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Free chloride concentration distribution is important for assessing the corrosion risk of steel bars in reinforced concrete structures under chloride environment. In this study, a group of 3150 free chloride concentration data sets were obtained. Afterwards, three machine learning methods, namely support vector regression (SVR), multilayer perceptron (MLP) and one-dimensional convolutional neural network (1D-CNN) were adopted to construct models to predict chloride concentration distribution. The results show that 1D-CNN and MLP models are better at predicting the chloride concentration in fly ash concrete, whereas the prediction capability of SVR is relatively poor. Moreover, free chloride concentration prediction based on unmeasured parameters was conducted. The results show that the 1D-CNN and MLP models both have high prediction abilities – that is, predicted results are consistent with experimental measurements, performing generally better than the time-varying model constructed based on Fick's second law. When the free chloride concentrations were higher than 0.1%, the SVR model had a better prediction effect, but had unsatisfactory results and differed significantly from the actual chloride concentration when at a lower concentration. Overall, the 1D-CNN model performs the best in predicting free chloride concentration of concrete at different penetration depths, exposure time and with different fly ash content. [ABSTRACT FROM AUTHOR]

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars. [ABSTRACT FROM AUTHOR]

To enhance the durability of concrete structures in harsh environments, replacing steel bars with FRP bars is judged a feasible method. The low elastic modulus and transverse strength of FRP bars result in the weak shear capacity of concrete beams reinforced with FRP bars. Reviewing and summarizing existing literature are important for addressing this challenge. The research progress on the shear behaviour of concrete beams reinforced with FRP bars was systematically described from two aspects in this paper. In the aspect of literature review, shear mechanisms and main influencing factors of concrete and FRP stirrups were summarized. In addition, achievements and shortcomings of existing literature were summarized, and potential research directions were pointed out. In the aspect of design method evaluation, a database containing 525 samples was established and calculation models of shear capacity of concrete beams reinforced with FRP bars in seven codes were evaluated. Evaluation parameters mainly included shear span ratio, effective height, and maximum strain of FRP stirrups. Based on the calculation model in Italian code CNR DT203-06, an optimized model was proposed to improve the accuracy in predicting concrete shear contribution. The review and evaluation in this paper had important reference significance for improving the design level of concrete structures reinforced with FRP bars and promoting the engineering application of FRP bars. [ABSTRACT FROM AUTHOR]

This study investigates the flexural behaviour of eight full-scale semi-precast slabs, where the precast bottom layer comprises fibre-reinforced concrete (FRC) with varying fibre types such as steel, chopped basalt, and basalt minibar fibres. The upper layer of these semi-precast slabs is cast-in-situ normal-strength concrete, with the interface bonding between the layers enhanced by two steel truss members. The semi-precast FRC slabs are longitudinally reinforced with prestressed basalt fibre-reinforced polymer (BFRP) and steel bars. Within the eight semi-precast slabs, two reference specimens are prepared for comparative analysis. These reference specimens have a precast bottom panel cast with normal-strength concrete, with one reinforced using longitudinal steel bars and the other reinforced with prestressed BFRP bars. The study focuses on assessing cracking patterns, ultimate moment capacity, stress distribution, stiffness, and ductility of these semi-precast slabs. The experimental test results demonstrate that the use of FRC and prestressed BFRP bars has a significant effect on improving the flexural behaviour of the semi-precast slabs, enhancing their strength, curbing deflection, cracking behaviour, and ultimate load capacity. Furthermore, the research includes an evaluation comparing three distinct code specifications for ultimate moment capacity against the experimental outcomes. This comparative analysis reveals a notable discrepancy, emphasizing the need to revise current code equations to better address the complexities associated with combining FRC and prestressed FRP materials in structural applications. [ABSTRACT FROM AUTHOR]

The impact of corrosion degree, axial compression ratio, reinforcement ratio of longitudinal bar and horizontal distribution rebar, and stirrup of boundary column on seismic performance of RC shear walls were investigated. The corrosion forms (rust expansion cracks and corroded steel bars), failure process, hysteretic characteristics, bearing capacity, and deformability were compared. Subsequently, a numerical model of corroded RC shear walls was established adopting shell elements. Finally, according to the numerical simulation method, considering the uncertainty of corrosion degree and material parameters, the vulnerability models of RC shear wall components with different corrosion degrees were built. The results show that the mechanical properties of the shear wall were seriously deteriorated due to the corrosion of steel bars, and the ultimate displacement and ductility coefficient of severely corroded specimens were reduced by 28.5% and 12.27% respectively, compared to non-corroded specimens. A proposed numerical modeling method for corroded RC shear walls based on shell element is accurate, and the bearing capacity error and energy dissipation error of the simulation and test results were less than 20%. As the degree of corrosion grew, the probability of shear wall components experiencing more severe failure added significantly. When the displacement angle was 1/120 (This is the limit value of elastic-plastic displacement angle specified in the code), the probability of DS3 and DS4 occurring in the shear wall with a corrosion degree of 0% were 56% and 39.44%, and the probability of DS4 and DS5 occurring in the shear wall with a corrosion degree of 10% were 41.1% and 38.44%. [ABSTRACT FROM AUTHOR]

The seismic performance of the CRTS II slab ballastless track lateral block (TLB) for high-speed railways (HSRs) is revealed for the first time. Nine test models of the main beam-TLB are constructed with varying quantities and diameters of interface anchorage steel bars. The model scale is 1:2, and the steel scale is 1:4. The study examines the failure mechanism, failure pattern, hysteretic curve, skeleton curve, energy dissipation capacity, ductility, stiffness degradation, and strength degradation of the TLB under low cyclic load. The influence of the diameter and quantity of interface anchorage steel bars on the seismic performance of the TLB is analyzed. The results indicate that the failure pattern of the TLB under low cyclic load can be divided into three stages: (a) the interface of the TLB and main beam initially exhibits minor cracking, which enlarges during loading and closes during unloading; (b) the interface steel bars repeatedly compress the surrounding concrete of the TLB and main beam, and the cracks continue to expand until they penetrate the entire interface, while the interface steel bars undergo shear deformation; (c) the concrete in the interface area between the TLB and main beam is crushed and spalled, and the interface steel bar experiences bending shear deformation, leading to slippage and inclination of the TLB. Increasing the quantity and diameter of interface anchorage steel bars enhances the energy dissipation capacity and ductility of the TLB, reduces the degradation of its strength and stiffness, and improves its seismic capability. However, when the diameter of interface anchorage steel bars reaches 12 mm and the quantity of steel bars reaches 8, the increase rate in energy dissipation capacity and ductility of the TLB slows down while the deterioration rate of strength and stiffness accelerates. [ABSTRACT FROM AUTHOR]

Concrete bridge towers are widely used in long-span bridges. Aiming at the reinforcement process which requires the largest labor force and has the highest safety risk during the construction of the super high concrete bridge tower. The key technology of assembling design and construction of super high concrete bridge tower reinforcement characterized by "industrialized production of mesh, rapid section forming and on-site assembling installation" is creatively proposed. In terms of design, the three-dimensional bridge tower reinforcement is discretized into planar or 3D mesh. In order to facilitate the reinforcement segment, a new flush lapping is used for the circumferential connection of stirrup, and the tapered sleeve splicing is used for the connection of the reinforcement parts between the segments, and the reliability of the connection is verified by experiments. In terms of construction, industrial assembly lines are used for the production of steel mesh and overall bending forming. The bridge tower reinforcement segments are assembled on the special jig, and finally installed on the tower by the tower crane. At present, this technology has been successfully applied to projects such as Lingdingyang Bridge, reducing labor intensity, improving construction efficiency by 30%, and ensuring project quality. [ABSTRACT FROM AUTHOR]

In this paper, some recent analytical expressions including those of codes for shear strength calculation of reinforced concrete (RC) beams without and with stirrups are discussed and verified against experimental data available in the literature. An analytical expression proposed by the author is also introduced and discussed. Two different sets of experimental data were analyzed: one for beams without stirrups composed of 719 data and the other one for beams with stirrups composed of 152 data. Comparison between experimental data and analytical results showed that all of the analytical expressions of international codes are conservative in prediction. The proposed equation gives the same grade of accuracy of the other existing analytical expressions for the prediction of experimental data, and it is derived by a mechanical approach. Comparison shows that although most of the analytical expressions give safe and conservative results, more effort is still necessary to reduce the high scatter of prediction of all the expressions used here, especially for beams without stirrups. [ABSTRACT FROM AUTHOR]

Given the complexities of reinforced soil materials' constitutive relationships, this paper compares reinforced soil composite materials to a sliding structure between steel bars and soil and proposes a reinforced soil constitutive model that takes this sliding into account. A finite element dynamic time history calculation software for composite response analysis was created using the Fortran programming language, and time history analysis was performed on reinforced soil retaining walls and gravity retaining walls. The vibration time histories of reinforced soil retaining walls and gravity retaining walls were computed, and the dynamic reactions of the two types of retaining walls to vibration were compared and studied. The dynamic performance of reinforced earth retaining walls was evaluated. [ABSTRACT FROM AUTHOR]

In this paper, a new type of bamboo scrimber column embedded with steel bars (rebars) was proposed, and the compression performance was improved by pre-embedding rebars during the preparation of the columns. The effects of the slenderness ratio and the reinforcement ratio on the axial compression performance of reinforced bamboo scrimber columns were studied by axial compression tests on 28 specimens. The results showed that the increase in the slenderness ratio had a significant negative effect on the axial compression performance of the columns. When the slenderness ratio increased from 19.63 to 51.96, the failure mode changed from strength failure to buckling failure, and the maximum bearing capacity decreased by 43.03%. The axial compression performance of the reinforced bamboo scrimber columns did not significantly improve at a slenderness ratio of 19.63, but the opposite was true at slenderness ratios of 36.95 and 51.96. When the reinforcement ratio increased from 0% to 4.52%, the bearing capacity of those with a slenderness ratio of 51.96 increased by up to 16.99%, and the stiffness and ductility were also improved. Finally, based on existing specifications, two modification parameters, the overall elastic modulus Ec and the combined strength fcc, were introduced to establish a calculation method for the bearing capacity of the reinforced bamboo scrimber columns. The calculation results were compared with the test results, and the results showed that the proposed calculation models can more accurately predict the bearing capacity. [ABSTRACT FROM AUTHOR]

The synergistic interaction inreinforced concrete systems originates from the strong bond between steel reinforcement and concrete, enabling them to collaborateunder load and optimize structural performance. This study applied various sludge-modified magnesium phosphate cement mixtures to the surfaces of plain round steel bars and ribbed steel bars to prepare steel-reinforced concrete specimens. The characterization of the bond performance of the sludge-modified magnesium phosphate cement reinforcement coating for steel bars and concrete was achieved through analyzing the failure modes, bond strength, and slip values of different groups. Microscopic analysis was performed using a scanning electron microscope. The results revealed that the primary failure mode of the steel-reinforced concrete specimens was steel bar pull-out, with some specimens exhibiting concrete splitting failure. Coating application on plain round steel bars increased bond strength, while on ribbed steel bars, it decreased bond strength. The application of the coating slightly reduced slip values to some extent. [ABSTRACT FROM AUTHOR]

AbstractThis study utilizes nonlinear finite element analysis to simulate the structural response of Reinforced Concrete (RC) corbels with hybrid reinforcements under monotonic loading. The models implemented in ABAQUS examine RC corbels with combined Carbon Fiber Reinforced Polymer (CFRP) and steel reinforcing bars to study the interaction between the concrete and hybrid reinforcement system. Specifically Ultimate load capacity, energy absorption and failure mode. Compressive strength, shear span/depth ratio, and the ratio of CFRP/steel reinforcement were the main parameters that considered in this paper. Results demonstrated a significant improvement in the ultimate load capacity of concrete corbels by up to 53% when both conventional steel and CFRP bars were integrated within the concrete corbel. The numerical test outcomes revealed that an increased hybrid reinforcement ratio effectively managed crack distribution, resulting in reduced concrete crack widths. [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]

Composite slab has extensive application in building industrialization. In this study, a novel composite slab with a joint was proposed, where the precast planks with bent-up rebar are only partially prefabricated along the thickness direction at the joint for cast-in-site pouring of concrete, and the rest is fully prefabricated in the factory. The flexural performance of the composite slab was compared with that of a traditional cast-in-site slab with the same geometric dimensions through four-point bending test. The results demonstrate that the bending performance of the composite slab, including cracking load, yield load, and ultimate load, is basically consistent with that of the cast-in-site slab, and can meet the engineering requirements. Based on experimental results, numerical research was conducted on the composite slabs. The effects of slab thickness, diameter of steel bar, concrete strength of precast plank, and slab span on the flexural behavior of composite slab were investigated. The numerical results show that the cracking load, yield load, and load corresponding to the deflection limit of the specimen increase with the increase in slab thickness and decrease with the increase in slab span. Increasing the steel bar diameter can increase the load corresponding to the deflection limit and yield load, while the effect on the cracking load is almost negligible. The concrete strength of precast plank has no significant effect on the flexural behavior of the composite slab. [ABSTRACT FROM AUTHOR]

To study the flexural behavior of hybrid reinforced concrete (hybrid‐RC) beams with FRP and steel bars, this paper used ABAQUS finite element (FE) software to model and nonlinear analyze the hybrid‐RC beams and investigate the effects of effective reinforcement ratio, concrete strength, and FRP bars type on the flexural behavior of hybrid‐RC beams. In addition, the FRP bars stress, flexural bearing capacity, and ductility formulas for hybrid‐RC beams were fitted based on the FE results, and existing literature data were used to verify their accuracy. The FE model results indicated that the effective reinforcement ratio, FRP bars type, and concrete strength significantly impacted the flexural bearing capacity and deformation performance of hybrid‐RC beams. Increasing the strength of concrete improved the flexural bearing capacity and ductility of hybrid‐RC beams; increasing the effective reinforcement ratio and the elastic modulus of FRP bars increased the flexural bearing capacity of the hybrid‐RC beams but decreased its ductility. In addition, the fitted FRP bars stress, flexural bearing capacity, and ductility calculation formulas can quickly and conveniently predict the flexural bearing capacity and ductility of hybrid‐RC beams. [ABSTRACT FROM AUTHOR]

If recycled concrete is to be widely, reasonably, and safely applied in practical engineering, the study of bond‐slip performance between steel bars and concrete is crucial. In this paper, the central pull‐out test of recycled concrete under different loading rates was conducted. The characteristics of failure mode and crack directions of the specimens were observed and analyzed. The ultimate bond strength and slip displacement between rebar and concrete were analyzed. The effects of three parameters, namely concrete strength grades, replacement percentage of recycled coarse aggregate, and loading rates on the failure modes and bond‐slip mechanical properties of recycled concrete, were analyzed and summarized. The experimental results showed that there were significant differences in the influence trend and amplitude of the above three parameters on the ultimate bonding strength, slip amount, and slip curve. Based on the above experimental and theoretical analysis, a reasonable bond‐slip constitutive model was established in this paper and was in good agreement with the experimental results. [ABSTRACT FROM AUTHOR]

This study aims to investigative the relationship between the pore pressure and the explosive spalling of polypropylene (PP) fiber reinforced concrete when subjected to high temperature. Using the vapor pressure gauge, the moisture measuring sensor, and the thermocouple to measure the vapor pressure, moisture content, temperature, and the temperature on the heated surface of slab specimen, and observing the explosive spalling for the specimens of cylinder and slab made of PP fiber concrete. Test results showed that only the cylindrical specimen without PP fiber and 100% moisture content was apparently subjected to explosive spalling. Comparing with the test results of the slab specimen, the moisture content of the cylinder specimen had a significant effect on the occurring of explosive spalling. On the other hand, the effect of PP fiber on explosive spalling was obviously improved. The control slab specimen without fiber presented explosive spalling on the fire-exposed surface, causing the steel bar to be exposed to air, while the internal temperature rose faster than the PP fiber slab specimen without explosive spalling. The non- PP fiber slab specimen is affected by explosive spalling, the heat trend effect of temperature showed more obvious, and its moisture movement was more rapid than the slab specimen with PP fiber. Under similar moisture content, the slab specimen without PP fiber started sooner to explosive spalling with a serious explosive failure, on the contrary, the slab specimen with 0.1% PP fiber was completely without explosive spalling, indicating the significant effect of anti-explosive spalling by adding PP fiber in concrete. [ABSTRACT FROM AUTHOR]

In past seismic events, earthquakes have often caused significant damage to buildings. It is noteworthy that most of the existing buildings are reinforced concrete structures. Therefore, in order to mitigate the damage caused by earthquakes, it is important to conduct damage assessment of reinforced concrete structures. Considering that damage at the material level is the fundamental cause of component and structural performance degradation, indices based on material damage often have advantages in reflecting and evaluating component and structural damage. This paper proposes a damage constitutive model for concrete based on existing research results. Then, aiming at the shortcomings of current research on steel bar damage constitutive models, a steel bar damage constitutive model under cyclic loading is proposed, reflecting various failure modes of steel bars under seismic actions. Based on this, a multi-level damage index system from materials to components to structures is established. Through multi-level experimental simulations and finite element analysis, the accuracy of the proposed damage indices is validated, and performance indices for components and structures are provided. These indices can effectively reflect the damaged state of components and entire structures and can be used to guide seismic design, damage assessment, and strengthening design. [ABSTRACT FROM AUTHOR]

Under earthquake loads, reinforced concrete chimneys with openings are prone to stress concentration and damage around these openings, possibly leading to structural collapse. In this paper, the stress concentration factor was proposed to quantitatively analyse the range of stress concentrations around openings under various parameters and identify the most significant coefficients affecting the stress concentration range. 9 Groups of numerical analysis models for chimneys with different parameterized openings were established, and more than 200 pushover analyses were conducted. The effects of the chimney wall thickness, wall diameter, opening size, and spacing between openings on the stress around the openings were investigated. Recommendations for limiting opening sizes were given, and a method for designing reinforcement steel bars for strengthening was proposed. The numerical results indicated that the central angle of a single opening cross-section should be less than 70°, and the total central angle of multiple openings should be less than 140°; the spacing between openings should not be less than 0.5 times the width of the opening; the range of the steel reinforcement range should be 4.5 times the wall thickness for circular openings; and for rectangular openings, it should be 3.5 times the wall thickness. The added reinforcement steel should have a reinforcement ratio for strengthening of 1.3 times that of the original reinforcement ratio. Finally, through dynamic analysis, it was verified that the opening reinforcement design method proposed in this paper can effectively reduce the stress concentration around openings. [ABSTRACT FROM AUTHOR]

In this paper, the flexural stiffness of the reinforced concrete (RC) beams reinforced with high‐strength steel bars after exposure to different elevated temperatures was investigated experimentally and theoretically. The effects of the elevated temperature (room temperature, 200°C, 400°C, 600°C, 800°C, and 1000°C), high‐temperature duration time (0 h, 1 h, and 2 h), and steel bar types (HRB600 and HRB500) on the load–deflection response, load–stiffness response, and crack distribution of tested beams were investigated. The results showed that when the temperature is below 600°C, the effect of high temperature on the stiffness reduction of high‐strength RC beams is not significant, while the beams reduced the stiffness when the exposure temperature reached 800°C and 1000°C, regardless of the type of the steel bars. The elevated temperature accelerated the development of the deflection of RC beams, and the bending stiffness of the RC beams decreased more severely as the increase of duration time. By using appropriate degradation factors, the residual stiffness of the beams was predicted well by the analysis calculation method and the effective inertia moment calculation method, for example, the prediction accuracy is over 91% and 85.8% for the cases under and over 800°C, respectively. However, for the beams at 1000°C, a correction coefficient (0.652) was applied to improve the accuracy of the calculative stiffness of the HRB600 RC beams at the service load stage. [ABSTRACT FROM AUTHOR]

This paper presented the experimental results of the strength capacity of studs embedded centrally in concrete with red mud synthetic coarse aggregates, with the variation of the handcrafted headed stud thickness (3.17, 4.76, 6.35, and 7.9 mm) and no shank bond influence with concrete. The results regarding the compressive strength of concrete showed considerable strength gain with synthetic coarse aggregate, ranging from 27.00 to 43.50 MPa, while in concrete with natural coarse aggregate, the variation was 27.00 to 36.50 MPa. Also, it was observed that the cracking in the concrete matrix of the synthetic coarse aggregate occurred in the aggregate instead of the transition zone, as occurred with the natural coarse aggregate concrete. However, the solid morphological formation of synthetic coarse aggregate provided excellent chemical adhesion to the headed stud, providing a hardening failure behavior after reaching the yield strength value of the steel bar with higher displacements. This can enable the optimized consumption of materials in the dosage of low‐strength structural concrete and the anchoring application of studs with smaller‐headed thicknesses, up to 8% of head diameter, generating economy and sustainability. [ABSTRACT FROM AUTHOR]

To investigate the flexural behavior of hybrid reinforced concrete (Hybrid‐RC) beams with Basalt fiber‐reinforced polymer (BFRP) bars and steel bars, this paper designed 14 Hybrid‐RC beams and studied the effect of different reinforcement forms on the flexural behavior of Hybrid‐RC beams. The research results indicated that when ρ≈2.28%$$ \rho \approx 2.28\% $$, an increase in Af/As$$ {A}_{\mathrm{f}}/{A}_{\mathrm{s}} $$ leads to a decrease in the cracking moment, ultimate moment, and ductility of Hybrid‐RC beams, the maximum crack width and deflection will increase. When ρ≈0.86%$$ \rho \approx 0.86\% $$, an increase in Af/As$$ {A}_{\mathrm{f}}/{A}_{\mathrm{s}} $$ will lead to a decrease in the cracking moment, deflection, and ductility of the Hybrid‐RC beams, while the maximum crack width and ultimate moment will increase. In addition, when ρ≤1.87%$$ \rho \le 1.87\% $$, the area of BFRP bars (the area of steel bars remains unchanged) should be changed to improve the flexural behavior of the Hybrid‐RC beams; When ρ>1.87%$$ \rho >1.87\% $$, the Hybrid‐RC beams should change the area of steel bars (the area of BFRP bars remains unchanged) to improve the flexural behavior of the beams. In addition, the ductility index prediction equation for Hybrid (BFRP and steel)‐RC beams was fitted based on the results of the theoretical model research. [ABSTRACT FROM AUTHOR]

A new type of buckling-restrained brace (BRB), called induction-hardened buckling-restrained brace (IHBRB), is proposed in this study. The IHBRB uses a round bar as the core steel and a hollow round section as the restrainer. The core steel undergoes partial induction hardening, which makes its strength lower in the middle but higher at the two ends. This strength difference along the length is expected to trigger energy dissipation in the middle but keep the ends undamaged. The restrainer has an inner diameter similar to that of the core steel, which minimizes the gap between them and avoids time-wasting grouting. This study introduces experimental and analytical research on four types of IHBRB. Tensile coupon tests revealed that the core steel of the IHBRB-600 series satisfied the target yield strength of 600 MPa in the middle and 1,200 MPa at both ends. The core steel of the IHBRB-800 series also satisfied the target yield strength of 800 MPa in the middle and 1,200 MPa at both ends. The ascending cyclic loading test showed that the IHBRB exerted a load capacity of over 1,000 kN as designed and exhibited tensile-compressive symmetric hysteresis behavior. IHBRB-600L, the specimen that failed by tensile fracture, showed that the high-strength brace end succeeded in remaining elastic as planned, while the low-strength brace middle showed a higher-order mode buckling. However, unexpected overall buckling at the joint occurred on other specimens. The low cycle fatigue specimens showed large cumulative inelastic deformation ratios of more than 200. A three-dimensional finite-element model of IHBRB-800L built by ABAQUS/Explicit (Dassault Systèmes Simulia Corp., Paris) captured the experimental results well. A parametric study revealed that the longer restrainer fixed at one side of the core steel end was one of the solutions to guarantee the great seismic performance of the IHBRB. [ABSTRACT FROM AUTHOR]

The effects of chlorides on the corrosion of steel bars within a matrix comprising modified magnesium oxysulfide (MMOS) cementitious materials was investigated. The phase composition, morphology and distribution of steel corrosion products (SCPs) were studied. There was basically no corrosion of the steel bars in the MMOS cement without chlorides. A high chloride content and a high water/cement (w/c) ratio in the MMOS matrix had adverse effects on the steel bar corrosion. The primary SCPs in the MMOS mixes were iron oxyhydroxides (FeOOH) and ferric oxide (Fe2O3), while ferrous oxide (FeO) was only observed at low w/c ratios, indicating a lower degree of oxidation. The presence of di-iron nonacarbonyl (Fe2(CO)9) at high w/c ratios suggested a higher degree of oxidation. At lower w/c ratios, rust products readily diffused. Conversely, at higher w/c ratios, these products accumulated close to the steel bars, resulting in a compact structure. [ABSTRACT FROM AUTHOR]

Corrosion of steel bars embedded in reinforced concrete structures considerably reduces the service life and even causes early failure of the structure. This paper investigates the early corrosion behavior of an alloy corrosion-resistant steel bar in seawater–sea sand concrete (SWSSC) using various electrochemical measurements [electrochemical impedance spectroscopy (EIS) linear polarization resistance (LPR)] and surface characterization techniques [scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), atomic force microscope (AFM), and X-ray photoelectron spectroscopy (XPS)], in comparison to low carbon steel bar (LC) and stainless steel bar (SS). The results reveal that the Cr10Mo1 alloy corrosion-resistant steel bar (CR) in SWSSC shows significant increase in the radius of the capacitive arc in later stages, particularly in the low frequency region. This increase in CR can be attributed to the enhanced corrosion resistance of the passivation film, as well as the rise of impedance at the interface between the passivation film and the concrete matrix. These improvements have effectively inhibited the penetration of free chloride ions into the concrete, thereby impeding the initiation and propagation of corrosion in CR In addition, the mechanical properties, pore structure and the hydration production of SWSSC were investigated. Based on the interactions between steel substrate and concrete matrix, the possible resistance mechanism of CR was proposed. This study innovatively provides a comprehensive evaluation of the effectiveness of CR in SWSSC. [ABSTRACT FROM AUTHOR]

Corrosion protection of steel bars in alkaline concrete environments poses a common challenge in marine engineering. One approach to mitigate steel bar corrosion is the addition of corrosion inhibitors to the concrete. In alkaline environments, the passivation of rebars occurs through anodic passivation coupled with the cathodic oxygen reduction reaction (ORR). The catalysis of ORR can expedite anode passivation. To investigate the corrosion inhibition of steel bars in alkaline environments, meso‐tetra(4‐carboxyphenyl)porphine (TCPP), known for its ORR catalytic properties, is selected. TCPP forms adsorption films on the surface of steel bars, facilitating the formation of passivation films. TCPP primarily adsorbs onto active sites on the surface of the passivation film, where lattice iron ions have leached. The adsorbed TCPP accelerates the formation of the passivation film through ORR catalysis, inhibiting the development of passivation film defects and enhancing the integrity and protection of the passivation film. The most significant effect is observed when the concentration of TCPP is 0.5 mmol/L. The physical adsorption of TCPP is primarily determined by the negative charge centers, namely the carboxyl group O and the pyrrole N. However, due to steric hindrance caused by the unrestricted rotation of the carboxyl benzene, the pyrrole N does not play a dominant role in chemical adsorption. Instead, the active site for chemical adsorption is the carboxyl group O. The adsorption process significantly reduces the diffusion coefficient of TCPP molecules, providing a robust and stable adsorption binding. Phthalocyanine molecules without carboxyl benzene groups adopt a planar structure, allowing them to form stable adsorption configurations on the iron surface through flat adsorption. This observation provides guidance for the design of novel metal phthalocyanine molecules. Specifically, the development of metal phthalocyanine molecules with modifying groups that are coplanar with the phthalocyanine ring and possess restricted rotation can achieve flat adsorption, improve coverage rate, and enhance adsorption configuration stability. [ABSTRACT FROM AUTHOR]

Carbon-fiber-reinforced polymer (CFRP) is a composite material consisting of a resin matrix reinforced with carbon fibers. This study focuses on CFRP composite pipe piles as the subject of investigation, exploring the impact of substituting steel bars with CFRP bars on the bending performance of pipe piles through rigorous three-point bending tests. The attenuation of flexural stiffness in CFRP pipe piles under a chloride salt environment was anticipated. The lateral bearing capacity of CFRP pipe piles was calculated by introducing a stiffness degradation coefficient for the piles and utilizing the finite difference method. The findings of the analysis suggest that as the CFRP reinforcement replacement rate increases, the initial bending stiffness of the composite pipe pile experiences a corresponding decrease. After serving for 28.15 years, the steel reinforcement within the pipe pile commences rusting, resulting in a nonlinear decline in the bending stiffness of the composite pipe pile. As the service time of pipe piles increases, a higher replacement rate of CFRP reinforcement results in a slower attenuation of pile stiffness. Consequently, both the horizontal displacement at the top of the pile and the bending moment along the body of the composite pipe pile gradually increase over time. During the same service period, the higher the rate of CFRP reinforcement, the less noticeable the attenuation in the horizontal bearing capacity of the pile shaft. [ABSTRACT FROM AUTHOR]

The use of plastic in modern society has resulted in a considerable amount of environmental contamination, largely due to the inherent chemical composition of the material. This poses a significant risk to the surrounding environment, particularly in terms of its impact on soil, air, and water quality. The use of recycled plastic in concrete is becoming increasingly prevalent within the construction industry due to its potential to mitigate environmental contamination from plastic waste. The objective of this study was to evaluate the performance of concrete incorporating recycled Polypropylene (PP) plastic as a fine aggregate. The two critical factors under examination were the quantity of PP plastic granules used as a proportion of fine aggregate (ranging from 0% to 30%) and the water-cement (w/c) ratio, which could be 0.45 or 0.55, in conjunction with a 1.5% plasticizer. The samples were subjected to a pull-out test to evaluate the parameters of bond stress behavior, failure mode, and bond-slip behavior. The findings indicated that an increase in the proportion of PP plastic granules used as a substitute for fine aggregate resulted in a notable reduction in bond strength, which was further amplified when the w/c ratio was diminished. The incorporation of 10% PP plastic granules led to a reduction in bond stress by 13.4% and 11.56%, respectively, in samples with w/c ratios of 0.45 and 0.55. Consequently, at a low w/c ratio, the predominant failure mode is considered to be splitting, while a higher w/c ratio increases the probability of pull-out splitting failure. [ABSTRACT FROM AUTHOR]

Bubbled Reinforced Concrete (RC) slabs have gained popularity in recent years as a practical construction method that eliminates unnecessary concrete in the center, thereby reducing the dead weight of the structure. This study provides a systematic framework to compare the performance and capabilities of one-way bubbled concrete slabs reinforced with Glass Fiber Reinforced Polymer (GFRP) bars and embedded steel I-sections. Four one-way concrete slabs, each with a length of 2,600 mm and a rectangular cross-sectional area of 600 mm in width and 150 mm in depth were employed. These slabs were reinforced with Glass Reinforced Plastics (GRP) rebar at the same reinforcement ratio and tested by two-point bending to failure. Different parameters such as specimen type (solid or bubbled slabs) and internal reinforcement were achieved using steel I-sections in two different shapes (2 and 4 pcs of steel I-sections), where 4I-section shape with a cross-sectional area equivalent to 2I-section shape, channel shear connectors, and bent steel bars (10 mm diameter) were used to improve the shear resistance. The results showed that bubbled slabs experienced a higher range of deformations (including deflection, strains, and cracks) by about (28%-88%) and a 15% decrease in ultimate load capacity compared to solid slabs. On the other hand, the use of steel I-sections as internal reinforcement significantly improved the specimen performance compared to unreinforced slabs (Steel Slab (SS) and Bubbled Slab (BS), respectively). Deflection was reduced by approximately 52% and 87% at the same load level, ultimate load capacity increased by approximately 121% and 179%, and flexural stiffness increased by approximately 197% and 272% at the same load level. [ABSTRACT FROM AUTHOR]

The slab is more petite and space-efficient in flat plate buildings since it is supported directly by columns rather than beams or drop panels, allowing additional floors to be added. Despite these benefits, a flat plate slab is vulnerable to brittle punching shear, a catastrophic collapse caused by the abrupt propulsion of a slab piece out from underneath by a column. In this study, Finite Element Analysis (FEA) was provided and carried out in ABAQUS/CAE 2019 to model the effects of punching shear impact on a flat plate reinforced with horizontal steel bars that vary in position, diameter, and number. Concrete was represented in the model by 8-noded hexahedral 3D brick elements and steel reinforcements by 2-noded linear 2D beam elements. The model has been modified according to the results of the experiments. In order to determine how different quantities and sizes of horizontal steel bars placed at different locations in a flat plate affected the slab's performance, parametric analysis was conducted. According to the outcomes, the shear capacity increases between 0.37 and 9.85% as the diameter of bars increases, between 1.2 and 22.9% as the quantity of bars increases, and between 1.99 and 26.1% as the bars shift from the tension side to the compression side. [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]

Copyright of Acta Materiae Compositae Sinica is the property of Acta Materiea Compositae Sinica Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

C45, a ferromagnetic material, can be strengthened by heat treatment such as quenching and is widely used as a material for general mechanical parts such as springs in automobiles. However, the presence of defects or flaws can cause cracking during the quenching stage, and a high-speed inspection method for detecting defects is required. In this study, we proposed and examined an inspection method for detecting defects using only a DC magnetic field by moving a round steel bar material at a high speed of 1 m/s inside a ring-shaped permanent magnet and generating eddy currents due to the velocity effect. [ABSTRACT FROM AUTHOR]

In recent years, high-ductility concrete (HDC) has gradually become popular in the construction industry because of its excellent ductility and crack resistance. Concrete itself is a kind of building material with poor tensile properties, and it is necessary to add a large number of steel bars to improve its tensile properties, which increases the construction cost of buildings. However, most of the research studies on high-ductility concrete are scattered. In this paper, the basic mechanical properties of high-ductility concrete and the effects of dry and wet cycles, freeze–thaw cycles, and salt erosion on the durability of high-ductility concrete are obtained by comprehensive analysis. The results show that the tensile properties of HDC can be significantly improved by adding appropriate fiber. When the volume fraction of steel fiber is 2.0%, the splitting tensile strength of concrete is increased by 98.3%. The crack width threshold of concrete chloride erosion is 55–80 μm, and when the crack width threshold is exceeded, the diffusion of CL-1 will be accelerated, and the HDC can control the crack within the threshold, thereby improving the durability of the concrete. Finally, the current research status of high-ductility concrete is analyzed, and the future development of high-ductility concrete is proposed. [ABSTRACT FROM AUTHOR]

With the development of global hydropower, the scale of hydropower stations is increasing, and the operating conditions are becoming more complex, so the stable operation of hydropower stations is very important. The vibration of the turbine unit will cause resonance in the powerhouse, and the structural stability of the powerhouse will be affected. Many scholars pay attention to the stability of the turbine unit operation, and there are few studies on the powerhouse of the hydropower station. Therefore, this paper relies on the Weifang Hydropower Station project to study key issues such as the tensile strength of concrete and how to arrange steel bars to increase the structural stability by changing the material properties through FEA. Three schemes are designed to evaluate the safety of the powerhouse structure when the turbine unit is running through the safety factor. Our findings indicate that the stress variation patterns observed on the inner surface of the powerhouse remain consistent across different operating scenarios. Notably, along the spiral line of the worm section, we observed that the stress levels on the vertical loop line decrease gradually with increasing distance from the inlet. Conversely, stress concentrations arise near the inlet and the tongue. Additionally, it has been noted that the likelihood of concrete cracking increases significantly at the tongue region. [ABSTRACT FROM AUTHOR]

The performance of joint connections in composite slabs is crucial for ensuring their bidirectional load-bearing capacity and overall structural integrity. To effectively address the challenge of protruding rebar in precast components, a new structural form of a tightly connected hollow concrete composite slab without protruding rebar on the slab side is proposed. To investigate the mechanical performance and failure modes of this slab-side tight-joint connected hollow concrete composite slab, bending performance tests under monotonic load were conducted on three tightly connected hollow composite slabs and one seamless hollow composite slab. The analysis focused on the failure modes, crack distribution, bending capacity, and bending stiffness of additional steel bars at the joints of the slabs. The results indicate that, under normal operating conditions, the flexural performance development of concrete hollow composite slabs with tightly connected slab sides is generally consistent with that of the non-spliced cast hollow composite slab. Under ultimate conditions, tearing or brittle fracture failure at the joint interface is likely to occur in the composite slabs, leading to a reduction in flexural bearing capacity. With an increase in joints, the bending capacity of the hollow composite slab decreases by 17.1%, Conversely, when joints are positioned away from the most stressed section, the flexural stiffness of the section increases by 13.5%. A comparison of experimental data and theoretical calculations indicates that the additional rebar at the joints effectively contributes to the lateral load transfer in the hollow composite slab, achieving bidirectional load-bearing capacity. This further validates that the design of the single-joint, tight-joint connected hollow concrete composite slab without protruding rebar meets the requirements for bidirectional load-bearing performance. [ABSTRACT FROM AUTHOR]

Concrete-filled steel tubes (CFSTs) have been increasingly utilized in engineering due to their excellent mechanical properties. Ensuring a solid bond between a steel tube and concrete is essential for optimizing their synergistic effect. This study introduces an internally welded steel bar structure within the inner wall of a steel tube to enhance the bond properties at the connection interface. The influence of various configurations of steel bars welded to the inner surface of the tube on the bond strength is investigated considering the impact of vibration on the load-bearing capacity of the component. This study comprises two groups of specimens, one with vibration and one without vibration, for a total of ten specimens. Each group included CFST members with five distinct internal welded steel bar structures. The experimental results, including load–displacement curves and strain data of the steel tube, were used to assess the impact of the internal welded steel bar configurations on the steel–concrete interface. The sliding process is described by correlating test data with curves and observed phenomena. To comprehensively compare the effects of structural dimensions on the bonding and slipping properties of the welded bars, finite element simulations replicating the experimental conditions were carried out using ABAQUS software, and the simulation results agreed with the experimental observations. The study demonstrated that incorporating internal welded steel bars substantially enhances the bond strength of steel pipe–concrete interfaces. While vibration weakens the bond strength in CFST members, internal welded steel bars mitigate this effect. These findings improve the structural performance of CFST structures and their resilience to external vibrations. [ABSTRACT FROM AUTHOR]

Flexural hybrid reinforced concrete members with fiber reinforced polymer (FRP) and steel bars (hybrid-RC) exhibit significant post-yielding stiffness due to the contribution of tensile FRP bars. To predict the post-yielding deflection of hybrid-RC members, the Bischoff's model for effective moment of inertia is extended into the post-yielding stage. Based on this extended model, expressions for equivalent moment of inertia, which consider the variation in stiffness along the member span with and without tension stiffening, are proposed. Obtaining close-formed solutions for the yielding moment of hybrid-RC cross sections, a critical parameter for determining the post-yielding effective moment of inertia, proves challenging due to the unknown state of compressive concrete. Therefore, a simplified equation to determine the yielding moment are proposed by regression of data derived from numerical sectional analyses. An experimental database including 92 hybrid-RC beams collected from published literature is established. The performance of the proposed equation for the yielding moment and expressions for the equivalent moment of inertia are evaluated using the database. The results indicate that the proposed equation can effectively predict the yielding moments of hybrid-RC beams. Furthermore, using a constant effective moment for predicting the post-yielding deflection is effective for the specimens with relatively high reinforcement ratios. The benefit of considering the stiffness variation along the member span is evident when dealing with lightly-reinforced concrete members. [ABSTRACT FROM AUTHOR]

To obtain a precise finite-element model (FEM) for analyzing the dynamic response of corroded beams at high temperatures, a stepwise FEM modification strategy is proposed based on the improved extreme learning machine. Three concrete beams were designed and cast, and the dynamic response characteristics of corroded concrete beams at room temperature and high temperature are discussed. Firstly, electrical accelerated corrosion tests and vibration tests were conducted on simply supported beams at room temperature. The fundamental frequencies of concrete beams under different corrosion ratios were measured. The attenuation law of fundamental frequency with corrosion ratio also was studied. Subsequently, the FEM under different corrosion ratios was modified. The bond-slip between steel bars and concrete under different degrees of corrosion was considered during the correction process. Finally, a vibration test at high temperature was performed. The modal attenuation law of corroded beams at high temperatures was analyzed. Based on the modified FEM, numerical analysis at high temperature was performed. The proposed FEM modification strategy and the study of the attenuation regularities of modal information under fire exposure provide a foundation for further research on the damage development of corroded reinforced concrete (RC) beams under fire exposure. [ABSTRACT FROM AUTHOR]

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

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

In order to investigate the mechanical properties of polyurethane cement (PUC) composite materials, axial tensile test, acid and alkali corrosion resistance test, bond test with concrete, and bond test with steel bars were conducted. The axial tensile results show that the tensile strength of PUC material is 31.11MPa, the stress-strain curve for axial tensile behavior of the material is obtained through fitting. To explore the durability of PUC materials, acid-alkali-salt corrosion resistance test is carried out, the results show that the PUC material has good resistance to acid and alkali corrosion. The failure mode of the bond test between PUC material and concrete is internal cohesion failure of concrete material, indicating good bond performance of PUC material. Axial tensile test of PUC material is carried out at different temperatures (-40°C~60°C). When subjected to temperatures between 40°C and 60°C, the strength of materials does not deteriorate. However, it is noteworthy that the material's ability to withstand tensile strain significantly increases as temperatures rise to 60°C. The bonding strength between PUC material and steel bar increases with an increase in protective layer thickness, and at a thickness of 70 mm, the maximum bond stress is achieved at 16.38 MPa. On the other hand, the strength of the bond reduces as the anchorage length increases. Smooth round bars demonstrate a significantly lower bond strength compared to deformed bars, as their maximum bond strength is at approximately 47.4% of that of the deformed bars under the same conditions. [ABSTRACT FROM AUTHOR]

Based on the insufficient data on bonding performance and effective anchorage length of sleeve grouting in assembled structure. Combining the existing studies, the sleeve grouting joint test for the static unidirectional tensile test was designed, and the influencing factors are reinforcement diameter and reinforcement anchorage length. Then, the failure mode, load-displacement relationship, energy consumption capacity and bearing capacity of the grouting sleeve connection are analysed, and the stress mechanism of the specimen in the one-way tensile state is expounded. This paper considers the actual damage state of the joint, according to the failure of the reinforcement outside the joint and the sleeve; referring to the reinforcement-concrete bond strength research theory, the effective anchorage length formula is proposed. When the steel bar is pulled out, the bond strength and bearing capacity mainly depend on the effective anchorage length. However, when the specimen breaks the steel bar outside the joint, it depends on the material performance of the steel bar itself. The research results of this paper can lay a theoretical foundation for the application of sleeve grouting joints. [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]

In order to explore the durability of manufactured-sand-reinforced concrete and its wet joint in a plateau environment, an integrally formed (IF) specimen and a wet joint specimen with punched interface (PI) made up of manufactured sand concrete were prepared in the simulated plateau environment. On the one hand, the accelerated corrosion test on IF and PI specimens was conducted to investigate their durability under corrosion. On the other hand, the freeze–thaw cycle test was carried out on IF and PI specimens to evaluate their frost resistance. Subsequently, the accelerated corrosion test was continuously performed on IF and PI specimens subjected to freeze–thaw cycles. The development of surface cracks, the corrosion morphology of internal steel bars, the actual corrosion rate, the section loss of corroded steel bars and the degradation of mechanical properties of steel bars after corrosion were analyzed. Moreover, the microstructural changes of specimens after different freeze–thaw cycles and corrosion degrees were observed. The results show that during single corrosion, the development of crack width of concrete, the increase in actual corrosion rates of steel bars and the degradation of mechanical properties of steel bars for IF and PI specimens before the theoretical corrosion rate of 6% were relatively slow, and once the theoretical corrosion rate exceeded 6%, these began to accelerate. The development of concrete cracks and the distribution of crack width are affected by wet joints. Compared with IF specimens, the average and maximum longitudinal crack widths of PI specimens increase by 0–22.54% and 12.16–21.95% for different freeze–thaw cycles, respectively. The frost resistance of the PI specimen decreases due to the existence of a wet joint. After freeze–thaw cycles numbering 50, the difference in frost resistance between IF and PI specimens obviously increased. Compared with IF specimens, the nominal yield strength, nominal ultimate strength and elongation of PI specimens after freeze–thaw cycles numbering 25~100 and corrosion with the theoretical corrosion rate of 6% decreased by 5.56–9.11%, 4.74–6.73% and 23.08–28.72%, respectively. The combined effect of freeze–thaw cycle and corrosion has a great influence on the ductility of steel bars. [ABSTRACT FROM AUTHOR]

In this paper, uniaxial tensile testing of semi-grouted sleeve connectors was carried out by controlling the amount of expansive agent in the grout material. The effects of different steel bar diameters and anchorage depths on the failure mode, bearing capacity, and surface strain of sleeve connectors were studied. It is found that there are three failure modes in the specimens--namely, steel bar pullout failure, steel bar slip failure, and screw thread failure. The expansion characteristics of the grout material can partially compensate for the lack of compressive strength. Based on the analysis of the ultimate bearing capacity of different specimens, a design method to prevent the slip failure of the semi-grouted sleeve is proposed. The addition of 5 to 11% expansive admixture can reduce the circumferential strain of the casing from the steel bar anchorage location to the grouting end by 28.57 to 125.30%, with no impact on the longitudinal strain variation pattern. As the depth of steel bar anchorage increases, the expansive effect of the steel bar anchorage and casing longitudinal strain gradually surpasses the shrinkage effect, while the shrinkage effect at the grouting end of the casing gradually outweighs the expansive effect. With an increase in steel bar diameter, the longitudinal strain at the grouting end of the casing only decreases by 1.75% and 2.10%, essentially having no significant impact. [ABSTRACT FROM AUTHOR]

Strictly following the similarity principle of specimen size, eccentricity, and carbon fiber-reinforced polymer (CFRP) strengthening layers, three groups of reinforced concrete square columns with different scales were designed. Experimental studies on eccentric compression of unstrengthened columns and CFRP-strengthened columns were carried out. The failure characteristics of specimens of various sizes were obtained, as well as the bearing capacity, ductility coefficient, lateral deflection, CFRP, and steel bar strain were analyzed. The test results showed an improved ductility, stiffness, and bearing capacity of eccentrically compressed reinforced concrete columns, strengthened with CFRP. However, the strengthening effect is inversely proportional to the size of the specimen and has a more obvious size effect. [ABSTRACT FROM AUTHOR]

This paper presents the details of the analyses which were conducted to study the effects of steel reinforcing bars with unintended high strength on the behaviors of reinforced concrete (RC) columns. The influence of these bars on the column strength and strength-reduction factors were investigated. The former was studied with the help of column axial load-moment interaction diagrams, while a reliability analysis was carried out for the latter. Four different column cross sections reinforced with reinforcement ratios varying from 1 to 4% were included in the analysis. Other variables included concrete compressive and reinforcing bar yield strengths. The effects of the aforementioned variables were also considered on the development length of the reinforcing bars in tension and compression. It was found that the use of reinforcing bars with unintended high strength could change column behavior to compression-controlled at a lesser axial load level, which is accompanied by a reduction in the curvature capacity. Modifications have been suggested to control the negative effects of unintended high strength of bars on the column behavior and bar development length. Strength-reduction factors for RC sections ranging from compression-controlled to tension-controlled regions have also been proposed, which differ from those suggested by the prevalent code of practice. [ABSTRACT FROM AUTHOR]