15 research outputs found

    Finite Element Method for Evaluating Rising and Slip of Column–Base Plate for Usual Connections

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    Предложена конечноэлементная методика расчета деформирования и относительного проскальзывания креплений стальной колонны кжелезобетонному основанию. Рассмотрены два случая крепления: пластина приваривается к торцу колонны и крепится двумя или четырьмя анкерными болтами к железобетонному основанию. В конечноэлементной модели с использованием модифицированного метода Лагранжа учитывается растрескивание бетонного основания и эффекты трения. Деформирование бетонного основания описывается с помощью упругопластической модели сжатия материала. По результатам расчетов построены диаграммы перемещений элементов крепления.Запропоновано скінченноелементну методику розрахунку деформування і відносного проковзування кріплень стальної колони до залізобетонної основи. Розглянуто два випадки кріплення: пластина приварюється до торця колони і кріпиться двома або чотирма анкерними болтами до залізобетонної основи. У скінченноелементній моделі з використанням модифікованого методу Лагранжа враховується розтріскування бетонної основи й ефекти тертя. Деформування бетонної основи описується за допомогоюпружно-пластичної моделі стиску матеріалу. За результатами розрахунків побудовано діаграми переміщень елементів кріплення

    Fatigue limit of recycled aggregate concrete

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    This paper presents the main results of the research carried out to obtain the fatigue limit of concrete incorporating recycled aggregate from concrete. In this research, recycled aggregate concretes with partial and total coarse aggregate replacement and control concretes with different increasing water/cement ratios have been cast to study the material’s behavior in response to repeated compressive loads. The results show that, for the same water/cement ratio, the recycled aggregate concretes present a loss of stiffness higher than the control concrete. Furthermore, the use of recycled aggregate in concrete implies a reduction of the fatigue life. These differences are increased for low water/cement ratios, as in this case the main factor is the lower strength capacity of the aggregate. From the results obtained, recommendable mixtures for recycled aggregates exposed to fatigue loads are proposed

    A continuum anisotropic damage model with unilateral effect

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    International audienceA continuum damage mechanics model has been derived within the framework of irreversible ther-modynamics with internal variables in order to describe the behaviour of quasi-brittle materials under various loading paths. The anisotropic character induced by the progressive material degradation is explicitly taken into account, and the Helmholtz free energy is a scalar function of the basic invariants of the second order strain and damage tensors. The elastic response varies depending on the closed or open configuration of defects. The constitutive laws derived within the framework of irreversible thermodynamics theory display a dissymmetry as well as unilateral effects under tensile and compressive loading conditions. This approach verifies continuity and uniqueness of the potential energy. An application to uniaxial tension-compression loading shows a good adequacy with experimental results when available, and realistic evolutions for computed stresses and strains otherwise

    GAP IN A LASER FREQUENCY He-Ne AT 632.8 nm

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    <p>The aim of this work is to show that the emitted signals of a double-output laser cavity exhibit distinctive features, manifesting themselves through typical dissymmetry in the corresponding spectral line shapes. Usually, such a dissymmetry in an inhomogeneously broadened gas laser appears with a clear but unpredictable shift of the maximum intensity level either towards the high or towards the low frequency sides with respect to line centre. In the case of a double-output laser, the spectral profiles show opposite shifts. This means that when the maximum intensity of one output moves towards the high frequency side of the profile, the maximum intensity of the other moves towards the low frequency side. This gives rise to a frequency shift, with respect to the Lamb-dip for a classical laser</p>On the theoretical side, we apply the standard disturbed Gaussian beam model to give a good quantification of the frequency shifts obtained at both sides of the syste

    Finite element method for the rising and the slip of column-plate base for usual connections

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    In the present paper, a finite element approach calculating the rising and the relative slip of steel base plate connections is proposed. Two types of connections are studied, the first consists on a base plate welded to the column end and attached to the reinforced concrete foundation by two anchor bolts. These bolts are placed on the major axis of the I shaped section used as column, one anchor bolt on each side of the web. In the second configuration, the connection includes a plate base and four anchor bolts placed out side the flanges of the I shaped section or hallow form. To take in account the real behaviour of this connection, a model by finite elements which considers count geometrical and material no linearties of the contact and cracking in the concrete foundation. To study the rising of the base plate, an approach treating problems of contact-friction between the base plate and the foundation is developed. This approach is based on a unilateral contact law in which a Coulomb friction is added. The numerical resolution is ensured by the increased Lagrangien method. For the behaviour of the concrete foundation, the developed model is based of a compressive elastoplastic model. The heights rising-rotations and the heights rising- slip displacements curves are plotted

    prisma-v2: Extension to Cloud Overlay Networks

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    International audienceIn this paper, we present prisma-v2, a new release of prisma, a Packet Routing Simulator for Multi-Agent Reinforcement Learning. prisma-v2 brings a new set of features. First, it allows simulating overlay network topologies, by integrating virtual links. Second, this release offers the possibility to simulate control packets, which allows to better evaluate the overhead of the network protocol. Last, we integrate the modules along with the core (ns-3) to a docker container, so that it can be run in any machine or platform. prisma-v2 is, to the best of our knowledge, the first realistic overlay network simulation playground that offers to the community the possibility to test and evaluate new network protocols

    Packet Routing Simulator for Multi-Agent Reinforcement Learning (PRISMA) (Version v0.1)

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    PRISMA (Packet Routing Simulator for Multi-Agent Reinforcement Learning) is a network simulation playground for developing and testing Multi-Agent Reinforcement Learning (MARL) solutions for dynamic packet routing (DPR). This framework is based on the OpenAI Gym toolkit and the ns-3 simulator.The OpenAI Gym is a toolkit for RL widely used in research. The network simulator ns–3 is a standard library, which may provide useful simulation tools. It generates discrete events and provides several protocol implementations.Moreover, the NetSim implementation is based on ns3-gym, which integrates OpenAI Gym and ns-3.The main contributions of this framework: 1) A RL framework designed for specifically the DPR problem, serving as a playground where the community can easily validate their own RL approaches and compare them. 2) A more realistic modelling based on: (i) the well-known ns-3 network simulator, and (ii) a multi-threaded implementation for each agent. 3) A modular code design, which allows a researcher to test their own RL algorithm for the DPR problem, without needing to work on the implementation of the environment

    Estimation of the Wind Energy Potential in Various North Algerian Regions

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    This investigation aims to model and assess the wind potential available in seven specific regions of North Algeria. These regions, i.e., Batna, Guelma, Medea, Meliana, Chlef, Tiaret, and Tlemcen, are known for their traditional agriculture. The wind data are obtained from the National Agency of Meteorology (NAM), and a Weibull distribution is applied. In the first part of this study, the wind potential available in these sites is assessed. Then, different models are used to estimate the wind system’s annual recoverable energy for these regions. We are interested in wind pumping for possible use to meet the needs of irrigation water in rural areas. Four kinds of wind turbines are explored to determine the possibility of wind energy conversion. In addition, the effects of the heights of the pylon holding the turbines are inspected by considering four cases (10, 20, 40, and 60 m). This estimation showed that the annual mean wind velocity varies from 2.48 to 5.60 m/s at a level of 10 m. The yearly values of Weibull parameters (k and c) at the studied sites varied within 1.61–2.43 and 3.32–6.20 m/s, respectively. The average wind power density ranged from 11.48 (at Chlef) to 238.43 W/m2 (at Tiaret), and the monthly wind recoverable potential varied from 16.64 to 138 W/m2
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