Steel Structures Research Articles

Improving stability in hybrid fire testing: Advancements in analysis method and software implementation

In large-scale structural fire resistance tests, the interaction between the individual elements and the surrounding structure causes discrepancies in behaviour compared to single-element fire tests. Large-scale tests of real structures are challenging due to financial and time limitations. To bridge this gap, the concept of “Hybrid Fire Testing (HFT)” emerges, where a portion of the structural system (i.e., physical substructure) is experimentally tested while the remaining structure (i.e., numerical substructure) is analyzed numerically. The primary challenges in HFT involve ensuring stability throughout the analysis by considering the varying stiffness of the fire-exposed element during the test and establishing a versatile communication platform between the physical substructure (PS) and numerical substructure (NS) components. This paper presents a comprehensive HFT framework, implemented within a user-friendly software interface, facilitating both virtual and experimental testing. The software incorporates a new method addressing stability concerns by predicting PS stiffness during the test, achieving convergence within a limited number of iterations. Additionally, the framework includes a communication platform utilizing internet protocols (IP) and COM ports for rapid and easy connection to diverse experimental control systems and finite element software packages. The functionality of the developed software is validated through its successful application in an HFT conducted on a 3-story steel structure within a simulated environment. Both force-controlled and displacement-controlled approaches confirm the method’s adaptivity to the employed test procedures.

Seismic Behavior of Steel Reinforced Ultra-High Strength Concrete Composite Frame: Experimental and Numerical Study

The seismic behavior of steel reinforced ultra-high strength concrete (SRUHSC) composite frame was investigated through finite element analysis (FEA) modeling. A FEA model for the seismic analysis of the SRUHSC frame was first established and verified with test results. The numerical model was subsequently used to study the seismic performance of the SRUHSC frame, including the P-Δ skeleton curves, the stiffness degradation, the failure mode, the subsequence mechanisms of plastic hinges and the stress–strain distribution. Finally, a parametric study was carried out to investigate the effect of salient parameters on the behavior of the SRUHSC frame. It was found that with the increment of the concrete strength, yield strength of steel, and linear stiffness ratio of beam to column, the horizontal load-bearing capacity and the elastic stiffness of the structure were improved, but there was no significant effect on the ductility. With the increment of the volume stirrup ratio and structural steel ratio, the horizontal load-bearing capacity and the ductility of the structure were both improved. However, with the increment of the axial-load ratio, there was no obvious change in the elastic stiffness of the structure, but the horizontal load bearing capacity and the ductility of the structure decreased obviously. In addition, the accuracy of a concrete constitutive model in the different degrees of constraint for the SRUHSC frame proposed by the authors was verified with the FEA model.

Low- and elevated-temperature constitutive model of cold-formed titanium-clad bimetallic steel sections

An experiment was conducted to study the mechanical properties of the flat and corner portions of cold-formed TCBS sections at low and elevated temperatures. The predetermined temperatures were set at −80 °C, −40 °C, 20 °C, 200 °C, 300 °C, 400 °C, and 500 °C. The failure modes, stress-strain curves, and key mechanical parameters of TCBS flat and corner couple specimens at different temperatures were obtained based on test results. The TCBS flat and corner specimens failed in ductile mode. The stress-strain curves of the TCBS flat and corner specimens at different temperatures did not show a yield plateau. The strength properties of TCBS flat and corner specimens at low temperatures obviously increased. The strength properties of the TCBS flat and corner specimens generally decreased with increasing elevated temperature. The cold-forming process increased and decreased the strength and ductile properties of TCBS at different temperatures, respectively. Additionally, the mechanical property reduction factors of TCBS flat and corner specimens at different temperatures were compared with those of various structural steels. Moreover, the applicability of the reduction factors for yield strength and elastic modulus provided in current codes was assessed for TCBS flat and corner specimens. Furthermore, the prediction equations of mechanical parameters and constitutive models were proposed for the TCBS flat and corner couple specimens at different temperatures, which provided a basis for designing TCBS structures in low- and elevated-temperature conditions.

High-Speed Steel Technology Substitution in Mining Machinery – an Experimental Study

The growth of mineral extraction in countries with a developed mineral resource sector under conditions of external restrictions requires the modernization of the domestic mining machinery – an indispensable condition of which is the replacement of technologies for the production of high-speed steels and machine tools. This research was aimed at experimental studies of microstructure, phase composition and microhardness distribution in the surface layer of the R6M5 high-speed steel samples after laser cutting, cold treatment and laser tempering. It was demonstrated that after laser cutting in the surface layer of the cut there was the carbide dissolution and enrichment of the metal matrix with carbon and alloying components, resulting in an increase of residual austenite content up to 50...60 %. After the cold treatment in liquid nitrogen the content of residual austenite decreased up to 7...9 %. The laser cut surface microhardness increased up to 1000...1100 MPa. At further laser tempering the dispersion hardening processes took place, as a result the V2C carbides appeared in the steel structure amounting to 4.7 %. The microhardness increased up to 10400...10600 MPa. The study showed the possibility of using the high-speed steel laser cutting not only as a separating operation, but also as a hardening treatment. The findings contribute to the technological support for the development of domestic mining machinery in terms of replacing imported high-speed steels and machine tools.

Comparative study of fillers for welding E410 structural steel

ABSTRACT An endeavour for creating an understanding of the effect of filler wires (ER-70S6 and ER-80SG) on the mechanical performance of metal inert gas (MIG) weldments of two E410 graded structural steels that differed majorly in carbon contents i.e. 0.04 wt.%C and 0.17 wt.%C was undertaken. Improvements in yield stress (YS) with ER-80SG for MIG weldments of both investigated E410 structural steels were noticed; however, %elongation and room temperature (RT) impact toughness deteriorated as regards to ER-70S6. Almost ⁓5% increase in YS and a drop by ⁓4%, ⁓22%, and ⁓60% in ultimate tensile stress (UTS), %elongation, and toughness, correspondingly, were obtained for 0.04 wt.%C structural E410 steel with ER-80SG over ER-70S6. While moderate ⁓9% and ⁓8% increments in YS and UTS and a decrement of ⁓7% and ⁓40% in %elongation and toughness, respectively, were observed for 0.17 wt.%C steel with ER-80SG over ER-70S6. Enhancement in YS and a fall in %elongation and toughness with ER-80SG compared to ER-70S6 were due to high heat input for performing MIG welding of E410 steel, leading to thorough phase transformations providing fine Widmanstätten ferrite and acicular ferrite structures in weld metal with variable-sized inclusions and dissolved cementite and pearlite sub-structures in heat affected (HAZ) subzones of 0.04 wt.%C and 0.17 wt.%C steels, respectively.

Improvement in inhibition performance of anti-corrosion coatings using polyolefin matrix embedded with modified TiO2 nanoparticles

Corrosion remains a critical issue for steel structures, leading to costly repairs and potential failures in industrial sectors. This study presents the development and characterization of polyolefin coatings for enhanced corrosion protection. Initially, the porous TiO2 nanoparticles were synthesized using the sol-gel method, followed by their modification through the encapsulation of sodium benzoate (SB) as a corrosion inhibitor. Modified Polyolefin coatings were prepared by incorporating modified nanoparticles (TiO2 loaded with sodium benzoate) into the polyolefin matrix, and an unmodified/blank polyolefin coating was prepared without any additive in the polyolefin matrix. The loading of the inhibitor into porous TiO2 was 10 % analyzed using thermogravimetric analysis. Furthermore, the electrochemical analysis revealed significant improvements in the corrosion resistance and barrier properties of the modified coatings compared to the unmodified blank coatings. Specifically, after 7 days in a corrosive environment, the blank coating pore resistance dropped from 1 × 1010 Ω·cm2 to 5 × 108 Ω·cm2, while the modified coating maintained a high pore resistance of 5 × 1011 Ω·cm2. A localized corrosion study for scratched blank polyolefin coatings showed growing corrosion activity from 5 h of immersion, while modified coatings ceased the detectable activity before 4 h of immersion, which evidenced the improved corrosion inhibition efficiency of the modified coating. This stability in corrosive environments was attributed to the successful loading of modified nanoparticles (TiO2/SB), where SB served as an active agent by forming a protective film on the steel substrate. Which inhibits the corrosion processes along with Ti-based compounds and prevents corrosion propagation under the damaged coating. The enhanced hydrophobic nature of 99° and electrochemical properties support the suitability of these coatings for corrosion protection of steel in various industries.

Seismic evaluation of BRBF steel structures with L-shaped irregular plan considering soil-structure interaction

Seismic evaluation of BRBF steel structures with L-shaped irregular plan considering soil-structure interaction

Проектирование современных российских дробильно-перегрузочных установок для комплексов циклично-поточной технологии

The article discusses methodological aspects of designing semi-stationary and mobile crushing and transfer units (DPU) carried out by the experts of Uralmashzavod PJSC and IGD Ural Branch of the Russian Academy of Sciences on behalf of the Russian Metalloinvest company during the development of the Russian DPU-7200 model. As the result of the R&D work performed, a DPU was manufactured and installed at a mining operation as part of the in-pit crushing and conveyor (IPCC) systems, which is intended for conveyor transportation of ore from the open pit. A distinctive feature of the discussed DPU is that it is made as a complete system with the supporting steel structures integrated in its design, which makes it possible to relocate it during the service life when expanding the IPCC. The issues concerned with justifying the DPU layout, parameters of the receiving and unloading hoppers are discussed with account of structural, strength, mining and technological factors. The paper presents the technical characteristics of the developed DPU, as well as the design features of the primary equipment. The impact of the related technological factors, i.e. irregular character of dump truck traffic, the technological and temporal modes of the IPCC operation in general and those of the DPU in particular, the designed schedule of maintenance and repair, etc., is shown.

Проектирование современных российских дробильно-перегрузочных установок для комплексов циклично-поточной технологии

The article discusses methodological aspects of designing semi-stationary and mobile crushing and transfer units (DPU) carried out by the experts of Uralmashzavod PJSC and IGD Ural Branch of the Russian Academy of Sciences on behalf of the Russian Metalloinvest company during the development of the Russian DPU-7200 model. As the result of the R&D work performed, a DPU was manufactured and installed at a mining operation as part of the in-pit crushing and conveyor (IPCC) systems, which is intended for conveyor transportation of ore from the open pit. A distinctive feature of the discussed DPU is that it is made as a complete system with the supporting steel structures integrated in its design, which makes it possible to relocate it during the service life when expanding the IPCC. The issues concerned with justifying the DPU layout, parameters of the receiving and unloading hoppers are discussed with account of structural, strength, mining and technological factors. The paper presents the technical characteristics of the developed DPU, as well as the design features of the primary equipment. The impact of the related technological factors, i.e. irregular character of dump truck traffic, the technological and temporal modes of the IPCC operation in general and those of the DPU in particular, the designed schedule of maintenance and repair, etc., is shown.

Microstructure and corrosion behaviour of structural steel fabricated by wire arc additive manufacturing (WAAM)

Wire arc additive manufacturing (WAAM) is a metal 3D printing technique that allows large-scale elements to be built in a relatively timely and cost-effective manner, well suited to the cost-sensitive construction sector. Despite the potential of this novel technology, the basic properties of WAAM materials remain elusive. This paper presents a comparative study on the microstructure and corrosion behaviour of WAAM steel plates and the conventionally rolled Q345 steel. The WAAM steel exhibited comparable corrosion performance to the conventionally-produced steel within twelve days exposure in 3.5 wt% NaCl solution, including the corrosion current density, and the characteristics of steel/concrete interface, determined through electrochemical impedance spectroscopy (EIS) analysis. Post-corrosion observations revealed that preferential dissolution occurred at (Si, Mn)-rich oxide inclusions, in addition to the general corrosion of surrounding steel matrix. The much higher content of Si and Mn element in the feedstock material WAAM steel resulted in slightly higher susceptibility to localised corrosion, compared to the Q345 rolled steel.

Corrosion of F/M steels and austenitic steels in Pb-Mg at different temperatures

Pb83Mg17 is expected to be a potential coolant for lead cooled fast reactors because of its less toxic radioactive products and possible acceptable corrosion rate without additional oxygen control in comparison with LBE. In order to evaluate the compatibility of structural steels and Pb-Mg, two F/M steels (SIMP, T91) and two austenitic steels (316L, 15-15Ti) were tested in Pb-Mg at 350, 450 and 550 °C with exposure time ranging from 100 h to 2000 h in this work. Compared with the slight corrosion or no obvious corrosion of F/M steels, austenitic steels have suffered very serious dissolution corrosion which is significantly influenced by temperature and exposure time. The corrosion rate of austenitic steels is controlled by dissolution or diffusion mechanism at different temperatures.

Mechanical Properties, Structure and Machinability of the H13 Tool Steel Produced By Material Extrusion

Mechanical Properties, Structure and Machinability of the H13 Tool Steel Produced By Material Extrusion

Mechanical Properties, Structure and Machinability of the H13 Tool Steel Produced By Material Extrusion

Mechanical Properties, Structure and Machinability of the H13 Tool Steel Produced By Material Extrusion

Retrofitting of Steel Structures with CFRP: Literature Review and Research Needs

The application of the externally bonded (EB) carbon fiber-reinforced polymer (CFRP) technique for retrofitting steel elements offers significant advantages over the conventional method. The high strength-to-weight ratio and corrosion resistance of CFRP materials have made them a viable alternative for retrofitting steel structures. This paper covers a wide range of aspects discussed in the research investigations to date on CFRP bonded steel elements and provides a critical review of the topic under both static and fatigue loading conditions. In the end, research needs and recommendations are presented in this respect.

Post-fire behavior and residual resistances of S890 ultra-high strength steel circular hollow sections under combined compression and bending

This paper presents experimental and numerical investigations into the post-fire local buckling behavior and residual resistances of S890 ultra-high strength steel (UHSS) circular hollow section (CHS) under combined compression and bending. The physical testing was firstly conducted and encompassed heating, soaking and cooling of specimens, as well as post-fire tensile coupon tests, measurements of initial local geometric imperfections and eccentrically loaded stub column tests. Then, finite element models were developed and validated with reference to the experimental observations and then adopted for parametric analyses to derive additional numerical data, considering various cross-section dimensions and loading combinations. As a result of the lack of design provisions for ultra-high strength steel structures after exposure to elevated temperatures, the applicability of the relevant ambient temperature design interactive curves given in the current European, American and Australian standards to post-fire S890 UHSS CHS under combined compression and bending was assessed, with post-fire material properties used. The assessment results showed that all design standards exhibited conservative and scattered predictions of residual resistances for S890 UHSS CHS under combined compression and bending at ambient temperature and after exposure to elevated temperatures. The American specification provided more precise predictions of residual failure loads for non-compact and slender (Class 3 and 4) sections than the Eurocode and Australian standard, due to the accurate compression and bending endpoints. In comparison to the American and Australian specifications, the Eurocode resulted in more precise results in predicting residual failure loads of compact (Class 1 and 2) sections, owing to the accurate compression and bending endpoints as well as the nonlinear design interaction curve.

Numerical study of low‐rise composite steel frame responses to blast loading using direct simulation method

AbstractThis paper investigated the blast behavior of a low‐rise composite steel structure of three stories subjected to internal and external explosions for the same explosive charge of 250 kg TNT. A comparison of three various blast scenarios is aimed at better understanding how blast waves propagate in confined risk zones and their damage effects on far and exposed elements to an explosive charge. Evaluation of the damage level and the overall response of the proposed numerical model is done by estimating the adequacy of structural members subjected to blast loading using general limits in attempting to check the structure's strength and regularity. The analysis was based on load combinations and damage criteria according to the Unified Facilities Criteria which are general design approaches suitable for civil design applications in forecasting blast loads and structural system responses. The overall behavior of this structure was simulated based on a dynamic analysis by the direct simulation approach, which was chosen for modeling blast loads using the Friedlander blast load equation, and the simpler, less expensive, more accurate, and realistic A.T.‐BLAST model to deduce the simplified blast‐wave overpressure profile. The material nonlinearity at a high strain rate using the Johnson‐Cook strength and concrete plasticity damage model is studied dynamically using ABAQUS finite element code to simulate the explicit dynamic nonlinear analysis. The overall response of the proposed numerical model was evaluated by estimating the adequacy of structural members, considering the blast load as the initial cause of failure, such as axial plastic strain, internal forces limits, maximum deformation, support rotation, demand‐capacity‐ratio (DCRshear/moment), drift index and material damage model. The position of the explosive charge played an important role in determining the rate at which the structural element begins to plastic strains, displacements, moments, or rotations beyond the limits, and then key elements should be considered in structural design against progressive collapse. Results showed that steel members exhibit early indicators of failure, such as buckling necking, shear tearing, or plastic hinges, whereas concrete slabs break up immediately due to brittleness. DCRmoment values successfully showed the columns in which the first plastic joint can occur, whereas DCRshear values signaled the onset of shear failure at connections. Besides, plastic hinges played an important role in dissipating energy and preventing total structural collapse via the Strong Column‐Weak Beam design concept, which appears repeatedly in this study. The structure is a well‐designed and ductile building capable of supporting higher loads and is considered to be repairable and intact.

Flexible Graphene Film-Based Antenna Sensor for Large Strain Monitoring of Steel Structures.

In the field of wireless strain monitoring, it is difficult for the traditional metal-made antenna sensor to conform well with steel structures and monitor large strain deformation. To solve this problem, this study proposes a flexible antenna strain sensor based on a ductile graphene film, which features a 6.7% elongation at break and flexibility due to the microscopic wrinkle structure and layered stacking structure of the graphene film. Because of the use of eccentric embedding in the feeding form, the sensor can be miniaturized and can simultaneously monitor strain in two directions. The sensing mechanism of the antenna is analyzed using a void model, and an antenna is designed based on operating frequencies of 3 GHz and 3.5 GHz. The embedding size is optimized using a Smith chart and impedance matching principle. Both the simulation and experimental results verify that the resonant frequency and strain magnitude are linearly inversely proportional. The experimental results show that the strain sensitivity is 1.752 kHz/με along the geometric length and 1.780 kHz/με along the width, with correlation coefficients of 0.99173 and 0.99295, respectively.

Preparation of bio-based trinity lignin intumescent flame retardant and its effect on burning behavior and heat transfer process of epoxy resin composites

The thermal insulation performance of intumescent coating coated on the surface of steel structure is of great significance to prevent the underlying steel structure from collapse in fire. Bio-based intumescent flame retardants gradually attract many attentions due to its environmental friendliness and rich natural sources. In this study, a new bio-based intumescent flame retardant trinity lignin intumescent flame retardant (TLI) is synthesized, which is added to epoxy resin (EP) to prepare EP/TLI epoxy intumescent coatings. The burning behavior of EP/TLI epoxy intumescent coatings is investigated by thermogravimetric (TG) analysis, limit oxygen index (LOI), vertical burning test and cone calorimeter test. Microscopic morphology of char layer is observed by scanning electron microscopy (SEM). The results show that when the TLI addition content is 20 wt% (EP/TLI-4), LOI reaches 26.5 %, UL-94 is V-0 rating. Compared to pure EP, the peak heat release rate (pHRR) and total heat release (THR) of EP/TLI-4 coating are reduced by 82.20 % and 78.27 %, respectively. The influence of chemical formulations, initial coating thickness and incident heat flux on heat transfer process of EP/TLI epoxy intumescent coatings is also investigated. At the same time, the thermal insulation mechanism of EP/TLI epoxy intumescent coating is presented.

Flexible Graphene Film-Based Antenna Sensor for Large Strain Monitoring of Steel Structures

In the field of wireless strain monitoring, it is difficult for the traditional metal-made antenna sensor to conform well with steel structures and monitor large strain deformation. To solve this problem, this study proposes a flexible antenna strain sensor based on a ductile graphene film, which features a 6.7% elongation at break and flexibility due to the microscopic wrinkle structure and layered stacking structure of the graphene film. Because of the use of eccentric embedding in the feeding form, the sensor can be miniaturized and can simultaneously monitor strain in two directions. The sensing mechanism of the antenna is analyzed using a void model, and an antenna is designed based on operating frequencies of 3 GHz and 3.5 GHz. The embedding size is optimized using a Smith chart and impedance matching principle. Both the simulation and experimental results verify that the resonant frequency and strain magnitude are linearly inversely proportional. The experimental results show that the strain sensitivity is 1.752 kHz/με along the geometric length and 1.780 kHz/με along the width, with correlation coefficients of 0.99173 and 0.99295, respectively.

Embodied impacts of key materials for UK decarbonised domestic retrofit: Differences between sources of embodied carbon and embodied energy data

Low energy domestic retrofit consumes materials, such as insulation, membranes and glazing, with smaller quantities of structural timber, steel or concrete, which have associated embodied impacts from resource extraction, manufacture and end-of-life treatments. In retrofit design, coefficients for material embodied impacts vary widely between sources and can lead to different results in a life cycle energy or carbon analysis, and perhaps different material choices in retrofit implementation. This paper considers how and why results differ between sources, and whether such data is suitable for making climate-beneficial design decisions. Embodied energy and carbon coefficients for 18 key retrofit materials were obtained from two widely used LCA databases and their similarity was quantified. The data collected illustrates that 70% embodied energy and embodied carbon data is within 20%, but that 30% of data was more than 20% different. Consistency of product naming and the absence in the datasets of key retrofit materials are factors identified contributing to variation, and present real constraints in practice. Furthermore, this exercise showed that embodied impacts for the types of materials most prominent in retrofits are less-well characterised than other major construction materials, and presents another layer of uncertainty. The data showed embodied energy was more consistent between sources than embodied carbon. This raises doubts about the predominant use of embodied carbon over energy for such analyses and establishes that a focus on embodied carbon over embodied energy has less power to reduce greenhouse gas emissions than considering both metrics together. It is concluded that obtaining such data with confidence is challenging and requires expertise in LCA, and is therefore unlikely to be accessible to most retrofit designers. Datasets need to be more complete and offer higher confidence to ensure delivery of high quality and meaningful results for climate-beneficial design decisions.