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Numerical Modelling of Unreinforced Masonry Infill Walls under Seismic Load Considering In-Plane / Out-Of-Plane Interaction
Get PDFMany studies and post-earthquake investigations have recognized that masonry infill walls play a major role in the seismic response of structures. Although their effect may be beneficial in some situations, the walls are also susceptible to high levels of damage, including collapse that can be life-threatening because of the heavy debris. Despite the critical importance of infill walls for life safety, infill walls are often neglected in numerical models and analyses implemented by designers because they are traditionally considered to be non-structural elements. Moreover, the majority of experimental studies and numerical models include only the in-plane behaviour of the panels: indeed, until recently, only sophisticated micro-models incorporated the out-of-plane response of unreinforced masonry infill walls. Recently, however, researchers have started to advance proposals for simplified macro-models that are capable of modelling in-plane/out-of-plane interaction, paving the way for the consideration of the associated issues in design practice. However, very few studies have applied these models to the dynamic seismic response history analysis of realistic structures.
In this context, this thesis focuses on the numerical modelling of unreinforced masonry (URM) infill walls, with particular attention to the combined in-plane/out-of-plane response of panels in reinforced concrete (RC) frame buildings during seismic events.
In the first part of this research, existing studies for URM masonry infill walls are reviewed, with an emphasis on the out-of-plane response of the panels. Significant experimental tests, modeling strategies and post-earthquake surveys are presented, stressing the parameters that influence the behaviour of the infills. An in-depth description is dedicated to the infill wall macro-model that is adopted for the analyses performed in this work, emphasizing its capabilities and limitations. This model consists of a single diagonal formed by two beam elements representing the wall; lumped modal mass is concentrated at the midpoint node of the diagonal. In-plane axial force and out-of-plane bending of the equivalent element interact by means of two fibre sections located adjacent to the central node. User defined domains limit axial/bending strengths and in-plane/out-of-plane ultimate displacements of the wall. When the response of an element exceeds these domains, the model simulates the collapse of this infill wall by removing it from the analysis.
Next, the numerical model is calibrated in the OpenSees software framework by comparing existing experimental results with numerical outputs. The laboratory tests comprise in-plane cyclic and out-of-plane quasi-static results on 1-bay and 1-storey frame specimens with two different types of clay URM infill walls that are frequently found in Italian and other Mediterranean countries. The calibrated model is then applied to the static pushover analysis of a set of planar frames, while the wall elements are simultaneously loaded in both orthogonal directions.
The nucleus of present study is the application of the calibrated model to the dynamic response history analysis of planar RC frames. Frame dimensions, number of stories, design and infill configurations are selected to be representative of the Italian building stock. Acceleration time histories consist of a suite of a bidirectional ground motions that are scaled to be compatible with Eurocode 8 elastic spectra. Cracking and collapse of the infill walls are monitored during the analysis. The infill walls reach their ultimate displacement capacity by a combination of in-plane and out-of-plane displacements, with the out-of-plane component usually playing the dominant role. The intensity of seismic load that is required to fail the infill walls, as well as the patterns of failure, are shown to be consistent with observed damage to URM infill walls in similar buildings during recent earthquakes.
This research suggests that simplified macro-elements are suitable for design-oriented models of URM infill walls in RC framed structures, capturing the critical interaction between in-plane and out-of-plane response of the infill walls but without making the models excessively complex
Persuasive Technologies for Active Ageing
No full textMost of the world countries are challenged with a large ageing population who spend most of their time at home and are mostly sedentary (8.5 hours per day as of today). Sedentary behavior and physical inactivity affect the social, physical and mental states of people leading to social isolation and physical declines and hence an ideal candidate for chronic and degenerative diseases.
To maintain an active aging process (healthy state of physical, mental and social wellbeing), regular and daily exercising is necessary. However, many older adults do not maintain regular exercising due to poor health, lack of company, lack of motivation, lack of transportation and suitable outdoor facilities. In this context, home based physical exercises can help people maintain their physical activity and ICT can act as a key player and facilitator by providing interactive training applications (through desktops and mobile devices), self-monitoring (using activity trackers and wearables) and automated coaching (using rule-based systems or remote assistance). Yet, for many people and, in particular, the sedentary older population at home; even with the existence of the technology, there is not enough motivation to maintain a regular exercising routine. Thus, this thesis aims to investigate the IT-mediated persuasive strategies that help independent-living older adults at home to maintain a regular exercising lifestyle. In particular, this research examines the effect of social inclusion and group exercising on the motivation of trainees at home to adhere to the training program which has proven to be effective
Development of a squeezed light source prototype for Advanced Virgo
No full textA century after the prediction of the existence of gravitational waves by A. Einstein and after over fifty years of experimental efforts, gravitational waves have been detected at Earth directly. This result is a major achievement and opens new prospectives for the exploration of our universe. Gravitational waves carry different and complementary information about the source with respect to electromagnetic signals. In particular the first detection demonstrated the existence of stellar-mass black holes, binary systems of black holes and their coalescence.
The detection was made by the LIGO instruments which are twin kilometer-scale Michelson interferometers in the US. These detectors represent the second generation of gravitational wave interferometers and, for the first time, they achieved the outstanding strain sensitivity of 10^(-23) Hz^(-1/2) between 90Hz and 400Hz. In the next months the LIGO network will be joined by another second generation detector: Advanced Virgo located near Pisa, Italy. The sensitivity of these advanced detectors is set by different noise sources. In particular, in the low frequency range (below 100Hz) major contributions come from thermal noises, gravity gradient noise and radiation pressure noise; instead, the high frequency band (above 100-200Hz) is dominated by shot noise. Quantum noise (radiation pressure and shot noise) is expected to dominate the detector sensitivity in the whole frequency band at the final target laser input power. To decrease the shot noise while increasing the radiation-pressure noise, or vice-versa, Caves \cite{Caves1981} proposed in 1981 the idea of the squeezed-state technique. The LIGO collaboration demonstrated for the first time in 2011 that the injection of a squeezed vacuum state into the dark port of the interferometer can reduce the shot noise due to the quantum nature of light. This result was achieved with the German-British interferometer GEO600 and was replicated in 2013 with the LIGO interferometer at Livingston. After these results, the LIGO collaboration have pursued further the research in the squeezed-state technique which is considered mandatory for third generation of ground based interferometric detectors. In 2013, the Virgo collaboration started developing the squeezed-state technique. The subject of my thesis is the realization of a prototype of frequency independent squeezed vacuum state source to be injected in Advanced Virgo. This prototype is developed in collaboration with other Virgo groups
Neue Armut, Exklusion, Prekarität. Armutspolitische Debatten im deutsch-französischen Vergleich, 1970 - 1990
No full textLa straordinaria crescita economica conosciuta dalla Franca, dalla Repubblica Federale Tedesca così come da quasi tutti i paesi europei nei tre decenni che seguirono la Seconda guerra mondiale, subì una fine repentina a causa dell’impennata dei prezzi del petrolio nel 1973 e nel 1979/80. A questo periodo di crescita spettacolare succedettero anni di recessione economica nei quali la disoccupazione divenne un fenomeno di massa e la povertà si estese al punto da colpire ampie fasce della popolazione, fasce che prima si ritenevano al riparo dal rischio della povertà.
Il presente progetto di Dottorato si propone di indagare il modo in cui il dibattito pubblico affrontò, elaborò e comunicò la crescita della povertà e la disoccupazione nel periodo della recessione. Attraverso lo studio comparato di Francia e Germania si tratterà di analizzare come furono comunicati i rischi sociali nei due Paesi, quali cause furono trovate, come vennero elaborate, e quali possibili soluzioni furono negoziate per risolvere il problema della nuova povertà.
Il progetto della tesi rientra nell’ambito della comunicazione politica come conflitto su norme dell’IGK ed è parte della ricerca sulla sicurezza sociale come costruzione comunicativa. Quest’ultima muove dalla tesi per cui sullo sfondo della comunicazione sui nuovi rischi della vita sociale sarebbero riconoscibili le diverse strade prese dai paesi europei in fatto di sicurezza sociale. Conformemente a questa tesi, il progetto si propone di spiegare i diversi sviluppi dello stato sociale in Germania e in Francia a partire dagli anni Settanta muovendo da un’analisi comparata della comunicazione dei nuovi rischi sociali
Flow and thermal regimes in river networks: effects of hydropower regulation and climate extremes
Get PDFInteractive impacts of climate change and human activities (e.g. hydropower production) have posed urgency in examining the patterns of hydrological and thermal response in riverine ecosystems, and the potential ecological implications manifested. Hydro-geomorphic conditions are the major factors in shaping water qualities in river networks, especially under the extreme climatic events. However, when the power of nature is encountered with human regulations, represented by hydropower production, it would be well worth discussing how the pictures of riverine hydro- and thermal regimes would change over the certain range of time and space. Moreover, the possible utility of hydropower regulation as mitigation of extreme climate changes is still open question to be verified.
Above-mentioned questions are answered in three aspects specifically:
• Governing factors and spatial distribution model for water residence time in river networks across Germany. Based on the machine learning technique of boosted regression trees (BRT), spatial distribution of water residence time is estimated for the long-term annual average hydrological conditions and extreme cases of flood and drought.
• Impacts of hydropower over temporal and spatial range are investigated by analyzing the mechanisms of hydropeaking propagation. Hydrologic and geomorphic contribution framework is proposed and applied for the upper Rhone River basin in Switzerland, a typical hydropower exploited river basin in the mountainous area.
• River water temperature response as an indication for ecological status is investigated for the alpine rivers across Switzerland, excellent representatives of sensitivity and vulnerability to climate change while under highly exploitation of hydropower activities. Extreme climate change case of heatwaves in 2003 and 2006 are selected and analysed especially.
Results of the three research components in correspondents to listed research questions showed that river hydrological regimes have more directly/important influence on the variation of flow availability in comparison with the geomorphologic settings. Nevertheless, geomorphologic and topologic conditions (e.g. river width, slope, and roughness coefficient) that largely control the hydraulic waves diffusion processes in a hydropower-dominated river basin determine the spatial range of hydropeaking impacts. A hierarchy framework of geophysical obstructions, hydrology, and hydraulic waves diffusion process is proposed for analyzing the spatial range of hydropeaking propagation. When the effects of hydropeaking and thermopeaking that induced by hydropower production activities are dominated in the river reach, hydropower regulation offers as great potential to mitigate extreme climate events (i.e. heatwaves).
By looking into specific perspective of river hydro- and thermal regimes, hydropower regulation, and climate extremes via different scales, we investigated the interactive effects between riverine ecosystem and human-climatic impacts. We expanded the approach of water residence time estimation into the field of machine learning with spatial predictions. Impacts of hydropower regulation are first elaborated with a framework of hydropeaking propagation mechanisms. Hydropower regulation has been identified to have great potential to mitigate extreme heatwaves through altering thermal regimes in rivers. Results of the study not only contribute to river hydrology and ecology studies, but also to the river management and climate change mitigation practices
Powder metallurgy: investigation of metallurgical and technological aspects and potential applications for critical components of turbomachineries
Get PDFThe application of powder metallurgy (PM) technologies to the manufacturing of Oil & Gas turbomachineries’ components was investigated in the course of research collaboration with the Material and Processes Engineering Department of General Electric Oil & Gas (Italy). The thesis focused on the study of the pressure-assisted Hot Isostatic Pressing technology for the processing of the corrosion resistant Ni-base alloy N07626. The densification behaviour of the N07626 metal powder in condition of pressure assisted sintering was investigated by experiments conducted on a small scale by uniaxial hot pressing condition using a Spark Plasma Sintering (SPS) machine in the aim of extending the result to the initial stage of densification of HIP. The SPS exepriments demonstrated that the densification rate is strongly affected by the process temperature and it is less sensitive to the variation of applied pressure.
The microstructure and mechanical properties of full-dense HIPped N07626 alloy, produced according to a fixed proprietary cycle and several experimental deviations were analyzed. The microstructure was studied by Optical Metallography, Scanning Electron Microscopy, Energy Dispersed X-Ray Spectroscopy and Electron Backscatter Diffraction. The mechanical properties of the alloy were assessed by tensile testing, conventional and instrumented Charpy V-Notch testing, JIC fracture toughness tests and fatigue crack growth rate testing. The tensile and impact toughness properties resulted sensitive to the local accumulation of oxygen in Oxygen Affected Zones (OAZs), that leads to a ductile to brittle transition in the impact toughness of the material. Two models for formation of OAZs were proposed based on the phase transformation and the oxidation/reduction reactions taking place in the HIP. The mechanical properties were discussed on the base of the microstructure of the Prior Particle Boundaries (PPBs) interface, focusing of the phase transformation products, represented by a thin layer of submicrometric oxides and carbides. The fracture mode was explained by the analogy with models of ductile micro-mechanisms of void nucleation and coalescence and with fracture models of particulate reinforced metal-matrix-composite. The Charpy impact toughness and the fracture toughness were correlated to the oxygen concentration and to the density of inclusions. The fatigue crack propagation behavior was discussed focusing on the effect of clustering of inclusions on the crack propagation path. A relation between the Paris slope with the impact toughness was found. Finally the increase of processing temperature (HIP and heat treatment) was found significanty beneficial for the toughness. This effect was investigate by grain-size analysis and was proposed to be related to a reduction of density of PPBs inclusions
Development of a design procedure accounting for the anisotropy of the dimensional change in Powder Metallurgy parts
Get PDFThe dimensional control is a crucial aspect for any manufacturing process. In Powder Metallurgy, and in particular in net shape press and sinter process, dimensional control assumes a particular relevance, since sintering of green parts involves dimensional variations that can be from 0 to 2-3% in volume. The dimensional variation in sintering is either shrinkage or swelling. Both depend on the material and on several process parameters relevant to the compaction and the sintering operations.
Experimental evidences proved dimensional variations to be affected by an anisotropic behavior. This important phenomenon affects the effectiveness of the dimensional control if not opportunely taken into consideration in the design process. Professor Ilaria Cristofolini and Professor Alberto Molinari have started a deep investigation on this phenomenon, about five years ago, involving an important experimental campaign. The main idea is to collect a large quantity of data, both on ad-hoc designed samples and on parts produced by qualified PM companies cooperating with the University of Trento. The purpose is to develop a realistic model, able to explain and describe the mechanisms involved in the anisotropy of dimensional changes, and the dependence on the geometry of the parts, building a robust knowledge to improve the design methodologies in the industrial production. The present work investigates the effect of the geometrical characteristics of the part on the dimensional variations in sintering, giving a particular importance on its anisotropic behavior. The influence of geometry has been investigated using rings and disks with varying heights, external diameters and internal diameters. The influence of the sintering temperature has been also evaluated. The dimensional variation has been measured by a tri-dimensional Coordinate Measuring Machine. The anisotropy has been defined through a specifically determined parameter, which has been used to develop a predictive model estimating the anisotropy of the dimensional variations. This model has been then validated on complex parts produced by a Powder Metallurgy company
Ab initio calculations of hadronic and electromagnetic reactions for few-body systems
No full textA study of methods in few-body nuclear physics is presented, in particular for the study of the photodisintegration cross section of 3He at low energies, and for the determination of phase shifts in low-energy three-body scattering. A possible extension of the methods considered to the study of a five-body problem is investigated
Low-impact friction materials for brake pads
Get PDFState-of-the-art friction materials for applications in disc brake systems are constituted by composite materials, specifically formulated to ensure proper friction and wear performances, under the sliding contact conditions of braking events. The bases of typical friction compound formulations usually include 10 to 30 different components bonded with a polymeric binder cross-linked in situ. Main requests to be fulfilled during braking are an adequate friction efficiency and enough mechanical resistance to withstand the torque generated by forces acting on the disc brake. Generally, each component confers distinctive properties to the mixture and their primary function can be classified in the following categories: binders confer mechanical strength to friction material guaranteeing pad compactness during use, abrasives increase friction efficiency and improve compound wear resistance, solid lubricants are responsible for stabilizing friction coefficient and contrasting the build-up effect, reinforcements increase mechanical strength improving wear minimization and stabilization. Furthermore, other modifying components such as fillers and functionalizers are involved which are not directly related to friction efficiency, e.g. cheap materials, pigments, etc. Organic brake pads for disc-brake applications are based on phenolic resin binders, generally it requires three main manufacturing steps: raw material blending, where friction compound components are mixed by blenders. Hot-molding, where blended friction mix is pressed against a metallic support at controlled high pressure (>2kN/cm2), temperature (150-200 °C) and pressing time (3-10 minutes). Brake pads post-curing, to complete the hardening of polymeric binder. This last step for phenolic resin is usually performed in a batch convective oven at temperature above 150 °C for 4-12 h, or alternatively using a continuous process, such as IR in-line tunnel ovens where the process time is 10-15 min, the oven heater temperature is between 500 and 700 °C and brake pad superficial temperature is easily above 300 °C. Such kind of formulations and manufacturing process reflects the generally acknowledged state of the art as regards organic friction materials for passenger cars and light trucks. In this panorama the idea of introducing a completely inorganic binder matrix would represent nowadays an extremely appealing topic in the field considering potential improvements of this alternative approach.
The complete elimination of the organic binder would reduce emission of phenol-formaldehyde hazardous derivatives generated at high-temperature e.g. volatile organic compounds, highly toxic polyaromatic hydrocarbons etc… Nature and toxicity of the organic compounds released at high temperature was investigated on brake pads manufacturing and compared with preliminary studies recently published. Introducing an inorganic hydraulically bonded matrix in place of the traditional organic-based binders would lead to a substantial reduction of the total embodied energy and water of brake pads considering low-temperature manufacturing process and inorganic binders properties. Primary production embodied energy for phenolic resin is estimated in the range of 75 - 83 MJ/kg (cradle to gate), while primary production water usage (embodied water) is in the range of 94 - 282 l/kg. As a matter of comparison, examples of the embodied energy for inorganic binders typically used for concrete construction are: Portland cements 4.9 MJ/kg, fly ash 9.3 MJ/kg, metakaolin 1.4 MJ/kg, silica fume 0.036 1.4 MJ/kg. The embodied water for these raw materials usually is less than 0.048 l/kg. Well-known properties of such peculiar inorganic materials exploiting the hydraulic activity of binders when exposed to water or alkaline environment. The only energy demanding compound was the alkaline solution (e.g. for sodium hydroxide and sodium silicate the embodied energy is respectively of 22MJ/kg and 16 MJ/kg). New brake pad manufacturing process allowed the substitution of commonly implied highly energy-consuming procedures with low-temperatures steps. Friction material components except binders were blended together with conventional plow-blade blender forming a dry friction-mix, then this dry friction-mix is blended with the inorganic binder and water or alkaline activators in a planetary mixer forming a wet friction-mix. Eventually wet friction mix is cold-pressed onto a metal back-plate without the need for further treatments at high temperature. It immediately emerges the energetic benefit connected to the manufacturing process of this inorganic binder-based brake pads. After brake pad production, the behavior of these inorganic materials was compared to traditional phenolic-based friction materials. Brake pads were tested on a full scale automotive brake dynamometer and on a real vehicle (in terms of performance and particle emission) following custom and international standard procedures. The aim of this work was to produce brake pad prototypes with friction material based on an inorganic hydraulic binder at performance comparable to commercial brake pads with organic-matrix based friction materials. The results obtained so far resulted particularly promising and paved the way to further developments of these novel class of friction materials
Il Gravettiano dell'Italia tirrenica nel contesto mediterraneo: definizione delle strategie di insediamento e mobilità attraverso lo studio delle materie prime e delle industrie litiche
Get PDFThe Gravettian is the second chrono-cultural complex of the Upper Paleolithic after the Aurignacian. The Gravettian diffusion, throughout Europe, took place in a short span of time between 30.000 and 20.000 years BP. During this period, the climate instability due to the LGM approach created different environments. Particularly, Italy was split in two regions separated by the Apennine mountains: the cold and arid Adriatic coast on the first hand and the more temperate Tyrrhenian coast on the other hand. The latter region is the main object of this research. With the aim to understand the development and the mobility strategies used by the Gravettian groups in this area, several lithic assemblages have been analyzed. Specifically, the Gravettian sequence of Riparo Mochi (Balzi Rossi, Liguria - Italy), providing one of the most important stratigraphy of the Italian Upper Paleolithic, has been entirely studied. Inside the Balzi Rossi archaeological complex a direct comparison has been provided by the Gravettian collection of Grotta dei Faniculli. Moreover, some other smaller collections coming from the Provence area have been studied, allowing a comparison with the Balzi Rossi area. Finally, the site of Bilancino located in Tuscany let to contextualize the Gravettian between the liguro-provençal arc and Italy. The relation between techno-typological aspects and the raw materials provenance gives important advances in our comprehension of the behavior of the hunter-gatherer groups who inhabited the sites, discussing the timing and territorial mobility of the Tyrrhenian Gravettian