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Shear strengthening of reinforced concrete beams using near-surface mounting (NSM) method with fiber-reinforced polymer (FRP) strips is more effective because of improved bond strength, better fire resistance and high maintainability. However, the surface preparation for NSM method is a difficult process where the beam–slab corner is not accessible by the rotary blade of the groove-making equipment. Consequently, the application of NSM method becomes more difficult to apply. Therefore, in this study, the effect of reducing in NSM length on the shear strength has been investigated by reinforcing only a part of the height, not the entire web of beam, referred to as the partial-length NSM method (PLNSM). Half scaled five RC T-beams were made and tested under symmetrical four-point static loading system. All except one was strengthened in shear in which the effect of reduced NSM length was balanced by inclining the partial-length NSM strips (IPLNSM). Furthermore, to mitigate the detrimental effect of reduced lengths of NSM strips, the retrofitting was enhanced by additional externally bonded reinforcement (EBR) method using CFRP sheets. The results showed that there was no significant negative effect of reduced NSM length on the strength of the strengthened specimens, and by providing inclined NSM strips, significant improvement in the strength was observed. Additionally, the hybrid approach combining the inclined partial length NSM (IPLNSM) and EBR method showed improvement in strength and deflection capacity. Lastly, when compared with the currently available design procedures, it was found that the available formulation can predict the design strength of PLNSM and IPLNSM reinforcement, thus making them a viable option for retrofitting reinforced concrete beams. [ABSTRACT FROM AUTHOR]

In this study, shear-critical reinforced concrete (RC) beams were strengthened by combining the prestressing and near-surface mounted (NSM) rods approaches. The potential danger of failure in such RC beams is a substantial concern as it is considered a potential threat. This study addresses its careful mitigation through experimental identification and numerical analysis to enhance the safety and sustainability of buildings by reducing the probability of failure risk for these RC beams. Nine of the ten RC beams that were tested had strengthened, and one had not. Internal prestressing (IP) within the beam body, external prestressing NSM (PNSM), internal embedment (IE) inside the beam with or without prestressing, and NSM are the strengthening technologies that were employed. The range of the extra shear reinforcement ratios (μs) was 0.87% to 1.60%. We investigated how strengthened beams behaved structurally in terms of the cracking load, ultimate load, load–deflection response, ultimate deflection, and stiffness. The insertion of five pairs of PNSM rods (μs = 1.45%) and five pairs of IP rods (μs = 1.6%), respectively, increased the beams' shear capacity by 57.8% and 70.4%. Shear capacity increased by 23.2% when three pairs of IE rods (μs = 1.02%) were installed. The prestressing location had an impact on shear capacity, with the interior case surpassing the external one. Compared to the control, the stiffness of the strengthened beams rose by 20%, 82%, and 84.4% when three, four, or five pairs of internal prestressing rods were added. A formula is proposed to calculate the shear capacity of all beams strengthened using various methods. [ABSTRACT FROM AUTHOR]

Predicting the shear resistance of reinforced concrete (RC) beams strengthened with externally bonded reinforcement using carbon fiber–reinforced polymer (CFRP) materials poses a significant challenge due to the complex nonlinear relationship with beam features and the inherent randomness in shear failure events, driven by their brittle nature. This paper proposes a model employing a multiobjective optimization technique that both, enhances the accuracy and ensures unbiased predictions. To highlight the achieved improvement, a comparison is made between the performance of the proposed model and a series of well-established models in the literature. The proposed model presents superior predictive performance and a smaller coefficient of variation in the model error distribution than the models in the literature. In addition, it exhibits unbiased predictions, highlighting the advantages of incorporating multiobjective optimization. Furthermore, a modified demerit point classification is introduced and applied to all models, highlighting the superiority of the proposed model in producing more reliable and cost-effective predictions. [ABSTRACT FROM AUTHOR]

This paper evaluated the structural behavior of shear-strengthened externally bonded FRCM composites. The additional shear strength of FRCM composites with three different types of textile grids (T1, T2, and T3) was analyzed for different crack patterns and failure modes. The influence of the internal transverse reinforcement ratio (ρw: 0.19%, 0.285%) and application method (SB: side bonding; UW: U-type wrapping) on the FRCM-strengthened beam was investigated. Furthermore, the interaction of FRCM composites with internal shear reinforcement was analyzed based on the strain distributions measured in the experiments. The experimental results showed that the failure modes (flexural, shear slippage, and shear debonding) changed depending on the type of textile grid applied. A reduction in shear reinforcement strain (interaction) due to FRCM strengthening was observed for all the strengthened beams, with differences depending on the shear reinforcement ratio and the type of textile grid. In addition, the ratio of the strain measured at the ultimate load to the strain of the textile grid in shear-failed reinforced beams was the lowest for the T3 grid, which had worse physical properties, and increased at lower shear reinforcement ratios. However, application methods (SB, UW) did not show significant differences. [ABSTRACT FROM AUTHOR]

In this article, an unprecedented fracture mechanics-based bond model for embedded through-section (ETS) fibre-reinforced polymer (FRP) bars installed in concrete blocks is proposed. Various methods have emerged for rehabilitating substandard and deteriorated concrete structures. The ETS FRP bar method provides numerous advantages over existing shear strengthening methods, but no reliable and comprehensive bond–slip model exist to predict the method's bond behaviour. In this study, a state-of-the-art analytical bond model is derived for determining the debonding force of the ETS FRP bars from concrete blocks using a newly proposed bi-linear bond–slip relationship that is expressed as a function of the maximum shear stress and its corresponding slip. The accuracy of the results predicted by the proposed model is verified with the existing push–pull data of ETS FRP/concrete joints in the literature. The results show that the newly proposed model can be used for both carbon FRP (CFRP) and glass FRP (GFRP) ETS bars with an average Pexp/Pmax ratio of 1.04 with superior statistical accuracy measures when compared to the existing bond models' predictions. [ABSTRACT FROM AUTHOR]

The potential for recovering the shear capacity of heat-damaged beams using carbon-fibre-reinforced polymer (CFRP) ropes was investigated using 12 concrete beams (150 × 250 × 1450 mm3) with shear reinforcement deficiency. Six beams were heated for 2 h at a temperature of 400°C; the others were not heated. All the beams were retrofitted with near-surface mounted CFRP ropes as external U-shaped stirrups, inserted in vertical holes (embedded through reinforcement) or implemented as a hybrid system of both. Lateral dowels were implanted in concrete along with schemes involving U-shaped stirrups to improve resistance against cover separation and shear failure, respectively. The mechanical behaviour of the beams was evaluated under three-point loading, with data collected and analysed to characterise the load–deflection relationships. Cracking and failure modes were analysed. For the heat-damaged beams, the adopted schemes restored load capacity and improved toughness and ductility, but not flexural stiffness. Moreover, implementing ropes as U-shaped external stirrups, terminating 20 mm below the top surface of the beams, helped avert side-cover separation, yet resulted in horizontal shear failure at the level of the upper concrete cover of the damaged beams. The residual strain induced in the U-shaped external stirrups was 14–40%, which is compatible with those reported in other works adopting similar repair methodologies. [ABSTRACT FROM AUTHOR]

This study experimentally assessed the shear performance of reinforced concrete (RC) beams strengthened with U-shaped High-Performance Fibre-Reinforced Concrete (HPFRC) under static and fatigue loading. Key parameters included HPFRC jacket thickness and beam shear span–depth (a/d) ratio. Five beams were tested under static loads to determine ultimate shear strengths, followed by fatigue tests on identical beams at 30–70% of ultimate shear strengths at 4 Hz. In static loading experiments, all the HPFRC jacketing proved effective, increasing the shear strength of RC beams by 95% to 130%. Although the strengthening system did not change the failure mode of the beams, the strengthened beams exhibited pseudo-ductile behaviour. As the a/d increased, the shear enhancement capability of the HPFRC jackets decreased. In fatigue loading experiments, all the HPFRC systems improved the fatigue life of RC beams. Specifically, in beams with an a/d ratio of 2.0, the fatigue life was extended from 75 cycles to a maximum of 951 cycles, while in beams with an a/d ratio of 3.5, it increased from 12,525 cycles to 48,786 cycles. In addition, a predictive model has been developed for the fatigue life of HPFRC/UHPFRC shear-strengthened beams, utilising the maximum fatigue load and the design's ultimate shear strength under static loading conditions. [ABSTRACT FROM AUTHOR]

In this study, the effectiveness was investigated of shear strengthening techniques in reinforced concrete (RC) deep beams incorporating stainless steel plates (SSPs). Four RC deep beams were tested under incremental static loading until failure to examine the proposed strengthening techniques. The key parameters considered in this study included the arrangement of the externally bonded SSPs. The experimental findings demonstrated that strengthening using SSPs led to substantial improvements in their performance compared to the unstrengthened control beam. The use of SSPs increased the ultimate shear capacity by 129 to 175% over the control specimen. Finite element models (FEMs) were developed to simulate the responses of the tested beams strengthened using SSPs. Parametric studies were then conducted using the validated FEM to investigate to identify the effects of the area of SSPs on the shear capacity of the beams. The parametric studies concluded that increasing the plate thickness resulted in the enhanced shear capacity of the deep beam specimens up to a critical point upon which the increases in the thickness have insignificant effects on the shear strength. The accuracy of the design equations given by European and American codes in predicting the shear strength of the deep beams is examined. [ABSTRACT FROM AUTHOR]

Abstract Shear strengthening of reinforced concrete beams using near-surface mounting (NSM) method with fiber-reinforced polymer (FRP) strips is more effective because of improved bond strength, better fire resistance and high maintainability. However, the surface preparation for NSM method is a difficult process where the beam–slab corner is not accessible by the rotary blade of the groove-making equipment. Consequently, the application of NSM method becomes more difficult to apply. Therefore, in this study, the effect of reducing in NSM length on the shear strength has been investigated by reinforcing only a part of the height, not the entire web of beam, referred to as the partial-length NSM method (PLNSM). Half scaled five RC T-beams were made and tested under symmetrical four-point static loading system. All except one was strengthened in shear in which the effect of reduced NSM length was balanced by inclining the partial-length NSM strips (IPLNSM). Furthermore, to mitigate the detrimental effect of reduced lengths of NSM strips, the retrofitting was enhanced by additional externally bonded reinforcement (EBR) method using CFRP sheets. The results showed that there was no significant negative effect of reduced NSM length on the strength of the strengthened specimens, and by providing inclined NSM strips, significant improvement in the strength was observed. Additionally, the hybrid approach combining the inclined partial length NSM (IPLNSM) and EBR method showed improvement in strength and deflection capacity. Lastly, when compared with the currently available design procedures, it was found that the available formulation can predict the design strength of PLNSM and IPLNSM reinforcement, thus making them a viable option for retrofitting reinforced concrete beams.

This study aimed to evaluate the shear strengthening capabilities of reinforced concrete (RC) shallow beams constrained by externally bonded glass chopped strand mat (GCSM) sheets and metallic mechanical anchors. The research investigated the effectiveness of GCSM sheets, known for their cost-effectiveness, ease of installation, and absence of specialized labor requirements, in improving the shear capacity, energy dissipation, and deformation capacity of RC beams. Experimental results revealed that GCSM sheets significantly enhanced the deformation capability, ultimate shear strength, and energy dissipation of RC shallow beams. Beams with GCSM applied to both the sides and bottom (SB) configuration demonstrated higher load-bearing capacity and energy dissipation compared to beams with GCSM only on the sides. The incorporation of a metallic mechanical bolt anchorage (MBA) system reduced the load-carrying capacities of beams with SB and beams with GCSM applied to only side by 28% and 5%, respectively, due to the drilling required for installation. However, the MBA system significantly improved the deflection performance, with beam B-S-A (GCSM on sides only and supplemented with MBA exhibiting the highest ultimate deflection of 23.92 mm. Overall, beams equipped with the MBA system showed superior ultimate deflection compared with those without it. Despite some reductions in load-bearing capacity, GCSM sheets combined with MBA systems proved highly effective in enhancing the shear strength, energy dissipation, and deformation capabilities of RC shallow beams, making them a valuable alternative for shear strengthening applications.

AbstractAs CFRP (carbon fiber-reinforced polymer) offers high retrofit efficiency for structural members in bending and shear due to its superior mechanical properties compared to steel, sheets made from this material have become ubiquitous in strengthening existing reinforced concrete (RC) structures. However, there needs to be more research on RC beams with no stirrups that have been shear-strengthened with side-bonded CFRP sheets. As such, this study aims to investigate this specific topic and assess design-related parameters that impact the load-bearing capacity of these shear-strengthened beams. To achieve this, nonlinear finite element models of four RC beams, including one control beam and three beams strengthened with side-bonded CFRP sheets, were built and verified regarding shear capacity, crack patterns, and failure mechanisms. The simulated beams demonstrated a high level of accuracy in all mentioned aspects. Numerical models were then developed to evaluate the design-oriented parameters that affect the response of shear-strengthened beams, including the concrete compressive strength, the amount of steel reinforcement, the number of CFRP layers, the CFRP bonding configuration, and the shear span-to-effective depth ratio. The results showed that not only the compressive strength of the concrete but also the amount of steel longitudinal reinforcement had a significant relationship with the load-bearing capacity of shear-strengthened beams. Meanwhile, the bonding configuration and the layer number of side-bonded CFRP sheets considerably influenced the ductility, the crack pattern, and the failure mode of shear-strengthened beams. [ABSTRACT FROM AUTHOR]

This research systematically compares the effectiveness of Carbon Fiber-Reinforced Polymer (FRP) and Fabric-Reinforced Cementitious Matrix (FRCM) in shear strengthening of reinforced concrete (RC) deep beams featuring web openings. Through a comprehensive experimental program, six RC beams were subjected to shear tests, considering variations in the number of layers for both FRCM and FRP, employing a U-wrapping configuration. Recorded parameters include load-deflection curves, ultimate strength, cracking patterns, failure modes, and strains in steel bars, allowing a comprehensive comparison between strengthened and un-strengthened RC beams. The study compares observed shear strengths from experiments with shear capacities predicted by proposed models for RC beams strengthened with FRCM and FRP, following codes such as ACI 440.2R-17, CSA S806-12, Eurocode 2, and ACI 549.4R-20. Increasing layers enhanced shear strengths and post-elastic stiffness. The presence of substantial openings led to early shear cracks and reduced strength. CFRP improved shear strength by 13.99% (1-layer) and 18.12% (2-layer), while FRCM strengthened layers by 20.2% (1 layer) and 29.3% (2 layers). FRCM outperformed in strength and stiffness, while FRP excelled in ductility and concrete confinement. Experimental and calculated results varied based on ACI, CSA, and Eurocode, with ACI providing consistent and accurate results. CSA's calculation surpassed experiments, emphasizing its consideration of effective fabric design strain. [ABSTRACT FROM AUTHOR]

The existing Reinforced Concrete (RC) buildings stock is often characterized by a significant seismic vulnerability, due to the absence of capacity design principles, even in regions with high seismic hazard, such as Italy. Approximately 67% of existing RC buildings in Italy have been designed without considering seismic actions (GLD), resulting in very low transverse reinforcement amount in beams and, particularly, in columns. Additionally, beam-column joints typically totally lack stirrups. Consequently, shear failures under seismic actions are very likely for this pre-code building typology, often limiting their seismic capacity. However, the assessment of shear failures in beams/columns or joints varies significantly from code to code worldwide. The main goal of this work is to quantify the impact of different code-based brittle capacity models on the seismic capacity assessment and retrofit, focusing on GLD Italian pre-1970 RC buildings. This comparative analysis is carried out by first considering three current codes, emphasizing their, even significant, differences: European (EN 1998-3-1. 2005), Italian (D.M. 2018), and American (ASCE SEI/41 2017) standards. Then, shear capacity models prescribed by the current drafts of the next generation of Eurocodes are implemented and compared to the current models. The assessment includes: (i) a parametric comparison among models; (ii) the evaluation of case-study buildings capacity in their as-built condition and after shear strengthening interventions. The latter is performed on 3D "bare" models, due to the lack of practical guidance in most codes on modelling masonry infills. [ABSTRACT FROM AUTHOR]

This study presents an experimental investigation on the contribution of carbon fiber-reinforced polymer (CFRP) sheets in shear-strengthened beams with different strengthening schemes. Three different reinforcement types and strengthening schemes are applied (U-shaped, U-shaped with additional anchorage and fully-wrapped). The strength contribution of FRP sheets, internal stirrups, and concrete are estimated based on experimental data. Two different anchoring strategies to prevent the FRP strengthening from debonding were also present, using horizontal strips of FRP and rebars on grooves on the web of the beams. The behavior of each of the beams is discussed in terms of loaddisplacement, failure mode, strains distribution, cracking pattern, and shear force contribution. The influence of the strengthening configuration and FRP anchorage on the FRP shear contribution and total shear resistance is discussed based on the experimental. The individual contribution of FRP, stirrups and concrete are estimated based on strain data from the tests. Finally, the experimental shear capacity is compared to the recommendations of ACI 440.2R, and fib Bulletins 14 and 90. [ABSTRACT FROM AUTHOR]

This paper presents the results of a study that investigates the mechanisms of shear resistance in reinforced concrete (RC) beams that are shear-strengthened with engineered cementitious composites (ECCs) and fiber-reinforced polymer (FRP). The ECC FRP utilizes ECC as the bonding agent between the FRP and concrete and the FRP as the high-strength reinforcement. The test program was divided into three groups: (1) 15 dog-bone shaped ECC FRP coupons; (2) 27 ECC FRP push-off blocks; and (3) two ECC FRP shear-strengthened RC beams 125 mm wide, 300 mm high, and 2,640 mm long. Groups 1 and 2 aimed at investigating the uniaxial tension and push-off behavior, respectively, by simulating the crack separation and sliding mechanisms. These mechanisms are fundamental to understanding the shear resistance of the ECC FRP and are characterized by the applicable tensile stress–strain and shear stress–sliding laws. The embedded FRP mesh in the ECC FRP composites significantly enhances the crack sliding that is required for shear strength development, with a minimal impact on the tensile and shear strengths. In addition, the precrack width reduced the shear strength of the ECC FRP. Group 3 aimed to investigate the shear behavior of the ECC FRP beams. The crack width and sliding were monitored during loading, which provides insights into the shear contributions from the concrete, steel stirrups, and ECC FRP. The results reveal a major shift in the shear capacity contribution from the concrete to the ECC FRP in the strengthened beams, which led to a substantial shear improvement. The contributions of the ECC FRP to shear resistance by crack separation and sliding were comparable throughout the loading process. The FRP meshes in the ECC FRP composites effectively limited deformation, maintained structural integrity, and redistributed the shear capacity from the ECC FRP to concrete. [ABSTRACT FROM AUTHOR]

This paper investigates, experimentally and numerically, the shear strengthening of Normal Concrete (NC) beams using post-tensioning steel bars and Engineered Cementitious Composite (ECC) reinforced with chemically cured Palm Fronds (PFs). The benefits of strain-hardening ECC and the tensile strength of PFs cured with 6% wt Alkali NaOH solution beside post-tensioned bars have been employed herein. Seven full-scale Reinforced Concrete (RC) beams were fabricated and experimented with under three-point loading until failure. The test parameters include the strengthening technique, type, and configuration of the material used for strengthening. The strengthening process has been implemented through two techniques: Externally Bonded Reinforcement (EBR) and Near-Surface Mounted (NSM) Reinforcement. The strengthening materials have been configured and placed in horizontal, vertical, and inclined positions. The effectiveness of the strengthening methods has been evaluated by examining their cracking propagations, load-deflection responses, collapse modes, elastic stiffness, and absorbed energy. It was found that the proposed strengthening systems could significantly control the crack pattern and failure mode, and they could enhance the ultimate load amplitude up to 37% and 50% for NSM ECC with PFs and EBR post-tensioning steel bars, respectively. Nonlinear three-dimensional finite element models of the tested beams were developed and validated with the test data, where it was found that finite element models predict the structural performance of tested beams with a maximum error of only 2%. [ABSTRACT FROM AUTHOR]

AbstractThis paper showcases shear testing conducted on seven reinforced concrete deep beams featuring square openings, aimed at demonstrating the efficacy of a shear strengthening approach utilizing textile-reinforced concrete (TRC). This experimental program researches two types of openings of 150 × 150 mm and 200 × 200 mm at the centre of the shear spans. The solid beam undergoes testing for comparison with both the unstrengthened and strengthened beams containing openings. The study evaluates the effectiveness of TRC through a comparison of load-displacement curves, cracking patterns, and strains in reinforcements between the strengthened and un-strengthened beams. The experimental results indicate that the TRC strengthening technique effectively boosts the shear-carrying capacity of beams. Examination of the tested beams reveals a significant enhancement in stiffness at the point of maximum force, with improvements ranging from 22% to 86%, depending on the opening size and the number of reinforced textile layers. Rupture in TRC and crushing in the concrete strut are observed in the strengthened beams, whereas the un-strengthened beams show severe crushing in concrete at failure. The test results are compared with calculations based on code provisions, revealing that the prediction model consistently yields values 11 to 44% higher than the experimental results. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the shear strengthening capabilities of reinforced concrete (RC) shallow beams constrained by externally bonded glass chopped strand mat (GCSM) sheets and metallic mechanical anchors. The research investigated the effectiveness of GCSM sheets, known for their cost-effectiveness, ease of installation, and absence of specialized labor requirements, in improving the shear capacity, energy dissipation, and deformation capacity of RC beams. Experimental results revealed that GCSM sheets significantly enhanced the deformation capability, ultimate shear strength, and energy dissipation of RC shallow beams. Beams with GCSM applied to both the sides and bottom (SB) configuration demonstrated higher load-bearing capacity and energy dissipation compared to beams with GCSM only on the sides. The incorporation of a metallic mechanical bolt anchorage (MBA) system reduced the load-carrying capacities of beams with SB and beams with GCSM applied to only side by 28% and 5%, respectively, due to the drilling required for installation. However, the MBA system significantly improved the deflection performance, with beam B-S-A (GCSM on sides only and supplemented with MBA exhibiting the highest ultimate deflection of 23.92 mm. Overall, beams equipped with the MBA system showed superior ultimate deflection compared with those without it. Despite some reductions in load-bearing capacity, GCSM sheets combined with MBA systems proved highly effective in enhancing the shear strength, energy dissipation, and deformation capabilities of RC shallow beams, making them a valuable alternative for shear strengthening applications. [ABSTRACT FROM AUTHOR]

The hybridisation of fibre-reinforced polymers (FRPs), particularly with the combination of natural and synthetic fibres, is a prominent option for their development. In the context of the construction industry, there is a notable gap in research on the use of jute and glass fibres for the strengthening of concrete structures. This paper presents comprehensive experimental results from tests on seven reinforced concrete (RC) beams strengthened for shear using synthetic, natural, and hybrid jute–glass FRP composites. The beams were reinforced using the externally bonded reinforcement (EBR) technique with U-wrap bonding. A beam without any strengthening was tested and set as a reference for the other beams. Two beams were tested with synthetic FRP shear strengthenings, one with carbon fibre-reinforced polymer (CFRP) and another with glass fibre-reinforced polymer (GFRP). The remaining tests were on RC beams strengthened with natural jute fibre-reinforced polymer (JFRP) and hybrid jute–glass FRP. The paper discusses the experimental behaviour of the tested beams in terms of vertical displacements, crack widths, and strains on steel bars, concrete, and FRP. The experimental strengths are also compared with theoretical estimates obtained using ACI 440.2R and fib Bulletin 90. The tests confirm the effectiveness of natural jute FRP and jute–glass hybrid FRP as an option for the shear strengthening of reinforced concrete beams. [ABSTRACT FROM AUTHOR]

This paper presents an experimental investigation of the use of composite polymer mortar (CPM) and steel strands wire mesh (SSWM) to strengthen reinforced concrete (RC) beams in shear. In order to maximize the shear resistance of the steel strands, a new type of anchor device called wedge‐shaped steel plate hoops (WSSPHs) was developed. And the study aimed to examine the effect of shear‐to‐span ratio and prestressing level on the mechanical properties of the beams. A total of nine beams were constructed and tested under four‐point bending monotonic load, comprising three control beams and six strengthened beams. The study analyzed the damage modes, load‐deflection curves, strength, stiffness, and ductility of the beams. The test results indicated that (1) the mechanical properties of the strengthened beams were improved, with the shear capacity improving by 38.47%–71.37% after strengthening. (2) It was observed that SSWM could be utilized more effectively in high shear‐to‐span ratio beams among the strengthened beams with the same prestressing level. (3) Additionally, the larger prestressing level was found to change the design damage mode of the test beams, with RB‐2.5‐0.5 failing in bending. Finally, a model was proposed to predict the shear capacity of the test beams based on the specification GB 50011‐2010. The model considered the effect of the initial prestressing of the steel strands. [ABSTRACT FROM AUTHOR]

This research studies shear strengthening performance for Normal Concrete (NC) beams employing Engineered Cementitious Composite (ECC) reinforced with Galvanized Welded Wire Mesh (GWWM) in conjunction with/without a prestressing system. Six full‐scale Reinforced Concrete (RC) beams were experimented under static monotonic loading at critical shear span zone up to collapse. The investigated factors were: the type and technique of strengthening, materials used for strengthening, and size and configuration of shear reinforcement. Two techniques were introduced: ECC layer reinforced with GWWM and pretensioned steel bars recovered by ECC with one GWWM. GWWM with and without pretensioned steel bars were delivered as shear reinforcement for strengthening. Vertical and inclined steel bars were the two configurations selected for the prestressing technique for suppressing shear stress. The study was discussed through the experimented beams' crack load and pattern, collapse mode, elastic stiffness, absorbed energy, initial cracking load, and ultimate load, along with the corresponding defection. Experimental results showed that both exploited techniques could govern crack patterns, enhance the failure mode, and upgrade ultimate loading capacity up to 52%. Finite element models were built up, simulating those strengthened with an ECC covering layer augmented with GWWM extracting a model with an error of about 3%. [ABSTRACT FROM AUTHOR]

This paper presents an experimental shear test performed to investigate the web‐shear capacity of composite hollow‐core slabs (HCS) with cast‐in‐place (CIP) concrete. Five HCS specimens are fabricated, and the presence of a topping slab and number of cores strengthened by core‐filling concrete are set as key test variables. The shear force–displacement responses of the specimens, patterns of cracks occurring in the HCS and filled cores, strain behavior of stirrups, and composite action between the HCS and CIP concrete are measured and analyzed comprehensively. In addition, the web‐shear capacity of the composite HCS with CIP concrete is calculated based on elasticity theory and the transformed area method, in which the residual stress ratio factor is introduced to reflect the shear contribution of the core‐filling concrete after its shear cracking. Moreover, a practical equation is proposed to allow structural engineers to easily perform the shear‐strengthening design of HCS via the core‐filling method. The detailed model and the simplified equation accurately evaluate the web‐shear capacities of the HCS specimens. [ABSTRACT FROM AUTHOR]

A novel cost-effective secondary hardening ultrahigh-strength steel, strengthened by the co-precipitation of M2C and NiAl, was developed. The present study systematically investigated the co-precipitation evolution, austenite reversion, and mechanisms of strengthening and toughening at different ageing temperatures. As the ageing temperature increased, the quenched microstructure underwent various transformations, including precipitation and dissolution of cementite, nucleation and coarsening of M2C and NiAl nanoparticles, as well as reversion of austenite. At ageing temperatures of 427 °C and 454 °C, a small amount of cementite was present in the martensite matrix, and M2C and NiAl precipitates started to form, resulting in low strength and poor toughness. At 482 °C, the peak-ageing stage was reached, achieving a maximum yield strength of 1875 ± 4 MPa and an ultimate tensile strength of 2185 ± 3 MPa. This strength is primarily attributed to shear strengthening of NiAl particles and Orowan strengthening of M2C carbides. Additionally, the complete dissolution of cementite at this stage improved toughness. As the ageing temperature increased to 510 °C and 538 °C, the strength decreased due to coarsening of M2C, while the toughness improved as a result of film austenite reversion and enhanced dislocations bypassing around the M2C carbides.

I-shaped concrete girders are widely used in precast bridge and roof construction, making them a common structural component in existing infrastructure. Despite well-established strengthening techniques using various innovative materials, such as externally bonded carbon fibre reinforced polymer (CFRP) reinforcement, the shear strengthening of an I-shaped concrete girder is not straightforward. Several research studies have shown that externally bonded CFRP reinforcement might exhibit early debonding at the concave corners of the I-shape, resulting in a marginal increase in shear capacity. This research study aims to assess the performance of two different CFRP shear strengthening strategies for I-shaped concrete cross-sections. In the first strategy, CFRP was bonded along the I-shape of the cross-section with the provision of additional anchorage. In the second strategy, the I-shape was transformed into a rectangular shape by using in-fill blocks over which the CFRP was bonded in a U-configuration. In addition to the strengthening strategies, the investigated parameters included two different materials for the in-fill blocks (conventional and aerated concrete) and two different anchoring schemes (bolted steel plate anchor and CFRP spike anchor). To avoid testing on large-scale girders, a new test methodology has been implemented on concrete I-sections. The test results demonstrate the feasibility of comparing different shear strengthening configurations dedicated to I-sections. Among other findings, the results showed that the local transformation of the I-shape to an equivalent rectangular shape could be a viable solution, resulting in shear strength enhancement of 12% to 53% without and with the anchorages, respectively. [ABSTRACT FROM AUTHOR]