). Experiment results showed that compared with CB, the cracking, peak load of SUB and PSUB increased by 25.30%, 28.5% and 19.8%, 26.4%, respectively. However, the deflection ductility of the strengthened beams slightly decreased. Finally, calculation model and theoretical equation for predicting the cracking as well as peak flexural capacity of HSSM-UHPC plate strengthened beams were proposed. Comparison between theoretical and test results showed that the proposed model can accurately predict the cracking and peak capacity of the strengthened beams, and can be used for strengthening design.

The effect of strain lag for the flexural enhancement of RC beams strengthened by HMRE under secondary load

This paper presents experimental, numerical and theoretical studies on damaged reinforced concrete (RC) beams strengthened with high-strength stainless steel wire rope (HSSSWR) meshes reinforced engineered cementitious composite (ECC), in order to evaluate the influence of strain lag caused by secondary load on the strengthening effect. Four-point bending tests were first performed to investigate the failure mechanism of HSSSWR meshes reinforced ECC (HMRE) strengthened RC beams under secondary load. Then the parameters were comprehensively studied by finite element (FE) simulation. The results show that even under secondary load, the HMRE can still exhibit good crack-control capacity on concrete and gave significant enhancement in the flexural performance of RC beams. The strain lag of the strengthening layer, which resulted in inadequate utilization of its strength, was intensified with an increase in the initial load level or reinforcement ratio of the longitudinal steel bars, but was mitigated as concrete strength, ECC thickness, reinforcement ratio of HSSSWRs, or HSSSWR ultimate strength increased. Finally, a calculating model was proposed for predicting the bearing capacity of the damaged RC beams strengthened with HMRE, considering strain lag caused by secondary load.

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 behaviour of Reinforced Concrete Beams by Using Expanded Polystyrene Beads and Palm Oil Fuel Ash as Replacement Materials

The Reinforced Concrete (RC) beams containing Expanded Polystyrene Beads (EPS) and Palm Oil Fuel Ash (POFA) as sand and cement replacement with a percentage between 10% and 30% were studied in terms of load-deflection behaviour. RC beam’s size was 1000×150×150 mm and simply supported at spaced 750 mm apart. The 10% of POFA without EPS shows a slight increase which is 0.26% higher than normal concrete in compressive strength. The ultimate load and flexural performance of RC beams with EPS and POFA exhibited a decreasing trend. All beams’ ultimate load exceeds the design value. The cracks of the RC beam may be classified as vertical flexural cracks, and some of the cracks can be classified as shear cracks based on the crack angle. As the percentage of EPS and POFA increases above 20% for all specimens, cracking starts to change to shear cracking.

Performance of structurally deficient blended RC beam

In this study, the flexural behavior of structurally deficient reinforced concrete (RC) beams incorporating fly ash partially replacing cement was investigated. Structural deficiencies in RC beams typically arise from causes like old age, poor design, and material deterioration. To understand the performance of these deficient beams, a series of flexure tests were conducted. Nine categories of RC beam specimens, each measuring 150mm x 150mm x 700mm, were cast and divided based on steel reinforcement percentages into three sets: 100%, 70%, and 50% of required steel. Within each set, one specimen contained 0% fly ash (100% cement), another contained 20% fly ash (80% cement), and the last one contained 30% fly ash (70% cement). The study focused on analyzing crack propagation, applied load versus mid-deflection relationships, stress-strain relationships, and normalization curve relationships. The results demonstrated that incorporating fly ash improved the flexural performance of RC beams. Beams with fly ash exhibited enhanced crack resistance and higher load-bearing capacities, particularly with 20% fly ash. Lower steel reinforcement percentages increased flexural deficiencies, but the presence of fly ash mitigated some effects. This research provides a significant understanding of optimizing RC beam design for improved durability and performance, showcasing the potential benefits of using sustainable materials such as fly ash in construction.

Hybrid strengthening scheme for reinforced concrete beams: Flexural behaviour and large-scale testing

Revision of design standards, new regulations, and planned/unplanned increases in loadings potentially make buildings vulnerable to changes in capacity demands. This may result in some structural components of an existing structure requiring strength or stiffness improvement. Strengthening of capacity deficit members is widely recognised as the preferred and sustainable choice in terms of conserving resources and minimising the carbon footprint. Strengthening techniques such as Reinforced Concrete (RC) jacketing, steel jacketing and Fibre Reinforced Polymer (FRP) wrapping have been explored and widely used. However, when adopted solely, each scheme has its drawbacks. RC jacketing results in a considerable rise in the dead load, influencing the loading on the foundation and restricting the functional space available post-jacketing. Steel jacketing often lacks flexibility as a significant effort is required for installation. FRP improves the flexural strength response but produces low stiffness enhancement and lesser ductility. A hybrid strengthening option, i.e. a combination of the above strengthening methods, presents a viable option to address the limitations cost-effectively. This paper presents a pioneering attempt focused on improving the flexural performance of RC beams using a hybrid strengthening scheme comprising of RC jacketing and FRP. Four large-scale RC beams were prepared, and three of them were strengthened. The first was strengthened by RC jacketing, the second by a combination of RC jacketing and flexural FRP, and the last by the combination of RC jacketing, flexural FRP and FRP ‘U wrap’ in the shear zones. The specimens were tested using the four-point bending test. The flexural behaviour was assessed in terms of the peak moment capacity, flexural stiffness, load-displacement response, crack pattern and failure modes. The test results confirmed that hybrid strengthening leads to strength gain and stiffness gains of 105% and 90% respectively, as compared with the unstrengthened beam. The efficacy of the theoretically predicted strengths against the test strengths is assessed.

Deterioration law of flexural performance of RC beams with initial cracks under alternating action of salt freeze-thaw cycles and fatigue

Reinforced concrete (RC) bridges in cold regions are continuously exposed to the combined challenges of traffic loads, freeze–thaw cycles, and salt corrosion. This research delves into the deterioration mechanics and flexural performance of damaged RC beams when subjected to the dual stresses of salt freeze–thaw cycles (SFTCs) and fatigue loading. We conducted performance degradation tests on cracked RC beams subjected to alternating SFTCs and fatigue loading, followed by evaluations of their residual flexural capacities. In-depth analysis considered the impact of the number of alternating cycles and the initial crack width. The results indicate that the combined effects of alternating SFTCs, fatigue loading, and initial cracks significantly diminish the RC beams' flexural strength. As the number of alternating cycles and the initial crack width increased, there was a notable rise in mass loss, rebar corrosion, and a reduction in residual load carrying capacity and stiffness. Particularly, beams without initial cracks saw a 3.61 % reduction in load carrying capacity and a 24.06 % decrease in stiffness after four alternating cycles. In contrast, beams with an initial crack width of 0.10 mm experienced an 11.15 % decline in load carrying capacity and a 38.38 % drop in stiffness. The study concludes that while the combined effects of fatigue loading, SFTCs, and initial cracks are significant, initial cracks exhibit a more pronounced negative influence on load carrying capacity than on stiffness and ductility.

Mechanical Properties and Flexural Response of Palm Shell Aggregate Lightweight Reinforced Concrete Beam

This work focuses on examining the mechanical characteristics and flexural response of reinforced concrete (RC) beams by incorporating oil palm shell (OPS) lightweight aggregate from oil palm shell waste. The OPS aggregates are replaced in various percentages, such as 0 to 50% of natural coarse aggregate (NCA). Mechanical properties of OPS concrete were conducted, and these properties were used to quantify the flexural performance of RC beams. Five RC beams with several gradations of OPS aggregates were cast and tested for this investigation. The first cracking, ultimate strength, load-deflection behavior, ductility index, and failure patterns of OPS aggregate beams were investigated as the corresponding behaviors to the NCA concrete beam. The fresh properties analysis demonstrated lessening the slump test by varied concentrations of OPS concrete. Furthermore, compressive strength was reduced by 44.73%, 50.83%, 53.33%, and 57.22% compared to 10%, 15%, 20%, and 50% OPC substitution at 28 days. Increasing OPS content in concrete mixes decreased splitting tensile strength, comparable to the compressive strength test. Modulus of rupture and modulus of elasticity experiments exhibited a similar trend toward reduction over the whole range of OPS concentrations (0–50%) in concrete. It was revealed that the flexural capacity of beams tends to decrease the strength with the increased proportion of OPS aggregate. Moreover, crack patterns and failure modes of beams are also emphasized in this paper for the variation of OPS replacement in the NCA. The OPS aggregate RC beam’s test results have great potential to be implemented in low-cost civil infrastructures.

Flexural behavior of long-term loaded RC beams strengthened by ultra-high performance concrete

This study aims to investigate the flexural behavior of reinforced concrete (RC) beams strengthened with ultra-high-performance concrete (UHPC) after being loaded with long-term sustained loads for more than 20 years. Seven RC beams, originally fabricated in 1998, are categorized as the one-time pouring unnotched beam (Overall beam), one-time pouring notched beam (Notched beam), and two-time pouring beam (Repaired beam). These RC beams were firstly tested under the effect of long-term sustained loads which lasted 23.6 years. Subsequently, notched beams were strengthened using UHPC (hereafter named as Strengthened beam), which are tested under four-point bending test to investigate the significance of strengthening using the UHPC. Long-term load effects on the flexural performance of RC beams, including creep, cracking, concrete carbonization, and steel rebar corrosion were tested and analyzed. Test results showed that the maximum carbonization depth was less than the concrete cover depth and the steel rebars corrosion was among 1.51–2.47%, which indicates that the steel rebars inside the beam are well protected and are almost free of rust. The bearing capacity of the strengthened beams were increased by 24.6–48.6% compared with that of the Notched beam, which emphasizes the significance of strengthening using the UHPC. The displacement ductility of the strengthened beams was decreased by 82–94% compared with that of the Overall beam, however no brittle failure was observed during the test. It is worth mentioning that the internal changes, caused by the long-term sustained loading, could not be completely changed by adopting UHPC strengthening, while the stiffness reduction caused by long-term loading considerably influenced the flexural behavior of the UHPC strengthened beams. In addition, more attention shall be paid to the UHPC-NC vertical interface which remarkably affected the flexural performance of the Strengthened beams.

Flexural behavior of RC beams enhanced with carbon textile and fiber reinforced concrete

Concrete cracking is the major cause of steel corrosion and performance degradation of reinforced concrete (RC) members. To significantly enhance the crack resistance and flexural performance of RC beams, textile and fiber-reinforced concrete (FRC) were used in this study, and a simple anchoring method of textile was proposed to prevent debonding failure. Eight RC beams were designed and tested, and the test variables included carbon textile, anchoring method and pouring thickness of FRC. The test results revealed that the proposed anchoring method can effectively avoid the debonding phenomenon; both carbon textile and FRC can improve the crack resistance, improve the flexural capacity and reduce the damage of specimens. Among, the combination of carbon textile and FRC is the most effective method to improve the mechanical properties of specimens. Compared with the ordinary RC beam, the crack resistance and flexural capacity of textile-FRC composite beams can be increased by 79.56% and 39.04% respectively under specific conditions. With the increase of the pouring thickness of FRC, the mechanical properties of the specimens gradually enhanced, while the growth rate gradually slowed down. Through sectional analysis, the calculation methods of the load-midspan deflection curve and flexural capacity of textile-FRC composite beams were established. The accuracy and applicability of the calculation methods were verified by test and finite element analysis. In addition, theoretical calculation results show that the enhancing effect is not significant in the case that the pouring thickness of FRC is beyond 64% of the section height.

An Experimental Approach to Evaluate the Effect of Reinforcement Corrosion on Flexural Performance of RC Beams

The corrosion of reinforcing steel in concrete has been reported as one of the main durability problems of reinforced concrete (RC) structures exposed to chloride, carbonation or both. To investigate the structural performances of RC structures subjected to corrosive exposure, the corrosion of rebars embedded in concrete is accelerated to induce a targeted degree of reinforcement corrosion in a short time duration. Several earlier researchers have attempted to develop a setup to induce the accelerated corrosion of steel bars in concrete structures. However, the induced corrosion has not been simulative of the naturally occurring corrosion of steel in concrete, causing a lack of accuracy in the test results. In this study, an attempt was made to develop a novel approach that could be utilized to induce required degrees of reinforcement corrosion following a natural pattern. To demonstrate the efficacy of the proposed setup and procedure of introducing uniform reinforcement corrosion, RC beam specimens were designed, cast, and corroded to three different corrosion levels. After inducing reinforcement corrosion, the beams were tested under flexural stress, and then the corroded bars were extracted to measure the mass loss due to corrosion. The visual inspection and gravimetric and flexural test results showed the capability of the proposed corrosion setup and procedure to induce the targeted uniform corrosion of steel bars, simulating a real-life scenario and facilitating the evaluation of the effect of reinforcement corrosion on the flexural performances of RC beams with very high accuracy.

Flexural Performance of RC Beams Strengthened with Pre-Stressed Iron-Based Shape Memory Alloy (Fe-SMA) Bars: Numerical Study

The iron-based shape memory alloy (Fe-SMA) has promising applications in strengthening and repairing aged steel-reinforced concrete structural elements. Fe-SMA bars can produce pre-stressing forces on reinforced concrete members by activating their shape memory phenomenon upon heating. This study aims to numerically evaluate the impact of pre-stressed Fe-SMA bars on the structural behavior of reinforced concrete (RC) beams at the serviceability and ultimate stages. Nonlinear finite element (FE) models were developed to predict the response of RC beams externally strengthened with Fe-SMAs. The model shows to correlate well with published experimental results. A parametric investigation was also carried out to examine the effect of various concrete grades, pre-stressing levels, and Fe-SMA bars’ diameter on load-deflection behavior. In light of the innovative nature of the Fe-SMA strengthening technique, a comparison investigation was established between RC beams strengthened with Fe-SMA bars against different pre-stressing systems, such as carbon fiber reinforced polymer (CFRP) bars, glass fiber reinforced polymer (GFRP) bars, and steel strands. The numerical findings showed a significant increase in the beams’ load-carrying capacity with larger Fe-SMA bars’ diameter. Specifically, using 12 mm Fe-SMA bars instead of 6 mm increased the beam’s strength by 73%. However, a 14% reduction in ductility was recorded for that case. Moreover, the pre-stressing level of Fe-SMA bars and concrete grade showed a negligible effect on the ultimate strength of the examined beams. Moreover, increasing the pre-stressing level and concrete strength significantly enhanced the load-deflection response in the serviceability stage. Furthermore, using 2T22 mm of Fe-SMA bars resulted in a better structural performance of RC beams compared to other techniques with 2T12 mm, with a comparable cost. Thus, it can be concluded that using Fe-SMA bars embedded in a shotcrete layer attached to the beam’s soffit is a viable and promising strengthening strategy. Nevertheless, further experimental investigations are recommended to further ascertain the reported findings of this numerical investigation.

Flexural strengthening of RC beams with built-in basalt-fibre-reinforced polymer T-plates

Basalt-fibre-reinforced polymers (BFRPs) are expected to be excellent materials for the repair and rehabilitation of civil infrastructure due to their sound mechanical properties, high corrosion resistance and low cost. However, reported studies investigating reinforced concrete (RC) beams externally strengthened with BFRP are limited. The objective of this work was thus to determine the effect of BFRP strengthening on the flexural performance of RC beams. Four RC beams with a rectangular cross-section were fabricated, strengthened using different BFRP reinforcement techniques and tested under four-point bending until failure. The failure mode, crack widths, number of cracks, load–deflection response curves and ductility of the beam systems were recorded and analysed. The experimental results showed that, compared with a control beam, the stiffness and ultimate capacity of the strengthened beams were increased by 8–23% and 14–30%, respectively. To predict the load-carrying capacity and deflection of the test specimens, three-dimensional finite-element (FE) modelling was performed using Abaqus software to simulate the behaviour of RC beams strengthened with BFRP plates. The predictions of the FE model matched the experimental results well in terms of the mid-span deflection and load-carrying capacity.

Eco-friendly concrete with chemically treated end-of-life tires: Mechanical strength, shrinkage, and flexural performance of RC beams

The disposal of waste end-of-life vehicle tires has become a major environmental issue around the globe, as it is not completely biodegradable and can be a massive threat to the environment. Several researchers have attempted to use tires as aggregate with and without chemical treatment. However, to the best of the authors' knowledge, no research has investigated the performance of clay brick aggregate (CBA) concrete by replacing the CBA with bleached powder-treated waste rubber tire aggregate (WRTA) at different treatment times. Within this context, this study examines the mechanical strength, shrinkage, and flexural performance of reinforced concrete (RC) beams made with seven replacement percentages (0, 5, 10, 15, 20, 30, and 50 % by volume) of CBA by WRTA treated with H2O, NaOH, and bleaching powder (BP) for 2 h and 72 h. The experimental outcomes reveal that as the percentage of untreated WRTA increases, the slump, dry density, and mechanical strength decrease. Furthermore, concrete shrinkage increases with the increasing content of untreated WRTA in the mix. Likewise, the flexural load of RC beams declines with an increased percentage of untreated WRTA. It has been observed that the concrete made with WRTA treated with NaOH and BP has significantly higher mechanical strength, a flexural load carrying capacity of RC beams, and lower shrinkage compared to the untreated WRTA. The improvement in all properties was more remarkable for the treatment with BP than NaOH and treatment of 72 h than 2 h. The findings reveal that 15 % WRTA treated with BP solution for 72 h can be used as a CBA replacement whose design strength is not significantly high (fcat28days ≈ 20 MPa).

Flexural performance of RC beams strengthened with inorganic adhesive bonded NSM CFRP bar

Organic adhesives (e.g. epoxy) have been widely utilized in near-surface mounted (NSM) carbon fibre reinforced polymer (CFRP) strengthening technique for reinforced concrete (RC) structural members. Their inevitable shortcomings, such as poor fire resistance, emission of toxic fumes, and incompatibility with concrete substrate, necessitate the advancement of eco-friendly inorganic adhesives. In this study, two types of inorganic adhesives, including ordinary Portland cement mortar (OPCM) and alkali-activated slag mortar (AASM), were adopted in the NSM CFRP bar strengthening method for RC beams. The inorganic adhesive type, bonding length, and additional anchorage device on CFRP bar were considered as parameters in the strengthening scheme. One control beam and four strengthened beams were fabricated and tested, followed by comparison of their failure modes, loading behaviour, and reinforcement strains. The results show that all the strengthened beams exhibit higher ultimate loads than the control beam. Comparing to the OPCM, the AASM is more effective in mitigating debonding of CFRP bar and enhancing the ultimate load of beams. Furthermore, it is essential to provide a sufficient bonding length for AASM bonded NSM CFRP bars to guarantee their strengthening effectiveness. The addition of anchorage device for CFRP bars can further enhance the synergistic action between CFRP bar and adhesive, leading to a further enhancement in flexural strength and CFRP bar strain. In addition, the flexural strengths of OPCM or AASM bonded NSM CFRP bar-strengthened beams can be accurately predicted by the equations provisioned in ACI 440.2R-2017.

Behavior of Reinforced Concrete Beams Strengthened in Flexure using Externally Bonded Aluminum Alloy Plates

The utilization of carbon, glass, aramid and basalt fiber reinforced polymers (FRP) in shear and flexural strengthening of reinforced concrete beams have been well established and proved its effectiveness. As externally bonded strengthening materials, FRP composites have many advantages and some disadvantages. The main disadvantage of FRP composites are that they brittle materials. Aluminum Alloy (AA) plates are ductile materials, which is a desirable characteristics for reinforced concrete (RC) beams. This study investigated the structural integrity of RC beams strengthened in flexure using externally bonded AA plates. Four beams were cast and three of them were strengthened in flexure using AA plates. The AA plate covered 90% of the beams’ span and two of the beams were anchored at both ends of the AA plates using one layer and two layers of carbon fiber reinforced polymer (CFRP) laminates. The control beam was not strengthened and was therefore used as bench mark for measuring the performance the strengthened beams with and without anchorages. The beams were tested until failure under four-point bending. Load-deflection curves and load-strain curves were plotted and the ductility indices of the tested beams were calculated. It was observed that the strengthened beams showed increase in strength up to 40.3% and in ductility up to 55% of that of the control beam. However, the failure ductility of the strengthened beams with two layers of U-wraps decreased slightly, by 5% of that of the control beam. It can be concluded that AA plates could be used as strengthening materials to enhance the flexural performance of RC beams. In addition, the use of U-wrap CFRP anchorages influenced the types of failure modes of the tested beams.

An experimental study on flexural performance of RC beams strengthened by NSM technique using GFRP strips for a resilient infrastructure system

Near surface mounted method (NSM) is an emerging technique with wider scope in repair and rehabilitation. In this method as lesser repair material is used and as FRP is placed inside grooves it offers higher serviceability, resistance to corrosion, higher impact damage resistance and fire resistance there by providing higher long-term economy. This method of strengthening avoids adverse environmental impacts, interruptions to service therefore considerable savings in time and cost. Hence, NSM technique helps in building resilience into infrastructure system. This paper is to present the experimental work on enhancing flexural performance of reinforced concrete beams by implementing NSM method. The side near-surface mounted (S-NSM) is an alternative method used for applying fibre reinforced polymer (FRP) flexural strengthening on reinforced concrete (RC) beams as in practical case the bottom face of the beam may be some times inaccessible. The S-NSM method places the FRP grooves at the sides of the beam on either side, rather than at the bottom in the normal near surface mounted (NSM) method. The present study is carried out on the use of NSM for strengthening of RC deficient beam designed for 30kN with NSM composite material namely glass fibre reinforced polymer (GFRP) strips as reinforcement. The experimental work included control specimen and strengthened beams at different locations and orientations of GFRP that is both bottom NSM and side NSM method (both horizontal and vertical orientation of strips) are studied and these beams are subjected to two point bending flexural test. The effect of groove location, crack pattern, deflection at midspan and quarter span and also different modes of failure are the characteristics studied based on results obtained.

Numerical study on the flexural performance of RC beams with externally bonded CFRP sheets

The numerical investigations on the structural performance of reinforced concrete (RC) beam strengthened with externally bonded carbon fiber-reinforced polymer (CFRP) sheets are presented. The nonlinear characteristics of materials (i.e., stress-strain relationships of steel reinforcement, concrete, CFRP, and CFRP/concrete bond stress-slip behavior) were adopted in three-dimensional finite element (FE) models. The validation of FE models was conducted by comparing the laboratory works carried out on two RC beam specimens with 2000 mm length, 300 mm height, and 120 mm width. The numerical results show a good correlation with the experimental results of the beam specimens, such as load-displacement curves, crack patterns, and failure modes. They allow confirming the capability of the developed FE model to predict the flexural performance of strengthened beams considering CFRP/concrete interfacial behavior. Furthermore, parametric investigations were performed to determine the effect of flexural strengthening schemes, CFRP length with or without U-wraps, and multiple CFRP layers on the flexural performance of strengthened beams.

Flexural performance of reinforced concrete beam made with waste foundry sand as fine aggregate

PurposeThe structural behavior of reinforced concrete (RC) beams made with waste foundry sand (WFS) was examined in this study by using investigational data. Five RC beams were tested in this present work, four beams with varying WFS content and one beam with natural aggregates. The factors considered for studying the flexural performance of RC beams were WFS content (10%, 20%, 30% and 40%), 15% Ground Granulated Blast Furnace Slag (GGBS) is used as supplementary cementitious (SCM) content for all beams and tension reinforcement ratio (0.95%). The crack pattern of the RC beams with WFS (RCB1, RCB2, RCB3 and RCB4) was similar to that of referral beam–RCB0. The RC beams made with WFS (RCB1, RCB2, RCB3 and RCB4) show lesser number of cracks than referral beam–RCB0. It is observed that RCB1 beam shows higher ultimate moment carrying capacity than other RC beams. A detailed assessment of the investigational results and calculations based on IS: 456-2000 code for flexural strength exhibited that the present provisions conservatively predicts the flexural strength and crack width of RC beams with WFS and 15% GGBS. It is suggested that 10% WFS can be used to make RC beam.Design/methodology/approachIn this present work, four RC beams made WFS and one RC beam made with natural aggregates. 15% GGBS is used as SCM for all RC beams. After casting of RC beams, the specimens were cured with wetted gunny bags for 28 days. After curing, RC beams like RCB0, RCB1, RCB2, RCB3 and RCB4 were tested under a four-point loading simply supported condition. An assessment of investigational results and calculations as per IS: 456-2000 code provisions has been made for flexural strength and crack width of RC beams with WFS and 15% GGBS. The crack pattern is also studied.FindingsFrom this experimental results, it is found that 10% WFS can be used for making RC beam. The RCB1 with 10% WFS shows better flexural performance than other RC beams. RC beams made with WFS show lesser number of cracks than referral beam–RCB0. IS: 456-2000 code provisions can be safely used to predict the moment capacity and crack width of RC beams with WFS and 15% GGBS.Originality/valueBy utilization of WFS, the dumping of waste and environmental pollution can be reduced. By experimental investigation, it is suggested that 10% WFS can be used to make RC structural members for low cost housing projects.