11,811 research outputs found

    Beam-Induced Damage Mechanisms and their Calculation

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    The rapid interaction of highly energetic particle beams with matter induces dynamic responses in the impacted component. If the beam pulse is sufficiently intense, extreme conditions can be reached, such as very high pressures, changes of material density, phase transitions, intense stress waves, material fragmentation and explosions. Even at lower intensities and longer time-scales, significant effects may be induced, such as vibrations, large oscillations, and permanent deformation of the impacted components. These lectures provide an introduction to the mechanisms that govern the thermomechanical phenomena induced by the interaction between particle beams and solids and to the analytical and numerical methods that are available for assessing the response of impacted components. An overview of the design principles of such devices is also provided, along with descriptions of material selection guidelines and the experimental tests that are required to validate materials and components exposed to interactions with energetic particle beams.Comment: 69 pages, contribution to the 2014 Joint International Accelerator School: Beam Loss and Accelerator Protection, Newport Beach, CA, USA , 5-14 Nov 201

    Parametric Study on Self-centering Precast Concrete Frames with Hysteretic Dampers

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    The self-centering precast concrete frame structure combines the advantages of industrialization and low earthquake damage, and its energy dissipation capacity and seismic performance have always been the focus of research. This paper proposed a kind of self-centering precast concrete frame with hysteretic dampers (SCPCHD). Its modular design makes the energy dissipation device and components easy to repair and replace. In order to obtain the optimal design, the finite element models of SCPCHD frames with different layout types of post-tensioned (PT) tendons and different shapes of hysteretic dampers are established, and the elastoplastic dynamic time-history analyses are carried out. The results show that the layout types and vertical margin of PT tendons have little effect on the displacement response of the frame structure. Compared to linear PT tendons, polygonal PT tendons can better bear the bending moment of the beam and reduce the stress of longitudinal reinforcements in the beam. The reduce effect of shortening the vertical margin on the tensile damage of beam concrete is obvious in the frame with polygonal PT tendons, but not obvious in the frame with linear PT tendons. Rational design of the prestressing force also plays a crucial role in the energy dissipation capacity of SCPCHD frames

    Crumbling of Amatrice clock tower during 2016 Central Italy seismic sequence: Advanced numerical insights

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    The dynamic behaviour and the seismic vulnerability of the ancient civic tower of Amatrice, dramatically damaged by the last shocks sequence of 2016 that occurred in Central Italy, have been studied in this paper by means of advanced 3D numerical analyses with the Discrete Element Method (DEM). Thus, a discontinuous approach has been used to assess the dynamic properties and the vulnerability of the masonry structure, through large deformations regulated by the Signorini's law, concerning the impenetrability between the rigid bodies, and by the Coulomb's law, regarding the dry-friction model. Afterward, different values have been assigned to the friction coefficient of the models and real seismic shocks have been applied in the nonlinear analyses. The major purpose of this study is to highlight that relevant data on the real structural behaviour of historical masonry can be provided through advanced numerical analyses. The comparison between the results of the numerical simulation and the survey of the existing crack pattern of the bell tower permitted to validate the approach used. Finally, from the results and conclusions of this case study, it is possible to affirm that the used methodology can be applied to a wide variety of historical masonry structure in Europe

    A new framework to estimate the probability of fire following earthquake

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    Fire following earthquake has been recognized as a very significant risk in the past decade. Several studies have been performed by researchers to develop analytical and experimental methods to assess the economic and life losses due to fire after an earthquake event. While the outcome of these efforts has resulted in significant advances, an accurate and simplified framework to be utilized by practicing engineers is still lacking. In this paper, a new methodology to predict the probability to have fire following a seismic event considering the building seismic damage is proposed. Earthquake was considered as the main hazard, whereas blast and fire were assumed as a cascading hazards. Bayesian approach was used to estimate conditional probability of fire caused by an earthquake. A hospital building has been assumed as case study, while a LPG tank located nearby the structure has been considered as potential source of blast and ignition. A physical-based simulation was used to evaluate intra-structure ignition probability due to leakage and/or breaks of the gas pipelines. Several parameters were considered to model the occurrence of intra-structure ignitions such as structural and non-structural damage, earthquake intensity, buildings geometry and occupancy and earthquake scenario time. proposed framework is considered a significant step to accurately predict fire risk following a seismic event with affordable time and it can be an alternative solution to the statistical ignition model currently being used in many fire following hazard methods

    Cascading Hazard Analysis of a Hospital Building

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    Recently multiple-hazards engineering has received more attention when evaluating the capacity and analyzing the behavior of a system that is exposed to more than one type of hazard. In this paper, the principle of multiple-hazards is investigated and a new methodology has been developed to assess cumulative damage of structural elements. The proposed approach is able to combine structural damage caused by sequential hazards through their conditional probability of occurrence. The damage related to each hazard has been evaluated independently. The corresponding physical models associated to each hazard have been used to assess the conditional probability of hazardā€™s occurrence. The method has been applied to a hospital located in California, US. Three hazards (earthquake, blast and fire) have been analyzed. First, non-linear time-history analyses have been performed using seven ground motions scaled to five different earthquake levels and the seismic response of the structure has been evaluated. The seismic input has damaged the hospitalā€™s power supply (LPG reservoir tank) which has caused a blast. The probability of explosion has been estimated taking into account the probabilities of fuel leakage, fuel concentration, and ignition respectively. A set of twelve blast intensity levels has been considered in the analyses, corresponding to different quantities of fuel content inside the tank. Afterwards, a fire hazard is generated following the explosion, whose intensity level has been evaluated using the compartmental heat flux. The fire effects have been modeled assuming an increment of temperature in the steel frame. The proposed multi-hazard approach can be used for both improving the structural safety and reducing the building life cycle costs to enhance in the end, the resilience of the hospital. Results show that this methodology can be used to provide risk mitigation measures within a more general resilience framework

    Resilience of critical structures, infrastructure, and communities

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    In recent years, the concept of resilience has been introduced to the field of engineering as it relates to disaster mitigation and management. However, the built environment is only one element that supports community functionality. Maintaining community functionality during and after a disaster, defined as resilience, is influenced by multiple components. This report summarizes the research activities of the first two years of an ongoing collaboration between the Politecnico di Torino and the University of California, Berkeley, in the field of disaster resilience. Chapter 1 focuses on the economic dimension of disaster resilience with an application to the San Francisco Bay Area; Chapter 2 analyzes the option of using base-isolation systems to improve the resilience of hospitals and school buildings; Chapter 3 investigates the possibility to adopt discrete event simulation models and a meta-model to measure the resilience of the emergency department of a hospital; Chapter 4 applies the meta-model developed in Chapter 3 to the hospital network in the San Francisco Bay Area, showing the potential of the model for design purposes Chapter 5 uses a questionnaire combined with factorial analysis to evaluate the resilience of a hospital; Chapter 6 applies the concept of agent-based models to analyze the performance of socio-technical networks during an emergency. Two applications are shown: a museum and a train station; Chapter 7 defines restoration fragility functions as tools to measure uncertainties in the restoration process; and Chapter 8 focuses on modeling infrastructure interdependencies using temporal networks at different spatial scales

    How to protect a wind turbine from lightning

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    Techniques for reducing the chances of lightning damage to wind turbines are discussed. The methods of providing a ground for a lightning strike are discussed. Then details are given on ways to protect electronic systems, generating and power equipment, blades, and mechanical components from direct and nearby lightning strikes

    Development of virtual cities models during emergencies

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    L'abstract ĆØ presente nell'allegato / the abstract is in the attachmen
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