Browsing by Issue Date, starting with "2011-05"
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- Blind Prediction of a Full-Scale RC Bridge Column Tested Under Dynamic ConditionsPublication . Bianchi, Federica; Sousa, Romain; Pinho, RuiThe definition of appropriate modelling approaches combined with a consistent software framework is a topic of major importance in the present days for structural engineering in general and, particularly, for earthquake engineering. The accuracy of the results obtained in the recent “Concrete Column Blind Prediction Contest 2010” for a full-scale reinforced concrete bridge column tested on the NEES Large High-Performance Outdoor Shake Table, seems to indicate that current modelling strategies are on the right track. The 1.2 m diameter cantilevered column spans 7.2 m from the footing. A massive 230 tonne reinforced concrete block supported by the column generates the inertial forces to mobilize the column capacity. Seismic performance was investigated under 6 ground motions, starting with lowintensity shaking and bringing the column progressively to near-collapse conditions. Based on the obtained results from the pre-contest simulation, as well with the post-contest analysis, it was possible to extract some important conclusions regarding the application of several strategies, namely the use of different type elements, element discretization, constitutive laws for materials.
- Modelling Issues on Seismic Assessment of Irregular RC StructuresPublication . Sousa, Romain; Bianchi, Federica; Pinho, Rui; Nascimbene, Roberto; Kazantzidou, DanaiMany existing RC structures worldwide were designed for gravity loads only, with inadequate lateral load resistance, lateral stiffness and poor detailing of the reinforcement. Moreover, the concept of regularity both in plan and elevation that characterise a good conceptual design was, in most cases, not taken into account. The introduction in Europe of the regulations for seismic assessment of existing structures imposed stricter performance requirements for building structures. In order to take into account the poor seismic behaviour of such buildings, recent seismic codes – namely EC8 and NTC08 (Italian code), introduce a number of prescriptions regarding issues such as analysis type, load distribution, accidental eccentricity, etc. At the same time, these codes give room for engineering judgment to be used with reference to the definition of structural and nonstructural elements such as slabs or infill walls, and obviously leave it up to the analyst decisions regarding Finite Elements typology, meshing, mass modelling, etc. The main goal of this work is thus to provide an extensive and wide evaluation on the influence of each of the abovementioned parameter on the seismic assessment of structures. For this purpose, nonlinear static procedures, as well as nonlinear dynamic analysis are performed on a real building that has also been experimentally tested in the past. The results will hopefully provide indications on the relative importance of each modelling parameter or decision.
- Liderança e autonomia. Da teoria progressista à prática retrógradaPublication . Silva, José ManuelA comunicação aborda a emergência do novo modelo de autonomia, administração e gestão das escolas e agrupamentos dos ensinos básico e secundário, estabelecido pelo Decreto-Lei n.º 75/2008 e aprofunda a reflexão sobre as questões da liderança, autonomia e poder nas escolas, os seus reflexos nas relações com parceiros da comunidade local e as contradições decorrentes de permanecer intocado o modelo centralizado de gestão macro dos estabelecimentos de ensino estatais.
- libboincexec: A Generic Virtualization Approach for the BOINC MiddlewarePublication . Ferreira, Diogo; Araujo, Filipe; Domingues, PatricioBOINC is a client-server desktop grid middleware that has grown to power very large computational projects. BOINC clients request computing jobs to a central server and run them alongside other regular applications. Unfortunately, this kind of execution causes two kinds of problems. Firstly, developers must port their application to every single operating system target, which usually means maintaining several different versions of the same application. Secondly, any application running natively on desktop grid hardware is a potential security threat to the volunteer client. During the course of this research we sought an efficient and generic method for alternative execution of jobs in BOINC clients. Our approach is strongly guided by the principles of non-intrusiveness and contains two main components. The first is a library, libboincexec, which is able to control several virtual machines monitors. The second is a modified BOINC wrapper that provides the glue between libboincexec and the middleware. Through the use of this solution we are able to effectively use virtual machines to perform computation on desktop grids. This computation is inherently safe because virtual machines provide sand boxing. Additionally, by targeting the same virtual operating system, the problem of maintaining different versions of an application does not exist, thereby solving the heterogeneity problem of desktop grid nodes.