Capacity assessment of multi-storey RC walls

Phase 2 of the CASH benchmark was dedicated to the response prediction of multi-storey reinforced concrete (RC) walls used as seismic resisting members in nuclear power plants. Nonlinear static and dynamic analyses have been carried out to check the reliability of non-linear finite element analysis (NLFEA) to assess the seismic capacity of reinforced concrete walls. Authors attended the benchmark by modelling RC walls using multi-layered shell elements and by adopting a self implemented crack model. The paper describes modelling strategies and some critical issues of the Eurocode 8 prescrip-tions for the shear demand and shear capacity evaluation of multi-storey RC walls

Il fenomeno del buckling implementato nel modello fessurativo PARC_CL 2.1

Gli edifici esistenti in calcestruzzo armato, progettati prima delle attuali normative sismiche, presentano solitamente un’armatura traversale ridotta o assente che causa un cattivo confinamento dell’armatura longitudinale. Durante il sisma le armature longitudinali possono essere sottoposte ad elevate deformazioni che possono indurre lo svergolamento (“buckling”). Si rende dunque necessario l’utilizzo di un modello costitutivo per l’acciaio capace di simulare realisticamente il fenomeno del buckling. I modello analizzati nel presente lavoro sono quello formulati da Monti-Nuti e da Kashani implementati nel modello fessurativo PARC_CL 2.1. Sono stati quindi analizzati elementi in calcestruzzo armato sottoposti a carichi ciclici con caratteristiche geometriche e meccaniche tipi-che degli edifici costruiti negli anni ’70 (pre normativa sismica), simulandone il comportamento con entrambi i modelli proposti.Reinforced concrete (RC) structures, designed and built before the modern seismic codes, typically present an un-derestimated transversal reinforcement, that causes a bad confinement for the longitudinal rebars. During earthquake, longitudinal reinforcement could be subjected to high deformations inducing buckling. It is therefore necessary using a constitutive model able to realistically simulate the buckling phenomenon. In the present work, the Monti-Nuti model and the Kashani model has been ana-lyzed and implemented in the PARC_CL 2.1 crack model. Then, RC elements subjected to cyclic loads with mechanical and geo-metrical characteristics typical of 70’s buildings in Italy (before seismic codes) have been analyzed with the two proposed models.

Janus II: a new generation application-driven computer for spin-system simulations

This paper describes the architecture, the development and the implementation of Janus II, a new generation application-driven number cruncher optimized for Monte Carlo simulations of spin systems (mainly spin glasses). This domain of computational physics is a recognized grand challenge of high-performance computing: the resources necessary to study in detail theoretical models that can make contact with experimental data are by far beyond those available using commodity computer systems. On the other hand, several specific features of the associated algorithms suggest that unconventional computer architectures, which can be implemented with available electronics technologies, may lead to order of magnitude increases in performance, reducing to acceptable values on human scales the time needed to carry out simulation campaigns that would take centuries on commercially available machines. Janus II is one such machine, recently developed and commissioned, that builds upon and improves on the successful JANUS machine, which has been used for physics since 2008 and is still in operation today. This paper describes in detail the motivations behind the project, the computational requirements, the architecture and the implementation of this new machine and compares its expected performances with those of currently available commercial systems.Comment: 28 pages, 6 figure

NUMERICAL EVALUATION OF THE CORROSION EFFECTS IN PRESTRESSED CONCRETE BEAMS WITHOUT SHEAR REINFORCEMENT

Corrosion of prestressed concrete structures causes size reduction of strands, degradation of mechanical properties of steel, cracking of the surrounding concrete and bond decay at steel-to-concrete interface. In this paper, a numerical approach able to take into account all the effects involved in the corrosion process by using non-linear finite element analysis (NLFEA) and membrane or shell elements modelling, is proposed. Two different strategies are adopted to model strands: the smeared and the discrete approaches. The results obtained using these latter strategies are validated by comparing NLFEA results with experimental measurements of a naturally corroded prestressed beam tested at the “Instituto de Ciencias de la Construcción Eduardo Torroja” in Madrid. Finally, pros and cons of the proposed modelling approach are critically analysed, demonstrating that considering the actual spatial corrosion distribution is necessary to predict the position where failure occurs

Why early collective action pays off: evidence from setting Protected Geographical Indications

AbstractThe registration of Geographical Indications (GIs) under the European Union (EU) legislation requires collective action and considerable efforts borne by multiple actors such as producers, processors, public authorities and research centers. We analyze their efforts, risks and benefits by comparing two EU GI registration processes in Italy and Austria, namely the Sorana bean Protected Geographical Indication (PGI) and the Perry from Mostviertel PGI. Results from the institutional and transaction costs analysis suggest that intensive interaction for solving conflicting interests, negotiating quality standards and defining common rules might pay off in indirect benefits and reduced risks. In particular, an inclusion of diverse and heterogeneous interest groups and a high degree of direct enterprise participation along the GI application process (as observed in the Italian case) generate benefits such as trust and social cohesion, which then support the actual use of the GI label and a better implementation of associated quality standards. A supportive legal framework with assistance from public authorities can back up the community of producers not only in technical aspects, but also as mediators when conflicts seem to be difficult to solve. As there seems to be a positive relationship between the intensity and effectiveness of collective action and the likelihood of achieving broadly accepted standards and social cohesion needed for successful GI implementation, the question for future research would not be how to avoid collective efforts but how to effectively organize the interaction among heterogeneous producer groups

Simulating spin systems on IANUS, an FPGA-based computer

We describe the hardwired implementation of algorithms for Monte Carlo simulations of a large class of spin models. We have implemented these algorithms as VHDL codes and we have mapped them onto a dedicated processor based on a large FPGA device. The measured performance on one such processor is comparable to O(100) carefully programmed high-end PCs: it turns out to be even better for some selected spin models. We describe here codes that we are currently executing on the IANUS massively parallel FPGA-based system.Comment: 19 pages, 8 figures; submitted to Computer Physics Communication

Host-cell dependent role of phosphorylated keratin 8 during influenza A/NWS/33 virus (H1N1) infection in mammalian cells

In this study, we investigated the involvement of keratin 8 during human influenza A/NWS/33 virus (H1N1) infection in semi-permissive rhesus monkey-kidney (LLC-MK2) and permissive human type II alveolar epithelial (A549) cells. In A549 cells, keratin 8 showed major expression and phosphorylation levels. Influenza A/NWS/33 virus was able to subvert keratin 8 structural organization at late stages of infection in both cell models, promoting keratin 8 phosphorylation in A549 cells at early phases of infection. Accordingly, partial colocalizations of the viral nucleoprotein with keratin 8 and its phosphorylated form were assessed by confocal microscopy at early stages of infection in A549 cells. The employment of chemical activators of phosphorylation resulted in structural changes as well as increased phosphorylation of keratin 8 in both cell models, favoring the influenza A/NWS/33 virus's replicative efficiency in A549 but not in LLC-MK2 cells. In A549 and human larynx epidermoid carcinoma (HEp-2) cells inoculated with respiratory secretions from pediatric patients positive for, respectively, influenza A virus or respiratory syncytial virus, the keratin 8 phosphorylation level had increased only in the case of influenza A virus infection. The results obtained suggest that in A549 cells the influenza virus is able to induce keratin 8 phosphorylation thereby enhancing its replicative efficiency

An in-depth view of the microscopic dynamics of Ising spin glasses at fixed temperature

Using the dedicated computer Janus, we follow the nonequilibrium dynamics of the Ising spin glass in three dimensions for eleven orders of magnitude. The use of integral estimators for the coherence and correlation lengths allows us to study dynamic heterogeneities and the presence of a replicon mode and to obtain safe bounds on the Edwards-Anderson order parameter below the critical temperature. We obtain good agreement with experimental determinations of the temperature-dependent decay exponents for the thermoremanent magnetization. This magnitude is observed to scale with the much harder to measure coherence length, a potentially useful result for experimentalists. The exponents for energy relaxation display a linear dependence on temperature and reasonable extrapolations to the critical point. We conclude examining the time growth of the coherence length, with a comparison of critical and activated dynamics.Comment: 38 pages, 26 figure

Ianus: an Adpative FPGA Computer

Dedicated machines designed for specific computational algorithms can outperform conventional computers by several orders of magnitude. In this note we describe {\it Ianus}, a new generation FPGA based machine and its basic features: hardware integration and wide reprogrammability. Our goal is to build a machine that can fully exploit the performance potential of new generation FPGA devices. We also plan a software platform which simplifies its programming, in order to extend its intended range of application to a wide class of interesting and computationally demanding problems. The decision to develop a dedicated processor is a complex one, involving careful assessment of its performance lead, during its expected lifetime, over traditional computers, taking into account their performance increase, as predicted by Moore's law. We discuss this point in detail