CFSRC Colloquium 2020


Recent Submissions

Now showing 1 - 20 of 55
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    Post-elastic Capacity of Thin-walled Cold-formed Steel Members
    (2020-10) Dubina, Dan; Ungureanu, Viorel; Kotelko, Maria
    The paper presents the possibility to apply the local plastic mechanisms to characterize the ultimate strength of thin-walled cold-formed steel members subjected to eccentric compression. In previous papers [13], [14], [18], the authors have shown that, for compression or bending, the failure of such sections modelled by localized plastic mechanisms characterize better the behaviour of thin-walled cold-formed short members in Ultimate Limit State. These models are consistent with the real failure mechanism of short members and were confirmed both by experimental tests and advanced elastic-plastic FEM analyses. Selected results from these studies are summarized in Chapter 2 of the paper. The main aim of the actual paper concerns the more complex problem of members subjected to combined loadings i.e. compression and bending or eccentric compression. The failure model of slender members in eccentric compression is still an open question. In an attempt to solve this problem, the authors propose a consistent methodology which applies the General Method of EN1993 Part 1-1, in which the section resistance, prone to bending and compression, is characterized through plastic mechanism failure models.
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    Material properties of cold-formed steel under subzero temperatures
    (2020-10) Xia, Yu; Sudhiwana, Tanapat; Blum, Hannah
    Cold-formed steel (CFS) structures are becoming increasingly prominent in many construction scenarios because of its distinct advantages, which includes light-weight, easy and low cost for stacking, transportation, and construction. One of the potential application scenarios of CFS is the use under subzero temperature, including being utilized in circumpolar latitude area and functioning as storage racks in industrial freezers. Although recent researchers have made many efforts on knowing the material properties of CFS in ambient and high-temperature scenarios, the existing data on the performance of CFS under subzero temperature condition is still highly limited. In this study, from material prospective, a series of tensile coupon tests were designed and carried out on specimens made of CFS sheet with a nominal yield strength of 400 MPa at different temperatures from ambient to -60◦C. Test results, including stress-strain relationships, elastic modulus, upper yield strength, yield strength, ultimate strength, and ductility, at different target temperature and their changing tendency along temperature change are thoroughly discussed. The test results from the experimental study provide essential data for developing better design guidelines for CFS structures, such as storage racks, in low temperature scenario.
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    Proceedings and Summary of the 2020 CFSRC Colloquium
    (2020-10-22) Ayhan, D.; Blum, H.; Peterman, K.D.; Schafer, B.W.
    With 110 concurrent attendees from 15 time zones and 51 papers and talks the global online Colloquium held from 20-21 October 2020 provided a unique forum for sharing and learning about the latest research and innovations in cold-formed steel structures. The Cold-Formed Steel Research Consortium (CFSRC) hosted the Colloquium which was delivered in four main sessions on Zoom with concurrent conversations, messaging, and a central blog in a dedicated Slack site. Attendees were able to listen and see the latest research, click through on the program to the accompanying paper, and contribute in real time to the ongoing conversations about the work being presented. CFSRC Director Ben Schafer provided a consistent online conversation throughout the Colloquium. The Colloquium was sponsored by: the America-China Steel Framing Association (ACSFA), the American Iron and Steel Institute (AISI), the Center for Cold-Formed Steel Structures (CCFSS), the Cold-Formed Steel Engineers Institute, Clark Dietrich, the Metal Building Manufacturers Association (MBMA), RunToSolve, the Steel Deck Institute, United States Gypsum (USG), United States Steel (USS), and Verco Decking. The participation of the sponsors not only demonstrated their commitment to innovation in cold-formed steel structures it also enabled a series of awards to be made to the next generation of of cold-formed steel researches through student awards for both best paper and best presentation. Amanpreet Singh, Graduate Student, Department of Structural Engineering, University of California, San Diego won the best paper award for his paper “Lateral Response of Cold-Formed Steel Framed Steel Sheathed In-line Wall Systems Detailed for Mid-Rise Build”. Harikrishnan Magarabooshanam, PhD researcher, School of Civil & Environmental Engineering, Queensland University of Technology won honorable mention for his paper “Numerical Study of Double Stud LSF Walls Exposed to Fire Conditions”. Astrid W. Fischer, Graduate Candidate, Johns Hopkins University Civil and Systems Engineering Department won the best presentation award for her work on “Topology Optimization of Cold-Formed Steel Deck Diaphragms with Irregularities”. The awards committee provided three honorable mention awards for best presentation, including: Hernan Castaneda, Graduate Research Assistant, Department of Civil & Environmental Engineering, University of Massachusetts Amherst, for his work on “Characterizing Wall-to-Diaphragm Moment-Rotation Response in Cold-Formed Steel Systems via Fastener Limit States”; David Manta, CERIS and Departamento de Engenharia Civil, Faculdade de Ciencias ˆe Tecnologia, Universidade Nova de Lisboa for his work on “Linear and bifurcation analyses combining shell and GBT-based beam finite elements”; and Fani Derveni, PhD Candidate, Department of Civil & Environmental Engineering, University of Massachusetts Amherst, for her work on “Impact of Fastener Spacing on the Behavior of Cold-Formed Steel Shear Walls Sheathed with Fiber Cement Board”. In addition, the awards committee made special note of a high quality contribution from an undergraduate researcher Olivia Oey, Undergraduate Student, School of Civil Engineering, University of Sydney for her paper “Nonlinear Analysis of Cold-Formed Channels Bent about the Minor Axis“. The 51 papers in the Colloquium program are all publicly accessible through a permanent host from the Sheridan Libraries at Johns Hopkins University. Each paper represents a unique contribution to our knowledge of the behavior, performance, and design of cold-formed steel structures. Papers addressed all aspects of the performance of cold-formed steel structures. Notable in the collection is a large number of papers addressing fire performance and analysis, and earthquake engineering of cold-formed steel as well as papers addressing the fundamental stability of thin-walled cold-formed steel members, systems and applications. The Colloquium was organized by Dr. Deniz Ayhan (CFSRC Scholar), Dr. Hannah Blum (CFSRC Affiliated Investigator), Dr. Kara Peterman (CFSRC Affiliated Investigator), and Dr. Ben Schafer (CFSRC Director). During the Colloquium CFSRC student investigators: Chu Ding, Astrid Fischer, Hamid Foroughi, and Zhidong Zhang provided much needed technical support to ensure the sessions all ran smoothly. CFSRC brings together researchers and facilities across institutions in North America to form the premiere organization in the world devoted to comprehensive, innovative, and impactful research to advance the design of cold-formed steel structures.
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    Optimization of flexural strength for cold roll formed sections using design of experiments and response surface methodology
    (2020-10-20) Qadir, S.J.; Nguyen, V.B.; Hajirasouliha, I.; Cartwright, B.; English, M.A.
    In this study, the buckling and ultimate strengths of cold rolled channel sections with intermediate stiffeners were studied using numerical modelling. In order to improve the section strength, various alternative sections of varying intermediate stiffeners were developed and searched for the maximum ultimate strength. The section flexural strength was optimized through a practical approach that combines finite element modelling and optimization using design of experiments (DOE) and response surface methodology. In this approach, a nonlinear finite element model was first developed for a referenced channel section subjected to four-point bending tests and this reference section was then parameterized in terms of geometric dimensions and material properties using the DOE technique. In the next step, a response surface was used to determine the influences of the stiffener’s properties on the section distortional buckling and ultimate strength including its location, shape, size and material properties by the cold work at the section corners and stiffener bends. Response surface design optimization was then used to determine the geometric dimensions and material properties of novel channel sections. The new optimized channel sections were then applied loading up to failure to obtain ultimate flexural strengths and the results were compared to those of the reference channel section. It was found that sections with maximum ultimate strength in distortional buckling could be obtained with both the stiffeners’ position, shape and size, and the cold work influence. The cold work influence was found most significant in the novel channel sections. An optimal shape for the channel section with maximum ultimate strength in distortional buckling could be obtained without increasing the amount of the material used.
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    The Direct Strength Method for Combined Bending and Web Crippling of Second-Generation Trapezoidal Steel Sheeting
    (2020-10-20) Willems, D.W.C.; Hofmeyer, H.; Snijder, H.H.; Schafer, Benjamin W.
    Second-generation trapezoidal sheeting, characterised by longitudinal stiffeners in webs and flanges, is loaded near a support by a concentrated force and a bending moment. Currently, design codes predict related failure by: (a) determining the ultimate bending moment via the effective width approach or the Direct Strength Method (DSM); (b) finding the web crippling load via a curve-fitted formula; and (c) using an interaction rule to take into account the load combination. However, the effective width approach is quite complex to use for many longitudinal stiffeners, and the accuracy of the design code approach is subjected to improvement. Moreover, nowadays the DSM provides a consistent and well-established method to predict ultimate loads for cold-formed steel structures. Therefore, in this paper the application of DSM for combined bending and web crippling of second-generation sheeting is investigated. First a set of internationally representative secondgeneration trapezoidal sheeting types is used to create a set of numerical experiments, where sheet-sections are subjected to a three-point bending test. Then finite element models are developed and verified, and used to predict the buckling, yield and ultimate loads for the set of numerical experiments. With the results from the numerical experiments, an explicit DSM approach is developed, which predicts the ultimate load for combined actions directly. Hereafter, also an interaction DSM approach is studied, which first predicts the ultimate bending moment by the DSM, then the web crippling load by the DSM and then uses a classic interaction rule for the load combination. The explicit and implicit DSM approaches perform equally well, with a coefficient of variation equal to 0.13. The interaction DSM approach resembles the current design rules most and is therefore the preferred approach, although the explicit DSM approach is more direct and certainly deserves consideration too.
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    Numerical investigation of the impact of bearing condition on the axial behavior of variable-height cold-formed steel stud wall assemblies
    (2020-10-20) Joorabchian, Abbas; Li, Zhanjie; Peterman, Kara D.
    This paper is devoted to identifying and numerically characterizing the strength of cold-formed steel (CFS) wall assemblies of various height with non-uniform bearing conditions. The results are for a means of evaluating existing design guidelines presented in the North American Specification of the American Iron and Steel Institute (AISI S100-16). In this standard, the bearing condition of the members is not included in equations for predicting axial strength. However, based on the recent experiments done by the authors, non-uniform stress distributions at the ends of CFS studs, caused by different bearing conditions, can reduce the axial capacity of the assemblies. The sources of nonuniformity considered were finite flexibility of the concrete slabs, uneven bearing surfaces provided by the slabs, distance of the wall assemblies to the slab edge, or overhang conditions caused by construction error. In the experiments done by the authors, the height of lipped-channels was fixed to 12 inches to enable comparison across specimens. However, in typical construction, wall assemblies installed on concrete slabs are generally full-height (8 ft or higher) and thus globally-dominant. In this paper, various heights are considered for the studs. They are determined based on the local, distortional, and global buckling half-wavelengths. The impact of bearing conditions on the strength is further elucidated via high-fidelity 3D finite element analyses (FEA). The results of FEAs clarify how the non-uniform stress distribution at the ends of the studs or partial bearing conditions can impact their strengths when they buckle locally, distortionally, and globally. The finite element models are calibrated with existing experimental results. Comparison to available experimental results and to the governing design codes are provided.
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    Study on Sectional-Global Interaction Buckling of Stainless Steel Lipped-C Beam-Columns
    (2020-10-20) Yang, Yueming; Han, Kang; Niu, Shuang
    As part of a research series concerning sectional and member capacity of cold-formed stainless steel beam-columns, this paper presents some experimental and simulated results on the interaction buckling behavior of stainless steel lipped-C beam-columns. Two series of tests (12 specimens in each series) were carried out first, for which the cross-section geometry and end restraints of specimens were designed to obtain distortional-global and local-global interaction buckling respectively. The experiments involved two alloys (austenitic S30401 (1.4301) and duplex S32205 (1.4462)) and three loading eccentricity levels (none, small and large). A detailed finite element model based on ABAQUS was developed and verified against test date.
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    Strength of Steel-to-Steel Screw Connections - Update to Provisions
    (2020-10-20) Stevens, Thomas; Sputo, Thomas; Bridge, Jennifer A.
    The objective of this research was to review the existing provisions of the AISI S100-16 North American Specification for Cold-Formed Steel Structural Members [1], for screw connections loaded in shear and tension (but not combined actions). This study performed a comprehensive analysis of available steel-to-steel screw connection strength test data, totaling 702 shear tests, 143 pull-over tests, and 335 pull-out tests. The tested strength of these connections was compared to the predicted strength from the existing strength equations in the AISI S100-16 Standard. The validity of the existing equations was evaluated based on how well the predicted strengths matched the tested strengths. From this analysis, recommended adjustments to the equations, factors of safety, and/or resistance were determined and reported. This study found that the existing equations in AISI S100-16 for screw connections loaded in shear do not need to be revised, although the resistance factors for both LRFD and LSD could be increased. For the limit state of pull-over, the existing equations in AISI S100-16 do not need to be revised, while the resistance and safety factors for pull-over could be revised, with distinction between connections with ductile steel and connections with low-ductility steel. This study did not look at the effect of geometry on pull-over, and further investigation is recommended. For the limit state of pull-out, the analysis of available test data indicates that the current nominal strength prediction equation in AISI S100-16 should be revised by including an adjustment factor into the equation. The proposed adjustment factor results in increased usable strength in connections with sheet thickness greater than 0.04 inches. It was found that the pullout resistance factors could be increased slightly.
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    Metal Building Roof Purlin Line Strength by Computation
    (2020-10-20) Moen, Cristopher D.
    A computation-based method for metal building purlin and girt design is introduced using the AISI S100-16 North American Specification for the Design of Cold-Formed Steel Structural Members. Purlin section properties, span length, material properties, and boundary conditions, including bracing connectivity to exterior screw-fastened or standing seam panels, are defined. Flexure, shear, and torsional strengths are calculated along the line. The capacity of the roof or wall system is determined by applying a gravity or uplift load until a strength limit state is reached. For uplift loads, buckling deformation of the purlin free flange between intermediate bridging is considered. The calculations are performed with an open-source software package called StructuresKit.jl written in the Julia computing language. Predicted strengths from the calculation method are compared to the experimentally determined strengths from 49 simple span Cee and Zee wall girt line uplift pressure box tests, some of which were constructed with rigid board insulation.
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    Effect of holes and stiffeners on the behavior of Eccentric loaded cold-formed steel built-up channel columns - numerical investigation
    (2020-10-20) He, Ziqi; Yang, Guang; Schafer, Benjamin W.; Zhou, Xuhong
    Cold-formed steel members often need to be opened in the web due to the passage of the building system pipeline. In general stiffeners of the web maybe strengthen their structural performance. In the field of cold-formed steel structures, such as multi-layer houses, wall frames and portal frames, the use of built-up cold-formed steel channel sections are becoming increasingly popular. Such members are often under the combined effects of compression and bending. Limited research has been done on the subject. In this paper, the back-to-back built-up cold-formed steel beam-columns are studied to understand the influence of stiffeners and openings on the ultimate bearing capacity and failure mode. First, this paper presents the results of experimental tests performed on back-to-back built-up cold-formed steel channel sections under axis and eccentric compression. Detailed observations on different failure modes and column strengths were made through varying the location of stiffeners and holes, length and cross section of columns, the magnitude and direction of eccentricity. Then, a non-linear finite element model was developed which includes material non-linearity, geometric imperfections and explicit modeling of web fasteners. A comprehensive parametric study consisting of 222 models has been carried out covering a wide range of eccentricity and web fasteners for the considered back-to-back built-up columns. Finally, based results of numerical research, the ultimate capacities were used to assess the performance of the current technical specifications of cold-formed thin-walled steel structures, North American codes, AS/NZS and China specification. As the test cannot be done during the epidemic, the correctness of the formula needs to be verified by subsequent tests.
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    Structure Performance of Cold-formed Steel columns reinforced by Channel Sleeve under Axial and Eccentric compression
    (2020-10-20) He, Ziqi; Li, Qixiu; Schafer, Benjamin W.; Zhou, Xuhong
    Due to the weak torsional stiffness of cold-formed thin-walled channel members, distortional buckling behavior maybe controlled the ultimate load-capacity under certain conditions. Therefore, a new section reinforced by Channel Sleeve is proposed in order to improve the structural capacity of channel columns in this paper and is performed on the axial and eccentric compression tests. The influence of Channel Sleeve spacing on the bearing capacity and failure mode is studied, and the beneficial effect of the Channel Sleeve on the bearing capacity is verified. First, the corresponding numerical modeling of the experiments is presented in detail by describing the numerical models, types of finite elements and methods of analyses. Second, the reinforced cold-formed steel members were subjected to axial and eccentric compression analysis. Next, the magnitude, direction of eccentricity and the sleeve position are varied, in order to address their effect on the columns' capacity and structural behavior. In addition, the numerical model is used to analyze the parameters such as the slenderness ratio of the specimen, the magnitude and direction of eccentricity. The influence of these parameter changes on the structural performance of the members under the action of axial and beam-column compression members is obtained. Finally, compare the bearing capacity of the axial compression specimen with the bearing capacity calculated by the North American Code.
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    Effects of pinching on seismic performances of unbraced steel storage pallet racks
    (2020-10-20) Dai, Liusi; Zhang, Peng; Ren, Chong
    Cold-formed steel storage unbraced pallet racks are generally used to store goods in large warehouses, and the existing full-scale shaking table tests show that a typical unbraced pallet rack exhibits a global failure mechanism with damaged connections and undamaged structural members. Therefore, the significant pinching of beam-to-upright connections has a significant influence on the structural seismic performance. The paper presents a numerical investigation into the effects of pinching on seismic performances of unbraced steel storage pallet racks. A FE model of cold-formed steel storage pallet racks subjected to seismic loads is developed to perform non-linear time-history analyses via OpenSees. The full-scale shaking table test results are employed to validate the FE model. Various connection models, including the modified Pinching 4 connection model, the hysteretic model, and the elastic model, are implemented in the simulation. The structural seismic performances based on different connection models are then compared. In particular, the connection behaviours defined by the modified pinching and hysteretic models are presented and compared. Moreover, the corresponding damage index (DI) of a typical connection is also calculated based on two different damage models. The results show that the pinching of connections greatly increases the structural seismic response in respect to the global displacement and interstorey drift, and should be carefully considered in the seismic design of cold-formed steel storage unbraced pallet racks.
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    A State-of-the-Art Review of Testing by Analysis in Cold-Formed Steel Design
    (2020-10-20) Koh, Hyeyoung; Blum, Hannah B.
    New product development is crucial to allow innovation in the cold-formed steel structural industry. However, the required physical testing of new components and assemblies are often a cost barrier which prevents implementation and slows new product development. Testing by analysis can be a good alternative to physical testing as it reduces the expense and time for performing physical experiments, however, two considerations are necessary to ensure accurate results. First, it requires a rational engineering analysis to calculate the capacities and deformations of the system, and the requirements to produce accurate analyses must be explicitly stated. Second, it is necessary to understand if the software used is capable of correctly modeling the behavior of standard thin-walled and nonsymmetric structural members and systems. This study aims to evaluate existing design standards that include numerical test-based design for both cold-formed steel and other industries. Recommendations for the use of testing by analysis based on the design standards and recent research relevant to testing by analysis are presented. The results of this study will assist with determining recommended requirements for accurate design and testing by analysis.
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    Extensions of the constrained Finite Strip Method for thin-walled members: closed sections and sections with rounded corners
    (2020-10-20) Li, Zhanjie; Jin, Sheng
    The objective of this paper is to provide a derivation for a constrained Finite Strip Method (cFSM) stability solutions that applied to thin-walled members with closed sections and sections with rounded corners. The current cFSM is able to provide the decomposed stability solutions for members with open sections – single branch and multi-branch. However, with the mode definitions and implementation adopted in current cFSM, there are limitations that inhabit its applications to other general sections, such as closed section, section with rounded corners, and curved sections. To overcome these limits, the traditional implementation approach of the Global (G), Distortional (D), and Local (L) modes through the warping displacement has been revisited and its relationship with the transverse displacements (i.e., Degree of Freedom, DOF) are then used to build the characteristics of these transverse displacements. Then, following the core assumptions of the mode definitions in current cFSM, a new implementation approach is adopted to establish the mode classes: through the transverse displacements instead of the warping displacement. Then, several other techniques are further introduced to enable the cFSM for overcoming the aforementioned limitations. First, the bredt shear strain for closed sections is incorporated along with the conventional in-place shear. Second, for section with rounded corners, the transverse DOFs, the controlling DOFs in the new implementation for the D modes are categorized into secondary DOFs (i.e., that can be determined from the controlling DOFs) whilst they are set as the controlling DOFs for L modes. Finally, numerical examples of several thin-walled steel members are illustrated to highlight the consistency of the new cFSM with current cFSM for open sections and the applicability to closed sections and sections with rounded corners.
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    Ductility Demands on CFS Structural Connections of Advanced High Strength Steel
    (2020-10-20) Ding, Chu; Li, Zhanjie; Blum, Hannah; Xia, Yu; Schafer, Benjamin W.
    The objective of this paper is to investigate the ductility demand for typical cold-formed steel (CFS) connections when advanced high strength steel (AHSS) is used for the components. Although currently AHSS is mostly used in the automotive industry, the availability of AHSS sheet thicknesses directly applicable for typical CFS use, and similar forming techniques, makes AHSSs ideal candidates for developing next-generation cold-formed construction steel. Research in the last few decades has led to entire families of AHSS grades with unique combinations of strength and ductility (i.e., elongation). For the pursuit of safety and economy, it is important to determine the actual ductility demand of CFS construction so that acceptable ranges of ductility capacity and associated strength reduction factors can be established. Since connections often present the highest ductility demand for materials in CFS construction, this study attempts to bound the ductility demand by testing AHSS in lap-shear bolted connections. The testing program includes five AHSS grades (two dual-phase and three martensitic) and one mild steel grade. Four primary failure modes are studied: bearing, tilting/bearing, net section, and end tear-out. The connection strengths are compared to predictions by design equations in code and literature. The influence on connection strength and deformation resulting from using AHSS are studied. An in-depth understanding of these influences from a fracture standpoint is also explored through numerical simulations. Overall the work intends to provide the first steps towards bringing a wider class of sheet steels to CFS construction.
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    Modeling of stress-strain relationship of advanced high-strength cold-formed steel at elevated temperature
    (2020-10-20) Xia, Yu; Yan, Xia; Gernay, Thomas; Blum, Hannah B.
    Recent material advances in the steel manufacturing processes have led to materials with greatly enhanced capabilities at competitive cost. New grades of cold-formed steels, referred to as Advanced High-Strength Steels (AHSS), have been developed with yield strengths up to 1200 MPa and ultimate strengths up to 1900 MPa. However, the behavior of these novel materials must be understood and characterized under extreme environments which may arise in structural applications, including high temperatures resulting from fire. In most current design codes, including the American Iron and Steel Institute standard, Eurocode and the Australian Standard, the properties of high strength cold-formed steel subjected to fire conditions are limited or non-existent. A series of steady-state coupon tensile tests for two families of AHSS with nominal yield strength of 340 MPa, 700 MPa, 1030 MPa and 1200 MPa at various uniform temperature stages from ambient to 700 C were carried out. A new constitutive model was proposed based on the characteristics of AHSS stress-strain curves from the tests, and a good agreement between the test data and the model was achieved. In addition, existing stress-strain models from previous studies were investigated to represent the material properties of AHSS at elevated temperatures and compared with the updated model. The fittings of the multiple material models for various families and grades of AHSS were evaluated. The data generated by this research addresses fire safety design and will be essential in supporting the adoption of these next generation steels in future infrastructure.
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    Numerical Study of Double Stud LSF Walls Exposed to Fire Conditions
    (2020-10-20) Magarabooshanam, Harikrishnan; Ariyanayagam, Anthony D.; Mahendran, Mahen
    Fire safety of light gauge steel frame (LSF) stud walls is important in the design of buildings. Many experimental and numerical studies have been undertaken to investigate the fire performance of load bearing LSF walls under standard fire conditions. Single stud LSF walls are the most common configuration used in the residential sector for both load bearing and non-load bearing walls. But in places where higher acoustic insulation rating and load carrying capacities are required, double stud LSF walls are used. Double stud walls have two parallel rows of studs with studs located directly opposite each other. Standard fire tests of full-scale double stud walls have shown that their fire resistance level (FRL) is superior to that of single stud walls. In single stud LSF walls the major mode of heat transfer from fire side to the ambient side is by conduction through steel studs followed by convection and radiation within the cavity whereas in the case of double stud LSF walls the conduction through steel studs is significantly reduced by the air gap between the two rows of stud. In this study, numerical models were developed to simulate this complex heat transfer mechanism in the double stud LSF walls and to explain the reasons for the superior fire resistance of double stud walls. Thermal numerical analysis results were compared with full-scale standard fire test results. This paper presents the details of the numerical study of load bearing double stud walls, comparisons with fire test results and its findings.
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    Fire performance of bio-based PCM lined LSF wall
    (2020-10-20) Gnanachelvam, Sayilacksha; Ariyanayagam, Anthony D.; Mahendran, Mahen
    Light gauge steel framed (LSF) wall systems are made of cold-formed steel studs lined with different types of wallboards. Increased demand for LSF wall systems has led to researchers focusing on improving their fire performance. Moreover, the thermal mass of LSF wall systems is not adequate compared to conventional wall systems, resulting in poor thermal performance. Thermal energy storage techniques can be used to increase the thermal mass of wall systems. Phase change materials (PCM) could be used due to their high thermal storage capacity, which can increase the thermal mass of LSF wall systems. PCM absorbs or loses energy and undergoes a phase transition from solid to liquid or liquid to solid, respectively, which helps to maintain the indoor thermal comfort level. Nevertheless, few organic PCM could increase the fuel load during the fire. Fire performance of LSF wall systems enhanced with PCM has not been investigated. Therefore, this study is aimed at investigating the fire performance of LSF wall systems enhanced with bio-based PCM under standard fire conditions. Fire rated gypsum plasterboards were used as lining in LSF wall systems. Findings reveal that higher fire resistance was obtained for LSF wall systems, lined with the bio-based PCM liners. This paper presents the fire test results of LSF wall systems made of fire rated gypsum plasterboards and lined with or without bio-based PCMs.
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    Cyclic Performance of Steel Sheet Connections for CFS framed Steel Sheet Sheathed Shear Walls
    (2020-10-20) Zhang, Z.; Singh, A.; Derveni, F.; Torabian, S.; Peterman, K.D.; Hutchinson, T.C.; Schafer, B.W.
    The main objective of this research is to study fastener-level force-deformation response appropriate for standard cold-formed steel (CFS) framed steel sheet sheathed shear walls under cyclic loads. Recently completed CFS-framed shear wall tests employing thin steel sheets screw-fastened to thicker CFS-framing have recorded higher capacity and ductility for the CFS-framed steel sheet sheathed shear walls. For the seismic performance of these shear walls, the cyclic nonlinear response of the fastener connection is especially important and should incorporate the impact of shear buckling of the steel sheet on the strength and ductility of the connection. Minimal cyclic fastener-level shear test data exists, especially for combinations of screw fastened thin steel sheet and thick framing steel. To address this, a unique lap shear test following AISI S905 was designed to elucidate and characterize the cyclic fastener behavior. The specimens were loaded with an asymmetric cyclic loading protocol which intentionally buckles the sheet in the compression direction, and progressively increases in the tension direction. A total of 93 tests demonstrating a wide range of framing thickness, sheet thickness, fastener size, and loading types were conducted. Key experimental statistics, including the characterization with a multi-linear backbone curve, are provided. Fastener connection strength is sensitive to whether the thin steel sheet ply is buckling away from or towards the fastener head in some test series. AISI S100-16 screw shear strength provisions performance is evaluated. The work is aimed at providing critical missing information for CFS-framed steel sheet sheathed shear walls for use in both simulation and design.
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    Study on Section Capacity of Stainless Steel Lipped-C Beam-Columns
    (2020-10-20) Han, Kang; Yang, Yueming; Niu, Shuang
    This paper aims to explore the buckling behavior and the section capacity of cold-formed stainless steel lipped-C stub beam-columns under combined axial compression and uniaxial bending. A total of 24 stub columns were tested comprising two sets of sections designed to fail by distortional buckling mode and local buckling mode respectively. Two alloys, austenitic S30401 and duplex S32205, were employed in the experiments. Three loading eccentricity levels (none, small and large) were designed to produce different stress gradients within the tested sections. Refined finite element models were established with ABAQUS and validated with the detailed test results. A systematic geometric and material nonlinear analysis were then carried out covering two alloys, four plate thicknesses, four local/distortional buckling slenderness levels and five loading eccentricity levels. Lastly, based on the current Direct Strength Method (DSM) design expression, the modified expression for the section capacity prediction was proposed which suits both stainless steel columns and beam-columns of lipped-C sections.