Steel Structures Research Articles

Electrochemical interaction behaviors between adjacent zinc-rich coating defects on steel structures under immersion and wet–dry environments

This study investigates the corrosion mechanism of carbon steel beneath zinc-rich coating (ZRC) defects to understand the mutual interference of carbon steel in atmospheric environments. First, electrochemical impedance spectroscopy (EIS) was conducted to determine the self-corrosion behavior of carbon steel under ZRC defects. Subsequently, a macrocell current tests were conducted under immersion and wet–dry environments to evaluate the electrochemical interaction effects at the location of coating defects. The results indicate that the electrochemical interactions between the ZRC defects are influenced by the sacrificial anode effect of Zn. Further, the interaction mechanisms between the steel substrates beneath the organic and inorganic ZRC defects were analyzed. The findings provide deeper insight into the behavior of steel structures in atmospheric environments, offering potential improvements in the design of protective coatings for infrastructure longevity.

Exceptional tensile ductility and strength of a BCC structure CLAM steel with lamellar grains at 77 kelvin

The low-temperature tensile brittleness of body-centered cubic (BCC) metals and alloys can seriously compromise their service applications. In this study, we prepared a BCC structured China low activation martensitic steel (CLAM) steel with lamellar grains by regulating the rolling and heat-treatment processes, successfully reversing the decreasing trend of ductility in the steel with decrease in temperature. Compared with current face-centered cubic (FCC) structural steels and high-entropy alloys, the lamellar grained CLAM steel exhibits an excellent synergy of strength and ductility at 77K, but with lower raw material costs. The superior low temperature ductility of the lamellar grained steel can be attributed to an increase in grain strength at low temperatures which promotes the propagation of layered tearing cracks; this in turn leads to a significant increase in the necking area of the steel, thereby compensating for the decrease in ductility. We conclude that our lamellar grain structures can be utilized to significantly enhance the low-temperature tensile ductility of BCC metals and alloys, thereby expanding their service range to cryogenic temperatures.

Structural Behavior of Steel Structure Retrofitted with Bracing Systems and Nonlinear Viscous Dampers

Introduction: A steel frame system becomes structurally less efficient when subjected to large lateral loads such as a strong wind or a severe earthquake. Several techniques could enhance the structural performance against these lateral loads, including single diagonal and X-bracing systems, moment-resisting frames, and viscous dampers. Methods: This study aimed to compare these techniques' ability to reduce the structure's dynamic and static behavior when it faces lateral loads. The structure dynamic behavior was discussed through its lateral displacement response computed from the nonlinear dynamic analyses using different seismic and harmonic excitations. The structure static behavior was investigated based on the demand capacity curves and the plastic hinges response computed from the nonlinear static analyses (Pushover) following FEMA P-1050-1 guidelines. In this paper, the viscous dampers were assumed to have a nonlinear behavior (0<α<1) and the impact of the velocity exponent α on their performance against the dynamic excitations was evaluated. Results: The results show that the X-braced frame performs better in reducing the structure displacement response and plastic hinges performance levels formed in the structural members than a single diagonal braced frame, followed by a momentresisting frame. The results also indicate that the X-braced frame has a larger base shear resistance capacity and a smaller deformation capacity than other structural configurations. Conclusion: It was also concluded that, for the same damping coefficient, the performance of nonlinear viscous dampers increased as the velocity exponent decreased.

Does seismic isolation reduce the seismic vulnerability and the variability of the inelastic seismic response? Large-scale experimental investigation

AbstractThis paper focuses on the large-scale experimental investigation of the seismic vulnerability and the variability of the inelastic seismic response of seismically isolated structures in comparison to conventional, fixed-based structures. The experimental setup comprises a steel structure consisting of two steel columns and a steel mass on top. The structure is seismically isolated using four friction pendulum bearings and subjected to an ensemble of strong recorded earthquake ground motion excitations using the shaking table of ETH laboratory. A mechanical clevis connection consisting of two hinges and two replaceable steel coupons is designed and constructed to facilitate the investigation of the seismic inelastic behavior of the structure for the selected ground motion record ensemble through the replacement of the damaged coupons after each shaking table excitation. Within this frame, the mechanical clevis connection presented in this study facilitates the parametric and experimental investigation of the seismic, inelastic behaviour of a wide range of structures and the experimental determination of their seismic fragility curves. The seismic vulnerability and the variability of the seismic response of the seismically isolated and the corresponding fixed-based structure are compared for three seismic hazard levels. The comparison of the response of the two structures demonstrates experimentally the ability of seismic isolation to reduce the seismic vulnerability and the variability of the seismic response of structures subjected to strong earthquake ground motion excitation, thus leading to the design of structures of higher performance, predictability and reliability in their response, even for extreme earthquake events.

Microstructure Evolution of Super304H Steel Used in a Service Power Station Boiler

The microstructure and structure of a Super304H superheater steel pipe after 47,000 h were analyzed by metallographic microscope, scanning electron microscope (SEM), and EDS, and its mechanical properties were measured by hardness meter. The results show that the austenitic grains appear on the outer wall of Super304H steel pipe after service, while the SEM and metallographic microscope tests show that the outer wall particles are coarse. There is an obvious corrosion layer on the outer surface, and the thickness of the corrosion layer on the windward surface is significantly higher than that on the leeward surface. The inner surface is refined and the hardness of the material is significantly increased; the outer surface, the inner surface, and the center all grow abnormally. In this case, the room temperature tensile strength and impact performance of the rough crystal area of the outer wall of the Super304H steel pipe are reduced and fracture along the crystal. Supervision should be strengthened to eliminate the safety risks caused by the abnormal growth of the outer wall austenite grain. The results of crystal phase microscopy show that the main structure of the material still maintains the basic structure of austenitic steel, and particle aggregation mainly occurs in the sub-inner layer of the inner and outer surface. Compared with the lee surface, the middle body structure is basically the same, but whether the thickness of the corrosion layer on the inner surface or the outer surface increases, the deformation degree of the deformation layer is greater. The hardness measurement finds that the hardness of the corrosion layer is caused by the increase in Super304H steel surface stress. In case of pipe explosion accident, the highest chance of pipe explosion here should be closely observed.

Multi-frequency eddy current control of structural steel sheets

The results of the study of the effect on the results of eddy current testing of the thickness of structural steel sheets of such a parameter as the force of pressing the eddy current sensor to the surface of the object of control are presented. To isolate the controlled parameter, experimental values of the introduced resistances of an eddy current converter obtained using multi-frequency measurements were used. The dependences of these resistances for the overhead eddy current transducer sensor on the clamping force and thickness of the steel sheet are revealed. A method for processing the results of eddy current measurements is proposed, which ensures the elimination of interfering parameters and reliable isolation of the controlled parameter.

Allowable stress rating compared to load and resistance factor rating for timber bridges with and without steel-beam retrofit

This paper presents the relevancy of the Allowable Stress Rating (ASR) and the Load and Resistance Factor Rating (LRFR) methods for timber bridges. Benchmark bridges constructed in the 1930′s are upgraded with hollow structural steel (HSS) beams and three-dimensional finite element models provide technical information that is necessary for examining their behavior and rating evaluations. Complying with published manuals, a total of 17 rating vehicles are considered across three categories (Design, Legal, and Permit) so as to generate the maximum responses of the bridges. The position of the vehicles dominates the deflection profiles of the unrepaired bridges. After installing the HSS beams, the live loads are redistributed and stiffness enhancement is noticed in the transverse direction of the bridges. The rating factors calculated with ASR exceed those with LRFR for the unrepaired bridges, regardless of vehicle configurations, and the level of disparity between these rating approaches increases when the bridges are repaired owing to differences in load factors. In terms of sensitivity to average daily truck traffic, the LRFR factors of the bridges under the Legal vehicles are more responsive than the factors subjected to other vehicle types. From a probability perspective, the compatibility of these rating methodologies varies contingent upon vehicle categories and the presence of the HSS beams. Practice guidelines are proposed to facilitate the conversion of rating factors between ASR and LRFR as a function of the present condition of constructed timber bridges.

Investigation of the Seismic Performance of a Multi-Story, Multi-Bay Special Truss Moment Steel Frame with X-Diagonal Shape Memory Alloy Bars

In this work, the seismic response of a multi-story, multi-bay special truss moment frame (STMF) with Ni-Ti shape memory alloys (SMAs) incorporated in the form of X-diagonal braces in the special segment is investigated. The diameter of the SMAs per diagonal in each floor was initially determined, considering the expected ultimate strength of the special segment, developed when the frame reaches its target drift and the desirable collapse mechanism, i.e., the formation of plastic hinges, according to the performance-based plastic design procedure. To further investigate the response of the structure with the SMAs incorporated, half the calculated SMA diameters were introduced. Continuing, three more cases were investigated: the mean value of the SMA diameter was introduced at each floor (case DC1), half the SMA diameter of case DC1 (case DC2), and twice the SMA diameter of case DC1 (case CD3). Dynamic time history analyses under seven benchmark earthquakes were conducted using commercial nonlinear Finite Element software (SeismoStruct 2024). Results were presented in the form of top-displacement time histories, the SMAs force–displacement curves, and maximum inter-story drifts, calculating also maximum SMA displacements. The analysis outcomes highlight the potential of the SMAs to be considered as a novel material in the seismic retrofit of steel structures. Both design approaches presented exhibit a certain amount of effectiveness, depending on the distribution, with the placement of the SMA bars and the seismic excitation considered. Further research is suggested to fully understand the capabilities of the use of SMAs as dissipation devices in steel structures.

A Magnetic Climbing Robot for Steel Bridge Inspection

Abstract. The maintenance of traditional steel bridges presents many significant challenges due to the fact that bridges of different ages and standards vary in design, structural complexity and technical difficulty. In light of these considerations, it is clear that maintenance personnel must possess a wealth of professional expertise and experience in order to effectively address the diverse and intricate maintenance challenges that arise. Moreover, the maintenance process entails high-risk operations such as high-altitude work and welding, which pose a threat to the safety of construction personnel. Therefore, this study introduces a magnetic adsorption robot designed to address the low efficiency and high costs of traditional maintenance methods. This robot features a dual robotic arm mechanism and modeled using the Denavit Hartenberg (D-H) parameter method. Electromagnetic adsorption is utilized to achieve wall adhesion, and direct power supply is provided through DC power to control weight. The robot can perform flexible remote control operations through the HC-05 Bluetooth module. The experimental results show that the robot exhibits robust adhesion and obstacle crossing ability on steel surfaces, thereby enabling unimpeded movement within the steel structure. In addition, the robot is now capable of performing overhaul procedures via remote control.

Influence of the longitudinal welded joint microstructure of X52 and X70 large diameter pipes on resistance to hydrogen embrittlement

The article covers influence of a set of gradient microstructures of large diameter pipes (LDP) on resistance to hydrogen embrittlement. The object of the study were specimens of longitudinal welded joints of X52 and X70 LDP before and after slow strain rate tensile tests (SSRT) in gaseous nitrogen and hydrogen. It was found that fracture of X52 specimens during SSRT occurred with multiple crack initiation centres at the interfaces of the pearlite–ferrite structural constituents, while fracture of X70 specimens resulted in a single crack propagation. Steels Х52 and Х70 fractured not in the heat-affected zone (HAZ) recrystallisation area containing islands of martensite-austenite phase, but in the high-temperature tempering zone, which is characterised by anisotropic ferrite-perlite (Х52) and ferrite-bainite (Х70) microstructure. Finely dispersed uniform structure of bainite ferrite despite the content of martensite-austenite component is not a source of hydrogen crack initiation. Although a welded joint of X70 steel is characterised by higher strength, it is less susceptible to the embrittlement effects of gaseous hydrogen than X52, which is probably due to the finer and more uniform structure of X70 steel. Presence of ferrite-pearlite banding in the structure of X52 steel has a more negative effect on resistance to hydrogen embrittlement than increased hardness of the HAZ high-temperature tempering area of X70 steel.

Modified Use of the Component Method to Get More Realistic Force Distribution in Joints of Steel Structures

According to the EN 1993-1-8 Standard, the moment resistance of end-plated connections can be calculated with the use of the component method. In this, a pair-of-force defines the moment resistance. The magnitude and the location of the compression force can be accurately identified. The tension force part is usually the resultant of parallel forces appearing in line with the bolt rows. Following the rules of manual calculation and using a mechanical finite element model, where each component is modelled with spring elements, in some—easily identifiable—cases, leads to different force distribution. The simplifications defined in the Standard provide a longer arm for the same force, and because of this, larger moment resistance at the expense of safety. In this work, an alternative calculation method will be presented that provides the same force values in each bolt row, as the mechanical model of the connection, without constructing the finite element model.

Study of the fire resistance of partially encased composite steel-concrete columns according to Eurocode 4

In this paper, the behavior of partially encased steel and concrete composite columns without fire protection exposed on four sides to the standard fire and under axial loading was studied using the simplified calculation model of the Eurocode4 (EC4) method. The main objectives of this study are: first to evaluate the temperature of the different components of the column section as well as the variation in the characteristics of the materials constituting them (strengths and Modulus of elasticity); and then analyze the influence of several parameters, such as the section size, the reinforcement rate, the buckling length and the mechanical strengths of the steel and concrete on the ultimate fire resistance. The results show that the dimensions of the section, the reinforcement rate and the buckling length have a significant influence on the fire resistance. On the other hand, the concrete strength, the structural steel grade and the reinforcing steel grade have a moderate influence.

Revealing failure loads of cyclically loaded H-steel columns from a thermodynamic perspective

Steel failure is always defined by phenomena such as yielding and buckling. A steel structure may fail under complex conditions such as cyclic or biaxial loading, but determining its critical loads is complex. Ref. [Case Stud Constr Mat., 2023; 18] used the dataset of Ref [Eng Struct., 2018; 174 826-839] (A set of cyclic loading tests of H-steel columns with material Q345B and length 1500 mm) attempts to reveal the systematic failure law of H-steel columns during cyclic loading from residual strains based on draft stage stressing state theory, but ignoring the relativity among the elements. With our lab's growing understanding of structural failure laws' systematic and evolutionary nature, ignoring the vital connection between the stressing state theory and thermodynamics is problematic. This work uses the dataset of Ref. [Eng Struct., 2018; 174 826-839] and try to reveal the failure laws of H-steel columns from a thermodynamic perspective based on the stressing state theory and new characterization methods. We first transform amplitude strain data under cyclic loading into state variables and divides them into six parts. The network-free renormalization method can be used to characterize the stressing state evolution of H-steel columns. Further, the phase transition loads can be detected by applying clustering analysis criteria because of their attractor effect. On the other hand, Wilson's phase transition theory defines phase transition loads as the fixed points of renormalization, which can be verified by comparing the before and after renormalization (part and overall) results. Lastly, the economy index (EI) is defined as the ratio of the biaxial moment triangle area S2 to the steel column volume at the elastoplastic branch (EPB) point to verify the safety and economy of the EPB-based seismic performance design for H-steel columns. EPB-based designs increase the EI of Class IV and III H-steel columns by 258.8 % and 365.8 %, respectively. Thus, this work provides a new reference for thermodynamic-based failure and seismic performance analysis of H-steel columns.

Intelligent design of steel–concrete composite beams based on deep reinforcement learning

In this work, an automated member design method is proposed based on deep reinforcement learning (DRL). Using steel–concrete composite beam design as a case study, the design procedure is conceptualized as a sequential optimization process and modeled as a Markov Decision Process (MDP). A design agent equipped with two deep neural networks, is trained using the proximal policy optimization (PPO) method to complete the complex design task of steel–concrete composite beams, adhering to the Chinese standard for design of steel structures GB50017-2017 provisions. The structural provisions are integrated into a simulated design environment, which can respond to the agent’s actions. A universal reward shaping function is introduced to guide the agent towards success and minimize material cost. The design quality and generation performance of trained PPO agent are compared with those of the Differential Evolution (DE) in 100 random training cases, 100 random testing cases, and 95 real-world engineering cases, demonstrating significant promise and reduced time consumption for automated steel–concrete composite beam design. An approach combining PPO with DE is proposed to enhance the robustness and reliability of the original agent. Finally, a brief discussion is conducted on the essence and prospects of the proposed method.

Synthesis, Characterization and Theoretical Calculations of a Novel Organic Corrosion Inhibitor for Mild Steel

Abstract Q235 is a carbon structural steel sheet that is widely employed in the construction and engineering sectors due to its cost-effectiveness and durability. Here, A novel organic corrosion inhibitor for Q235 sheet based on furan-thiadiazole (5-amino-2-furyl-1, 3, 4-thiadiazole, AFTZ) has been designed, successfully synthesized and characterized in this work. Results of experimental data and theoretical calculations indicated that AFTZ has an excellent corrosion inhibition property for Q235 sheet in 1.0 mol/L H2SO4. The highest efficiency of corrosion inhibitor tested by weight loss experiment can reach 91.17% and electrochemical experiment was up to 95.85% when AFTZ increased to 2 mg/mL in H2SO4 solution. The morphological characteristics of Q235 sheets with or without corrosion inhibitor showed that the target inhibitor has good corrosion inhibition performance. Quantum computation using the DFT method of guassian09 software and FT-IR date attribute the excellent corrosion inhibition to the film-forming nature of AFTZ.

Study and Characterisation of Bimetallic Structure (316LSI and S275JR) Made by Hybrid CMT WAAM Process

The main objective of this research is to conduct an experimental investigation of the bimetallic material formed by 316LSI stainless steel and S275JR structural steel, produced via hybrid wire arc additive manufacturing technology with cool metal transfer welding and machining, and with the objective of being able to reduce the industrial cost of certain requirements for one of the materials. A methodological investigation has been carried out starting with welding beads of 316LSI on S275JR plates, followed by overlapping five beads and conducting final experiments with several vertical layers, with or without intermediate face milling. The results achieved optimal bead conditions for wire speeds of 4 m/min and 5 m/min at a travel speed of 400 mm/min. Overlap experiments show that the best deposition results are obtained with an overlap equal to or greater than 28%. Cooling time does not significantly influence the final geometry of the coatings. Regarding metallographic analysis, the filler material presents an austenitic columnar structure. In the base material, a bainitic structure with inferred grain refinement was detected in the heat-affected zone. An increase in hardness is observed in the heat-affected zone. In the results obtained from the tensile tests of the bimetallic material, an increase in mechanical strength and yield strength is observed in the tested specimens.

Research on Digital Construction Technology for Special-Shaped Shell Pipe Structures

The aesthetic appeal of special-shaped shell pipe structures makes them highly favored by architects and holds promising prospects for various applications. In the detailed design stage, NURBS curves should be divided into multiple continuous arcs due to the limitations of current steel structure fabrication equipment, which can only accommodate pipes with equal-curvature bends. However, the traditional manual fitting methods suffer from several issues including low efficiency, undercutting at the interface, poor smoothness of curves, and lack of control over tolerances. Furthermore, the weaker out-of-plane stiffness and utilization of bending arc pipe sections pose significant challenges in terms of spatial positioning and installation accuracy that need to be addressed. The study focuses on addressing these challenges by investigating digital construction technology for special-shaped shell pipe structures and developing a parametric algorithm that enables automatic fitting of spatial NURBS curves into multiple arcs, thereby achieving seamless curve fitting. A post-processing program was developed to enable the parametric generation of fabrication and installation information for structural members, which can be seamlessly integrated into the BIM database. Finally, structural position control technology is proposed to improve assembly efficiency and ensure consistency between the completed construction state and the design shape. The above digital construction technology has been applied in projects such as the Haihua Island International Conference Center. It can provide complete technical solutions for modeling of special-shaped shell pipe structures, including establishment of a member information database, fabrication at the workshop and installation on site, construction organization management, as well as installation accuracy control.

Effect of size on eccentric compression performance of steel tube and sandwiched concrete jacketed CFST columns

This study investigated the size effect of steel tube and sandwiched concrete jacketed CFST columns under eccentric compression. A series of eccentric compression tests were conducted on 3 geometrically similar un-strengthened CFST columns and 13 strengthened CFST columns with varying structural sizes (with a ratio of 1:1.5:2), different eccentricities, and different outer steel ratios. The eccentric performance of the specimens, including their failure behaviours, load-axial displacement curves, and longitudinal and circumferential strain distribution were explored. Additionally, the size effect on nominal stress-longitudinal displacement relationships, nominal axial strength, nominal ultimate deflection and ductility index were investigated. The test results confirmed the presence of a size effect in both un-strengthened and strengthened CFST columns, with nominal strengths closely following Bažant's proposed "size effect law (SEL)". Finally, considering the influence of size effect, this study proposed axial force-bending moment (N-M) correlation curves for predicting the bearing capacity of strengthened CFST stub columns based on EC4, AISC-360, AIJ and GB 50936. Among these codes, AIJ provided the most accurate predictions when compared to the test results. Introducing the size effect coefficients mitigated the tendency to overestimate the load-bearing capacity of large-size retrofitted columns.

A novel method: YOLO-CE and 3D point cloud-based feature extraction for welding seams of tower bases

Abstract Robotic automated welding of non-standard steel structures presents significant challenges, particularly for electric power tower bases. This study introduces a novel approach that integrates the You Only Look Once—Compact Invert Block and Efficient Local Attention (YOLO-CE) model, an enhanced version of YOLOV8 for 2D image segmentation, with 3D point cloud technology. The YOLO-CE model is used to accurately extract point cloud data from the target area, which is then processed using the MSAC algorithm for efficient plane segmentation. Weld lines are identified through plane equations, allowing for initial weld point cloud extraction. To further refine accuracy, an optimized evaluation equation is developed that accounts for both the distance between the weld point cloud and the fitted plane, and the angle between their normal vectors. This enables precise classification of the weld point cloud. From this classification, key weld feature points are identified, and their exact positions are determined by calculating the distances between these points and their intersections with three planes. The reliability of the proposed method was validated using a robot for precise measurements, with a total error margin of less than 1.5084 mm, demonstrating high accuracy and stability. Post-operation inspections confirmed that the welds were filled and free from defects, meeting all process requirements. The YOLO-CE model achieved a mIoU of 96.38% and a precision of 99.8%, highlighting its effectiveness. This method provides an efficient and precise solution for the automated welding of non-standard steel structural components and has promising application potential.

A comparative analysis of metaheuristic algorithms for optimizing curved roof structures

This article explores the optimal design of curved steel structures with a focus on minimizing their weight by determining the most suitable cross-sections. Customized optimization algorithms were developed to identify structural designs that meet safety and durability requirements, adhering to design constraints set by the ASD-AISC specification. To ensure reliable results, the study employs a variety of metaheuristic optimization methods: Biogeography-Based Optimization (BBO), Dynamic Harmony Search (DHS), Wolf Colony Algorithm (WCA), and Honey Badger Algorithm (HBA). The Honey Badger Algorithm, a relatively new addition to the field, was used for the first time in the context of structural optimization for curved roof systems. This unique approach aims to evaluate its performance in civil engineering problems and compare it with other established algorithms. The major challenges of this study lie in the inherent complexity of dome structures, which involve a large number of elements and nonlinear constraints. The subdivision of the structure into smaller groups was necessary to manage the computational load, although this introduced additional complexities. Despite these challenges, the metaheuristic methods demonstrated their robustness in addressing such intricate engineering problems. Additionally, data retrieval is facilitated through Open Application Interface (OAPI) functions, enabling seamless data transfer between SAP 2000 and Visual Basic. The study's final design example involves a dome model with 2556 elements, which was both modeled and optimized. The results demonstrate the effectiveness of these optimization algorithms in achieving structurally sound and efficient designs. The insights gained from this study contribute to our understanding of optimized cross-sections in curved steel structures, offering valuable guidance for improving structural performance and minimizing material usage.