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The objective of this research is to experimentally study the flexural behavior of hybrid reinforced concrete beams. Three test beams, each with dimensions of (2200 X 150 X 240) mm, were fabricated for this purpose. The first beam was constructed using ordinary concrete, while the second beam consisted of two layers of high-strength concrete in the compression zone and normal concrete in the tension zone. The third beam was entirely cast using high-strength concrete. In terms of reinforcement, all beams were equipped with 2φ12 steel bars in the tension zone and 2φ12 steel bars in the compression zone. Additionally, φ12 steel bars were employed to resist shear forces, distributed along the length of the beams with a spacing of 125 mm c/c. Two-point loading was applied to all beams until failure occurred. The results obtained from the experimental tests reveal that the use of hybrid concrete beams enhances the ultimate load capacity by approximately 20.93%. On the other hand, beams constructed entirely from highstrength concrete exhibited an increase in failure load capacity by approximately 28.68%. [ABSTRACT FROM AUTHOR]

This study intended to measure the efficiency of different strengthening techniques to advance the flexural characteristics of reinforced concrete (RC) beams using glass fiber-reinforced polymer (GFRP) laminates, including externally bonded reinforcement (EBR), externally bonded reinforcement on grooves (EBROG), externally bonded reinforcement in grooves (EBRIG), and the near-surface mounted (NSM) system. A new NSM technique was also established using an anchorage rebar. Then, the effect of the NSM method with and without externally strengthening GFRP laminates was studied. Twelve RC beams (150 × 200 × 1500 mm) were manufactured and examined under a bending system. One specimen was designated as the control with no GFRP laminate. To perform the NSM method, both steel and GFRP rebars were used. In the experiments, capability, as well as the deformation and ductileness of specimens, were evaluated, and a comparison was made between the experimental consequences and existing standards. Finally, a new regression was generated to predict the final resistance of RC beams bound with various retrofitting techniques. The findings exhibited that the NSM technique, besides preserving the strengthening materials, could enhance the load-bearing capacity and ductileness of RC beams up to 42.3% more than the EBR, EBROG, and EBRIG performances. [ABSTRACT FROM AUTHOR]

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Shear strength of a reinforced concrete (RC) member should be larger than its flexural strength, in order to prevent the shear failure, which is sudden and brittle. The reliability of a RC beam against the shear failure is closely related to the reliability of the equation determining its shear strength. In this study, the reliabilities of shear strength equations of RC beams were investigated by constructing the performance function between prediction equations and experimental results using a second-moment approach. It is assumed that the random variables are statistically independent, and the correlation effects are not taken into account. It is observed from the reliability rankings that the equation of EN 1992:2004 yields the lowest failure probability while the equation of Zsutty is the highest failure probability. [ABSTRACT FROM AUTHOR]

This research aims to conduct a comparative analysis of the first crack load, flexural strength, and shear strength in reinforced concrete beams without stirrups. The comparison is made between the conventional model developed according to the current design code (ACI building code) and an unconventional approach using Artificial Neural Networks (ANNs). To accomplish this, a dataset comprising 110 samples of reinforced concrete beams without stirrup reinforcement was collected and utilised to train a Multilayer Backpropagation Neural Network in MATLAB. The primary objective of this work is to establish a knowledge-based structural analysis model capable of accurately predicting the responses of reinforced concrete structures. The coefficient of determination obtained from this comparison yields values of 0.9404 for the first cracking load, 0.9756 for flexural strength, and 0.9787 for shear strength. Through an assessment of the coefficient of determination and linear regression coefficients, it becomes evident that the ANN model produces results that closely align with those obtained from the conventional model. This demonstrates the ANN's potential for precise prediction of the structural behaviour of reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Structurally deficient bridges are commonly retrofitted using conventional methodologies, including reinforced concrete, steel jackets, and fiber-reinforced polymers. Although these retrofit methods aim to improve structural performance, exposure to aggressive environments may undermine the durability performance of the retrofit material. More recently, ultra-high-performance concrete (UHPC) has provided an alternative to conventional construction methods, with its superior material characteristics favoring its use in retrofit applications. In this study, a large-scale reinforced concrete (RC) T-beam is constructed and artificially damaged. The T-beam is then retrofitted with an external envelope of UHPC on all faces. Sandblasting is introduced to the surface, providing partially exposed reinforcement in the T-beam to simulate material deterioration. Additional reinforcement is placed in the web and flange, followed by casting the enveloping layer of UHPC around the specimen. The feasibility of this method is discussed, and the structural performance of the beam is assessed by subjecting the beam to cyclic and ultimate flexural loading. This paper presents the results of cyclic and ultimate testing on the RC-UHPC composite T-beam regarding load–displacement, failure mode, and strain responses. The retrofitted T-beam specimen is subjected to a cyclic loading range of 131 kN for 1.576 million cycles. Despite no visible cracks in the cyclic testing, the specimen experiences a 12.22% degradation in stiffness. During the ultimate flexural testing, the specimen shows no relative slip between the two concretes, and the typical flexural failure mode is observed. By increasing the longitudinal reinforcement ratio in the web, the failure mode can shift from localized cracking, predominantly observed in the UHPC shell, toward a more distributed cracking pattern along the length of the beam, which is similar to conventional reinforced concrete beams. [ABSTRACT FROM AUTHOR]

This study aims to investigate the effectiveness of para-aramid fiber sheet in enhancing the flexural performance of reinforced concrete (RC) beams made with Environmental-Friendly Recycled Coarse Aggregates. The experimental program examines the effect of substitution ratio of recycled aggregates (0%, 30%, and 50%), type of para-aramid fiber sheet (KN 206 RFL and KN AA070-RFL), and the method of fiber sheet attachment (bottom and bottom-side). The test results show that the ultimate load-carrying capacity of RC beams reinforced with para-aramid fiber sheet attached to the bottom and side parts increased by 23.9% compared to the unreinforced specimens. The main findings of the study include the identification of the BU-type attachment method as the most effective method for enhancing the flexural performance of reinforced concrete beams. The comparison of the experimental results with analytical predictions showed that the nominal flexural strength obtained from the experimental study was lower than the analytical predictions, but the ductile capacity of the specimens indicated the effectiveness of para-aramid fiber sheet reinforcement in EFRCA RC beams for flexural strength. The study highlights the potential of using para-aramid fiber sheet in improving the flexural behavior of RC beams made with recycled aggregates, offering a sustainable solution for the construction industry. [ABSTRACT FROM AUTHOR]

Near Surface Mounted (NSM) Carbon Fiber-Reinforced Polymer (CFRP) reinforcement technique to improve the flexural strength of reinforced concrete members has become increasingly attractive in recent years. In this study, the practical problem of concrete cover depth cutting limitation was investigated. Twelve specimens were tested by four-point bending until failure. Experimental parameters include concrete cover depth, CFRP reinforcement type, CFRP positioning, and stirrups status. Furthermore, a nonlinear FEA model was developed to simulate the tested beams and was able to predict the experimental behavior satisfactorily. A series of parametric studies were then performed using this model to understand the effect of various reinforcement parameters on the flexural performance of the beam. The results showed that Strengthening with CFRP resulted in a significant increase in yield and ultimate strengths, but a significant ductility loss was recorded due to CFRP strip debonding in the strengthened beams, this problem was addressed by using more efficient strengthening techniques utilizing the effective bond length and a proper groove depth and positioning for the NSM bars. [ABSTRACT FROM AUTHOR]

In this study, the feasibility of utilizing locally produced coarse recycled aggregate (RA) from demolition waste in the UAE for structural applications was investigated. A comprehensive literature review on the subject showed that the shear and flexural responses of reinforced beams utilizing aggregate from concrete demolition waste are greatly dependent on the aggregate replacement ratio and the quality of the recycled aggregate. The experimental program in this study consisted of three phases. Phase I focused on the evaluation of the physical and mechanical characteristics of the RA, Phase II addressed the mix design and fresh and hard properties of the concrete, and Phase III dealt with the flexural and shear behavior of structural members. The research involved twelve 150 mm × 300 mm reinforced concrete beams with a length of 1500 mm or 2000 mm that were made with 0% (control), 50%, or 100% recycled coarse aggregate, replacing natural coarse aggregate (NA). Two target concrete compressive strengths, 25 and 35 MPa, were considered in the investigation. The results showed that the recycled aggregates had lower crushing and LA abrasion values by 40% and 18–28%, respectively, whereas the absorption capacity was 40–300% higher compared to the natural aggregate. In addition, the mechanical properties of the concrete made with different replacement ratios (R%) of RA were either similar or slightly less than those of the control mix. The shear beam tests with f c ′ = 25 MPa showed that the 50%- and 100%-replacement-ratio beams demonstrated closely matched normalized shear strength values that exceeded their corresponding NA beam by 12.5%, while the shear beam tests with f c ′ = 35 MPa showed that the NA beam exhibited normalized shear strength surpassing the 50% RA and 100% RA beams by 12.5% and 17.5%, respectively. In the flexural beam tests, the flexural strength exhibited minimal disparities for the beams that shared the same RA% but differed in their compressive strength targets, and overall, the variation in the RA% had a marginal impact on the flexural strength of the beams. Further, an increase in the RA% corresponded to an increase in the shear ductility index, which was in contrast with the findings on the flexural ductility index. Furthermore, predictions of flexural strength using the ACI318-19 code and shear strength using the strut-and-tie model yielded comparable results to the experimental ones. [ABSTRACT FROM AUTHOR]

In this paper, the effectiveness of the strengthening by a wooden plate for reinforced concrete (RC) beams that incorporate waste sawdust (SD) as a partial substitute for fine aggregate (sand) has been investigated. To this end, two types of concrete mixtures were made: normal concrete (NC) and sawdust concrete (SDC), which was made by substituting 15% of the volume of sand with SD. Five RC beams (100 mm in depth, 200 mm in width, and 1500 mm in length) were experimentally tested for flexural behavior under four-point loading. Three strengthening schemes were used in this study. The first scheme used a wooden plate that was only fixed by an adhesive layer. The second and third schemes were applied by a wooden plate, which was fixed by an adhesive layer and steel angles (two and eleven angles). The findings of the study indicate that although the concrete's workability, compressive, and splitting tensile strengths were reduced with the addition of SD, the ultimate load of the beam with SD was lower than that of the control beam, with a slight variation of approximately 4%. Moreover, strengthening the RC beam with a wooden plate and two steel angles yielded the highest load capacity among all tested beams, 20% higher than the control specimen. The study's findings offered useful information for developing eco-friendly sawdust concrete beams with efficient strengthening techniques for potential future uses. [ABSTRACT FROM AUTHOR]

The motive of building sustainable structures and strengthening the structural members is important to overcome the problems associated with poor initial design and/or construction, accidental events, and degradation related to the environment. This paper aims to assess the flexural behavior of a prestressed basaltic fiber-reinforced polymer- (FRP-) strengthened reinforced concrete (RC) beam under static load through the finite-element method using ABAQUS CAE that is validated with experimental results from relevant literature. To achieve the desired objective, 18 models were prepared based on prestressing level, thickness of basalt FRP (BFRP), width of BFRP, length of BFRP, bond between concrete and BFRP, and type of FRP as study parameters. The results indicate that the use of prestressed BFRP is efficient in strengthening the flexural strength of the RC beam. Compared to nonstrengthened specimens, the flexural capacity of the specimens strengthened with BFRP at prestressing levels of 0%, 15%, 35%, and 45% show enhancement of 6.09%, 9.17%, 13.89%, and 17.57%, respectively. While increasing the width, length, and thickness of the prestressed BFRP section, increased yielding and ultimate load capacity of the specimen have been obtained; however, the ductility has been reduced up to 13.87% with increasing the BFRP thickness. The result also shows that the specimen strengthened with prestressed BFRP has better ductility than the prestressed carbon FRP (CFRP)-strengthened specimen; however, the model strengthened with prestressed CFRP has shown higher load-carrying capacity. It is also noticed that a cohesive bond better suited the experimental specimen than the fixed interference of the concrete surface, and relative to the cohesive bond, the fixed interference has shown a 17.4% higher ultimate load carrying capacity. [ABSTRACT FROM AUTHOR]

Despite having many advantages, using rubber to produce reinforced concrete members like beams is still restricted. When there is more waste tire rubber in concrete structures, rubber concrete's flexural and compressive strengths gradually decrease. However, this study used steel fibers to improve compressive strength and externally bonded carbon fiber-reinforced polymer (CFRP) sheets to increase flexural strength. Four groups of three reinforced concrete beams each were established for the study's use. The first and third groups of concrete beams used a volumetric replacement of fine and coarse aggregates with 5% and 10% waste tire rubber. However, steel fibers were added to the second and third groups at a rate of 1.25% of the concrete volume. Waste tire rubber and steel fibers were not replaced or added to the fourth group, the main reference group. The dimensions of each beam were 2.1×0.2×0.3 m. A concrete beam's first member is always free of external reinforcement, followed by its second member, which has one layer, and its third member, which has two layers of CFRP sheet. ABAQUS, a finite element analysis program, was used numerically to represent the third strengthening layer. The results showed that strengthening the reinforced rubberized concrete beams with a single layer of CFRP sheets increased the load at first crack and failure by 8.57% and 17.64%, respectively, compared to the unreinforced reference beam, compensating for the loss caused by the production of rubberized concrete and adding additional flexural strength. These loads increased by 31.43% and 26.45%, respectively, due to the steel fibers added to the beams containing these waste tire rubber. Strengthening with two layers of CFRP sheets increased the load at first crack and failure by 17.14 and 34.27, respectively. The steel fibers added to the beams that contained these amounts of waste tire rubber, on the other hand, caused these loads to increase by 42.86 and 49.23%, respectively. Strengthening with three layers numerically results in an exponential increase in load at the first crack and the failure by 8.03 and 52.88%, respectively. On the other hand, the loads on the beams that contained these quantities of waste tire rubber increased by 50.49% and 104.47%, respectively, when steel fibers were added to them. [ABSTRACT FROM AUTHOR]

In this study, an experimental program was developed to investigate the flexural behavior of pre-damaged reinforced concrete (RC) beams that had been repaired and strengthened using carbon fiber-reinforced polymer (CFRP) laminates under a monotonic load. Two techniques were used: externally bonded reinforcement (EBR) and near-surface-mounted (NSM) reinforcement, to repair and strengthen the tested beams. The experimental program involved casting and testing nine simply supported RC rectangular beams; one beam was considered as the reference beam and did not undergo additional strengthening, and the remaining beams were strengthened using CFRP laminates. These eight beams were divided into two main groups for the purposes of strengthening: beams for which the EBR technique was used, and beams for which the NSM technique was used. The primary variables observed in the EBR and NSM groups included four damage percentages obtained according to the preload (20, 40, 60, and 80%) from the ultimate load carried by the reference beam. The experimental results show that decreasing the damage percentage leads to an increase in ultimate strength from about 3.6% to 17.2% for the beams repaired using the EBR technique and from 27.6% to 57% for the beams repaired using the NSM technique; additionally, the NSM method was more effective than the EBR method in terms of the flexural strength and mode of failure. However, using CFRP laminates enhances the flexure capacity of strengthened RC beams. [ABSTRACT FROM AUTHOR]

This study aimed to assess the feasibility of utilizing geopolymer for repairing reinforced concrete beams. Three types of beam specimens were fabricated: benchmark specimens without any grooves, rectangular-grooved beams, and square-grooved beams. The repair materials employed included geopolymer material, and epoxy resin mortar, while carbon fiber sheets were used as reinforcement in select cases. The repair materials were applied to the rectangular and square-grooved specimens, with the carbon fiber sheets attached to the tension side of the specimens. To evaluate the flexural strength of the concrete specimens, a third-point loading test was conducted. The test results indicated that the geopolymer exhibited higher compressive strength and shrinkage rate compared to the epoxy resin mortar. Furthermore, the specimens reinforced with carbon fiber sheets demonstrated even greater strength than the benchmark specimens. In terms of flexural strength under cyclic third-point loading tests, the carbon fiber-reinforced specimens exhibited the ability to withstand over 200 cycles of repeated loading at 0.8 times the ultimate load. In contrast, the benchmark specimens could only withstand seven cycles. These findings highlight that the use of carbon fiber sheets not only enhances compressive strength but also improves resistance to cyclic loading. [ABSTRACT FROM AUTHOR]

The present study investigates the flexural behavior of reinforced concrete (RC) beams; the longitudinal reinforcing rebars of the beams were corroded and then strengthened with carbon fiber-reinforced polymer (CFRP). The corrosion of the longitudinal tension reinforcing rebars in eleven beam specimens was accelerated in order to obtain different corrosion levels. Afterwards, the beam specimens were strengthened by bonding one layer of CFRP sheets to the tension side to restore the strength loss due to the corrosion. The failure modes, flexural capacity, and midspan deflection of the specimens with different corrosion levels of the longitudinal tension reinforcing rebars were obtained by the four-point bending test. It was found that the flexural capacity of the beam specimens decreased with the increase in the corrosion level of the longitudinal tension reinforcing rebars and that the relative flexural strength was only 52.5% when the corrosion level was 25.6%. The stiffness of the beam specimens decreased significantly when the corrosion level was higher than 20%. Through a regression analysis of the test results, a model for the flexural bearing capacity of the corroded RC beams strengthened with CFRP was proposed in the study. [ABSTRACT FROM AUTHOR]

This paper is an experimental study of the effectiveness of using internal and external alkali-resistant glass fabric textile (AR-GT) layers for flexural strengthening of reinforced concrete (RC) beams. The experimental work compares internal single and triple layers of AR-GT as supplemental flexural reinforcement with textile-reinforced mortar (TRM) in RC beams subjected to four-point bending loading. In addition, a control beam specimen is cast with no AR-GT fabric. Monitoring the load–deflection curves, crack patterns, and strengthening layer performance showed that using AR-GT for internal and external layers increased the load-carrying capacity of RC beams. The failure patterns of beams with one external AR-GT layer and three internal AR-GT layers showed a similar trend, with higher loading capacity and lower deflections than the other beams. Three internal textile AR-GT layers recorded higher flexural strength (52%) than one internal layer (6.3%), compared to the control beam specimen. Moreover, using one layer of external AR-GT fabric exhibited higher flexural strength than using one or three internal layers (56.8%). [ABSTRACT FROM AUTHOR]

In this study, the efficacy of strengthening of reinforced concrete (RC) beams in shear by utilizing high-performance fiber-reinforced concrete (HPFRC) was explored. The shear strengthening was achieved by epoxy bonding of prefabricated HPFRC strips or plates onto the beams. The beams were strengthened utilizing two different strengthening schemes: (i) plates side strengthening (ii) vertical strips applied at shear critical sections. The behavior of the two configurations was compared to the behavior of non-shear reinforced and shear-reinforced RC beams. The high-performance concrete (HPC) utilized contains 1.5% of steel fibers per volume of HPC mortar and is known as HPFRC. Parameters determined were the flexural strength and compressive strength of HPFRC mortar. The obtained results revealed that HPFRC realized a 28-day flexural strength of 20 MPa and a compressive strength of 108 MPa. Moreover, HPFRC strengthened RC beams experienced an increased in strength capacity of about 50% for plates and 36% for vertical strips compared to the RC beams with no stirrups. The results for HPFRC strengthened beams with plates were superior compared to those of the stirrup-reinforced beams, whereas the results of HPFRC strips strengthened beams were almost identical to the stirrup-reinforced beams. Also observed, was an improvement in the ductility of the beams with the best results achieved when employing HPFRC plates and strips. Highlights: Shear Strengthening of RC beams by HPFRC plates utilizing two methods. Precast HPFRC plates bonded by epoxy adhesive and anchored. Continuous shear strengthening resulted in high-capacity enhancement and ductility. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) structures can experience damage due to material degradation, overloading, and other circumstances. Damage can take the form of spalling and delamination. One of the straightforward techniques to repair those localized damages is patching. Several types of materials can be used as patching material, one of which is Unsaturated Polyester Mortar (UPR)-Mortar. The UPR-mortar possesses low elastic modulus, high early strength, and adequate bond strength. However, only a few studies investigate the efficacy of employing the UPR-mortar patching to rehabilitate reinforced concrete structures. The current study uses experimental and numerical methods to examine how patching with UPR-mortar affects the flexural performance of reinforced concrete beams. Loading tests on RC beams with and without patching repair were carried out in the laboratory. During the loading test, the load and midspan deflection, strain development of the flexural reinforcements, and flexure crack evolution were monitored. Numerical simulations were also performed to validate the experimental results and further investigate the beam behavior with varying patching lengths. The results indicate that the remediation of RC beam with UPR-mortar patching can restore and boost flexural strength. Furthermore, when the patching length exceeds the maximum beam moment zone's length, the beam's flexural capacity increase becomes more apparent. [ABSTRACT FROM AUTHOR]

Four‐point bending tests were conducted to investigate the flexural properties of fly‐ash‐based geopolymer concrete beams. Although geopolymer concrete has a stress–strain relationship with brittle compressive softening behavior, it can be used as a flexural member because it exhibits ductile bending moment–deflection relationships when used with compression reinforcing bars and transverse reinforcement. The test results revealed that the conventional design method can be used to estimate the bending moment–deflection relationship of geopolymer concrete beams. However, the stiffness reduction ratio for yielding must be modified to consider the difference in the modulus of elasticity between geopolymer concrete and ordinary Portland cement concrete. [ABSTRACT FROM AUTHOR]

The significant CO2 emissions that can be associated with cement manufacture is the primary cause of global warming. Thus, the authors and research groups are motivated by many factors to find long-term solutions to this problem. Geopolymer concrete is such type of concrete in which the primary binder is resulted from alkali activation of some source materials like fly ash, metakaoline, rice husk ash, and ground granulated blast furnace slag. Commonly, geopolymer concrete gives comparable mechanical strength properties to conventional concrete. The use of this type of concrete is restricted by the properties of the used source materials and the molar concentrations of the alkali activator. As a consequence, making investigations to the relevant structural behavior as a result of these variables are rich sources of scientific research. The goal of this work is to provide a brief overview to the recent contributions that have dealt with the structural behavior of geopolymer concrete. The context of this paper was obtained to illustrate the main findings as well as the used source materials and some additional considerations. [ABSTRACT FROM AUTHOR]

This paper describes a study on finite element modeling (FEM) carried out on the ABAQUS platform for the prediction of flexural strength of corrosion-damaged reinforced concrete (RC) beams strengthened using layers of ultra-high-performance concrete (UHPC). Considering different combinations of the degree of reinforcement corrosion and thickness and configuration of UHPC layers, a total of twenty-two corroded, un-strengthened, and strengthened RC beam specimens were tested to record their flexural behavior. Following the flexural testing, the FEM was carried out considering the degradation in the diameter and the yielding strength of the corroded reinforcing bars. The cohesive surface bonding approach was used to simulate the interfacial bond stress slip between the corroded bars and surrounding concrete. The results of the FEM were validated using the experimental test results of the respective beam specimens. The FEM results (including crack pattern, flexural strength, stiffness, and linear and nonlinear behavior of the strengthened RC beams) were found to be in close agreement with the corresponding experimental test results. This indicates that the proposed FEMs can capture the flexural behavior of the corroded RC beams strengthened using layers of UHPC with high accuracy. Furthermore, a parametric study was carried out using the validated FEMs to investigate the effects of varying the compressive strength and thickness of UHPC layers on the flexural strength of the corroded strengthened RC beams. [ABSTRACT FROM AUTHOR]

Textile-reinforced mortar (TRM) is used to strengthen reinforced concrete (RC) structures using a textile and inorganic matrix. TRM is a part of textile-based composites; the basic structural behaviors, application methods, and methodologies for the extension of actual structures in TRM were studied. However, structural behavior and performance verification which depict the long-term service situation and fatigue is limited. Therefore, this study, verified the flexural behavior of TRM-strengthened beams and their fatigue performances using carbon- and alkali-resistant (AR) glass textiles through 200,000 load cycles. TRM-strengthened beams were applied to an optimization strengthening method which consisted of whether the textile was straightened. According to the test results, the strengthening efficiency of TRM-strengthened beams when subjected to cyclic loading was lower than that of the monotonic loading, except for the straightened carbon textile specimen. The average efficiency of the AR-glass textile (straightened and non-straightened) and carbon (non-straightened) was 0.86 compared to the TRM-strengthened beam subjected to monotonic loading in terms of flexural strength. In the case of deflection, the average efficiency of the AR-glass textile type was similar to the monotonic loading test results, while that of the non-straightened carbon textile was improved. The Ca-S specimen that was used to straighten the carbon textile showed a reliable structural performance with a strength efficiency of 0.99 and a deflection efficiency of 0.97 compared to the monotonic load test. Therefore, TRM strengthening using a straightened carbon textile is expected to be sufficient for the fatigue design of TRM-strengthened beams. [ABSTRACT FROM AUTHOR]

To explore the effect of adding bamboo fiber and steel wire mesh to BFRP bar-reinforced concrete beams on their flexural performance, we designed and fabricated six test beams with different parameters. Through flexural tests and numerical simulations, the effects of bamboo fiber length and steel wire mesh layout on the crack resistance, deformation capacity, and flexural ultimate bearing capacity of BFRP bar concrete beams were assessed. The feasibility of the simulation and the calculation method of flexural capacity of such specimens were considered. The research results showed that the addition of bamboo fiber can increase the cracking load and global stiffness and reduce the deformation of the test beam, but this had little effect on the ultimate flexural bearing capacity of the test beam. The cracking load, global stiffness, and ultimate flexural bearing capacity of the test beams were improved by the addition of steel wire mesh, and the stiffness and ultimate flexural bearing capacity of the test specimens with steel wire mesh in the whole beam were improved. Although the composite effect of bamboo fiber and steel wire mesh showed some improvement in these indicators, the improvement effect was not ideal. [ABSTRACT FROM AUTHOR]

The American Concrete Institute (ACI) developed ACI-318 and ACI-440 codes, providing design guidelines for concrete beams subject to flexure and reinforced with steel or Fiber-Reinforced Polymer (FRP) bars, respectively. Although using a hybrid reinforcing system that combines steel bars and FRP bars has gained significant attention, ACI codes have no design guidelines for this concept. The main objective of this study is to determine the appropriate strength reduction factor for hybrid steel/FRP RC beams (i.e., concrete beams reinforced with a hybrid system of FRP and steel bars) by conducting a comprehensive probabilistic analysis over a wide range of hybrid steel/FRP RC beams dataset. This factor is a crucial component of the design standards outlined by the American Concrete Institute (ACI). The reliability index of the beams dataset under consideration is determined within the framework of reliability analysis using the First Order Reliability Method (FORM). Furthermore, a sectional analysis is employed as a mechanical model initially verified using an experimental dataset of 95 specimens. This model is utilized to forecast the flexural capacity of beams. The study's findings indicate a substantial correlation between the strength reduction factor and the reinforcement and live-to-dead load ratios. For the objective of conservative design, a strength reduction factor of 0.65 is suggested. • Calibration of Strength reduction factor ϕ for Steel/FRP RC beams is performed. • ACI design rules are considered. • Calibration was performed over 77760 case including different design configurations. • Live/dead load and reinforcement ratios found to have significant effect the value of ϕ. • Global calibration results in ϕ of 0.75, and can be take 0.65 for conservative purpose. [ABSTRACT FROM AUTHOR]

Lightweight aggregate concrete (LWC) and fiber reinforced polymer (FRP) reinforcement are potentially more sustainable alternatives to traditional steel-reinforced concrete structures, offering several important benefits. To further the knowledge in this area, the physical–mechanical properties of LWC produced with 0%, 50%, and 100% expanded clay aggregate were assessed. Subsequently, the flexural behavior of LWC beams reinforced with steel reinforcement and glass and basalt FRP bars was tested. The results of the experimental program allowed quantifying of the effect of expanded clay aggregate incorporation on LWC properties. The use of FRP reinforcement was also compared to steel-reinforced concrete beam behavior. The results of this study can provide additional support for the use of innovative materials such as LWA and FRP reinforcement. [ABSTRACT FROM AUTHOR]

In this paper, the structural performance of lap-spliced beams were investigated by the testing of 18-UHPFRC beams with and without a lap-spliced region and steel fiber. All test specimens were subjected to flexural load by using the four-point bending test. It was shown that test steel fiber inclusion in the ultra-high-strength matrix significantly increased the strength of the lap-spliced beams. The maximum strength of the specimen increased linearly with the increase in steel fiber volume fraction. The hybrid-type UHPFRC, with lower steel fiber volume fraction, using two types of steel fiber was effective in improving the bond strength. In order to verify the safety of lap splice length design methods by current code provisions and UHPFRC design recommendations, the average bond stress at the ultimate state was used to calculate the lap splice length, which makes reinforcement yielding, and this value, compared with design lap splice length. Most of the design equations were under the estimated bond stress of UHPFRC. However, the AFGC recommendation, which considers the tensile strength of UHPFRC, overestimates the bond stress of UHPFRC because this recommendation was developed from the direct pull-out test results. [ABSTRACT FROM AUTHOR]

Due to rise in infrastructure development and demand for seawater and sea sand concrete, fiber-reinforced polymer (FRP) rebars are widely used in the construction industry. Flexural strength is an important component of reinforced concrete structural design. Therefore, this research focuses on estimating the flexural capacity of FRP-reinforced concrete beams using novel artificial intelligence (AI) decision tree (DT) and gradient boosting tree (GBT) approaches. For this purpose, six input parameters, namely the area of bottom flexural reinforcement, depth of the beam, width of the beam, concrete compressive strength, the elastic modulus of FRP rebar, and the tensile strength of rebar at failure, are considered to predict the moment bearing capacity of the beam under bending loads. The models were trained using 60% of the database and were validated first-hand on the remaining 40% database employing the correlation coefficient (R), error indices namely, mean absolute error, root mean square error (MAE, RMSE) and slope of the regression line between observed and predicted results. The developed models were further validated using sensitivity and parametric analysis. Both models revealed comparable performance; however, based on the comparison of the slope of the validation data (0.83 for GBT model against 0.75 for the DT model) and higher R for the validation phase in case of the GBT model in comparison to the DT, the GBT model can be considered more accurate and robust. The sensitivity analysis yielded depth of the beam as the most influential parameter in contributing flexural strength of the beam, followed by the area of flexural reinforcement. The developed GBT model surpasses the existing gene expression programming (GEP) model in terms of accuracy; however, the current American Concrete Institute (ACI) model equations are more reliable than AI models in predicting the flexural strength of FRP-reinforced concrete beams. [ABSTRACT FROM AUTHOR]

To decarbonise the current construction sector and meet the global net-zero target, there is a pressing need to develop an environmentally friendly alternative to Portland cement concrete. Alkali activated and geopolymer concrete have much to offer in this regard. At present, however, there is limited study on the behaviours of alkali activated structural members, particularly on flexural members, which encompass most practical design situations. This paper presents a database of 37 tests on slender alkali activated and geopolymer concrete beams available in the literature, with the aim to investigate the flexural strengths of this alternative concrete when used as a structural member. In addition, the results of nonlinear finite element analyses on fourteen reinforced geopolymer concrete beams are presented to highlight key influencing factors governing the behaviour and failure of flexural members. Of particular interest is to study the influence of reinforcement ratio, compressive strength, and material brittleness on the overall strength and ductility. Overall, it is shown that the flexural response of geopolymer concrete beams under short-term loading is comparable to that of ordinary reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Numerous studies investigated the possibility of incorporating plastic wastes in concrete mixtures, thus contributing to efficient management and sustainable development of the construction industry. This paper investigates the possibility of reducing the water-to-cement ratio and/or incorporating steel fibers or polymeric latexes to mitigate the drop in structural properties of reinforced concrete (RC) beams containing polyethylene terephthalate (PET) additions. The PET was derived from waste plastic bottles that were shredded into small pieces and added during concrete batching at 1.5% to 4.5%, by total volume. Test results showed that the concrete plain and structural properties degrade with PET additions, given their lightweight nature and poor characteristic strength compared to aggregate particles. The reduction of w/c from 0.55 to 0.46 proved efficient to refine the matrix porosity and reinstate the shear and flexural strengths of RC beams. Moreso, the incorporation of 0.8% steel fibers (by volume) or 15% styrene-butadiene rubber latexes (by mixing water) were efficient to enhance the bridging phenomenon and reduce the propagation of cracks during beam testing. [ABSTRACT FROM AUTHOR]

This study aims to establish a complete theoretical model for the nominal flexural strength of concrete beams reinforced with steel-fiber composite bars (SFCB-RC), and determine an optimized range for the ratio of the diameter of the steel core to the diameter of SFCBs (η). Firstly, flexural failure modes for SFCB-RC beams were determined through theoretical analysis, and two failure modes including concrete crushing (compression failure) and FRP in SFCBs rupturing (tension failure) were recommended. It was confirmed that there exists a transition region between the failure modes of tension and compression, where both modes are possible. By conducting a statistical analysis of a database including 57 SFCB-RC beams, an upper-limit reinforcement ratio was recommended for SFCB-RC beams in the transition region. Simplified equations to predict the nominal flexural strength for compression-controlled SFCB-RC beams were proposed by directly using the constitutive model of SFCBs. The flexural strength equations for tension-controlled concrete beams reinforced with fiber reinforced polymer bars (FRP-RC) were confirmed to be also suitable for SFCB-RC beams. Validation of these equations was conducted using the assembled database. Furthermore, the parametric analysis revealed an optimal range of the ratio η (0.77–0.87). This suggested range can serve as a basis for standardizing the production specifications of SFCBs. • Design methods and recommendations for flexural SFCB-RC beams were proposed. • The upper-limit reinforcement ratio of the transition region for flexural SFCB-RC beams was determined. • Simplified equations for predicting the nominal flexural strength of SFCB-RC beams were proposed. • An optimized range for the ratio of the steel core diameter to the SFCB diameter was determined. [ABSTRACT FROM AUTHOR]

In recent years, overlapping hoop, consisting of a U-shaped stirrup and a crosstie, has gained popularity because it could enhance construction efficiency of concrete composite beams. The U-shaped stirrups (U-shaped stirrup with 135°/180° hooks, namely A and S) and crossties (crosstie with 135° (90°)/90° hooks, namely J and C) are typical in the application. This study focused on four corresponding combinations of overlapping hoops, i.e., A+J, S+C, A+C and S+J. Ten full-scale concrete composite/monolithic beams were tested under cyclic loading, with parameters of the above four overlapping hoops and traditional enclosed hoop. The results revealed that all overlapping hoops had no fracture or early detachment prior to the peak load. The hysteresis curves of the four overlapping hoop composite beams were similar in full shape, demonstrating a good energy dissipation capacity. The four overlapping hoop composite beams had differences in flexural strength within 8% and 1% with the enclosed hoop composite beam and monolithic beam, respectively. The displacement ductility of the four overlapping hoop composite beams ranged from 6.1 to 6.8, while that of the enclosed hoop composite beam and monolithic beam was 7.3 and 6.3, respectively. Ten specimens exhibited similar stiffness degradation laws, and their three-linear restoring force models were proposed. Overall, the concrete composite beams reinforced with the four different overlapping hoops demonstrated similar seismic performance to that of the two enclosed hoop concrete beams. Considering the integrity and workability, the overlapping hoop A+C, consisting of a U-shaped stirrup (two 135° hooks) and a crosstie (two 90° hooks), would be the preferred combination. • Cycle test results on ten full-scale concrete composite/monolithic beams reinforced with overlapping hoops are presented. • The property of four types of overlapping hoops is studied and the preferred combination of overlapping hoops is proposed. • The effect of hooks on the integrity property of hoops is discussed. • The difference in seismic performance between concrete composite/monolithic beams with overlapping hoops is investigated. [ABSTRACT FROM AUTHOR]

• EBROG technique efficiently improved bond and flexural capacity of the RC specimens, in comparison with EBR. The distribution of grooves affected the load capacity. • A numerical model was developed to simulate Intermediate Crack Debonding (ICD) in beams for various bond-slip laws, applicable to the different strengthening techniques. • ICD failure load in RC beams strengthened with EBROG CFRP laminates was accurately predicted using the proposed model. This paper presents a study on the flexural capacity of Reinforced Concrete (RC) beams strengthened with Externally Bonded Reinforcement on Grooves (EBROG) Carbon Fibre Reinforced Polymer (CFRP) laminates. Thirteen single-shear tests and seven RC beams strengthened with CFRP are examined, comparing Externally Bonded Reinforcement (EBR) and EBROG techniques with different groove distributions. The results showed that EBROG improved the bond and flexural performance. Comparison with existing prediction models reveals that while the literature models accurately predict EBR results, they underestimated the bending capacity for EBROG due to calibration based on EBR bond parameters. Consequently, a numerical model is developed to simulate Intermediate Crack Debonding (ICD) for various bond-slip laws, applicable to the different strengthening techniques. The proposed model is validated using experimental flexural tests and calibrated bond-slip laws obtained from single-shear tests, demonstrating accurate prediction of ICD failure for both EBR and EBROG. [ABSTRACT FROM AUTHOR]

This paper investigates the potential improvement in the flexural strength of reinforced concrete beams when plain concrete is partially replaced by Hooked-Steel Fiber Concrete (HSFC). The main parameters considered in the experimental work were the height (hf) of the HSFC layer and the volume fraction (Vf) of the steel fiber used to create the HSFC layer. The volume fractions (Vf) of steel fiber used ranged from 0.5% to 1.5% with a 0.5% increment. For each steel fiber fraction, the height of the HSFC layer was varied as 20, 40, 60 and 100% of the overall depth of the section. In addition to the control reinforced concrete beam (hf = 0.0h and Vf = 0.0%), twelve hybrid beams were cast and tested using a fourth-point bending mode. Three distinct loading states were considered in this study: cracking, yielding and ultimate loads. Additionally, the effect of the material's hybridization on ductility, cracking stiffness, toughness and cracking behavior is discussed. The test results showed that partial replacement of plain concrete with HSFC of hf = 0.6h has approximately the same effect on the load-carrying capacity of the tested beams as compared to the full replacement (hf = 1.0h). In addition, the fiber content of 1.5% showed better results as compared to the lower contents of 0.5% and 1.0%.. [ABSTRACT FROM AUTHOR]

The conventional reinforced concrete is the most used building material in worldwide, concrete characteristics are brittle failure mechanism in tension, it essential to be improved. In concrete mix short descrete steel fibers to be added to recover its brittleness. in this project the optimum percentage of steel fibers are added, then we investigate the flexural behaviour of RC beam. In this project the hooked end steel fibers of 0.75mm Dia and 50mm length are added in reinforced concrete beam with concrete compressive strength of 30MPa (M30). The optimum percentage of steel fibers added to concrete mix, 15 cubes, 15 cylinders, 15 beams with 5 different percentages (i.e 0%, 0.75%, 1%, 1.25%, 1.5%) have been tested. The dimension of beam is 700mm x 150mm x 150mm. in this study flexural behaviour of steel fiber added reinforced concrete beams compared to normal (or) conventional reinforced beam with no steel fibers, the steel fiber reinforced beams were tested under flexure using a third-point loading test setup for M30 concrete. [ABSTRACT FROM AUTHOR]

The most widely used material after water is the concrete composite. However, it is commonly accepted that concrete is weak in tension compared to its compression, therefore, conventionally, it is usually reinforced with steel rebars. Recently, reusing of waste plastic materials has become a norm among researchers whom used it in different forms in improving some mechanical properties of the concrete such as impact and tensile strength. However, using PET plastic strips as a replacement of main steel rebars is a novel idea. Therefore, in this study the experimental laboratory work is conducted to investigate the possibility of using waste plastic strips as a replacement of the main reinforcement steel bars to promote the flexural capacity of concrete beams at 28 days. For this purpose, a total number of 10 beams were casted with dimensions of (200mm x 200mm x 1200mm) to investigate the effects of using waste plastic strips in enhancing the bending capacity of the beams. The results showed that the incorporation of the plastic strips can improve the load carrying capacity and toughness of the concrete beams compared to unreinforced concrete beams. [ABSTRACT FROM AUTHOR]

The use of reinforced fibre polymers to strengthen and repair structural elements is widely spreading. However, there is lack of knowledge of the actual behavior of strengthened structures with FRP sheets. This paper discusses the experimental results of the flexural strengthening of reinforced concrete (RC) beams by carbon fibre-reinforced polymer (CFRP) sheets bonded by epoxy adhesive to the tensile surface of the beams. Using a four-point bending load system over an effective span of 1800 mm, a total of ten beams with an overall dimension of 150 mm * 200 mm * 2000 mm with different degrees of strengthening schemes were tested. The number of layers, strengthening scheme (side and U-shape bonding) and reinforcement ratio are the major parameters of the experimental study. The research indicates that the flexural strength of the beams was substantially improved as the layers of laminate increased (between 31.80 and 71.50 %) and using U shape in ends that delay or prevent debonding failure. The experimental results compared to that analytically obtained by using ANSYS model showing acceptable agreement with deviations varying no more than 10 % for all specimens. [ABSTRACT FROM AUTHOR]

Copyright of Tikrit Journal of Engineering Sciences is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In this study, we conducted experimental tests on two specimens of reinforced concrete beams using a three-point bending test to optimize the flexure and stiffness designs. The first specimen is a reinforced concrete beam with an ordinary reinforcement, and the second specimen has an invented reinforcement system that consists of an ordinary reinforcement in addition to three additional bracings using steel bars and steel plates. The results of the flexure test were collected and analyzed, and the flexural strength, the rate of damage during bending, and the stiffness were determined. Finite element modeling was applied for both specimens using the LS-DYNA program, and the simulation results of the flexure test for the same outputs were determined. The results of the experimental tests showed that the flexural strength of the invented reinforcement system was significantly enhanced by 15.5% compared to the ordinary system. Moreover, the flexural cracks decreased to a significant extent, manifesting extremely small and narrow cracks in the flexure spread along the bottom face of the concrete. In addition, the maximum deflection for the invented reinforced concrete beam decreased to 1/3 compared to that of an ordinary reinforced concrete beam. The results were verified through numerical simulations, which demonstrated excellent similarities between the flexural failure and the stiffness of the beam. The invented reinforcement system exhibited a high capability in boosting the flexure design and stiffness. [ABSTRACT FROM AUTHOR]

The effect of the sulphate attack on reinforced concrete structures in Lagos lagoon environment has become a concern for stakeholders in the construction industry. This study investigated the flexural strength and microstructure of reinforced concrete beams for a period of 365 days. Thirty beams with dimension 150 mm £ 150 mm £ 600 mm were cast using grade 30 concrete with water cement ratio of 0.45 and cured for 28, 90 and 365 days, in both lagoon and fresh water. Flexural strength and microstructural test were carried out. The result showed that the flexural strength of concrete submerged in fresh and lagoon water were 24.6 and 20.3 N/mm2 respectively. The microstructure also confirmed the fact that specimens submerged in the lagoon had more defects and deterioration than the sample cured in fresh water at 365 days. [ABSTRACT FROM AUTHOR]

This paper presents the flexural capacity of reinforced concrete beams designed with highstrength steel bars. Reinforced concrete beams with steel bars fy = 550 MPa are designed to have flexural strength like beams with steel bar fy 420 MPa. According to ACI 318M-19, the high-strength steel bars (fy = 550 MPa) are allowed to use as the reinforcing steel, which previously unpermitted. This study was conducted to represent the possibility of using high-strength steel bars as reinforcement. There are five sample beams that design with various diameters (13 and 19 mm) and strength (fy 420 and 550 MPa) of longitudinal reinforcement. These beams were placed on two simple supported and undergo monotonic loads at two points-load. It is reviewed the flexural capacity of beams with high-strength steel bars involve load capacity, moment, and beam deflection. Also, the behavior of beams when receiving loads in terms of the relationship between load and deflection. Based on the research, beams with a high-strength steel bar can accept higher loads than normal beams by a difference of about 16-18%. While at the same deflection condition, which is 100 mm, beams with high strength reinforcement can achieve a higher load of around 18 percent. Beam with high-strength steel bars showed flexural behavior that was not much different from the normal-strength steel bars because it did not show brittle collapse. It proves that high-strength steel bars can be used on reinforced concrete structural elements if it satisfies the requirements specified in the code. [ABSTRACT FROM AUTHOR]

The construction industry faces various challenges, e.g. reducing its carbon footprint and the extensive use of materials. Therefore, Computational Design and Additive Manufacturing gain more importance throughout the industry. In combination, they offer the possibility of manufacturing individually designed building components, which can be less material-consuming and structurally improved. The presented research displays and discusses the effect of force-flow-oriented reinforcement design in concrete beams concerning the flexural strength and the required amount of steel. For this purpose, different reinforcement layouts were designed and integrated into conventionally cast and additively manufactured beam components. For the design of the force-flow-oriented reinforcement layouts, a digital workflow is established, and FEM simulations are utilised. The load-bearing capacity of the beams is compared based on four-point bending tests. Due to the optimised reinforcement layout, an increase of flexural strength of more than 60% was achieved while keeping the reinforcement amount constant. It is also shown that using force-flow-oriented reinforcement layouts can save nearly 60% of the reinforcement needed to achieve the same flexural strength as a beam with a conventional reinforcement cage. Finally, the potential for automated force-flow-oriented reinforcement integration within additively manufactured components is discussed. • Simulation-based approach for force-flow-oriented reinforcement layouts in concrete elements. • Experimental validation with cast and Shotcrete 3D printed beams. • Force-flow-oriented layouts can increase flexural strength by 60% for same reinforcement content. • Rebar content can be reduced by around 60% keeping similar load-bearing capacity. • Conceptual ideas for automated production of material efficient concrete components. [ABSTRACT FROM AUTHOR]

• For the specimens using D20 GFRP bars, the retrofit method of CE was sufficient to restore the bond strength. • For the specimens using D28 GFRP bars, the retrofit methods of U and CU were effective in restoring the bond strength. • The predictions of flexural strength and effective moment of inertia of retrofitted specimens were proposed addressing the pre-damage effect. Fiber-reinforced polymer (FRP) reinforced concrete structures are inevitably subjected to extreme loads. The retrofitting of damaged FRP-reinforced concrete structures will become an important issue, especially with the gradual application of FRP bars in concrete structures. For structures that can be retrofitted, the structural performance is significantly affected by the bond of FRP bars in pre-damaged concrete. For this reason, this paper investigated the effectiveness of retrofit methods of carbon FRP (CFRP) sheet and/or ultra-high performance concrete (UHPC) at restoring the bond strength of glass FRP (GFRP) bars in pre-damaged concrete, and twenty spliced GFRP-reinforced concrete beams were tested under four-point loading. The beams were pre-loaded until bond failure occurred, and then retrofitted and reloaded to assess the restoration of the bond strength. The effects of retrofit methods, spacing of confining stirrups, GFRP bar diameter, and pre-loading type were investigated. The bond strength of the 20 mm and 28 mm diameter GFRP bars was increased by 4~138% and 4~234% after retrofitting with CFRP sheet and/or UHPC, respectively. The modified flexural strength model and modified effective moment of inertia addressing the adverse effect of partial fracture of glass fibers and concrete cracks predicted well the load-carrying capacity and deflection of the retrofitted specimens showing flexural failure, respectively. [ABSTRACT FROM AUTHOR]

In this study, a total of 177 flexural experimental tests of corroded reinforced concrete (CRC) beams were collected from the published literature. The database of flexural capacity of CRC beam was established by using unified and standardized experimental data. Through this database, the effects of various parameters on the flexural capacity of CRC beams were discussed, including beam width, the effective height of beam section, ratio of strength between longitudinal reinforcement and concrete, concrete compressive strength, and longitudinal reinforcement corrosion ratio. The results indicate that the corrosion of longitudinal reinforcement has the greatest effect on the residual flexural capacity of CRC beams, while other parameters have much less effect. In addition, six available empirical models for calculating the residual flexural strength of CRC beams were also collected and compared with each other based on the established database. It indicates that though five of six existing empirical models underestimate the flexural capacity of CRC beams, there is one model overestimating the flexural capacity. Finally, a newly developed empirical model is proposed to provide accurate and effective predictions in a large range of corrosion ratio for safety assessment of flexural failure of CRC beams confirmed by the comparisons. [ABSTRACT FROM AUTHOR]

The structural behavior of concrete beams containing recycled coarse aggregates (RCAs) was investigated in this study using detailed experimental data. Twelve concrete beams were tested in the experimental program: nine beams with varying RCA contents and three control beams with natural coarse aggregates (NCAs). The parameters for investigating the structural behavior of the RCA concrete beams under flexure were the RCA content (30%, 50%, and 100%) and tensile rebar ratio (0.50%, 0.79%, and 1.14%). The crack pattern of the RCA beams was similar to that of the NCA beams; however, the RCA beams exhibited smaller crack spacing than the NCA beams. The flexural strength was slightly affected by the RCA content. However, the ductility of the beam was not significantly influenced by the RCA content. A comparison of the experimental results and the calculations from the ACI 318 and EC 2 provisions for the flexural strength showed that the current provisions conservatively predicted the flexural strength of the RCA concrete beams. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering (17264073) is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Several effective strengthening schemes for enhancing the flexural strength of heat-damaged reinforced concrete (RC), beams are proposed. A series of twenty-eight RC rectangular beams were cast, subject to a temperature of 600 °C for 3 h, strengthened, and then tested in flexure to determine the effect of externally applied carbon and glass fiber reinforced polymeric sheets (CFRP) and (GFRP) respectively, as a method for regaining the beams' flexural capacity. The load-deflection behavior and the modes of failure of the beams tested are described. The beams strengthened in shear and flexure with CFRP and GFRP sheets applied at the sides and the bottom of the beams in U-shaped jackets or strips showed a significant increase in their flexural strength compared to control and heat damaged ones. They achieved a high percentage of the control beams load carrying capacity, and exhibited a ductile failure characterized by the initiation of typical flexural cracks in the moment zone followed by the occurrence of flexure-shear cracks in the constant shear span. Optimizing the CFRP and GFRP strengthening schemes proposed could provide promising and cost effective repair alternatives for enhancing the flexural capacity of fire damaged RC members. [ABSTRACT FROM AUTHOR]

The use of kevlar fabric laminates in the structural repair and retrofitting of reinforced concrete members becomes a great deal of research work nowadays. Many research works have been done on the performance of Fibre-Reinforced Polymer (FRP) laminates on reinforced concrete structural members. Some studies have been done on the performance of kevlar fabric laminates on reinforced concrete structural members and only few contributions are available for self-compacting concrete structural members. Hence, in this research work, an attempt is made to study the performance of reinforced concrete and self-compacting beams laminated with various numbers of kevlar fabric layers by an epoxy bonding agent under a two-point concentrated loading system. The experimental data of ultimate load, mid-span deflection and mode of failure was collected and discussed. Theoretical and analytical studies were also conducted and compared with experimental results. When applying the kevlar fabric as an external reinforcement, the flexural strength of two-layer U-shape kevlar fabric-laminated beams has been increased by 88% and 82%, respectively, compared to unlaminated reinforced concrete and self-compacting beams. [ABSTRACT FROM AUTHOR]

A construction system with high sustainability, high durability, and appropriate strength can be supplied by geopolymer concrete (GPC) reinforced with glass fibre-reinforced polymer (GFRP) bars and carbon fibre-reinforced polymer (CFRP) bars. Few studies deal with a combination of GPC and FRP bars, especially CFRP bars. The present investigation presents the flexural capacity and behaviour of fly-ash-based GPC beam reinforced with two different types of FRP bars: six reinforced geopolymer concrete (RGPC) beams consisting of three specimens reinforced with GFRP bars and the rest with CFRP bars. The beams were tested under four-point bending with a clear span of 2000 mm. The test parameters included the longitudinal-reinforcement ratio and the longitudinal-reinforcement type, including GFRP and CFRP. Ultimate load, first crack load, load-deflection behaviour, load-strain curve, crack width, and the modes of failure were studied. The experimental results were compared with the equations recommended by ACI 440.1R-15 and CSA S806-12 for flexural strength and midspan deflection of the beams. The results show that the reinforcement ratio had a significant effect on the ultimate load capacity and failure mode. The ultimate load capacity of CFRP-RGPC beams was higher than that of GFRP-RGPC, more crack formations were observed in the CFRP-RGPC beams than in the GFRP-RGPC beams, and the crack width in the GFRP-RGPC beams was more extensive than that in the CFRP-RGPC beams. Beams with lower reinforcement ratios experienced a fewer number of crack and a higher value of crack width, while numerous cracks and less value of crack width were observed in beams with higher reinforcement ratio. Beams with the lower reinforcement ratios were more affected by the type of FRP bars, and the deflection in GFRP-RGPC beams was higher than that in CFRP-RGPC beams for the same corresponding load level. ACI 440.1R-15 and CSA S806-12 underestimated the flexural strength and midspan deflection of RGPC beams; however, CSA S806-12 predicted more accurately. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Engineering & Sustainable Development is the property of Republic of Iraq Ministry of Higher Education & Scientific Research (MOHESR) and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract This paper reports the effect of corroded tension reinforcements on the flexural behavior of reinforced recycled aggregate concrete (RRC) beams strengthened with carbon fiber-reinforced polymer (CFRP). Eight beams were subjected to accelerated corrosion for 2, 4, 6, 8, 10, 12, and 14 days to obtain the theoretical mass loss in their tension reinforcements of 1%, 3%, 5%, 7%, 9%, 11%, and 13%, respectively. The specimen beams were categorized into two groups (strengthened and unstrengthened). First, strengthened group included SB0–SB7.Seconded, unstrengthened group included B0 and B7. The results indicated that the flexural bearing capacity of the RRC beam decreased with increasing tension reinforcement corrosion level. The flexural bearing capacity of the RRC beams strengthened with CFRP improved more significantly. The CFRP strengthening effect of corroded RRC beams was more obvious than that of corroded RC beams under the same corrosion level. The specimens failed owing to tension reinforcements yielding, the compression concrete was crushed and subsequently the CFRP debonding the concrete. The corroded RRC beams, strengthened by adhering CFRP sheets, could restrict the development and extension of the cracks. [ABSTRACT FROM AUTHOR]