Antonio Isalgue
Universitat Politecnica de Catalunya, Física Aplicada, Faculty Member
- Professor, PhD in Physics in 1984edit
In recent years, we have studied the serious and very serious maritime accidents registered by the Spanish fishing sector in all its modalities and areas. In several cases, the results obtained are different from the hypotheses initially... more
In recent years, we have studied the serious and very serious maritime accidents registered by the Spanish fishing sector in all its modalities and areas. In several cases, the results obtained are different from the hypotheses initially raised. At a global level, the problem of fishing accidents is observed practically all over the world, regardless of the level of development and there are various theories about them, but it does not cease to surprise that maritime transport is one of the forms of transport with the lower ratio of accidents referred to the transport carried out, while in the fishing sector the accident rate is much higher than in other industrial or productive sectors. Regarding the influence of the meteorological conditions, we observe that the maritime accidents of fishing boats in Spain occur mostly on theoretically good days, meteorologically speaking, in which the wind was very low, and the visibility was excellent, but the swell was considerable. On the othe...
Research Interests: Fishing and Visibility
Las interrelaciones y la complejidad inherente en los espacios urbanos modernos hacen difícil el análisis y la extracción de conclusiones y acciones a realizar para la mejora de condiciones de vida y la minimización del impacto ambiental.... more
Las interrelaciones y la complejidad inherente en los espacios urbanos modernos hacen difícil el análisis y la extracción de conclusiones y acciones a realizar para la mejora de condiciones de vida y la minimización del impacto ambiental. Decisiones planeadas cuidadosamente y líneas de acción establecidas tras larga reflexión pueden producir resultados totalmente inesperados a causa de particularidades, o de complejos conjuntos de reacciones por parte de los residentes o de poderes económicos no incluidos inicialmente, confiriendo gran complejidad al sistema urbano. La complejidad tiende a incrementar con el tamaño, y esto es concomitante con la concentración de servicios en ciudades, y en grandes aglomeraciones. Las necesidades de transporte se vuelven más evidentes con el aumento de tamaño de las concentraciones urbanas. Otros sistemas muy complejos, como los seres vivos, satisfacen relaciones aproximadas entre algunas de las variables macroscópicas que los definen, conocidas como...
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In cold regions, the reduction in envelope thermal transmittance is often the dominant parameter in ensuring thermal comfort in buildings. However, countries in warmer climates have also adopted this same strategy, often neglecting other... more
In cold regions, the reduction in envelope thermal transmittance is often the dominant parameter in ensuring thermal comfort in buildings. However, countries in warmer climates have also adopted this same strategy, often neglecting other parameters that are more influential in their respective climate regions that can achieve thermal comfort. This study focuses on passive building strategies to ensure a building’s thermal comfort conditions in Mediterranean climates in the winter. This monitoring study compares two dwellings during the winter in Barcelona, Spain, in order to analyze the impact of not only the envelope’s thermal properties on indoor temperature, but also the role of other factors such as outdoor temperature and solar gains. The dwellings were built in different decades, each following distinct building technical codes, diverse construction techniques, and building materials. The methodology used in this study is based on thermal measurements, meteorological data, and...
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ABSTRACT Experimental study of damping in civil engineering structures was done using smart materials (NiTi SMA). The study is focused on the stayed cables for bridges. The cable oscillations are induced by wind, rain or traffic. The SMA... more
ABSTRACT Experimental study of damping in civil engineering structures was done using smart materials (NiTi SMA). The study is focused on the stayed cables for bridges. The cable oscillations are induced by wind, rain or traffic. The SMA and their solid-solid phase transformation permits effective damping via the hysteresis cycle and the conversion of mechanical work in heat. The analysis of SMA behavior needs to be strictly coherent with the requirements associated to the application. In particular, the high requirement on working cycles induced by a strong storm of 3 or 4 days, the temperature stress dependence of the phase transformation (via Clausius-Clapeyron equation), the self-heating effects, the SMA creep and the eventual effects of aging (temperature and time) on the transformation temperatures (i.e., atomic order and/or other effects) were studied. The SMA was applied to mitigate the oscillations induced in realistic cables in ELSA (45 m length) with positive results, and in the LCPC facility (50 m length), always with equivalent simulation tests. The experimental examples suggest that the SMA permit an effective reduction of the oscillation amplitudes better than a half. The work is realized in the frame of SMARTeR, one S3T-ESF project their goal is the damping in stayed cables of bridges. For instance, the Iroise bridge in the highway between Brest and Plougastel, France, or eventually in the St. Nazaire bridge in the Loire Atlantique near Nantes or other bridges (i.e. the Viaducs du Boulonnais in the A16 highway, France).
The particular properties of Shape Memory Alloys associated to their thermoelastic martensitic transformation with hysteresis permits applications of SMA as a damper via the conversion of the work absorbed in each cycle in heat. The... more
The particular properties of Shape Memory Alloys associated to their thermoelastic martensitic transformation with hysteresis permits applications of SMA as a damper via the conversion of the work absorbed in each cycle in heat. The guaranteed behavior requires the appropriateness of SMA for the complete requirements of the application. This work shows two complementary aspects of the SMA application in Civil Engineering, the first of them, the SMA dampers in earthquake damping of a family house. The second aspect relates an elementary approach to the damping of stayed cables in bridges, using some data from the Iroise Bridge. The application in the first case needs long time constancy of properties and then around 200 cycles during an earthquake. In the second case, the fatigue life of SMA imposes that only small strains in the alloy can be accepted. Finally, it is emphasized the importance of working conditions, including temperature and time.
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Shape Memory Alloys (SMA) show particular properties associated to their martensitic transformation between metastable phases. Their use in dampers requires a deep knowledge of the SMA behavior and its coherence with the application... more
Shape Memory Alloys (SMA) show particular properties associated to their martensitic transformation between metastable phases. Their use in dampers requires a deep knowledge of the SMA behavior and its coherence with the application requirements. In earthquakes engineering standard conditions require that, after several years or decades at rest, an excellent performance is necessary for one or two minutes, i.e., nearly 200 working oscillations. When the target is the damping of stayed cables in bridges under the wind or rain actions, a larger number of oscillations is expected per each working day. This contribution analyzes the fatigue behavior of a CuAlBe alloy (appropriate for earthquakes) and discusses the results of some available experiments on a NiTi alloy for their eventual application to stayed cables..
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ABSTRACT Several solutions have been proposed to mitigate the vibrations of stay cables in bridges, which are subjected to wind, rain and traffic loads. One possible solution relates to the use of semi-active devices, such as the ones... more
ABSTRACT Several solutions have been proposed to mitigate the vibrations of stay cables in bridges, which are subjected to wind, rain and traffic loads. One possible solution relates to the use of semi-active devices, such as the ones based on magneto-rheologic fluids. These devices need guaranteed electrical power, together with computational effort and technical attention. In contrast, shape memory alloy (SMA) wires were studied for application as passive elements. In the present work, the properties of SMA that are required to realize dampers provided with an appropriate reliability are discussed. In particular, the fatigue/fracture life of the SMA wires and the thermal effects induced by both external temperature and the self-heating process are studied. The SMA dampers were applied to stayed cables of realistic size and tested in "facilities." Namely, the cables No 1 of 45 m length available at the ELSA-JRC in Ispra, Italy, and the 50 m cable of IFSTTAR near Nantes, in France, were considered. The experimental results establish a reduction of the vibration amplitude to one half or less than the one observed in the un-damped case. Furthermore, the installation of the SMA dampers causes an increase of the cable frequency. Performing a Windowed Fourier Transform or a Wavelet Transform analysis the evolution of frequency with the signal amplitude was studied. The change of amplitude produces a change of stiffness in the SMA. The adoption of an appropriate phenomenological model of the hysteresis cycle permits to perform numerical simulations using standard Finite Elements Analysis tools such as, for instance, the ANSYS software.
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The application of Shape Memory Alloy (SMA) devices to practical uses need well established performance. The reliable application in some areas, as dampers in engineering, needs a known, relatively long fatigue life (some million... more
The application of Shape Memory Alloy (SMA) devices to practical uses need well established performance. The reliable application in some areas, as dampers in engineering, needs a known, relatively long fatigue life (some million oscillations). The thermomechanical properties of SMA, based on their martensitic transformation, made them attractive to use for damping, taking advantage of the pseudoelastic window and hysteresis on transforming-retransforming. Due to size effects and to the fact that fatigue failure in metallic NiTi usually comes from a defect inducing crack growth, fatigue has to be studied for concrete applications, with the correct samples. The present work points out the possibility to apply NiTi to dampers and actuators. Testing machine experiments indicate that the main parameter controlling fatigue life is the effective stress on the NiTi wire. Long wire life (in the million cycle regime) can be achieved under limited stresses (around or under 200 MPa). Also, exp...
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The properties of SMA (Shape Memory Alloys, smart materials) are associated to a first order phase transition named martensitic transformation that occurs between metastable phases: austenite and martensite. At higher temperature phase or... more
The properties of SMA (Shape Memory Alloys, smart materials) are associated to a first order phase transition named martensitic transformation that occurs between metastable phases: austenite and martensite. At higher temperature phase or at lower stress the austenite is the metastable phase. The martensite appears at lower temperature phase or higher stresses. The hysteresis of the transformation permits different levels of applications, i.e., in their use as a damper. Two types of applications can be considered in damping of structures in Civil Engineering. The first one is related to diminishing the damage induced by earthquakes. The second one is a reduction of oscillation amplitude associate to an increase of the lifetime for the stayed cables in bridges. Different fundamental behavior of the SMA needs to be guaranteed in each case.
ABSRACT: A deeper understanding of the effectiveness of adopting devices mounting shape memory alloy (SMA) elements in applications targeted to the mitigation of vibrations is pursued via an experimental approach. During a seismic event,... more
ABSRACT: A deeper understanding of the effectiveness of adopting devices mounting shape memory alloy (SMA) elements in applications targeted to the mitigation of vibrations is pursued via an experimental approach. During a seismic event, less than 1000 loading unloading cycles of the alloy are required to mitigate the earthquake effects. However, the aging effects during the time of inactivity prior to the oscillations (several decades characterized by the yearly summer-winter temperature wave) should be considered in order to avoid and/or minimize them. In this paper, the results obtained by carrying out, in different laboratories, fatigue tests on SMA specimens are compared and discussed. Furthermore, the effects of seismic events on a steel structure, with and without SMA dampers, are numerically simulated using ANSYS. Under an earthquake excitation, the SMA devices halve the oscillation amplitudes and show re-centering properties. To confirm this result, an experimental campaign is conducted by actually installing the proposed devices on a physical model of the structure and by evaluating their performance under different excitations induced by an actuator.
KEYWORDS: damping; fatigue life; passive control systems; shape memory alloys; vibration mitigation
KEYWORDS: damping; fatigue life; passive control systems; shape memory alloys; vibration mitigation
Research Interests: Materials Engineering, Civil Engineering, Materials Science, Dynamical Systems, Earthquake Engineering, and 21 moreVibrations, Structural Dynamics, Finite Element Analysis (Engineering), Advanced materials in architecture, Experimental Mechanics, Materials, Materials Characterisation, Vibration Control, Applied Mechanics, Mechanical Behavior Of Materials, Steel Structure, Smart Materials, Fatigue, Vibration, Materials Science and Engineering, Mechanics of Materials, Shape Memory Alloys, Dissipative Systems, Dampers, Laboratory experiment, and Hysteretic energy dissipation capacity
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Building sensitivity to climatic fluctuations and users' actions: a challenge for high- tech buildings Due to the current concern about energy consumption and CO2 emissions, buildings are increasingly insulated and equipped with... more
Building sensitivity to climatic fluctuations and users' actions: a challenge for high- tech buildings Due to the current concern about energy consumption and CO2 emissions, buildings are increasingly insulated and equipped with controlling machinery. However, the effective energy consumption of high-tech buildings is often higher than expected, and users' sensation of temperature comfort is not as good as it should
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Artisanal fishing has been and remains one of the sectors with the highest accident rate in our country. According to serious studies in artisanal fisheries in the area of Galicia accidents are the small boats those that have the... more
Artisanal fishing has been and remains one of the sectors with the highest accident rate in our country. According to serious studies in artisanal fisheries in the area of Galicia accidents are the small boats those that have the strongest claims. It is also observed that accidents occurred during operations of gear retrieval. Faced with this problem is to conduct a study that will further knowledge of the conditions in which the accident occurred, then to carry out the necessary measures to reduce the number of fatalities in this sector proposals.
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Hemos introducido en la evaluacion de las asignaturas “Fonaments Fisics” (DMN i DNM) “Fonaments Fisics de l’ Enginyeria” (ETPSV) la realizacion de un ejercicio de autoevaluacion utilizando los cuestionarios proporcionados por Moodle.... more
Hemos introducido en la evaluacion de las asignaturas “Fonaments Fisics” (DMN i DNM) “Fonaments Fisics de l’ Enginyeria” (ETPSV) la realizacion de un ejercicio de autoevaluacion utilizando los cuestionarios proporcionados por Moodle. Llevamos a cabo una experiencia conjunta con los alumnos de las titulaciones ETPSV y DMN, obteniendose que la nota media (sobre 10) en el cuestionario fue de 6.00, y de 5.90 en el examen final con una dispersion de 0.63. Puede observarse la validez del cuestionario como correlacion entre el resultado obtenido en el cuestionario Moodle y el que, posteriormente obtienen en el examen final.
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La percepció i l’habitabilitat de l’espai urbà són aspectes molt relacionats amb la radiació solar. Malgrat això, l’anàlisi de la llum natural no s’acostuma a utilitzar per avaluar el confort ambiental en els espais urbans, tot i... more
La percepció i l’habitabilitat de l’espai urbà són aspectes molt relacionats amb la radiació solar. Malgrat això, l’anàlisi de la llum natural no s’acostuma a utilitzar per avaluar el confort ambiental en els espais urbans, tot i que l’anàlisi lumínica de l’espai públic proporciona una lectura excel·lent de l’escena arquitectònica en termes formals i funcionals. En aquesta recerca es busquen connexions entre la composició dels espais públics i la llum natural que permetin comprendre quins paràmetres influeixen en el confort visual i tèrmic dels seus usuaris. Concretament, s’avalua la distribució i la tendència de les dades físiques referides a la llum natural en places situades en ciutats mediterrànies. L’estudi s’enfoca en dues places rectangulars (una a Sicília i una a Catalunya) amb característiques espacials similars, en les que es realitza un estudi comparatiu. Quatre escenes de cada plaça van ser fotografiades en tres intervals de temps diferents i després, les imatges es van ...
Research Interests: Humanities and Art
The presence of precipitates in SMA influences strongly their properties. We present some experimental results for small γ phase precipitates (around 10 nm) in Cu-Zn-Al single crystals. The shift in transformation temperatures and the... more
The presence of precipitates in SMA influences strongly their properties. We present some experimental results for small γ phase precipitates (around 10 nm) in Cu-Zn-Al single crystals. The shift in transformation temperatures and the evolutive behaviour of the stress/temperature width on cycling are interpreted as due to the creation of dislocations and to the subsequent plastic deformation of martensite around the precipitates as a consequence of the β-martensite interface passing through the material. With the appropriated thermomechanical treatment, the precipitate growth could be oriented to give a symmetry breakdown of the system and, as a result, a two way shape memory effect could be obtained.
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The damping property of shape memory alloys (SMA) can be used in passive damping devices in which there is no moving part. Some of these dampers were designed to work in the martensitic regime of SMA while others operate in the... more
The damping property of shape memory alloys (SMA) can be used in passive damping devices in which there is no moving part. Some of these dampers were designed to work in the martensitic regime of SMA while others operate in the superelastic regime. The superelastic regime dissipates less energy per cycle than the martensitic one, but it offers a better structural stability as well as a re-centering capability. Also, the performances of a superelastic SMA damper are improved if a pre-strain is applied. However, some temporal effects related to the application of a pre-strain compromise the long-term stability of the damper. This article discusses the design of an SMA superelastic damper intended for small residential buildings. For economical reasons, such buildings cannot be equipped with a classical active or semi-active control damping technology. The innovative aspect of the SMA damper presented here is its capacity to operate in a pre-strain state only when the earthquake occurs...
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Shape memory alloys are considered smart materials because of their singular thermo-mechanical properties, due to a thermoelastic martensitic transformation, enabling possible uses as actuators (because of mechanical recovery induced from... more
Shape memory alloys are considered smart materials because of their singular thermo-mechanical properties, due to a thermoelastic martensitic transformation, enabling possible uses as actuators (because of mechanical recovery induced from temperature changes) and as dampers (because of hysteresis). NiTi wires for dampers in Civil Engineering had been characterized and tested in facilities. Guaranteed performance needs to know behavior during fatigue life and knowledge of effects in the event of extreme conditions, as
eventual overstraining. In this work, we check the possibilities to absorb mechanical energy on the fatigue life depending on stress level and explore the consequences of overstraining the material during installation, the possibilities of partial healing by moderate heating, and some effects of over-stressing the wires. The mechanical energy absorbed by the unit weight of damper wire might be very high during its lifetime if
maximum stresses remain relatively low allowing high fatigue life. We show also some results on NiTi wire working as an actuator. The lifetime mechanical work performed by an actuator wire can be very high if applied stresses are limited. The overstraining produces relevant ‘‘residual’’ deformation, which can be to some extent reversed by moderate heating at zero stress. The reason for the observed characteristics seems
to be that when external high stresses are applied to an NiTi wire, it undergoes some plastic deformation, leaving a distribution of internal stresses that alter the shape and position of the macroscopic stress-strain transformation path.
eventual overstraining. In this work, we check the possibilities to absorb mechanical energy on the fatigue life depending on stress level and explore the consequences of overstraining the material during installation, the possibilities of partial healing by moderate heating, and some effects of over-stressing the wires. The mechanical energy absorbed by the unit weight of damper wire might be very high during its lifetime if
maximum stresses remain relatively low allowing high fatigue life. We show also some results on NiTi wire working as an actuator. The lifetime mechanical work performed by an actuator wire can be very high if applied stresses are limited. The overstraining produces relevant ‘‘residual’’ deformation, which can be to some extent reversed by moderate heating at zero stress. The reason for the observed characteristics seems
to be that when external high stresses are applied to an NiTi wire, it undergoes some plastic deformation, leaving a distribution of internal stresses that alter the shape and position of the macroscopic stress-strain transformation path.
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Research Interests: Physics and Humanities
ABSTRACT A deeper understanding of the effectiveness of adopting devices mounting shape memory alloy (SMA) elements in applications targeted to the mitigation of vibrations is pursued via an experimental approach. During a seismic event,... more
ABSTRACT A deeper understanding of the effectiveness of adopting devices mounting shape memory alloy (SMA) elements in applications targeted to the mitigation of vibrations is pursued via an experimental approach. During a seismic event, less than 1000 loading-unloading cycles of the alloy are required to mitigate the earthquake effects. However, the aging effects during the time of inactivity prior to the oscillations (several decades characterized by the yearly summer-winter temperature wave) should be considered in order to avoid and/or minimize them. In this paper, the results obtained by carrying out, in different laboratories, fatigue tests on SMA specimens are compared and discussed. Furthermore, the effects of seismic events on a steel structure, with and without SMA dampers, are numerically simulated using ANSYS. Under an earthquake excitation, the SMA devices halve the oscillation amplitudes and show re-centering properties. To confirm this result, an experimental campaign is conducted by actually installing the proposed devices on a physical model of the structure and by evaluating their performance under different excitations induced by an actuator.
Research Interests: Engineering, Materials Engineering, Civil Engineering, Materials Science, Dynamical Systems, and 15 moreEarthquake Engineering, Advanced materials in architecture, Experimental Mechanics, Materials, Materials Characterisation, Applied Mechanics, Mechanical Behavior Of Materials, Fatigue, Materials Science and Engineering, Mechanics of Materials, Shape Memory Alloys, Dissipative Systems, Dampers, Laboratory experiment, and Hysteretic energy dissipation capacity
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