Faculty Publications

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Subject: search.filters.subject.Local buckling

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    Investigation of local buckling behavior of web perforated plain channel stub columns
    (Elsevier Ltd, 2024) Francis, R.; Shabhari, A.; Chandrasekar, D.; Vijaya Vengadesh Kumar, J.
    As a sustainable material, cold-formed steel (CFS) is increasingly popular in structural components of buildings and industrial storage racks. The plain channel sections having a flange stiffened web element and unstiffened flange elements are prominently used as compression members in CFS systems. These elements are likely to undergo local buckling under compressive loading. The openings or closely spaced perforations along the longitudinal direction of the web for serviceability requirements on buildings and beam level adjustment requirements on storage racks lead to additional complications to the local buckling. Although the Effective Width Method and Direct Strength Method rationally cover the buckling behavior of plain channel sections, the influence of height-to-width ratio with perforations is not effectively accounted for in the design. Limited research details are available in the literature for the web perforations of lipped channels or rack sections. However, these sections do not have unstiffened flanges, where the unstiffened flanges can be more vulnerable to local buckling, e.g., plain channels. The web perforations also make the web more vulnerable to local buckling. This article examines the local buckling behavior of plain channel sections with the influence of web perforations through systematic experimental and comprehensive numerical studies. The influencing parameters of the cross-section geometry are assessed through the principal component analysis (PCA) to understand its correlation with local buckling. The PCA results shed light on mandatory parameters for the elastic critical local buckling load calculation and/or nominal local buckling strength prediction of the plain channel section. © 2024
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    Local buckling behaviour of web perforated cold-formed steel lipped channel columns
    (Elsevier Ltd, 2024) Shabhari, A.; Jeyapragasam, V.V.K.; Chandrasekar, D.
    To connect beams and bracings with storage rack uprights, closely spaced perforations are provided along the web, flanges, and rear flanges of uprights. These perforations can significantly lower the ultimate capacity of such compression members with the possible influence of its natural buckling modes. This capacity reduction can depend on various parameters such as (a) geometrical shape, proportioning of cross-section, and stiffeners; (b) perforation shape, size, spacing, and location; (b) slenderness of member, cross-section, and elements of cross-section; and (d) material properties. A thorough understanding of the influence of the above-mentioned factors is necessary for the accurate strength prediction of perforated Cold-formed steel (CFS) compression members. Even though the current design standards are updated for the accurate strength prediction of unperforated CFS compression members, they do not collectively account for the influence of all the aforementioned factors on the load-carrying capacity of the perforated CFS members, particularly for the local buckling capacity. Though the Direct Strength Method (DSM) of design is the most accepted method for accurate strength prediction of CFS members even for complex cross-sectional shapes, recent research on the strength evaluation of perforated CFS members using DSM has emphasized the need for refinement in DSM. The Modified Direct Strength Method (MDSM), which accounts for the simultaneous buckling of flanges and web, includes the cross-section aspect ratio and cross-section slenderness to predict more accurately the local buckling design strength. However, it was developed only for unperforated specimens. Hence, a systematic experimental and numerical investigation was done to understand the influence of the perforation in the local buckling behavior of the lipped channel section. In total, 14 specimens, including 2 unperforated and 12 web perforated CFS lipped channel stub columns were physically tested with fixed support conditions. The Finite Element Analysis using ABAQUS software was used to conduct an extensive parametric numerical study. The results were used to compare the strength curves of DSM and MDSM and the modification in the design curves has been proposed by considering the erosion in strength due to the presence of perforation. © 2024 Elsevier Ltd
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    Nonlinear buckling and free vibration analysis of auxetic graphene origami composite beams under nonuniform thermal environment
    (Taylor and Francis Ltd., 2025) Shashiraj; Pitchaimani, J.; Kattimani, S.
    This study examines the thermo-mechanical behavior of auxetic metamaterial beams enhanced by graphene origami (GOri) under spatially varying nonuniform temperature distributions (SVTD). Utilizing Timoshenko beam theory considering von-Kármánn type nonlinear strain–displacement relationship, GOri beams are modeled as layered structures. The Ritz method is employed to solve equilibrium equations, analyzing the impact of GOri distribution patterns, content, and folding degree on post-buckling and vibration paths. The effects of five SVTDs, three end conditions, and three GOri distribution patterns on buckling, post-buckling behavior, and nonlinear free vibration characteristics are explored. Findings reveal that the parabolic temperature distribution with peak temperatures at beam ends (P-MAE) results in higher critical temperatures and nonlinear free vibration frequencies. This research provides crucial insights into the design and optimization of GOri-enabled metamaterial structures in complex thermal environments, highlighting the significant influence of nonuniform temperature distributions along the beam’s length. © 2024 Taylor & Francis Group, LLC.
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    Experimental and Numerical Study of Applicability of Euler's Buckling Theory for Laminated Plates
    (The Aeronautical and Astronautical Society of the Republic of China, 2025) Puranik, A.M.; Kaliveeran, V.
    This study investigates the accuracy of Euler’s theory for predicting the critical buckling load of a laminated plate comprising a 2.4 mm steel core sandwiched between 1.3 mm aluminum layers, with dimensions 500 mm × 100 mm. Analytical solutions are based on Euler's buckling theory. The theoretical values are verified through ANSYS simulation and experimental testing. The results reveal the limitations of classical buckling assumptions when applied to laminated composites, emphasizing the effects of material heterogeneity. Numerical and experimental analyses confirm the influence of these factors on the critical load, providing insights into the adaptation of classical theory for complex material systems. This research offers a comprehensive framework for the buckling mechanism of laminates, bridging theoretical, computational, and experimental approaches. © 2025 The Aeronautical and Astronautical Society of the Republic of China. All rights reserved.
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    Localised edge load dependent aeroelastic stability of porous plates with GPL reinforcement under the influence of supersonic flow
    (Elsevier Ltd, 2025) Twinkle, T.; Pitchaimani, J.; Lacarbonara, W.
    Buckling and flutter characteristics of porous plates with graphene platelet (GPL) reinforcement subjected to concentrated edge loads are explored for the first time. The plate is considered to be having simultaneous variation of GPL and porosity content through the thickness. For the porous plate with GPL reinforcement, the effective material properties are determined using the Halpin–Tsai micromechanical model. Further, to obtain the solutions the Galerkin method is employed for the governing differential equations derived using Hamilton's principle. The results of the present model are validated for accuracy and reliability by comparing them with the results available in the open literature for buckling, free vibration, and flutter studies. To study the flutter behaviour of plates under the effect of different types of concentrated edge loads, several parametric studies are performed for the first time. Additionally, the influence of GPL weight percentage, amount of porosity, dispersion of porosity, and GPL on the flutter instability is investigated. The results indicate that the type of concentrated edge load has a major impact on the flutter instability of the plate with centrally distributed (case 1) type of loading leading to a higher reduction in flutter pressure. Further, an increase in porosity and GPL content significantly affects the flutter and buckling coefficient values. © 2024 Elsevier Ltd
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    Vibration and Stability Characteristics of Functionally Graded Plates Subjected to Localized Edge Loadings
    (Springer, 2025) Swaminathan, K.; Hirannaiah, S.; Rajanna, T.
    In this article, the influence of various types of localized in-plane edge loadings on vibration and stability characteristics of Functionally Graded Material (FGM) plates have been studied by developing finite element (FE) code in FORTRAN. Due to the complex arrangement of plates and situations arising during the real time application, loads acting on the member are not always uniform, rather nonuniform or localized in nature. For a such loading and boundary condition, the stress distribution within an element is highly non-uniform in nature. Therefore, the buckling loads are evaluated by dynamics approach. Here, in this study FGM plate is modelled using eight-noded isoparametric element with five degrees of freedom at each node. In the FE formulations, the influence of shear deformation and rotary inertia are included. In the FGM plate, the effective materials properties are assumed to vary in the thickness direction according to power-law distribution of volume fraction of the constituents. The analysis is carried out for four types of localized edge loads. Effect of different parameters such as boundary condition, side to thickness ratios, volume fraction exponent, load width ratio and the aspect ratio of the plate is considered to study the buckling characteristics of FGM plate. From the current study, it is mainly understood that the buckling characteristics of FGM plate of various volume fraction exponent is highly influenced by the position and width of localized in-plane edge loads. © The Institution of Engineers (India) 2024.
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    Local buckling strength enhancement due to non-slender flanges in web perforated plain channel columns
    (Elsevier Ltd, 2025) Francis, R.; Shabhari, A.; Jeyapragasam, V.V.K.; Chandrasekar, D.
    Cold-formed steel columns are the primary compression members in housing and industrial storage racks, with discrete holes or closely spaced web perforations. The element slenderness and web perforations influence the local buckling capacity. This study examines the local buckling capacity of slender web plain channel cross-sections with non-slender or slender flanges in the presence of web perforations. Fourteen plain channel stub column tests were conducted on two cross-section aspect ratios, two perforation shapes, with three perforation orientations. Further, a comprehensive parametric study was conducted using validated Finite Element models. The local buckling strength of unperforated and web-perforated cold-formed plain channel columns is evaluated using the Direct Strength Method (DSM) and Modified Direct Strength Method (MDSM). The increase in local buckling strength due to non-slender flanges becomes significant, depending on the aspect ratio and non-dimensional local buckling slenderness ratio of the plain channel cross-section. This research provides the scope to expand the applicability of DSM and MDSM design strength predictions from cold-formed steel design to general thin-walled steel sections, where the welded thin-walled steel sections can have different element thicknesses. As the element thickness plays a crucial role in element slenderness and inter-element interaction, the local buckling capacity prediction available for uniform cross-section thickness can be unduly conservative. This study highlights the significance of element slenderness and effective area reduction due to perforation shape and orientation in the local buckling strength of cold-formed plain channel sections. © 2025 Institution of Structural Engineers. Published by Elsevier Ltd. All rights are reserved, including those for text and data mining, AI training, and similar technologies.