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In this work, the performance of a semicircular cylinder with the flat side parallel to the incoming flow has been studied experimentally in a wind-excited energy harvester. Preliminary sectional model wind tunnel tests have allowed the identification of the reduced velocity ranges howing appreciable wind-induced oscillations. Interestingly, vortex-induced vibration-galloping interferences have been identified for both heave and pitch degrees of freedom at low reduced wind speeds, as well as coupled galloping in the higher ranges of flow velocities. The impact on the aeroelastic response caused by the attachment of a small-diameter rod at different positions has been studied, finding an enhancement in the amplitude of the oscillations and an enlargement in the vortex-induced vibration excitation range for some of them. Based on these preliminary results, an energy harvester has been designed adopting a cantilever beam supporting the semicircular cylinder. The device has showed a good performance reaching 2.5 mW of averaged harvested power for the configuration with a small-diameter rod attached at γ=85º for 8 m/s flow speed.

[EN] One of the remaining challenges for the scientific-technical community is predicting preterm births, for which electrohysterography (EHG) has emerged as a highly sensitive prediction technique. Sample and fuzzy entropy have been used to characterize EHG signals, although they require optimizing many internal parameters. Both bubble entropy, which only requires one internal parameter, and dispersion entropy, which can detect any changes in frequency and amplitude, have been proposed to characterize biomedical signals. In this work, we attempted to determine the clinical value of these entropy measures for predicting preterm birth by analyzing their discriminatory capacity as an individual feature and their complementarity to other EHG characteristics by developing six prediction models using obstetrical data, linear and non-linear EHG features, and linear discriminant analysis using a genetic algorithm to select the features. Both dispersion and bubble entropy better discriminated between the preterm and term groups than sample, spectral, and fuzzy entropy. Entropy metrics provided complementary information to linear features, and indeed, the improvement in model performance by including other non-linear features was negligible. The best model performance obtained an F1-score of 90.1 ± 2% for testing the dataset. This model can easily be adapted to real-time applications, thereby contributing to the transferability of the EHG technique to clinical practice., This work was supported by the Spanish Ministry of Economy and Competitiveness, the European Regional Development Fund (MCIU/AEI/FEDER, UE RTI2018-094449-A-I00-AR), and by the Generalitat Valenciana (AICO/2019/220)

Shape and size design of twin-box decks involves managing a number of highly sensitive deck features, including aerodynamic, stiffness, and mass properties, which leads to important and co...

[EN] Electrohysterography (EHG) has emerged as an alternative technique to predict preterm labor, which still remains a challenge for the scientific-technical community. Based on EHG parameters, complex classification algorithms involving non-linear transformation of the input features, which clinicians found difficult to interpret, were generally used to predict preterm labor. We proposed to use genetic algorithm to identify the optimum feature subset to predict preterm labor using simple classification algorithms. A total of 203 parameters from 326 multichannel EHG recordings and obstetric data were used as input features. We designed and validated 3 base classifiers based on k-nearest neighbors, linear discriminant analysis and logistic regression, achieving F1-score of 84.63 ± 2.76%, 89.34 ± 3.5% and 86.87 ± 4.53%, respectively, for incoming new data. The results reveal that temporal, spectral and non-linear EHG parameters computed in different bandwidths from multichannel recordings provide complementary information on preterm labor prediction. We also developed an ensemble classifier that not only outperformed base classifiers but also reduced their variability, achieving an F1-score of 92.04 ± 2.97%, which is comparable with those obtained using complex classifiers. Our results suggest the feasibility of developing a preterm labor prediction system with high generalization capacity using simple easy-to-interpret classification algorithms to assist in transferring the EHG technique to clinical practice., This work was supported by the Spanish Ministry of Economy and Competitiveness, the European Regional Development Fund (MCIU/AEI/FEDER, UE RTI2018-094449-A-I00-AR) and by the Generalitat Valenciana (AICO/2019/220).

[Abstract] The wind flow around twin-box decks is particularly complex due to the very important role played by the slot distance between girders and the presence of the downwind box that is immersed in the wake of the upwind box. Detailed experimental studies on the three-dimensional flow features of this deck typology are certainly challenging, and CFD simulations have not tackled this problem so far. The goal of this 3D LES piece of research is to shed some light on the complex flow features around twin-box decks, particularly when the deck geometry is fully three-dimensional due to the presence of the transversal beams linking together the deck girders. Integral parameters, mean and instantaneous flow structures and spanwise correlations are studied for a segment of the Stonecutters Bridge. It has been found that the presence of the transversal beam plays a key role in the flow correlation loss, identifying, for instance, the out-of-phase shedding of vortices at different sides of the transversal beam. The numerical results agree well with experimental data in the literature, and offer a richer and more comprehensive explanation for the identified aerodynamic responses. This research has been funded by the Spanish Ministry of Economy and Competitiveness in the frame of the research project with reference BIA2016-76656-R and the Galician regional government with reference ED431C 2017/72. The first of the authors has been funded by the Spanish Ministry of Economy and Competitiveness in the frame of the National Program for Promotion of Talent and Employability through the BES-2014-068418 predoctoral contract grant, associated with the BIA2013-41965-P research project Xunta de Galicia; ED431C2017/72

[Abstract] In computational fluid dynamics (CFD) simulations, verification is the process of identifying both the spatial and the temporal discretisations providing relatively insensitive model results. The underlying goal of this task is to identify the mesh with a lower number of elements and the longer time step size compatible with the purposes of the study. In this manner, the computational burden associated with CFD methods may be decreased without compromising the accuracy of the numerical results. In general, this process is accomplished by studying three meshes with increasing discretisation levels (coarse, medium and fine), expecting that the medium one would provide satisfactory results. Once the satisfactory spatial discretisation level is selected, the different time step sizes are studied, taking into account that a Courant number (Co) of 1 is usually considered the maximum allowable value for numerical stability when adopting a LES (Large Eddy Simulation) approach. In this study, a detailed verification study considering two different approaches, providing the uncertainty level of several parameters of interest depending on the spatial and temporal discretisation is reported. The first of them consists in the curve fitting of linear or quadratic curves to selected model outputs; meanwhile the second approach relies on the Richardson extrapolation principle. These two different approaches are applied in the frame of the 3D LES numerical simulations of the Stonecutters bare deck geometry. In the study the focus is put on the sensitivity of the integral parameters, that is the force coefficients and Strouhal number, with the spatial and temporal discretisations. This research has been funded by the Spanish Ministry for Science and Innovation in the frame of the research project with reference PID2019-110786GB-I00 and the Galician regional Government with reference ED431C2017/72. The computations have been carried out in the computer cluster Breogan and in the Galician Supercomputing Center (CESGA) Xunta de Galicia; ED431C2017/72

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG [Abstract] An efficient method for analyzing the nonlinear aerostatic stability of long-span bridges using a modal formulation is proposed. First, a simplified linear version defined as modal-based approach is introduced, which evaluates the bridge displacements using the modal properties of the bridge and speeds up the assessment of the critical velocity by applying a root-finding algorithm. Then, this scheme is further developed to identify the instability limit point in nonlinear structures by combining nonlinear FEM analyses with the linear version of the modal-based approach and a root-finding algorithm in an outer loop. The effects of considering the three components of the wind loads, the stays sag effect, structural nonlinearities, aerodynamic nonlinearities, and the initial wind angle of attack, are analyzed and discussed. The computational advantages of the proposed method and its accuracy are demonstrated through three application examples, including a simplified linear 1 DoF system, and linear and nonlinear FEM models of a full cable-stayed bridge. The collapse mechanism of the cable-stayed bridge is driven by the stiffness degradation of the stays caused by the deck vertical upward displacements. It has been found that the influence of the nonlinear aerodynamic features is very low when the structural nonlinearities control the bridge collapse. Xunta de Galicia; ED481B2018/053 Xunta de Galicia; ED431C 2017/72 EEUU. National Science Foundation; CMMI #1562244 M. Cid Montoya is funded by the Xunta de Galicia (Galician regional government) and the Fulbright Scholar Program with reference ED481B2018/053. S. Hernández, F. Nieto, and M. Cid Montoya have been funded by the Spanish Ministry of Economy and Competitiveness in the frame of the research project with reference PID2019-110786 GB-I00, and the Xunta de Galicia, including FEDER funding, with reference ED431C 2017/72. A. Kareem especially thanks NSF for in part support under grant CMMI #1562244.

Structural optimization techniques have the potential to become a powerful tool in the design of long-span bridges. The search for more efficient and reliable designs involves considering shape variations in the deck cross-section, which is one of the key features of the bridge. This affects the deck aerodynamics and its mechanical properties, and consequently to the aeroelastic response of the bridge. A numerical approach pursuing to optimize a long-span bridge needs to explore changes in the deck shape, including structural and aeroelastic responses as design constraints. Therefore, the flutter response of the bridge must be computed numerically for every candidate proposed by the optimization algorithm. This work presents a novel approach to conduct the optimization of deck shape and cables size of a long-span cable-stayed bridge considering simultaneously aeroelastic and structural constraints. The design variables are the cross-section area and prestressing force of each stay, the deck plates thickness and the width and depth of a streamlined box deck. The aeroelastic constraint is evaluated based on the fully numerical procedure developed in an authors' previous work. A series of parameter variation studies, that are instrumental for the sound interpretation of the optimum designs, are also reported.

The classical approach currently used in the bridge engineering industry for the structural and aeroelastic design of bridges is based on an iterative heuristic process which includes wind tunnel testing. The dependency on experimental techniques for the aeroelastic characterization of the bridge deck cross-section requires a substantial amount of resources, and consequently the number of potential candidate designs must be limited. The fast improvements in Computational Fluid Dynamics (CFD) techniques in recent years have led to its use in the industrial field, and consequently bridge design methods must be updated. This paper proposes a fully numerical strategy to overcome the classical iterative process in bridge deck shape design. Firstly, it consists in constructing a surrogate model of the aerodynamic response of the baseline cross-section and the allowed shape variations by conducting a set of CFD simulations of several sample designs. Then, the force coefficients and their slopes can be obtained for every design included in the design domain, the flutter derivatives can be approximated by the quasi-steady formulation, and the flutter velocity can be computed. This procedure is applied to two cable-stayed bridges with different spans, and the reported results are validated with wind tunnel tests.

This paper presents the results of numerical and experimental investigations on the force coefficients and Strouhal numbers of circular segments considering different corner angles or chord to sagitta ratios. The research is motivated because these geometries are becoming increasingly popular in several engineering disciplines. The so-called D-section (semi-circular cylinder with a corner angle of $ 90^{\circ } $ ) has been experimentally studied in the past, since it is a galloping prone geometry. However, there is a lack of research for cases with different corner angles, and the numerical investigations related to this topic are particularly scarce. In this work, a 2D Unsteady Reynolds Averaged Navier–Stokes approach has been adopted aiming to study the circular segments at the sub-critical regime, considering corner angles from $ 40^{\circ } $ to $ 90^{\circ } $ , and the flow parallel to the rectilinear side. These sections were found to be particularly challenging since they present massive flow separation on the rectilinear side, alongside the inherent difficulties related to modeling the flow along curved surfaces at high Reynolds numbers. The impact of introducing low-Reynolds-number and curvature corrections in the $ k-\omega $ SST turbulence model and the performance of the Transition SST model have been extensively studied.

The quality of aeroelastic tests of long-span bridges is highly influenced by the ability of the reduced-scale models to reproduce the dynamic response of the real bridge. Hence, the design of the models is one important component in the process, as differences between the dynamic properties of the model and the prototype typically arise due to inherent limitations when constructing the reduced-scale model. This paper reviews the design process of full bridge reduced-scale models and explores sources of inaccuracies. A method based on optimization algorithms is proposed to reduce these inaccuracies in the model dynamic responses. This method is applied to a modified version of a real project consisting of a cable-stayed bridge with two diamond-shaped towers, single-box deck, 176 stays, and four piers. The optimization of the dynamic properties of the full bridge reduced-scale model is conducted in two phases: the first one optimizes the standalone tower, and the second one the complete bridge model. The results show the capabilities of the method, which nearly eliminates the inaccuracies in the natural frequencies of the model. The effects on other dynamic properties, such as variations in the generalized masses and in the modal shapes, are studied and commented upon.

Structures Congress 2020. 5-8 abril, 2020. St. Louis, Missouri [Abstract] This paper describes the evolution of deck shape of long span bridges since the Tacoma Narrows collapse trying to avoid undesirable aerodynamic behavior under wind flow and the trend in the last decades to increase the length of the main span of suspension and cable stayed bridges. The necessity to use advanced technologies to help the engineer to obtain the best possible design is highlighted and the advantages of applying optimization methodologies is encouraged. It is explained that this approach requires to use only numerical tools and hence to eliminate experimental studies, as wind tunnel tests using reduced models of full bridge of a segment of the deck, and their substitution by computational fluid dynamics (CFD) simulations. After doing so, the current capabilities of this approach are presented and, finally, the problems that need to be solved to have a fully operational methodology able to be implemented in real structures are outlined. This research has been funded by the Spanish Ministry of Economy and Competitiveness in the frame of the research project BIA2016-76656-R and the Galician regional government (including FEDER Funding) reference ED431C 2017/72. M. Cid Montoya has been funded by the Galician regional government (Xunta de Galicia) with reference ED481B 2018/053 and the Fulbright postdoctoral scholarship program Xunta de Galicia; ED431C 2017/72 Xunta de Galicia; ED481B 2018/053

Structures Congress 2020. 5-8 abril, 2020. St. Louis, Missouri [Abstract] Optimization techniques have demonstrated their capability to obtain economic and sustainable designs while meeting the performance and safety requirements in a number of engineering disciplines. In the bridge engineering field, the increasing main span length of super-long span bridges makes the wind-resistant design a top priority. However, it has been traditionally conducted following heuristic rules based on experimental analyses. Alternatively, the last advances in CFD and metamodeling techniques enables the development of optimization frameworks. The right conception of the aerostructural optimization problem is crucial to achieve noticeable reductions in the required amount of material and comprehensive safe designs. This paper reports the last advances in the authors’ line of research that pursues the definition of a numerical methodology for the full aerostructural optimization of long-span bridges considering shape and size design variables. The capabilities of the method are presented, and the necessity of considering uncertainty in the process is discussed. This research has been funded by the Spanish Ministry of Economy and Competitiveness in the frame of the research project with reference BIA2016-76656-R, and the Galician regional government, including FEDER funding, with reference ED431C 2017/72. M. Cid Montoya is funded by the Galician regional government with reference ED481B 2018/053 and the Fulbright postdoctoral scholarship program. A. Kareem especially thanks NSF support under grant CMMI #1612843. Fei Ding is supported by a grant from the Center for Informatics and Computational Sciences Xunta de Galicia; ED431C 2017/72 Xunta de Galicia; ED481B 2018/053 EEUU. National Sanitation Foundation (NSF); CMMI #1612843

Recent findings have shown that maximum diameter of abdominal aortic aneurysm (AAA) and its growth rate are not entirely reliable indicators of rupture potential. The AAA geometrical shape and size may be related to the rupture risk which is a clinical manifestation of the balance between the forces generated by blood flow within the AAA and its strength. This study aims at assessing the hemodynamic features associated with the geometry of AAAs.

While it is well known that the gap between twin-box decks is a key design variable that impacts the onset flutter velocity of a bridge, further research is required to ascertain how modifications in several bridge design variables affect other aeroelastic responses. This paper utilizes aero-structural optimization techniques for the design of long-span bridges with short gap twin-box decks considering simultaneously structural, flutter and buffeting constraints. The optimization helps to reduce the material volume of the structure while maintaining all the performance and safety requirements below the imposed thresholds. It has been found that the geometry of the individual box cross-section is an important feature for the control of the buffeting response, particularly the vertical acceleration. On the other hand, flutter and torsional buffeting constraints require designs with larger gap distance and alternative box geometries, leading to a trade-off between conflicting design demands. Hence, depending on the expected wind load conditions and the specific requirements of a particular project, an optimum aero-structural bridge design with a particular deck shape can be identified. The framework presented in this study is an effective tool to achieve sustainable and safe bridge designs that seeks a most efficient balance between all the design constraints.

The design of long-span bridges under wind places multiple demands that are frequently contradictory in regard to the resulting deck configuration. The structural demand requires that the deck contributes to the bridge stiffness, which results in bluff geometry. Conversely, aeroelastic aspects demand that the deck shape be more streamlined to reduce the aerodynamic and aeroelastic load effects. This requires that the design of long-span bridges be carried out as an aero-structural design problem, where the goal is to obtain designs with the lowest cost that simultaneously fulfill the structural and aeroelastic constraints. This study presents a numerical framework for the aero-structural design of long-span bridges under buffeting focusing on the deck shape. In this paper, the relationship between the buffeting response of a cable-stayed bridge and its deck shape is analyzed by means of parametric studies that help to better understand the role played by each involved parameter. This information is used to tailor the deck shape aiming at keeping the buffeting response under a given threshold. By building upon this framework, the design problem can be recast as an aero-structural optimization problem.

Reliability based design optimization (RBDO) for deck shape and thicknesses of the steel plates that form a box girder of long-span suspension bridges is performed considering probabilistic flutter constraint. The entire process was carried out fully computationally including the definition of flutter derivatives. Surrogate models were constructed to estimate the aerodynamic response of the bridge for different deck shapes based on the results from a series of CFD simulations. Some of the aerodynamic coefficients were validated by wind tunnel tests. Flutter derivatives were then estimated using quasi-steady approach for the evaluation of critical flutter velocity. Uncertainty in the aerodynamic coefficients from CFD simulations as well as the extreme wind speed at the bridge site were considered. The formulated methodology was applied to the Great Belt East Bridge.

The design of long-span bridges consists of dealing with a large number of design variables and it is conditioned by responses of structural and aeroelastic nature. A deep knowledge about the influence of these variables governing the bridge responses is crucial to achieve efficient and safe designs. Apart from heuristic rules, numerical approaches, such as parameter variation studies, sensitivity analysis and optimization algorithms, can provide reliable information to improve designs. This work studies the effects on the flutter and structural responses of a cable-stayed bridge when the mechanical, mass, aerodynamic and aeroelastic properties of a streamlined mono-box deck are modified. These results are used to understand qualitatively and quantitatively the effects caused by the variation of the deck plate thickness and cross-section shape on the bridge responses.

[Abstract:] Flexible structures, such as cable-supported bridges, are prone to suffer from vortex-induced vibrations (VIV) under wind flow, as their span lengths are steadily growing in the last decades. VIV is a phenomenon that takes place at reduced wind speeds. The movements of the structure at VIV are self-limited and their frequency corresponds with the natural frequency of the structure (lock in). Therefore, VIV affects the structure’s serviceability and can cause fatigue related damage. Hence, the need for identifying and avoiding this phenomenon at the early design stages is a key issue in long-span bridges design. In the present study a rectangular cylinder of width to depth ratio 4:1, which is a common simplification of a bridge deck cross section, is analysed for the static case as well as undergoing free vibration in the vertical direction under wind flow. These analyses have been carried out by 2D URANS CFD simulations, adopting two different turbulence models: the k − ω SST, which is based upon the Boussinesq eddy-viscosity approximation, and the Reynolds Stress Model, which directly calculates the components of the specific Reynolds stresses. For the static case the force coefficients, Strouhal number and the pressure coefficient distributions were calculated and compared with the available experimental data. In the case of the free-to-oscillate 4:1 rectangular cylinder, the oscillation amplitudes are compared with wind tunnel data reported in the literature. In addition, the frequencies and phase-lags between the time-dependent lift coefficient and the vertical oscillations are studied. Ministerio de Economía y Competitividad; BIA2016-76656-R Ministerio de Economía y Competitividad; BES-2014-068418 Ministerio de Economía y Competitividad; BIA2013-41965-P Xunta de Galicia; ED431C 2017/72

Design techniques based upon sensitivity analysis are not usual in the current design of suspension bridges. However, sensitivity analysis has been proved to be a useful tool in the car and aircraft industries. Evaluation of sensitivity analysis is a mandatory step in the way towards an efficient automated optimum design process which would represent a huge jump in the conception of long span bridges. Some of the authors of this paper were pioneers in establishing a methodology for obtaining the sensitivity analysis of flutter speed in suspension bridges a few years ago. That approach was completely analytical and required the evaluation of many matrices related to the phenomenon. In those works the total mass of the deck was considered as constant and such a circumstance supposed a limitation of the method. In the present paper the complete analytical formulation of the sensitivity analysis problem in bridges considering variable deck mass is presented, as well as its application to the design problem of the Great Belt Bridge. Analytical evaluation of sensitivities is a time demanding task, and in order to avoid excessive computation times, distributed computing strategies have been implemented which can be considered as an additional benefit of this approach. For the application example, it has been found that deck cross-section area and torsional inertia are the structural properties with the greatest influence on the flutter performance.

This document describes an optimization problem of cable cross section of a cable stayed bridge considering constraints of cable stress and deck displacement. Since the bridge is still in the design phase, the geometry and the mechanical characteristics are subjected to changes. In order to avoid creating different structural models, a computer code was written to produce a model from geometrical and mechanical data and solve the optimization problem. At the end of the document, two examples are included to show the capabilities of the methodology presented.

The study of bridge responses under wind-induced loads is based upon full aeroelastic model testing or hybrid methods which use section model tests and subsequent computer analysis. Both methodologies present several strong points and some shortcomings, specially related with the visualization of the bridge dynamic behaviour. Nowadays, advances and improvements in computational power and computer aided design technologies make possible a new way towards the feasible design of long span bridges considering its aerodynamic and aeroelastic behaviour. The virtual wind tunnel (VWT) technique developed by the authors joins together accurate section model testing with computer aided design in order to obtain a detailed computer visualization of the complete bridge behaviour under wind flow. The results obtained for the Tacoma Narrows Bridge and the Messina Strait Bridge are presented.

Cable supported bridges are wind prone structures. Therefore, their aerodynamic behaviour must be studied in depth in order to guarantee their safe performance. In the last decades important achievements have been reached in the study of bridges under wind-induced actions. On the other hand, non-conventional design techniques such as sensitivity analysis or optimum design have not been applied although they have proved their feasibility in the automobile or aeronautic industries. The aim of this research work is to demonstrate how non-conventional design techniques can help designers when dealing with long span bridges considering their aeroelastic behaviour. In that respect, the comprehensive analytical optimum design problem formulation is presented. In the application example the optimum design of the challenging Messina Strait Bridge is carried out. The chosen initial design has been the year 2002 design proposal. Up to a 33% deck material saving has been obtained after finishing the optimization process.

Construction of cable supported bridges has experienced a great impulse in the past decade. Bridges having more than 800m of span length were built in France and Japan and some bridges with span length of more than 1km are going to be built, such as the Stonecuters bridge in Hong-Kong, and the Chongming in China (Fig. 1). Because of the increasing length of this class of bridges, they are becoming prone to phenomena like flutter in a similar way than long span suspension bridges. Cable stayed bridges may present a few different alternatives for the cable system. At least harp, fan or modified fan arrangements can be discussed at the beginning of the design. Also variations in the number of cable planes can be studied. Usually, during the design process changes are made by carrying out a number of analyses and using trial and error techniques relying in heuristic rules that are based upon the particular skills of the engineer. This approach can be inefficient in new problems and commonly it needs to be supported with results coming from experimental testing which makes more expensive the whole design process. Instead of that, an approach based in sensitivity analysis can be very helpful for the designer.

The morphology of abdominal aortic aneurysms (AAA) has been recognized as a factor that may predispose their rupture. The time variation of the AAA morphology induces hemodynamic changes in morphological behavior that, in turn, alters the distribution of hemodynamic stress on the arterial wall. This behavior can influence the phenomenon of rupture. In order to evaluate the relationship between the main geometric parameters characterizing the AAA and the hemodynamic stresses, 6 AAA models were reconstructed and characterized. The models were characterized using thirteen geometrical factors based on the lumen center line: eight 1D indices, three 3D indices, and two 0D indices. The temporal and spatial distributions of hemodynamic stresses were computed using computational fluid dynamics. The results showed that the hemodynamic stresses are modified by the time variations of the AAA morphology, and therefore, the hemodynamic stresses, in combination with other parameters, could be a criterion for improved rupture risk prediction. Statistical correlations between hemodynamic stresses and geometric indices have confirmed the influence by the AAA morphometry on the prediction of the rupture risks, although higher reliability of these correlations is required.

This paper focuses on the design of long-span suspension bridges under aeroelastic constraints. Such challenging structures need to be protected against wind-induced instabilities as flutter. The authors envision that a set of scientific disciplines not currently used in bridge engineering may help along the design process and constitute a useful tool. First, the formulation of sensitivity analysis of flutter speed is described, indicating how this technique can be a guide for engineers making changes in the prototype; two examples of important bridges, as the Great Belt and Messina Strait, are used to demonstrate the capability of this approach. Then, the idea of producing computer animations to represent the aeroelastic deformation of bridges simulating virtual boundary layer wind tunnel testing is presented showing pictures of the Tacoma Narrows and Messina Bridges. Finally, the advantages of introducing distributed computing to make easier to implement the previously mentioned techniques are demonstrated. The authors have previously published papers related with sensitivity analysis in bridges or computer animations of the aeroelastic behaviour of suspension bridges. However, this is the first time that their comprehensive multidisciplinary approach is presented.

We compared the hemodynamic performance of the Edwards Perimount Magna (EPM) and the Medtronic Mosaic (MM) bioprostheses according to the patient aortic annulus diameter (AAD). Eighty-six patients undergoing aortic valve replacement were prospectively assigned to receive either an EPM-valve (n=43) or an MM-bioprosthesis (n=43). Randomization was performed after measuring the AAD and patients were grouped according to their AAD:22 mm (n=12), 22-23 mm (n=31) and23 mm (n=43). Echocardiographic assessment was performed one year postoperatively. The mean AAD (EPM 23.9+/-2.1 mm vs. MM 23.6+/-2.3 mm) and mean valve size implanted (EPM 22.6+/-2.1 mm vs. MM 23.3+/-2.1 mm) were comparable in both groups. The EPM-group showed significantly lower mean gradient (EPM 10.2+/-3.2 mmHg vs. MM 17.1+/-8.2 mmHg) and larger effective orifice area (EOA) (EPM 1.99+/-0.4 cm(2) vs. MM 1.69+/-0.4 cm(2), P0.0001). The EPM-valve was superior with respect to mean pressure gradient and EOA in all AAD. This difference was statistically significant in AAD of 22-23 mm (EPM 9.6+/-3.0 mmHg vs. MM 18.2+/-8.6 mmHg; EPM 1.82+/-0.3 cm (2) vs. MM 1.51+/-0.2 cm (2)) and23 mm (EPM 9.9+/-3.1 mmHg vs. MM 14.2+/-5.6 mmHg; EPM 2.18+/-0.4 cm(2) vs. MM 1.94+/-0.5 cm(2)). Patient-prosthesis mismatch was present in 26.8% (MM) vs. 6.9% (EPM) of the patients (P=0.01). When the same AAD is taken as a reference, the EPM-valve was hemodynamically superior to the MM-bioprosthesis. The EPM-prosthesis significantly reduced the incidence of PPM.

In this work the practical applicability of a 2D URANS approach adopting a block structured mesh and Menter's SST k-ω turbulence model in fluid-structure interaction (FSI) problems is studied using as a test case a ratio B/H = 4 rectangular cylinder. The vortex-induced vibration (VIV) and torsional flutter phenomena are analyzed based on the computation of the out-of-phase and in-phase components of the forced frequency component of lift and moment coefficients when the section is forced to periodically oscillate both in heave and pitch degrees of freedom. Also the flutter derivatives are evaluated numerically from the same forced oscillation simulations. A good general agreement has been found with both experimental and numerical data reported in the literature. This highlights the benefits of this relatively simple and straightforward approach. These methods, once their feasibility has been checked, are ready to use in parametric design of bridge deck sections and, at a later stage, in the shape optimization of deck girders considering aeroelastic constraints.

Introduccion y objetivos La troponina I (TnI) es un marcador de dano miocardico utilizado en la estratificacion pronostica del sindrome coronario agudo. El objetivo del estudio fue analizar el valor pronostico tardio del nivel maximo de TnI obtenido en las 48 h tras el ingreso en una unidad coronaria por angina inestable. Metodos Se incluyo a 149 pacientes consecutivos. Se realizaron determinaciones seriadas de la fraccion MB de la creatincinasa (CK-MB) y TnI. Los pacientes sin elevacion de la CK-MB fueron clasificados en dos grupos, en funcion de la presencia de TnI elevada (n = 58) o normal (n = 91). Se analizaron prospectivamente los factores clinicos y evolutivos relacionados con la probabilidad de muerte, nuevo episodio agudo coronario o revascularizacion coronaria tras un ano de seguimiento. Resultados No se observaron diferencias entre los dos grupos en relacion con las caracteristicas clinicas, salvo la edad, que fue mayor en el grupo con TnI elevada (69 frente a 64 anos; p = 0,01). Tras un ano de seguimiento no se apreciaron diferencias en la incidencia de nuevos acontecimientos coronarios agudos ni en la revascularizacion; sin embargo, la mortalidad fue mayor en el grupo con TnI elevada (el 13 frente al 4%; p = 0,01). Los predictores independientes de mortalidad fueron el infarto previo (riesgo relativo [RR] = 3), TnI elevada (RR = 3,2), fraccion de eyeccion 70 anos (RR = 15). Conclusiones En la angina inestable, un valor elevado de TnI dentro de las primeras 48 h del ingreso se asocia con un aumento de la mortalidad al ano de seguimiento.

Increasing the efficiency in the process to numerically compute the flutter derivatives of bridge deck sections is desirable to advance the application of CFD based aerodynamic design in industrial projects. In this article, a 2D unsteady Reynolds-averaged Navier-Stokes (URANS) approach adopting Menter׳s SST k-ω turbulence model is employed for computing the flutter derivatives and the static aerodynamic characteristics of two well known examples: a rectangular cylinder showing a completely reattached flow and the generic G1 section representative of streamlined deck sections. The analytical relationships between flutter derivatives reported in the literature are applied with the purpose of halving the number of required numerical simulations for computing the flutter derivatives. The solver of choice has been the open source code OpenFOAM. It has been found that the proposed methodology offers results which agree well with the experimental data and the accuracy of the estimated flutter derivatives is similar to the results reported in the literature where the complete set of numerical simulations has been performed for both heave and pitch degrees of freedom. Xunta de Galicia; GRC2013-056 Ministerio de Economía y Competititividad; DPI2013-41893-R

The results of several bridge decks 2D steady and unsteady RANS (Reynolds Averaged Navier-Stokes) simulations are reported in this work. The focus has been put on the potential of CFD based simulations in industrial applications in the realm of bridge engineering aerodynamic and aeroelastic problems. The force coefficients of a box deck have been computed at different angles of attack finding a good match with the experimental data available in the literature. Also CFD steady simulations have been used to obtain the force coefficients of a Π section considered in the original design proposal of a cable-stayed bridge. Based on the numerical computations, modifications in the original design have been proposed adding fairings and baffles which showed an improved aerodynamic response. The scale effects in the performance of guide vanes for mitigating the vortex-induced response of a twin box girder have been analyzed by means of CFD obtaining a good agreement with experimental measurements. Finally the effect of wind barriers in a twin box deck have been assessed based on the spectrum of the lift coefficient for both the cross-section fitted with or without wind barriers.

In this work the authors have studied the applicability of the 2D URANS approach adopting a block structured mesh and Menter’s SST k-omega turbulence model for the aspect ratio 4 rectangular cylinder. As a first step, a verification study is carried out for the mesh refinement level and the time step size. Then, the static response for a 0o angle of attack is considered for validation purposes. The vortex induced vibration response is computed based on the outof-phase component and phase angle of a one degree of freedom heave forced oscillation simulation at different reduced velocities. Finally, the flutter derivatives are evaluated based on the results of forced induced oscillations in both heave and pitch degrees of freedom. The computational results obtained herein have been in agreement with both experimental and numerical data available in the literature. The proposed methodology based on 2D URANS is less computer power demanding than a 3D LES approach, while it keeps a good accuracy level, which is of particular interest in the frame of industrial applications.

La hemocromatosis esta caracterizada por un excesivo deposito de hierro en una variedad de tejidos. La afeccion cardiaca sucede en un tercio de los pacientes con hemocromatosis y se produce como consecuencia de una acumulacion de ferritina en el musculo cardiaco que induce por un lado una alteracion en la funcion ventricular sistolica y diastolica y por otro un sustrato arritmogenico. Las manifestaciones clinicas pueden estar indistintamente relacionadas con taquiarritmias auriculares, ventriculares, bloqueos auriculoventriculares y/o con insuficiencia cardiaca congestiva, siendo mas frecuentes las primeras. Presentamos el caso de una paciente con hemocromatosis secundaria a transfusiones repetidas por anemia sideroblastica con afeccion cardiaca y cuyas primeras manifestaciones cardiacas fueron taquiarritmias auriculares recurrentes y taquicardia ventricular sostenida sincopal, por lo que se implanto un desfibrilador automatico.

We report the case of a 53-year-old patient with a mitral prosthesis hospitalized for heart failure. Diagnosis of mitral prosthetic thrombosis, led to a therapeutic disjunction between thrombolysis and surgery. Because of the high risk of surgical intervention, the patient was treated with r-TPA (accelerated infusion), showing immediate, successful response.

Introduccion y objetivos Un volumen plaquetario elevado en la fase cronica del infarto de miocardio se asocia con un mayor riesgo de episodios isquemicos recurrentes y muerte, pero el significado de este signo sobre el pronostico a corto plazo del infarto de miocardio es desconocido. Los objetivos del presente estudio fueron investigar la influencia del volumen plaquetario medio sobre el riesgo de muerte, isquemia recurrente e insuficiencia cardiaca durante la fase hospitalaria y analizar las relaciones del volumen plaquetario con variables demograficas y clinicas, obtenidas al ingreso hospitalario. Material y metodos Se estudian 1.082 pacientes con infarto de miocardio, clasificados en dos grupos de acuerdo con el volumen plaquetario medio estimado al ingreso: grupo 1, volumen plaquetario superior a 9 fl (n = 443) y grupo 2, volumen plaquetario ≤ 9 fl (n = 639). El analisis de las diferencias entre ambos grupos sobre los puntos finales del estudio fue realizado mediante tecnicas univariante y de regresion logistica. Un analisis estadistico univariante fue aplicado para investigar la relacion del volumen plaquetario con las variables basales al ingreso. Resultados Un volumen plaquetario superior a 9 fl se asocio con un aumento significativo del riesgo del punto final combinado del estudio (OR = 1,37; p = 0,026). En el estudio univariante, un volumen plaquetario elevado se relaciono con una incidencia mayor de insuficiencia cardiaca (OR = 1,46; p = 0,01) junto a un aumento no significativo del riesgo de angina/reinfarto (OR = 1,35; p = 0,07). Ademas, un volumen plaquetario superior a 9 fl se asocio con una mayor prevalencia de infarto previo, hipertension arterial y diabetes mellitus. Conclusiones Los resultados del estudio sugieren que un volumen plaquetario alto al ingreso es un predictor independiente de riesgo de insuficiencia cardiaca durante la fase hospitalaria y en nuestro estudio se asocio con una tendencia no significativa hacia una mayor tasa de episodios isquemicos recurrentes a corto plazo.

Introduccion El analisis de la variabilidad de la frecuencia cardiaca ha sido aceptado como metodo no invasivo para valorar la influencia del sistema nervioso autonomo sobre el corazon. Aunque la variabilidad de la frecuencia cardiaca se ha venido utilizando en la ultima decada en diversas patologias, los estudios en la miocardiopatia hipertrofica son escasos. Objetivos Investigar mediante el analisis de la variabilidad de la frecuencia cardiaca la actividad del sistema nervioso autonomo en pacientes con miocardiopatia hipertrofica. Pacientes y metodos La variabilidad de la frecuencia cardiaca se ha evaluado mediante el analisis del registro electrocardiografico de 24 h (Holter) en 20 pacientes con miocardiopatia hipertrofica y en 15 controles normales. Se utilizo como medida de la variabilidad de la frecuencia cardiaca el analisis espectral de las frecuencias que fueron calculadas mediante el analisis de la transformada de Fourier. Se analizan los componentes de alta frecuencia (0,15 a 0,40 Hz), los de baja frecuencia (0,04 y 0,15 Hz) y el componente global (0,01 y 1,0 Hz). Tambien se valora la relacion entre el componente de baja/alta frecuencia como indice del balance simpaticovagal del corazon. Los datos se presentan con valores medios ± DE. Se utiliza el test de la t de Student para datos no apareados. Se consideran significativos valores de p Resultados No hubo diferencias en la frecuencia cardiaca media entre los pacientes con miocardiopatia hipertrofica y los controles (media ± DE: 71 ± 9 frente a 74 ± 11 lat/min; p = NS), mientras que hubo un descenso significativo tanto en el componente global (media ± DE: 7,14 ± 1,1 frente a 7,57 ± 0,6 ln [ms 2 ]; p = 0,02), como en los componentes de altas (media ± DE: 5,22 ± 0,8 frente a 5,63 ± 1,3 ln [ms 2 ]; p = 0,04) y bajas frecuencias (media ± DE: 6,14 ± 1,2 frente a 6,72 ± 0,7 ln [ms 2 ]; p = 0,03). No hubo diferencias significativas entre el cociente de bajas/altas frecuencias (media ± DE: 1,1 ± 0,1 frente a 1,2 ± 0,1 ln [ms 2 ]; p = NS). Conclusiones Estos datos sugieren que los pacientes con miocardiopatia hipertrofica tienen una alteracion en el estado del sistema nervioso autonomo tanto en la actividad simpatica (componente de baja frecuencia) como en la actividad vagal (componente de alta frecuencia), si bien no se traduce en un desequilibrio entre actividad simpaticaparasimpatica (relacion bajas/altas frecuencias).

The cable stayed bridge of Talavera de la Reina in central Spain is a signature structure of a high aesthetic quality, the main span is 318 m long and the single pylon reaches 164 m of height. Due to the relevance of the bridge a study of the wind characteristics at the location and a set of aerodynamic studies both experimental and computational were carried out to anticipate the future response of the bridge under wind flow. They comprised a boundary layer wind tunnel test of the stand alone pylon and the full bridge, a test of a reduced model of a segment of the deck in an aerodynamics wind tunnel and computational analysis to obtain the flutter speed of the bridge. This paper describes the bridge and the results of the mentioned studies that allowed us to conclude that the bridge could perform safely while subjected to the expected wind speed at its location.

Abdominal aortic aneurysms (AAAs) rupture is one of the main causes of death in the world. This is a very complex phenomenon that usually occurs “without previous warning”. Currently, criteria to assess the aneurysm rupture risk (peak diameter and growth rate) cannot be considered as reliable indicators. In order to improve the predicting of AAA rupture risk, it had been developed a simple method, where the main geometric parameters of aneurysms have been linked into six biomechanical factors, which have been combined to obtain a dimensionless rupture risk index, RI(t). Based on the initial results of the validation tests of this method a broader prospective randomized control study with two hundred and one patients at the Clinic Hospital of Valladolid-Spain using a new set of weighted coefficient values for each biomechanical factor has been carried out in this work. The outcomes of the present work have shown that it is possible to implement a clinical assessment of the AAA rupture risk through its geometric parameters. Defined quantitative indicator is easy to understand. It allows estimating the aneurysms rupture risks and is able to identify the ones that ruptures even when its peak diameter is less than the threshold value. It also identifies those cases where the rupture should not occur regardless the maximum diameter is greater than the rupture threshold value and consequently avoids the patients to be submitted to surgical procedure. According to the results, the most relevant geometric biomechanical factors are the deformation rate and the growth rate. Beside these ones, but less important, resulted the saccular index.

© 2012 Vilalta et al., licensee InTech. This is an open access chapter distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Biomechanical Approach to Improve the Abdominal Aortic Aneurysm (AAA) Rupture Risk Prediction

There are multiple configurations permitted for a cable stayed bridge such as the number of spans, tower shapes, and cable arrangements. Therefore it is always important to study the behaviour of these types of structures against strong winds so that aeroelastic instabilities do not appear. This paper contains detailed aeroelastic analyses of three cable stayed bridges of very different configurations. Talavera Bridge over the Tagus River in Spain has only a single span of 315 m with a single pylon. The bridge has a central stay cable plane that supports the deck and two skewed planes of rear cables that allow the overall balance. The project of Miradoiros Bridge over La Coruna estuary in Spain has a classical configuration with a main span of 658 m and two secondary spans of 270 m each. The bridge has two lateral stay cable planes and an aerodynamic box girder. Finally, the future cable stayed bridge over the Forth in Scotland is studied. It has three mono-towers with a symmetrical arrangement resulting in two 650 m main spans and 325 m side spans. The deck superstructure is a single cell box girder with the stay cables anchored along the centre, so the bridge has two corridors. The software that analysed the aeroelastic instabilities of these bridges has been developed by the School of Civil Engineering at the University of La Coruna and it is based on hybrid methods. The hybrid methods are computational, although they need some coefficients and functions which must be obtained experimentally in an aerodynamic wind tunnel working with a deck sectional model. These experimental data permit the analysis of the complete structure considering the fluid-structure interaction between the wind flow and the deck.

The recently designed highway for by-passing the city of Talavera de la Reina in Spain is currently under construction. The main structural element in the project is a cable-stayed bridge which for sure will become a landmark in the region. The bridge has a main span of 318 m, comprising a concrete box deck 36 m width and a single inclined pylon 164 m high. The singularity of the bridge has recommended a comprehensive analysis regarding wind effects on the structure. The aerodynamic coefficients of the deck have been obtained from wind tunnel tests and they have also been computed using CFD software considering two different turbulence models. Also the flutter functions have been evaluated by means of sectional model tests and the flutter velocity has been obtained. It has been found that the bridge enjoys a safe design for wind actions.

In September 2007 the Spanish version of eurocode, UNE-EN 1991-1-4 has been published; also in road bridges the Spanish IAP code is considered by designers as a feasible tool for the evaluation of wind actions on conventional road bridges. Additionally the AASHTO LRFD Bridge Design Specifications is a feasible comprehensive code. The aim of this work is to analyze the approaches followed for the aforementioned codes for the design of short road bridges in terms of wind loads values and “user-friendliness”. Thus the general procedures are described in order to get a grasp of their stipulations. Finally, two examples of simple bridges have been considered to evaluate the wind loads to be considered in their design according to the two codes. It has been obtained that eurocode and AASHTO LRFD give higher wind loads than the IAP code. Moreover IAP and AASHTO LRFD are easier to use for practitioners as they are specific bridge norms.