Publications

Export 66 results:
Sort by: Author [ Title  (Desc)] Type Year
A B C D E F G H I J K L M N O P Q R S T U V W X Y Z 
M
L
Santos, F. A., H. Rebelo, M. Coutinho, L. S. Sutherland, C. Cismasiu, I. Farina, and F. Fraternali. "Low velocity impact response of 3D printed structures formed by cellular metamaterials and stiffening plates: PLA vs. PETg." Composite Structures (2020): 113128. AbstractWebsite

This work studies the low-velocity impact response of 3D-printed layered structures made of thermoplastic materials (PLA and PETg), which form sacrificial claddings for impact protection. The analyzed structures are composed of crushable cellular cores placed in between terminal stiffening plates. The cores tessellate either honeycomb hexagonal unit cells, or hexagonal cells with re-entrant corners, with the latter exhibiting auxetic response. The given results highlight that the examined PETg protectors exhibit higher energy dissipation ratios and lower restitution coefficients, as compared to PLA structures that have the same geometry. It is concluded that PETg qualifies as an useful material for the fabrication of effective impact protection gear through ordinary, low-cost 3D printers.

Silva, M. A. G., C. Cismaşiu, and C. G. Chiorean. "Low velocity impact on laminates reinforced with {P}olyethylene and {A}ramidic fibres." Computational Methods in Engineering and Science. Proceedings of the 9th International Conference EPMESC IX. Eds. V. P. Iu, L. N. Lamas, Y. - P. Li, and K. M. Mok. Macao, China: A.A.Balkema Publishers, 2003. 843-849. Abstract

The present study reports low velocity impact tests on composite laminate plates reinforced either with Kevlar 29 or Dyneema. The tests are produced using a Rosand Precision Impact tester. The experimental results obtained for Kevlar 29 are simulated numerically. The deflection history and the peak of the impact force are compared with experimental data and used to calibrate the numerical model.

H
Cismaşiu, C. The hybrid-{T}refftz Displacement Element for Static and Dynamic Structural Analysis Problems. Lisboa, Portugal: Instituto Superior Técnico, 2000. Abstract

The displacement model of the hybrid-{T}refftz finite element formulation is applied to the solution of geometrically and physically linear static and dynamic problems. As the approximation bases solve locally the governing system of differential equations, the errors in the approximation affect only the implementation of the boundary conditions. Potential and elastostatic problems are used to illustrate the enforcement of the boundary conditions and the convergence of the solutions in energy, stresses and displacements, under both p- and h-refinement sequences and their insensitivity to mesh distortion, incompressibility and positioning of the coordinate system of the approximation basis. Also illustrated is the use of elements with arbitrary geometry and the efficiency that can be reached by including in the bases the solutions associated with dominant local effects, in particular those associated with singular stress fields. An adaptive p-refinement algorithm that exploits the naturally hierarchical nature of the approximation bases is presented and assessed. The formulation is generalised for elastodynamic analysis in the frequency domain of both bounded and unbounded domains, which are modelled either with absorbing boundary conditions or with semi-infinite elements that satisfy the Sommerfeld condition. The performance of the formulation is illustrated with tests on the convergence of the solutions in energy, stresses and displacements and on their insensitivity to mesh distortion, wave length and position of the absorbing boundary, for a wide spectrum of forcing frequencies and under both p- and h-refinement sequences.

Freitas, J. A. T., and C. Cismaşiu. "Hybrid-{T}refftz displacement element for spectral analysis of bounded and unbounded media." International Journal of Solids and Structures. 40 (2003): 671-699. Abstract

The hybrid-{T}refftz displacement element is applied to the elastodynamic analysis of bounded and unbounded media in the frequency domain. The displacements are approximated in the domain of the element using local solutions of the wave equation, the Neumann conditions are enforced directly and the surface forces are approximated on the Dirichlet and inter-element boundaries of the finite element mesh. Two alternative elements are developed to model unbounded media, namely a finite element with absorbing boundaries and an unbounded element that satisfies explicitly the Sommerfeld condition. The finite element equations are derived from the fundamental relations of elastodynamics written in the frequency domain. The numerical implementation of these equations is discussed and numerical tests are presented to assess the performance of the formulation.

de Freitas, J., I. Moldovan, and C. Cismaşiu. "Hybrid-Trefftz displacement element for poroelastic media." Computational Mechanics (2011): 1-15. AbstractWebsite

The elastodynamic response of saturated poroelastic media is modelled approximating independently the solid and seepage displacements in the domain and the force and pressure components on the boundary of the element. The domain and boundary approximation bases are used to enforce on average the dynamic equilibrium and the displacement continuity conditions, respectively. The resulting solving system is Hermitian, except for the damping term, and its coefficients are defined by boundary integral expressions as a Trefftz basis is used to set up the domain approximation. This basis is taken from the solution set of the governing differential equation and models the free-field elastodynamic response of the medium. This option justifies the relatively high levels of performance that are illustrated with the time domain analysis of unbounded domains.

F
Gomes, G. J., Válter Lúcio, and Corneliu Cismasiu. "Full Scale Blast testing of a High-Performance Energy-Absorbing System." PROTEDES2022. Região Sul da Ordem dos Engenheiros, Lisboa 2022.
E
Rebelo, Hugo Bento, Filipe Amarante dos Santos, Corneliu Cismasiu, and Duarte Santos. "Exploratory study on geodesic domes under blast loads." International Journal of Protective Structures (2019).
de Gomes, Gabriel Jesus, Valter José Guia da Lúcio, Corneliu Cismasiu, and José Luis Mingote. "Experimental Validation and Numerical Analysis of a High-Performance Blast Energy-Absorbing System for Building Structures." Buildings. 13.601 (2023): 1-20.
Gomes, G., H. Rebelo, V. Lúcio, C. Cismasiu, and J. Mingote. "Experimental Research and Development on Blast Resistant Structures." Advances on Testing and Experimentation in Civil Engineering, Springer Tracts in Civil Engineering. Switzerland: Springer Nature, 2023. 1-20.
Cismaşiu, C., A. Narciso, and F. Amarante dos Santos. "Experimental Dynamic Characterization and Finite Element Updating of a Footbridge Structure." Journal of Performance of Constructed Facilities.10.1061/(ASCE)CF.1943-5509.0000615 (2014).Website
Rebelo, H. B., A. Gregório, P. A. R. Rosa, D. Lecompte, and C. Cismaşiu. "Experimental characterization of 3D-printed PLA under uniaxial high strain-rate loading." AuxDefense 2018 – 1st World Conference on Advanced Materials for Defense. Lisbon 2018. auxdefense_extabstract_v2.pdf
Rebelo, H. B., D. Lecompte, C. Cismasiu, A. Jonet, B. Belkassem, and A. Maazoun. "Experimental and numerical investigation on 3D printed PLA sacrificial honeycomb cladding." International Journal of Impact Engineering. 131 (2019): 162-173.Website
Cismasiu, Corneliu, Filipe Amarante P. dos Santos, and Ana I. M. Rodrigues. "Experimental and FE updating techniques for the unseating vulnerability assessment of a footbridge structure." The 4th International Conference on Dynamics, Vibration and Control. Shanghai, China: Shanghai Institute of Applied Mathematics and Mechanics, 2014. icdvc_2014.pdf
Joaquim, Ana, Corneliu Cismasiu, Filipe Santos, and Elsa Caetano. "Estimation of the tensile force in the stay-cables of Salgueiro Maia Bridge using ambient vibration tests." ISDAC2017 - International Symposium on the Dynamics and Aerodynamics of Cables. Porto: FEUP, 2017. artigo_isdac_v5_ec.pdf
D
Santos, Filipe, Corneliu Cismasiu, Ildi Cismasiu, and Chiara Bedon. "Dynamic Characterisation and Finite Element Updating of a RC Stadium Grandstand." Buildings. 8.10 (2018): 141, 1-19.
Freitas, J. A. T., and C. Cismaşiu. "Developments with hybrid-{T}refftz stress and displacement elements." Computer Assisted Mechanics and Engineering Sciences. 8 (2001): 289-311. Abstract

The paper reports on the work on hybrid-{T}refftz finite elements developed by the Structural Analysis Research Group, ICIST, Technical University of Lisbon. A dynamic elastoplastic problem is used to describe the technique used to establish the alternative stress and displacement models of the hybrid-{T}refftz finite element formulations. They are derived using independent time, space and finite element bases, so that the resulting solving systems are symmetric, sparse, naturally $p$-adaptive and particularly well suited to parallel processing. The performance of the hybrid-{T}refftz stress and displacement models is illustrated with a number of representative static and dynamic applications of elastic and elastoplastic structural problems.

Gomes, G. J., V. J. G. Lúcio, and C. Cismasiu. "Development of a high-performance blast energy-absorbing system for building structures." AuxDefense2022 - 3rd World Conference on Advanced Materials for Defense. Guimarães, Portugal 2022.
de Gomes, Gabriel Jesus, Valter José Guia da Lúcio, and Corneliu Cismasiu. "Development of a high-performance blast energy-absorbing system for building structures." International Journal of Protective Structures. 15.3 (2024): 484-508. AbstractWebsite

Shock absorbers have been widely used in the automotive and aeronautical industries for many years. Inspired on these devices, the paper presents an analytical and numerical assessment of a high performance protective system for building structures against blast loads, which is composed of a shielding element connected to the main structure, at the floor levels, through ductile Energy Absorbing Connectors (EACs). The EACs exploit the external tube inversion mechanism to absorb a significant part of the imparted kinetic energy from the blast wave. While the system prototype has been developed in laboratory, it was characterized and tested in a full-scale blast testing campaign. A validated finite element model was used next to analyze its performance in a more demanding design scenario. The introduction of EACs notably reduces the peak horizontal loads and the kinetic energy transferred to the protected structure, being expected a significant reduction of the stresses in the supporting vertical elements, in addition to the protection of structural and non-structural members. These results encourage further studies of the presented protective system that can be potentially employed for a large variety of blast threat scenarios, especially when increasing the stand-off is not a possible/viable option and sensitive facilities have to be protected.

C
Amarante dos Santos, Filipe, Corneliu Cismasiu, and Francisco Braz Fernandes. "Cyclic Instability of Shape-Memory Alloys in Seismic Isolation Systems." International Journal of Structural Glass and Advanced Materials Research (2018): 1-14.
Santos, F., C. Cismasiu, R. Perdigão, V. Bernardo, J. Sampayo, P. Candeias, A. Costa, A. Carvalho, and L. Guerreiro COMPORTAMENTO SÍSMICO DE LIGAÇÕES EM PASSADIÇOS PRÉ-FABRICADOS. 10º Congresso Nacional de Sismologia e Engenharia Sísmica. Ponta Delgada, 2016.artigosismica2016_submetido.docx
Oliveira, Tiago, Pedro Matias, and Corneliu Cismasiu. "Comportamento de painéis de vidro laminado à ação de explosões - Geração de curvas Pressão-Impulso." PROTEDES2022. Região Sul da Ordem dos Engenheiros, Lisboa 2022.
dos Santos, Amarante F. P., and C. Cismasiu. "Comparison Between Two {SMA} Constitutive Models for Seismic Applications." Twelfth Conference on Nonlinear Vibrations, Dynamics, and Multibody Systems. Blacksburg, VA 24061 2008. Abstract
n/a
dos Santos, Amarante F. P., and C. Cismasiu. "Comparison Between Two SMA Constitutive Models for Seismic Applications." Journal of Vibration and Control. 16 (2010): 897-914. AbstractWebsite

This paper analyses and compares the dynamic behavior of superelastic shape memory alloy (SMA) systems based on two different constitutive models. The first model, although being able to describe the response of the material to complex uniaxial loading histories, is temperature and rate independent. Thesecond model couples the mechanical and kinetic laws of the material with a balance equation considering the thermal effects. After numerical validation and calibration, the behavior of these two models is tested in single degree of freedom dynamic systems, with SMAs acting as restoring elements. Different dynamic loads are considered, including artificially generated seismic actions, in a numerical model of a railway viaduct. Finally, it is shown that, in spite of its simplicity, the temperature- and rate-independent modelproduces a set of very satisfying results. This, together with its robustness and straightforward computational implementation, yields a very appealing numerical tool to simulate superelastic passive control applications.