Artigos de Revista

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discrete element model is presented. The numerical model, created with the code 3DEC, employed a rigid block representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match the experimental natural frequencies is discussed, as well as the boundary conditions to simulate the shake table. Comparisons are made with the measured displacements at key locations, and the modes of deformation and fracture of the walls. The DEM model was able to reproduce important features of the shaking table tests. The experimental deformation and near collapse patterns were clearly identifiable in the numerical simulations, which produced displacements within the observed orders of magnitude, for the various levels of excitation.

The analysis of the shaking table test of a 3-wall stone masonry structure performed with a discreteelement model is presented. The numerical model, created with the code 3DEC, employed a rigidblock representation and a Mohr-Coulomb joint model. Joint stiffness calibration to match theexperimental natural frequencies is discussed, as well as the boundary conditions to simulate theshake table. Comparisons are made with themeasured displacements at key locations, and themodesof deformation and fracture of the walls. The DEM model was able to reproduce important features ofthe shaking table tests. The experimental deformation and near collapse patterns were clearlyidentifiable in the numerical simulations, which produced displacements within the observed ordersof magnitude, for the various levels of excitation.

Strong ground motion prediction based on finite-fault simulation requires the identification of the fault (strike, dip, length and width), source kinematics parameters (stress drop, rupture velocity and slip distribution), regional crustal properties (geometrical spreading, anelastic structure, and upper crustal amplification and attenuation parameters) and the determination of amplification effects due to the local site geology. The general purpose of this study is to understand source and attenuation properties in the Azores, by the determination of stress drop, quality factor and kappa, through records obtained by the Portuguese digital seismic and accelerometer network. Source Spectra were obtained, for each record, after correcting observed spectra from geometrical spreading and anelastic attenuation effect: quality factor was estimated based on coda decay in the time domain and the kappa parameter was estimated by fitting the high-frequency decay of the acceleration spectrum with a straight line in a log-linear scale. Mean stress drop value was obtained considering that

Purpose Urban allotment gardens (UAGs) are expandingworldwide, especially in large cities. Environmental pressures(direct and diffuse pollution, gardener practice, geogenic contamination)often result in the accumulation of potentiallyharmful trace elements in garden soils. The objectives of thisstudy were to assess the spatial variability of trace elementdistribution in UAGs from city, garden, and plot scale in fourEuropean cities; to provide a baseline understanding and identifyabnormal values under environmental pressures; and toevaluate the potential of portable X-ray fluorescence screeningas a useful tool in soil management.Materials and methods The four cities (Ayr and Greenock(Scotland), Lisbon (Portugal), Nantes (France)) provided awide range of environmental pressures on soils. The locationsof the 14 allotment gardens were identified in consultationwith the local municipality in each city to reflectvarious land uses or according to previous evaluation ofsoil quality. Soil sampling was carried out in 66 plots intotal, from which 3 datasets were produced: (i) basic soilproperties and trace element concentrations from a compositesample of topsoil for each plot (trace elements quantifiedby inductively coupled plasma

A computationally affordable modeling of dynamic fracture phenomena is performed in this study by using strain injectiontechniques and Finite Elements with Embedded strong discontinuities (E-FEM). In the present research, classical strain localizationand strong discontinuity approaches are considered by injecting discontinuous strain and displacement modes in the finite elementformulation without an increase of the total number of degrees of freedom. Following the Continuum Strong DiscontinuityApproach (CSDA), stress

This paper illustrates the capability of a viscoplastic subloading model recently proposedin reproducing strain-rate change effects in soil. The viscoplastic model used is based onthe subloading surface concept making possible the occurrence of viscoplastic strainsinside the yield surface. After a brief description of the basic principles and constitutiverelations behind the model, a numerical simulation of an undrained triaxial compressiontest on a normally consolidated reconstituted London clay with several strain-ratechanges was performed with success. This result was obtained with a general soil modelwhich did not take into account these specific temporary effects in its formulation. Theinfluence of the strain

When granular materials are applied in geotechnical works, like embankments and road pavement layers, one of the most relevant engineering properties in stability analysis is ultimate shear strength. In geotechnical engineering, the triaxial test is one of the most reliable methods available for determining ultimate shear strength. In this test, a soil specimen, compacted in laboratory or collected from exploratory soil borings, is generally used. In order to determine the strength parameters, at least 3 identical specimens are required in this test. Having 3 identical specimens, a single stage triaxial test procedure is used. If not, multistage triaxial test procedure is used to eliminate the effects of soil variability in the results. In this case, several confining pressures are applied to the same specimen. Although multistage triaxial tests have been used for soils for a long time, there is still a lack of test results for unbound granular non-traditional materials. This paper presents triaxial test results obtained from a Portuguese unbound granular non-traditional material (named as Inert Steel Aggregate forConstruction - ISAC). The triaxial tests were carried out using multistage and single stage techniques. As the results are quite well comparable, it is concluded that it is possible to determine shear strength parameters with just one specimen. Consequently, the research conducted has validated the use of multistage triaxial tests as a reliable and cost-effective alternative to the conventional single stage triaxial test in the mechanical characterization of unbound granular materials.

The availability of clean energy of wind waves is enough to meet current demand of the world, attracting researches to find devices with good performance to extract this type of energy. The oscillating water column converter is a type of device that has been extensively studied for this purpose. This paper describes a numerical analysis of an onshore oscillating water column device taking into account hydrodynamic and aerodynamic coupling, performance curves of the turbine and air pressure control by a relief valve. The numerical analyses are carried out by the Fluinco model, based on slightly compressible flow method to solve the Navier-Stokes equations, and employing the two-step semi-implicit Taylor-Galerkin method. The aerodynamic model is based on the first law of thermodynamics applied to the air column inside the chamber and on turbines similar to Pico

Les ports et autres infrastructures construits sur des côtes exposées à de fortes houles ont besoin d