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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]

It is common knowledge that increased temperatures have a negative impact on the axial load‐capacity and stiffness of reinforced concrete (RC) rectangular columns. This is something that is commonly acknowledged. For the purpose of restoring the axial capacity and stiffness of heat‐damaged RC columns, it is absolutely essential to carefully pick a suitable method for strengthening and repairing the columns. This research paper investigates the performance of various strengthening methods, such as the use of carbon fiber‐reinforced polymer (CFRP) jackets with near‐surface mounted (NSM) steel bars and a combination of welded wire mesh (WWM) and CFRP strengthening techniques, for the rehabilitation of RC rectangular columns that have been damaged due to exposure to high temperatures. Specifically, the paper focuses on the performance of these methods in relation to the rehabilitation of RC rectangular columns. There were three groups of tested RC rectangular columns: pre‐heated and unstrengthened, post‐heated and unstrengthened, and post‐heated and strengthened. Over a period of 3 h, 600°C was applied to the heated columns. Both a scheme utilizing a combination of unidirectional CFRP strips and NSM steel bars and another utilizing a combination of unidirectional CFRP strips and WWM were evaluated. Axial compression tests were performed on each column until failure occurred. The experimental test outcomes revealed that exposure to high elevated temperatures led to a decrease in the axial load‐carrying capacity of 38.6% and a decrease of 75.9% in initial stiffness, compared to unheated RC columns. Both strengthening schemes proved effective in restoring and surpassing the initial load‐carrying capacity of undamaged RC rectangular columns by an average of 35%. Notably, the combination of CFRP strips and WWM exhibited superior performance in restoring the initial stiffness of post‐heated RC rectangular columns, representing a novel finding. The strengthening scheme employing WWM and CFRP recovered 61.3% of the lost axial strength caused by high temperature, while the NSM/CFRP scheme restored 34.5% of the lost axial strength. In addition, the utilization of NSM in combination with CFRP strips as well as utilization of the WWM and CFRP systems leads to stiffness enhancement of 52.1% and 123.7%, respectively, when compared to post‐heated and unstrengthened RC columns. However, the study's findings have clearly shown that combination of WWM and CFRP strips is efficient in enhancing the strength of heated and unheated damage RC beams. [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]

The dual‐function retrofitting system that uses the carbon‐fabric reinforced cementitious matrix (C‐FRCM) as both the anode of impressed current cathodic protection (ICCP) system and the structural strengthening (SS) material, that is, an ICCP‐SS system, is investigated. The experimental program mainly focused on the shear behavior of C‐FRCM strengthened reinforced concrete (RC) continuous beam under the dual‐function retrofitting system. The influence of anode polarization on the shear strengthening of RC continuous beams is analyzed. Shear tests were conducted on a total of 14 corroded RC continuous beams to investigate the influence of key parameters, including anode polarization degree of prefabricated C‐FRCM plate, layer of carbon fiber mesh and side‐wrapping. The failure modes, shear capacities, and load‐deflection curves of the shear‐strengthened RC continuous beams are reported. Based on the test results, the applicability of relevant design codes was evaluated and found to provide rather conservative predictions for the shear capacity of the examined C‐FRCM strengthened RC continuous beams. [ABSTRACT FROM AUTHOR]

This article presents a review of state of the art on nonmetallic reinforcement in terms of bending moment redistribution in double‐span elements. The authors present a summary of existing research programs focused on moment redistribution in FRP (Fiber Reinforced Polymer) reinforced concrete (RC). On this basis authors created a database of concrete elements with all the important construction properties of the elements. Gathered data are presented with quantitative analysis of several variables effecting moment redistribution in published articles. In the following publication authors show a research review which includes an analysis of the influence of variable parameters from the point of view of the database, concerning: degrees of longitudinal reinforcement, ratio between degrees of reinforcement in span and over the support, type of reinforcement (FRP/steel/hybrid), concrete class and transverse reinforcement. [ABSTRACT FROM AUTHOR]

This paper presents the experimental study and finite element modeling of the flexural behavior of concrete beams reinforced with reused steel bars as longitudinal reinforcements. The experimental program and results of eight reinforced concrete (RC) beams constructed with and without reused steel bars are described in detail. The replacement percentages of brand‐new bars with reused steel bars in the tested beams were 50% and 100%. The reused steel bars were coated with and without epoxy. Steel fibers with fractions of 0.5% and 1.0% of the concrete volume were added to the concrete mixes. The load‐deflection relationship, ductility index, toughness, and failure modes of the tested beams are presented and discussed. It is shown that utilizing reused steel bars decreases the ultimate load of RC beams but increases their deflection at the ultimate load compared with the control beam. Increasing the steel fiber ratio increases the ultimate load and the deflection at the ultimate load of RC beams incorporating reused steel bars. However, the zinc‐rich epoxy used to coat the reused steel bars does not affect the behavior of the beams. Three‐dimensional nonlinear finite element (FE) models of the tested beams were developed using ABAQUS and validated against the test results. The developed FE models are capable of accurately simulating the experimentally observed behavior of RC beams with reused steel bars. [ABSTRACT FROM AUTHOR]

Glass fiber reinforced polymer (GFRP) concrete beams reinforced by carbon fiber reinforced polymer (CFRP) grid reinforced engineering cementitious composite (ECC) have excellent flexural performance and corrosion resistance in marine environments. However, the lack of a reliable theoretical model for predicting the flexural behavior of the hybrid beams makes it challenging apply them in the practical engineering. To address this issue, a series of numerical models were established to investigate the effects of key parameters on the flexural behavior of the hybrid beams, including the peak load, the neutral axis height, and the sectional stress distribution. Subsequently, based on the influence of the failures of different materials on the flexural performance of the hybrid beam, the loads of four feature points were calculated in the theoretical model to predict the entire load–displacement curve. Finally, the application range of the theoretical model was given based on the neutral axis height. The results showed that the cover thickness of the ECC, the GFRP reinforcement ratio and the cross‐sectional area of the CFRP grid were the key factors affecting the flexural performance of the hybrid beams. The theoretical model established in this study can predict the load–displacement curve accurately and can provide a reference for the subsequent design of the hybrid beams. [ABSTRACT FROM AUTHOR]

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

Reinforced concrete deep beams in bridges and other critical infrastructure are subjected to millions of load cycles during their service life. At the same time, they typically work with high shear and develop critical diagonal cracks. The cyclic loading across the cracks results in fatigue damage of the shear‐resisting mechanisms, which needs to be taken into account in the assessment of existing structures, and in particular in members with small amount of shear reinforcement built according to early design codes. To aid the development of advanced assessment approaches for such structures, this paper presents five large‐scale fatigue tests of deep beams with a stirrup ratio of 0.134%. The beams are preloaded to develop complete diagonal cracks, and then are subjected to cycles with different minimum and maximum load. The focus is placed on detailed crack measurements, needed for the development of crack‐based assessment approaches. The crack data is analyzed with the help of the two‐parameter kinematic theory to quantify important deformations. It is shown that the fatigue across the shear cracks is associated mainly with degradation of aggregate interlock and progressive damage in the critical loading zones. It is also shown that as the maximum load is decreased, the fatigue life increases, and the failure mode can switch from shear to flexure. [ABSTRACT FROM AUTHOR]

The reinforced concrete (RC) beams could be upgraded in shear using steel and fiber‐reinforced polymer (FRP) having several shapes (bars, strips, or sheets). Using near‐surface mounted (NSM) Glass FRP (GFRP) bars is still limited compared to carbon FRP (CFRP) elements as shear reinforcement. Moreover, using reinforced high‐strength concrete layers (HSCL) as NSM shear strengthening for the RC beams is still limited. Herein, three RC beams internally reinforced in shear using different shear areas (without, 100 mm stirrups apart, and 200 mm stirrups apart) were experimentally tested as reference beams (CB). Other eight beams strengthened in shear using NSM HSCL, and bars were experimentally tested. Moreover, an extended finite element (FE) simulation was implemented through a verified FE model to study the effect of other NSM aspects on shear‐strengthened beam response. The results explained that, regardless of the internal stirrups area and external NSM characteristics, the shear‐strengthened beams showed higher load efficiency than the corresponding CB. The NSM upgraded shear beam had slightly higher load efficiency than the un‐strengthened beam having the same steel area as internally shear stirrups. Moreover, increasing the internal shear stirrups decreased the total efficiency of the NSM shear strengthening and the internal stirrups regardless of the NSM characteristics. Furthermore, the NSM HSCL was more efficient than the corresponding NSM bars in increasing the load capacity and stiffness of the shear‐strengthened beams. The reported analytical model predicted well the shear capacity of the tested beams. [ABSTRACT FROM AUTHOR]

Silica, a principal component of waste glass powder (GP) reacts with calcium hydroxide to form the hydration products, and the process is affected by the fineness of GP and the percentage of cement replaced. This study investigates the structural behavior of concrete incorporating GP in reinforced concrete members by 0%–25% (by weight) replacement of cement with GP along with 0%–0.45% addition of glass fibers (GFs). The compressive and tensile strengths, strength activity index (SAI), and failure mode of treated concrete mixtures have revealed the optimum values as 15% replacement of cement with GP with 0.3% of GF. In the second stage of experiment, reinforced concrete beams were cast at various percentages of GP and GF to investigate the load–deflection response. It was observed that the beam specimen treated with GP exhibited considerably less mid‐span deflection (14.8 mm) at failure as compared to the control beam (with no GP and GF) which failed at 29.4 mm. The beam specimen treated with GP only showed significant degradation in stiffness after the peak load due to the fact that a part of GP remains unreacted and acts as a filler. Moreover, the beam specimen cast at optimum percentages of GP (15%) and GF (0.3%) showed large mid‐span deflection and higher failure load as compared to the control beam. These results suggest that the partial replacement of cement with GP should be accompanied by the addition of fibers to avoid unwanted brittle responses of GP concrete, with the additional advantage of reducing the non‐biodegradable waste. [ABSTRACT FROM AUTHOR]

To study the influence of the defects on the flexural behavior of laminated T‐beams, full‐scale beam tests of three reinforced concrete laminated T‐beams with incomplete bonding and one non‐defective reinforced concrete laminated T‐beam were conducted under monotonic loading. The results showed that the failure modes and crack patterns of the defective beams were similar to those of beams without defects. However, horizontal cracks appeared in these defects. Although the peak loads of the four specimens were relatively close, the difference in the maximum deflection was distinct. The deflection span ratio of each specimen exceeded 1/17, and the displacement ductility ratio exceeded 15. The results indicate that internal defects have only a slight influence on the flexural capacity of laminated beams but significantly influence their ductility. [ABSTRACT FROM AUTHOR]

Iron tailings have been extensively studied as mineral admixtures and as coarse and fine aggregates. However, few studies have been conducted on the mechanical properties of iron tailings concrete structures. Using iron tailings powder as an mineral admixture, and iron tailings gravel and sand as coarse and fine aggregates, respectively, the flexural behavior of full iron tailings concrete (FITC) beams was investigated experimentally. Compared with conventional concrete (CC) beam, we showed that the crack‐resistant, yield, and ultimate moments of FITC beams are similar to those of the concrete strain of FITC beams, which is in good agreement with the plane section assumption before cracks appear. The low elastic modulus of FITC makes the deflection of three FITC beams larger than that of a CC beam. The current design code of China is appropriate for calculating the load‐carrying capacity of FITC beam; however, the deflection calculation formula should be modified. [ABSTRACT FROM AUTHOR]

Dowel action of the longitudinal reinforcement in RC beams without and with small amounts of shear reinforcement is typically considered a constant shear contribution determined from the splitting strength of the concrete cover. However, in a recent experimental investigation by the authors, it was shown that the shear force transferred by dowel action for beams without shear reinforcement should be determined from the dowel displacement and a linear elastic model and a rigid plastic dowel model. This article is aimed at extending this model to also cover members with small amounts of shear reinforcement. To that aim, a novel approach to calculate the shear force carried by dowel action of the longitudinal reinforcement in both beams with and without shear reinforcement is presented. The model is derived by establishing an equilibrium of work between the internal stored elastic or dissipated plastic energy and the external work performed by the shear force in the dowel. Additionally, a method to determine the displacement of the dowel from DIC measurements is presented. For the remaining shear‐transfer actions, reasonable constitutive models from the literature are adapted. On the basis of DIC measurements, the shear force carried by each of the shear‐transfer actions is calculated for 16 shear tests of beams without and with small amounts of shear reinforcement. The sum of shear force carried by each of the shear‐transfer actions is shown to predict the applied shear force fairly well, from the development of the critical shear crack until failure. Additionally, it is shown that for beams with shear reinforcement below the minimum requirements according to the current design standards, the shear capacity is governed by aggregate interlock, residual tensile stresses, and the inclination of the compression chord. While for beams with shear reinforcement above the minimum requirements, the shear capacity is governed by the shear reinforcement and dowel action. [ABSTRACT FROM AUTHOR]

The present paper proposes a mechanical model for the prediction of the response of slender reinforced concrete beams with corroded transverse and longitudinal reinforcements. The proposed model is based on the Modified Compression Field Theory and is able to predict the load–displacement curve of members subjected to monotonic displacement‐controlled tests up to their peak load. The corrosion‐damage effects are considered by means of an effective width of the beam and by means of reduced values of both cross‐sectional area and strain capacity of steel bars. The accuracy of the model is evaluated by comparison with results of tests reported in the literature. Moreover, a simple relation is suggested for the estimate of the shear strength of reinforced concrete beams with low values of the effective geometric percentage of (corroded) stirrups. [ABSTRACT FROM AUTHOR]

Since reinforced concrete members suffer from different types of loads during their service life, the steel bars embedded in reinforced concrete members can be easily corroded in chloride‐laden environment. To investigate the influence of combined effect of load and steel corrosion on the flexural stiffness of recycled aggregate concrete (RAC) beams, 12 RAC beams were prepared and tested. The effects of load level (i.e., the ratio of the load applied to beams to the ultimate load) and recycled coarse aggregate (RCA) replacement ratio (i.e., the ratio of RCAs to replace natural coarse aggregates) on the internal force arm coefficient of cracking cross‐section, the elastoplastic resistance moment coefficient of cross‐section, and the strain incongruity coefficient of corroded tensile steel bars were analyzed, and a calculation model for flexural stiffness of RAC beams under combined effect of load and steel corrosion was established. The results showed that when the ratio of bending moment to ultimate bending moment of the pure bending part of beams was within 0.55–0.80 and the average mass loss of tensile steel bars was less than 3.23%, 0.85 could be adopted as the internal force arm coefficient of cracking cross‐section. The elastoplastic resistance moment coefficient of cross‐section was approximately a constant when the corroded RAC beams were in the service stage, while it increased obviously with the load level. There was a strong linear relationship between strain incongruity coefficient and average mass loss of tensile steel bars during the service stage of corroded RAC beams, and the strain incongruity coefficient increased linearly with the load level. The calculated values of the model of flexural stiffness proposed in this paper were in reasonable agreement with the experimental values. [ABSTRACT FROM AUTHOR]

Reinforced concrete (RC) and prestressed concrete (PC) structural elements need to be designed in order to guarantee large plastic deformations, avoiding any loss in their load bearing capacity. In this framework, the rotation capacity of RC and PC beams has been demonstrated to be a function of concrete mechanical properties, reinforcement characteristics, and of the structural size. On the other hand, Theory of Plasticity as well as the International Standards completely disregard size‐scale effects and ductile‐to‐brittle transitions, leading to an overlook of the strain‐softening behavior of the concrete matrix and of the rotation capacity of RC beams. On the other hand, the Cohesive/Overlapping Crack Model is able to evaluate concrete cracking in tension and concrete crushing in compression, as well as snap‐back and snap‐through unstable phenomena, steel yielding and/or slippage. This Nonlinear Fracture Mechanics model predicts a reduction in the moment versus rotation plastic plateau by increasing the beam depth and/or the reinforcement percentage. The numerical investigations carried out on reinforced and prestressed high‐performance concrete beams having rectangular or T‐shaped cross‐sections highlight the size‐scale effects on plastic rotation capacity that allow to formulate new scale‐dependent upper and lower limits of reinforcement percentage to guarantee a stable and ductile postpeak behavior of reinforced concrete structures. [ABSTRACT FROM AUTHOR]

Polyethylene terephthalate (PET) is a new type of fiber‐reinforced polymer (FRP) composite material, which has the characteristics of high performance, high toughness, high tensile fracture load, low elongation, low creep, no rust, and safety in use. The good performance of PET can significantly improve the mechanical properties of its components. A total of six reinforced concrete (RC) beams were produced in the test, one of which was a comparison beam, and the other five were reinforced with PET. In the test, the PET reinforcement spacing, number of reinforcement layers, and laying method were used as control variables, and an experimental study on the normal section bending performance of the specimen was performed. The test analyses the failure characteristics, crack width, bearing capacity, and deflection of the specimens under different reinforcement conditions. The test results showed that PET reinforcement can effectively inhibit the occurrence and development of cracks in RC beams and improve the ultimate bearing capacity and ductility of the components. The smaller the PET reinforcement spacing, the higher the ultimate bearing capacity; the greater the number of PET layers, the better the ductility of the specimen. Additionally, the economy, environmental protection, and portability of PET are of great significance for its application in practical engineering reinforcement. [ABSTRACT FROM AUTHOR]

This paper presents an experimental program of the bond behavior of concrete beams reinforced with hybrid fiber‐reinforced polymer (FRP) and steel bars, and the bond behavior between flexural cracks is investigated. Under the static loading, both the slip of steel and glass FRP (GFRP) bars increased significantly after steel yielding, while the slip of steel bars presented a faster increase rate. A method of calculating the bond stress based on test data was proposed, and this method overcame the disadvantage of histogram distribution of the conventional method. An analytical model of calculating the bond stress was proposed, and was verified with the test results. Under the fatigue loading, the bond stress deteriorated more seriously with a higher upper limit of fatigue load. The slip increased rapidly at the initial stage, and remained approximately unchanged with the increase of fatigue cycles, and the slip increased dramatically when the beam was subjected to fatigue failure. After fatigue loading, the yielding strength and ultimate strength of steel bars showed an increase rate less than 5%, while the hardening phase decreased significantly. The ultimate tensile strength of GFRP bars after fatigue decreased in the range of 4.5%–32.3%, and the modulus for elasticity remained unchanged. [ABSTRACT FROM AUTHOR]

This paper presents a modeling approach to analyze the flexural response of hybrid reinforced concrete beams with localized corrosion. A new mechanical model based on extensive uniaxial testing is proposed to describe the stress–strain relationship of corroded bars with a single pit. The proposed mechanical model is then incorporated into a sectional analysis to determine the moment curvature relationship of hybrid reinforced concrete sections with pitting corrosion. The actual crack pattern is used to divide a beam into discrete hinge elements which are then combined to compute the load–deflection response of statically determinate beams. The modeling approach is evaluated with available experimental data showing good predictive capabilities. A parametric study revealed the importance of the interaction between the tensile reinforcement ratio and the concrete postcracking residual stress. Furthermore, the deformation capacity of reinforcement bars with pitting corrosion levels beyond 0.25 was shown to have a dominant effect on the ultimate deflection of hybrid reinforced concrete beams. [ABSTRACT FROM AUTHOR]

High‐performance fibre reinforced concrete represents a promising alternative to conventional reinforced concrete for the construction of prestressed precast girders for road bridges. Specifically, all shear reinforcement is replaced by the use of steel fibres, which leads to important savings from the material and economical perspectives. Therefore, reliable shear formulations are required for these specific cases. In an effort to evaluate the accuracy of code expressions, this paper presents a database collecting 80 experimental shear tests on prestressed fibre reinforced concrete beams without stirrups. After illustrating its main characteristics, this database is used to verify the conservativeness and accuracy of shear formulation according to several codes and recommendations: i) Model Code 2010, ii) draft version of Model Code 2020, iii) draft version of the new Eurocode 2, and iv) Spanish National Code. The evaluation, carried out through the calculation of the model safety factor, indicated that the application of all shear formulations is largely conservative, leading to less unsafe tests than the desired 5% fractile. The relation between model safety factors and mechanical parameters is then investigated. Finally, the results obtained for the developed database are compared with those achieved from two larger databases of beams with similar features but without prestress. The comparison clearly proves the greater conservatism of code expressions when beams are prestressed. [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]

To reduce the impact on global warming, many countries and regions are advocating the use of low‐carbon and green supplementary cementitious materials (SCMs) to improve the cement industry. This study investigates the shear behavior of reinforced concrete (RC) beams made with a novel green concrete, limestone, calcined clay, and cement clinker (LC3). Full‐scale shear tests were conducted on RC and LC3‐RC beams to evaluate their fundamental behavior for structural applications. The shear resistance of LC3 concrete beams was evaluated using Chinese, American, and Eurocode codes, while carbon emission and environmental impact were analyzed by life cycle assessment (LCA). Results showed that LC3‐RC and RC beams exhibited similar shear behavior in terms of crack initiation, propagation, and development. The increase in concrete strength improved the stiffness of LC3‐RC specimens, while RC specimens remained unchanged. The ductility of RC specimens was inversely proportional to concrete strength, while LC3‐RC beams exhibited optimal ductility. The increase in stirrup ratio significantly improved the shear resistance of both LC3‐RC and RC beams. With increased shear‐span ratio, the failure mode of LC3 specimens improved, changing from diagonal‐compression to shear compression or diagonal tension failure. The shear resistance of both LC3‐RC and RC beams was underestimated by GB 50010‐2010, ACI 318‐19, and Eurocode 2. LC3 concrete significantly reduced energy consumption and carbon emissions and achieved favorable environmental benefits in terms of GWP, PMFP, POFP, TAP, and TETP. Increasing usage of limestone in LC3 may further decrease environmental potential without sacrificing mechanical properties. The findings of this study contribute to the development of sustainable and environmentally friendly structures in engineering. [ABSTRACT FROM AUTHOR]

High‐performance fiber‐reinforced concrete (HPFRC) can be considered a promising material for the construction of precast concrete girders for road bridges. This paper presents conceptual considerations and numerical analysis to support this statement. The HPFRC is a compromised alternative between FRC and UHPFRC mixes. Specifically, a tailor‐made mix design of HPFRC jointly developed by ACCIONA and the authors is presented, and then compared with the other types of fiber‐reinforced concretes collected from the technical literature. In addition, some trends observed in the database are described. This material characterization is followed by a conceptual analysis of the advantages of the application of HPFRC to road bridges. Specifically, a proposed bridge for the case of a 60 m‐span box girder is analyzed. A comparison between alternatives based on the use of HPFRC and conventional reinforced concrete is discussed. The results shed light on the viability of this material for bridge application. Specifically, the main finding show potential significant material savings in structural elements of the superstructure. Finally, ongoing and future research for a wide application to the construction sector are briefly discussed. [ABSTRACT FROM AUTHOR]

Hybrid reinforced concrete (HRC) can be defined as a cementitious material in which the reinforcing secondary phase consists of a combination of continuous steel rebars and of short discontinuous fibers, randomly distributed within the concrete matrix. For these structural elements, experimental flexural tests highlight how the postcracking response of the composite is strongly affected by the amount of steel bars together with reinforcing fibers. In the present work, it is shown that the action of these two contributions can be clearly interpreted in the framework of Fracture Mechanics through the Updated Bridged Crack Model (UBCM). The model assumes nonlinear constitutive laws to describe the toughening action of the reinforcing secondary phases, which are related to the yielding of steel rebars and to the pull‐out of the short fibers. Under these assumptions, different postcracking regimes depending on three scale‐dependent dimensionless numbers can be predicted: the bar‐reinforcement brittleness number, NP, which is directly related to the steel bar area percentage, ρ; the fiber‐reinforcement brittleness number, NP,f, which is directly related to the fiber volume fraction, Vf; and the pull‐out brittleness number, Nw, which depends on the critical embedment length of the fiber‐reinforcement, wc. The couples of critical values of the two reinforcement brittleness numbers define the minimum reinforcement conditions of the HRC structural element—that is, the combination of ρmin and Vf,min required to guarantee a stable post‐cracking response—including its scale dependence. A parametrical analysis is presented together with the modeling of an experimental campaign reported in the literature in order to assess the effectiveness of the UBCM. [ABSTRACT FROM AUTHOR]

Thin‐walled textile‐reinforced concrete beams have recently emerged as a promising approach for material‐efficient design. However, the increased complexity of the formwork is a major challenge in implementing such elements for broader use in the construction industry. This study presents a novel type of stay‐in‐place flexible formworks with integrated textile reinforcement. The use of weft‐knitted textiles allows the integration of continuous high‐strength rovings as shear reinforcement and the introduction of spatial features within the fabric to guide bending‐active rods to shape the complex cross‐section geometry. The manufacturing procedure and the structural performance were investigated in an experimental campaign consisting of four concrete beams with I‐profile cross sections tested in three‐point bending, where aramid rovings were used for the shear and conventional deformed steel bars for the flexural reinforcement. The transverse reinforcement ratio proved to be essential in increasing the shear strength. Thereby, the use of digital image correlation measurements of the surface deformations allowed the direct assessment of the strains and, thus, the mechanical activation of the textile reinforcement. The full tensile capacity of all the aramid rovings crossing the governing crack could not be exploited due to the brittle material behavior, resulting in a progressive failure once the first roving reached its tensile strength. Compatibility‐based stress fields were used to predict the load‐deformation and failure behavior of the tested beams, which resulted in an excellent agreement of the ultimate loads and failure modes obtained from the model with the observations and results from the experiments. [ABSTRACT FROM AUTHOR]

In topology optimization with discrete model finite element analysis (FEA), feasible reinforcement domain determines to a large extent the result, and the trade‐off between accuracy and efficiency of optimization as well. Therefore, a cantilever reinforced concrete short beam was comparatively optimized based on five feasible reinforcement domains with complexity at different levels, respectively. The outcomes exhibit that, it is reasonable to evolve reinforcement layout by topology optimization with discrete model FEA. The orientation of diagonal reinforcement in optimal topologies from complex feasible reinforcement domains would correspond more to the orientation of the principal tensile stress than that using simple ones, since complex ones have rebar distribution with high density or diagonal reinforcement with various orientations. After optimization, the global stress level of the reinforcement decreases, and then utilization rate of the reinforcement strength increases. Additionally, the consumption of rebar and the workload of reinforcement engineering only slightly increased, although such optimal reinforcement topologies are relatively complex. Consequently, the mechanical properties of concrete members can be substantially improved by using a more complex feasible reinforcement domain for optimizing rebar distribution. A complex domain should be chosen on the premise of completing the optimization within a reasonable time in engineering applications. [ABSTRACT FROM AUTHOR]

This article describes the second blind simulation competition (BSC) organized by the fib WG 2.4.1, which aims to assess the predictive performance of models based on the finite element method (FEM) for the analysis and design of fiber reinforced concrete (FRC) structures. Slabs supported on columns or piles have becoming competitive applications for FRC due to the technical and economic benefits may be obtained by combining properly the fiber reinforcement mechanisms to those provided by conventional reinforcement placed, as a strip, in the alignment of columns/piles. Therefore, a representative zone of this structural system, namely a hybrid fiber reinforced concrete (R/FRC) shallow beam, is chosen in this BSC to show the potentialities of FRC in these types of applications, as well as to assess the predictive performance of FEM‐based computational models on the design verification at serviceability and at ultimate limit state conditions (SLS and ULS, respectively). Two statically indeterminate shallow beams of two equal spans were tested up to their failure, by recording the applied loads, the strains in the conventional reinforcements and in the FRC of the critical zones of the structure. By using digital image correlation, the average crack width at the level of the flexural reinforcements was recorded. The participants had to predict these results by receiving information about the mechanical properties of the materials, the geometry of the prototypes and their loading and support conditions. In this article, the rules and the results of this 2nd BSC competition are presented, and the data obtained experimentally is thoroughly analyzed. [ABSTRACT FROM AUTHOR]

Polyvinyl alcohol‐engineered cementitious composite (PVA‐ECC) exhibits strain hardening and multiple cracking characteristics under tension. Its superior tensile behavior may also influence the flexural behavior of reinforced PVA‐ECC beams. This paper investigates the load capacity and failure mode of reinforced PVA‐ECC beams in bending. Seven beams with different tensile reinforcement ratios, including six PVA‐ECC beams and one conventional concrete beam, were tested in the experimental program. The influence of reinforcement ratio on load capacity and failure characteristics was discussed in detail. Test results showed that with increasing reinforcement ratio, the ultimate load of beams was increased, but the failure mode was changed from fracture of PVA‐ECC in the tension zone to crushing in the compression zone, thereby limiting the full development of beam ductility. An analytical model is proposed to calculate the load and the vertical deflection of beams. In the model, the tension‐stiffening effect of reinforcement after cracking of PVA‐ECC is considered by defining the bond–slip relationship of reinforcement embedded in PVA‐ECC. Comparisons are made between experimental results in the literature and those calculated by using the analytical model to show the accuracy of the model in predicting the load–deflection relationship, the moment–rotation relationship, and the moment–curvature relationship. [ABSTRACT FROM AUTHOR]

In the present work, the effect of early‐strengthening of reinforced concrete (RC) beam specimens using layers of ultra‐high performance concrete (UHPC) on their performance against reinforcement corrosion was examined. A number of fifteen RC beam specimens were prepared, one beam specimen uncorroded and unstrengthened was considered as a control beam, two beams were corroded and unstrengthened, and twelve corroded and strengthened beam specimens that were divided into two groups. RC beam specimens of the first group were corroded continuously to cause total theoretically targeted mass losses of the steel rebars and then strengthened using UHPC layers. RC beams of the second group were also corroded to the same degrees but in two steps. In the first step, the beams were corroded to cause a portion of targeted theoretical mass losses. Then the beams were strengthened in the same way as the beams of the first group and then subjected to second‐step accelerated reinforcement corrosion to achieve finally the same degrees of total theoretical mass losses as that of the first group. The corroded and strengthened beam specimens were exposed to flexural testing, and then the corroded rebars extracted from the beams were used to conduct gravimetric tests to determine the actual values of the mass losses due to accelerated corrosion. The gravimetric and flexural tests' results were used mainly to observe the influence of early‐strengthening on the actual mass loss and the flexural behavior of the tested beam specimens. Results showed a significant reduction in the values of the actual mass loss and better flexural behavior due to the early‐strengthening of the corroded beams. An analytical model, developed and validated using the data collected from the experimental tests, can be utilized to predict the ultimate load‐carrying capacities of the corroded strengthened RC beam specimens. [ABSTRACT FROM AUTHOR]

This paper investigates the shear performance of corroded reinforced concrete (RC) beams with different stirrup corrosion rates and strengthening interventions. In this work, eight corroded beams strengthened with various interventions, including U‐shaped stirrup, bonded steel plate, and anchored steel plate strengthening techniques, were tested under static loading. The experimental shear capacity, load–deflection response, and failure modes of the unstrengthened and strengthened specimens were carefully studied. Three shear capacity models based on GB50010‐2010, ACI 318‐08, and Eurocode 2 codes were proposed and discussed. The results showed that all specimens have the same failure mode, that is, the shear–compression failure. The shear capacities are improved by 17.36%–23.61% and 23.76%–38.46% by these interventions for the specimens with 10% and 20% stirrup corrosion rates, respectively. The anchored steel plate technique provides the maximum improvement in the shear capacity. Additionally, the increased stiffness of corroded specimens with strengthening interventions is apparent when the corrosion rate is 10% but not obvious when the corrosion rate is 20%. The models based on GB50010‐2010 and ACI 318‐08 codes were proved to have higher accuracy but may overestimate the shear capacity. In contrast, the Eurocode 2‐based model comes with relatively low prediction accuracy but conservative results, and it is recommended for engineering design. [ABSTRACT FROM AUTHOR]

The damping of simply supported rubberized concrete beams was measured and compared against conventional concrete beams in their uncracked and cracked states. The variables controlled were: rubber content (10% and 20% by total volume of aggregates replaced), reinforcing content, axial load, and damage state. Impact hammer‐induced free‐vibration was used to excite the specimens and quasi‐static four‐point bending used to damage the beams. Rubberized concrete displayed a measurable increase in damping relative to ordinary concrete in both the uncracked and cracked states. It was found that reinforcing appears to reduce the damping of all beam specimens in their undamaged state compared to unreinforced counterparts. No relationship was found between reinforcing ratio and damping. For crack widths up to 0.1 mm a non‐linear monotonic increase in damping was observed. Damping measured throughout the entire pushover response of the beams was found to follow a skewed‐shaped bell curve. Compressive axial load was found to reduce the damping of the beams. The shape of the free vibration decay envelopes was examined. Rubber was found to make the damping response more viscous‐like. Whilst reinforcing made the shapes of the decay curves more similar between beams made of different concrete types. No clear evidence for friction damping due to cracking was found. For all beams, based on the free‐vibration response, it was found that the damping exhibited by both plain and reinforced concrete is not a true exponential decay curve. This means that the damping calculated by the logarithmic decrement method will depend on the choice of interval selected. A method for standardizing the implementation of the logarithmic decay method to avoid arbitrary choices of intervals and allow for fairer cross‐study comparison of damping values was therefore proposed. [ABSTRACT FROM AUTHOR]

This paper investigates the effect of material properties, boundary conditions, and related modeling and design uncertainties on the fire behavior of statically indeterminate reinforced concrete beams and slabs by means of a parametric study based on a comprehensive model. This model uses material properties specified by EN 1992‐1‐2, complemented by considerations concerning the biaxial compressive strength of concrete, strain hardening and limitations of the ultimate strain of reinforcement, as well as tension stiffening. The parametric study identifies and explains the most influential parameters governing the fire behavior of statically indeterminate reinforced concrete beams and slabs. The implementation and generalization of these parameters are evaluated and compared to current design rules in EN 1992‐1‐2 derived from the evaluation of experimental testing and real fire cases. Overall, the detailing rules given in EN 1992‐1‐2 are found to be reasonably safe, and they can be easily used for practical applications. Furthermore, the results of the study indicate that model predictions for the studied statically indeterminate systems are subject to considerable uncertainty because (i) information on the used material is possibly incomplete and (ii) the models given in design codes do not (or only insufficiently) cover all relevant aspects of the thermo‐mechanical behavior. Specifically, the concrete aggregate type with its corresponding thermal expansion, the strain hardening properties of the reinforcement and tension stiffening with its detrimental effect on the ductility of the tension chord may affect the rating across several standard fire resistance times of statically indeterminate reinforced concrete members subjected to bending. [ABSTRACT FROM AUTHOR]

Small amounts of shear reinforcement are often assumed to increase the shear capacity of RC beams, compared to an identical beam without shear reinforcement. However, in a recent experimental campaign, the shear capacity of beams with a shear reinforcement ratio below the minimum requirements according to the design standards turned out to be similar to identical beams without shear reinforcement. This paper presents a detailed analysis of why the shear capacity may be similar for beams without‐ and beams with small amounts of shear reinforcement. This includes the influence of small amounts of shear reinforcement on the shear behaviour and shear‐transferring mechanisms. The analysis shows that the crack development is more severe at the ultimate load for beams with a small amount of shear reinforcement compared to beams without shear reinforcement. This more severe crack development is shown to cause an overestimation of the shear contribution from aggregate interlock when applying a well‐known constitutive model often used for beams without shear reinforcement. Therefore, a new expression for the aggregate interlock stresses is proposed. A comparison of the proposed expression with Mixed‐Mode crack opening tests shows a good agreement with the test for both small and large crack openings. By applying the proposed expression on the measured crack kinematics it is shown that for a large shear contribution from aggregate interlock the shear contribution from the shear reinforcement is very limited and as the aggregate interlock stresses decrease the shear contribution from the shear reinforcement increases. This shift in the governing shear‐transferring mechanism can help to improve the requirements for the minimum shear reinforcement often found in the design standards. [ABSTRACT FROM AUTHOR]

There are only a few studies related to the effect of the hybrid fiber reinforcement on the flexural behavior of full‐scale beam specimens having lap‐spliced length. Thus, this study will ensure important experimental data about the effect of macro steel fibers blended with micro steel fibers on lap‐spliced length. The aim of this study was to investigate the influence of hybrid steel fiber reinforcement on the flexural behavior of full‐scale reinforced concrete beams having different lap‐spliced bars. A sum of three traditional concrete mixtures including a total of 1% fiber by volume fraction was adopted: control mixture without steel fiber, only macro steel fiber and hybrid steel fiber reinforced mixtures. For this purpose, 18 full‐scale beams (200 × 300 × 2000 mm) having three different lap‐spliced length (15, 25, and 35Ø) as tension steel bars were produced and tested under four‐point bending to examine flexural behavior, mode of failure, ductility, and energy absorption capacity properties. In conclusion, the hybrid fiber reinforcement caused the highest increase in the load carrying capacity of the beam specimens. Besides, the hybrid fiber reinforced beam specimens exhibited excellent ductility and energy absorption capacity compared to single fiber reinforced beam specimens. On the other hand, it can be addressed that the hybrid fiber reinforced structural elements had a vital important to compensate the application errors and carelessness in steel bar workmanship, inadequate the lap‐spliced length as per the codes. It can be emphasized that the lap‐spliced length as per the building codes can be reduced in 40% by containing hybrid steel fiber (0.8% macro‐0.2% micro) reinforced concrete without a reduction in load carrying capacity, ductility, and energy absorption capacity compared to control beam specimens without fiber. [ABSTRACT FROM AUTHOR]

Corrosion of stirrups (generally with small diameters and concrete covers) significantly affects the shear strength of reinforced concrete elements. As shear failures may lead to brittle collapses, hence the need to avoid them during structures' entire service life. The Compression Chord Capacity Model (CCCM), a shear mechanical model, was recently extended to predict the strength of corrosion‐damaged beams by identifying the model parameters that could be most affected by steel corrosion. In this paper, the CCCM is combined with two material deterioration models included in the new Spanish Structural Code, and considers carbonation of concrete or chloride ions, to predict long‐term shear strength evolution. Finally, a parametric analysis is carried out to explore the effect of the most influential parameters on shear strength degradation according to the used models and depending on different exposure classes. [ABSTRACT FROM AUTHOR]

This research has investigated the effect of reinforcement corrosion on the flexural response of reinforced concrete beams subjected to blast loading. Five beams, with and without corrosion, were tested under blast loads using a shock‐tube. The corroded specimens were subjected to an accelerated corrosion regime prior to testing, with a mass loss of up to 22% in the longitudinal steel reinforcement over the mid‐span or full‐span regions. A companion set of two beams was tested under quasi‐static four‐point bending. The results from the static tests show that corrosion of the longitudinal reinforcement decreased the strength and ductility, and ultimately changed the failure mode from ductile to brittle. Under blast loading, the steel corrosion increased maximum displacements and support rotations, reduced blast capacity, increased damage and fragmentation, and led to more brittle failure as the % mass loss increased. The effects of corrosion on blast response were moderate when the steel was corroded over the full‐span region. Furthermore, the blast response of the beams was predicted using dynamic inelastic single‐degree‐of‐freedom (SDOF) analysis, with the resistance functions developed using 2D finite element modeling, while accounting for the reduction in steel stress–strain properties and corrosion‐induced cracking. The SDOF analysis showed acceptable results in terms of ability to predict maximum displacements of the flexural‐governed beams (corroded and un‐corroded). [ABSTRACT FROM AUTHOR]

It is important to assess existing reinforced concrete (RC) structures with damages. This task, however, is traditionally empirical and time‐consuming. To improve assessment accuracy and efficiency, this study proposed an approach to semantic model damaged RC beams based on point clouds. A slice‐based method for automatically modeling deformed beams and a color‐based crack detection method were developed for generating building information modeling (BIM) and finite element (FE) models. Furthermore, to enhance structural assessment and decision‐making by providing both damage and loading performance analysis data, a framework to extend the existing IFC standard was proposed for interoperability issues between FE models and BIM, aiming to integrate semantic‐enrichment damages and FE analysis results in the as‐is BIM model. Experiments were carried out on a simply supported RC beam subjected to a concentrated load. As a result, the improvement of the developed as‐is BIM model for damage visualization and structural assessment was confirmed. [ABSTRACT FROM AUTHOR]

This article aims to investigate the flexural behavior of strengthened corroded reinforced concrete (RC) beams using carbon fiber‐reinforced polymer (CFRP) laminates and using a hybrid system of CFRP laminates and ultrahigh‐performance concrete (UHPC) layers. A total of 15 RC beam specimens were prepared, out of which one specimen was uncorroded–unstrengthened, and 14 specimens were corroded using accelerated corrosion set up to cause a significant reduction in the load‐carrying capacity of the RC beams. The damaged covers of the corroded RC beam specimens were first repaired and then strengthened with different strengthening strategies involving CFRP laminates alone as well as the CFRP laminates and UHPC jacketing together. The experimental results obtained by testing the strengthened RC beam specimens in flexure showed a significant enhancement in the load‐carrying capacity and stiffness of the strengthened corroded RC beams. The number of CFRP laminates, hybridization of the CFRP laminates and UHPC layer, and the thickness of the UHPC layer all significantly improved the load‐carrying capacity and stiffness of the strengthened corroded RC beams indicating the possibility of selecting an optimal strategy out of different options for strengthening the corroded beams to achieve a targeted degree of the efficacy of the strengthening. The analytical model developed in this study to estimate the flexural capacity of the strengthened RC beams was found to predict the values of the load‐bearing capacity of the RC beams strengthened using different strategies very close to their respective experimental values. [ABSTRACT FROM AUTHOR]

When shear cracking occurs in existing reinforced concrete deep members, engineers are faced with the challenge of determining the safety of the members. This paper presents a crack‐based assessment approach that utilizes the Two‐Parameter Kinematic Theory (2PKT) as a framework for the assessment of lightly reinforced concrete deep beams. The paper presents three assessment approaches with progressively increasing levels of approximation (LoAs). The first level of approximation (LoA I) involves using the 2PKT in a predictive manner for situations where the crack shapes are unknown, LoA II improves upon LoA I by incorporating more detailed modeling of the strain in the transverse reinforcement at the location of the critical cracks, and LoA III includes the details of LoA II but also uses the detailed crack geometry as an input in the assessment. Each of the LoAs is presented and compared with experimental data from a 4‐m deep beam test in the literature. The shear carrying mechanisms determined from the kinematic model are evaluated and compared across LoAs. Finally, the paper utilizes LoA III to study the size effect in shear for deep beams. The results quantify the influence of aggregate interlock on the size effect in shear critical deep beams. [ABSTRACT FROM AUTHOR]

Investigations on steel fiber reinforced concrete (RC) beams in torsion show, that the steel fibers positively influence the torsional load‐bearing behavior. Since a systematic evaluation of the previously known test results and the derivation of a generally valid design model were lacking until recently, current codes such as Model Code 2010 do not contain any design models for the consideration of the steel fiber load‐bearing effect in the torsion design. Due to this, the existing torsion tests on steel fiber RC were summarized in a database. Furthermore, on the basis of the test results and observations, the space truss model developed by Rausch and later refined by Lampert and Thürlimann, among others, was further developed and supplemented by additional longitudinal and transverse steel fiber tension struts. This modified space truss model was validated with the database and shows good to very good predictions to the torsion test data. [ABSTRACT FROM AUTHOR]

This study numerically investigates the effects of bond properties between embedded through‐section‐glass fiber‐reinforced polymer (ETS‐GFRP) bars and concrete on the performance of the reinforced concrete (RC) beams strengthened in shear with ETS‐GFRP bars. The key bond parameters, including the interfacial fracture energy (Gf), bond stiffness (K), and bond strength (τm) are examined. Results demonstrate that the bond properties of ETS‐GFRP bar–concrete interfaces mainly affect the postpeak behavior and ductility of the ETS‐strengthened beams. The FE model considering triangle bond model for the ETS‐GFRP bar–concrete interfaces can reasonably predict the load versus deflection and failure mechanism of the ETS‐strengthened beam as well as the debonding process of the ETS‐GFRP bars from concrete against the experimental results. The use of the flexible and ductile adhesive, which has small bond stiffness and high interfacial fracture energy, for ETS‐GFRP bonding technology would lead to the large ductility of the ETS‐GFRP‐strengthened beams. The ETS‐GFRP bar–concrete interfaces with high cohesive strength can distribute the shear cracks and limit the local debonding, encouraging the deformability of ETS‐GFRP‐strengthened beams. [ABSTRACT FROM AUTHOR]

To improve the flexural behavior of reinforced concrete (RC) beams, a new ferrocement composite material was proposed. A polyvinyl alcohol fiber‐reinforced ferrocement cementitious composite (PVA‐RFCC) and steel wire mesh (SWM) were attached onto the soffit of the RC beams as a composite reinforcement layer (CRL). One control beam and four strengthened RC beams were investigated. The maximum load carrying capacity, initial stiffness, and displacement ductility parameter of the strengthened beams were up to 99.3%, 48.0%, and 90.9% higher than those of the control beam, respectively. The SWM2 accounted for 91.6% of these improvements. An analytical model was proposed to predict the flexural capacity of strengthened RC beams. The tensile force of the polyvinyl alcohol‐engineered cementitious composite was considered and calculated by rectangular and triangular distributions. The predicted results were in good agreement with the experimental results, which validated the accuracy of the proposed model. [ABSTRACT FROM AUTHOR]

This paper describes an experimental program, which investigates the validity of using Expression 7.21 in Eurocode 2 for calculating shrinkage curvatures of loaded reinforced concrete beams cracked in flexure, this Expression having previously been validated for use with uncracked sections but not for cracked sections. The experimental method used a heating technique, which exploited the differing coefficients of expansion of limestone concrete and stainless steel reinforcement to impose simulated shrinkage strains on a range of rectangular beams of various sizes and reinforcement percentages. The results indicate that Expression 7.21 is valid for use with sections cracked in flexure but may overestimate curvatures by significant amounts. It is shown that improved estimates of curvature are given by using Expression 7.18 in conjunction with Expression 7.21 with the best results being obtained by setting β = 0.3 or by using an adjusted value for the cracking moment (Mcr), as detailed in the paper. [ABSTRACT FROM AUTHOR]

Post‐installed connections are widely used in the rehabilitation, strengthening, and expansion of existing concrete structures. These connections accommodate the connecting of new elements to old concrete using post‐installed anchoring techniques. Attachment of new segments to concrete beams and columns requires the installation of anchors in slim concrete components. Under this condition, the behavior of connection is severely affected by the small width of concrete elements. Additionally, the behavior of anchors is influenced by the confining effects of stirrups in reinforced concrete elements. In this paper, the tensile behavior of chemical anchor connections in single and group formations of four and six anchors is investigated using the results of 36 individual experiments of adhesive anchors installed in plain and reinforced concrete beams. The key design parameters are embedment depth, section width, and effects of the reinforcement. The results indicate high levels of interaction between all studied parameters. The tensile capacities of the single and groups of anchors are compared against ACI 318 predictions. The main effects of parameters, as well as their interactions, are analyzed and discussed. Based on the test results, several recommendations are provided for the installation of adhesive bonded anchors in narrow concrete components. [ABSTRACT FROM AUTHOR]

The bending performance of polypropylene fiber reinforced engineered cementitious composite (PP‐ECC) beams was studied. A total of five reinforced concrete (RC) beams were prepared and tested. The test variables include matrix type, longitudinal reinforcement diameter, and longitudinal reinforcement ratio. The study found that ECC is an ideal building material to improve the bending performance of RC beams. For the failure mode, even if the ultimate load is reached, no local cracks are observed in the ECC beam. On the contrary, due to the high ductility of the ECC material, multiple microcracks appear in the tension zone of the beam. From the perspective of bending performance, the use of ECC materials as the matrix of RC beams can not only increase the cracking load, yield load, and ultimate load of RC beams but also increase its ductility and energy absorption capacity. A method for predicting the flexural bearing capacity of ECC beams considering the effect of fiber tensile stress is proposed. The experimental data in this study are compared with the experimental data in the previous literature, and the prediction results of this model and other previous models are obtained. The average ratio of the predicted value of the flexural bearing capacity of the RC beam to the experimental value is 0.979, and the coefficient of variation is 0.016. [ABSTRACT FROM AUTHOR]

Concrete tensile stresses influence the cracking behaviour and the stiffness of reinforced concrete (RC) members. Most design codes account for this tension stiffening effect using an effective reinforcement ratio. Although this ratio has a significant influence on the design of RC structures, its quantification is controversial in many cases, and typically relies on empirical geometry‐based expressions. One main reason for this knowledge gap is that the area of concrete in tension can only be verified indirectly, for example, through crack widths and spacings and using a suitable mechanical model. This indirect validation is subject to considerable uncertainty as it depends on parameters that scatter (e.g., bond stresses and the concrete tensile strength), and further assumptions relating internal stresses to the applied loads are required. This article outlines how refined measurements of the reinforcing steel strains and the concrete deformations in the compression zone, combining distributed fibre optic sensing (DFOS) and digital image correlation (DIC), can be used in order to obtain a more reliable quantification of the parameters affecting tension stiffening and hence, the effective reinforcement ratio. Selected models are validated against experimental data of an RC beam tested under four‐point bending, underlining the potential of DFOS and DIC as valuable tools for a better understanding of RC structures and the enhancement of mechanical models. [ABSTRACT FROM AUTHOR]

The shear crack width, crack behavior, and crack development of 24 reinforced concrete beams have been experimentally investigated. All the beams reinforced with longitudinal reinforcement and hooked‐end steel fibers in place of transverse reinforcement. Hooked‐end steel fibers 35 and 60 mm long are used at volume fractions ranging from 0.75% to 1.5% in the first case, and from 0.5% to 1% in the latter case. For extending the scope of the investigation, two types of concrete matrices (normal‐strength of 25 MPa and medium‐strength of 45 MPa) have been investigated. A simple mechanics‐based mathematical model is developed by determining the strains in the transverse direction of shear cracks and the average horizontal spacing between the shear cracks. The accuracy of the model has been confirmed with the experimental results and conservative predictions have been observed with mean, SD, and coefficient of variation as 0.99, 0.19, and 18.96, respectively. Based on detailed mathematical and experimental investigation, the minimum approximately observed shear crack width has value of 0.4 mm for all SFRC beams therefore the allowable shear crack width of 0.4 mm, for steel fiber reinforced concrete has been recommended. [ABSTRACT FROM AUTHOR]

Torsional tests for four concrete beams reinforced with glass fiber reinforced polymer (GFRP) bars as torsional longitudinal reinforcements and glass textile grids as torsional transverse reinforcements are conducted to study the possibility in using noncorrosive and cold‐bendable glass textile grids as minimum torsional transverse reinforcements. These beams are compared with three control beams reinforced with GFRP torsional transverse reinforcements. Two investigated variables in this experimental study are the number of layers of textile grids and the orientation of torsional transverse reinforcements. Grade 40 fine‐grained concrete is used for all tested beams. A standard pure torsional test is used to study the torsional behaviors of these beams. The experimental behaviors of the tested beams are compared in terms of recorded torque‐twist curves; strain gauge readings in transverse, longitudinal reinforcements, and concrete at critical positions; observed cracking patterns and failure modes. The experimental results are compared with the recommendations for minimum torsional transverse reinforcements in the existing design codes and guidelines such as the ACI 318‐19, EC2, ACI 440.1R‐15, and CSA S806. The comparison indicates that the existing guidelines are unsafe in estimating the minimum transverse torsional reinforcements for glass textile‐reinforced concrete beams. [ABSTRACT FROM AUTHOR]

Modeling and assessing the load‐carrying capacity of reinforced concrete (RC) structures that are cracked is important because the condition of an RC structure changes due to natural aging and accumulated damage. The current approach to determining the residual capacity of a cracked RC structure is time‐consuming and error‐prone due to a limited capacity to obtain and process structural information. In this study, an automated approach was proposed to determining residual capacity by performing finite element (FE) analysis of an RC structure using point cloud three dimensional modeling. Two simply supported RC beams were subjected to bending tests to provide validation data. The initial activity was to extract dimensional data from laser‐scanned point cloud data of a beam. The information obtained was used to automatically generate nonlinear FE models of the beam that was used for nonlinear FE analyses in Abaqus. An initial crack was added to the beam to model a cracked beam in real conditions. Three different models were used to simulate initial cracks, a weakened element model, a cohesive zone model, and an extended FE model. The results indicate that the proposed method of automating the combination of point cloud data with nonlinear FE analysis provides a novel practical approach to modeling and assessing cracked RC beams. [ABSTRACT FROM AUTHOR]