Project name: UltimatePanel – Painéis curvos para aplicação estrutural
Research group: Mechanical Design
Objective
Parceiros: Universidade de Coimbra (Coordinator), IDMEC
Financiamento: FCT, Lisboa2020, Portugal2020, EU
Ficha do projeto (link)
Descrição:
This project was conducted to develop a clear design approach for curved panels. In order to achieve this goal, three action plans were implemented in parallel: i) experimental, ii) analytical and iii) numerical. After an initial review of existing standards and their design approaches (all identified engineering branches were taken into account), the experimental tests (served as a first step to assess the standards accuracy) and analytical and numerical studies (with parameterization of geometry, different materials, loading types) were performed. The results from the numerical study arose from benchmark models that were calibrated and validated using the experimental results. Each research team was responsible for a plan (ISISE-UC – experimental; IST-UL – analytical; UERJ – numerical). However, despite this clear definition of responsibilities, all tasks were carried out in cooperation between research teams. A huge set of results was found (see publications) and design recommendations were developed and proposed for steel structural codes.
Página do projecto:
https://isise.net/site/index.php?module=publicProjects&target=details&id=120
Contacto IDMEC: Nuno Silvestre (IDMEC was responsible for Task 4)
The aim of this task was to develop new theoretical and analytical formulations to study the linear and nonlinear behaviour of curved panels, thus allowing a better understanding of differences between curved panels and plates/shells. In particular, the main objectives of this task were:
1) Develop analytical formulations to determine the buckling loads, load-deflection curves and deformed shapes of curved panels under different loadings and support conditions.
2) Understand the roots of buckling phenomena of curved panels by means of selecting stress/strain components and/or deformation modes that are crucial to their exact evaluation.
The objectives of this task were met. The team developed Generalised Beam Theory (GBT) formulations to study the linear, buckling and post-buckling behaviour of curved panels under different loadings (pure compression, pure bending, bending and compression, shear). The published (and ongoing) papers present and discuss the obtained results on the elastic post-buckling behaviour and imperfection sensitivity of simply supported cylindrical steel panels. The results presented were obtained by means of a geometrically non-linear GBT formulation, which can include arbitrary member initial geometrical imperfections. The modal decomposition features of GBT enables extending the knowledge on the mechanics underlying these structural elements, which cannot be obtained with standard shell finite element analysis. GBT buckling analyses of curved panels with distinct curvatures were conducted and post-buckling results to assess the panels’ imperfection sensitivity were shown (distinct critical-mode initial geometrical imperfections shapes with several amplitudes) . These results provide the evolution, along the equilibrium paths, of relevant modal displacement profiles, modal participation diagrams and deformed configurations. For comparison and validation purposes, shell finite element results were also reported.
The main conclusion of this task is the buckling and postbuckling behaviour of curved panels is extremely complex. The buckling mode of a panel corresponds to a linear combination of several GBT deformations modes, which makes the development of an analytical expression to calculate the critical looad unfeasible for design practice. Additionally, this linear combination of deformations modes changes along the nonlinear equilibrium paths. As expected in these structural systems, there is a strong/detrimental influence from the initial geometrical imperfection shape and/or amplitude, regardless of the panel’s curvature. Indeed, even with a small curvature, there is a high susceptibility to the initial geometrical imperfections considered, contrarily to the post-buckling behaviour of plates (flat panels) – depending on the configuration of the initial geometrical imperfection very high, moderate or small strength stable or unstable equilibrium paths can be obtained. Moreover, higher amplitudes do not necessarily lead to lower strengths (peak loads) as other “less complex” structural systems. The critical buckling load increases with the curvature of the panel (with the same cross-section area and aspect ratio), it is not possible to provide any conclusion about the maximum-to-critical load ratio in post-buckling analysis (high influence of the initial geometrical imperfections). Consequently, the design of panels constitutes a very difficult and challenging task due to the unknown pattern of these initial imperfections.
Publicações IDMEC
Artigos em Revista Internacional
Silvestre N, Duarte APC, Martins JP, da Silva LS (2019). GBT Buckling Analysis of Cylindrical Panels Under Compression, Structures, 17, 34-42. https://doi.org/10.1016/j.istruc.2018.12.007
Martins AD, Silvestre N (2019). Modal analysis of the post-buckling behaviour of cylindrical steel panels under compression: Imperfection sensitivity and local2 interaction, Thin-Walled Structures, 144, 106345. https://doi.org/10.1016/j.tws.2019.106345
Martins AD, Silvestre N (2020). Modal Analysis and Imperfection Sensitivity of the Post-Buckling Behaviour of Cylindrical Steel Panels Under In-plane Bending, Engineering Structures, 207, 110127. https://doi.org/10.1016/j.engstruct.2019.110127
Artigos em Revista Internacional (relacionados)
Duarte APC, Pereira GB, Silvestre N. (2021). Numerical study of the influence of the stringers cross-section geometry on the mechanical behavior of compressed curved stiffened composite panels, Mechanics of Advanced Materials and Structures, Volume 28, Issue 5. https://doi.org/10.1080/15376494.2019.1578009 (this paper was Submitted on 27 Oct 2018, Accepted 08 Jan 2019, Published online: 30 Apr 2019)
Artigos em Conferência Internacional
Silvestre N, Duarte APC, Martins JP, da Silva LS (2018). Buckling and Postbuckling of Cylindrical Panels for Steel Brigde Girders, Mini-Symposium on “Steel Structures: Mechanics, Simulation and Testing”, 10th European Solid Mechanics Conference (ESMC 2018), Bologna, Italy, July 2-6, 2018.
Silvestre N (2019). Stability of thin-walled structures: recent developments in panels. Keynote Lecture, International Conference on Advances in Structural and Geotechnical Engineering, ICASGE 2019, Hurghada, Egypt, 25-28 March 2019.
Artigos em Conferência Internacional (relacionados)
Fonseca F, Duarte APC, Silvestre N (2019). Finite element modeling of CFRP fuselage panels under high velocity transverse impact loading, Invited Lecture, The Seventh International Conference on Structural Engineering, Mechanics and Computation (SEMC 2019) will be held in Cape Town, South Africa, 2-4 September 2019.
Dissertações de Mestrado (relacionados)
Gonçalo Brás Pereira (2018). Computational Modelling of Failure Stiffened Composite Panels, Master thesis on Aerospace Engineering, Instituto Superior Técnico, University of Lisbon.
Francisca Fonseca e Silva (2018). Strength of Aircraft Composite Panels under Transverse Impact Loading, Master thesis on Aerospace Engineering, Instituto Superior Técnico, University of Lisbon.
Fábio Aguincha (2019). Multi-objective optimization of curved composite laminated plates. Master thesis on Mechanical Engineering, Instituto Superior Técnico, University of Lisbon.
Helder Martins (2020). Simulation of Curved Panels under Blast Loading, Master thesis on Aerospace Engineering, Instituto Superior Técnico, University of Lisbon, in progress.