Reinforced Concrete Beam Specimens Research Articles

Flexural strengthening of RC beams by advanced concrete canvas

AbstractIn 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.

Experimental investigation of the seismic behaviour of eccentric RC beams with different reinforcement configurations

In reinforced concrete (RC) buildings, the seismic behaviour of RC beams with flush outside faces of beams and columns has not been verified by experiments. In this study, four large RC beam specimens were fabricated and an experimental verification was conducted. The results showed that all of the specimens (including three beam specimens with flush outside faces of beams and columns) could withstand ultimate drift angles up to 4% rad. In addition, the lateral strength and seismic behaviour of a specimen with a concrete cover of 85 mm were no less than those of the benchmark specimen, so a concrete cover thickness of 85–40 mm should be acceptable for RC beams. The seismic behaviour of two specimens with lateral U-shaped auxiliary transverse reinforcement and a concrete cover of 85 mm was better than that of the benchmark specimen, but the crack width of the latter was wider and the spalling degree of the concrete cover was more serious. Based on the results of this work, the practical recommendation is to adopt lateral U-shaped auxiliary transverse reinforcement in which the two legs extend beyond half the width of the hoop, with two auxiliary longitudinal reinforcements and the same spacing as the hoop.

Combined deterioration effects of freeze–thaw and corrosion on the cyclic flexural behavior of RC beams

Reinforced concrete (RC) stands as the predominant construction material, and with the growing prevalence of aging infrastructure, the safety assessment of deteriorating structures has emerged as a pressing and critical concern. This study presents an experimental investigation into the combined effects of freeze–thaw cycles (100, 200, and 300 cycles) and corrosion (corrosion ratio: 3% and 10%) on the cyclic behavior of RC beams. Seven RC beam specimens with varying types and levels of deterioration were fabricated, and static tests were conducted using a four-point bending method to assess the behavior of RC beams under each degradation factor. The experimental results revealed that increasing freeze–thaw cycles significantly impact RC beam behavior, leading to intensified crack formation due to cyclical frost-heaving pressure. This ultimately results in reduced yield loads ranging from 3% to 11% and peak loads reduced by 1–2% compared to the reference specimen A-0-0. Corrosion of steel bars in RC beams alters failure modes, with corroded specimens (C-0-3 and C-0-10) experiencing substantial decreases in yield load, a 15% reduction in C-0-3, and a 26% decrease in C-0-10, compared to A-0-0. Displacement at yield load and peak load also decreased, highlighting the detrimental impact of corrosion on beam mechanical properties. The combined deterioration from freeze–thaw cycles and corrosion further exacerbates these reductions, resulting in a substantial decrease in yield load (32%) and peak load (24%) in D-3-10 compared to the reference specimen A-0-0. Additionally, energy dissipation capacity and cumulative energy dissipation capacity exhibit dynamic changes influenced by the progression of freeze–thaw cycles, corrosion, and their combined effects.

Experimental study on seismic behavior of RC beams confined by corroded stirrups

PurposeTo understand the seismic behavior of reinforced concrete (RC) beams confined by corroded stirrups, low-reversed cyclic loading tests were carried out on seven RC beam specimens with different stirrup corrosion levels and stirrup ratios to investigate their mechanical characteristics.Design/methodology/approachThe failure mode, hysteresis behavior, skeleton curves, ductility, stiffness degradation and energy dissipation behavior of RC specimens are compared and discussed. The experimental results showed that the restraint of concrete provided by corroded stirrups is reduced, which leads to a decline in seismic performance.FindingsFor the specimens with the same ratios of stirrup, as the corrosion level increased, the load-carrying capacity, stiffness, plastic deformation capacity and energy-dissipation capacity dropped significantly. Compared with the uncorroded specimen, the failure modes of specimens with high corrosion level changed from ductile bending failure to brittle failure. For the specimens with the same levels of corrosion, the higher the stirrup ratio was, the stronger the restraint effect of the stirrups on the concrete, and the seismic behavior of the specimens was obviously improved.Originality/valueIn this paper, a total of seven full-size RC beam specimens at joints with different stirrup corrosion levels and stirrup ratios were designed and constructed to explore the influences of corrosion levels and stirrup ratios of stirrups on the seismic performances. The failure modes, strain of reinforcement, hysteretic curves, skeleton curves, stiffness degradation and ductility factor of RC specimens are compared and discussed.

Effects of pre-cracked reinforced concrete in compression zone on prefabricated RC beam behavior

Cracks can occur in the compression zone of a beam cross section, in the middle part of the span due to different reasons. For instance, due to accidents happened during transportation of the prefabricated Reinforced Concrete (RC) beams on manufacturing site. In this study, effects of such cracks on the behavior of RC beams are investigated experimentally. Compression strength of concrete and intensity degree of pre-created cracks were adopted as test parameters. A total of eight RC beam specimens were tested under the effect of bending, applying three-point loading. According to the results it was observed that the pre-cracked RC beams had almost the same strength with the reference beams; but bending stiffness of the RC beams decreased when the intensity of the cracks increased relatively.

Seismic Performance of Reinforced Concrete Beams Susceptible to Single-Crack Plastic Hinge Behavior

Following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, a number of reinforced concrete (RC) beams in high-rise structures developed a single primary crack at the beam-column interface without the formation of distributed secondary cracks along the beam length. Detailed assessments showed that these beams have conforming longitudinal steel ratios and the single-crack mechanism may be due to design and/or construction practices for beam-column joints in the 1980s. In order to investigate the seismic behavior of reinforced concrete beams with detailing that inhibited the spread of flexural yielding, an experimental program was carried out on RC beam specimens, having similar reinforcement detailing to that of beams that developed a single crack at their ends during the Kaikoura earthquake to understand their seismic behavior, postearthquake repairability, and residual low-cycle fatigue life. Experimental results showed that the beams were able to undergo significant inelastic drift demands without loss of lateral resistance and have sufficient residual drift capacity following moderate and large earthquake demands. The response of the beam specimens was dominated by hinge rotation via the bond-slip mechanism. Comparisons showed that the measured drift capacities of the beams exceeded the predicted drift capacities computed using state-of-the-practice procedures.

Flexure‐axial‐shear interaction of ductile beams with single‐crack plastic hinge behaviour

AbstractOne of the key damage observations in modern reinforced concrete (RC) frame buildings, damaged following the 2010/2011 Canterbury and 2016 Kaikoura earthquakes, was localised cracking at the beam‐column interface of capacity‐designed beams. The localised cracking in the beams was due to curtailed longitudinal bars at the beam‐column interface. Following these observations, without experimental data to justify desirable seismic performance, modern beams controlled by localised cracking were assumed to be potentially earthquake‐vulnerable. To address this, an experimental program was carried out on six RC beam specimens susceptible to single‐crack plastic hinge behaviour due to curtailed longitudinal bars. The experimental data show that RC beams with single‐crack plastic hinge behaviour can undergo significant inelastic drift demands without loss of lateral resistance. However, contrary to conventional beams with distributed cracking, the response of RC beams with single‐crack plastic hinge behaviour due to curtailed longitudinal bars is mainly dominated by hinge rotation (via bond‐slip) and shear sliding at the column face. The current paper studies the interdependence of axial elongation, bond‐slip and shear sliding deformation of RC beams with single‐crack plastic hinge behaviour under cyclic demands. A procedure for seismic assessment of RC beams with single‐crack plastic hinge behaviour due to curtailed longitudinal bars is proposed. The proposed formulations can be adopted to develop adequate numerical models for simulating the response of RC frames with beams susceptible to single‐crack plastic hinge behaviour due to curtailed longitudinal bars.

Behavior Under Repeated Loading of RC Beams Externally Strengthened in Flexure with SRG Systems

Steel-reinforced grout (SRG) systems are effective methods for the flexural strengthening of reinforced concrete (RC) beams. In this study, the effect of a limited number of repeated loads on the structural response and debonding evolution of strengthened beams was experimentally investigated. The number of available research concerning the cyclic behavior of SRG-strengthened members is quite limited and this research attempts to cover this knowledge. A total of ten full-scale RC beam specimens were tested under a four-point bending scheme. The effectiveness of the traditional externally bonded (EB) strengthening technique was compared with a promising innovative technique referred to as inhibiting/repairing/strengthening (IRS). The test variables included the use of two SRG configurations using high and low steel strip density. The experimental results revealed that the performance of the beams was largely dependent on the spacing of the steel strands within the reinforcing strip. Under repeated loading, the debonding of the external system takes place when steel fiber with high mass per unit of area was used. By increasing the matrix impregnation of the steel strip, the composite system was not affected by debonding. Further, the efficiency in terms of flexure enhancement, local and global ductility performance and energy dissipation of the beams are also discussed.

Effect of early‐strengthening of RC beams using UHPC layers on their performance against reinforcement corrosion

AbstractIn 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.

Shear strengthening of RC beams using FRCM system made with industrial wastes

In the present study, industrial wastes were used as a partial replacement for cement to form cement-based repair mortars, and the feasibility of using these mortars as the matrix in fiber reinforced cementitious matrix (FRCM) system for shear strengthening of reinforced concrete (RC) beam specimens was investigated. Accordingly, an experimental program comprising two parts was carried out. Firstly, the properties of the mortars were examined through compressive strength, tensile strength, sulfuric acid resistivity, and electrical resistivity tests. Finally, 6 shear-critical RC beam specimens were manufactured, two of which remained un-strengthened acting as control specimens. Two specimens were strengthened in shear by carbon fiber reinforced polymer (CFRP) strips and two specimens were strengthened by fiber reinforced cementitious matrix (FRCM) layers made with prepared mortars. The shear capacity of the specimens was measured through 3-point bending test. The parameters investigated in the beam specimens included the effect of shear strengthening system (FRP/FRCM) and shear span/depth ratio. It was shown that the specimens strengthened by the FRCM system made with waste materials had similar or slightly better performance compared to the FRP strengthened specimens.

Flexural performance of pre-damaged RC beams strengthened with different configurations of UHPFRC layer –experimental and analytical investigation

This paper reports a study comprising both experimental and analytical works to capture the flexural behavior of pre-damaged reinforced concrete (RC) beams strengthened with different configurations of ultra-high-performance fiber-reinforced concrete (UHPFRC) layers on the beam’s surface. Firstly, a selected mixture of normal concrete and steel reinforcing bars (both used for casting the RC beams) and a selected mixture of UHPFRC (used for strengthening the RC beams) were characterized, followed by preparing 14 RC beam specimens. While one RC beam was used as a control specimen, the other 13 beams were pre-damaged to three levels by applying flexural loads corresponding to 30, 75, and 90 % of the ultimate flexural load-bearing capacity of the control RC beam. The pre-damaged RC beams were strengthened by applying 30 mm-thick UHPFRC layer(s) to their surface(s) using three different strengthening configurations that included a tensile surface, two vertical surfaces, and three surfaces (tensile and two verticals). The strengthened beams were subjected to flexural loading, and the data pertaining to load versus deflection and strain in reinforcing bars were recorded until the failure. While no changing in the pattern of the strain development in reinforcing steel bars and the mode of failure of the strengthened beams were observed, their flexural performance was significantly affected by their degree of pre-damaging and the strengthening configuration. The strengthened RC beams pre-damaged by 30 % showed significantly higher enhancement in the load-bearing capacity than the strengthened RC beams pre-damaged by 75 and 90 % because of the fact that the steel reinforcement in strengthened RC beams with a pre-damage of 30 % did not yield before strengthening, contrary to the beams pre-damaged by 75 and 90 % in which the steel reinforcement bars yielded during the damaging process before strengthening and therefore the steel reinforcement had insignificant contribution in improving the flexural performance after strengthening. The three-sided, two-sided, and one-sided UHPFRC strengthened RC beams showed the highest to the lowest enhancement in the flexural performance. The analytical models were derived to predict the ultimate load-bearing capacities of the strengthened RC beams for all three UHPFRC jacketing configurations. Results obtained using the developed analytical models matched very well with the corresponding experimental results.

Effect of industrial waste metal chips on flexural behavior of re-inforced concrete beams

Recycling waste and by-products are necessary for environmentally friendly production and reducing carbon footprint. It is possible to use waste materials as additives and admixtures to improve the strength, ductility, and toughness of the reinforced concrete (RC) elements. Industrial waste metal chips have a high potential to be used as an admixture which improves the general behavior of RC elements, as proven by preliminary studies. In this study, various industrial waste metal chips were added into concrete as an admixture in different sizes and proportions to experimentally investigate the effect on the flexural strength of RC beams. Five RC beam specimens with identical dimensions and different metal chip waste admixtures were cast for the experiments. The load-displacement behavior of beams was examined by conducting a three-point bending test. As a result, it has been observed that the use of waste metal chips can significantly increase the flexural strength and ductility of the beams. The maximum load of one specimen with steel chip admixture is found to be 1.75 times higher than the waste-free reference beam. It is concluded that the usage of waste metal chips as an admixture is a viable solution to enhance the flexural behavior of the RC beams.

Finite element analysis of bond behavior in corroded reinforced concrete beams: State-of-the-art

The article conducts a comprehensive examination of various aspects related to rebar corrosion, encompassing the corrosion mechanism, its implications on design criteria, the modeling of bond interfaces under both corroded and non-corroded conditions, and the modeling of reinforced concrete (RC) beams affected by corrosion, employing both empirical and analytical methodologies. The initial stages of corrosion instigate a gradual transformation of rebar into rust. One notable consequence of reinforcement corrosion is the generation of expansive pressure, leading to concrete cracking, spalling, and detachment of the concrete cover. Additionally, it diminishes the effective cross sectional area of the rebar, ultimately resulting in a decline in the concrete's bond strength and gradual structural deterioration. Ultimately, continuous corrosion can lead to a complete loss of bond between the concrete and rebar, representing the most severe form of damage attributable to corrosion. This poses a critical threat, particularly in cases where the beam functions as an unreinforced structure, potentially culminating in sudden structural failure. This paper primarily underscores the utilization of the Finite Element Method (FEM) for evaluating the impact of bond deterioration between concrete and reinforcement caused by corrosion. The paper effectively employs this technique to predict and analyze the structural damage in corroded RC beam specimens.

Carbonation depth model for loaded reinforced concrete (RC) beams under time-dependent relative humidity conditions

Steel bar corrosion caused by concrete carbonation is one of the important factors of the durability failure of reinforced concrete (RC) structures. The annual relative humidity (RH) in the upper reaches of the Yangtze River shows obvious time-dependent characteristics. The important wharf components represented by RC beams bear flexural loads during their long-term service. The carbonation of RC structures under the coupling of the service environment and flexural load is very complicated. However, corresponding studies on the carbonation of loaded RC structures are mostly carried out in a constant RH environment, which is quite different from the time-dependent RH (T-RH) conditions in the upper reaches of the Yangtze River. For this study, the RC beam of a wharf in the upper reaches of the Yangtze River is treated as the research object. According to the long-term observation data of the 24-year daily mean RH at this wharf site, the periodic (time-dependent) characteristics of RH in a typical year are obtained by statistical analysis. On this basis, a physical experiment for RC beam specimens subjected to flexural loads under an accelerated carbonation environment with T-RH is carried out to explore the influence of the coupling effect of the T-RH and flexural load on the concrete carbonation behaviour. The results showed that the range of RH is basically distributed from 45 to 95%, and the monthly mean RH over a typical year shows a 'W'-shaped periodic characteristic. The compressive strength and concrete carbonation depth under the T-RH environment are larger than those under the C-RH carbonation environment; hence, the carbonation degree of concrete under a T-RH environment is more serious. When the flexural load level is less than 1.0, the flexural tensile stress can accelerate the carbonation degree of RC specimens, and the carbonation depth of concrete is positively correlated with the flexural load level. When the flexural load does not reach the concrete compressive strength, the flexural compressive stress can inhibit concrete carbonation. Based on the experimental measurements, the carbonation depth model for loaded RC beams under the T-RH is established, and the accuracy of the model is verified by the original test data collected during 27 years of the natural carbonation of RC beams. Through the studies and achievements presented in this paper, the carbonation trends of loaded RC beams under T-RH are revealed, and the corresponding mathematical model is established, which can be used to evaluate the carbonation depth of loaded RC beams considering T-RH in general atmospheric environments. The research results can provide a basis for RC structure durability evaluation in the upper reaches of the Yangtze River and have important guiding significance for practical engineering.

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

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

Damage assessment of reinforced concrete structures under elevated-amplitude cyclic loading using sentry values based on acoustic emission testing

ABSTRACT This article reports the combined application of sentry value and the Gaussian Mixture Modeling (GMM) algorithm to study crack classification in reinforced concrete (RC) beams using acoustic emission (AE) testing. The AE generated from RC beam specimens subjected to elevated-amplitude cyclic loading was used to study crack classification. The specimen approaches yielding, followed by a structural failure, when AE hits linked with shear cracks begin to exceed AE hits associated with tensile cracks. The sentry value for RC beam specimens decreased with subsequent higher amplitude loading phases, indicating the formation of macrocracks. The Kaiser effect phenomenon in RC beams was observed. The yielding of steel rebars and subsequent collapse of the RC beam specimens, followed by unstable crack propagation, were identified using the zero-slope line and a vertical spike in the sentry value versus the time graph. The current study appears to be significant for damage assessment and crack classification of in-situ RC flexural members.

Finite Element Modelling of Corrosion-Damaged RC Beams Strengthened Using the UHPC Layers.

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

Experimental and analytical study on the effect of different repairing and strengthening strategies on flexural performance of corroded RC beams

This paper reports the results of a study conducted to investigate the flexural behavior of corroded reinforced concrete (RC) beams that were first repaired with different types of cover repairing materials and then strengthened with the carbon fiber-reinforced polymer (CFRP) laminates. Thirteen RC beam specimens were prepared. One specimen was used as a control beam (un-corroded, unrepaired, unstrengthened), and the reinforcing bars in twelve specimens were corroded using an accelerated corrosion setup. While five corroded specimens (two unrepaired and three repaired) were tested without strengthening using CFRP laminates, the other seven corroded specimens (two unrepaired and five repaired) were strengthened with one and two layers of CFRP laminates before testing under flexure. For the RC beams subjected to 10 and 20% corrosion of steel bars (by mass), strengthening using one layer of CFRP laminate enhanced the load-bearing capacities by 89 and 73%, respectively, while strengthening with two CFRP layers improved the load-carrying capacity by 162 and 154%, respectively. Repairing the damaged cover of the corroded RC beams using ultra-high-performance concrete (UHPC) was found to be most effective in enhancing the load-bearing capacity and stiffness, whether the corroded beams were strengthened with CFRP laminates or not. Repairing of the cover using commercial repair material also enhanced the load-carrying capacity and stiffness, with ductility more than that of UHPC. Strengthening of the corroded beams further improved the load-carrying capacity. An analytical model was developed that can predict the load-bearing capacity of the beams with a fair degree of accuracy.

Strategies for strengthening of corroded reinforced concrete beams using CFRP laminates and UHPC jacketing

AbstractThis 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.

Curvature-enabled analytical method for bending-induced crack location prediction

Condition assessment of civil infrastructure damaged by naturaldisasters with insufficient structural information has been a challenge for engineers. This paper proposes an analytical method to predict bending-induced crack locations on damaged reinforced concrete (RC) beams merely using curvature characteristics obtained from vision-based technologies. Firstly, critical equations that calculate minimum crack spacing followed by bending curvature information are derived through bond-slip theory and assumed boundary conditions. Secondly, a prediction procedure is proposed using derived critical equations to determine bending-induced crack locations. Two RC beam specimens under four-point bending were investigated to verify the validity and accuracy of the proposed method. Experimental results show that the combination of vision-based technologies and the analytical method proposed in this research has great potential in structural inspection and safety evaluation in field.