Steel Sections Research Articles

Experimental investigation of the bond-slip behavior between steel section and concrete under different loading histories

Experimental study of interfacial bonding performance between section steel and ultra-high performance concrete in PUES beam with the hollow section

Design and analysis of special concentrically braced frames with A500 and annealed A500 square hollow section steel braces

This article investigates the structural resistance of thin-walled steel sections classified as Classes 1 to 4 under Eurocode 3. The study focuses on flexural capacity, and takes into consideration the effects of local buckling and the bimoment. Although Class 1 and 2 sections can develop complete plastic resistance, Class 3 sections are limited to elastic behavior prior to local instability. For Class 4 sections, effective width methods are employed to account for the reduction in strength due to early local buckling. Based on Eurocode formulations, these approaches are extended to incorporate the influence of the bimoment, which is significant in thin-walled open sections under non-uniform torsion. A comparative analysis between analytical models and numerical simulations is presented, with an emphasis on how the bimoment alters stress distributions and reduces the effective widths of slender plates. The results underscore the necessity of including these effects in the structural design of thin-walled members, particularly for open profiles subjected to bending and warping.

ABSTRACTModern structural applications are increasingly using cold‐formed steel (CFS) sections because of their high strength‐to‐weight ratio and ease of fabrication. These sections come in open (C, Z, L), closed (tubular, box), and built‐up configurations. To forecast their performance under axial, flexural, and combined loading, traditional analytical and finite element methods (FEM) are computationally demanding and frequently unsuccessful in capturing intricate buckling interactions, residual stresses, and geometric imperfections. A promising substitute is offered by recent developments in machine learning (ML), which allow for quick, highly accurate predictions based on data. According to studies, ML models like artificial neural networks (ANNs), support vector machines (SVM), convolutional neural networks (CNN), and gradient boosting can greatly increase predictive accuracy. For example, when compared to traditional methods, R2 scores for axial strength predictions increased from 0.75 to 0.94. Three areas of future research are highlighted in this review, which critically analyzes ML applications in CFS research: (i) creating real‐time surrogate models that are integrated into design platforms; (ii) combining mechanics‐based techniques such as the direct strength method (DSM) with explainable machine learning (XML); and (iii) adding uncertainty quantification (UQ) to improve reliability. Centralized dataset creation, adaptive health monitoring, and the integration of sustainability objectives are further directions. This study offers researchers and practitioners a path forward for ML‐enabled CFS design by bridging the gap between high‐fidelity simulations and realistic design workflows. The results show that in order to guarantee safe, effective, and sustainable structures, interpretability, code compatibility, and industry adoption are as important as the transformative potential of ML.

This paper reviews the calculation of shear studs in the load introduction area (LIA) of concrete-encased steel composite columns, focusing on their role in transferring shear forces between the concrete and the embedded steel section. Based on recent literature, especially the stiffness-based approach proposed by Grzeszykowski et al. (2023), the study highlights key factors influencing shear transfer, such as load distribution, material properties, and stud arrangement. Through a critical review of current design practices and assumptions in international codes, the paper identifies limitations in traditional strength-based methods, particularly at service load levels. In contrast, the stiffness-based method (StiffM) considers partial interaction and connector stiffness, offering a more realistic evaluation than the conventional strength-based method (StrM). Case studies are briefly discussed to demonstrate the practical implications of adopting a stiffness-based design perspective, which may improve structural efficiency and safety.

Geometric properties i.e., elastic and plastic section moduli of unsymmetrical sections is determined through a method used by the American Institute of Steel Construction, AISC. This method is based on the assumption that neutral axis always remains parallel to the legs of sections, however, in reality when an unsymmetrical section is used as a flexural member, and load is applied about an axis parallel to one of the legs of the section, biaxial bending is produced in the section which adjusts the placement of neutral axis to a state where the neutral axis does not necessarily continue to be parallel to the legs of section. AISC uses the same procedure for the design of unsymmetrical steel sections as that for symmetrical sections. As design is usually based upon their geometric properties like elastic and plastic section moduli, moment of inertia, etc., so AISC method yields unsafe and uneconomical results. Therefore, unsymmetrical sections should be designed using the author’s recommendations based upon their actual analysis. This paper deliberates the incorrect use of values of the AISC in the given circumstances and presents an alternative procedure for the easy and correct design of unsymmetrical sections. This involves the use of equivalent section moduli, Sx, and Zx including the effect of lateral bending.

This study numerically investigates the effect of different welding steel plate shapes on the behavior of expanded open web asymmetrical steel composite beams. Increased web depth of asymmetrical steel beams in composite concrete results in increased stiffness and strength. Expanding the web's depth enhances the composite concrete steel beam's strength and performance in specific design scenarios, such as expanded, cellular, or castellated steel composite concrete beams. A horizontal cut in the web in each asymmetrical section can create an expanded web of asymmetrical steel profiles. Two asymmetrical tees can then be assembled, and a plate known as a spacer plate with a constant area and different shapes can be added between the two halves of the asymmetrical tee sections. The Finite Element (FE) numerical model developed by ABAQUS software was employed to develop and evaluate new numerical models by considering a variety of increment plate configurations, which resulted in the production of a greater number of models at a lower cost and more efficiently. The results indicate that curved plates increased the ultimate load capacity, while other shapes led to decreased stiffness. Therefore, the ultimate load capacity of the curved plate increased by approximately 2.3% compared to the reference model due to a reduced stress distribution.

Soil strengthening with hydraulic binders has gained popularity in recent years and provides an alternative to traditional methods, both for foundation reinforcement and for retaining walls. In many cases, columns, walls, or soil-cement mix blocks require reinforcement with steel sections. Correctly assessing the load-bearing capacity of a reinforced element requires an understanding of the bonding forces between the steel and the soil-cement mix. This article presents the results of pull-out tests conducted on steel flat bars embedded in a soil-cement mix. A soil-cement mix containing sand, silt, and clay fractions was prepared. The surfaces of the flat bars were treated in three different ways, and their roughness was subsequently measured. The pull-out strength of steel flat bars embedded in a soil-cement mix with compressive strength in the range of 1–2 MPa was determined. The tests revealed a correlation between surface roughness and bond strength. The conducted tests provided the basis for developing new research directions and for formulating a new bonding model for the interaction between steel profiles and soil-cement.

Steel-reinforced concrete (SRC) structures combine steel skeletons with concrete components, improving load-bearing capacity and streamlining construction. In this study, four full-size lattice SRC members were tested under pure bending to validate fundamental assumptions and were further analyzed numerically. The experimental specimens demonstrated a 15.3% increase in ultimate load-carrying capacity and an average 58.7% increase in the ductility index compared with conventional members. Notably, the improvement in ductility was substantially greater than the enhancement in load-bearing capacity. In parallel, a load-bearing capacity formula for lattice SRC members was proposed, yielding an error margin of 0.136 when compared with existing formulae for section steel members. The flexural strength predictions of formulae derived from simplified elastic–plastic theory and numerical analysis agreed with the test results.

The full-scale military invasion of Ukraine by the Russian Federation in February 2022 caused widespread damage to civilian infrastructure, including large-panel residential buildings constructed primarily in the late Soviet period. These structures are prevalent in urban districts like Saltivka, a densely populated area of Kharkiv located near the state border. Due to their modular design and proximity to frontline hostilities, many of these buildings experienced either partial or complete destruction, particularly affecting floor slabs.This study investigates the restoration of floor systems in damaged large-panel buildings and proposes a practical, innovative reinforcement method based on tubular concrete (concrete-filled steel tubes) enhanced with a specialized infill composition. The solution involves constructing a steel subframe integrated with a modified concrete core that includes steel fiber and mineral additives to improve mechanical performance. Structural analysis and experimental tests demonstrated that this configuration significantly improves the stiffness and strength characteristics of floor elements while allowing for a reduction in slab thickness. Compared to traditional solutions, the proposed system offers up to 50 % less deformation than empty steel sections and about 30 % better performance than standard concrete-filled tubes.From a construction standpoint, the design allows for efficient assembly within existing buildings, maintaining room height and minimizing the impact on architectural ergonomics. Additional central beams redistribute loads more effectively, transforming the floor into a system supported along its entire perimeter, which reduces bending moments and enhances load-bearing capacity.This method addresses critical challenges in post-war reconstruction by providing a costeffective, scalable approach to residential rehabilitation. Its compatibility with prefabricated panel housing makes it particularly valuable in regions where restoring living space quickly and safely is essential. The findings confirm that tubular concrete elements with optimized infill materials can serve as a reliable alternative to traditional slab replacement techniques in the context of modern structural retrofitting.

Flexural buckling and design of press-braked rectangular hollow section steel long columns

Experimental and numerical investigation on flexural performance of non-prestressed concrete precast bottom slab with a removable section steel and three ribs

The increasing adoption of back-to-back built-up cold-formed steel (CFS) channel columns in construction is attributed to their lightweight nature, versatility in shape fabrication, ease of transportation, cost efficiency, and enhanced load-bearing capacity. Additionally, the incorporation of web openings facilitates the integration of electrical, plumbing, and heating systems. These built-up sections are widely utilized in wall studs, truss elements, and floor joists, with intermediate screw fasteners strategically positioned at regular intervals to prevent the independent buckling of channels. Based on 18 experimental tests, this study demonstrates an excellent correlation between finite element analysis and the experimental results, confirming the accuracy of geometrically and materially nonlinear finite element modeling in predicting the axial buckling strength of built-up short columns. Furthermore, the design standards of the American Iron and Steel Institute and Australian/New Zealand Standards were found to underestimate the axial load capacity by approximately 12.5%. The primary objective of this research is to investigate the influence of various hole configurations, both with and without stiffeners, on the axial performance of built-up short CFS channel columns. A total of 180 finite element models were developed, examining four different unstiffened and edge-stiffened hole configurations, validated against experimental results from plain webs. The findings reveal that web holes and edge stiffeners significantly impact axial load-bearing capacity, while the specific shape of the openings has a negligible effect. Specifically, introducing a hole at the centroid of each web results in an approximate 8.5% reduction in axial load capacity in the absence of edge stiffening. However, the incorporation of stiffeners around the perforations mitigates this reduction and enhances both structural efficiency and load-bearing capacity. These results highlight the critical role of edge stiffening in optimizing the structural performance of perforated built-up CFS columns.

This research presents a detailed parametric study of the thermal behaviour of concrete-filled steel tubular (CFST) sections as they respond to different fire exposure conditions. After validation of the model, 18 finite element models were developed to analyse the effects of fire duration, section size, steel tube thickness, aspect ratio, and heating configurations on heat transfer behaviour. The temperature-dependent thermal properties per Eurocode standards were employed to model material degradation. The results indicate the effects of geometric parameters and heating orientation on the distribution of internal temperatures and temperature gradients. While the concrete core delays heat progression, it was found from this study that cross-sectional area and fire exposure direction significantly dictate the rise of core temperature and heat flux. Moreover, the analysis investigates the insight progression of thermal interaction at the steel–concrete interface, mainly in square CFSTs – an area with fewer detailed investigations. These findings offer improved thermal characterisation of CFSTs and provide an excellent base for performance-based coupled thermo-mechanical analysis to enhance fire-resistant design.

Experimental study on the flexural response of UHPC beams encased high-strength section steel

Currently, both Chinese and international standards have not addressed the fatigue design for encased composite beams with welded shear studs (ECB-S), which undoubtedly limits the application of encased composite structures under fatigue loading conditions. This paper, combining a series of existing fatigue test results for ECB-Ss, proposes a fatigue design method for ECB-S that can serve as a reference for practical engineering design. Regarding the flexural fatigue failure characteristics of ECB-S, the overall safety of ECB-S is ensured through individual fatigue designs for key components such as the embedded steel sections, tensile rebars, and encasing concrete. Specifically, the fatigue design or verification of tensile rebars is based on the design S - N curve obtained from forty-two S - N data points in ECB and ECB-S fatigue tests, taking into account the effect of stress ratio. The fatigue design or verification of embedded steel sections is based on the S - N curve derived from eight S - N data points in ECB-S fatigue tests, considering the coupling effects of fractures between embedded steel sections and tensile rebars. For the compressive concrete, the fatigue design methods in the current reinforced concrete structural codes are directly applied for verification. Finally, the feasibility and rationality of the ECB-S fatigue design method proposed in this paper are validated by fatigue test results, and corresponding fatigue design recommendations are provided. The mean values of ratios of fatigue lives between the calculated values by the design method and experimental values are 0.403 for embedded steel sections and 0.280 for tensile rebars. Additionally, the maximum compressive stress in concrete remains below its compressive fatigue strength. The findings of this paper can offer reference and guidance for the practical engineering design of ECB-S.

This study introduces a new method for modeling the nonlinear behavior of adhesively bonded composite steel–concrete T-beam systems. The model characterizes the interfacial behavior between the steel beam and the concrete slab using a strain compatibility approach within the framework of linear elasticity. It captures the nonlinear distribution of shear stresses over the entire depth of the composite section, making it applicable to various material combinations. The approach accounts for both continuous and discontinuous bonding conditions at the bonded steel–concrete interface. The analysis focuses on the top flange of the steel section, using a T-beam configuration commonly employed in bridge construction. This configuration stabilizes slab sliding, making the composite beam rigid, strong, and resistant to deformation. The numerical results demonstrate the advantages of the proposed solution over existing steel beam models and highlight key characteristics at the steel–concrete interface. The theoretical predictions are validated through comparison with existing analytical and experimental results, as well as finite element models, confirming the model’s accuracy and offering a deeper understanding of critical design parameters. The comparison shows excellent agreement between analytical predictions and finite element simulations, with discrepancies ranging from 1.7% to 4%. This research contributes to a better understanding of the mechanical behavior at the interface and supports the design of hybrid steel–concrete structures.

This research investigated and compared the structural behavior of reinforced concrete straight beams and beams made with out-of-plane parts. This study focused on the influence of the location and number of out-of-plane parts, as well as encasing the beams with a steel section, on the ultimate strength, deflection, and rotation in addition to the ductility, energy absorption, and failure mode. A total of nine beams were modelized numerically, divided into three series. The first one included one straight beam, while the remaining two series included four beams each made with out-of-plane parts with and without steel sections. The beams with out-of-plane parts connected the two, three, four, and five concrete segments. The outcomes revealed that the beams made with out-of-plane parts showed less strength than straight beams, which increased the connected segments and reduced the ultimate strength capacity. The regular beam’s linearity was dissimilar to the zigzag beams, which showed a linearity of 32% and was reduced to 22%, 20%, 19.67%, and 16% for beam out-of-plane parts made with two, three, four, and five segments, respectively. Forming a zigzag in the plane of the beams reduced the cracking load, but the decrement depended on the number of parts, which led to more reduction in the yielding load. Concerning the deflection and deformations, the concrete straight beams failed in flexure, with maximum deflection occurring at the midspan of the beam, which was different for beams without plane parts, which showed a combined shear-torsional failure for which the maximum deformation occurred at the midspan with inclination of connected parts on the interior perpendicular axis. Encasing the beams’ out-of-plane parts with steel sections enhanced the structural behavior. The ductility and energy absorption of the out-of-plane parts beams were less than the straight ones, but encasing the beams with a steel section improved the ductility and energy absorption twice.

Partially Encased Composite (PEC) columns are structural elements comprising a steel section with concrete partially encased between the flanges. These columns are widely adopted in multistorey building construction, particularly as corner columns, due to their ability to optimize floor space and provide structural efficiency. Despite their advantages, PEC columns are susceptible to issues such as inadequate bond strength between steel and concrete, local buckling of steel components, and crushing of the encased concrete under axial loads. This study focuses on evaluating the global stability of a partially encased composite column with an L-shaped cross-section (L-PEC column), aiming to enhance bond strength and load-bearing capacity. The research explores the effect of incorporating castellations and corrugations on the steel web to improve the interaction between steel and concrete. Additionally, the use of steel hoops and carbon fiber-reinforced polymer (CFRP) wrapping is investigated to mitigate local buckling and concrete crushing, thereby enhancing the overall structural performance. A detailed parametric study was also carried out to assess the influence of various factors on the column's behavior.