Publications

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Journal Article
Cismasiu, C., J. R. G. Ferreira, and H. B. Rebelo. "Modelação tridimensional de ondas de choque em LS-DYNA." Construção Magazine.86 (2018): 24-28.
Freitas, J. A. T., and C. Cismaşiu. "Numerical implementation of hybrid-{T}refftz displacement elements." Computers & Structures. 73 (1999): 207-225. Abstract

The numerical implementation of the displacement model of the hybrid-{T}refftz finite element formulation is presented. The geometry of the supporting element is not constrained a priori. Unbounded, non-convex and multiply connected elements can be used. The approximation basis is naturally hierarchical and very rich. It is constructed on polynomial solutions of the governing differential equation, and extended to include the particular terms known to model accurately important local effects, namely the singular stress patterns due to cracks or point loads. Numerical and semi-analytical methods are used to compute the finite element matrices and vectors, all of which present boundary integral expressions. Appropriate procedures to store, manipulate and solve symmetric highly sparse systems are used. The characteristics of the finite element solving system in terms of sparsity and conditioning are analysed, as well as its sensitivity to the effects of mesh distortion, incompressibility and rotation of the local reference systems. Benchmark tests are used also to illustrate the performance of the element in the estimation of displacements, stresses and stress intensity factors.

Silva, M. A. G., C. Cismaşiu, and C. G. Chiorean. "Numerical simulation of ballistic impact on composite laminates." International Journal of Impact Engineering. 31 (2005): 289-306. Abstract

The paper reports experimental and numerical simulation of ballistic impact problems on thin composite laminated plates reinforced with Kevlar 29. Ballistic impact was imparted with simulated fragments designed in accordance with STANAG-2920 on plates of different thickness. Numerical modelling was developed and used to obtain an estimate for the limit perforation velocity V50 and simulate failure modes and damage. Computations were carried out using a commercial code based on nite differences and values obtained are compared with the experimental data to evaluate the performance of the simulation. Good correlation between computational simulation and experimental results was achieved, both in terms of deformation and damage of the laminates. Future work is advanced to include the interposition of an outer ceramic layer as well as examining the influence of dry-wet and temperature cycles on the mechanical strength of the plates and their temporal evolution under accelerated ageing.

Cismasiu, Corneliu, and Filipe Amarante P. dos Santos. "Numerical simulation of superelastic shape memory alloys subjected to dynamic loads." Smart Materials and Structures. 17 (2008): 025036 (12pp). AbstractWebsite

Superelasticity, a unique property of shape memory alloys (SMAs), allows the material to recover after withstanding large deformations. This recovery takes place without any residual strains, while dissipating a considerable amount of energy. This property makes SMAs particularly suitable for applications in vibration control devices. Numerical models, calibrated with experimental laboratory tests from the literature, are used to investigate the dynamic response of three vibration control devices, built up of austenitic superelastic wires. The energy dissipation and re-centering capabilities, important features of these devices, are clearly illustrated by the numerical tests. Their sensitivity to ambient temperature and strain rate is also addressed. Finally, one of these devices is tested as a seismic passive vibration control system in a simplified numerical model of a railway viaduct, subjected to different ground accelerations.

Rebelo, H. B., and C. Cismasiu. "Robustness assessment of a deterministically designed sacrificial cladding for structural protection." Engineering Structures. 240 (2021): 112279. AbstractWebsite

Being able to efficiently mitigate the effects of blast loads on structures, sacrificial cladding solutions are increasingly used to protect structural elements from the effects of accidental explosions and/or terrorist attacks. The present study analyses the loss of effectiveness of a deterministically designed sacrificial cladding when variability in the material properties and uncertainties in the mechanical model are considered. The results of an experimental campaign are used to validate the numerical models that allow the deterministic design of a sacrificial cladding which successfully improves the blast resistant capabilities of a given structural element. Nonetheless, it is shown that, taking into account the probabilistic variability of key parameters is of vital importance when designing sacrificial cladding solutions, since, when not properly designed for the structural element it intends to protect, adding a sacrificial cladding might negatively impact its blast resistant capabilities. Additionally, it is concluded that the deterministic approach might be against safety. In the reported case study, when comparing the admissible charge weight yielding from the deterministic and probabilistic approaches, one verifies that the former allows a higher charge weight.

Cismaşiu, Corneliu, Filipe Amarante Dos P. Santos, Rui Da Silva A. Perdigão, Vasco M. S. Bernardo, Paulo X. Candeias, Alexandra R. Carvalho, and Luís M. C. Guerreiro. "Seismic Vulnerability Assessment of a RC Pedestrian Crossing." JOURNAL OF EARTHQUAKE ENGINEERING. X.X (2018): 1-19.
Cismaşiu, Corneliu, Pedro B. S. Silva, José V. Lemos, and Ildi Cismaşiu. "Seismic Vulnerability Assessment of a Stone Arch Using Discrete Elements." International Journal of Architectural Heritage (2021): 1-15. AbstractWebsite
n/a
and Amarante dos Santos, F. P. and Cismaşiu, Pamies Teixeira C. J. "Semi-active vibration control device based on superelastic NiTi wires." Structural Control and Health Monitoring. 20 (2013): 890-902.Website
dos Santos, Filipe Amarante P., Corneliu Cismasiu, Pedro F. Gonçalves, and Mauricio Gamboa-Marrufo. "Smart glass facade subjected to wind loadings." Structures and Buildings. 167.12 (2014): 1-10.
Amarante dos Santos, Filipe, Corneliu Cismasiu, and Chiara Bedon. "Smart glazed cable façade subjected to a blast loading." Proceedings of the Institution of Civil Engineers-Structures and Buildings (2015): 1-10. Abstract

This paper investigates the dynamic behaviour of cable-supported glazing façades
subjected to medium-level air blast loads. Preliminary numerical studies are carried-out in
SAP2000 by means of a geometrically refined and simplified lumped-mass finite-element
numerical model, in order to assess the major effects of the design blast load in the main
façade components. As shown, both the glass panels and the cable system are able to
properly accommodate the incoming impulsive loads, typically involving extreme ...

Amarante dos Santos, Filipe, Corneliu Cismasiu, and Chiara Bedon. "Smart glazed cable facade subjected to a blast loading." Proceedings of the Institution of Civil Engineers - Structures and Buildings. 3.169 (2016): 223-232.
Miscellaneous
Thesis
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.