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

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

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. [ABSTRACT FROM AUTHOR]

This study examines the effect of Ground Granulated Blast Furnace Slag (GGBS) and steel fibers on the flexural behaviour of RC beams under monotonic loading. Various percentages of GGBS were used to substitute cement, namely 0%, 20%, 40%, 60%, and 80% and fibers were added to the concrete mix as 0%, 0.5%, 1%, and 1.5% of the volume of concrete. The load–deflection behaviour of GGBS-incorporated RC beams with fibers was compared with the control RC beam. Beams were tested under load control for 28 days and 180 days. The ultimate load of the GGBS-incorporated RC beam up to 40% cement replacement was found to higher than that of the control beam. The strength of concrete is reduced by 28% and 19% when cement was partially replaced by 80% of GGBS at 28 and 180 days, respectively, compared to control concrete without fibres. Further, the analytical load–deflection response of GGBS-incorporated RC beams was determined by using several codes of practice, namely, ACI 318-11(2011), CSA A23.3-04 (2004), EC-04 (2004), and IS 456 (2000). The Codal provisions were primarily based on the effective moment of inertia, Young's modulus, and modulus of rupture, stiffness, and cracking. Average load–deflection plots obtained from experiments were compared with the computed load–deflection of analytical studies. It was found that the analytically predicted load–deflection behaviour is comparable with the corresponding average experimental load–deflection response. Moment curvature relations were also developed for RC beams. [ABSTRACT FROM AUTHOR]

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]

Fibers are mixed within reinforced high‐strength recycled aggregate concrete (RHRAC) beams to improve their flexural performance. This study experimentally and analytically investigates the effect of using RAC combined with polyvinyl alcohol fiber (PVAF) and steel fiber (SF) on the flexural performance of RHRAC beams. A total of 11 RHRAC beams (150 × 300 × 2600 mm3) are manufactured and subject to four‐point flexural testing. The parameters of the concrete are investigated, including the volume content of the PVAF and SF. The experimental results show that SF increases the flexural strength of RHRAC beams more than PVAF does. Conversely, the effect of PVAF on deformability is more significant than that of SF. In addition, the positive influences of hybrid fiber (PVAF and SF) on the crack load, flexural capacity, and deformation capacity are superior to those of single‐mixed PVAF or SF. Three different specifications are used to calculate the flexural capacity of the test beams, among which, JGJ/T465‐2019 is the most reliable. [ABSTRACT FROM AUTHOR]

The present article is an effort to quantify the flexural strength of corroded reinforced concrete (RC) beams. Eight RC beams with dimensions of 150 × 200 × 2200 mm were tested in four-point bending, including six beams corroded in a chloride environment with average corrosion of longitudinal reinforcement in the range of 5% to 15%. The remaining two beams were used as control beams. The ultimate strength, failure mode and particularly the relationship between crack width and corrosion level are analyzed and discussed. A two-dimensional non-linear finite element model has been presented to simulate the steel bar corrosion considering the deterioration of concrete strength and steel-concrete bond stress. The generalised regression neural network (GRNN)-based model for the ultimate flexural strength of corroded RC beams has been established based on 123 experimental data collected from previous studies. The experimental results were used to separately validate the non-linear finite element model and novel GRNN model. Experimental results indicate that if the overall corrosion rate is used, the corrosion crack width can be a function of the percentage of section loss. The GRNN model provides superior predictive results compared to previous empirical methods with the highest correlation coefficient (r), and the smallest normalised root mean square error. [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]

Cement has historically been a major contributor to carbon dioxide emissions, and substituting cement in concrete with alternative cementitious materials will lead to a decrease in carbon footprints. A vast amount of literature focuses on the mechanical properties and performance of concrete partially replaced with different cementitious materials. However, the literature on the structural performance of concrete with different cementitious materials is very limited. Therefore, the main aim of the current experimental study is to evaluate the flexural and shear performance of reinforced concrete (RC) beams cast with various replacement percentages of ordinary Portland cement (OPC) with supplementary cementitious materials (SCM) such as ground granulated blast furnace slag (GGBS) and fly ash. A total of 33 RC beams were cast with 50% and 70% replacement of cement with GGBS and fly ash. In addition, the tensile and compressive strengths of the different mixes with GGBS and fly ash were also compared with the 100% OPC mix at 28 and 56 days. All beams were subjected to monotonic four-point bending tests and load-deflection response curves along with failure modes were presented. The experimental results showed that the average compressive and tensile strength of mixes with GGBS and fly ash replacement were comparable with OPC. The mixes with 50% replacement and higher usage of GGBS showed higher compressive strengths compared to mixes with 70% replacement. In addition, the flexural performance of beams with GGBS and fly ash were comparable to the specimen with 100% OPC. Even GGBS and fly ash replacement increased the stiffness and yield strength of the beam specimens by 36 and 16% compared to the control specimen. The specimens tested at 56 days with higher usage of fly ash and 50% replacement showed the highest flexural load as compared with other specimens. In the case of the shear specimens, the normalized ultimate shear capacity of RC beams is not significantly affected when OPC is replaced with 50% and 70% of GGBS and fly ash, respectively. Therefore, it can be concluded that the overall behavior of SCM beams was comparable to that of the control OPC beams. The ACI 318-19 design guidelines were also used to predict the flexural and shear capacity of RC beams cast with GGBS and fly ash. The aforementioned experiments indicate the viability and effectiveness of cement replacements in concrete with SCM, which in return, contribute to lower carbon footprints. [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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High-strength steel reinforcement offers promising application prospects in buildings with large spans and loads, as it can reduce steel congestion and simplify construction process. To investigate the mechanical behavior of flexural members reinforced with high-strength steel and measures to control crack width, in this study, static loading tests were conducted on 17 full-scale reinforced concrete (RC) beams with HRB635 high-strength steel reinforcement, six of which were reinforced with steel fiber. The failure mode, flexural strength, ductility, crack width, and deflection of the specimens were investigated, and the effects of different key parameters, including the reinforcement ratio and diameter, concrete strength, and steel fiber volume fraction were also analyzed. Test results indicated that the tensile strength of HRB635 reinforcement could be fully utilized, while the ductility ratios of high-strength steel reinforced concrete (HSS-RC) beams were less than those of beams with normal strength reinforcement. The maximum crack widths of most specimens without steel fibers exceeded the threshold defined in GB 50010-2010, indicating that the design of HSS-RC beams may be controlled by the requirements of serviceability limit state. Furthermore, the crack widths predicting methods defined in GB 50010-2010 and EN 1992-1-1 are more accurate for HSS-RC beams, while the deflection predicting methods defined in GB 50010-2010 and ACI 318-19 both underestimated the deflection of HSS-RC beams. This study could provide a theoretical basis for the engineering application of HRB635 high-strength steel reinforcement. [ABSTRACT FROM AUTHOR]

The building and construction industry's demand for steel reinforcement bars has increased with the rapid growth and development in the world. However, steel production contributes to harmful waste and emissions that cause environmental pollution and climate change-related problems. In light of sustainable construction practices, bamboo, a readily accessible and eco-friendly building material, is suggested as a viable replacement for steel rebars. Its cost-effectiveness, environmental sustainability, and considerable tensile strength make it a promising option. In this research, hybrid beams underwent analysis through the use of thoroughly validated finite element models (FEMs), wherein the replacement of steel rebars with bamboo was explored as an alternative reinforcement material. The standard-size beams were subjected to three-point loading using FEMs to study parameters such as the load–deflection response, energy absorption, maximum capacity, and failure patterns. Then, gene expression programming was integrated to aid in developing a more straightforward equation for predicting the flexural strength of bamboo-reinforced concrete beams. The results of this study support the conclusion that the replacement of a portion of flexural steel with bamboo in reinforced concrete beams does not have a detrimental impact on the overall load-bearing capacity and energy absorption of the structure. Furthermore, it may offer a cost-effective and feasible alternative. [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]

This paper presents an experimental investigation on the static, microstructural and impact properties of concrete incorporating tire rubbers. Fine tire rubber (FR) and coarse tire rubber (CR) were used to replace fine and coarse aggregates, respectively, by 10 and 20% by volume. The single and combined effects of tire rubbers on the unit weight, mechanical properties (compressive strength, split tensile strength, flexural strength, and flexural toughness properties) and impact resistance of concrete were evaluated. Drop-weight test using concrete beams was conducted to evaluate the impact behavior of concrete. The microstructure of concrete was also investigated using SEM analysis. The results showed that incorporation of FR and CR reduced the unit weight, compressive strength, and flexural strength of concrete. Lower content of tire rubbers increased the split tensile strength of concrete, however higher content of tire rubbers resulted in its reduction. On the other hand, tire rubbers were found to remarkably enhance the energy absorption capacity, fracture energy and impact strength of concrete. SEM observations revealed that rubberized concretes had more porosity and weaker interfacial transition zone than normal concrete. In general, when FR and CR were used together, they showed an average static and impact performance compared to their single use. [ABSTRACT FROM AUTHOR]

This investigation was conducted to study the response of reinforced hybrid beams exposed to flames and their capacity for carrying loads. At the age of 28 days, concrete samples and beams were exposed to fire temperatures ranging from 25°C to 600°C. Then, the beams were gradually cooled by being left in the air. The testing samples were exposed to flames for a half hour at temperatures of 600°C. All ultrahigh-performance concrete (UHPC) specimens (cubic, cylinder, and prism), upon burning at 600°C, spalled and lost some of their mechanical characteristics. Results indicate a remarkable reduction in compressive strength; the residual compressive strength was 78% and 62% for conventional and ultrahigh-performance concrete, respectively. Therefore, the remaining tensile strength was 77% and 69% for normal concrete and UHPC, respectively, and the residual flexural strength was 41% and 64% for conventional concrete and UHPC, respectively. Four beams consisting of two kinds of concrete, normal concrete (NC) and UHPC, were subjected to flame, and another four reference beams with dimensions of 12 cm width, 15 cm depth, and 170 cm length were used in this study. The results showed that the effect of firing on the UHPC part was larger than on the normal concrete part, and that led to an effect on the beams' behavior and mode of failure. For reference beams, it can be seen the use of the UHPC layer at the compression zone played a major role by changing the mode of failure from compression (as in beam R1) to flexural failure (as in beams R2 and R3). However, after firing, the mode of failure returned to compression failure because the influence of firing on the UHPC part was greater than on the normal concrete part at 600°C. This study is considered important in buildings that must be highly durable and are likely to be exposed to fires. It is clear when using a layer of UHPC in the NC beam affected by fire that it is possible to benefit from this beam after removing the surface damaged by the fire and making repairs on the surface of the beam. [ABSTRACT FROM AUTHOR]

This study investigates the impact of varying glass fiber-reinforced polymer (GFRP) stirrup spacing on the performance of doubly GFRP-reinforced concrete beams. The research focuses on assessing the behavior of GFRP-reinforced concrete beams, including load-carrying capacity, cracking, and deformability. It explores the feasibility and effectiveness of GFRP bars as an alternative to traditional steel reinforcement in concrete structures. Six concrete beams with a cross-section of 300 mm (wide) × 250 mm (deep), simply supported on a 2100 mm span, were tested. The beams underwent four-point bending with two concentrated loads applied symmetrically at one-third of the span length, resulting in a shear span (a)- to-depth (h) ratio of 2.8. The experimental findings reveal that altering the GFRP stirrup spacing along the longitudinal axis of the beams, from 200 mm (equivalent to the effective depth (d)) to 50 mm (equal to (d⁄4)), altered the mode of failure from flexure-shear to flexure-compression. However, when the spacing was equal to or less than (d⁄3), there was no significant improvement in load-carrying capacity, as the contribution of GFRP bars in resisting shear loads was limited. Under service loads, the GFRP-reinforced beams exhibited wider cracks, but reducing the stirrup spacing helped restrain crack widening. Incorporating GFRP bars in the compression zone had a positive effect on reducing crack width in the tension zone. Additionally, using GFRP stirrups with spacing varying between (d) and (d⁄2) in the pure bending region increased the deflection ductility indexes. To enhance the ductility of GFRP-reinforced concrete beams, it is recommended to use GFRP stirrups in the pure bending region with spacing greater than the spacing between GFRP stirrups in the shear spans. The study highlights that the current ACI code overestimates the shear capacity provided by GFRP stirrups, particularly when the spacing is less than or equal to (d⁄3). [ABSTRACT FROM AUTHOR]

In search of sustainable development this study gives the vision of evolutionary growth in construction industry. As said by Buckminster Fuller "You never change things by fighting the reality. To change something, build a new model that makes the existing model obsolete. "The dream of having a house is a challenging task for low and moderate-income earners in developing countries. Low-cost housing techniques can be adapted to achieve an environmentally friendly and innovative construction to overcome the problem. The materials like Bamboo and Polypropylene band (PP) have been considered as sustainable building materials for the replacement of steel in this present research. Bamboo is a construction material that has been used for a long period for rural housing techniques. Many researchers have determined that bamboo has high tensile strength properties and is also easily available. It is possible to lower the cost of the construction by using bamboo as the main reinforcement. Polypropylene (PP) band, which is rarely used as a building material in India which is strong has heat resistance, and is lighter in weight. The main objective of this study includes that, strength parameters such as flexural strength, compressive strength of the reinforced concrete beam can be achieved by using bamboo as the main reinforcement and Polypropylene band as vertical stirrup that can reduce the cost by 85% and also helps to achieve lightweight structure. The establishment of stable analytical model proves to be cost effective by reducing the number of test specimens for experimental work. This research targets to compare experimental investigations with FEA approach. The Finite Element Analysis (FEA) is carried out using ABAQUS for model geometry to observe experimental study. MATLAB application has been used to validate the structural behaviour through parametric studies like shear force and bending moment diagram using 3-point loading beam. [ABSTRACT FROM AUTHOR]

This paper proposes an optimization study for both structure and materials to obtain an affordable, long-span, light-weight, and fast-constructing T-shape lightweight concrete-filled steel tubular (LWCFST) girder in order to be used in bridge construction. This research was performed on a hollow steel tube of Steel-52 (yield limit 360 MPa), which was filled with LWC. A set of parameters had been investigated to illustrate its effect on T-shape LWCFST girder stiffness, toughness, resilience, and ultimate carrying load capacity in order to obtain an equivalent stiffness to that of the typically used precast concrete girder. Based on design codes (EN 1994-1-1/Euro code 4 and ANSI/AISC 360-10) that permit the use of LWC as a filler material, the parameters considered were: the thickness of the steel tube, compressive strength of the filler concrete, and the bond condition between the steel tube and filler lightweight concrete. The yielding and ultimate bending capacity were determined based on the interpreted failure criteria of T-shape LWCFST girder, considering non-linear analysis for both material and loads using ANSYSWORKBENCH software. The results showed that T-shape LWCFST girder can be employed as a significant relative economic alternative to a typical precast girder in the bridge construction field, thanks to its high stiffness/weight ratio. The lightweight concrete inside was effectively employed to delay the local web buckling of the steel tube to increase its bending capacity. In addition, it reduced the total self-weight of the bridge's superstructure by 20% compared with a typical precast concrete girder. The dominant failure of T-shape LWCFST girders was found in the upper concrete slab due to the compression stress, even though the tensile cracks in the filler concrete occurred after reaching tensile yield stress in the steel tube. Additionally, increasing the value of friction coefficient between steel tube and lightweight concrete up to 0.8 was found to significantly affect the girder stiffness and has a slight effect after, no matter how high it is. [ABSTRACT FROM AUTHOR]

This study aims to investigate the flexural performance and design methods of flexural concrete beams reinforced with basalt fiber–reinforced polymer (BFRP) and steel bars. Eight concrete beams, which included six reinforced with a combination of BFRP and steel bars, one reinforced with only steel bars, and one reinforced with only BFRP bars, were constructed and then tested under four-point loading. For hybrid-reinforced concrete (RC) beams, two types of BFRP bars (ribbed and sand-coated) and different reinforcement ratios were considered. The test results are discussed in terms of the flexural capacity, reinforcement strain, deflection responses, and cracking behavior. Experimental results showed that the crack width of the hybrid-RC beam, obtained by adding BFRP bars in the concrete cover of the steel-RC beam, reduced by approximately 40% compared with that of the steel-RC beam, and the strength utilization of BFRP bars in hybrid-RC beams was higher than that in the BFRP-RC beam. Additionally, the cracking moment, nominal flexural strength, and midspan deflection of the hybrid-RC beams were predicted by using existing design models. The bond-dependent coefficients (kb) of the ribbed and sand-coated BFRP bars were assessed by using test data. [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]

Fiber reinforced polymer (FRP) bars have been widely used as a replacement for steel bars in civil engineering due to their high strength and superior durability. However, compared to steel reinforced concrete (RC) beams, FRP RC beams have insufficient ductility and are more expensive. Therefore, a hybrid beam reinforced with steel and FRP bars has been proposed recently. In this study, the flexural properties of steel bar RC beam, basalt FRP (BFRP) bar RC beam, and BFRP steel bars hybrid RC beams were studied based on numerical simulation. The effect of As/Af on the stress of longitudinal reinforcements, load–midspan curves, ductility, and overall performance of the hybrid RC beams is analyzed. Results indicated that the hybrid RC beams exhibited a second‐order stiffness after the steel bars yielded owing to the contribution of the BFRP bars. As As/Af increases, the ductility of the hybrid RC beam and the strength utilization of BFRP bars increase, and a preferable ductility and overall performance can be achieved when As/Af was close to 1.0. The theoretical calculation results of hybrid RC beams based on ACI, CSA, and GB codes are compared with the simulation results, and the accuracy of the ultimate flexural strength of the prediction results is verified. In addition, equations for predicting the deflection of hybrid RC beams are proposed, and they exhibit higher prediction accuracy compared to the prediction models based on the ACI code. [ABSTRACT FROM AUTHOR]

The study of damage processes in concrete and their effects on the residual properties represents a key point related to the service life of reinforced concrete (RC) structures. The use of steel fibers in RC beams mainly improves the cracking control and the shear bearing capacity. Considering the shear behavior, the presence of fibers not only leads to partial or total substitution of secondary reinforcement, but they can also result in a modification of the failure behavior from a shear failure (brittle) to a bending (ductile) one. The contribution of fibers on flexural and shear behavior of sound and damaged RC beams was investigated using alkali‐silica reaction as a damaging tool. First, the evolution of deformations and cracks were measured on creep tests of RC beams with and without fibers and reactive aggregates. Second, the flexural and shear behavior of damaged and undamaged beams incorporating steel fibers were compared. Results showed that alkali‐silica reaction damage can provoke a reduction of RC beam ductility, while the flexural strength is preserved. Regarding shear, it was observed that even in damaged concrete, fibers were able to control the crack propagation and increase the bearing capacity. [ABSTRACT FROM AUTHOR]

This study aims to develop a new hybrid strengthening approach for reinforced concrete beams by integrating near‐surface mounted shape memory alloys (SMAs) and externally bonded carbon fiber reinforced polymers (CFRPs). Due to the superelasticity and shape memory effect of SMAs, the proposed strengthening can enhance the flexural strength of concrete beams without compromising ductility. The recovery behavior of deformed SMA wires was studied to determine the optimal prestrain level that can achieve the highest recovery stress. Afterward, the flexural performance of concrete beams strengthened with SMA, CFRP and both was investigated by performing three‐point tests. The results show that integrating SMA and CFRP has more influence on increasing the ultimate moment than the cracking moment and leads to a more significant improvement in the ultimate moment than individually utilizing SMA and CFRP. Besides, the effect of the integrated approach on enhancing the ductility is more notable than increasing the ultimate moment. The ultimate moment was analytically calculated, and the calculations show reasonable agreement with experimental results. The effects of the SMA and CFRP amount on the ultimate moment were also clarified through a parametric study. [ABSTRACT FROM AUTHOR]

This article presents woven carbon-fiber-reinforced polymer (CFRP) tubular mesh used as a reinforcement on the inner surface of hollow beams made of high-performance concrete (HPC). The tubular mesh was designed to serve as both the tensile and shear reinforcement of hollow beams intended for the construction of small self-supporting structures that could be assembled without mechanization. The reinforcement was prepared with a tri-axial weaving machine from carbon filament yarn and was homogenized using epoxy resin. The interaction of the composite reinforcement with the cementitious matrix was investigated, and the surface of the reinforcement was modified using silica sand and polyvinyl alcohol (PVA) fibers to improve cohesion. The sand coating enhanced bond strength, resulting in the significantly higher flexural strength of the hollow beam of 128%. The PVA fibers had a lower positive effect of 64% on the flexural strength but improved the ductility of the beam. Individual beams were connected by gluing steel parts directly inside the hollow core of the HPC beam. This procedure provides good interaction between the CFRP reinforcement and the glued steel insert and allows for the fast and simple assembly of structures. The weaving of additional layers of the CFRP reinforcement around HPC beams was also explored. A small structure made of the hollow HPC beams with inner composite reinforcement was constructed to demonstrate the possibilities of the presented technology. [ABSTRACT FROM AUTHOR]

Research studies investigating the possibility of using 5 new core material (other than polystyrene) in concrete sandwich panels are being reported in the literature. Though several alternate core materials are suggested in the literature, not many would improve the fire-resistance property of the sandwich panels. Towards addressing this issue, in this paper, a lightweight pervious concrete core is proposed as a new alternative. Experimental studies were conducted to determine the flexural behavior of sandwich panels with pervious concrete core. The flexural behaviour was investigated under threepoint and four-point bending conditions. The geometrical variables considered were core thickness and a number of shear connector lines. The variables considered were found to influence the initial stiffness, cracking moment, ultimate moment, load-deflection behaviour and load-strain behaviour of the panels. Test results showed that, sandwich panels without shear connector trusses failed due to the separation of wythes, and the panels with shear connector trusses achieved composite action. An analytical study indicated that the equation given in ACI 318 underestimated the strength of the tested panels. The equation has to be modified by explicitly including the shear connector details in the equation for predicting the flexural strength with reasonable accuracy. Further experimental and analytical studies on prototype concrete sandwich panels with pervious concrete core produced using lightweight aggregates are required in view of developing design guidelines for practical applications. [ABSTRACT FROM AUTHOR]

The work presented here aims at investigating the feasibility of iron-based Fe-SMA (shape memory alloy) reinforcement as an alternative to conventional steel reinforcement. The conventional steel reinforcement shows large plastic strain, low resistance to corrosion, low resistance to fatigue and also inadequate recentering capability. As a result, advanced materials available in the form of superelastic (SE) shape memory alloy (SMA) are fabricated to form structural reinforcements. This FE-SMA mitigates the problem of long-lasting deflection by using its reversible stress-strain capability. This iron-based Fe-SMA may be stimulated between the temperatures of 90 to 150°C, with which it is possible to strengthen the reinforced concrete (RC) beams without any crucial damage. The stress-strain behavior in tension, corrosion resistivity, pull-out tests of Fe-SMA reinforcement and flexural strength of RC beam were evaluated experimentally. The FE-SMA exhibits recovery stresses of 250-300 MPa subjected to a temperature of 160°C. A comparison of load-carrying capacity of iron-based Fe-SMA reinforcement is also shown. [ABSTRACT FROM AUTHOR]

Because U-shaped steel beams filled with concrete have the advantages of reduced construction period and superior structural performance, they have been widely used as structural elements. In this study, the flexural behavior of newly developed bolt-connected U-shaped steel and concrete composite beams under a negative bending moment was experimentally evaluated. The main test variables were bolt spacing in bottom steel plates and types of U-shaped steel sections. Test results showed that the flexural behavior of the composite beams is determined by the plate-buckling mode of bolt-connected bottom steel plates. Composite beams with a greater bolt spacing than that in the standard AISI S100-16 experienced early plate buckling of the bottom steel plates, resulting in reduction of flexural stiffness and maximum flexural strength. Thus, the buckling mode of bolt-connected bottom plates should be considered for bolt-connected U-shaped composite beams under a negative bending moment. The longitudinal lips of U-shaped steel sections can increase the flexural performance of composite beams due to anchorage performance of the steel sections with lips. [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]

A database of results from 27 tests of diagonally reinforced concrete coupling beams was analyzed to develop improved force-deformation envelopes (backbone curves) for modeling and analysis of coupling beams. The database, which was selected from a larger set of 60 test results, comprises specimens that generally satisfy ACI 318-19 requirements. The analyses show that the chord rotation capacity of diagonally reinforced concrete coupling beams compliant with ACI 318-19 is closely correlated with beam clear span-to-overall depth ratio and, to a lesser extent, the ratio of hoop spacing to diagonal bar diameter. A simple expression is proposed for estimating beam chord rotation capacity. Coupling beam strength was shown to be more accurately estimated from flexural strength calculations at beam ends than other methods. Recommendations are made for obtaining more accurate backbone curves in terms of chord rotation capacity, strength, and stiffness. [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]

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]

One of the conventional retrofitting methods for reinforced concrete beams is flexural strengthening of beams with CFRP materials. In this study, a full scale reinforced concrete beam was constructed and evaluated under four-point flexural test. Afterward, a same beam was retrofitted in flexural region by monolayer of CFRP. These experimental tests were carried out to be the basis of verification for numerical specimens. For numerical study, ABAQUS software was used for modeling and analysis of totally five retrofitted reinforced concrete beams. The results show that the fully retrofitted beam with CFRP laminate and U-shape wraps has the best performance in terms of capacity and delay for emergence of cracks. It is worth to say, flexural strengthening in the middle of beam has not notable result in capacity, though, could convey the failure mechanism to out of pure bending region. [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]

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With the advancement of material science and infrastructure design technology, there is an increased need to reflect various loading scenarios in the design of civil infrastructures, including extreme loads such as impact and blast. However, structural behavior under extreme loads has been observed to be very different from that under static loads due to the high-rate loading condition. Therefore, extensive experimental and analytical studies have been conducted to explain the structural behavior under impact loading. From these efforts, various discussions have been presented on the impact behavior and the evaluation of the impact resistance of structures. However, despite the fact that the repair or reinforcement of structures damaged by impact loads is a critical issue, studies of the residual performance of impact-damaged structures are insufficient. This paper presents an experimental study to improve the understanding of the residual performance of impact-damaged structures. A total of 29 RC beams were tested under static loads to examine the effect of impact-damage on the residual behavior of RC beams. Of these, 8 RC beams were intact, and the other 21 RC beams suffered impact loading through drop weight impact tests and were damaged prior to the static flexural tests. The residual performance was evaluated by comparing the maximum load capacity, flexural stiffness, and displacement ductility of impact-damaged beams and intact beams. The comparison indicated that the flexural stiffness and displacement ductility of the impact-damaged RC beams decreased significantly, whereas their flexural strengths did not exhibit a significant difference. Predictive models for flexural stiffness and displacement ductility of the impact-damaged beams were suggested from the test results, and through these, the residual performance of the impact-damaged structure could be evaluated. [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]

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 fc′ = 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 fc′ = 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.

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]