ReabOp - Optimization of documentation workflows in the rehabilitation of built structures

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Publications

Assessing the influence of material and geometrical uncertainty on the mechanical behavior of functionally graded material plates

Publication . Carvalho, Alda; Silva, Tiago; Loja, Amélia; Damásio, Fábio Raimundo

Composite materials possessing a functional gradient are becoming strong candidates to enhance the performance of structures when severe operating conditions are a reality. These types of conditions may, for example, range from situations where a high thermal gradient is present to others where it is imperative to minimize abrupt stresses transitions between material interfaces. The manufacturing achievement of the gradients determined for a specific application may in practice face some limitations, which can be due, among other factors, to technological process constraints, eventual operating condition deterioration of production stages, or to nonconforming raw materials. Regardless of the origin of such limitations, the reality is that the uncertainty is always present to some extent; this is clearly reflected in the scattering of material and geometrical properties of these composites. The understanding that deterministic analyses are not enough to provide a complete prediction of the composite structures’ behavior emphasizes the crucial need to identify the effects that the variability in material and geometrical parameters will produce in the structural response.With the presentwork, one intends to study the influence of this variability in the static and free vibrations behavior of functionally graded plates. It is also an objective of this study to use regression models to predict these responses and to characterize the contribution of each model parameter to the explanation of the response variability. To this purpose, a set of numerical results is presented and discussed.

2016-11-03Journal article

Restricted access

Reconstruction and analysis of hybrid composite shells using meshless methods

Publication . Bernardo, G. M. S.; Loja, Amélia

The importance of focusing on the research of viable models to predict the behaviour of structures which may possess in some cases complex geometries is an issue that is growing in different scientific areas, ranging from the civil and mechanical engineering to the architecture or biomedical devices fields. In these cases, the research effort to find an efficient approach to fit laser scanning point clouds, to the desired surface, has been increasing, leading to the possibility of modelling as-built/as-is structures and components’ features. However, combining the task of surface reconstruction and the implementation of a structural analysis model is not a trivial task. Although there are works focusing those different phases in separate, there is still an effective need to find approaches able to interconnect them in an efficient way. Therefore, achieving a representative geometric model able to be subsequently submitted to a structural analysis in a similar based platform is a fundamental step to establish an effective expeditious processing workflow. With the present work, one presents an integrated methodology based on the use of meshless approaches, to reconstruct shells described by points’ clouds, and to subsequently predict their static behaviour. These methods are highly appropriate on dealing with unstructured points clouds, as they do not need to have any specific spatial or geometric requirement when implemented, depending only on the distance between the points. Details on the formulation, and a set of illustrative examples focusing the reconstruction of cylindrical and double-curvature shells, and its further analysis, are presented.

2017-06Journal article

Open access

On the characterization of parametric uncertainty on FGM plates

Publication . Damásio, Fábio R.; Silva, Tiago A. N.; Carvalho, Alda; Loja, Amélia

Composite materials with their intrinsic tailor-made capabilities can be strong candidates to improve the mechanical performance of structures, either by partially or totally replacing other traditional materials. These easily tailored features can be thought not only in terms of the more often used fibre reinforced laminated composites but also in the context of particulate composites. In general, the mechanical performance of composite structures can be, intentionally or not, influenced through the manipulation of geometric properties, the selection of material’s phases and its disposition in the composite, as well as, the spatial distribution of reinforcement agents, such as fibres or particles. The uncertainty associated to all these diferente aspects can be considered as the main source of variability to the mechanical behaviour of a given structure. It is therefore important to characterize the relations between the geometric and material parameters and a set of some relevant structural responses. The quantification of uncertainty is often related to the experimental behaviour of a given structure, although it can also be assessed within the design perspective, where it is useful to understand and identify the parameters with a greater influence on the uncertainty associated to the model simulations. In the present work, one considers functionally graded plates, where different material and geometric characteristics are assumed to be uncertain. The mechanical behaviour of such plates is modelled using Lagrange- and Kriging-based finite element models, developed according to the assumptions of the first order shear deformation theory. A set of numerical results is presented and discussed in order to identify the most significant modelling parameters for the description of the output variability, in this case the maximum deflection.

2015Conference object

Restricted access

Optimization of desalination heat exchanger`s geometries using bat-inspired techniques

Publication . Costa, D. M. S.; Trindade, J. M. F.; Loja, Amélia

In many regions of the world there are persisting situations of lack of potable water with the well-known consequences in population’s daily life, where a poverty logic loop seems to be definitely installed. In some of those regions, where seawater and solar energy resources are abundant, the use of this kind of energy may be an effective alternative to consider for seawater desalination. Falling film evaporators allow high heat transfer rates and are an important key to achieve greater efficiencies throughout several industries. Desalination systems, especially when driven by renewable energies, tend to be highly dependent of appropriate efficiencies. In order to study this matter, a meta-heuristic optimization of a desalination model of this kind is done, focusing on some design variables of the evaporator’s geometry. Because of the context of the present work, the achievement of an optimal solution, from the global heat transfer perspective is a particularly important objective. To enable this optimization study, different implementations of bat-inspired optimization technique will be considered, aiming at the minimization and maximization of the falling film heat transfer coefficient, within a desalination model, based on a horizontal falling film evaporator. A parametric study concerning the heat exchangers’ selected design variables will be carried out and discussed, along with an influence analysis ofother optimization parameters.

2015-03Conference object

Restricted access

Reconstruction of surfaces from unstructured points clouds, using compactly-supported radial basis functions

Publication . Bernardo, G. M. S.; Loja, Amélia

The need for a relevant viable approach to fit point clouds obtained by 3D laser scanning, to a desirable surface, has been object ofa substantial research effort and progresso in the past two decades in a wide range of scientific and technological fields. However, this task is far from being a trivial task. First, because of the randomness of the sampled points obtained, which in most cases count with additional noise points. Secondly, in point clouds it is frequent to find lacks ofdata, leading to the existence ofholes in the surface. As far as it is possible to know, all the methods used to achieve the fitting surfaces, present diferente undesirable behaviours, under different conditions. In the present work we present a hybrid method to reconstruct the surfaces associated to synthetic point clouds randomly generated. Parametric studies are carried out to illustrate and characterize the performance ofthe different techniques implemented..

2015-03Conference object

Restricted access