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<article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:ali="http://www.niso.org/schemas/ali/1.0/" article-type="research-article" dtd-version="1.2" xml:lang="en"><front><journal-meta><journal-id journal-id-type="publisher-id">Structural Mechanics of Engineering Constructions and Buildings</journal-id><journal-title-group><journal-title xml:lang="en">Structural Mechanics of Engineering Constructions and Buildings</journal-title><trans-title-group xml:lang="ru"><trans-title>Строительная механика инженерных конструкций и сооружений</trans-title></trans-title-group></journal-title-group><issn publication-format="print">1815-5235</issn><issn publication-format="electronic">2587-8700</issn><publisher><publisher-name xml:lang="en">Peoples’ Friendship University of Russia named after Patrice Lumumba (RUDN University)</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="publisher-id">48309</article-id><article-id pub-id-type="doi">10.22363/1815-5235-2025-21-5-462-473</article-id><article-id pub-id-type="edn">DFDCNF</article-id><article-categories><subj-group subj-group-type="toc-heading" xml:lang="en"><subject>Analytical and numerical methods of analysis of structures</subject></subj-group><subj-group subj-group-type="toc-heading" xml:lang="ru"><subject>Аналитические и численные методы расчета конструкций</subject></subj-group><subj-group subj-group-type="article-type"><subject>Research Article</subject></subj-group></article-categories><title-group><article-title xml:lang="en">Numerical Modeling of Change of Shape of Flexible Bars</article-title><trans-title-group xml:lang="ru"><trans-title>Численное моделирование формоизменения гибких стержней</trans-title></trans-title-group></title-group><contrib-group><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0000-0003-3913-9694</contrib-id><contrib-id contrib-id-type="spin">6812-9718</contrib-id><name-alternatives><name xml:lang="en"><surname>Gaidzhurov</surname><given-names>Peter P.</given-names></name><name xml:lang="ru"><surname>Гайджуров</surname><given-names>Пётр Павлович</given-names></name></name-alternatives><bio xml:lang="en"><p>Advisor of the Russian Academy of Architecture and Construction Sciences, Doctor of Technical Sciences, Professor of the Department of Structural Mechanics and Theory of Structures</p></bio><bio xml:lang="ru"><p>советник РААСН, доктор технических наук, профессор кафедры строительной механики и теории сооружений</p></bio><email>gpp-161@yandex.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0007-3766-6913</contrib-id><name-alternatives><name xml:lang="en"><surname>Danik</surname><given-names>Nikita B.</given-names></name><name xml:lang="ru"><surname>Даник</surname><given-names>Никита Борисович</given-names></name></name-alternatives><bio xml:lang="en"><p>Postgraduate Student of the Department of Structural Mechanics and Theory of Structures</p></bio><bio xml:lang="ru"><p>аспирант кафедры строительной механики и теории сооружений</p></bio><email>danik3777@mail.ru</email><xref ref-type="aff" rid="aff1"/></contrib><contrib contrib-type="author"><contrib-id contrib-id-type="orcid">https://orcid.org/0009-0001-8844-2123</contrib-id><name-alternatives><name xml:lang="en"><surname>Klimukh</surname><given-names>Alexander V.</given-names></name><name xml:lang="ru"><surname>Климух</surname><given-names>Александр Витальевич</given-names></name></name-alternatives><bio xml:lang="en"><p>Postgraduate Student of the Department of Structural Mechanics and Theory of Structures</p></bio><bio xml:lang="ru"><p>аспирант кафедры строительной механики и теории сооружений</p></bio><email>sancho.klimukh.96@mail.ru</email><xref ref-type="aff" rid="aff1"/></contrib></contrib-group><aff-alternatives id="aff1"><aff><institution xml:lang="en">Don State Technical University</institution></aff><aff><institution xml:lang="ru">Донской государственный технический университет</institution></aff></aff-alternatives><pub-date date-type="pub" iso-8601-date="2025-12-15" publication-format="electronic"><day>15</day><month>12</month><year>2025</year></pub-date><volume>21</volume><issue>5</issue><issue-title xml:lang="en">VOL 21, NO5 (2025)</issue-title><issue-title xml:lang="ru">ТОМ 21, №5 (2025)</issue-title><fpage>462</fpage><lpage>473</lpage><history><date date-type="received" iso-8601-date="2026-01-31"><day>31</day><month>01</month><year>2026</year></date></history><permissions><copyright-statement xml:lang="en">Copyright ©; 2025, Gaidzhurov P.P., Danik N.B., Klimukh A.V.</copyright-statement><copyright-statement xml:lang="ru">Copyright ©; 2025, Гайджуров П.П., Даник Н.Б., Климух А.В.</copyright-statement><copyright-year>2025</copyright-year><copyright-holder xml:lang="en">Gaidzhurov P.P., Danik N.B., Klimukh A.V.</copyright-holder><copyright-holder xml:lang="ru">Гайджуров П.П., Даник Н.Б., Климух А.В.</copyright-holder><ali:free_to_read xmlns:ali="http://www.niso.org/schemas/ali/1.0/"/><license><ali:license_ref xmlns:ali="http://www.niso.org/schemas/ali/1.0/">https://creativecommons.org/licenses/by-nc/4.0</ali:license_ref></license></permissions><self-uri xlink:href="https://journals.rudn.ru/structural-mechanics/article/view/48309">https://journals.rudn.ru/structural-mechanics/article/view/48309</self-uri><abstract xml:lang="en"><p>Flexible bars experiencing large displacements and small strains during loading are investigated. The purpose of the study: numerical analysis of the stress-strain state of flexible bars, taking into account geometric nonlinearity in a three-dimensional formulation. The displacement-based finite element method is used as the mathematical framework. The process of shape changing of the bar was modeled by incremental loading in combination with the restructuring of the geometry of the model, taking into account the resulting displacements. The bar was modeled using rectilinear beam finite elements connected at adjacent nodes by linear and rotational combined elements with variable stiffness. To conduct computational experiments, macros in the APDL language, embedded in the ANSYS Mechanical software, were written and verified. Numerical experiments were performed using finite element models with elastic hinges and without hinges. Based on the results obtained, it is established that the proposed direct incremental algorithm for solving geometrically nonlinear problems of structural mechanics is absolutely convergent. The developed method of defining the stiffness of rotational springs can be used in modeling spatial unstable frames.</p></abstract><trans-abstract xml:lang="ru"><p>Объект исследования - гибкие стержни, испытывающие в процессе нагружения большие перемещения и малые деформации. Цель исследования - численный анализ напряженно-деформированного состояния (НДС) гибких стержней с учетом геометрической нелинейности в трехмерной постановке. В качестве математического аппарата использован метод конечных элементов в форме метода перемещений. Процесс формоизменения стержня моделировался путем инкрементального нагружения в сочетании с перестроением геометрии модели с учетом полученных перемещений. Стержень моделировался набором прямолинейных балочных конечных элементов, соединенных в смежных узлах линейными и поворотными комбинированными элементами с переменной жесткостью. Для проведения вычислительных экспериментов написаны и верифицированы макросы на языке APDL, встроенного в программный комплекс ANSYS Mechanical. Выполнены вычислительные эксперименты с применением конечно-элементных моделей с упругими шарнирными вставками и без шарнирных вставок. На основании полученных результатов установлено, что предлагаемый прямой инкрементальный алгоритм решения геометрически нелинейных задач строительной механики является абсолютно сходящимся. Разработанная методика назначения жесткостей поворотных пружин может быть использована при моделировании пространственных кинематически изменяемых стержневых систем.</p></trans-abstract><kwd-group xml:lang="en"><kwd>flexible bars</kwd><kwd>finite element method</kwd><kwd>geometric nonlinearity</kwd><kwd>direct incremental method</kwd></kwd-group><kwd-group xml:lang="ru"><kwd>гибкие стержни</kwd><kwd>метод конечных элементов</kwd><kwd>геометрическая нелинейность</kwd><kwd>прямой инкрементальный метод</kwd></kwd-group><funding-group/></article-meta><fn-group/></front><body></body><back><ref-list><ref id="B1"><label>1.</label><citation-alternatives><mixed-citation xml:lang="en">Dykhovichny Yu.A. Large-span structures of the 1980 Olympics in Moscow. Moscow: Stroyizdat Publ.; 1982. (In Russ.) Available from: https://dwg.ru/lib/1136 (accessed: 21.04.2025).</mixed-citation><mixed-citation xml:lang="ru">Дыховичный Ю.А. Большепролетные конструкции сооружений Олимпиады-80 в Москве. 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