Modeling of Masonry Structures at Multiple Scales

Zdivo je materiál použitý ve většině stavebních památek na celém světě. Spolehlivé nástroje pro analýzu zděných konstrukcí jsou zapotřebí nejen pro vyhodnocení jejich seismické zranitelnosti, ale také při návrhu opatření směřujících k obnovení či zvýšení únosnosti existujících budov, které si zaslouží ochranu. Zdivo je nelineární, heterogenní a anizotropní materiál, jehož vlastnosti silně závisejí na základních stavebních jednotkách, tedy blocích (cihlách) a maltě, a na jejich prostorovém uspořádání. Pro simulaci mechanického chování zděných konstrukcí byla vyvinuta řada modelů, které se liší mírou rozlišení. Pro velké konstrukce vede snaha o výpočetní efektivitu ke zjednodušeným modelům, charakterizovaným rozdělením zděných stěn na makroprvky. Významným zástupcem této skupiny modelů je metoda ekvivalentního rámu. Její podstatou je nahrazení zděné stěny idealizovaným rámem, přičemž panely jsou modelovány jako nosníky charakterizované odpovídajícím mechanickým chováním. Míra rozlišení může být zvýšena tím, že se každý makroprvek uvažuje jako homogenizované kontinuum s vlastnostmi, které reprodukují celkovou odezvu určitého výseku heterogenní mikrostruktury. Formulace vhodného konstitutivního zákona ale není lehkou úlohou. Tento zákon by měl fenomenologicky reprodukovat mechanické chování materiálu, včetně vzniku tahových trhlin, smykového pokluzu, drcení v tlaku a dalších jevů. Navíc tento přístup vyžaduje těžkopádnou identifikaci mechanických parametrů, které není vždy snadné určit na základě běžných laboratorních testů materiálu. K popisu role základních stavebních jednotek a jejich interakce může posloužit model formulovaný na mikroúrovni, který explicitně bere v úvahu jednotlivé bloky, maltu a rozhraní mezi nimi. Tato práce se zabývá zděnými konstrukcemi na několika úrovních rozlišení. Problémy s formulací modelů ekvivalentního rámu v případě nepravidelného rozmístění otvorů se zkoumají na základě porovnání výsledků pro ekvivalentní rámy s výsledky získanými metodou konečných prvků, o které lze předpokládat, že lépe postihuje skutečné chování nepravidelných stěn. Provedená parametrická analýza zděných pilířů modelovaných jako homogenizované kontinuum je zaměřena na posouzení vlivu tvaru a svislého tlakového zatížení na nelineární statické chování. Pozornost se pak přesouvá na jemnější úrovně rozlišení, na nichž se zkoumá lokalizace nepružného přetváření, která ovlivňuje konstitutivní zákony pro modelování zdiva na makro a mikroúrovni. Provádí se lokalizační analýza ortotropního makroskopického modelu formulovaného podle teorie plasticity s více plochami plasticity, v jejímž rámci jsou odvozeny analytické podmínky lokalizace potvrzené simulacemi metodou konečných prvků. V závěru je vyvinut mikromechanický model pro pravidelné zdivo a pomocí něj se na reprezentativním objemu materiálu analyzují lokalizační vlastnosti, ovlivněné velikostí tohoto objemu a předpokládanými směry periodicityMasonry represents the material used in the great majority of the world building heritage structures. Reliable tools for analysis of masonry structures are needed not only for seismic vulnerability assessment but also to properly design interventions to restore and strengthen existing buildings, which deserve to be preserved. Masonry is a nonlinear, heterogeneous, and anisotropic material whose properties strongly depend on its microstructure, typically composed of two phases, blocks and mortar, and on the way it is assembled. To simulate the mechanical behavior of masonry structures, numerous models have been developed, characterized by different detailing levels. For large structures, the need for computational efficiency leads to simplified models characterized by the subdivision of masonry walls in macro-elements. A notable example of this group of models is the equivalent-frame method, which consists of identifying the masonry wall with an ideal frame, where panels are modeled as beams characterized by proper mechanical behavior. The detailing level can be increased by considering each macro-element as a homogenized continuum, assuming that, at the scale of representation, masonry can be treated as a continuum having mechanical properties that reproduce the overall response of a certain portion of the heterogeneous microstructure. However, the formulation of a suitable constitutive law is not an easy task. It should phenomenologically reproduce the material mechanics, including tension cracking, shear sliding, compressive crushing, and many other aspects. Moreover, this approach requires a cumbersome identification of mechanical parameters that are not always easy to determine from basic experimental tests on the material. To consider the role of each constituent and the effects of their interactions, a microscale model can be set up, where blocks, mortar joints, and mortar-block interfaces are represented explicitly. In this work, masonry structures are studied at several detailing levels. An issue affecting equivalent-frame models, namely the presence of irregularity in the wall opening layout, is addressed by comparing equivalent-frame results with finite-element ones, which are assumed to better represent the actual behavior of irregular walls. A parametric analysis on masonry piers, modeled as a homogenized continuum, is carried out, aimed to assess the influence of the height-to-width ratio and the vertical compression load on the nonlinear static behavior. The focus is then shifted to finer scales. The localization analysis of an orthotropic macro-scale model in the framework of multi-surface plasticity is presented, deriving analytical localization conditions corroborated by finite element simulations. Finally, a microscale model for regular masonry is developed to analyze the localization properties of the representative volume element, also by investigating the role of its size and periodicity directions

LOCALIZATION ANALYSIS OF AN ORTHOTROPIC MULTI-SURFACE PLASTICITY MODEL UNDER UNIAXIAL STRESS

Numerical simulations of masonry structures are often based on continuum macromodelling approaches that need constitutive laws able to phenomenologically reproduce the behavior of the material. To capture the deformation process up to failure, appropriate softening laws are needed to take into account the contraction of the yield stress domain caused by cracking and crushing. It is well known that softening may lead to localization of inelastic strain. This paper focuses on localization analysis of an orthotropic macro-scale model in the framework of multi-surface plasticity, which describes the in-plane behavior of masonry structures. Preliminary results reported in this short paper are limited to uniaxial stress states. Analytical localization conditions are first derived for uniaxial stress states with principal axes aligned with the material axes of orthotropy. Then, localization analysis is extended to an arbitrary angle between the principal stress axes and the axes of orthotropy

Multiagent system integrating process and quality control in a factory producing laundry washing machines

Manufacturing companies are currently forced to reconsider their production processes by adopting more flexible, robust, and adaptive systems, aiming to improve their competitiveness. Multiagent systems (MASs) technology is suitable to address this challenge by providing an alternative way to design these complex systems based on the decentralization of the control functions over distributed entities. This paper describes the installation of a MAS solution in an industrial factory plant producing laundry washing machines. The installed solution focuses on the integration of quality and process control, and contributes to the maximization of the factory profitability facing changing conditions by applying self-adaptation procedures at the local and global levels. The preliminary results show improvements in the production efficiency and product quality, as well as a reduction of the scrap costs.info:eu-repo/semantics/publishedVersio

Host Galaxies of low z Radio-loud Quasars: A search of HST archives

We searched the HST archives for unpublished WFPC2 images of low redshift (z<0.5) radio loud quasars (RLQ). This led to the identification of 11 objects. We present here the results of the analysis of these images from which we derive the properties of their host galaxies. All objects are clearly resolved and their surrounding nebulosity is consistent with an elliptical galaxy model. These new data, together with previous published HST observations, form a sample of 34 sources which significantly expands all previous studies of low redshift RLQ based on HST data. For this full sample we derive the average absolute magnitude of the host galaxies =-24.01+/-0.48, and the effective radius =10.5+/-3.7kpc. No significant correlation is found between the nucleus and the host galaxy luminosity. Using the relationship between black hole mass (M_BH) and bulge luminosity we investigate the relation between M_BH and total radio power for RLQ and compare with other classes of radio sources. The overall distribution of AGN in the plane M_BH-P(radio) exhibits a trend for increasing M_BH with increasing P(radio) but with a substantial spread. RLQ occupy the region of most powerful sources and most massive BH. The quasars appear to emit over a wide range of power with respect to their Eddington luminosity as deduced by the estimated M_BH.Comment: 23 pages, 8 figures, ApJ in pres

Intelligent products: the grace experience

Product intelligence is a new industrial manufacturing control paradigm aligned with the context of cyber-physical systems and addressing the current requirements of flexibility, reconfigurability and responsiveness. This paradigm introduces benefits in terms of improvement of the entire product׳s life-cycle, and particularly the product quality and customization, aiming the customer satisfaction. This paper presents an implementation of a system of intelligent products, developed under the scope of the GRACE project, where an agent-based solution was deployed in a factory plant producing laundry washing machines. The achieved results show an increase of the production and energy efficiency, an increase of the product quality and customization, as well as a reduction of the scrap costs.info:eu-repo/semantics/publishedVersio

GRACE ontology integrating process and quality control

Multi-agent systems paradigm is a suitable approach to implement distributed manufacturing systems addressing the emergent requirements of flexibility, robustness and responsiveness. In such systems, an ontology is a crucial piece to provide a common understanding on the vocabulary used by the intelligent, distributed agents during the exchange of shared knowledge. This paper describes the design of an ontology to define the structure of the knowledge that is used within a multi-agent system integrating process and quality control in production lines for home appliances, which is being developed within the EU FP7 GRACE (inteGration of pRocess and quAlity Control using multi-agEnt technology) project. The ontology schema is validated by instantiating for a case study derived from a washing machines production line

The cosmic evolution of quasar host galaxies

We present near-infrared imaging of the host galaxies of 17 quasars in the redshift range 1 < z < 2, carried out at the ESO VLT UT1 8m telescope under excellent seeing conditions (~0.4 arcsec). The sample includes radio-loud (RLQ) and radio-quiet (RQQ) quasars with similar distribution of redshift and optical luminosity. For all the observed objects but one we have derived the global properties of the surrounding nebulosity. The host galaxies of both types of quasars follow the expected trend in luminosity of massive ellipticals undergoing simple passive evolution, but there is a systematic difference by a factor ~2 in the host luminosity between RLQs and RQQs (M_K(RLQ) = -27.55 +- 0.12 and M_K(RQQ) = -26.83 +- 0.25). Comparison with quasar hosts at similar and lower redshift indicates that the difference in the host luminosity between RLQs and RQQs remains the same from z = 2 to the present epoch. No significant correlation is found between the nuclear and the host luminosities. Assuming that the host luminosity is proportional to the black hole mass, as observed in nearby massive spheroids, these quasars emit at very different levels (spread \~1.5dex) with respect to their Eddington luminosity and with the same distribution for RLQs and RQQs. Apart from a factor of ~2 difference in luminosity, the hosts of RLQs and RQQs appear to follow the same cosmic evolution as massive inactive spheroids. Our results support a view where nuclear activity can occur in all luminous ellipticals without producing a significant change in their global properties and evolution. Quasar hosts appear to be already well formed at z ~2, in disagreement with models for the joint formation and evolution of galaxies and active nuclei based on the hierarchical structure formation scenario.Comment: Astrophysical Journal, accepted; 34 page

First detection of water vapor in a pre-stellar core

Water is a crucial molecule in molecular astrophysics as it controls much of the gas/grain chemistry, including the formation and evolution of more complex organic molecules in ices. Pre-stellar cores provide the original reservoir of material from which future planetary systems are built, but few observational constraints exist on the formation of water and its partitioning between gas and ice in the densest cores. Thanks to the high sensitivity of the Herschel Space Observatory, we report on the first detection of water vapor at high spectral resolution toward a dense cloud on the verge of star formation, the pre-stellar core L1544. The line shows an inverse P-Cygni profile, characteristic of gravitational contraction. To reproduce the observations, water vapor has to be present in the cold and dense central few thousand AU of L1544, where species heavier than Helium are expected to freeze-out onto dust grains, and the ortho:para H2 ratio has to be around 1:1 or larger. The observed amount of water vapor within the core (about 1.5x10^{-6} Msun) can be maintained by Far-UV photons locally produced by the impact of galactic cosmic rays with H2 molecules. Such FUV photons irradiate the icy mantles, liberating water wapor in the core center. Our Herschel data, combined with radiative transfer and chemical/dynamical models, shed light on the interplay between gas and solids in dense interstellar clouds and provide the first measurement of the water vapor abundance profile across the parent cloud of a future solar-type star and its potential planetary system.Comment: The Astrophysical Journal Letters, in pres

lifex-ep: a robust and efficient software for cardiac electrophysiology simulations

Background: Simulating the cardiac function requires the numerical solution of multi-physics and multi-scale mathematical models. This underscores the need for streamlined, accurate, and high-performance computational tools. Despite the dedicated endeavors of various research teams, comprehensive and user-friendly software programs for cardiac simulations, capable of accurately replicating both normal and pathological conditions, are still in the process of achieving full maturity within the scientific community. Results: This work introduces lifex-ep, a publicly available software for numerical simulations of the electrophysiology activity of the cardiac muscle, under both normal and pathological conditions. lifex-ep employs the monodomain equation to model the heart's electrical activity. It incorporates both phenomenological and second-generation ionic models. These models are discretized using the Finite Element method on tetrahedral or hexahedral meshes. Additionally, lifex-ep integrates the generation of myocardial fibers based on Laplace-Dirichlet Rule-Based Methods, previously released in Africa et al., 2023, within lifex-fiber. As an alternative, users can also choose to import myofibers from a file. This paper provides a concise overview of the mathematical models and numerical methods underlying lifex-ep, along with comprehensive implementation details and instructions for users. lifex-ep features exceptional parallel speedup, scaling efficiently when using up to thousands of cores, and its implementation has been verified against an established benchmark problem for computational electrophysiology. We showcase the key features of lifex-ep through various idealized and realistic simulations conducted in both normal and pathological scenarios. Furthermore, the software offers a user-friendly and flexible interface, simplifying the setup of simulations using self-documenting parameter files. Conclusions: lifex-ep provides easy access to cardiac electrophysiology simulations for a wide user community. It offers a computational tool that integrates models and accurate methods for simulating cardiac electrophysiology within a high-performance framework, while maintaining a user-friendly interface. lifex-ep represents a valuable tool for conducting in silico patient-specific simulations

Swift Observations of GRB 050603: An afterglow with a steep late time decay slope

We report the results of Swift observations of the Gamma Ray Burst GRB 050603. With a V magnitude V=18.2 about 10 hours after the burst the optical afterglow was the brightest so far detected by Swift and one of the brightest optical afterglows ever seen. The Burst Alert Telescope (BAT) light curves show three fast-rise-exponential-decay spikes with $T_{90}$=12s and a fluence of 7.6$\times 10^{-6}$ ergs cm$^{-2}$ in the 15-150 keV band. With an $E_{\rm \gamma, iso} = 1.26 \times 10^{54}$ ergs it was also one of the most energetic bursts of all times. The Swift spacecraft began observing of the afterglow with the narrow-field instruments about 10 hours after the detection of the burst. The burst was bright enough to be detected by the Swift UV/Optical telescope (UVOT) for almost 3 days and by the X-ray Telescope (XRT) for a week after the burst. The X-ray light curve shows a rapidly fading afterglow with a decay index $\alpha$=1.76$^{+0.15}_{-0.07}$. The X-ray energy spectral index was $\beta_{\rm X}$=0.71\plm0.10 with the column density in agreement with the Galactic value. The spectral analysis does not show an obvious change in the X-ray spectral slope over time. The optical UVOT light curve decays with a slope of $\alpha$=1.8\plm0.2. The steepness and the similarity of the optical and X-ray decay rates suggest that the afterglow was observed after the jet break. We estimate a jet opening angle of about 1-2$^{\circ}$Comment: 14 pages, accepted for publication in Ap