In recent years, we have studied the serious and very serious maritime accidents registered by th... 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...
5th International Conference Virtual City and Territory, Barcelona, 2,3 and 4 June 2009
Las interrelaciones y la complejidad inherente en los espacios urbanos modernos hacen difícil el ... 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...
In cold regions, the reduction in envelope thermal transmittance is often the dominant parameter ... 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...
ABSTRACT Experimental study of damping in civil engineering structures was done using smart mater... 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 tr... 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.
Shape Memory Alloys (SMA) show particular properties associated to their martensitic transformati... 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..
ABSTRACT Several solutions have been proposed to mitigate the vibrations of stay cables in bridge... 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.
The application of Shape Memory Alloy (SMA) devices to practical uses need well established perfo... 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...
The properties of SMA (Shape Memory Alloys, smart materials) are associated to a first order phas... 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.
Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC -... more Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC - stainless steel or NiTi matrix coatings. The starting feedstock powders have been obtained by SHS technology. After crushing and sieving, the fraction of particles between 20 and 63μm, have been selected for thermal spray. The obtained coatings have been characterized by XRD and SEM-EDS to
ABSRACT: A deeper understanding of the effectiveness of adopting devices mounting shape memory al... 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.
In recent years, we have studied the serious and very serious maritime accidents registered by th... 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...
5th International Conference Virtual City and Territory, Barcelona, 2,3 and 4 June 2009
Las interrelaciones y la complejidad inherente en los espacios urbanos modernos hacen difícil el ... 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...
In cold regions, the reduction in envelope thermal transmittance is often the dominant parameter ... 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...
ABSTRACT Experimental study of damping in civil engineering structures was done using smart mater... 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 tr... 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.
Shape Memory Alloys (SMA) show particular properties associated to their martensitic transformati... 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..
ABSTRACT Several solutions have been proposed to mitigate the vibrations of stay cables in bridge... 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.
The application of Shape Memory Alloy (SMA) devices to practical uses need well established perfo... 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...
The properties of SMA (Shape Memory Alloys, smart materials) are associated to a first order phas... 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.
Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC -... more Different spraying technologies (plasma and High Velocity Oxi-Fuel) have been use to obtain TiC - stainless steel or NiTi matrix coatings. The starting feedstock powders have been obtained by SHS technology. After crushing and sieving, the fraction of particles between 20 and 63μm, have been selected for thermal spray. The obtained coatings have been characterized by XRD and SEM-EDS to
ABSRACT: A deeper understanding of the effectiveness of adopting devices mounting shape memory al... 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.
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KEYWORDS: damping; fatigue life; passive control systems; shape memory alloys; vibration mitigation
KEYWORDS: damping; fatigue life; passive control systems; shape memory alloys; vibration mitigation