American Steel Research Articles

Analytical method for distortional buckling load of cold-formed steel members with perforated web under bending moment

In order to reduce weight or meet specific functional requirements, cold-formed steel (CFS) members with perforated webs are widely used in practical engineering. However, these web holes, especially the un-stiffened ones, can result in stress concentrations and section deficiencies, leading to a reduction of the distortional buckling load. Existing specifications, such as the American Iron and Steel Institute (AISI 2016) and Australia New Zealand Standards (AS/NZS 4600:2018), do not fully consider this impact. By simplifying the perforated web into an equivalent beam model and modifying the calculation method of the web rotational stiffness, this paper proposes an analytical method for the distortional buckling load of perforated CFS members with arbitrary hole parameters, including the hole spacing, location, and geometric shape. The proposed method is verified by finite element analysis (FEA) and experiment results in the literature. The FEA result indicates that holes near the compressed flange or with smaller spacing can lead to more reduction in the distortional buckling load. Compared to existing methods, the calculation accuracy of the proposed method has been improved by 2% to 4%.

Investigating Economic Effects of 2018 Steel Tariff Imposition In USA


 In 2018, the Trump administration imposed a 25% tariff on steel imports from a number of countries. The administration justified this action by referring to section 232 of the 1962 Trade Expansion Act, which allows for the imposition of tariffs for ‘national security reasons.’ While the domestic American steel industry applauded the action, the tariffs have been extremely controversial and elicited consternation among countries and industries negatively affected.
 Overall, the tariffs had an initial positive impact on the steel industry, increasing both employment in American steel-producing firms and increasing prices charged for the high-demand commodity. However, this effect was relatively short-lived and was likely not as pronounced as the Trump administration would have preferred. Meanwhile, steel-consuming industries, such as the automobile industry, saw a steep rise in prices, a loss of competitiveness, and a significant drop in employment rates. Given that substantially more labor is employed in the steel-consuming industry as compared to the steel-producing industry, those negatively impacted by the use of tariffs significantly exceeded those who benefitted from them.
 Beyond the direct impacts on steel-producers and steel-consumers, the 2018 tariffs also had the effect of provoking retaliatory tariffs on a variety of American industries, which created to a phenomenon known as ‘cascading protection’ as ever more domestic industries, which experienced a loss of competitiveness as a result of the tariffs, lobbied the administration for the imposition of further tariffs.

Structural behaviour of Cold‐Formed Steel back‐to‐back welded sections subjected to longitudinal shear

AbstractThe current study focuses on understanding the behaviour of flare v‐groove welds on back‐to‐back connected Cold‐Formed Steel welded sections (G300) subjected to longitudinal shear. A novel welding technique called Cold Metal Transfer (CMT) welding was used for fabrication with copper‐coated steel welding wire as a filler metal (ER70S‐6). This mode of welding has the advantage of controlled material deposition compared to the spray or globular mode of welding. Lap shear tests were carried out on unlipped channels including thickness of the weld, and length of the weld. The weld geometry was observed under an optical microscope after polishing and chemical etching of the weld cross‐section, as American Iron and Steel Institute (AISI) design standard provides no specification on thickness of flare v‐groove welds for CMT welding process. In general, the lap shear specimens failed in plate tearing failure mode and brittle fracture of weld at the weld contours. Additionally, the appropriateness of AISI's shear design strength equations for flare v‐groove welds was verified and preliminary design guidelines are provided addressing the lacunae in AISI design standard.

Study on the performance of a novel rotation-amplified brace and its vibration control for a frame structure

A novel rotation-amplified brace (RAB) with higher energy dissipation capacity is proposed based on the bridge amplification working mechanism to solve the problem that traditional displacement-dependent braces are unable to fully perform under low-intensity earthquakes due to their small deformation. First, the basic construction and working mechanism are introduced. Then, a theoretical model is derived that can precisely predict the hysteretic characteristics of the brace and verified by numerical simulation. Additionally, the mechanical properties of the brace under different initial amplifying angles are presented. Finally, its control effect on a rotation-amplified braced frame (RABF) is studied. The numerical simulation results show that the yield-bearing capacity, maximum bearing capacity, initial stiffness and energy dissipation capacity of RAB significantly increase with decreasing initial amplification angle. Meanwhile, a smaller initial amplification angle can bring out a greater plastic deformation area of the energy-dissipation steel tube to improve the energy dissipation capacity. However, it is necessary to ensure that the ratio of the maximum tensile-compressive capacity meets the limit stipulated by the American Steel Structure Association at 1.3. It is especially noteworthy that the maximum reduction ratio of maximum interstory drift is as high as 61% for the RABF structure with braces in an inverted V-shape arrangement, which further verifies the effectiveness of RAB in improving seismic performance.

Weld Effective Lengths for Axially Loaded Transverse Plate-to-CHS Connections

Large-scale experimental tests were conducted to evaluate the strength of partial joint penetration (PJP) groove welds in axially loaded transverse plate-to-circular hollow section (CHS) X-connections. Six connections, comprising 12 joints, were designed to investigate the influence of branch-to-chord width ratio and chord slenderness on weld strength. Nonuniform strain distributions were observed in the branches adjacent to the joints, indicating that the welds were only partially effective. Results from the experimental tests were used to evaluate design guidance for PJP welds in the American steel design standard, AISC 360-16, and a weld effective length equation is proposed for axially loaded plate-to-CHS connections.

Design and optimization of a type-C tank for liquid hydrogen marine transport

As one of the most promising renewable energy sources, hydrogen has the excellent environmental benefit of producing zero emissions. A key technical challenge in using hydrogen across sectors is placed on its storage technology. The storage temperature of liquid hydrogen (20 K, or −253 °C) is close to absolute zero so the storage materials and the insulation layers are subjected to extremely stringent requirements against the cryogenic behaviour of the medium. In this context, this research proposed to design a large liquid hydrogen type-C tank with AISI (American Iron and Steel Institution) type 316 L stainless steel as the metal barrier, using Vapor-Cooled Shield (VCS) and Rigid Polyurethane Foams (RPF) as the insulation layer. A parametric study on the design of the insulation layer was carried out by establishing a thermodynamic model. The effects of VCS location on heat ingress to the liquid hydrogen transport tank and insulation temperature distribution were investigated, and the optimal location of the VCS in the insulation was identified. Research outcomes finally suggest two optimal design schemes: (1) when the thickness of the insulation layer is determined, Self-evaporation Vapor-Cooled Shield (SVCS) and Forced-evaporation Vapor-Cooled Shield (FVCS) can reduce heat transfer by 47.84% and 85.86% respectively; (2) when the liquid hydrogen evaporation capacity is determined, SVCS and FVCS can reduce the thickness of the insulation layer by 50% and 67.93% respectively.

A modified model of Lundberg-Palmgren rolling contact fatigue formula considering the effects of surface treatments

The Lundberg-Palmgren (L-P) fatigue life formula, as a statistical fatigue theory, has been widely used in the industry. However, its direct applicability is limited to the components treated by surface strengthening technologies. Rolling contact fatigue tests and surface integrity measurements of American Iron and Steel Institute (AISI) 9310 rollers with several surface treatments were performed to address this issue. Based on these results, a modified L-P fatigue model was proposed, enabling the consideration of surface modification including surface roughness, residual stress, and hardening introduced by different surface treatments. Compared with the original L-P fatigue formula, its results are more accurate for surface strengthened specimens. Furthermore, this method can assess the contact fatigue life of gears treated by surface strengthening techniques.

Structural behaviour of cold-formed steel T-Stub connections with HRC and screws subjected to tension force

Cold-formed steel (CFS) T-Stub connections are widely used in single-story buildings, and their use is increasing in multi-story and long-span buildings. Recently, an innovative CFS T-Stub connection was developed using self-drilling screws and the Howick Rivet Connector (HRC), and such a newly-developed connection demonstrated excellent structural performance in the building industry. In this paper, a comprehensive experimental and numerical investigation was conducted to investigate the failure mechanism and structural behaviour of CFS T-Stub connections with a combination of HRC and screws under tension force, considering the effects of screw numbers. Firstly, a total of 15 new experimental tests were conducted on the CFS T-Stub connections with various numbers of screws. From the experiments, it was observed that the HRC was subjected to shear failures, while screws failed primarily due to tilting and bearing failures in all investigated specimens. Then, a non-linear elasto-plastic finite element (FE) model was developed and validated against the experimental results in terms of connection strength and failure modes. Finally, the design strengths obtained from the American Iron and Steel Institute (AISI 2016) & Australia/New Zealand standards (AS/NZS 2018) and Ahmadi et al. (2016) were compared with the test and FEA results, showing that the ultimate design strength of CFS T-Stub connections was overestimated by 16% and 14%, respectively. However, for T-Stub connections with HRC alone and with HRC and one screw, these design guidelines were unconservative by 5%.

More accurate design equations for cold-formed steel members subjected to combined axial compressive load and bending

Cold-formed steel (CFS) load-bearing members in multi-storey frame systems are subjected to combined actions sourced from gravity and lateral loads. However, limited information is available on the complex interaction behaviour of such elements affected by different buckling modes. This study aims to provide a better understanding of the behaviour and design of CFS sections under various combinations of compression and bending about both major- and minor-axes. Experimentally validated finite element (FE) models of CFS elements were developed in ABAQUS software, accounting for material nonlinearity and geometric imperfections. The validated models were then used to conduct a parametric study to assess the structural performance and failure modes of over 500 CFS elements with various lengths, thicknesses and cross-sectional dimensions under 19 different load eccentricities. It was demonstrated that the element and web slenderness ratios and the magnitude and direction of eccentricity are the key factors affecting the behaviour of the CFS beam–column elements. The accuracy of current design specifications, including American Iron and Steel Institute (AISI-S100), Australian/New Zealand Standard (AS/NZS-4600) and European standard (Eurocode-3) was then investigated. Subsequently, the results were used to propose a new design interaction equation as a function of element and web slenderness ratios. It was shown that the proposed equation could considerably improve the accuracy of the code strength predictions, especially in the case of medium to high slenderness elements. Finally, a reliability analysis was conducted within the framework of the AISI-S100 to ensure that the proposed design equation provides the required level of safety.

Structural Design for Roll-Formed Aluminium Alloy Perforated Channels Subjected to Interior-Two-Flange Web Crippling: Experimental Tests, Numerical Simulation, and Neural Network

This study analyses the interior-two-flange (ITF) web crippling strength of roll-formed aluminum alloy lipped channels (RA channels) with web holes employing experimental testing, numerical modeling, and deep neural network (i.e., Deep belief Network, DBN). A total of 30 experimental tests on web crippling behavior were carried out, with the results utilized to validate a finite element (FE) model, developed in this study. The experimental results were compared to the data produced by the validated FE model, which was then used to train the DBN model. The results of the DBN prediction were shown to be around 5% more conservative than the FE results. In order to evaluate the effects of associated factors on the ITF web crippling strength of RA channels, a comprehensive parametric study was conducted using the DBN. The design guidelines that are currently available in the American Iron and Steel Institute (AISI 2016), the Australian and New Zealand Standards (AS/NZS 1997; AS/NZS (2018)), and the Eurocode (CEN 2007) were found to be unreliable while determining the ITF web crippling strength of RA channels. The DBN's predictions developed new formulae for calculating the web crippling strength reduction factors. After conducting a reliability study, it was found that the developed strength reduction factor equations are reliable when calculating the ITF web crippling strength of such perforated roll-formed aluminium alloy channels.

EVOLUTION OF USA COMPOSITE CODES: CHANGES IN CHAPTER I (COMPOSITE CONSTRUCTION) OF THE AISC 360‐22

AbstractThis paper briefly reviews the evolution of composite codes in the USA in the context of important changes for the 2022 edition of the American steel design specification for buildings Major changes include the incorporation of composite walls as a new type of composite member, the addition of new provisions for shear capacity of filled members, and the introduction of a performance‐based procedure for qualifying new types of anchors. An appendix also allows for the use of high strength materials for concrete filled rectangular members. The paper then describes the write's opinion on (1) important issues that need to be addressed on the direction of future codes, (2) areas where more research work is needed to provide more consistent and simpler design rules and (3) the desirability of including additional topics into the main specification.

Experimental assessment of link slabs in continuous span applications of press-brake-formed tub girders

The scope of this effort is to evaluate the performance of a link slab transversely connecting press-brake-formed tub girders (PBFTG). Modular PBFTGs were developed by a technical working group within the Steel Market Development Institute’s (a business unit of the American Iron and Steel Institute) Short Span Steel Bridge Alliance, led by the current authors. This working group consists of stakeholders in the steel bridge industry, including mills, fabricators, service centers, industry trade organizations, universities, and bridge owners. A full-scale link slab transversely joining two PBFTGs was fatigue loaded simulating a 75-year fatigue life in a rural environment. Strain and deflection data was recorded and compared throughout the fatigue life to determine the link slab’s effectiveness. Results of this effort show the link slab detail performs adequately throughout its fatigue life.

Strong dependency of the tribological behavior of CuZr-based bulk metallic glasses on relative humidity in ambient air

Thanks to their outstanding mechanical properties, Bulk Metallic Glasses (BMGs) are new alternatives to traditional crystalline metals for mechanical and micromechanical applications including power transmission. However, the tribological properties of BMGs are still poorly understood, mostly because their amorphous nature induces counter intuitive responses to friction and wear. In the present study, four different BMGs (Cu47Zr46Al7, Zr46Cu45Al7Nb2, Zr60Cu28Al12, and Zr61Cu25Al12Ti2) underwent ball-on-disc friction tests against 100Cr6 steel balls (American Iron and Steel Institute (AISI) 52100) at different relative humidities (RHs) ranging from 20% to 80%. Controlling humidity enabled to observe a high repeatability of the friction and wear responses of the BMG. Interestingly, the friction coefficient decreased by a factor of 2 when the humidity was increased, and the wear rate of BMGs was particularly low thanks to a 3rd-body tribolayer that forms on the BMG surface, composed of oxidized wear particles originating from the ball. The morphology of this tribolayer is highly correlated to humidity. The study also identifies how the tribolayer is built up from the initial contact until the steady state is achieved.

Sectional capacities of cold-formed perforated steel channel columns

Holes are pre-punched in the web of cold-formed steel channel columns to accommodate the technical systems. Many research studies have considered and illustrated the impacts of web holes on the capacities of such steel channel columns. These impacts have been accounted for in the American Specification AISI S100-16 using a new design method termed as the Direct Strength Method (DSM). This method allows designers to predict the capacities of cold-formed steel members on the basis of elastic buckling analyses. These analyses can be carried out by using a new module software package CUFSM recently developed by The American Iron and Steel Institute to analyse the buckling behaviors of cold-formed steel sections with perforations. This paper is aimed to apply the DSM to investigate the sectional capacities of cold-formed steel channel columns with a variety of hole dimensions. The behaviors and strengths of these perforated steel channel sections are analysed; recommendations are subsequently provided for the optimum of capacities in terms of the same hole areas. It was found that perforated channel columns with smaller heights and longer lengths are more beneficial for sectional capacities in general. .

Analytical Prediction of the Distortional Buckling Loads for Cold-Formed Channel Beams with Edge-Stiffened Rectangular Web Openings

Recently, there has been an increasing number of studies on the distortional buckling analyses of cold-formed steel (CFS) channels with web edge-stiffened holes. However, the literature about the analytical solutions is scarce, and the current design rules, e.g., the American Iron and Steel Institute (AISI 2016) and the Australian/New Zealand standards (AS/NZ 4600: 2018), provide little design advice for CFS channels with edge-stiffened holes. This paper presents an analytical method for estimating the bearing capacity for the distortional buckling of CFS channel beams with edge-stiffened rectangular web holes. To validate the proposed method, comprehensive finite element (FE) analyses were performed. The proposed design equations accurately forecast the distortional buckling moment capacities of the CFS channels with edge-stiffened holes. Specifically, the average error of the critical moment predictions for the distortional buckling of perforated CFS channel beams obtained by the proposed analytical method and the finite element method (FEM) is only 6.59%, where the maximum error reaches 17.76%. Moreover, a parameter study on the effect of the edge-stiffener length on the bearing capacity was carried out as well, and the results show that the edge stiffener indeed significantly enhanced the critical moment when it is below a threshold length, but the enhancement becomes unobvious once surpassing the threshold length.

Black Life and Photographic Time

Photographer and video artist LaToya Ruby Frazier’s The Notion of Family series (2001–14) strikingly looks forward through the past. The project traces its origins to Frazier’s teen years growing up in the industrial suburb of Braddock, Pennsylvania, a once-thriving mill town just nine miles outside of Pittsburgh that drew many African Americans northward in the decades following the failures of Reconstruction. Braddock began experiencing rapid decline in the 1970s when American steel no longer dominated the global market. The Braddock that Frazier grew up in was characterized by many of the markers of industrial disintegration: widespread unemployment, decaying infrastructure, increased drug addiction, and palpable rage and despair about the collapse of the economy and local industry, among them. Frazier uses her photographic practice to document some of these developments and reckon with the implications and meanings of these changes in conditions for those suffering their consequences. Often central to and reflected in the artist’s work is a critique of narratives of progress. This article examines the ways The Notion of Family series bears witness to Black life experienced in real time while also demonstrating the impossibility of the dominant temporal order to account for Black living and being. Sharpening focus on several of the images of Frazier’s Grandma Ruby, featured in the series, The Notion of Family also examines how Frazier uses her photographic practice to refuse the kind of willful forgetting and violent obfuscating that insists upon rendering invisible or fungible Black people who have vitalized communities like Braddock for generations.

Analytics with stochastic optimisation: experimental results of demand uncertainty in process industries

This study reports the test results of a two-stage stochastic linear programming (SLP) model with recourse using a user-friendly generic decision support system (DSS) in a North American steel company. This model has the flexibility to configure multiple material facilities, activities and storage areas in a multi-period and multi-scenario environment. The value of stochastic solution (VSS) with a real-world example has a potential benefit of US$ 24.61 million. Experiments were designed according to the potential joint probability distribution scenarios and the magnitude of demand variability. Overall, 144 SLP optimisation model instances were solved across four industries, namely, steel, aluminium, polymer and pharmaceuticals. The academic contribution of this research is two-fold: first, the potential contribution to profit in a steel company using an SLP model; and second, the optimisation empirical experiments confirm a pattern that the VSS and expected value of perfect information (EVPI) increase with the increase in demand variability. This study has implications for practicing managers seeking business solutions with prescriptive analytics using stochastic optimisation-based DSS. This study will attract more industry attention to business solutions, and the prescriptive analytics discipline will garner more scholarly and industry attention.

New Water-Ethylene Glycol Lubricants with Stearate Ionic Liquid Crystal Additive

The main purpose of the present study is to improve the tribological performance of aqueous lubricants with the use of ecofriendly, fatty acid-derived additives. The protic ionic liquid crystal bis(2-hydroxyethyl)ammonium stearate (DES) has been added to 50:50 water+ethylene glycol (W–EG) to obtain (W–EG)+0.5%DES; (W–EG)+1%DES and (W–EG)+2%DES emulsions. The new lubricants have been studied in sapphire-AISI (American Iron and Steel Institute) 316L stainless-steel pin-on-disk sliding contacts. The addition of DES reduces the friction coefficient by up to 76% and wear rate by up to 80%, with respect to (W–EG). The best performance is found for the emulsions with the lower proportion of DES (0.5 and 1 wt.%). These results have been related to viscosity and turbidity values. Wear mechanisms have been studied by Scanning Electron Microscopy/Energy Dispersive X-ray Spectroscopy (SEM/EDX) and by Raman microscopy. While W–EG shows a severe abrasive mechanism, no abrasion marks are present inside the wear track after lubrication with (W–EG)+0.5%DES, the emulsion with the lowest wear rate. After lubrication with W–EG, an increase in oxygen content is observed inside the wear track, as determined by EDX and confirmed by Raman microscopy, which shows the presence of iron oxides. The addition of DES reduces these oxidation processes.

The Gokteik Viaduct: A Tale of Gentlemanly Capitalists, Unseen People, and a Bridge to Nowhere

This article explores technical and socio-political factors that impacted construction of the Gokteik Viaduct railway bridge in Shan State, Burma, and the recurring failure of political powers to complete a continuous railway between Rangoon (Yangon) and Yunnan. Under rather contentious circumstances, the British government awarded an American steel company with the contract to construct what would become the world’s longest railway trestle bridge at the time of its completion in 1900. As an engineering marvel of its era, the Gokteik Viaduct is in the same category as the Eiffel Tower in Paris. Until now, however, scarce research has explored the Gokteik Viaduct in terms of historicity and factors that ultimately prevented this structure from fulfilling its intended purpose of transporting trainloads of marketable goods between Burma and Yunnan. This raises an ironic question: How could engineers construct such a remarkable bridge to service a railway that was never finished? Furthermore, why does the Gokteik Viaduct largely remain unexamined in terms of its noteworthy place in the geopolitics of Southeast Asia? In answering such questions, the authors conclude that the “unseen” story of the Gokteik Viaduct is not only about engineering prowess but of a political and social environment that continues to bedevil massive infrastructure projects in Upper Burma today.

Investigation of sectional capacities of cold‐formed perforated steel channel sections

AbstractWeb holes are commonly seen in cold‐formed steel channel sections to accommodate the technical services. The presence of the web holes has resulted in the reduction of the sectional capacities of the cold‐formed steel sections and has been considered in the design according to the American Specification AISI S100‐16 using a new approach in the design called the Direct Strength Method (DSM). This article, therefore, will use this design method to investigate the sectional capacities of perforated channel sections under compression or bending with the variation of hole sizes in relation to those of gross channel sections. Elastic buckling analysis – a compulsory requirement for application of the DSM – can be conducted using a module CUFSM software program recently developed by the American Iron and Steel Institute. The investigated channel sections are taken from the availably commercial sections. The obtained sectional capacities are seen as the opposite trends for local and distortional buckling modes, although a downtrend of the sectional capacities is found in general with the increase of hole dimensions. It was found that perforated channel sections with smaller hole height and longer hole lengths were recommended to obtain the optimum section capacities in terms of the same web hole area, but the opposite trend was seen for these sections under bending with long hole lengths.