Steel Structures Research Articles

Skirt piles in foundation: a structural rehabilitation solution for fixed offshore platforms

An analysis and structural design of strength and ductility level earthquake is presented in this paper. Numerical results show that structural failure under seismic loads is sensitive to the degree of deterioration of structural steel. The structural elements do not present any excess stress, that is, all stress ratios are less than unity. The maximum stress ratio is 0.942, in the superstructure of element 1586-1571, which corresponds to a main deck beam elevation (+) 15,850 m.

Autonomous Image-Based Corrosion Detection in Steel Structures Using Deep Learning.

Steel structures are susceptible to corrosion due to their exposure to the environment. Currently used non-destructive techniques require inspector involvement. Inaccessibility of the defective part may lead to unnoticed corrosion, allowing the corrosion to propagate and cause catastrophic structural failure over time. Autonomous corrosion detection is essential for mitigating these problems. This study investigated the effect of the type of encoder-decoder neural network and the training strategy that works the best to automate the segmentation of corroded pixels in visual images. Models using pre-trained DesnseNet121 and EfficientNetB7 backbones yielded 96.78% and 98.5% average pixel-level accuracy, respectively. Deeper EffiecientNetB7 performed the worst, with only 33% true-positive values, which was 58% less than ResNet34 and the original UNet. ResNet 34 successfully classified the corroded pixels, with 2.98% false positives, whereas the original UNet predicted 8.24% of the non-corroded pixels as corroded when tested on a specific set of images exclusive to the investigated training dataset. Deep networks were found to be better for transfer learning than full training, and a smaller dataset could be one of the reasons for performance degradation. Both fully trained conventional UNet and ResNet34 models were tested on some external images of different steel structures with different colors and types of corrosion, with the ResNet 34 backbone outperforming conventional UNet.

Application of newly proposed hardening laws for structural steel rods

In civil engineering, distinct mechanical properties and behaviors of structural steel rods necessitate a novel approach to material modeling. This study extends the application of recently proposed strain-hardening laws, originally developed for automotive sheet metals, to several structural steel rods (CB240-T and CB300-T). Standard uniaxial tensile tests are conducted for each examined material to obtain experimental stress-strain data. Various curve fitting methods are then employed to refine the parameters of the strain-hardening laws, enabling accurate representation of the steel rods mechanical behavior. Subsequently, these laws are implemented in Abaqus software for numerical simulation of uniaxial tensile tests, facilitating the analyses of material response under uniaxial tensile loading condition. Compared to the measured data, the predicted force-displacement curves are in good agreement with the measurements until the tail of the curves. The comparisons verify the ability and potential of the examined hardening law for studying the post-necking behavior of structural steels. The outcomes provide a framework for more precise characterization of structural steel materials.

Evolution of the Lamellar Pearlite Structure of Rail Steel under Tension

Evolution of the Lamellar Pearlite Structure of Rail Steel under Tension

Influence of Deformation on the Structural–Phase State of Structural Steel and on the Formation of Its Yield Strength and Degree of Hardening

Influence of Deformation on the Structural–Phase State of Structural Steel and on the Formation of Its Yield Strength and Degree of Hardening

Local relaxation of residual stress in high-strength steel welded joints treated by HFMI

AbstractThis research studies the influence of high-peak loads on local relaxation of residual stress and fatigue damage in high-strength steel welded joints treated by high-frequency mechanical impact (HFMI) treatment. The joint behavior is simulated with elastic–plastic finite element analyses that account for the combined effect of geometry, residual stress, and material properties. This simulation uses two treated geometry models: with or without surface roughness on HFMI groove, and two material properties: S690QL and AH36 structural steels. The results show that surface roughness and load history, including high-peak loads, significantly influence fatigue response. It is revealed that the model neglecting the surface roughness cannot represent the amount of residual stress change and fatigue damage at less than 100 µm depth from the surface. In addition, the local yield strength in the HFMI-treated zone affects the plasticity behavior near the surface imperfection under the high-peak loads, which provides comparatively different fatigue damage between S690QL and AH36 in some cases. As a result, this study provides the further understanding needed to develop a robust modeling approach to the fatigue life estimation of HFMI-treated welds subjected to high-peak loads.

Durability of Fe-SMA/steel single-lap joints exposed to hygrothermal environments

Due to the adverse impact of hygrothermal environments and fatigue load, the performance degradation of existing steel structures necessitates repairs to extend their service life. Structures retrofitted by bonding iron-based shape memory alloy (Fe-SMA) have been demonstrated as an active non-destructive repair method. Nevertheless, the deterioration of the adhesives triggered by hygrothermal environments is a crucial challenge in its practical reinforcement applications. In this study, 54 Fe-SMA/steel single-lap joints (SLJs) are aged in 55°C and 98 % relative humidity environments for 30, 60 and 110 days, and tested under shear loads. The long-term performance, failure patterns, load-displacement responses and shear-resistance capacity of the SLJs are investigated, considering the essential parameters of aging time, overlap length and adhesive types. The experimental results exhibit that the failure patterns of aged Fe-SMA/steel SLJs depend highly on the adhesive types. The shear-resistance capacity of Fe-SMA/steel SLJs decreases dramatically with the prolongation of aging time. After 110 days of aging, the shear-resistance capacity of type-C, type-S and type-P SLJs decreases by about 14 %, 39 % and 49 %, respectively. When the overlap length increases from 50 mm to 150 mm, the shear-resistance capacity of type-C, type-S and type-P Fe-SMA/steel SLJs improves by 21 %, 39 % and 22 %, respectively, increasing the overlap length can safeguard the optimal functionality and long-term performance of the retrofitted steel structures. While the environments are relatively aggressive, it is recommended to use type-C adhesive to obtain the satisfactory serviceability of the retrofitted steel structures. The experimental achievements are significant for repairing deteriorated steel infrastructures by bonding Fe-SMA, guaranteeing the long-term performance and normal-use safety of structural reinforcement design, and reducing carbon emissions due to the avoidance of reconstruction.

Cyclic Void Growth Model Parameter Calibration of Q460D Steel and ER55-G Welds after Exposure to High Temperatures

When high-strength steel is heated to high temperatures and then cooled naturally, its ductility decreases. In earthquake-prone areas, it is necessary to evaluate the ultra-low cycle fatigue fracture (ULCF) behavior of high-strength steel structures after a fire if these structures are used continuously. However, the ULCF fracture model of high-strength steel subjected to high temperatures followed by natural cooling has not been deeply studied. In view of this, twelve notched, round bar specimens fabricated from Q460D steel and ER55-G welds were heated to 900 °C followed by natural cooling and then cyclic loading experiments and finite element analyses (FEA) were performed on these specimens. The fracture deformation obtained from the experiments was used in the FEA to calibrate the damage degradation parameter of a Cyclic Void Growth Model (CVGM) of Q460D steel and ER55-G welds under this condition. The calibrated values were 0.30 and 0.20, respectively. The calibrated CVGM was employed to predict the number of cycles and the force and displacement at the fracture moment of the notched round bar specimens. The predicted results aligned closely with the experimental results, indicating that CVGM is effective in predicting the fracture of Q460D steel and ER55-G welds following exposure to 900 °C and subsequent natural cooling.

Determination and analysis of stress concentration factor in finite plate with different polygonal discontinuities under uniaxial compression using finite element analysis (FEA)

Stress concentration is the accumulation of stress in a body due to a sudden change in its geometry. Stresses and stress concentrations are created at the nearer area of the structural discontinuities. Any structural discontinuity compromises the strength of the structure. Numerical approaches can be used to determine the maximum stress concentration for various complex geometries without regard to time or cost constraints. The current study gives a thorough finite element analysis of stress concentration in a structural steel plate with a polygonal cutout. In contrast to orientation and area, this study looks at an isotropic finite plate for the stress concentration factor (SCF) with central polygonal cutouts (triangular, square, pentagonal, and hexagonal). ANSYS, a finite element program, calculates the von Mises stresses, and based on the results, stress concentrations are calculated. The orientation of polygonal cutouts in a square plate and the constant area of polygonal cutouts in a square plate are two parameters considered in the calculation. These results are verified by literature for the orientation of the hole, which concludes that a square hole position parallels the loading direction showing a 50% reduction in stress concentration factor.

An Integrated Building Information Modeling and Life-Cycle Assessment Approach to Facilitate Design Decisions on Sustainable Building Projects in Canada

In the context of the digital and sustainable transformation of building projects, the integrated approach of Building Information Modeling (BIM) and life-cycle assessment (LCA) has been widely studied. Recent advancements in such integrated modeling processes and techniques have not yet provided reliable and robust decision-making capabilities for designers to intuitively choose between material alternatives. This study develops a new design framework that integrates BIM, LCA, and multi-criteria decision-making (MCDM) algorithms to facilitate sustainable design processes in building projects. A case study using a single-family housing project in the British Columbia province of Canada was implemented to test the designs to demonstrate the effectiveness of the proposed integrated framework, including a three-way comparison of design scenarios—conventional hot-roll steel, recycled steel, and timber. The results indicate a significant performance improvement with the adoption of recycled structural steel materials, surpassing conventional steel designs and demonstrating a similar performance to that of timber designs. The study underscores the importance of informed decision-making in material selection, driven by the quantitative analysis of digital designs and multi-criteria evaluation (e.g., social carbon cost). This integrated framework offers a valuable tool for designers, engineers, and builders to achieve sustainability when designing building projects through the systematic and rapid comparison of environmental performance.

Failure mechanisms in pre-tensioned bonded hybrid joints

ABSTRACT This study investigated the failure mode of pre-tensioned bonded hybrid joints in steel structures using Digital Image Correlation (DIC) alongside Finite Element Analysis (FEA) and compared the results with those of adhesive bonded joints of identical geometry. While all joint types initially exhibited ideal adhesive joint behaviour at low loading levels, with linear elastic response, differences emerged as loading increased. In particular, hybrid joints exhibited out-of-plane deformations near the ends of the splice plates, a feature not observed in bonded joints. Shear deformations consistently peaked at the ends of the overlap for all joint types and increased with increasing load levels. In contrast to bonded joints, hybrid joints demonstrated resilience under escalating loads, maintaining resistance due to the presence of bolts despite the increased deformations. This study contributes to the understanding of the observed failure mode: while hybrid joints initially resembled ideal bonded joints at lower loads, increasing loads caused critical cracks to initiate at the overlap ends in the adhesive layer, culminating in bonded joint failure. In conclusion, this study has elucidated the failure mode of hybrid joints, providing insights for modelling and dimensioning in steel structures.

Subcontractor Engagement in the Two-Stage Early Contractor Involvement Paradigm for Commercial Construction

Commercial construction projects (CCPs) in New Zealand contribute more to the economy than other project types. However, many face cost and time increases due to inadequate planning. Procurement pathways that involve contractors during design development provide more time to plan, collaboratively. Nevertheless, most projects are procured through traditional tender where contractors are only involved after detailed design. Through two-stage early contractor involvement (2S-ECI), contractors can provide design buildability advice for complex projects, contribute value management, carry out exploratory works, and order materials. The role of subcontractors in 2S-ECI can be significant. Six semi-structured interviews were conducted with clients, consultants, main contractors, and a subcontractor involved in large complex commercial construction projects. The findings build on the emerging body of knowledge about 2S-ECI by providing insight into subcontractor early involvement. Project complexity and market conditions were the main reasons for early subcontractor involvement. Common challenges include a lack of information sharing among the parties, non-competitive selection, and a lack of standard contract documentation. Opportunities for improvement include clarifying client expectations, educating stakeholders, and providing more equitable compensation for pre-construction services. Key drivers for subcontractor involvement include project complexity, market conditions, ordering long-lead-time systems, and performance specifications. Specialist early sub-trades include electrical, mechanical, structural steel, and façades. Subcontractors should typically be engaged as early as possible, often concurrently via main contractors to share performance risk. Pre-construction services provided by subcontractors include planning and sequencing; design buildability analysis; risk mitigation; value management; budget advice; systems procurement; design solutions; and document control systems. Advantages include obtaining specialist project knowledge and improving completion certainty. Producing a pre-construction services agreement (PCSA) for subcontractors may address challenges, as has been carried out for main contractors, but there is still a gap in the contractual framework for 2S-ECI for subcontractors.

Crack Detection of Structures using Artificial Intelligence System

Abstract: Structural Health Monitoring (SHM) having wider scope of operations such as structural audit, rehabilitation of structures and along with it a major scope of crack detection is also included. Effective crack detection is vital for ensuring the safety and longevity of civil engineering structures. Crack Detection in existing methods is tedious process, it requires costly equipment’s as well as time consuming, and inaccuracy in mechanical equipment’s. The technological advancements especially in the field of Artificial Intelligence (AI) maybe an acceptable solution for crack identification through mobile app using Image processing techniques. The mobile app can be used to accurately identify crack pattern and measure the size of cracks in structures (concrete and steel). The app needed to capture and process data from diverse sources, such as images, in real time. It allows for real-time monitoring of structures and ensures safety and integrity of it. The image processing algorithm is used for to accurately identifying various types of cracks in different lighting, environmental conditions, effective and optimized solution. This project explained about real-time data processing for crack detection and its challenges. This demanded robust backend infrastructure and efficient data processing techniques to deliver prompt and accurate results. User Interface and Experience developing an intuitive and user-friendly interface for the app while maintaining high performance.

Mechanical Properties of S235 Steel Protected with Intumescent Coatings Under High Temperatures: An Experimental Study

This study investigates the impact of high temperatures on the mechanical properties of fire-protected versus unprotected S235 cold-formed steel (CFS) specimens with variable thicknesses. Through axial tensile tests, we assessed how intumescent coatings influence the behavior of steel under fire-like conditions. The results reveal that as temperatures increase, the mechanical strength of unprotected steel diminishes significantly, especially at temperatures beyond 400 °C. However, at temperatures between 500 and 900 °C, coated specimens demonstrate considerably enhanced strength compared to their uncoated counterparts. The coating effectively reduces the steel’s temperature exposure by approximately 200 °C, crucially preserving its integrity at critical temperatures. The thickness of the steel also plays a role, with thicker specimens maintaining higher ultimate strength up to a threshold temperature. The study culminates in a predictive analytical model that estimates the ultimate strength of coated and uncoated steel based on temperature and specimen thickness. These insights contribute substantially to the design of safer, more fire-resistant steel structures.

A Study on Crack Initiation and Propagation of Welded Joints under Explosive Load

Welded joints in naval ship hull structures are weak areas under explosive load, but there are relatively few studies investigating the failure characteristics of welded joints through dynamic fracture and explosion tests. In order to explore and predict the failure characteristics of welded joints under explosive load, instrumented Charpy impact tests, explosion tests, and numerical simulations were carried out. The dynamic fracture toughness of ultra-high strength ship hull structural steel welded joints was obtained, and the dynamic stress intensity factors, together with the correlation between stress wave and crack propagation at different positions, were acquired. The results showed that the stress state at the crack tip of a Charpy impact specimen was consistent with that of a welded joint under explosive loads, and the crack initiated when the dynamic stress intensity factor exceeded the dynamic fracture toughness. The results indicated that the dynamic fracture toughness obtained by instrumented Charpy impact tests could be used to predict the crack initiation characteristics of welded structures under explosive load, and the stress wave at the crack tip was basically perpendicular to the crack propagation surface and promoted the rapid propagation of cracks.

Unveiling the effect of electron beam shock on the microstructure and wear resistance of Cr12MoV steel

Enhancing wear resistance is the core factor that prolonged the life of the Cr12MoV mold and elevates the quality of the components produced. Hence, Cr12MoV mold steel was shocked by scanning electron beam (SEB) to improve wear resistance. Results revealed that the segregation eutectic carbides in the surface structure of Cr12MoV steel were dissolved during the shock process of various beam electron beams, and the small particles of carbides produced are helpful in reducing wear. With an energy density of 20 J/mm2, surface roughness of Cr12MoV steel decreases from 2.9 μm to 1.2 μm, the friction coefficient decreases from 0.85 to 0.52. Additionally, the wear capacity also decreases from 0.036 mm3 to 0.011 mm3, and surface wear resistance increases by over 3 times. Grain refinement-induced surface hardening is the primary cause underlying performance improvement. This study provides ideas for improving the surface quality of Cr12MoV steel.

Study and Analysis of Steel, RCC, and Composite Structure Comparison

In India, plain concrete is a common building material, especially for medium- and low-rise buildings. Even while steel is still widely used in high-rise structures and composite construction is less frequent, it's possible that composite construction could prove more beneficial in these projects. Reinforced concrete is often used in construction projects. Steel beams are put into concrete to make reinforced concrete, an efficient composite material. The distinguishing feature of composite construction is the secure joining and bending of two load-bearing structural elements into a single piece. When compared to RCC most steel frames, composite constructions are considered to be some of the least expensive and transient building materials. The main component of a composite construction is an I-section column embedded or encased in building materials, or a tube of steel filled with steel and concrete. Composed of cold steel plates plus mortar, Part I consists of a beam plus a plate for the deck. The beams are connected to the top slab using fire-resistant and robust shear connections. Keywords— Steel Concrete Composite Building, RCC building, Seismic Analysis etc.

Advanced analysis and construction techniques for long-span spatial structures in steel engineering

This paper explores advanced analysis methods and construction techniques for long-span spatial structures in steel engineering. It delves into the principles of the Direct Analysis Method (DAM), emphasizing equilibrium, compatibility, plasticity, and stability, as well as load path and redundancy considerations. The DAM provides a robust framework for analyzing complex steel structures, ensuring stability, resilience, and efficiency. Furthermore, the paper discusses modeling techniques, including Finite Element Analysis (FEA), dynamic analysis, and nonlinear analysis, highlighting their significance in optimizing design solutions and predicting structural behavior under diverse loading conditions. Practical considerations in material selection, connection design, and construction are addressed, focusing on enhancing performance, durability, and constructability. Prefabrication and modular construction techniques are explored as effective strategies for accelerating project schedules, improving quality control, and enhancing site safety. Through a comprehensive review of literature and case studies, this paper provides valuable insights for engineers and researchers involved in the design and construction of long-span spatial structures in steel engineering.

Post-fire mechanical properties of titanium-clad bimetallic steel after cold-forming process: Experiment and constitutive model

Titanium-clad bimetallic steel (TCBS), composed of a titanium alloy cladding layer and carbon steel substrate layer, has been proposed to mitigate the effects of corrosion and enhance the durability of steel structures. This study conducted tensile coupon test to explore the coupling effect of the cold-forming process and fire exposure on the monotonic mechanical properties of TCBS. Following the cold-forming process and fire exposure, there was no visible cracking observed in either the cladding or the metallurgical bonding layer. Test results revealed a notable enhancement in the strength properties and a decrease in the ductility of the TCBS specimens after cold forming. Moreover, the study elucidated the effects of the exposure temperature and cooling method on the stress–strain curves and fractures of TCBS corner specimens. Three different fracture sequences of the TCBS corner specimens were observed during monotonic tensile test. The key mechanical parameters were concerned in this study, which included the yield and ultimate strengths, yield and ultimate strains, elastic modulus, elongation after fracture, and section shrinkage. Then, the variation trends of key mechanical parameters were clarified. Predictive equations were developed for these parameters of the TCBS corner specimens after fire exposure. Additionally, two constitutive models were developed for the corner TCBS stress–strain curves with and without the yield plateau, enabling their use in numerical and theoretical investigations of the post-fire performance of cold-formed TCBS components.

A comprehensive investigation of the process and atmospheric coupling corrosion on corroded and mechanical properties of the SPA-H weathering steel

Weathering steel has recently become popular in engineering due to its corrosion resistance, but its mechanical characteristics must alter during double corrosion, process chemical solution corrosion (CSC), and atmospheric corrosion (AC). However, no studies have been published on the coupling effect of process and atmospheric corrosion. The durability and safety of weathering steel structures can be challenging to assess. As a result, we used SPA-H weathering steel as the object, ran process corrosion and double corrosion simulations (process corrosion plus atmospheric corrosion simulation), and created three corrosion conditions: non-corrosion, single-side corrosion, and double-side corrosion. CSC was the corrosion process. Following CSC, the second (120, 360, 720, and 1200 hour) Copper-Accelerated Acetic Acid-Salt Spray Testing (CASS) was performed to simulate atmospheric corrosion. A correlation analysis was conducted using the grey correlation method between indoor and atmospheric corrosion. After corrosion testing, these specimens were subjected to White Light Interferometry (WLI) and tensile coupon tests (TCT) to evaluate the corrosion characteristics and the deterioration of material mechanical properties. Finally, linear fitting was used to produce the calculation formula between the mechanical properties and the mass loss ratio of single-side and double-side corrosion.