Steel Structures Research Articles

Heterogeneous nucleation mechanism of CaS and TiN on spinel combining DFT calculations and experiments

The characteristics of composite inclusions between atomic interfaces has been investigated by combining high-angle annular dark field (HAADF) with first-principles computations. The characteristics of the composite inclusions reveal a core of Ca2Al2O5, with CaS and TiN adhering to its surface. According to mismatch degree theory and SEM characterization, the nucleation rate increases with a decreasing degree of mismatch. Notably, the adhesion work of the Ca2Al2O5/CaS interface is greater than that of the Ca2Al2O5/TiN interface, demonstrating the stronger bond strength of the Ca2Al2O5/CaS interface. The prediction of the lowest interfacial energy shows that a stable interface can form between Ca2Al2O5 and MX. Hence, Ca2Al2O5 can be effectively utilized as a nucleation side for CaS (TiN). The present work provides valuable theoretical and technical information for knowledge-based design and prediction of composite inclusion regulation for structural steels, especially for marine engineering steels.

High-Temperature Tensile Behavior of Structural Steel Grades with Varying Manganese Contents

Abstract Three low-carbon (∼0.1 wt.% carbon) grades of structural steel with varying manganese content (0.75–1.5 wt.%) with ferrite-pearlite microstructure were used for the study. The 1.5 % manganese steel is a microalloyed steel with vanadium, niobium, and titanium content, which is strengthened by interphase precipitates. The steels were tensile tested at room temperature and in the temperature range between 200°C–700°C, at 100°C intervals. The elevated temperature flow strengths of the steels studied show higher strength values for the higher manganese steel. It was found that the manganese enhanced the strength at all ranges of test temperatures. The retention factor of the conventional structural steels was less than or equal to 0.50 against 0.66 for a fire-resistant steel grade. The study shows that the addition of elements such as chromium, molybdenum is required to achieve a higher retention factor to fulfill the requirement of fire resistance characteristics.

Mechanical properties and tensile failure mechanisms of SM400A steel treated by high-power continuous-wave laser

This study systematically investigates the effects of high-power continuous wave laser (CWL) treatment on the mechanical behavior and failure mechanisms of SM400A steel, comparing these outcomes with those of untreated specimens. The findings reveal that while CWL treatment enhances surface hardness, it has minimal impact on the strength of thick structural steel components. However, excessive laser energy density leads to surface defects and softening of the microstructure, adversely affecting the material's toughness. This results in a reduction in elongation at fracture, transitioning the failure mode from ductile to brittle. The study concludes that to ensure the safe use of laser-treated structures, the laser energy density should be carefully controlled not to exceed 3000 J/cm2.

Investigation of Co-Cr alloy layer prepared by laser metal deposition

Abstract Additive technologies are commonly used for component production and repair. Laser metal deposition is a type of additive technology that can create new bodies or add new components to existing parts. This technology enables continuous modification of the chemical and material properties of the deposited layer to suit the intended purpose. The alloying powder is dissolved and mixed in a small volume molten pool during laser deposition. The laser cladding process is known for its rapid heating and cooling rates. This can result in partial or non-existent dissolution of powder particles in the molten pool, or the formation of non-equilibrium microstructures that cannot be achieved through conventional metallurgical processes. As a result, this method can be used to create materials with unique combinations of properties. In this study, a Co-Cr coating layer was applied to a structural steel base plate. The parameters combination was generated using Taguchi’s experimental design. The relationship between the parameters and the properties of the prepared coating was evaluated using the Taguchi method.

Low-Carbon Steel Formed by DRECE Method with Hot-Dip Zinc Galvanizing and Potentiodynamic Polarization Tests to Study Its Corrosion Behavior

The use of low-carbon unalloyed steel with minimal silicon content is widespread in structural steel and automotive applications due to its ease of manipulation. The mechanical properties of this steel can be significantly enhanced through severe plastic deformation (SPD) techniques. Our study focuses on the practical benefits of the dual rolling equal channel extrusion (DRECE) method, which strengthens the steel and has implications for material hardness and the thickness of subsequently applied hot-dip zinc galvanizing. Furthermore, the steel’s corrosion potential and current are investigated as a function of material hardness and thickness. The findings show a 20% increase in hardness HV 30 after the first run through the forming machine, with an additional 10% increase after the second run. Subsequent galvanizing leads to a further 1–12% increase in HV 30 value. Notably, the DRECE hardening demonstrates no statistically significant effect on the corrosion potential and current; however, the impact of galvanizing is as anticipated.

Axial compressive behavior of steel-hollow core partially encased composite spliced columns

Steel-hollow core partially encased composite spliced frame beam (SHSFB) amalgamates the advantages of steel and composite structures, offering excellent deformation capacity, seismic performance, material savings, and reduced weight. These advantages are also essential for frame columns. Therefore, axial compression tests were conducted on four steel-hollow core partially encased composite spliced columns (SHSCs) and one steel comparison specimen to investigate their failure modes and compressive performance. The test results revealed that the SHSC does not fully utilize the compressive performance of the composite part under compression. Based on these experimental results, improvements were made to the configuration of SHSC, and a new type of SHSC (NSHSC) was further introduced. Finite element parameter analysis was conducted on the hollow-core partially encased composite (HPEC) short columns and NSHSCs, respectively, to investigate the confined effect on concrete in the HPEC section and the influence of different parameters on the compressive performance of NSHSC. The simulated results show that the effectively confined area of concrete in the HPEC section increases with thicker H-shaped steel flanges and narrower stirrup spacing. The compressive performance and failure modes of NSHSC are determined by the lower strength of either the steel part or the composite part. Finally, by integrating concrete confined area division and the compressive stability of variable stiffness column, the calculation method for the axial compressive bearing capacity of NSHSC was proposed. The calculated values exhibit good agreement with the simulation results.

Low-cycle fatigue of welded joint from steel of X70 strength class

Steels of X70 strength class are particularly widely used in the field of heavy engineering. One of the most important issues when choosing steel for structures is its behavior under cyclic loads. It is difficult to find a description of the behavior of all zones of the welded joint under fatigue. The purpose of this study was to determine the fatigue characteristics of welded joints made of the Russian analogue of S690QL steel with fixation of acoustic and magnetic parameters for their use in the diagnosis. The objects of the study were the samples from domestic steel of X70 strength class. The chemical composition was determined using optical emission spectrometry. The grinds for microstructural analysis were prepared according to the standard technique with etching in the metal. The fatigue test was carried out on a specialized test bench. The authors used the acoustic system AIS NRK-3 for acoustic measurements and the acoustic parameter D – as an informative parameter. A MA-412MM coercitimeter was applied to evalua­te the magnetic characteristics. The following were evaluated: residual magnetization Br , coercive force Hc , Hc/Br ratio. The smallest number of cycles corresponds to the deposited metal zone. The decrease in amplitude showed a significant variation in the behavior of the material depending on the junction zone. However, the curves for heat affected zone (HAZ) and the deposited metal are practically the same. HAZ differs to a lesser extent from the base metal than the deposited metal zone. The graph of the acoustic parameter in its form is the reverse of the magnetic characteristics graph. Thus, there is a minimum for the acoustic parameter, depending on the operating time, and a maximum for the magnetic characteristics. For both graphs, the extremum is the point corresponding to the operating time of 0.6.

An Evaluation of Backfill Material Applicability through Deformation Measurements of Long-Span Buried Corrugated Steel Structures

Corrugated steel plates are increasingly being applied to various types of structures, such as eco-corridors, noise reduction tunnels, and urban elevated roads. However, applications for spans exceeding 25 m are lacking, as they require clear standards for calculating the elastic moduli of backfill materials and reinforced sections. This study evaluated the appropriateness of mechanical assumptions applied in the design, by measuring displacements at each stage and comparing the finite element analysis results for a concrete-reinforced corrugated steel plate arch underground structure with a width of 27.5 m and length of 467 m. Based on the measurement results, deformations ranging from 19.8% to 63.7% of allowable deflection were observed when applying an elastic modulus of 60 MPa to solidified soil backfill, which is twice the maximum standard value applied to general soil, thereby confirming the suitability for the serviceability of underground structures.

Bond-slip models on interfacial behavior between Fe-SMA and steel in hygrothermal environments

Strengthening the existing steel structures to enhance performance can prolong their service life and reduce carbon emissions. Previous studies have employed iron-based shape memory alloy (Fe-SMA) to adhesively and actively retrofit long-span steel bridges in practice, achieving satisfactory repair efficiency. Nonetheless, concerns persist regarding the long-term performance of Fe-SMA-bonded parent structures, principally stemming from the performance degradation of the adhesives in hygrothermal environments. In this study, the damage evolution and debonding mechanisms of Fe-SMA/steel single-lap joints (SLJs) in hygrothermal environments are investigated through 54 lap-shear tests. The evolutionary process of Fe-SMA strain and shear stress within the overlapping zone is assessed, varying with aging time and adhesive type under shear load. Furthermore, the bond-slip models of the Fe-SMA/steel SLJs are put forward, which change with the aforementioned influencing factors in hygrothermal environments. The lap-shear tests demonstrate that the ultimate shear stress of SLJs is transmitted approximately up to 50 mm away from the initial end, with shear stress developing swiftly towards the free end during this phase. In hygrothermal environments, the effective overlapping length of the SLJs is highly contingent on the material properties of adhesives, improving with the prolonged aging time. This study proposes bond-slip models that describe the interfacial performance between Fe-SMA and steel, accounting for the detrimental influence of temperature, humidity, plastic deformation of components and strain relaxation. The experimental outcomes can guide the analysis of the debonding characteristics of Fe-SMA-bonded structures, and the theoretical study can provide reliable predictions for the service performance of reinforcement systems in hygrothermal environments.

Effects of Electrochemical Hydrogen Charging Parameters on the Mechanical Behaviors of High-Strength Steel.

Extended exposure to seawater results in the erosion of the structural high-strength steels utilized in marine equipment, primarily due to the infiltration of hydrogen. Consequently, this erosion leads to a decrease in the mechanical properties of the material. In this investigation, the mechanical responses of Q690 structural high-strength steel specimens were investigated by considering various hydrogen charging parameters, such as the current density, charging duration, and solution concentration values. The findings highlighted the significant impacts of electrochemical hydrogen charging parameters on the mechanical behaviors of Q690 steel samples. Specifically, a linear relationship was observed between the mechanical properties and the hydrogen charging current densities, while the associations with the charging duration and solution concentration were nonlinear. Additionally, the fracture morphology under various hydrogen charging parameters was analyzed and discussed. The results demonstrate that the mechanical properties of the material degrade with increasing hydrogen charging parameters, with tensile strength and yield stress decreasing by approximately 2-4%, and elongation after fracture reducing by about 20%. The findings also reveal that macroscopic fractures exhibit significant necking in uncharged conditions. As hydrogen charging parameters increase, macroscopic necking gradually diminishes, the number of microscopic dimples decreases, and the material ultimately transitions to a fully brittle fracture.

Experimental study on low-cycle fatigue performance of high-strength bolted shear connections

In strong earthquakes, low-cycle fatigue fractures may occur in the bolted connections of steel braced frames. Ensuring a high low-cycle fatigue life for high-strength bolted connections is of paramount significance in enhancing the overall safety and collapse resistance of steel structures. Despite substantial research on plate fatigue failure within bolted connections, there remains a research gap regarding low-cycle fatigue failure of high-strength bolts in these connections. This study aims to address the aforementioned shortcomings by conducting 34 sets of low-cycle fatigue tests on high-strength bolted connections. The test specimens all experienced low-cycle shear fatigue fracture at the threaded or unthreaded portion of the bolt shank as the dominant failure mode. Residual deformations were observed in the holes of connection plates. Based on the test data, ultimate shear capacity of a single shear connection is around 0.61Fy (tensile yield bearing capacity of bolt) when the shear force passes through the unthreaded portion and drops to 0.54Fy for the shear force at the thread. The untreated Q355 (minimum yield strength of 355 MPa) steel surface has an average anti-slip coefficient of around 0.37, while milling reduces it to approximately 0.30. The influence patterns of loading amplitude, bolt material, minimum plate thickness, bolt diameter, shear force position and connection type on low-cycle fatigue life are given by range analysis. Among them, variance analysis shows that loading amplitude and bolt material are the primary influencing factors. The correlation coefficient between loading amplitude and low-cycle fatigue life is −0.92, indicating a strong negative correlation. The degradation amount and rate of anti-slip capacity and shear capacity of bolted connections are also investigated. To propose reliable life prediction method, three models were used to establish the relationship between dimensionless shear deformation and low-cycle fatigue life of 10.9-grade high-strength bolted connections. It is not appropriate to use the fatigue categories defined in current standards to predict the low-cycle shear fatigue life of high-strength bolted connections.

Automatic PAUT crack detection and depth identification framework based on inspection robot and deep learning method

Orthotropic steel bridge decks (OSD) are widely acclaimed for their lightweight, high load-carrying capacity, and adaptability, making them a popular choice in steel structure bridges. However, the complex nature of their structure makes them susceptible to fatigue cracking, posing significant safety concerns. To address the issues above, this study employs a robot equipped with an ultrasonic phased array probe to automate the detection of internal cracks within Orthotropic Steel Decks (OSD). A Deep Convolutional Generative Adversarial Network (DCGAN) is utilized to augment the training dataset of Phased Array Ultrasonic Testing (PAUT) images. The YOLO series algorithms are applied and compared for crack localization, with YOLO v7-tiny exhibiting the highest accuracy and speed. Integrating attention mechanisms into the YOLO v7-tiny algorithm to facilliate rapid and high-precision crack detection. Analyzing the echo region with an echo intensity bar enabled the identification of crack depth, with an identification error within 5%.

Assessment of the Film-Free Water Decal Method for Speckle Pattern Application in Digital Image Correlation.

Digital Image Correlation (DIC) often encounters challenges with variability and consistency in traditional speckle pattern application techniques, such as spray-painting, affecting measurement accuracy and reliability. This study evaluates a film-free water decal method as an alternative for applying speckle patterns in DIC. SS275 structural steel specimens were prepared with speckle patterns using both the film-free water decal method and traditional spray-painting. The quality of the speckle patterns was assessed, and their effectiveness for DIC was evaluated through tensile testing and a comparison with strain gauge measurements. The film-free water decal method provided enhanced control over speckle pattern application, resulting in high-quality, consistent patterns. Strain measurements obtained using this method closely matched those from traditional methods, confirming its reliability. The film-free water decal method offers a practical and reliable alternative to spray-painting, improving the consistency and accuracy of DIC experiments, with potential applications in various engineering and scientific fields.

Strain amplitude dependency of cyclic hardening/softening behavior of 490 N/mm2 class steel

Existing studies on the strain amplitude dependency of cyclic softening behavior in structural steels often involve limited cycles or strain amplitudes below 2.5%, failing to provide a comprehensive understanding of stabilized cyclic behavior. This study performed uniaxial tension–compression cyclic loading tests using SN490B structural steel under three loading patterns: constant, variable, and offset constant strain amplitudes. The cyclic hardening and softening behaviors and stress–strain hysteresis loops were compared. Under variable strain amplitude loading, the specimens were subjected to increasing and decreasing strain amplitudes to investigate the strain amplitude dependency of the cyclic hardening and softening behaviors. Under offset constant strain amplitude loading, mean strains were initially introduced in either the tension or compression strain range, followed by cyclic loading with a constant strain amplitude centered around the mean strains. The test results revealed the following: (1) Under constant strain amplitude cyclic loading, the material exhibited cyclic softening and hardening behaviors at strain amplitudes smaller than and larger than 0.5%, respectively; (2) Under variable strain amplitude cyclic loading, increased and reduced strain amplitudes resulted in cyclic hardening and softening behaviors, respectively. The cyclic hardening/softening behavior strongly depended on the strain amplitude. Applying a significant number of cycles after strain amplitude reduction resulted in the stress–strain curves closely resembling those under constant strain amplitude conditions; (3) Even under offset constant strain amplitude cyclic loading conditions with nonzero mean strain, the peak stresses and shapes of the hysteresis loops approached those under constant strain amplitude conditions without mean strain.

Flexural behaviour of Q1100 ultra high strength steel welded I-sections

An experimental and numerical program investigating the in-plane flexural behaviour of Q1100 ultra high strength steel (UHSS) welded I-sections is presented in the current paper. The testing program comprised of material coupon tests, measurements of residual stresses, and in-plane 3-point bending tests. Subsequently, a numerical program was executed, involving the development of finite element (FE) models. The FE models validated against the experiments were subsequently employed for parametric studies, aiming at assessing the flexural behaviour of Q1100 welded I-sections across a broader spectrum of section geometries. The data obtained from the experiments and numerical simulations were used to assess the applicability of prevailing design provisions outlined in the European, Chinese and Australian codes for high-strength steel structures. These design provisions encompass classification limits for cross-sections and predicted methods for cross-sectional resistance in bending. Via reliability analyses, adjustments were made to the cross-section classification limits. Finally, a modified direct strength method was proposed to predict the in-plane bending resistance for Q1100 welded I-sections.

New triglycidyl ether triazine as a protective agent for metal: Comprehensive analysis

This study presents the synthesis and characterization of triglycidyl ether triazine (TGET), a novel epoxy resin, designed as a defensive agent for mild steel (C38) in a 1 M HCl environment. The corrosion inhibitory effectiveness of TGET was evaluated by various electrochemical methods and corroborated by surface analysis using surface and theoretical methods. The key findings demonstrate that the protection behavior of TGET rises with its concentration, achieving a maximum of 94.77 % at 10−3 mol/L, indicating a highly effective reduction in iron dissolution. Surface analysis confirmed the establishment of a defensive cover on the metal surface. The theoretical studies supported the experimental data, suggesting a strong adsorption of TGET molecules on the steel surface through chemical interaction, primarily via electron donation from the N and O atoms of the TGET to the metal surface. These results establish TGET as a highly effective corrosion inhibitor with potential applications in protecting steel structures in industrial environments characterized by acidic conditions.

Structural damage detection and localization via an unsupervised anomaly detection method

This study introduces an unsupervised machine learning framework for damage detection and localization in Structural Health Monitoring (SHM), leveraging dynamic graph convolutional neural networks and Transformer networks. This approach is specifically tailored to overcome the challenge of limited labeled data in SHM, enabling precise analysis and feature synthesis from sensor-derived time series data for accurate damage identification. Incorporating a novel ‘localization score’ enhances the framework’s precision in pinpointing structural damages by integrating data-driven insights with a physics-informed understanding of structural dynamics. Extensive validations on diverse structures, including a benchmark steel structure and a real-world cable-stayed bridge, underscore the framework’s effectiveness in anomaly detection and damage localization, showcasing its potential to safeguard critical infrastructure through advanced data-effective machine learning techniques.

Sustainable and cost-effective optimal design of steel structures by minimizing cutting trim losses

Since the beginning of the structural optimization field, the optimal design was characterized by the least-weight configuration. In this sense, all the researchers agreed on adopting the minimum-weight optimization statement as the most promising approach to achieve an optimized employment of material. However, especially for steel structures, this approach completely fails the primary goal of encouraging standardization of pieces during the production phase. Except for rare cases, increasing diversity among structural elements leads to a dramatic increase in the financial cost as well as the environmental impact of the structure because of the material waste generated during the cutting procedure.In this paper, a real-coded Genetic Algorithm has been adopted and the well-known one-dimensional Bin Packing Problem has been implemented within the structural optimization process. The Objective Function formulation lies in a marked change of the paradigm in which the target function is represented by the amount of steel required by the factory instead of the structural cost (e.g. weight). The proposed approach is tested on different steel structures moving from 2D truss beams to 3D domes. Addressing the optimal stock of existing elements leads to a significant waste reduction of 40% in almost all the investigated case studies.

Analysis of Knuckle Joint for Structural Steel, Aluminium Alloy, And Titanium Alloy

Abstract—The goal of this research is to investigate and determine the stresses in a knuckle joint using steady state analysis, with the objective of identifying the optimal material for the project. Three different materials, namely structural steel, aluminium alloy, and titanium alloy are analyzed for the knuckle joint. The study focuses on a knuckle joint designed for an applied force of 25 KN. Finite Element Analysis (FEA) results for tensile loading are compared and validated with total deformation. The findings indicate that the knuckle joint made of titanium alloy exhibits the lowest stresses, while the knuckle joint made of structural steel is capable of sustaining the highest tensile load without failure. Keywords- Knuckle Joint, FEM, stress analysis, Titanium alloy, aluminium alloy, structural steel.

The influence of heat treatment modes on structure and corrosion properties of 14Kh17N2 steel

The influence of heat treatment modes on structure and corrosion properties of 14Kh17N2 steel