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Advances in Structural Steel Research
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Advances in Structural Steel Research

A special issue of Metals (ISSN 2075-4701).

Deadline for manuscript submissions: closed (31 May 2020) | Viewed by 95224

Special Issue Editors

Dr. Ravi Kiran Yellavajjala

E-Mail Website
Guest Editor
Civil & Environmental Engineering, North Dakota State University, CIE201E, 1410 North 14th Avenue, Fargo, ND 58105, USA
Interests: pathfinding algorithms; reinforcement learning; explainable AI; sensitivity analysis; machine vision
Special Issues, Collections and Topics in MDPI journals
Dr. Hussam Mahmoud

E-Mail Website
Guest Editor
Civil & Environmental Engineering, Colorado State University, 1372 Campus Delivery, Fort Collins, CO 80523, USA
Interests: extreme events, multi-hazard response, life-cylce analysis, resilient infrastructure, fatigue, fracture, deteroration and repair, fire in steel structures
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

More than 50% of the steel produced in the world is used by the construction industry alone. Steel consumption by the construction industry is found to be strongly correlated with economic growth in both developing and developed countries. Structural steel is cheap, abundantly available, and has the highest strength-to-weight ratio among mass-produced construction materials. Theoretically, structural steel is 100% recyclable, and in fact about 90% of the structural steel produced in the United States is recovered from steel scrap. Steel structures have a long life and low life-cycle costs. Besides this, steel structures are adaptable to future needs and provide ample architectural and structural freedom to architects and design engineers.

Despite these advantages, there remain many challenges associated with making steel infrastructure robust, resilient, and sustainable. The main aim of this Special Issue is to rapidly disseminate state-of-the-art fundamental and applied research that will have a positive impact on the design, analysis, erection, and maintenance of steel infrastructure (buildings, bridges, transmission towers, offshore structures, and steel pipelines, among others).

Topics of interest include but are not limited to the following:

Area-1: Steel Structures

  • Performance-based design or analysis criteria
  • Life-cycle cost assessment and optimization
  • Modeling of steel structures subjected to single or multiple hazards
  • Innovative structural steel systems
  • Novel connections and fastening systems
  • Innovative design solutions for complex steel infrastructure challenges
  • Design and assessment issues with high-rise buildings, off-shore structures, transmission towers, and pipelines
  • Improving the sustainability of steel infrastructure
  • Data science in steel infrastructure (inclusive of structural health monitoring)
  • Frame optimization and sensitivity analysis
  • Topology optimization of structural members and connections

Area-2: Structural Steels

  • The mechanical behavior of structural steels under blast, corrosion, fracture, fatigue, and fire
  • Constitutive modeling of structural steels subjected to blast, corrosion, fracture, fatigue, and fire
  • Applications of shape memory alloys and multiphase steels in construction
  • Additive manufactured steels for construction
  • Stainless steels for construction
  • The influence of nano- and microscale steel properties on the behavior of steel structures
  • The design of new steel microstructures for enhanced mechanical performance

Any other topic closely related to steel infrastructure will be considered for publication.

Assist. Prof. Ravi Kiran Yellavajjala
Assoc. Prof. Hussam Mahmoud
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Metals is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Collapse
  • Structural steel systems
  • Structural health monitoring
  • Connections
  • Instability
  • Sensitivity and optimization
  • Fracture
  • Corrosion
  • Shape memory alloys
  • Ultra-high strength steels

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Further information on MDPI's Special Issue polices can be found here.

Published Papers (19 papers)

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Research

29 pages, 14081 KiB  
Article
New Metallic Damper with Multiphase Behavior for Seismic Protection of Structures
by Amadeo Benavent-Climent, David Escolano-Margarit, Julio Arcos-Espada and Hermes Ponce-Parra
Metals 2021, 11(2), 183; https://doi.org/10.3390/met11020183 - 20 Jan 2021
Cited by 11 | Viewed by 2918
Abstract
This paper proposes a new metallic damper based on the plastic deformation of mild steel. It is intended to function as an energy dissipation device in structures subjected to severe or extreme earthquakes. The damper possesses a gap mechanism that prevents high-cycle fatigue [...] Read more.
This paper proposes a new metallic damper based on the plastic deformation of mild steel. It is intended to function as an energy dissipation device in structures subjected to severe or extreme earthquakes. The damper possesses a gap mechanism that prevents high-cycle fatigue damage under wind loads. Furthermore, subjected to large deformations, the damper presents a reserve of strength and energy dissipation capacity that can be mobilized in the event of extreme ground motions. An extensive experimental investigation was conducted, including static cyclic tests of the damper isolated from the structure, and dynamic shake-table tests of the dampers installed in a reinforced concrete structure. Four phases are distinguished in the response. Based on the results of the tests, a hysteretic model for predicting the force-displacement curve of the damper under arbitrary cyclic loadings is presented. The model accurately captures the increment of stiffness and strength under very large deformations. The ultimate energy dissipation capacity of the damper is found to differ depending on the phase in which it fails, and new equations are proposed for its prediction. It is concluded that the damper has a stable hysteretic response, and that the cyclic behavior, the ultimate energy dissipation capacity and failure are highly predictable with a relatively simple numerical model. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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22 pages, 8652 KiB  
Article
Numerical Study on Seismic Response of Steel Storage Racks with Roller Type Isolator
by Oscar Álvarez, Nelson Maureira, Eduardo Nuñez, Frank Sanhueza and Ángel Roco-Videla
Metals 2021, 11(1), 158; https://doi.org/10.3390/met11010158 - 16 Jan 2021
Cited by 4 | Viewed by 3832
Abstract
This research evaluates the effectiveness of using a roller-type base isolation device with tensile strength in reducing the dynamic response of industrial steel storage racks. These were subjected to a seismic input acting separately in both directions of the structure. The seismic record [...] Read more.
This research evaluates the effectiveness of using a roller-type base isolation device with tensile strength in reducing the dynamic response of industrial steel storage racks. These were subjected to a seismic input acting separately in both directions of the structure. The seismic record obtained from the earthquake that occurred in Llolleo, Chile, on 3 March 1985, was used as input. This earthquake was scaled in the frequency domain, adjusting its response spectrum to coincide with the design spectrum required by NCh2745. In the calculations of this spectrum, the most hazardous seismic zone (zone 3) and soft soil (soil III) that amplifies the effect of the low frequencies of the earthquake were considered. These frequencies are the ones that have the most affect on flexible structures such as high racks and systems with base isolation. Numerical time-history analyses were performed in fixed base racks and base isolation racks. In both cases, the models include semi-rigid connections with capacity for plastic deformation and energy dissipation. Parametric analyses were carried out considering the most relevant variables, using an algorithm programmed in MATLAB software. The maximum relative displacement, maximum basal shear load, and maximum absolute floor acceleration were considered as responses of interest. The results showed the effectiveness of using the base isolation device by reducing the absolute accelerations between approximately 75% and 90%, compared to the same fixed rack at its base. This makes it possible to reduce the vulnerability of the stored load to overturn under the action of a severe earthquake. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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25 pages, 13662 KiB  
Article
Cyclic Behavior of Hollow Section Beam–Column Moment Connection: Experimental and Numerical Study
by Eduardo Nuñez, Nwar Boainy, Freddy González, Ronald Torres, Ricardo Picón and Néstor Guerrero
Metals 2020, 10(12), 1608; https://doi.org/10.3390/met10121608 - 30 Nov 2020
Cited by 5 | Viewed by 10058
Abstract
Steel buildings with tubular columns showed a satisfactory performance during the Honshu (2011) earthquake, unlike steel buildings in the 1994 Northridge and 1995 Kobe earthquakes, where welded moment connections showed damage in their joints. In this research, a lateral joint using a hollow [...] Read more.
Steel buildings with tubular columns showed a satisfactory performance during the Honshu (2011) earthquake, unlike steel buildings in the 1994 Northridge and 1995 Kobe earthquakes, where welded moment connections showed damage in their joints. In this research, a lateral joint using a hollow structural section (HSS)-beam and HSS-column subjected to cyclic displacement was performed. Three large-scale specimens were tested and a numerical model was calibrated, reaching a good adjustment. Later, several configurations of beams and columns were evaluated using finite element (FE) models from the numerical model previously calibrated. A flexural resistance higher 0.80 Mp at 0.04 [rad] was obtained for all cases studied. The ductility factor in the 3 specimens was lower than 2.5, therefore a non-ductile behavior was controlled in the connection. This aspect is very important although a 0.8 Mp at 0.04 [rad] was achieved. Finally, the typical welded moment connection can be improved using the bolted moment connection, which allows the concentration of inelastic incursion in the beam compared with the welded solution. However, a non-ductile behavior derived from local buckling in flanges of a tubular beam can affect the seismic performance. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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25 pages, 11010 KiB  
Article
Cyclic Performance of End-Plate Biaxial Moment Connection with HSS Columns
by Eduardo Nuñez, Roberto Lichtemberg and Ricardo Herrera
Metals 2020, 10(11), 1556; https://doi.org/10.3390/met10111556 - 23 Nov 2020
Cited by 7 | Viewed by 4891
Abstract
This paper presents a numerical study on the seismic performance of end-plate moment connection between I-beam to HSS (hollow structural section) column stiffened by outer diaphragms (EP-HSS). In previous experimental research, this moment connection showed a satisfactory performance according to requirements established in [...] Read more.
This paper presents a numerical study on the seismic performance of end-plate moment connection between I-beam to HSS (hollow structural section) column stiffened by outer diaphragms (EP-HSS). In previous experimental research, this moment connection showed a satisfactory performance according to requirements established in Seismic provisions. However, one type of joint was studied and bidirectional and axial loads were not considered. In this since, several configurations representative of 2D interior joints and 3D interior and exterior joints in a steel building were modeled and subjected to unidirectional or bidirectional cyclic displacements according to protocol in seismic provisions. Firstly, a similar joint configuration was calibrated from experimental data, obtaining an acceptable adjustment. The assessment of seismic performance was based on hysteretic curves, failure mechanisms, stiffness, dissipated energy, and equivalent damping. The results obtained showed a ductile failure modes for 2D and 3D joint configurations with EP-HSS moment connection. The axial load has no significant effect on the moment connection. However, it affects the column strength due to the increase of the stresses in the column wall. Compared with 2D joints, 3D joints reached higher deformations even when a similar number of beams is used. The external diaphragms to the column panel zone provided rigidity in the joints and no degradation of slope for each loop in load/reload segment for elastic loop; therefore, curves without pinching were observed. All inelastic deformation is concentrated mainly in the beams. A moment resistance above 80% of the capacity of the beam at a drift of 4% is achieved in all joints. From the results reached, the use of EP-HSS moment connection with hollow structural section columns is a reliable alternative in seismic zones when steel moment frames are employed. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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19 pages, 7135 KiB  
Article
Detection of Corrosion-Indicating Oxidation Product Colors in Steel Bridges under Varying Illuminations, Shadows, and Wetting Conditions
by Dayakar L. Naik, Hizb Ullah Sajid, Ravi Kiran and Genda Chen
Metals 2020, 10(11), 1439; https://doi.org/10.3390/met10111439 - 29 Oct 2020
Cited by 13 | Viewed by 6176
Abstract
Early detection of corrosion in steel bridges is essential for strategizing the mitigation of further corrosion damage. Although various image-based approaches are available in the literature for corrosion detection, most of these approaches are tested on images acquired under uniform natural daylight illuminations [...] Read more.
Early detection of corrosion in steel bridges is essential for strategizing the mitigation of further corrosion damage. Although various image-based approaches are available in the literature for corrosion detection, most of these approaches are tested on images acquired under uniform natural daylight illuminations i.e., inherent variations in the ambient lighting conditions are ignored. Owing to the fact that varying natural daylight illuminations, shadows, water wetting, and oil wetting are unavoidable in real-world scenarios, it is important to devise a robust technique for corrosion identification. In the current study, four different color spaces namely ‘RGB’, ‘rgb’, ‘HSV’ and ‘CIE La*b*’ along with a multi-layer perceptron (MLP) is configured and trained for detecting corrosion under above-mentioned real-world illumination scenarios. Training (5000 instances) and validation (2064 instances) datasets for this purpose are generated from the images of corroded steel plates acquired in the laboratory under varying illuminations and shadows, respectively. Each combination of color space and an MLP configuration is individually assessed and the best suitable combination that yields the highest ‘Recall’ value is determined. An MLP configuration with a single hidden layer consisting of 4 neurons (1st Hidden Layer (HL)(4N)) in conjunction with ‘rgb’ color space is found to yield the highest ‘Accuracy’ and ‘Recall’ (up to 91% and 82% respectively). The efficacy of the trained MLP to detect corrosion is then demonstrated on the test image database consisting of both lab-generated partially corroded steel plate images and field-generated images of a bridge located in Moorhead (Minnesota). Lab-generated images used for testing are acquired under varying illuminations, shadows, water wetting, and oil wetting conditions. Based on the validation studies, ‘rgb’ color space and an MLP configuration consisting of single hidden layer with 4 neurons (1st HL(4N)) trained on lab-generated corroded plate images identified corrosion in the steel bridge under ambient lighting conditions. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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20 pages, 11386 KiB  
Article
Design Contributions to the Elaboration of New Modeling Schemes for the Buckling Assessment of Hydraulic Actuators
by Virgil Florescu, Stefan Mocanu, Laurenţiu Rece, Daniel Cătălin Motounu, Aurel Gherghina and Adrian Burlacu
Metals 2020, 10(9), 1143; https://doi.org/10.3390/met10091143 - 24 Aug 2020
Cited by 5 | Viewed by 2874
Abstract
Hydraulic cylinders represent the main actuating/positioning element for standalone lifting equipment or equipment for various transport platforms. This type of actuator represents a structural component responsible for the operational safety of the equipment it serves. One of the most common and dangerous reasons [...] Read more.
Hydraulic cylinders represent the main actuating/positioning element for standalone lifting equipment or equipment for various transport platforms. This type of actuator represents a structural component responsible for the operational safety of the equipment it serves. One of the most common and dangerous reasons concerning the end of life for this equipment is the buckling or loss of stability of the elastic equilibrium shape. This article aims to compare the classical approach of the problem in accordance with the strength of materials theory in relation to the numeric algorithms used in the applications for the analysis of structure behavior and the algorithms that are based on the finite element method. The subject of study is a hydraulic cylinder that is installed in a self-lifting platform and because of the manifestation of the phenomenon under analysis, it has led to a technical accident. For this purpose, an estimation of the value for the buckling critical load of the cylinder assembly was carried out. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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18 pages, 7716 KiB  
Article
Bidirectional Response of Weak-Axis End-plate Moment Connections: Numerical Approach
by Eduardo Nuñez, Guillermo Parraguez and Ricardo Herrera
Metals 2020, 10(7), 964; https://doi.org/10.3390/met10070964 - 17 Jul 2020
Cited by 6 | Viewed by 6214
Abstract
Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations [...] Read more.
Brittle failure mechanisms can affect the seismic performance of structures composed of intersecting moment resisting frames, if the biaxial effects are not considered. In this research, the bidirectional cyclic response of H-columns with weak-axis moment connections was studied using numerical models. Several configurations of joints with bidirectional effects and variable axial loads were studied using the finite element method (FEM) in ANSYS v17.2 software. The results obtained showed a ductile behavior when cyclic loads are applied. No evidence of brittle failure mechanisms in the studied joint configurations was observed, in line with the design philosophy established in current seismic provisions. However, beams connected to the column minor axis reached a partially restrained behavior. Joints with four beams connected to the column exhibited a partially restrained behavior for all axial load levels. An equivalent force displacement method was used to compare the hysteretic response of 2D and 3D joints, obtaining higher deformations in 3D joints with respect to 2D joints with a similar number of connected beams. Consequently, design procedures are not capable of capturing the 3D deformation phenomenon. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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21 pages, 17535 KiB  
Article
Assessment of the Seismic Behavior of Selective Storage Racks Subjected to Chilean Earthquakes
by Eduardo Nuñez, Catalina Aguayo and Ricardo Herrera
Metals 2020, 10(7), 855; https://doi.org/10.3390/met10070855 - 28 Jun 2020
Cited by 6 | Viewed by 4076
Abstract
A seismic performance evaluation of selective storage racks subjected to Chilean Earthquakes was conducted using nonlinear pushover and nonlinear dynamic time-history analyses. Nine seismic records with two horizontal components and magnitude Mw > 7.7 were applied to numerical models of prototype rack structures. [...] Read more.
A seismic performance evaluation of selective storage racks subjected to Chilean Earthquakes was conducted using nonlinear pushover and nonlinear dynamic time-history analyses. Nine seismic records with two horizontal components and magnitude Mw > 7.7 were applied to numerical models of prototype rack structures. The prototype racks were designed considering two types of soil and two aspect ratios. The inelastic behavior of beam connections was included in the models. The results showed a predominantly elastic behavior, mainly in the cross-aisle direction, in comparison to the down-aisle direction. The inelastic action was concentrated in pallet beams and up-rigths. Higher values of base shear were reached, due to elevated rigidity in rack configurations, and an acceptable performance was obtained. A response reduction factor was reported in both directions, reaching values larger than the limit imposed by the Chilean standard. However, values below this limit were obtained in the cross-aisle direction, in some cases. Finally, in all cases, the calculated response modification factor is highly influenced by the overstrength obtained from seismic design. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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14 pages, 6209 KiB  
Article
Effect of Warm Rolling Temperature on the Microstructure and Texture of Microcarbon Dual-Phase (DP) Steel
by Qiangqiang Yuan, Zhigang Wang, Yinghui Zhang, Jieyun Ye, Yao Huang and Ankang Huang
Metals 2020, 10(5), 566; https://doi.org/10.3390/met10050566 - 27 Apr 2020
Cited by 9 | Viewed by 2739
Abstract
The effect of warm rolling temperature on microstructure and texture of microcarbon dual-phase (DP) steel was investigated through scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results showed that with the increase of rolling temperature, the density [...] Read more.
The effect of warm rolling temperature on microstructure and texture of microcarbon dual-phase (DP) steel was investigated through scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). The results showed that with the increase of rolling temperature, the density and thickness of the deformation band first increased and then decreased. Ferrite and fine martensite were observed in the annealed sheet, and the ferrite had a much more homogeneous distribution in the sample rolled at 450 °C. During warm rolling, the ferrite developed a dominant γ-fiber and a weak α-texture. During the annealing of the rolled sheet, the intensity of the γ-fiber was increased and a weak {001}<100> texture developed in the sample rolled at room temperature. An increase in the rolling temperature generated an initial decrease and subsequent increase in the strength of the unfavorable {001}<110> texture in the annealed sheet. In addition, the strength reached a maximum at 550 °C due to an increase in the dissolved carbon in the matrix, which was result of carbide dissolution. By contrast, the intensity of the γ-fiber remained relatively higher and was deemed the weaker {001}<110> component in the annealed sheet rolled at 450 °C. Therefore, a larger texture factor (fγ-fiber/f(α-fiber+λ-fiber)) can be produced under this process. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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12 pages, 4645 KiB  
Article
In-Situ Observation of Lüders Band Formation in Hot-Rolled Steel via Digital Image Correlation
by Hai Qiu, Tadanobu Inoue and Rintaro Ueji
Metals 2020, 10(4), 530; https://doi.org/10.3390/met10040530 - 20 Apr 2020
Cited by 13 | Viewed by 4940
Abstract
Although the Lüders yield phenomenon has been investigated for more than 150 years, some understanding of Lüders band formation lack substantial support from experimental evidence. In-situ observation of Lüders band formation in hot-rolled steel experimentally clarified the following facts: (i) When stress reaches [...] Read more.
Although the Lüders yield phenomenon has been investigated for more than 150 years, some understanding of Lüders band formation lack substantial support from experimental evidence. In-situ observation of Lüders band formation in hot-rolled steel experimentally clarified the following facts: (i) When stress reaches the true upper yield stress, the Lüders band begins to nucleate. True upper yield stress is greater than nominal upper yield stress. (ii) Gross stress concentration promotes the Lüders band formation, and the size of the gross stress concentration region determines the initial width of the Lüders band. (iii) The Lüders band nucleates far ahead of the gross yield point. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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28 pages, 16893 KiB  
Article
Numerical Study on Cyclic Response of End-Plate Biaxial Moment Connection in Box Columns
by Marco Gallegos, Eduardo Nuñez and Ricardo Herrera
Metals 2020, 10(4), 523; https://doi.org/10.3390/met10040523 - 18 Apr 2020
Cited by 19 | Viewed by 4780
Abstract
The 2008 Wenchuan-China earthquake showed the importance of considering the bidirectional seismic action as a cause of failure in column hinge mechanisms. Subsequently, the large 2011 Tohoku-Japan earthquake revealed that Special Moment Frames buildings, made of tubular columns (Hollow Structural Section or Built-up [...] Read more.
The 2008 Wenchuan-China earthquake showed the importance of considering the bidirectional seismic action as a cause of failure in column hinge mechanisms. Subsequently, the large 2011 Tohoku-Japan earthquake revealed that Special Moment Frames buildings, made of tubular columns (Hollow Structural Section or Built-up Box Section) and rigid connections with I-beams, did not suffer serious damage. However, only the ConXtech® ConXL™ moment connection has been prequalified according to the (American Institute of Construction) AISC Seismic Provisions for use with tubular columns and the rest of connections do not consider biaxial resistance. The research reported herein investigated the cyclic response of box-columns joints, connected to I beams using the four-bolt extended endplate connection, subjected to bidirectional bending and axial load on the column. To conduct the study, complex nonlinear finite element models (FEMs) of several I beam to box column joint configurations were constructed and analyzed under cyclic loading using the ANSYS software. The results reveal that the failure is concentrated in the beams of all joint configurations except for the columns with axial load equal to 75% of the column capacity, where a combined failure mechanism is achieved. The energy dissipation capacity of joints with a greater number of beams is lower than joints with fewer beams. The bidirectional effect of the seismic action and the level of axial load must be considered to avoid the formation of a column-hinge fragile failure mechanism also the behavior exhibited by 3D joints is more realistic than 2D joints according to real structures. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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19 pages, 17675 KiB  
Article
Monotonic Response of Exposed Base Plates of Columns: Numerical Study and a New Design Method
by Héctor Díaz, Eduardo Nuñez and Claudio Oyarzo-Vera
Metals 2020, 10(3), 396; https://doi.org/10.3390/met10030396 - 19 Mar 2020
Cited by 5 | Viewed by 10356
Abstract
This paper describes a numerical study of the behavior of exposed base plates of columns under the action of axial and bending loads. The aim of this research is to evaluate numerically the failure mechanisms on stiffened and non-stiffened base plates and propose [...] Read more.
This paper describes a numerical study of the behavior of exposed base plates of columns under the action of axial and bending loads. The aim of this research is to evaluate numerically the failure mechanisms on stiffened and non-stiffened base plates and propose a new design method. The effects of base plate thickness, location of anchor rods, location of stiffeners and tensile strength of anchor rods were considered in the analysis. Sixteen finite elements simulations were performed considering different combinations of the above mentioned parameters. The results show a fragile response in the base plates when high resistance anchor rods are used. The anchor rods worked as fuse elements in base plates with a large thickness or many stiffeners. Additionally, the models with anchor bars located outside of the column flanges showed lower flexural strength and rotational stiffness compared to the models with anchor rods located between column flanges. The simulations showed that the base plate strength was determined by the simultaneous failure mechanisms of two or more components, different to what is stated in current design guides. Finally, the new method is suitable to design base plates with stiffened and not stiffened configurations, which unlike traditional design methods, show a good adjustment with numerical models. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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16 pages, 6136 KiB  
Article
Effects of Cross-Section Type and Degree of Utilization on Failure Time and Temperature of Cold-Formed Steel Column under ISO Fire
by Fadhluhartini Muftah, Mohd Syahrul Hisyam Mohd Sani and Shahrin Mohammad
Metals 2019, 9(9), 964; https://doi.org/10.3390/met9090964 - 2 Sep 2019
Cited by 1 | Viewed by 2803
Abstract
An investigation into fire resistance subjected to the ISO fire standard was conducted on a cold-formed steel (CFS) column. The variables involved were the CFS sections with various cross-section types and service loadings known as the degree of utilization. Three types of cross-section, [...] Read more.
An investigation into fire resistance subjected to the ISO fire standard was conducted on a cold-formed steel (CFS) column. The variables involved were the CFS sections with various cross-section types and service loadings known as the degree of utilization. Three types of cross-section, known as channel, back-to-back (BTB), and box-up (BU) sections, were studied. All supports for the column are in constant condition. To simulate the real fire situation, the column was preloaded at 30%, 50%, and 70% of its ultimate strength. After the load was static, the column was exposed to the ISO fire standard. The column was loaded at the centroid of the section. The temperature at the column surface and the time was recorded until the column became unstable. The results show that the shape did not have any significant effects on the critical temperature of the CFS columns. The higher the applied load—or as used in this study, the higher the degree of utilization of the CFS columns—the greater the negative linear effect on their critical temperature. It is concluded that the minimum limiting temperature is 400 °C and the minimum limiting time is four minutes for the CFS column. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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11 pages, 3198 KiB  
Article
Continuous Cooling Transformation Diagram, Microstructures, and Properties of the Simulated Coarse-Grain Heat-Affected Zone in a Low-Carbon Bainite E550 Steel
by Yun Zong and Chun-Ming Liu
Metals 2019, 9(9), 939; https://doi.org/10.3390/met9090939 - 27 Aug 2019
Cited by 12 | Viewed by 3940
Abstract
In order to provide important guidance for controlling and obtaining the optimal microstructures and mechanical properties of a welded joint, the continuous cooling transformation diagram of a new low-carbon Nb-microalloyed bainite E550 steel in a simulated coarse-grain heat-affected zone (CGHAZ) has been constructed [...] Read more.
In order to provide important guidance for controlling and obtaining the optimal microstructures and mechanical properties of a welded joint, the continuous cooling transformation diagram of a new low-carbon Nb-microalloyed bainite E550 steel in a simulated coarse-grain heat-affected zone (CGHAZ) has been constructed by thermal dilatation method in this paper. The welding thermal simulation experiments were conducted on a Gleeble-3800 thermo-mechanical simulator. The corresponding microstructure was observed by a LEICA DM2700M. The Vickers hardness (HV) and the impact toughness at −40 °C were measured according to the ASTM E384 standard and the ASTM E2298 standard, respectively. The experimental results may indicate that the intermediate temperature phase transformation of the whole bainite can occur in a wide range of cooling rates of 2–20 °C/s. In the scope of cooling rates 2–20 °C/s, the microstructure of the heat-affected zone (HAZ) mainly consists of lath bainite and granular bainite. Moreover, the proportion of lath bainite increased and granular bainite decreased as the cooling rate increasing. There is a spot of lath martensite in the microstructure of HAZ when the cooling rate is above 20 °C/s. The Vickers hardness increases gradually with the increasing of the cooling rate, and the maximum hardness is 323 HV10. When the cooling time from 800 °C to 500 °C (t8/5) is 5–15 s, it presents excellent −40 °C impact toughness (273–286 J) of the CGHAZ beyond the base material (163 J). Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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18 pages, 20820 KiB  
Article
Study on Microstructure and Properties of a New Warm-Stamped Niobium-Alloyed Steel
by Peng Tian, Wen Liang, Zhennan Cui, Guoming Zhu, Yonglin Kang, Baoshun Li, Li Lin and Rendong Liu
Metals 2019, 9(7), 765; https://doi.org/10.3390/met9070765 - 8 Jul 2019
Cited by 1 | Viewed by 3066
Abstract
The warm stamping technology is a promising technology to meet the needs of car weight reduction and energy conservation. In order to compare with the mechanical properties of the traditional hot-stamped boron-alloyed steel 22MnB5, a new warm-stamped niobium-alloyed steel 22Mn3SiNb was designed and [...] Read more.
The warm stamping technology is a promising technology to meet the needs of car weight reduction and energy conservation. In order to compare with the mechanical properties of the traditional hot-stamped boron-alloyed steel 22MnB5, a new warm-stamped niobium-alloyed steel 22Mn3SiNb was designed and tested. The optimal heating parameters for warm forming process were explored through mechanical tests, and the process of their microstructure evolution was investigated by scanning electron microscope (SEM), transmission electron microscope (TEM) and X-ray diffraction (XRD), etc. The experimental results indicate that the optimal heating parameters for the niobium-alloyed steel 22Mn3SiNb are a heating temperature of 800 °C and a soaking time of 5 min. Compared to the hot-stamped boron-alloyed steel 22MnB5 under their respective optimal heating parameters, the properties and microstructure characteristics of 22Mn3SiNb are greatly improved, and nearly no decarburized layer is found on the surface of the niobium-alloyed steel 22Mn3SiNb. In addition, the addition of Nb produces the effects of grain refinement and precipitation strengthening due to the introduction of plenty of nano-precipitated particles and dislocations. In the end, it can be predicted that the new warm-stamped niobium-alloyed steel will replace the conventional hot-stamped boron-alloyed steel. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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18 pages, 4677 KiB  
Article
A New Method for Internal Force Detection of Steel Bars Covered by Concrete Based on the Metal Magnetic Memory Effect
by Caoyuan Pang, Jianting Zhou, Qingyuan Zhao, Ruiqiang Zhao, Zhuo Chen and Yi Zhou
Metals 2019, 9(6), 661; https://doi.org/10.3390/met9060661 - 6 Jun 2019
Cited by 12 | Viewed by 3418
Abstract
In this paper, the specimens of steel bars covered by concrete (SBCC) are taken as research objects, and a new method for steel bar internal force detection based on the metal magnetic memory effect is proposed. The variation law of the self-magnetic flux [...] Read more.
In this paper, the specimens of steel bars covered by concrete (SBCC) are taken as research objects, and a new method for steel bar internal force detection based on the metal magnetic memory effect is proposed. The variation law of the self-magnetic flux leakage (SMFL) signals on the surfaces of SBCC specimens with loading tension and the variation of the SMFL signals along the axial positions of specimens under different tensile forces are studied. The results show that when the loading tension is about 90% of the yield tension, the tangential component of the SMFL signal has a maximum extreme point. The distribution of the SMFL signals along the axial position shows a smooth curve, where the values at both ends are small while the intermediate values are large. This paper also proposes the use of the “area ratio deviation parameter” to quantitatively calculate the internal forces of the steel bars. This parameter shows a significant linear relationship with the loading tension during the strengthening stage of the specimens. This method can supplement the existing steel bar stress detection methods and has prospective research value. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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26 pages, 4722 KiB  
Article
Texture-Based Metallurgical Phase Identification in Structural Steels: A Supervised Machine Learning Approach
by Dayakar L. Naik, Hizb Ullah Sajid and Ravi Kiran
Metals 2019, 9(5), 546; https://doi.org/10.3390/met9050546 - 10 May 2019
Cited by 36 | Viewed by 6984
Abstract
Automatic identification of metallurgical phases based on thresholding methods in microstructural images may not be possible when the pixel intensities associated with the metallurgical phases overlap and, hence, are indistinguishable. To circumvent this problem, additional visual information about the metallurgical phases, referred to [...] Read more.
Automatic identification of metallurgical phases based on thresholding methods in microstructural images may not be possible when the pixel intensities associated with the metallurgical phases overlap and, hence, are indistinguishable. To circumvent this problem, additional visual information about the metallurgical phases, referred to as textural features, are considered in this study. Mathematically, textural features are the second order statistics of an image domain and can be distinct for each metallurgical phase. Textural features are evaluated from the gray level co-occurrence matrix (GLCM) of each metallurgical phase (ferrite, pearlite, and martensite) present in heat-treated ASTM A36 steels in this study. The dataset of textural features and pixel intensities generated for the metallurgical phases is used to train supervised machine learning classifiers, which are subsequently employed to predict the metallurgical phases in the microstructure. Naïve Bayes (NB), k-nearest neighbor (K-NN), linear discriminant analysis (LDA), and decision tree (DT) classifiers are the four classifiers employed in this study. The performances of all four classifiers were assessed prior to their deployment, and the classification accuracy was found to be >97%. The proposed technique has two unique advantages: (1) unlike pixel intensity-based methods, the proposed method does not misclassify the grain boundaries as a metallurgical phase, and (2) the proposed method does not require the end-user to input the number of phases present in the microstructure. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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9 pages, 3613 KiB  
Article
Correlation between Microstructural Evolution and Mechanical Properties of 2000 MPa Cold-Drawn Pearlitic Steel Wires during Galvanizing Simulated Annealing
by Xiuyu Lu
Metals 2019, 9(3), 326; https://doi.org/10.3390/met9030326 - 14 Mar 2019
Cited by 8 | Viewed by 3432
Abstract
In the present experiment, hot-dip galvanizing simulated annealing of 2000 MPa cold-drawn pearlitic steel wires was carried out at 450 °C. The effects of microstructural evolution on the mechanical properties of the as-prepared wires were analyzed through scanning electron microscopy (SEM), transmission electron [...] Read more.
In the present experiment, hot-dip galvanizing simulated annealing of 2000 MPa cold-drawn pearlitic steel wires was carried out at 450 °C. The effects of microstructural evolution on the mechanical properties of the as-prepared wires were analyzed through scanning electron microscopy (SEM), transmission electron microscopy (TEM), tensile test, torsion test, and Vickers hardness test. In addition, the relationship between torsion laps and microstructural evolution of cold-drawn pearlitic steel wires was investigated in detail. It was found that the torsional performance of the wires deteriorated after annealing at 450 °C for 2–5 min, and the corresponding microstructural evolution was accompanied by the partial degradation of lamellar pearlites due to the diffusion and dislocation pinning of dissolved carbon atoms in ferrites, and it is not feasible to achieve the matching of strength and torsion laps by prolonging the holding time. The deterioration in torsional performance can be attributed to the microstructural difference between the surface and the center of the annealed wires. When the proportion of non-lamellar structure between the surface and the center in each specimen exceeded 8%, the microhardness difference was found to be greater than 40 HV and the torsion lap was less than 3 circles. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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16 pages, 3530 KiB  
Article
Lateral Buckling Theory and Experimental Study on Pipe-in-Pipe Structure
by Zechao Zhang, Hongbo Liu and Zhihua Chen
Metals 2019, 9(2), 185; https://doi.org/10.3390/met9020185 - 4 Feb 2019
Cited by 15 | Viewed by 4055
Abstract
With the increasing depth of marine oil and gas exploitation, more requirements have been proposed on the structure of deep-sea oil pipelines. The influencing factors of lateral buckling of a pipe-in-pipe (PIP) structure containing initial imperfections and its critical force were investigated in [...] Read more.
With the increasing depth of marine oil and gas exploitation, more requirements have been proposed on the structure of deep-sea oil pipelines. The influencing factors of lateral buckling of a pipe-in-pipe (PIP) structure containing initial imperfections and its critical force were investigated in this study by conducting an experiment, a finite element analysis, and a theoretical derivation. The change laws on the influence of initial imperfections of the PIP structure during thermal loading were revealed through an experimental study by using imperfection amplitude and wavelength as parameters. Appropriate finite element models were established, and the influences of initial imperfections, pipe-soil interaction, and the height and the number of centralizers on the global buckling critical force of the PIP structure were analyzed. The formulas of global buckling critical force of inner and outer pipes and that under pipe-soil interaction was obtained by using a theoretical derivation method. A comparative verification with experimental and finite element (FE) models result was conducted, which provided a corresponding basis for steel pipeline design. Full article
(This article belongs to the Special Issue Advances in Structural Steel Research)
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