Victoria Rosca - Academia.edu (original) (raw)

Papers by Victoria Rosca

Materials

The greatest advantage of fiber-reinforced composite materials is the freedom to tailor their str... more The greatest advantage of fiber-reinforced composite materials is the freedom to tailor their strength and stiffness properties, while the most significant disadvantage consists in their high costs. Therefore, the design process and especially the optimization phase becomes an important step. The geometry of the fabric of each lamina as well as their stacking sequence need to be carefully defined, starting from some basic geometric variables. The input parameters are the widths and the heights of the tows, the laminate-stacking sequence and the gaps between two successive tows or the height of the neat matrix. This paper is a follow-up to a previous work on using and improving an in-house software called SOMGA (Satin Optimization with a Modified Genetic Algorithm), aimed to optimize the geometrical parameters of satin-reinforced multi-layer composites. The final goal is to find out the way in which various types of woven fabrics can affect the best possible solution to the problem o...

The Bulletin of the Polytechnic Institute of Jassy, Construction. Architecture Section, 2008

The main idea of meshless methods is to approximate the unknown field by a linear combination of ... more The main idea of meshless methods is to approximate the unknown field by a linear combination of shape functions built without having recourse to a mesh of the domain. The computational domain is discretized using a set of scattered nodes. The shape functions associated with a given node is then built considering the weight functions whose support overlaps the one of the weight function of this node; thus, there is actually no need to establish connectivities between the different nodes as in the finite element method. Monte-Carlo integration techniques are promising schemes in the context of meshless techniques. The purpose of the present paper is to implement in EFG a new body integration technique for the evaluation of the stiffness matrix that does not rely on a partition of the domain into cells, but rather points. Numerical examples based on three-dimensional elasticity problems are presented to examine the accuracy and convergence of the proposed method. In this context, Quas...

Sustainable Structural Design Methodology for Lattice Telecommunication Towers

19th International Multidisciplinary Scientific GeoConference SGEM2019, Nano, Bio, Green and Space: Technologies for Sustainable Future, 2019

Automatic Design for Optimal Configuration of Steel Lattice Telecommunication Towers

SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings

The Bulletin of the Polytechnic Institute of Jassy, Construction. Architecture Section, 2015

The structure of the fabric, when it is used as a composite reinforcement, have a major influence... more The structure of the fabric, when it is used as a composite reinforcement, have a major influence on the mechanical properties of a fabric reinforced composite material. Composite design and analysis requires a computer tool, not only to link composite properties to fabric micro and macro geometry, but also to link fabric micro geometry to the weaving pattern. The complex structure of textile composite comprises of several hierarchical levels: macro (composite component or sub-component), meso (unit cell of the reinforcement structure) and micro (fibre placement inside yarns and fibrous plies). The most specific to textile composites is meso level, where the structure dependent behaviour of the material is most pronounced. This is the most important level at which the optimization of the structure and the constituents should be performed. Continuous and discrete approaches are possible for the forming simulations of composite textile reinforcements because of their multi-scale struc...

Exploring barriers to Mobile e-ID adoption : A government perspective on Republic of Moldova Mobile e-ID

As more and more governments have embarked on the e-government path, providing digital interactio... more As more and more governments have embarked on the e-government path, providing digital interaction with its citizens has boosted the demand for trusted electronic identity solutions that can ensure ...

As information technology (IT) becomes an integral part of society, public sector organizations ... more As information technology (IT) becomes an integral part of society, public sector organizations have witnessed an increasing shift in how they deliver services to citizens. One area of IT that has ...

Element Free Galerkin Formulation for Problems in Composite Micromechanics

Applied Mechanics and Materials, 2015

The heterogeneity and anisotropy of structural composites make the application of the standard me... more The heterogeneity and anisotropy of structural composites make the application of the standard mesh-based methods using the meshing of interfacial region between matrix and fibers a difficult task. The objective of this study is to present the EFG formulation for problems of composite micromechanics. It is expected that the tediousness and approximations involved in mesh generation, and hence inaccuracies in the results can be avoided using the new meshless techniques such as the Element Free Galerkin (EFG) method. The theoretical methodologies, computer implementations and practical application are carried out. Periodic boundary conditions of the unit cell under tensile load are set up. The method of Lagrange multipliers is introduced for the treatment of material discontinuity at the fiber-matrix interface in which both the displacement continuity and traction reciprocity are satisfied. The EFG method is formulated for the generalized plane strain problems. Examples are presented ...

Particularities of Modelling the Mechanical Properties of Woven Composite Fabrics

Applied Mechanics and Materials, 2015

The mechanical properties of composite fabrics rely on a fabric made by a textile weaving process... more The mechanical properties of composite fabrics rely on a fabric made by a textile weaving process. In order to use their special ability of being drapeable, instead of just plain weave fabrics, satin or twill reinforcement can be selected. Although some other advantages of the resulting composite, such as good impact resistance or damage tolerance are similar to all woven reinforcement composites, the superior drapeability of satin is a major reason to favour this type of textile reinforcement. This paper is focused on the modelling procedures of stiffness characteristics, specific to satin reinforced laminated composites, using a semi-discrete approach. This method is a compromise between the continuous and pure discrete approaches and is associated with a mesoscopic analysis of the repetitive unit cell (RUC). The elastic properties of the textile reinforced epoxy composite, namely longitudinal modulus and transverse modulus, in case of carbon and fibre glass based 5-harness satin ...

Engineering Transactions

The paper uses the layerwise theory, i.e. the zigzag behaviour in-plane displacements through the... more The paper uses the layerwise theory, i.e. the zigzag behaviour in-plane displacements through the thickness, and Lagrange interpolation functions for finite element to compute stresses and displacements in beams made of composite materials. The layerwise method can determine the interlaminar stresses and other localized effects with the same accuracy as two-dimensinal finite element methods but with less computer effort. We present as illustration two examples.

The interest in the non-conventional energy resources, a consequence of the severe restrictions i... more The interest in the non-conventional energy resources, a consequence of the severe restrictions imposed towards pollution of any kind, arises again the interest in using solar collectors. Implanting them on the terraces of new or existent home residencies, or any kind of other buildings, means to solve a sum of engineering problems, among them being also the stages of safely designing the plane panels for collectors and the sustaining skeleton, made in steel as well as the fixing systems adopted for the interface with the building itself. The necessity of considering the maximum wind speeds actions along other dynamic effects of its turbulence is the result of a many years experience, specially if one must also think in terms of efficiency and costs both for construction and exploitation. The pattern of the wind flow field suffers intricate alterations in the proximity of these collectors placed in the vicinity of the building surface and, in these situations, it is common to test t...

A simple and less-costly integration of meshless Galerkin weak form

III European Conference on Computational Mechanics

... Victoria E. Rosca*, Vitor MA Leitão † *I DECivil-ICIST, Instituto Superior Técnico Av. Rovisc... more ... Victoria E. Rosca*, Vitor MA Leitão † *I DECivil-ICIST, Instituto Superior Técnico Av. Rovisco Pais 1049-001 Lisboa, Portugal victoria@civil.ist.utl.pt † DECivil-ICIST, Instituto Superior Técnico Av. Rovisco Pais 1049-001 Lisboa, Portugal vitor.leitao@civil.ist.utl.pt ABSTRACT ...

ce.tuiasi.ro

The composite action in members built up of different materials results in savings in constructio... more The composite action in members built up of different materials results in savings in construction cost. These savings can be further advanced by employing optimization techniques in the design of composite members. This paper presents an algorithm model for the cost optimization of composite beams based on the specifications of the SR EN 1994-1-1/2006: Design of composite steel and concrete structures. Design examples taken from the literature were analysed in order to validate the proposed model, to illustrate its use, and to demonstrate its capabilities in optimizing composite beam designs.

Quasi-Monte Carlo mesh-free integration for meshless weak formulations

Engineering Analysis with Boundary Elements, 2008

... Many of the so-called meshless methods, such as the element-free Galerkin (EFG) method [Belyt... more ... Many of the so-called meshless methods, such as the element-free Galerkin (EFG) method [Belytschko T, Lu YY, Gu L. Element-free Galerkin methods. Int J Numer Methods Eng 1994;37:22956], are based on the global weak form over the entire domain. ...

The climate behaviour suffers important changes as result of the impact with a rapid extension of... more The climate behaviour suffers important changes as result of the impact with a rapid extension of the anthropic space. The abrupt modification of season temperature and severe wind storms are put in evidence now all over the world. Simulation of the dynamic effects of wind action upon the built environment in laboratory is a process of scaling at reduced dimensions of a complex combination of factors insuring similarity between the natural phenomenon and the one artificially reproduced. Usually, the design wind dynamic action on structures is identified with the so-called extra-tropical depressions, specific for middle global latitudes; the atmosphere is considered neutrally stratified, the vertical profile is in equilibrium with the terrain roughness in A.B.L. The simulations of wind speeds and pressures in the boundary layer of the air moving at the surface of the earth are based on vertical profile of the mean speeds, turbulence intensity, spectral power and histograms of the rec...