96 research outputs found
CLIMATE CHANGE AND URBAN FORM: SIMULATION STUDIES IN TEMPERATE CLIMATES
No full textResearch summary Humanity is facing important challenges in the next years. The United Nations set of Sustainable Development Goals (United Nations, 2014), to be adopted in September 2015, underline that climate (goal 13: take urgent action to combat climate change and its impacts) and urban issues (goal 11: make cities and human settlements inclusive, safe, resilient and sustainable) are two of the most important of these challenges. Climate is changing and urban population is growing very fast, leaving many people in exposition to extreme events and making more difficult to build the cities resilience. Climate change adaptation requires the understanding of the urban response to warmer environment and heat weaves. Architectural R(solution) proposed in this paper consist in a parametrical interpretation of simulation studies, searching for more adaptable urban forms, which could respond to future modified climates. Three different temperate locations are tested (Rome, Barcelona and Antofagasta), to obtain results that could be generalized and indicate the importance of design variables like density, buildings' height, urban matrix orientation facing sun and wind, and cities' greening strategies
NiTi Wires for Dampers and Actuators: Fatigue
No full textThe singular properties of Shape Memory Alloys (SMA), which are due to a thermoelastic martensitic transformation, made them attractive for use as actuators or as dampers. The dampers could use preferably the stronger effect of the pseudoelastic window and the hysteresis on transforming- retransforming, but also other processes that are available, as damping in martensite phase (rubber-like effect). The application of SMA to practical uses need well established performance and life. The reliable application in some areas, as dampers in Civil Engineering, needs guaranteed properties. The requirements have to be clearly set to look for applicability of specific alloys, conditioning treatments, and devices. In Civil Engineering, the damping of earthquake effects might need some hundreds or one thousand of working cycles, while the damping of wind-induced vibrations would need to support many millions of cycles without failure to be useful. The required number of cycles will then limit the maximum design stresses and strains on the material to perform without failure, and these will directly influence the dimensioning of the devices.
This work deals with some results on fatigue of NiTi pseudoelastic wires, and points the possibility to apply NiTi as damper material. Fatigue has to be studied for concrete applications, with the correct samples
Built-form, mass and energy: Urban fabric performance
No full textThe link between urban form and building energy demand is a complex balance of morphological, constructive, utilization and climatic factor. Especially in the European compact city, where existing areas prevail on much more energy-efficient new settlements, it is evident that operative ways to transform efficiently the building stock have to be found. This paper explores the existence of a relation between built mass and energy demand depending on urban form. Focusing on the compact city of Mediterranean climate, tests on different case studies simulations are carried out. Results presented and discussed, point out that mass has strong relevance on energy demand and plays an important role in reducing energy consumptions. This paper is a preliminary report of an ongoing research study about one possible way to comprehend "metabolic rate" scaling law - The relationship between power and mass of a complex system in its process - concerning urban fabric. This knowledge-base could help verify the accordance with this rule on urban scale and give hints to conscious and effective built environment transformations towards more efficient conditions
Fatigue laboratory tests toward the design of SMA portico-braces
No full textA 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
Urban morphology and energy performance in the 20th century public city: the case of Rome
No full textA vivacious discussion focusing on the 20th century public housing neighbourhoods’ urban regeneration and densification amongst academics and practitioners working in architecture and urban design is ongoing. Two main focuses of analysis have been investigated: the different transformation strategies and the relationship between urban morphology and energy performance in the existing urban fabric. At present, these focuses need to be developed into an integrated approach determining tools and design methods at urban scale. Our study presents a contribution to the energy analysis and related design tools at urban scale permitting to determine more efficient conditions for the 20th century public housing neighbourhoods. It has been carried out within the public building stock of Rome which globally represents the 12% of the urban footprint: an ideal environment to test urban scale design methods for urban regeneration in Mediterranean climate. The relation between morphology and energy demand has been investigated taken into account different spatial density definitions as useful indicators to illustrate this kind of relation. Among these indicators, those more suitable to express reliable trends in relation to energy demand have been determined. The analyses have been conducted with Design Builder and Energy Plus simulation tool. This paper present and discuss results for three case studies. Building intensity (FSI) and coverage (GSI) show that density has relevance on energy demand for heating and cooling. Especially at islands scale, these indicators seem to be more adequate to describe this relation. The investigation on these kinds of performances achieved by density indicators help comprehend the different behaviours in each urban fabric. Methodological structure and the determined parametrical tools show themselves as knowledge base for aware design transformations of this housing building stock
Buildingmass and energy demand in conventional housing typologies of the Mediterranean city
No full textThe causal relation among building typology and building energy demand is a complex balance of climate, morphology, technology and use. The assessment of the relation between mass of building elements and energy demand in different housing typologies is the main goal of this study. A novel indicator, namely the Buildingmass, is introduced and tested in the Mediterranean climate region. Explorations on nine conventional housing typologies in Barcelona and Rome are carried out. Buildingmass evaluation is based on the calculation of the mass of building elements. Energy demand is assessed by modelling on multi-space dynamic thermal analysis tool. Our results point out that the Buildingmass has a strong relevance on energy, playing an important role in reducing heating and cooling demand in the Mediterranean city, as described by the proposed correlation (R2 = 0.88). Moreover, this indicator gives a more detailed characterisation of the housing stock of the Mediterranean city. The study aims at bridging the gap between urban physics and urban metabolism studies and fostering energy conservation measures for the built environment
Ms-Evolution in Cu-Zn-Al SMA. Predictable Temperature and Time Actions on Parent Phase
No full textRecently an increased interest has been noticed for order effects in Cu-based SMA. For instance, on the
transformation temperature Ms values and its evolution after heat treatments and quench type effects. Usually, the
experimental Ms values after quench fluctuate around ± 2 K. The interest for continuous actuators needs a more
reduced and, in any case, predictable fluctuation domain. In this work, by using high resolution in temperature, time
and resistance measurements on a Cu-Zn-Al alloy (1.48 e/a), the results establish a distribution of the evolution in two
main actions : a relatively short time and a long time tail effects. Two temperature dependent time constants have been
determined from the experiments, with different activation energies (13630 K and 10330 K). The two actions might be
associated to different ordering processes. Furthermore, the experimental results allow to describe a representative
model that can be used to predict the Ms evolution with temperature and time. The differences between simulated and
experimental results for the Ms is about ± 0.15 K for temperature-time evolutions near room temperature
Guaranteed behaviour of shape memory alloys : After quench and long time effects in CuZnAl SMA
No full textThe use of Shape Memory Alloys (SMA) in critical "high tech" applications such as robotics and in continuous actuators needs an increased reliability and a guaranteed behaviour lasting several years. High resolution measurements enabled to quantify the time effects of aging near room temperature on the properties of CuZnAl SMA and to modelize the macroscopic behaviour. Some structural measurements showed small changes on the material structure
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