Ribbed Steel Bars Research Articles

Bond Degradation Mechanism and Constitutive Relationship of Ribbed Steel Bars Embedded in Engineered Cementitious Composites under Cyclic Loading

In order to investigate the bond degradation mechanism and constitutive relationship of ribbed steel bars in engineered cementitious composites (ECCs) under cyclic loading, 12 groups of specimens were tested in this paper. The design parameters included ECC compressive strength, ECC flexural toughness, cover thickness, and anchorage length. The results indicated that the degradation of the bond behavior of the ribbed steel bars in the ECCs under cyclic loading was mainly caused by the degradation of the properties of the ECC material itself, concentrating on the development of cracks in the ECC, the extrusion and shear failure of the ECC between the steel bar ribs, and the continuous grinding of the ECC particles on the shear failure surface. The degradation of the bond stress-slip curves under cyclic loading was mainly reflected by the degradation in the ultimate bond strength and unloading stiffness. According to the monotonic loading test results, a monotonic bond stress-slip relationship model was proposed. On this basis, through building the hysteretic rules of the bond stress-slip curves under cyclic loading, a calculation model was proposed to predict the bond stress-slip constitutive relationship between the ribbed steel bars embedded in the ECCs under cyclic loading. Finally, the validity of the proposed model was verified by a comparison between the model curves and the tested curves.

Bonding of Carbon Steel Bars in Concrete Produced with Recycled Aggregates: A Systematic Review of the Literature

Civil construction is essential for the world economy and the largest generator of construction and demolition waste (CDW), mainly due to a lack of planning, technological control, and restoration execution, among other factors. While efforts are made to minimize this waste generation, one possible application for CDW is its incorporation into Portland cement-based materials as recycled aggregates, in partial or total replacement of natural aggregates. However, for CDW use to be feasible, the structure performance and safety must be assured, and the adherence between concrete and reinforcement bars, in this context, is a fundamental mechanism. With this perspective, this paper aims to investigate the influence of recycled aggregate on steel–concrete bonding. To this end, the SREE (Systematic Review for Engineering and Experiments) method was employed as a novelty, including a methodology quality analysis, to search and analyze relevant scientific articles published in the last ten years. The results revealed that the use of CDW as recycled aggregates in concrete worsens the steel–concrete bonding, and that ribbed steel bar seems to be the best option when employed in RC structures built with CDW-concrete, although the bar diameter and the anchorage length still need further investigations, and that CDW-concrete’s use can significantly contribute to reducing the emission of greenhouse gases and to capturing CO2 from the atmosphere. Therefore, further investigations should focus on the real influence of recycled aggregate type and replacement content, bar diameter, anchorage length, and CDW’s potential to capture CO2.

Bond behavior between steel bars and 3D printed concrete: Effect of concrete rheological property, steel bar diameter and paste coating

• The effects of the rheological property on the steel–concrete bond behavior of printed and cast samples were investigated. • The porosity at the steel–concrete interface is related to the bond strength. • The bond strength values of 3D printed samples with ribbed bars of different diameters were compared. • The rheological properties of fresh concrete for 3D printing are very significant to control the quality of reinforced 3D printed concrete. Due to the unique layer by layer deposition process of extrusion-based 3D printed concrete (3DPC), the bonding of steel bars with 3DPC differs from that with traditional cast concrete. To understand the steel-printed concrete bond behavior, this paper mainly explored the effect of preparation technologies, concrete rheological properties, steel bar diameter and paste coating on steel bars on the bond behavior between ribbed steel bars and concrete. According to pull-out test and X-ray computed tomography test, the results showed that bond strengths between 3DPC and steel bars were obviously lower than those between steel bars and cast concrete. The rheological properties of fresh concrete show significant impact on the bond behavior of reinforced 3D printed samples. Lower yield stress and plastic viscosity can narrow the bond strength gap between printed samples and cast samples. The utilization of surface coated steel bar with fresh cement paste can effectively enhance the steel-3DPC bond strength. The variations in steel–concrete bond strengths can be explained via pore structure at steel–concrete interface. The results suggest that it is of great importance to control the quality of reinforced 3D printed concrete by optimizing the rheological properties of fresh concrete for 3D printing.

Analytical solution of the bond strength between ribbed steel bar and engineered cementitious composites considering the fiber bridging effect

AbstractThis paper investigated the analytical solution of the bond strength between ribbed steel bar and engineered cementitious composites (ECC). In this method, ECC cover was regarded as a thick‐walled cylinder subjected to the uniform internal pressure which consisted of an elastic uncracked outer ring and a partially cracked inner ring. For the uncracked outer ring, it can be solved by the elastic mechanics theory. To solve the partially cracked inner ring, two key problems that had to be investigated were the crack width and the tensile stress–crack width relationship of ECC. According to the steady‐state cracking mode, the hoop deformation of ECC was expressed by the equal distribution and then the crack width can be determined. Besides, the fictitious crack model in fracture mechanic was introduced to describe the crack propagation process. Then a trilinear model was applied to reflect the tensile stress–crack width relationship of ECC materials, which considered the combined action of aggregate bridging and fiber bridging on the crack surface. Finally, the comparison between the calculation results and experimental results was carried out to prove the validity of the analytic method of bond strength proposed in this paper. Results indicated that the analytical solution and the experimental data fitted in well with each other. Then parameter analyses were conducted based on the analytical method proposed in this paper.

Rust Distribution of Non-Uniform Steel Corrosion Induced by Impressed Current Method.

The non-uniform corrosion of steel bars is the main factor affecting the durability of concrete. The cracking pattern of concrete due to corrosion is closely related to the distribution of the corrosion products. Research on the thickness distribution of the rust layer and the cracking pattern of concrete under different influencing factors is of great significance in the prediction of the service life of existing reinforced concrete structures and the avoidance of the premature cracking of the reinforced concrete structures to be built. This paper studies the thickness distribution of the rust layer on the surface of single and multiple corroded reinforcements under non-uniform corrosion. The electrochemical analysis of the electrified corrosion process was carried out by using the finite element analysis software, and the distribution of the current density was obtained. The effects of geometric parameters, steel bar position, and steel bar spacing and shape on the corrosion expansion cracking pattern were studied. The results indicated that as the position of the steel bar differed, the crack pattern of the concrete changed, depending on the number of corrosion peaks (i.e., the maximum thickness of the rust layer). In terms of the corner-located steel, the number of corrosion peaks varied in the cases of different geometrical parameters (i.e., the diameter of the steel bar and the distance between the steel bars and the stainless steel wire). Nevertheless, the critical corrosion degrees of the side-located and corner-located steel bars, with respect to the cracking of the outer concrete surface, were basically the same. Additionally, the ribbed steel bar presented a lower critical corrosion degree than that of the plain steel bar, while little influence was exhibited with the varying angles of the rib.

Tetrahedral Profiled Carbon Rovings for Concrete Reinforcements

Textile reinforcements have established themselves as a convincing alternative to conventional steel reinforcements in the building industry. Due to their high load-bearing capacities in addition to a smaller concrete cross section required, the bond between textile and concrete is extremely important. In contrast to ribbed steel bars ensuring a stable mechanical interlock with concrete (form fit), the bond force of carbon rovings has so far been transmitted primarily via the coating of the textile, i.e. by an adhesive bond with the concrete matrix (material fit). However, this material fit must be activated over relatively large yarn areas, which does not allow material-efficient utilization of the mechanical load capacity of the textile reinforcement. Solutions involving profiled rovings promise significant improvements in the bonding behavior by creating an additional mechanical interlock with the concrete matrix. In order to achieve a form-fit effect between roving and concrete, a roving geometry inspired by ribbed steel bars has to be created. For this purpose, an innovative profiling process was developed and implemented.

3D meso-scale modelling of the bonding failure between corroded ribbed steel bar and concrete

Subjected to a corrosive environment, the macroscopic behavior of reinforced concrete structures is closely related to the bond property between rebar and concrete. For assessing the material performance and evaluating the nonlinear bond behavior of the interface between corroded ribbed rebar and concrete, and finally revealing the meso-mechanical failure mechanism of the reinforced concrete structure, we propose a 3D mesoscopic model in the current paper. The following elements that may influence the macroscopic behavior of the reinforced concrete are considered in the model: (1) the friction resistance and the mechanical interaction between corroded ribbed rebar, rust and concrete (2) the surface characteristic of threaded ribbed bar. The proposed mesoscopic model allows us to assess the influences of corrosion on the bond performance of corroded reinforced concrete through a two-stage analysis: after considering the expansive behavior of the reinforced concrete in the model, we apply a pull-out force on the corroded rebar to evaluate the bond-slip behavior between the corroded rebar and concrete. For validating our model, we compare the failure patterns and corroded bond stress-slip curves calculated by the model and obtained by experimental means and found a good consistency between them. Finally, a modified model was developed to describe the corroded bond stress-slip relationship. It has been found that when relative slip is applied, the concrete continues to crack along pre-existing cracks caused by corrosion products until the concrete splitting failure accorded. With the increase of corrosion level, the shape of the bond stress-slip curve is similar with a significantly degradation of the bond strength and peak slip, especially at small corrosion levels. Through comparing the proposed modified formula with the existing test data, one can find that the proposed modified formula can effectively characterize the corroded bond stress-slip relationship between deformed rebar and concrete.

Bond of Ribbed Steel Bar in High-Performance Steel Fiber Reinforced Expanded-Shale Lightweight Concrete

For the structural application of high-performance Steel Fiber Reinforced Expanded-shale Lightweight Concrete (SFRELC), a reliable bond of ribbed steel bar should be ensured. In this paper, an experimental study was carried out on the bond properties of ribbed steel bar embedded in SFRELC by the direct pull-out test. The SFRELC was produced with a strength grade of 35 MPa and a volume fraction of steel fiber as 0%, 0.8%, 1.2%, 1.6% and 2.0%, respectively. Fifteen groups of specimens were made with a central placed steel bar with diameter of 14 mm, 20 mm and 28 mm, respectively. Complete bond stress-slip curves were determined for each group of specimens, and the characteristic values of bond-stress and slip at key points of the curves were ascertained. Results show that the bond strength, peak-slip and residual bond strength increased with the increase of the volume fraction of steel fiber. With the increase of steel bar diameter, bond strength decreased while the peak-slip increased, and the descending curves became sharp with a decreased residual bond strength. Formulas for calculating the bond strength and peak-slip were proposed. The relationships were determined for the splitting bond strength, residual bond strength with the bond strength, the splitting bond slip and residual bond slip with the peak-slip. Combined with rational fitting analyses of bond strength and slip, a constitutive model was selected for predicting the bond stress-slip of ribbed steel bar in SFRELC.

Influence of high temperatures on the bond between carbon Fibre-Reinforced polymer bars and concrete

The effect of corrosion on reinforced concrete structures can lead to significant economic losses. Therefore, steel bars used in the concrete structures must be replaced with a different material that can withstand water contact without causing corrosion and can ensure the safe operation of the structure during its lifespan, even in adverse weather. Carbon-fibre-reinforced polymer (CFRP) bars are one of the materials that can replace steel bars and they have already been applied as a substitute previously. This study analyses the bonding of these bars with concrete at high temperatures and for longer time periods. It presents an experimental plan that involves a series of pullout trials at different ages, days, and thermal conditions in CFRP rods either treated with ribbed steel bars or that underwent sand-ribbed surface treatment. Some compression tests for each mixture were performed at the same ages and temperatures as the experimental plan in pullout to determine the influence of high temperatures on concrete. The study completed with some complementary tests on the CFRP rods using optical microscopy, scanning electron microscopy (SEM), and atomic force microscopy (AFM), from the evaluated pullout samples. The high temperature significantly affected the ribbed CFRP bars by diminishing their bond stress and did not affect the sanded CFRP bars. This uneven behaviour and the influence of high temperature on concrete resistance at the age of 180 d is justified.

In-plane seismic behavior of NSM strengthened adobe walls: Experimental evaluation of different reinforcements

This study focuses on the seismic strengthening of adobe walls using different reinforcing materials using the near-surface-mounted (NSM) technique. The test specimens comprise five adobe wall panels. Out of these, four specimens are strengthened with the three different NSM reinforcing materials of ribbed steel bars, sand-coated glass fiber-reinforced polymer (GFRP) bars, and sand-coated reeds. The strengthening procedure involves insertion of the reinforcing materials into the horizontal and vertical grooves cut symmetrically on both sides of the panels. The in-plane performance of the wall specimens is assessed under an incremental cyclic loading regime at the presence of the vertical pre-compression stress of 0.3 MPa. The results are described in terms of lateral resistance, ultimate displacement, ductility, hysteretic energy, and stiffness degradation. The envelopes of the hysteretic load–displacement curves thus obtained are then used in the seismic evaluation of the test specimens. While the results confirm the efficacy of all the reinforcing materials, the NSM steel bars are shown to be superior in this regard but the sand-coated reeds to be inferior to the other materials. The superiority of steel bars is attributed to their higher strength and elastic modulus. Nonetheless, the improvement achieved with the sand-coated reeds is considered to be satisfactory as well, particularly from sustainability and affordability viewpoints.

Prediction of fatigue damage in ribbed steel bars under cyclic loading with a magneto-mechanical coupling model

As a ferromagnetic material, the magnetization of ribbed steel bars will change with the development of fatigue damage under cyclic loading, which can be used to evaluate the fatigue damage state of steel bars. However, the quantitative relationship between fatigue damage and the variation in magnetization is still unclear, and the existing magneto-mechanical model cannot be applied to ribbed steel bars directly. To accurately predict the magnetization and the fatigue damage state during fatigue, it is also necessary to consider the influence of stress concentration caused by ribs on stress and fatigue life. This paper proposes a magneto-mechanical model suitable for ribbed steel bars, which use the Neuber law and Coffin-Manson relationship to determine the stress range and fatigue life under stress concentration. Additionally, the magnetic induction intensity of the HRB400 ribbed steel bar in the tensile fatigue test was measured to verify the proposed model, and the mechanism of the magnetization change trend during fatigue was analyzed in detail. Through the fatigue damage formula based on the magnetic indicator, the simulation and experimental comparison results show that the proposed model can effectively describe the fatigue damage state of ribbed steel bars in the fatigue.

Magnetic variation in construction steels under tensile stress. Empirical research with Helmholtz coils

Steel is responsible for providing resistance to flexotraction to reinforced concrete structures. Steel is responsible for providing reinforced concrete structures with a flexural strength. For this reason, it is important to study its behaviour under different tensile states. This study used measuring equipment that was able to determine variations in magnetic properties of B500-SD steel bars during standard tensile tests. The magnetic field generated by a Helmholtz coil was collected through a secondary circuit. This enables the induced electromotive force to relate with the steel deflection stages when subjected to the tests. Moreover, it was possible to determine the variation of magnetic permeability when submitting 12mm and 16mm diameter bars to different tensile states. This method could prove extremely useful in determining the tensile state of ribbed steel bars that are embedded into the concrete structure.

Mesoscale modelling of bond failure behaviour of ribbed steel bar and concrete interface

To explore the nonlinear bond behaviour between ribbed bar and concrete, combined with the characteristics of concrete meso-structure and ribbed bar surface characteristics and considering frictional resistance and the mechanical interlocking between rebar and concrete, a meso-scale model is established. Based on the good agreement between the simulation results and experimental results, the failure mechanism of bond between rebar and concrete is discussed, and the distribution characteristics of bond stress of steel bar are analysed. Furthermore, based on the meso numerical analysis method, the influence of friction coefficient between rebar and concrete on the failure mode of concrete and bond stress-slip curve was discussed, and the proportion of friction component in bond strength is obtained.

Numerical Evaluation of Bond Behavior of Ribbed Steel Bars or Seven-wire Strands Embedded in Lightweight Concrete

The bond-slip relationship between concrete and steel is significant in evaluating the nonlinear behavior of reinforced concrete structures. The force transmitted by the bond in reinforced concrete structures was studied numerically in high-strength, lightweight concrete with ribbed reinforcing steel bar or seven-wire strand, using ATENA 3D software. The first part of the study was a validation of the model based on the actual results of standardized pull-out tests using the software. Subsequently, the bond behavior was studied, where a four-point static bending test was modeled based on the real bond-slip relationship of the pull-out test. It was deduced that the ATENA 3D software can simulate the experimental tests and provide meaningful results. In addition, inferred from the numerical modeling, the maximum crack width and the mid-span deflection of the reinforced concrete beam increased when the bond stress between the concrete and the reinforcing steel bars was decreased. When a high amount of reinforcement (two strands) was used, concrete failure occurred before the strands yielded. However, further increase of the bond stress also decreased the maximum crack width and mid-span deflection. The failure occurred due to the increase in the strand yielding point by using one strand as a reinforcement of the beam.

Comparative studies on passivation and corrosion behaviors of two types of steel bars in simulated concrete pore solution

The corrosion behavior of two types of stirrups, a plain steel bar and a ribbed steel bar, were studied in this work. The results demonstrated that a better passive state was achieved on B500, which was due to a relatively higher concentration of Fe2+ oxides at the first 2 nm depths of the film, even though B500 film had relatively less FeOx contents, because Fe2+ oxides had a better protective property than Fe3+ oxides. Furthermore, the slightly lower donor density of B500 film in the M-S analysis results presented the much less point defect in the film, showing an increase in the anti-corrosion property of passive film. These contributed to a higher chloride threshold value of B500, 4 times higher than that of S275. Therefore, compared with S275, B500 stirrups could be more suitable for the application in the severe service environment.

3D meso-scale modelling of the interface behavior between ribbed steel bar and concrete

To explore the nonlinear bond behavior between ribbed bar and concrete, considering frictional resistance and the mechanical interlocking between rebar and concrete as well as the surface characteristic of crescent ribbed bar, a 3D meso-scale modelling approach is established. Comparisons between the simulation and experimental results indicate that the meso-scale method can provide good predictions of the interface behavior between concrete and deformed steel bar under confinement conditions. The bond failure mechanism and the propagation of internal crack of specimen were clearly studied and revealed based on the 3D simulations. Moreover, the influences of concrete strength gradation, ratio of cover thickness to bar diameter as well as stirrup confinement on bond stress-slip behavior, concrete failure mode and rebar stress were explored. The simulation results indicate that the meso-scale modelling method can well describe the bond failure process at the steel bar/concrete interface. It is found that increasing the concrete strength can delay the internal crack of the specimen and may change the failure mode of the specimen from splitting failure to pull-out failure. As concrete strength increases, the bond strength increases linearly, whereas the peak slip decreases slightly. The shape of bond stress-slip curve and the concrete failure modes are closely associated with the lateral confinements such as concrete cover thickness and the stirrup confinement. When the cover thickness and the stirrup confinement index reach a certain value, the bond failure would no longer be affected. In addition, the strain of stirrups increases continuously, the bond stress provided by stirrups increases first and then decreases.

Bond of FRP bars with different surface characteristics

This paper presents an extensive experimental study of the effect of surface characteristics on the bond behaviour of Fibre Reinforced Polymer (FRP) bars in concrete. A wide range of commercially available FRP bars with different surface profiles (total of 13 different surface configurations) were involved. For comparison, ribbed steel bars were used. To investigate whether the effect of surface characteristics is in interaction with other factors, further parameters were included in the study such as concrete compressive strength (35 and 66 MPa), bar diameter (6 to 12 mm) and test type (pull-out [P-O] and direct tension [DT] pull-out). This resulted a total of 200 P-O and 38 DT tests. DT test method was developed by the authors based on a similar test setup from the literature. Surface finish of the investigated FRP bars include sand coated (SC), helically wrapped (HW), helically wrapped and sand coated (HWSC), indented (In) and ribbed (Rb). Most of the applied bars are Glass FRP (GFRP), however, due to the similar physical and mechanical properties Basalt FRP (BFRP) bars were used as well. The bond behaviour of the bars was evaluated by bond strength, bond stress-slip relationship, representative bond stresses and failure mode. It was found that the bond strength as well as bond stress-slip behaviour and failure mode vary considerably depending on surface characteristics. Furthermore, even within the same surface category the bond strength difference can be significant (e.g., SC surface with different sand fineness). The concrete strength influences the bond strength even if it is higher than the limit stated in literature (approximately 30 MPa). Furthermore, the bond strength results of all FRP bars were consistently higher than those of steel bars. The highest slip value to reach the bond strength was observed for HW FRP bars, while the lowest for SC bars. Some results reported in this paper considerably differ from those previously reported in other papers based on testing similar bars. The difference, in terms of bond strength, can be explained by the alteration of surface configuration, the improvements in material properties and fabrication processes. Finally, the test setup was found to affect the measurable bond strength.

Evaluating Stress-Strain Properties of Reinforcing Steel for Reinforced Concrete

Abstract The stress-strain properties of reinforcing steel for reinforced concrete are related to the design of reinforced concrete structures. In China Codes, steel bars for the prestressing of concrete (PCB) and hot-rolled ribbed bars in grade 600 (HRB600) were introduced to design concrete structures. However, the stress-strain properties of high-strength steel bars are not defined by the standard. In this paper, reinforcing steel for reinforced concrete in a China Code included hot-rolled plain bars (HPB), HRB, cold-rolled ribbed steel bars (CRB), PCB, hot-rolled wire rod for prestressed steel (PSW), and screw-thread steel bars for the prestressing of concrete (PSB), which were tested under axial tension. Results showed that the reinforcing steel was divided into two types: HPB, HRB, and CRB600H with yield plateau and PCB, PSW, PSB, and CRB550 without. Based on the experimental results, the tensile mechanical indicators of reinforcing steel were determined and the stress-strain curves prediction models of reinforcing steel were developed. The stress-strain curves prediction models of steel bars can predict the tensile properties of steel bars accurately, which can be used in finite element software to simulate the tensile properties of steel bars and explore the stress development of steel bars in concrete structures.

Three-Dimensional Nonlinear Finite Element Modeling for Bond Performance of Ribbed Steel Bars in Concrete Under Lateral Tensions

Development of experimental studies in bond behavior between deformed bar and concrete under complex stress conditions in the last 2 decades is significantly affecting the concrete design specification. This article presents a rib-scale finite element model (FEM) to study the bond behavior of deformed bar in concrete under lateral tensions. In this model, detailed modeling including the reinforcing bar ribs and the concrete keys in contact region is realized with real geometric parameters. At the concrete–bar interface, surface-to-surface contacts with tie constraints are used and relative sliding or separation between contact surfaces are inhibited; adhesion between concrete and deformed bar is ignored. A user-defined subroutine named VUSDFLD in ABAQUS software was incorporated into the concrete damaged plasticity (CDP) model to acquire more accurate concrete constitutive relations. The FEM is calibrated using pullout test data from published papers. The simulation results show that all specimens failed in splitting mode. The lateral tension is an adverse factor on the bond property between steel bar and concrete, both the ultimate bond strength and the slip at the peak bond stress decrease with the increase of the lateral tensions. Comparison of computational simulation with the experimental data indicates that the proposed model gives a reasonable prediction of the bond stress–slip curves as well as the concrete crack patterns.

Bond properties of steel and sand-coated GFRP bars in Alkali activated cement concrete

The bond performance of glass fibre reinforced polymer (GFRP) bars and that of steel bars embedded in Alkali Activated Cement (AAC) concrete are analysed and compared using pull-out specimens. The bond failure modes, the average bond strength and the free end bond stress-slip curves are used for comparison. Tepfer’s concrete ring model is used to further analyse the splitting failure in ribbed steel bar and GFRP bar specimens. The angle the bond forces make with the bar axis was calculated and used for comparing bond behaviour of ribbed steel bar and GFRP bars in AAC concrete. The results showed that bond failure mode plays a significant role in the comparison of the average bond stress of the specimens at failure. In case of pull-out failure mode, specimens with ribbed steel bars showed a higher bond strength while specimens with GFRP bars showed a higher bond stress in case of splitting failure mode. Comparison of the bond stress-slip curves of ribbed steel bars and GFRP bars depicted that the constant bond stress region at the peak is much smaller in case of GFRP bars than ribbed steel bars indicating a basic bond mechanism difference in GFRP and ribbed steel bars.