Steel Bars In Structures Research Articles

Research Progress on the Transport and Prediction of Chloride Ions in Concrete Structures

Reinforced concrete structures are widely used in practical engineering, and the durability issues of such structures under chloride environments have been a hot research topic. Chloride ions can cause corrosion of internal steel bars in structures under the action of chloride salt, leading to structural cracking, decreased bearing capacity, and ultimately affecting the structural safety during service life. Therefore, comprehensive and systematic research on chloride ion transport and prediction in concrete structures is crucial. This paper reviews the recent research progress on chloride ion transport in concrete structures both domestically and internationally, introduces the latest research results on chloride ion transport mechanisms, transport laws, prediction methods, and points out the limitations and future research directions in existing research on chloride ion transport and prediction in concrete structures.

Experimental Study and Discrete Analysis of Compressive Properties of Glass Fiber-Reinforced Polymer (GFRP) Bars.

Glass fiber-reinforced polymer (GFRP) has superior characteristics over traditional steel, such as lightweight, high strength, corrosion resistance and high durability. GFRP bars can be a useful alternative to steel bars in structures, specifically those in highly corrosive environments, as well as structures subjected to high compressive pressure such as bridge foundations. Digital image correlation (DIC) technology is used to analyze the strain evolution of GFRP bars under compression. It can be seen from using DIC technology that the surface strain of GFRP reinforcement is uniformly distributed and increases approximately linearly, and brittle splitting failure of GFRP bars happens due to locally occurring high strain at the failure stage. Moreover, there are limited studies on the use of distribution functions to describe the compressive strength and elastic modulus of GFRP. In this paper, Weibull distribution and gamma distribution are used to fit the compressive strength and compressive elastic modulus of GFRP bars. The average compressive strength is 667.05 MPa and follows Weibull distribution. Moreover, the average compressive elastic modulus is 47.51 GPa and follows gamma distribution. In order to verify that GFRP bars still have certain strength under compressive conditions, this paper provides a parameter reference for their large-scale application.

Correlation between Mechanical and Magnetic Properties of Structural Steel Bar due to Variable Loading Conditions

Correlation between Mechanical and Magnetic Properties of Structural Steel Bar due to Variable Loading Conditions

Prediction of buckling force in hourglass-shaped specimens

It is important to avoid buckling during low-cycle fatigue testing. The buckling load is dependent on the specimen shape, material properties, and the testing machine. In the present investigation of hourglass-shaped specimens the importance of the diameter to radius of curvature is examined. Diameters of 5 and 7 mm are examined with a ratio of radius of curvature to diameter of 4, 6, and 8. The machine used is an Instron 8800 with elongated rods for a climate chamber. This leads to a reduced stiffness of the machine during compression testing. A finite element model (in Abaqus) is developed to identify the critical buckling force. For hourglass-shaped specimens, buckling means onset of sideways movement, without a drop in the applied load which is typical for conventional Euler buckling. The onset of sideways movement is identified experimentally by analysis of the data from extensometer and the load cell. This model is verified by experiments and fits within 0.6 to − 11% depending on the specimen diameter and diameter to radius of curvature ratio. The smallest deviations are obtained for the 7-mm-diameter specimen with deviation varying from 0.6 to − 3.3% between the model and the experiments. The current investigation is done with a commercially available hot rolled structural steel bar of Ø16 mm.

Corrosion monitoring in steel bars using Laser ultrasonic guided waves and advanced signal processing

Ultrasonic scanning can present a detailed map of the invisible internal degradation of objects. However, their utility is limited in the case of built facilities as their dimensions are too large for the currently used piezoelectric transducers to penetrate. This paper presents an investigation with high power Laser ultrasonic guided waves combined with an advanced signal processing for discerning corrosion in structural steel bars. The pros and cons of Laser ultrasonic monitoring vis-à-vis traditional piezoelectric systems have been highlighted. Dispersion curves for the steel bars have been deduced to understand its modal characteristics. The variations in time-frequency spectra due to the spread in corrosion have been correlated with the predominant propagation modes in the bar. The time-frequency spectral pattern obtained from the proposed signal processing techniques are calibrated with the mass loss due to corrosion. A K-means cluster-based approach has been used to predict the state of corrosion.

Case Study – When A Roof is More Than a Roof

The repurposing of existing buildings is becoming more prevalent. But changing a buildings use is not without concern. A European Company purchased an existing warehouse located north of Chicago, Illinois, USA as the space filled their needs for the layout of their manufacturing equipment. Producing medical grade synthetic mesh requires interior temperatures of 90°F (32.2C) with a relative humidity of 90%. The roof of the facility was low-sloped trapezoidal standing seam metal roof system that was watertight in all types of precipitation: Rain, snow, ice. The insulation, below the roof panels and above the steel purlins, was vinyl face fiberglass batt laid over the structural steel bar joist and pinned by the metal roof panels. Shortly after manufacturing commenced, water build-up in the batt insulation during winter started and was so severe that the vinyl facing would belly downward and split the lap seams, which would release the water, soiling the 2m wide rolls of mesh that then did not meet medical standards and had to be discarded. This case study will review the issues that arose out of repurposing a warehouse to a manufacturing facility and what the solution to correct moisture related issues. Hutchinson Design Group, Ltd. of Barrington, Illinois, was retained to investigate the conditions, determine the causes and develop a corrective solution.

Synthesis and characterisation of TiO 2 nanoparticles/Fe 2 O 3 waste chips composite

Water contamination along with the environmental issues resulted by industrial wastewaters have caused a trend in applying semiconducting photocatalysts, among which TiO2 composites have been particularly focused on to overcome the drawbacks of titanium(IV) oxide also known as titania. In the current investigation, waste chips of a structural steel bar with the chemical composition of Fe2O3 were utilised to obtain the TiO2–Fe2O3 composite. X-ray diffraction (XRD), field-emission scanning electron microscopy, energy dispersive spectroscopy, diffusive reflectance spectra, and Brunauer–Emmett–Teller analyses were made to evaluate the composition and structure of the samples. Furthermore, the photocatalytic performance of the samples was studied by methyl orange (MeO) degradation. XRD spectra proved the presence of anatase and Fe2O3 phases in the sample of 10%wt. Fe2O3. The results indicate that as the Fe2O3 content rises, the bandgap narrows. However, the specific surface area enlarges as this amount goes up to a certain limit (10%wt.), from which any further increase leads to a reduction in the specific surface area. The obtained results of MeO decolourisation presented the Fe2O3 of 10%wt. and bandgap of 2.72 eV, and the specific surface area of 63 m2/g to be of the highest efficiency (96%).

Fire resistance of locally produced 500W structural steel bars

Steel has been used for many decades in structural applications because of its good combination of mechanical properties. In recent years in Bangladesh the demand for TMT 500W steel bars has increased profoundly, for its higher strength and good ductility. But fire remains one of the serious potential risks to most buildings and structures. To understand the effect of fire on mechanical properties of steel bars at elevated temperature a locally produced 500W TMT bar of 8 mm diameter has been investigated. Both macroscopy and microscopy were carried out to reveal different zones such as hardened case, soft core and transition zone in the cross-section and microstructure respectively of the steel bars in the as received condition. Finally, high temperature tensile tests were conducted at 500°C, 600°C, 650°C in steady state method at a strain rate of 0.5mm/min and the results at these 3 temperatures were noted. Data generated from the room temperature and high temperature tensile tests were compared. The test results demonstrated that the high temperature severely degrades the tensile strength of the 500W TMT steel bars and they can hardly bear any load at temperature above 600°C.

Fatigue Life Dependency on the Cleanliness and Ductility of Structural Steels

Plain concrete is very brittle and weak. It cannot withstand sudden shock, cyclic load and high level of tensile stress. So, concrete is reinforced by various types of structural steels. To reduce the overall weight of the RCC structures, worldwide practice is to use high strength structural steels along with high strength concrete. In this research work low strength high ductility (300 grade) and high strength moderate ductility (500 grade) locally produced steel bars of 20mm diameter were used. They were then characterized by means of chemical composition, microstructure, size and distribution of inclusion particles, tensile and fatigue tests. The fracture surfaces of the failed fatigue samples were observed under optical and scanning electron microscopes. After detail investigation, experimental results suggest that compared to ductility, cleanliness of the structural steel bars are much more important for better fatigue life of the RCC structures.

Corrosion Effects on Residual Structural Capacity of Resins / Exudates Inhibited Steel Reinforcement Flexural Beam

The study investigated the effects of corrosion on the residual structural steel bar capacity of resins/exudates inhibited and non-inhibited reinforced concrete beam members. Steel reinforcements were coated with moringa oleifera lam resins/exudates from trees extract (Inorganic inhibitors), embedded into concrete beam members and exposed to sodium chloride medium representing laboratory harsh saline marine environment. Corrosion acceleration potential test was conducted on 27 samples of non-corroded, uncoated and coated resins/exudates paste thicknesses of steel bar and simulated for 60 days, after 30 days, initial concrete cured. Results obtained showed corrosion potential presence on uncoated members with cracks and spalling. Further recorded results on non-corroded flexural strength test of failure load 29.09%, midspan deflection 28.30%, tensile strength 12.03% and elongation 31.50%, for coated beam members, failure load 29.42%, midspan deflection 27.42%, tensile strength 12.09% and elongation 31.80%, for corroded beam members, failure load decreased by 22.50%, midspan deflection increased by 39.30%, tensile strength decreased to 10.17% and elongation by increased 46.30%. The entire experimental results showed that corroded specimens has lower flexural load, higher midspan deflection, lower tensile strength and higher elongation due to loss of steel bar fibre from degradation effect from corrosion, inhibitors served as protective coating against corrosion, but no strength was added to steel members.

Corrosion Effects on Residual Structural Capacity of Resins / Exudates Inhibited Steel Reinforcement Flexural Beam

The study investigated the effects of corrosion on the residual structural steel bar capacity of resins/exudates inhibited and non-inhibited reinforced concrete beam members. Steel reinforcements were coated with moringa oleifera lam resins/exudates from trees extract (Inorganic inhibitors), embedded into concrete beam members and exposed to sodium chloride medium representing laboratory harsh saline marine environment. Corrosion acceleration potential test was conducted on 27 samples of non-corroded, uncoated and coated resins/exudates paste thicknesses of steel bar and simulated for 60 days, after 30 days, initial concrete cured. Results obtained showed corrosion potential presence on uncoated members with cracks and spalling. Further recorded results on non-corroded flexural strength test of failure load 29.09%, midspan deflection 28.30%, tensile strength 12.03% and elongation 31.50%, for coated beam members, failure load 29.42%, midspan deflection 27.42%, tensile strength 12.09% and elongation 31.80%, for corroded beam members, failure load decreased by 22.50%, midspan deflection increased by 39.30%, tensile strength decreased to 10.17% and elongation by increased 46.30%. The entire experimental results showed that corroded specimens has lower flexural load, higher midspan deflection, lower tensile strength and higher elongation due to loss of steel bar fibre from degradation effect from corrosion, inhibitors served as protective coating against corrosion, but no strength was added to steel members.

Producing Structural-Steel Bar from Continuous-Cast Billet

The expanded use of continuous-cast billet in the production of structural-steel bar is considered. The quality of 135 × 135 mm continuous-cast billet produced on a standard continuous-casting machine and the bar derived from it is evaluated. At more recently built plants, the production of quality bar from continuous- cast billet requires total extension of the order of 6–7. On the basis of the analysis developed in the present work, it is possible to determine the maximum critical bar cross section such that the required properties are ensured.

Effect of Different Corroding Media on the Corrosion Rate of Locally Produced Thermo Mechanically Treated (TMT) High Strength Structural Steel Bar

The corrosion behavior/rate of TMT steel bars in different corroding media such as rain water, storage atmosphere and concrete ponded in 10% sodium chloride solution has been investigated for a corrosion duration of 40 weeks. The corrosion rate of TMT steel bars corroded in the three media was measured at an interval of 4 weeks. Both macroscopy and microscopy were carried out to reveal different zones such as hardened case, soft core and transition zone in the cross-section and microstructure in these zones respectively of the TMT steel bars in the as received condition and after corrosion of 40 weeks duration. It was found that the corrosion rate of the TMT steel bars in rain water decreases gradually with corrosion duration and reaches a minimum value at 24 weeks of duration after which the corrosion rate increases. The corrosion rate of TMT steel bars in storage atmosphere initially increases and after reaching a maximum value at 16 weeks duration it starts decreasing. The corrosion rate of the TMT steel bars in concrete with 10% NaCl solution decreases very slowly and after reaching minimum value at 32 weeks of duration it starts increasing gradually. It was also found that the corrosion rate of the TMT steel bar in rain water is much higher than that of the TMT bar in storage atmosphere and the corrosion rate of the steel bars in concrete with NaCl solution is the lowest of all the media.

강재 품질에 따른 격자지보재의 성능평가

ABSTRACT: This paper dealt with contents on the performance evaluation of standardized steel and non-standardized steel of lattice girder. Lattice girder is arch type tunnel supports made of structural steel bar and it is girder used to ensure the stability of tunnel by suppressing any transformation of ground as much as possible during tunnel excavation. The performance evaluation of lattice girder can be conducted through bending strength test, tensile strength test and tunnel standard specification specifies that welding structural steel with over 500MPa yield strength shall be used. However, it is difficult to distinguish visually between standardized steel and non-standardized steel onsite if low-quality structural steel is used. Accordingly, this paper conducted performance evaluation of standardized steel and non-standardized steel of lattice girder to point out the issue of deteriorated yield strength of non-standardized steel, while proposed a method of verifying yield strength onsite. Keywords: Lattice girder, Non-standardized lattice girder, Yield strength, Performance evaluation

Geometric conditions in bar rolling

Analysis of the scope for more efficient bar rolling is considered; a method of rapid analysis is outlined. By this means, the geometric parameters of the rolling pathways may be represented by alternative groups of repeatedly transformed dimensionless factors, and the results of repeated transformation may be statistically analyzed, to obtain an assessment of competitiveness. The multivariant representation of the geometric conditions yields significantly more information, including unexpected technological reserves of the process. Such analysis provides a set of recommendations regarding the local correction of the deformation region in one or more passes of the steel through the mill. As an example, this approach is employed in assessing the potential for increasing the product yield in rolling structural-steel bar for cold extrusion and upsetting on small-bar and wire mills at OAO EVRAZ ZSMK. The proposed method may be used to improve the production of a wide range of steel bar.

Failure analysis of a hardened and tempered structural steel (42CrMo4) bar for automotive applications

A round ∅ 78 mm structural steel bar of 42CrMo4 grade with an internal crack was brought with the request to pursue a failure analysis investigation. The crack was detected after ultrasonic inspection at the end-user plant. Visual inspection, optical and scanning electron microscopy were used as the principal analytical techniques in the present study. Further to fractographic interpretation (dendritic morphology found in failure area) and the inclusions detected in the interior of the crack surfaces, it can be concluded that the major crack in the steel bar was probably originated from casting. Plastic deformation processes during rolling resulted probably in the rotation of the crack while overload after subsequent heat treatment (quenching and tempering) may have caused secondary cleavage morphology cracks.

보강 섬유 종류에 따른 고인성 시멘트 복합체내에서 철근의 겹침 이음 성능

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험3. 철근의 겹침이음 실험 결과4. 결론참고문헌요약