Damage assessment on building structures subjected to the recent near-fault earthquake in Lorca (Spain)

The city of Lorca (Spain) was hit on May 11th 2011 by two consecutive earthquakes with 4.6 and 5.2 Mw respectively, causing casualties and important damage in buildings. Lorca is located in the south-east region of Spain and settled on the trace of the Murcia-Totana-Lorca fault. Although the magnitudes of these ground motions were not severe, the damage observed was considerable over a great amount of buildings. More than 300 of them have been demolished and many others are being retrofitted. This paper reports a field study on the damage caused by these earthquakes. The observed damage is related with the structural typology. Further, prototypes of the damaged buildings are idealized with nonlinear numerical models and their seismic behavior and proneness to damage concentration is further investigated through dynamic response analyses.

A hierarchical strategy for real-time tracking on-board UAVs

In this paper, we present a real-time tracking strategy based on direct methods for tracking tasks on-board UAVs, that is able to overcome problems posed by the challenging conditions of the task: e.g. constant vibrations, fast 3D changes, and limited capacity on-board. The vast majority of approaches make use of feature-based methods to track objects. Nonetheless, in this paper we show that although some of these feature-based solutions are faster, direct methods can be more robust under fast 3D motions (fast changes in position), some changes in appearance, constant vibrations (without requiring any specific hardware or software for video stabilization), and situations where part of the object to track is out the field of view of the camera. The performance of the proposed strategy is evaluated with images from real-flight tests using different evaluation mechanisms (e.g. accurate position estimation using a Vicon sytem). Results show that our tracking strategy performs better than well known feature-based algorithms and well known configurations of direct methods, and that the recovered data is robust enough for vision-in-the-loop tasks.

Instabilities in two-liquid layers subject to a horizontal temperature gradient

We study theoretically the stability of two superposed fluid layers heated laterally. The fluids are supposed to be immiscible, the interface undeformable and of infinite horizontal extension. Combined thermocapillary and buoyancy forces give rise to a basic flow when a temperature difference is applied. The calculations are performed for a melt of GaAs under a layer of molten B2 O3 , a configuration of considerable technological importance. Four dif- ferent flow patterns and five temperature configurations are found for the basic state in this system. A linear stability analysis shows that the basic state may be destabilized by oscilla- tory motions leading to the so-called hydrothermal waves. Depending on the relative height of the two layers these hydrothermal waves propagate parallel or perpendicular to the temperature gradient. This analysis reveals that these perturbations can alter significantly the liquid flow in the liquid-encapsulated crystal growth techniques.

An evaluation of seismic hazard in La Hispaniola, after the 2010 Haiti earthquake

An evaluation of the seismic hazard in La Hispaniola Island has been carried out, as part of the cooperative project SISMO-HAITI, supported by the Technical University of Madrid (UPM) and developed by several Spanish Universities, the National Observatory of Environment and Vulnerability) ONEV of Haiti, and with contributions from the Puerto Rico Seismic Network (PRSN) and University Seismological Institute of Dominican Republic (ISU). The study was aimed at obtaining results suitable for seismic design purposes. It started with the elaboration of a seismic catalogue for the Hispaniola Island, requiring an exhaustive revision of data reported by more than 20 seismic agencies, apart from these from the PRSN and ISU. The final catalogue contains 96 historical earthquakes and 1690 instrumental events, and it was homogenized to moment magnitude, Mw. Seismotectonic models proposed for the region were revised and a new regional zonation was proposed, taking into account geological andtectonic data, seismicity, focal mechanisms, and GPS observations. In parallel, attenuation models for subduction and crustal zones were revised in previous projects and the most suitable for the Caribbean plate were selected. Then, a seismic hazard analysis was developed in terms of peak ground acceleration, PGA, and spectral accelerations, SA (T), for periods of 0.1, 0.2, 0.5, 1 and 2s, using the Probabilistic Seismic Hazard Assessment (PSHA) methodology. As a result, different hazard maps were obtained for the quoted parameters, together with Uniform Hazard Spectra for Port au Prince and the main cities in the country. Hazard deaggregation was also carried out in these towns, for the target motion given by the PGA and SA (1s) obtained for return periods of 475, 975 and 2475 years. Therefore, the controlling earthquakes for short- and long-period target motions were derived. This study was started a few months after the 2010 earthquake, as a response to an aid request from the Haitian government to the UPM, and the results are available for the definition of the first building code in Haiti.

Direct estimation wave setup as a medium level in swash

The extreme runup is a key parameter for a shore risk analysis in which the accurate and quantitative estimation of the upper limit reached by waves is essential. Runup can be better approximated by splitting the setup and swash semi-amplitude contributions. In an experimental study recording setup becomes difficult due to infragravity motions within the surf zone, hence, it would be desirable to measure the setup with available methodologies and devices. In this research, an analysis is made of evaluated the convenience of direct estimation setup as the medium level in the swash zone for experimental runup analysis through a physical model. A physical mobile bed model was setup in a wave flume at the Laboratory for Maritime Experimentation of CEDEX. The wave flume is 36 metres long, 6.5 metres wide and 1.3 metres high. The physical model was designed to cover a reasonable range of parameters, three different slopes (1/50, 1/30 and 1/20), two sand grain sizes (D50 = 0.12 mm and 0.70 mm) and a range for the Iribarren number in deep water (��0) from 0.1 to 0.6. Best formulations were chosen for estimating a theoretical setup in the physical model application. Once theoretical setup had been obtained, a comparison was made with an estimation of the setup directly as a medium level of the oscillation in swash usually considered in extreme runup analyses. A good correlation was noted between both theoretical and time-averaging setup and a relation is proposed. Extreme runup is analysed through the sum of setup and semi-amplitude of swash. An equation is proposed that could be applied in strong foreshore slope-dependent reflective beaches.

Highly correlated ab initio study of the far infrared spectra of methyl acetate

Highly correlated ab initio calculations (CCSD(T)) are used to compute gas phase spectroscopic parameters of three isotopologues of the methyl acetate (CH3COOCH3, CD3COOCH3, and CH3COOCD3), searching to help experimental assignments and astrophysical detections. The molecule shows two conformers cis and trans separated by a barrier of 4457 cm���1. The potential energy surface presents 18 minima that intertransform through three internal rotation motions. To analyze the far infrared spectrum at low temperatures, a three-dimensional Hamiltonian is solved variationally. The two methyl torsion barriers are calculated to be 99.2 cm���1 (C���CH3) and 413.1 cm���1 (O���CH3), for the cis-conformer. The three fundamental torsional band centers of CH3COOCH3 are predicted to lie at 63.7 cm���1 (C���CH3), 136.1 cm���1 (O���CH3), and 175.8 cm���1 (C���O torsion) providing torsional state separations. For the 27 vibrational modes, anharmonic fundamentals and rovibrational parameters are provided. Computed parameters are compared with those fitted using experimental data.

Computational Study of the Fe(CN)(2)CO Cofactor and Its Binding to HypC Protein.

In the intricate maturation process of [NiFe]-hydrogenases, the Fe(CN)2CO cofactor is first assembled in a HypCD complex with iron coordinated by cysteines from both proteins and CO is added after ligation of cyanides. The small accessory protein HypC is known to play a role in delivering the cofactor needed for assembling the hydrogenase active site. However, the chemical nature of the Fe(CN)2CO moiety and the stability of the cofactor���HypC complex are open questions. In this work, we address geometries, properties, and the nature of bonding of all chemical species involved in formation and binding of the cofactor by means of quantum calculations. We also study the influence of environmental effects and binding to cysteines on vibrational frequencies of stretching modes of CO and CN used to detect the presence of Fe(CN)2CO. Carbon monoxide is found to be much more sensitive to sulfur binding and the polarity of the medium than cyanides. The stability of the HypC���cofactor complex is analyzed by means of molecular dynamics simulation of cofactor-free and cofactor-bound forms of HypC. The results show that HypC is stable enough to carry the cofactor, but since its binding cysteine is located at the N-terminal unstructured tail, it presents large motions in solution, which suggests the need for a guiding interaction to achieve delivery of the cofactor.

A vision-based strategy for autonomous aerial refueling tasks

Autonomous aerial refueling is a key enabling technology for both manned and unmanned aircraft where extended flight duration or range are required. The results presented within this paper offer one potential vision-based sensing solution, together with a unique test environment. A hierarchical visual tracking algorithm based on direct methods is proposed and developed for the purposes of tracking a drogue during the capture stage of autonomous aerial refueling, and of estimating its 3D position. Intended to be applied in real time to a video stream from a single monocular camera mounted on the receiver aircraft, the algorithm is shown to be highly robust, and capable of tracking large, rapid drogue motions within the frame of reference. The proposed strategy has been tested using a complex robotic testbed and with actual flight hardware consisting of a full size probe and drogue. Results show that the vision tracking algorithm can detect and track the drogue at real-time frame rates of more than thirty frames per second, obtaining a robust position estimation even with strong motions and multiple occlusions of the drogue.

A Hierarchical Tracking Strategy for Vision-Based Applications On-Board UAVs

In this paper, we apply a hierarchical tracking strategy of planar objects (or that can be assumed to be planar) that is based on direct methods for vision-based applications on-board UAVs. The use of this tracking strategy allows to achieve the tasks at real-time frame rates and to overcome problems posed by the challenging conditions of the tasks: e.g. constant vibrations, fast 3D changes, or limited capacity on-board. The vast majority of approaches make use of feature-based methods to track objects. Nonetheless, in this paper we show that although some of these feature-based solutions are faster, direct methods can be more robust under fast 3D motions (fast changes in position), some changes in appearance, constant vibrations (without requiring any specific hardware or software for video stabilization), and situations in which part of the object to track is outside of the field of view of the camera. The performance of the proposed tracking strategy on-board UAVs is evaluated with images from realflight tests using manually-generated ground truth information, accurate position estimation using a Vicon system, and also with simulated data from a simulation environment. Results show that the hierarchical tracking strategy performs better than wellknown feature-based algorithms and well-known configurations of direct methods, and that its performance is robust enough for vision-in-the-loop tasks, e.g. for vision-based landing tasks.

Numerical and experimental study of the parametric rolling of a fisihing vessel in regular head waves

The dynamic behaviour of a fishing vessel in waves is studied in order to reveal its parametric rolling characteristics. This paper presents experimental and numerical results in longitudinal regular waves. The experimental results are compared against the results of a time-domain non-linear strip theory model of ship motions in six degrees-of-freedom. These results contribute to the validation of the parametric rolling prediction method, so that it can be used as an assessment tool to evaluate both the susceptibility and severity of occurrence of parametric rolling at the early design stage of these types of vessels.

Registration and fusion of contrast-enhanced MRI myocardial substrate maps and X-ray angiograms

The aim of this work is to provide the necessary methods to register and fuse the endo-epicardial signal intensity (SI) maps extracted from contrast-enhanced magnetic resonance imaging (ceMRI) with X-ray coronary ngiograms using an intrinsic registrationbased algorithm to help pre-planning and guidance of catheterization procedures. Fusion of angiograms with SI maps was treated as a 2D-3D pose estimation, where each image point is projected to a Pl��cker line, and the screw representation for rigid motions is minimized using a gradient descent method. The resultant transformation is applied to the SI map that is then projected and fused on each angiogram. The proposed method was tested in clinical datasets from 6 patients with prior myocardial infarction. The registration procedure is optionally combined with an iterative closest point algorithm (ICP) that aligns the ventricular contours segmented from two ventriculograms.

On-road visual vehicle tracking using Markov chain Monte Carlo with metropolis sampling

In this study, a method for vehicle tracking through video analysis based on Markov chain Monte Carlo (MCMC) particle filtering with metropolis sampling is proposed. The method handles multiple targets with low computational requirements and is, therefore, ideally suited for advanced-driver assistance systems that involve real-time operation. The method exploits the removed perspective domain given by inverse perspective mapping (IPM) to define a fast and efficient likelihood model. Additionally, the method encompasses an interaction model using Markov Random Fields (MRF) that allows treatment of dependencies between the motions of targets. The proposed method is tested in highway sequences and compared to state-of-the-art methods for vehicle tracking, i.e., independent target tracking with Kalman filtering (KF) and joint tracking with particle filtering. The results showed fewer tracking failures using the proposed method.

Fishing effort control regulations influence on stability, safety and operability of small fishing vessels: study of a series of stability related accidents occurred in Spain between 2004 and 2007

Entre los a��os 2004 y 2007 se hundieron por problemas de estabilidad cinco pesqueros espa��oles de peque��a eslora, de caracter��sticas parecidas, de relativamente poca edad, que hab��an sido construidos en un intervalo de pocos a��os. La mayor��a de los tripulantes de esos pesqueros fallecieron o desaparecieron en esos accidentes. Este conjunto de accidentes tuvo bastante repercusi��n social y medi��tica. Entre ingenieros navales y marinos del sector de la pesca se relacion�� estos accidentes con los condicionantes a los dise��os de los pesqueros impuestos por la normativa de control de esfuerzo pesquero. Los accidentes fueron investigados y publicados sus correspondientes informes; en ellos no se explor�� esta supuesta relaci��n. Esta tesis pretende investigar la relaci��n entre esos accidentes y los cambios de la normativa de esfuerzo pesquero. En la introducci��n se expone la normativa de control de esfuerzo pesquero analizada, se presentan datos sobre la estructura de la flota pesquera en Espa��a y su accidentalidad, y se detallan los criterios de estabilidad manejados durante el trabajo, explicando su relaci��n con la seguridad de los pesqueros. Seguidamente se realiza un an��lisis estad��stico de la siniestralidad en el sector de la pesca para establecer si el conjunto de accidentes estudiados supone una anomal��a, o si por el contrario el conjunto de estos accidentes no es relevante desde el punto de vista estad��stico. Se analiza la siniestralidad a partir de diversas bases de datos de buques pesqueros en Espa��a y se concluye que el conjunto de accidentes estudiados supone una anomal��a estad��stica, ya que la probabilidad de ocurrencia de los cinco sucesos es muy baja considerando la frecuencia estimada de p��rdidas de buques por estabilidad en el subsector de la flota pesquera en el que se encuadran los cinco buques perdidos. A continuaci��n el trabajo se centra en la comparaci��n de los buques accidentados con los buques pesqueros dados de baja para construir aquellos, seg��n exige la normativa de control de esfuerzo pesquero; a estos ��ltimos buques nos referiremos como ���predecesores��� de los buques accidentados. Se comparan las dimensiones principales de cada buque y de su predecesor, resultando que los buques accidentados comparten caracter��sticas de dise��o comunes que son sensiblemente diferentes en los buques predecesores, y enlazando dichas caracter��sticas de dise��o con los requisitos de la nueva normativa de control del esfuerzo pesquero bajo la que se construyeron estos barcos. Ello permite establecer una relaci��n entre los accidentes y el mencionado cambio normativo. A continuaci��n se compara el margen con que se cumpl��an los criterios reglamentarios de estabilidad entre los buques accidentados y los predecesores, encontr��ndose que en cuatro de los cinco casos los predecesores cumpl��an los criterios de estabilidad con mayor holgura que los buques accidentados. Los resultados obtenidos en este punto permiten establecer una relaci��n entre el cambio de normativa de esfuerzo pesquero y la estabilidad de los buques. Los cinco buques accidentados cumpl��an con los criterios reglamentarios de estabilidad en vigor, lo que cuestiona la relaci��n entre esos criterios y la seguridad. Por ello se extiende la comparativa entre pesqueros a dos nuevos campos relacionados con la estabilidad y la seguridad delos buques: ��� Movimientos a bordo (operatividad del buque), y ��� Criterios de estabilidad en condiciones meteorol��gicas adversas El estudio de la operatividad muestra que los buques accidentados ten��an, en general, una mayor operatividad que sus predecesores, contrariamente a lo que suced��a con el cumplimiento de los criterios reglamentarios de estabilidad. Por ��ltimo, se comprueba el desempe��o de los diez buques en dos criterios espec��ficos de estabilidad en caso de mal tiempo: el criterio IMO de viento y balance intenso, y un criterio de estabilidad de nueva generaci��n, incluyendo la contribuci��n original del autor de considerar agua en cubierta. Las tendencias observadas en estas dos comparativas son opuestas, lo que permite cuestionar la validez del ��ltimo criterio sin un control exhaustivo de los par��metros de su formulaci��n, poniendo de manifiesto la necesidad de m��s investigaciones sobre ese criterio antes de su adopci��n para uso regulatorio. El conjunto de estos resultados permite obtener una serie de conclusiones en la comparativa entre ambos conjuntos de buques pesqueros. Si bien los resultados de este trabajo no muestran que la aprobaci��n de la nueva normativa de esfuerzo pesquero haya significado una merma general de seguridad en sectores enteros de la flota pesquera, s�� se concluye que permiti�� que algunos dise��os de buques pesqueros, posiblemente en busca de la mayor eficiencia compatible con dicha normativa, quedaran con una estabilidad precaria, poniendo de manifiesto que la relaci��n entre seguridad y criterios de estabilidad no es un��voca, y la necesidad de que ��stos evolucionen y se adapten a los nuevos dise��os de buques pesqueros para continuar garantizando su seguridad. Tambi��n se concluye que la estabilidad es un aspecto transversal del dise��o de los buques, por lo que cualquier reforma normativa que afecte al dise��o de los pesqueros o su forma de operar deber��a estar sujeta a evaluaci��n por parte de las autoridades responsables de la seguridad mar��tima con car��cter previo a su aprobaci��n. ABSTRACT Between 2004 and 2007 five small Spanish fishing vessels sank in stability related accidents. These vessels had similar characteristics, had relatively short age, and had been built in a period of a few years. Most crewmembers of these five vessels died or disappeared in those accidents. This set of accidents had significant social and media impact. Among naval architects and seamen of the fishing sector these accidents were related to the design constraints imposed by the fishing control effort regulations. The accidents were investigated and the official reports issued; this alleged relationship was not explored. This thesis aims to investigate the relationship between those accidents and changes in fishing effort control regulations. In the introduction, the fishing effort control regulation is exposed, data of the Spanish fishing fleet structure and its accident rates are presented, and stability criteria dealt with in this work are explained, detailing its relationship with fishing vessel safety. A statistical analysis of the accident rates in the fishing sector in Spain is performed afterwards. The objective is determining whether the set of accidents studied constitute an anomaly or, on the contrary, they are not statistically relevant. Fishing vessels accident rates is analyzed from several fishing vessel databases in Spain. It is concluded that the set of studied accidents is statistically relevant, as the probability of occurrence of the five happenings is extremely low, considering the loss rates in the subsector of the Spanish fishing fleet where the studied vessels are fitted within. From this point the thesis focuses in comparing the vessels lost and the vessels that were decommissioned to build them as required by the fishing effort control regulation; these vessels will be referred to as ���predecessors��� of the sunk vessels. The main dimensions between each lost vessel and her predecessor are compared, leading to the conclusion that the lost vessels share design characteristics which are sensibly different from the predecessors, and linking these design characteristics with the requirements imposed by the new fishing control effort regulations. This allows establishing a relationship between the accidents and this regulation change. Then the margin in fulfilling the regulatory stability criteria among the vessels is compared, resulting, in four of the five cases, that predecessors meet the stability criteria with greater clearance than the sunk vessels. The results obtained at this point would establish a relationship between the change of fishing effort control regulation and the stability of vessels. The five lost vessels complied with the stability criteria in force, so the relation between these criteria and safety is put in question. Consequently, the comparison among vessels is extended to other fields related to safety and stability: ��� Motions onboard (operability), and ��� Specific stability criteria in rough weather The operability study shows that the lost vessels had in general greater operability than their predecessors, just the opposite as when comparing stability criteria. Finally, performance under specific rough weather stability criteria is checked. The criteria studied are the IMO Weather Criterion, and one of the 2nd generation stability criteria under development by IMO considering in this last case the presence of water on deck, which is an original contribution by the author. The observed trends in these two cases are opposite, allowing to put into question the last criterion validity without an exhaustive control of its formulation parameters; indicating that further research might be necessary before using it for regulatory purposes. The analysis of this set of results leads to some conclusions when comparing both groups of fishing vessels. While the results obtained are not conclusive in the sense that the entry into force of a new fishing effort control in 1998 caused a generalized safety reduction in whole sectors of the Spanish fishing fleet, it can be concluded that it opened the door for some vessel designs resulting with precarious stability. This evidences that the relation between safety and stability criteria is not univocal, so stability criteria needs to evolve for adapting to new fishing vessels designs so their safety is still guaranteed. It is also concluded that stability is a transversal aspect to ship design and operability, implying that any legislative reform affecting ship design or operating modes should be subjected to assessing by the authorities responsible for marine safety before being adopted.

Jovian Capture of a Spacecraft with a Self-Balanced Electrodynamic Bare Tether

This paper proposes and analyzes the use of a nonrotating tethered system for a direct capture in Jovian orbit using the electrodynamic force generated along the cable. A detailed dynamical model is developed showing a strong gravitational and electrodynamic coupling between the center of mass and the attitude motions. This paper shows the feasibility of a direct capture in Jovian orbit of a rigid tethered system preventing the tether from rotating. Additional mechanical���thermal requirements are explored, and preliminary operational limits are defined to complete the maneuver. In particular, to ensure that the system remains nonrotating, a nominal attitude profile for a self-balanced electrodynamic tether is proposed, as well as a simple feedback control.

Hydrodynamic forces on heave plates for offshore systems oscillating close to the seabed or the free surface

La energ��a e��lica marina es uno de los recursos energ��ticos con mayor proyecci��n pudiendo contribuir a reducir el consumo de combustibles f��siles y a cubrir la demanda de energ��a en todo el mundo. El concepto de aerogenerador marino est�� basado en estructuras fijas como jackets o en plataformas flotantes, ya sea una semisumergible o una TLP. Se espera que la energ��a e��lica offshore juegue un papel importante en el perfil de producci��n energ��tica de los pr��ximos a��os; por tanto, las turbinas e��licas deben hacerse m��s fables y rentables para ser competitivas frente a otras fuentes de energ��a. Las estructuras flotantes pueden experimentar movimientos resonantes en estados de la mar con largos per��odos de oleaje. Estos movimientos disminuyen su operatividad y pueden causar da��os en los componentes el��ctricos de las turbinas y en las palas, tambi��n en los risers y moorings. La respuesta de la componente vertical del movimiento puede reducirse mediante diferentes actuaciones: (1) aumentando la amortiguaci��n del sistema, (2) manteniendo el per��odo del movimiento vertical fuera del rango de la energ��a de la ola, y (3) reduciendo las fuerzas de excitaci��n verticales. Un ejemplo t��pico para llevar a cabo esta reducci��n son las "Heave Plates". Las heave plates son placas que se utilizan en la industria offshore debido a sus caracter��sticas hidrodin��micas, ya que aumentan la masa a��adida y la amortiguaci��n del sistema. En un an��lisis hidrodin��mico convencional, se considera una estructura sometida a un oleaje con determinadas caracter��sticas y se eval��an las cargas lineales usando la teor��a potencial. El amortiguamiento viscoso, que juega un papel crucial en la respuesta en resonancia del sistema, es un dato de entrada para el an��lisis. La tesis se centra principalmente en la predicci��n del amortiguamiento viscoso y de la masa a��adida de las heave plates usadas en las turbinas e��licas flotantes. En los c��lculos, las fuerzas hidrodin��micas se han obtenido con el f n de estudiar c��mo los coeficientes hidrodin��micos de masa a��adida5 y amortiguamiento var��an con el n��mero de KC, que caracteriza la amplitud del movimiento respecto al di��metro del disco. Por otra parte, se ha investigado la influencia de la distancia media de la ���heave plate��� a la superficie libre o al fondo del mar, sobre los coeficientes hidrodin��micos. En este proceso, un nuevo modelo que describe el trabajo realizado por la amortiguaci��n en funci��n de la enstrof��a, es descrito en el presente documento. Este nuevo enfoque es capaz de proporcionar una correlaci��n directa entre el desprendimiento local de vorticidad y la fuerza de amortiguaci��n global. El an��lisis tambi��n incluye el estudio de los efectos de la geometr��a de la heave plate, y examina la sensibilidad de los coeficientes hidrodin��micos al incluir porosidad en ��sta. Un dise��o novedoso de una heave plate, basado en la teor��a fractal, tambi��n fue analizado experimentalmente y comparado con datos experimentales obtenidos por otros autores. Para la resoluci��n de las ecuaciones de Navier Stokes se ha usado un solver basado en el m��todo de vol��menes finitos. El solver usa las librer��as de OpenFOAM (Open source Field Operation And Manipulation), para resolver un problema multif��sico e incompresible, usando la t��cnica VOF (volume of fluid) que permite capturar el movimiento de la superficie libre. Los resultados num��ricos han sido comparados con resultados experimentales llevados a cabo en el Canal del Ensayos Hidrodin��micos (CEHINAV) de la Universidad Polit��cnica de Madrid y en el Canal de Experiencias Hidrodin��micas (CEHIPAR) en Madrid, al igual que con otros experimentos realizados en la Escuela de Ingenier��a Mec��nica de la Universidad de Western Australia. Los principales resultados se presentan a continuaci��n: 1. Para peque��os valores de KC, los coeficientes hidrodin��micos de masa a��adida y amortiguamiento incrementan su valor a medida que el disco se aproxima al fondo marino. Para los casos cuando el disco oscila cerca de la superficie libre, la dependencia de los coeficientes hidrodin��micos es m��s fuerte por la influencia del movimiento de la superficie libre. 2. Los casos analizados muestran la existencia de un valor cr��tico de KC, donde la tendencia de los coeficientes hidrodin��micos se ve alterada. Dicho valor cr��tico depende de la distancia al fondo marino o a la superficie libre. 3. El comportamiento f��sico del flujo, para valores de KC cercanos a su valor cr��tico ha sido estudiado mediante el an��lisis del campo de vorticidad. 4. Introducir porosidad al disco, reduce la masa a��adida para los valores de KC estudiados, pero se ha encontrado que la porosidad incrementa el valor del coeficiente de amortiguamiento cuando se incrementa la amplitud del movimiento, logrando un m��ximo de damping para un disco con 10% de porosidad. 5. Los resultados num��ricos y experimentales para los discos con fald��n, muestran que usar este tipo de geometr��as incrementa la masa a��adida cuando se compara con el disco s��lido, pero reduce considerablemente el coeficiente de amortiguamiento. 6. Un dise��o novedoso de heave plate basado en la teor��a fractal ha sido experimentalmente estudiado a diferentes calados y comparado con datos experimentales obtenidos por otro autores. Los resultados muestran un comportamiento incierto de los coeficientes y por tanto este dise��o deber��a ser estudiado m��s a fondo. ABSTRACT Offshore wind energy is one of the promising resources which can reduce the fossil fuel energy consumption and cover worldwide energy demands. Offshore wind turbine concepts are based on either a fixed structure as a jacket or a floating offshore platform like a semisubmersible, spar or tension leg platform. Floating offshore wind turbines have the potential to be an important part of the energy production profile in the coming years. In order to accomplish this wind integration, these wind turbines need to be made more reliable and cost efficient to be competitive with other sources of energy. Floating offshore artifacts, such oil rings and wind turbines, may experience resonant heave motions in sea states with long peak periods. These heave resonances may increase the system downtime and cause damage on the system components and as well as on risers and mooring systems. The heave resonant response may be reduced by different means: (1) increasing the damping of the system, (2) keeping the natural heave period outside the range of the wave energy, and (3) reducing the heave excitation forces. A typical example to accomplish this reduction are ���Heave Plates���. Heave plates are used in the offshore industry due to their hydrodynamic characteristics, i.e., increased added mass and damping. Conventional offshore hydrodynamic analysis considers a structure in waves, and evaluates the linear and nonlinear loads using potential theory. Viscous damping, which is expected to play a crucial role in the resonant response, is an empirical input to the analysis, and is not explicitly calculated. The present research has been mainly focused on the prediction of viscous damping and added mass of floating offshore wind turbine heave plates. In the calculations, the hydrodynamic forces have been measured in order to compute how the hydrodynamic coefficients of added mass1 and damping vary with the KC number, which characterises the amplitude of heave motion relative to the diameter of the disc. In addition, the influence on the hydrodynamic coefficients when the heave plate is oscillating close to the free surface or the seabed has been investigated. In this process, a new model describing the work done by damping in terms of the flow enstrophy, is described herein. This new approach is able to provide a direct correlation between the local vortex shedding processes and the global damping force. The analysis also includes the study of different edges geometry, and examines the sensitivity of the damping and added mass coefficients to the porosity of the plate. A novel porous heave plate based on fractal theory has also been proposed, tested experimentally and compared with experimental data obtained by other authors for plates with similar porosity. A numerical solver of Navier Stokes equations, based on the finite volume technique has been applied. It uses the open-source libraries of OpenFOAM (Open source Field Operation And Manipulation), to solve 2 incompressible, isothermal immiscible fluids using a VOF (volume of fluid) phase-fraction based interface capturing approach, with optional mesh motion and mesh topology changes including adaptive re-meshing. Numerical results have been compared with experiments conducted at Technical University of Madrid (CEHINAV) and CEHIPAR model basins in Madrid and with others performed at School of Mechanical Engineering in The University of Western Australia. A brief summary of main results are presented below: 1. At low KC numbers, a systematic increase in added mass and damping, corresponding to an increase in the seabed proximity, is observed. Specifically, for the cases when the heave plate is oscillating closer to the free surface, the dependence of the hydrodynamic coefficients is strongly influenced by the free surface. 2. As seen in experiments, a critical KC, where the linear trend of the hydrodynamic coefficients with KC is disrupted and that depends on the seabed or free surface distance, has been found. 3. The physical behavior of the flow around the critical KC has been explained through an analysis of the flow vorticity field. 4. The porosity of the heave plates reduces the added mass for the studied porosity at all KC numbers, but the porous heave plates are found to increase the damping coefficient with increasing amplitude of oscillation, achieving a maximum damping coefficient for the heave plate with 10% porosity in the entire KC range. 5. Another concept taken into account in this work has been the heave plates with flaps. Numerical and experimental results show that using discs with flaps will increase added mass when compared to the plain plate but may also significantly reduce damping. 6. A novel heave plate design based on fractal theory has tested experimentally for different submergences and compared with experimental data obtained by other authors for porous plates. Results show an unclear behavior in the coefficients and should be studied further. Future work is necessary in order to address a series of open questions focusing on 3D effects, optimization of the heave plates shapes, etc.