Low-Cycle Fatigue Properties of Bimetallic Steel Bar with Buckling: Energy-Based Numerical and Experimental Investigations.

A bimetallic steel bar (BSB) consisting of stainless-steel cladding and carbon steel substrate exhibits excellent corrosion resistance and good mechanical properties. The bimetallic structure of BSBs may affect their low-cycle fatigue performance, and current investigations on the above issue are limited. In this study, the low-cycle fatigue properties of bimetallic steel bars (BSBs) with inelastic buckling were investigated. Experiments and numerical studies were conducted to investigate the low-cycle fatigue capacity for BSBs, considering buckling. The buckling mode of BSBs is discussed. The hysteretic loops and energy properties of BSBs with various slenderness ratios (L/D) and fatigue strain amplitudes (εa) are investigated. With increases in the L/D and εa, the original symmetry for hysteresis loops disappears gradually, which is caused by the buckling. A predictive equation revealing the relation between the εa and fatigue life is suggested, which considers the effects of the L/D. A numerical modelling method is suggested to predict the hysteretic curves of BSBs. The effect of buckling on the stress and energy properties of BSBs is discussed through the numerical analysis of 44 models including the effects of the L/D, εa, and cladding ratios. The numerical analysis results illustrate that the hysteresis loops of BSBs with various εa values exhibit similar shapes. The increase in the cladding ratio reduces the peak stress and the dissipated energy properties of BSBs. The hysteresis loop energy density decreases by about 3% with an increase of 0.1 in the cladding ratio. It is recommended that the proportion of stainless steel inBSBs should be minimized once the corrosion resistance requirements are met.

Steel bar penetrating cervical spinal canal without neurological injury: A case report.

BACKGROUND: We report a rare case of cervical spinal canal penetrating trauma and review the relevant literatures. CASE SUMMARY: A 58-year-old male patient was admitted to the emergency department with a steel bar penetrating the neck, without signs of neurological deficit. Computed tomography (CT) demonstrated that the steel bar had penetrated the cervical spinal canal at the C6-7 level, causing C6 and C7 vertebral body fracture, C6 left lamina fracture, left facet joint fracture, and penetration of the cervical spinal cord. The steel bar was successfully removed through an open surgical procedure by a multidisciplinary team. During the surgery, we found that the cervical vertebra, cervical spinal canal and cervical spinal cord were all severely injured. Postoperative CT demonstrated severe penetration of the cervical spinal canal but the patient returned to a fully functional level without any neurological deficits. CONCLUSION: Even with a serious cervical spinal canal penetrating trauma, the patient could resume normal work and life after appropriate treatment.

Inhibition performance of uniconazole on steel corrosion in simulated concrete pore solution: An eco-friendly way for steel protection.

Corrosion inhibitors play a vital role in impeding the corrosion process of steel bars within concrete structures exposed to corrosive environments. Nevertheless, conventional corrosion inhibitors pose environmental risks. In contrast, contemporary studies have explored corrosion inhibitors that are eco-friendly. However, these inhibitors are burdened by high costs and complex production processes, impeding the widespread application in concrete structures. Consequently, this study presents an innovative solution by incorporating uniconazole, an agricultural fungicide, as a corrosion inhibitor for steel bars in concrete structures. The steel bars were exposed to corrosion within a simulated concrete pore solution containing 0.6 mol/L NaCl, both with and without the presence of uniconazole. The morphology and hydrophilicity of the steel bar surface were investigated via optical microscope and contact angle experiments. Electrochemical tests (open circuit potential, potentiodynamic polarization, electrochemical impedance spectroscopy, and Mott-Schottky analysis) and X-ray photoelectron spectroscopy were employed to investigate the corrosion inhibition performance and mechanism of uniconazole. The results demonstrate that uniconazole elevates the hydrophobicity and contributes to the corrosion inhibition of steel bars. Electrochemical test results indicate that as the concentration of uniconazole increases from 1 × 10-4 mol/L to 1 × 10-3 mol/L, the inhibition efficiency likewise demonstrates a corresponding increase, escalating from around 50 %-90 %. Uniconazole molecules function as mixed-type inhibitors, exhibiting characteristics of both anode-type and cathode-type inhibitors. The adsorption of uniconazole enhances the stability and thickness of the passive-adsorbed layer on the steel surface, effectively impeding the charge transfer process and obstructing the interaction of corrosive substances with the base metal. In summary, the application of uniconazole exhibits the highlights of efficient, cost-effective, environmentally friendly, and the potential for scalable production. This positions uniconazole as a promising candidate for use as a corrosion inhibitor in the domain of concrete structures.

Axial Compressive Behavior of Cross-Shaped CFST Stub Columns with Steel Bar Truss Stiffening.

Concrete-filled steel tube (CFST) columns have been widely used in residential buildings due to their high bearing capacity, good ductility, and reliable seismic performance. However, conventional circular, square, or rectangular CFST columns may protrude from the adjacent walls, resulting in inconvenience in terms of the arrangement of furniture in a room. In order to solve the problem, special-shaped CFST columns, such as cross-shaped, L-shaped, and T-shaped columns, have been suggested and adopted in engineering practice. These special-shaped CFST columns have limbs with the same width as the adjacent walls. However, compared with conventional CFST columns, the special-shaped steel tube provides weaker confinement to the infilled concrete under axial compressive load, especially at concave corners. The parting at concave corners is the key factor affecting the bearing capacity and ductility of the members. Therefore, a cross-shaped CFST column with steel bar truss stiffening is suggested. In this paper, 12 cross-shaped CFST stub columns were designed and tested under axial compression loading. The effects of steel bar truss node spacing and column-steel ratio on the failure mode, bearing capacity, and ductility were discussed in detail. The results indicate that the columns with steel bar truss stiffening can change the final deformation mode of the steel plate from single-wave buckling to multiple-wave buckling, and the failure modes of columns also subsequently change from single-section concrete crushing failure to multiple-section concrete crushing failure. The steel bar truss stiffening shows no obvious effect on the axial bearing capacity of the member but significantly improves the ductility. The columns with a steel bar truss node spacing of 140 mm can only increase the bearing capacity by 6.8% while nearly doubling the ductility coefficient from 2.31 to 4.40. The experimental results are compared with those of six design codes worldwide. The results show that the Eurocode 4 (2004) and the Chinese code CECS159-2018 can be safely used to predict the axial bearing capacity of cross-shaped CFST stub columns with steel bar truss stiffening.

Effect of Corrosion on the Bond Behavior of Steel-Reinforced, Alkali-Activated Slag Concrete.

Alkali-activated slag concrete (ASC) is regarded as one of the most promising sustainable construction materials for replacing ordinary Portland cement concrete (OPC) due to its comparable strength and outstanding durability in challenging environments. In this study, the corrosion of steel bars embedded in ASC and OPC was studied by means of an electrically accelerated corrosion test of steel bars in concrete. Meanwhile, the bond performance of the corroded steel bars embedded in ASC was tested and compared with corresponding OPC groups. The results showed that ASC and OPC behaved differently in terms of bond deterioration. The high chemical resistance of ASC decreased the corrosion of steel bars and, thus, increased the residue bond strength and the bond stiffness.

Impact of Corrosion on the Bond Strength between Concrete and Rebar: A Systematic Review.

Corrosion of the reinforcement affects more than the cross-sectional area of the rebar. The volume of steel also increases due to expansive corrosion products, leading to the cracking, delamination, and spalling of concrete. As a result, the bond capacity between concrete and rebar is affected. Researchers have extensively examined the impact of corrosion on the bond strength between concrete and rebar to propose empirical, theoretical, or numerical predictive models. Therefore, research programs on this topic have increased rapidly in recent years. This article presents a systematic literature review to explore experimental methods, outcomes, and trends on this topic. The Web of Science search collected 84 relevant research articles through a rigorous selection. Key factors that affect bond strength degradation, including concrete cover, concrete strength, and stirrups, have been documented. However, a general model is still unavailable due to discrepancies caused by differences in testing methods to evaluate the effect of corrosion on bond strength. Furthermore, researchers attempted to clarify the degradation mechanism of bond strength affected by corrosion. As a result, new alternatives have been proposed to build a practical model to assess the bond strength deterioration of corroded structures.

Effect of NaCl Solution and Simulated Concrete Pore Solution Environment on the Efficiency of Steel Bar Energized Corrosion.

As the main problem of the durability deterioration of concrete structures, the corrosion of steel bars is usually made by the method of electrified corrosion with a short cycle and low cost. However, there is a big difference between the actual corrosion depth and the theoretical corrosion depth after the reinforcement is electrified. In this paper, through the accelerated corrosion test of steel bars, the change law and influence factors of corrosion efficiency of steel bars in concrete simulated pore solution and NaCl solution are studied. The test results show that the corrosion efficiency of reinforcement in the NaCl solution is higher than that in the concrete simulated pore solution, and the corrosion efficiency in the NaCl solution changes in two stages with the corrosion degree of reinforcement. The corrosion efficiency of concrete in the simulated pore solution decreases with the increase of corrosion degree of reinforcement, which is more significant than that in the NaCl solution. Under the same conditions, the corrosion efficiency is higher in the chloride ion solution with high concentration, and the influence of chloride ion concentration change in the simulated pore solution of concrete on the corrosion efficiency is more significant. The corrosion efficiency of reinforcement under low current density is higher than that under high current density.

The Influence of Freeze-Thaw Cycles and Corrosion on Reinforced Concrete and the Relationship between the Evolutions of the Microstructure and Mechanical Properties.

Freeze-thaw cycles (FTCs) and steel bar corrosion (SBC) are the most common service conditions of hydraulic concrete and have significant impacts on its durability. Using pullout and microscopic tests of different FTC and SBC rates, we selected the mass loss rate, ultrasonic velocity, bond strength and bond slip in order to describe the changes in the macro-properties, and also selected the porosity and pore size distribution as micro-parameters in order to explore the influence of FTCs and SBC on the mechanical properties of hydraulic concrete. The results showed that the bond strength decreased as the FTCs increased due to the microstructure damage caused by FTC and SBC, which affects the mechanical properties. A corrosion rate of ≤3% offset the damage caused by 50 FTCs. FTCs and SBC resulted in superimposed damage effects on the concrete. In addition, we established a bond strength damage model based on the joint FTCs and SBC and quantitatively described the degradation law of the macro-mechanical properties. The analysis shows that the influence of FTCs on the bond strength was greater than that of the SBC. These research results can provide a reference and experimental support for the frost-resistant design and durability prediction of hydraulic concrete structures in cold environments.

Anti-Corrosion Performance of Migratory Corrosion Inhibitors on Reinforced Concrete Exposed to Varying Degrees of Chloride Erosion.

This study investigated the anti-corrosion performance of commercial amino alcohol migratory corrosion inhibitors (MCIs) on concrete that underwent varying degrees of chloride erosion. Electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PD), scanning electron microscopy, and energy dispersive spectroscopy (SEM-EDS) analyses were performed to study the anti-corrosion performance and mechanism of the MCIs on the steel bars. The results indicated that the corrosion resistance of the steel bars in concrete was significantly improved by coating with the MCIs, and the earlier the specimens were coated with the MCIs, the higher the anti-corrosion efficiency. The anti-corrosion efficiency was 55.35% when the MCIs coating was applied before chloride erosion; however, the anti-corrosion efficiency decreased to 3.40% when the MCIs coating was applied after the ninth drying-wetting cycle. The improvement in corrosion resistance of the steel bar in concrete coated with MCIs was due to the protective MCIs-molecule film that formed on the steel bar surfaces, and the oxidative dissolution of iron at the anode was effectively inhibited by the MCIs coating.

Bond Performance of Steel Bar and Fly Ash-Based Geopolymer Concrete in Beam End Tests.

This paper presents a comprehensive investigation of the bond characteristics of steel bar reinforced geopolymer concrete (GPC). The ASTM A944 beam end tests were conducted on GPC beams reinforced with plain or ribbed bars. The bond-slip curves and the bond strength of GPC beams were obtained. The relationship between the bond stress and relative slip in plain and ribbed bar reinforced GPC has been represented by empirical formulae. The bond testing results were compared with those of corresponding ordinary Portland cement concrete (OPC) using statistical hypothesis tests. The results of hypothesis testing showed that GPC was significantly superior to OPC in terms of bond capability with plain bars and bond stiffness with ribbed bars. The statistical analysis indicated that the bond-slip relations derived for OPC are inapplicable to GPC; thus, new bond-slip relations are suggested to estimate the development of bond stress and relative slip between GPC and steel bars.

Algorithmic-Aided Approach for the Design and Evaluation of Curvilinear Steel Bar Structures of Unit Roofs.

Rationalization in structural design in the field of steel structures mostly consists inreducing structural material. The aim of this work was to develop an algorithmic-aided, original and practical approach to shaping curvilinear steel bar structures of modular roofs, enabling their optimization. The first stage of shaping consists in creating algorithms that define the structures of shelters made of four roof units. Algorithmic definitions of the structures made it possible to obtain many variants of the roof structures with the adopted preliminary criteria. In order to evaluate the effectiveness of the individual variants, the genetic optimizations of the structures' forms were carried out. Assuming that the structures were loaded with self-weights, the cross-sections of the structures' members were optimized with the permissible deflections, while the structures' weights were the optimization criteria. This allowed us to eliminate the design variants unfavorable in terms of shape and weight. In contrast, the structures with the most advantageous properties were then optimized for weight under snow and wind loads. The research allowed us to notice how the shapes of the structures influenced their efficiency. The dual approach proposed for shaping, which takes advantage of the generative design and consistent flow of information during shaping, allowed us to achieve better solutions compared to the traditional approach.

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.

Novel approach to removing a steel bar extending from the scrotum to anterior abdominal wall: a case report.

Foreign body penetration from the scrotum is not rare. If a large and sharp foreign body pierces through an existing wound, it likely must be extended to improve exposure. Therefore, many traumatologists attempt to minimize the surgical wound caused by the removal of the foreign body. We describe a case of a foreign object penetrating from the scrotum to anterior abdominal wall. Our novel surgical approach is safe and feasible to use and provides minimal scarring, thereby allowing rapid recovery.

A prospective study on long-term trace metal accumulation in hair: Is there any difference between minimally invasive repair of pectus excavatum and carinatum?

BACKGROUND: To date, there is no study about trace metal level increases in hair after stainless steel pectus bar implantation. We aimed to determine whether there was any significant increase in the levels of trace metals in the hair of children who underwent minimally invasive repair of pectus excavatum (MIRPE) and minimally invasive repair of pectus carinatum (MIRPC). MATERIALS AND METHODS: In this prospective study, we collected the data of 223 patients who underwent MIRPE and MIRPC between November 2013 and August 2020. The levels of main components of the stainless steel pectus bar ("PES", Medxpert GmbH, Escbach, Germany) namely Cr, Fe, Ni, and Mo in hair were analyzed. The study involved two study groups: A group of patients who underwent MIRPE with a single bar (n = 112) and a group of patients who underwent MIRPC (n = 71). Both groups were analyzed in two different timelines: A group of consecutive patients prior to bar implantation and a group of the same patients who underwent bar removal after a mean time of 34.6 ± 5.1 months. RESULTS: Statistically significant increases in all studied trace metal levels were observed in the single-bar MIRPE group. In the MIRPC group, the accumulation of studied trace metals was no statistically significant. The double-bar MIRPE group had higher trace metal increase rates compared to single-bar MIRPE group (p>0.05). CONCLUSION: In our study; increases in iron, chrome, nickel and molybdenum levels were observed in both MIRPE and MIRPC patients by hair trace metal analysis; but these increases were statistically significant in only MIRPE group.

Non-Destructive Testing of Steel Corrosion Fluctuation Parameters Based on Spontaneous Magnetic Flux Leakage and Its Relationship with Steel Bar Diameter.

In an actual structure, the arrangement of steel bars is complicated, there are many factors affecting the corrosion of steel bars, and these factors affect each other. However, accurately reflecting the corrosion of steel bars in actual engineering through theoretical calculations is difficult. Besides, it is impossible to detect and evaluate steel bars rust completely and accurately. This article is based on spontaneous magnetic leakage detection technology and adopts the method of stage corrosion and scanning along the reinforcing bar. Based on spontaneous magnetic flux leakage detection technology, the linear change rate of the tangential component curve of the magnetic flux leakage signal generated after the corrosion of a steel bar is studied, and a comparison is made between the steel bar coated concrete samples with different steel bar diameters. In this paper, the "origin of magnetic flux leakage signal" is defined as a reference point, which is convenient for effectively comparing the magnetic signal curves under all operating conditions. Besides, the "rust-magnetic fluctuation parameter" is proposed to accurately reflect the sudden change of leakage magnetic field caused by disconnection due to the corrosion of a steel bar. A new data processing method is provided for the non-destructive testing of steel corrosion using the spontaneous magnetic flux leakage effect, which can effectively reduce the influence of steel bar diameter on magnetic flux leakage signal and improve the precision of non-destructive testing technology of steel bar corrosion using the metal magnetic memory effect.

Bond Properties of Steel Bar in Concrete under Water Environment.

The present study concerns the bond behavior of steel bar in concrete under a water environment. This topic was put forward because of the changes of concrete under a water environment and the importance of reliable anchorage of steel bar for reinforced concrete structures. Thirty bond specimens with deformed steel bars were immersed in water and experimentally studied by pull-out tests. The soaking time from 28 day to 360 day and the cubic compressive strength of concrete with 20 N/mm2 and 40 N/mm2 were considered as the main parameters. The results indicate that the moisture content, compressive strength, and splitting tensile strength of concrete are affected by the water environment; the splitting tensile strength varies almost linearly with the compressive strength of concrete; and the descent portion of the bond-slip curve dropped slowly owing to the confinement of stirrups. On the basis of the test data, the formulas for the prediction of bond strength, residual strength, and the corresponding slips with different soaking time are proposed. Finally, the constitutive relation of bond-slip with two portions in the water environment is established with good agreement with the experimental bond-slip curves.

Monitoring of Epoxy-Grouted Bonding Strength Development between an Anchored Steel Bar and Concrete, Using PZT-Enabled Active Sensing.

Anchored steel bars have been widely used in retrofitting of existing concrete structures. The bonding strength between the anchored steel bar and the concrete is critical to the integrity of the strengthened concrete structure. This paper presents a method to monitor epoxy-grouted bonding strength development by using a piezoceramic-enabled active sensing technique. One concrete beam with an anchored steel bar was involved in the monitoring test, and two concrete beams with six anchored steel bars were used in the pull-out test. To enable the active sensing, a Lead Zirconate Titanate (PZT) patch was bonded to the surface of the exposed end, and piezoceramic smart aggregates were embedded in each concrete specimen. During the monitoring experiment, signals from PZT sensors and smart aggregates were acquired at intervals of 0, 20, 40, 60, 80, and 100 min. In addition, a pull-out test was performed on each of the remaining six anchored steel bars in the two concrete beams, while the signal was recorded in the test. Furthermore, a wavelet packet analysis was applied to analyze the received signal energies to investigate the bonding strength development between the concrete and the anchored steel bar during the epoxy solidification process. The test results demonstrate the effectiveness of the proposed method in monitoring the bonding strength development between the anchored steel bar and the concrete, using the PZT-enabled active sensing.

Research on Internal Force Detection Method of Steel Bar in Elastic and Yielding Stage Based on Metal Magnetic Memory.

Based on the metal magnetic memory effect, this paper proposed a new non-destructive testing method for the internal tensile force detection of steel bars by analyzing the self-magnetic flux leakage (SMFL) signals. The variation of the SMFL signal of the steel bar with the tensile force indicates that the curve of the SMFL signal has a significant extreme point when the tensile force reaches about 65% of the yield tension, of which the first derivative curve has extreme points in the elastic and yielding stages, respectively. To study the variation of SMFL signal with the axial position of the steel bar under different tensile forces, a parameter reflecting the fluctuation of the SMFL signal along the steel bar is proposed. The linear relationship between this parameter and the tensile force can be used to quantitatively calculate the tensile force of steel bar. The method in this paper provides significant application prospects for the internal force detection of steel bar in the actual engineering.

Management of a Steel Bar Injury Penetrating the Head and Neck: A Case Report and Review of the Literature.

BACKGROUND: Nonmissile penetrating injuries to the head and neck caused by a steel bar are rare, and a standard management strategy is lacking. CASE DESCRIPTION: A 42-year-old woman sustained a steel bar injury with penetration of the head and neck. Computed tomography and three-dimensional reconstruction were performed for preoperative evaluation. Digital subtraction angiography was performed to confirm potential vascular injury. The steel bar was successfully removed through an open surgical procedure by a multidisciplinary team. CONCLUSIONS: Relevant literature regarding nonmissile penetrating injuries involving a steel bar was reviewed to propose appropriate management strategies. Comprehensive imaging evaluation and prompt surgery by a multidisciplinary team contributed to the successful removal of the steel bar.

A Recent Progress of Steel Bar Corrosion Diagnostic Techniques in RC Structures.

Corrosion of steel bar is one of key factors undermining reinforced concrete (RC) structures in a harsh environment. This paper attempts to review the non-destructive procedures from the aspect of the corrosion measurement techniques, especially their advantages and limitations. Systematical classification of diagnostic methods is carried out to determine any probable corrosion issues before the structures become severe, and helps choose the suitable method according to different construction features. Furthermore, the three electrochemical factors method is introduced to inspire researchers to combine various techniques to improve corrosion evaluation accuracy. The recommendations for future work are summarized, in conclusion.