Papers

The generation of unstructured triangular grids for coastal applications requires extensive manual tunning, in order to improve the stability, accuracy and efficiency of the model simulations. As current grids reach 105-106 nodes, this manual tunning is no longer feasible. This paper presents a new post-processor that aims at optimizing the local distribution of nodes and elements by adding and deleting nodes and by changing the connections between nodes. The algorithms target a smooth transition between elements sizes by making the number of connections of each internal node as close to 6 as possible.An application of the post-processor to various grids shows that the grid roughness is reduced by 10-30%, while decreasing marginally the number of nodes and maintaining the global nodal distribution. To illustrate the benefits of the post-processor, a grid with 130.000 nodes of the maritime zone under Portuguese jurisdiction is used to simulate tides with a good accuracy (root mean square errors below 10 cm) and without numericaloscillations. The model results provide an extensive database of tidal elevations that can feed boundary conditions to local estuarine models.

Avaliação do risco de incêndio em centros urbanos antigos parte I – Aplicação do método de ARICA ao centro histórico do Funchal - A diferente concepção e materiais usados nas construções antigas fazem com que estas apresentem um risco de incêndio agravado. Tendo como objectivo avaliar o risco de incêndio do centro histórico do Funchal aplicaramse os métodos de Gretener e ARICA a alguns edifícios característicos. A aplicação dos métodos permitiu não só verifi car o risco de incêndio como detectar as diferenças entre os métodos.

A diferente concepção e materiais usados nas construções antigas fazem com que estas apresentem um risco de incêndio agravado. Tendo como objectivo avaliar o risco de incêndio do centro histórico do Funchal aplicaramse os métodos de Gretener e ARICA a alguns edifícios característicos. A aplicação dos métodos permitiu não só verifi car o risco de incêndio como detectar as diferenças entre os métodos.

Summary: A Bayesian estimator with informative prior distributions (a multi-normal and an inverted gamma distribution), adequate to displacement estimation at dam monitoring net-works, is presented. The hyper-parameters of the prior distributions are obtained by Bayesian empirical methods with non-informative priors. The performances of the Bayes estimator and the classical generalized lest squares estimator are compared using two measurements of the horizontal monitoring network of a concrete gravity dam: the Penha Garcia dam (Portugal). In order to test the robustness of the two estimators, gross errors are added to one of the measured horizontal directions: the Bayes estimator proves to be significantly more robust than the generalized least squares estimator.

Hierarchical Bayesian regression models, with differing hyper-prior distributions, are considered as accident prediction models to be fitted on data collected over several years on the Portuguese motorway network. A sensitivity analysis is performed by way of simulation to investigate the practical implications of the choice of informative hyper-priors (Gamma, Christiansen and Uniform) and non-informative Gamma, as well as various sample sizes and years of aggregated data, on the results of a road safety analysis, in particular, at detecting high accident risk locations. It was concluded that informative hyper-priors were best at detecting hotspots when small sample sizes were considered. For bigger samples the various hyper-priors produced equivalent outcomes. Furthermore, more accurate results were obtained when more years of data were analyzed.

SUMMARY Structural health monitoring is an emergent powerful diagnostic tool that can be used to identify and to prevent possible failures of the various components that comprise an infrastructure. In a suspension bridge, the measurement of the vertical and transversal displacements plays an important role for its safety evaluation. Considering the restrictions usually found on these structures, an enhanced solution comprises a non-contact vision-based measurement system with dynamic response, accuracy and amplitude range well suited to the physical phenomenon to measure. A methodology to perform the vision system calibration is described, which can be carried out in situ, while the deck is moving, requiring little effort and a minimum set of information. The key idea is to use the factorization method to get an initial estimation of the object shape and camera’s parameters, and to incorporate the knowledge about the distances between the calibration targets in a non-linear optimization process to achieve a metric shape reconstruction and optimize the camera’s parameters estimation. Results obtained by numerical simulation experiments are reported, showing the negligible influence of noisy calibration data in the calibration performance and also the robustness of the calibration process on the camera’s parameters estimation. Tests carried out to assess the calibration and tracking of the bridge deck motion showed that, even in an environmental severely affected by noise, it is possible to measure the vertical and transversal displacements of the bridge deck with excellent levels of accuracy.

Os canais de rega são infra-estruturas hidráulicas de grande importância, que contribuem para o desenvolvimento de uma agricultura desejavelmente sustentável e para a fixação da população agrícola. O principal objetivo dos canais de rega é o transporte do maior volume de água a longas distâncias com custos de operação e manutenção o mais baixos possível. Assim, a impermeabilização dos canais de rega revela-se de uma grande importância, devendo ser cuidada a sua concepção e execução, tanto de novos canais como da reabilitação de existentes.Os principais objetivos deste artigo são: levantamento dos processos de impermeabilização ou revestimentos existentes nos canais de rega; identificação das principais anomalias verificadas nesses canais, das causas prováveis para a sua ocorrência e das técnicas de reabilitação das mesmas.

N/A

N/A

N/A