The Experts below are selected from a list of 273012 Experts worldwide ranked by ideXlab platform
Massimo Fragiacomo - One of the best experts on this subject based on the ideXlab platform.
-
long Term Behavior of wood concrete composite floor deck systems with shear key connection detail
Journal of Structural Engineering-asce, 2007Co-Authors: Massimo Fragiacomo, Richard M Gutkowski, Jeno Balogh, R S FastAbstract:The paper investigates the long-Term Behavior of wood-concrete composite beams with notched connection detail. The experimental program comprised the characterization of the component materials (wood, concrete, and connection detail) and long-Term tests on beam specimens. The beam specimens were monitored during the construction process, and for an overall period of 133 days after the application of the service load. The experimental results have then been extended to the entire service life of the structure using a one-dimensional finite-element model. It was found that the increase in moisture content due to the bleeding of the fresh concrete is not an issue for the durability of the wood deck, and the type of construction (shored or unshored) does not significantly affect the structural performance. The rheological phenomena experienced by the component materials lead to quite large deflections over the entire service life, whereas the variation in stress is not significant. If the limitation of the deflection is required for serviceability considerations, the use of concrete with reduced shrinkage and the precambering of the wood deck are to be recommended. A simplified approach based on closed form solutions for composite beams with smeared flexible connectors is finally proposed for the prediction of the long-Term Behavior.
-
long Term Behavior of timber concrete composite beams i finite element modeling and validation
Journal of Structural Engineering-asce, 2006Co-Authors: Massimo Fragiacomo, Ario CeccottiAbstract:This first part of two companion papers deals with the numerical modeling of timber–concrete composite beams (TCCs) under long-Term loading. All phenomena affecting the long-Term Behavior of timber, concrete, and the connection system, such as creep, mechanosorptive creep, shrinkage/swelling, and temperature variations, are fully considered. The structural problem is solved through a uniaxial finite element model with flexible connection and a step-by-step numerical procedure over time. The important role played by the environmental thermohygrometric variations on TCCs is highlighted through some analyses. The proposed numerical procedure is validated on two long-Term experimental tests in outdoor conditions. Despite some uncertainties in environmental conditions and material properties, a good fit between experimental and numerical results is obtained. A parametric analysis is performed in the second part, showing the contribution of different rheological phenomena and thermohygrometric variations on beam deflection and connection slip. Based on results carried out, a simplified approach for long-Term evaluation of TCCs is then proposed.
-
long Term Behavior of timber concrete composite beams ii numerical analysis and simplified evaluation
Journal of Structural Engineering-asce, 2006Co-Authors: Massimo FragiacomoAbstract:This second part of two companion papers investigates the contribution of different rheological phenomena and thermohygrometric variations on long-Term Behavior of timber–concrete composite beams (TCCs) in outdoor conditions. The numerical algorithm presented and validated against two experimental tests in the first part is employed with this aim. Such a model fully considers all rheological phenomena and, therefore, leads to rigorous solutions. Effects on the beam response include the creep and mechanosorptive creep of both timber and connection, along with concrete creep and shrinkage, and may markedly increase the elastic deflection due to live load. The inelastic strains due to yearly and daily variations of environmental conditions (temperature and relative humidity) produce an important fluctuation of the deflection. A simplified method, which is suitable for practical design of TCCs under long-Term loading, is at last proposed. The effects of load, concrete shrinkage, and inelastic strains due to environmental variations are evaluated one by one using approximate formulas and are then superimposed. Creep and mechanosorptive creep are taken into account by adopting modified elastic moduli. The reliability of the proposed method is checked by way of some comparisons with numerical results. The applicability for the case of TCCs in heated indoor conditions is also discussed.
-
finite element model for collapse and long Term analysis of steel concrete composite beams
Journal of Structural Engineering-asce, 2004Co-Authors: Massimo Fragiacomo, Claudio Amadio, Lorenzo MacoriniAbstract:This paper concerns the development of a numerical procedure for studying steelconcrete composite beams with regard to both the collapse analysis and long-Term Behavior at the serviceability limit ...
Cristobal Rojas - One of the best experts on this subject based on the ideXlab platform.
-
space bounded church turing thesis and computational tractability of closed systems
Physical Review Letters, 2015Co-Authors: Mark Braverman, Jonathan Schneider, Cristobal RojasAbstract:We report a new limitation on the ability of physical systems to perform computation-one that is based on generalizing the notion of memory, or storage space, available to the system to perform the computation. Roughly, we define memory as the maximal amount of information that the evolving system can carry from one instant to the next. We show that memory is a limiting factor in computation even in lieu of any time limitations on the evolving system-such as when considering its equilibrium regime. We call this limitation the space-bounded Church-Turing thesis (SBCT). The SBCT is supported by a simulation assertion (SA), which states that predicting the long-Term Behavior of bounded-memory systems is computationally tractable. In particular, one corollary of SA is an explicit bound on the computational hardness of the long-Term Behavior of a discrete-time finite-dimensional dynamical system that is affected by noise. We prove such a bound explicitly.
-
noise vs computational intractability in dynamics
arXiv: Computational Complexity, 2012Co-Authors: Mark Braverman, Alexander Grigo, Cristobal RojasAbstract:Computation plays a key role in predicting and analyzing natural phenomena. There are two fundamental barriers to our ability to computationally understand the long-Term Behavior of a dynamical system that describes a natural process. The first one is unaccounted-for errors, which may make the system unpredictable beyond a very limited time horizon. This is especially true for chaotic systems, where a small change in the initial conditions may cause a dramatic shift in the trajectories. The second one is Turing-completeness. By the undecidability of the Halting Problem, the long-Term prospects of a system that can simulate a Turing Machine cannot be deTermined computationally. We investigate the interplay between these two forces -- unaccounted-for errors and Turing-completeness. We show that the introduction of even a small amount of noise into a dynamical system is sufficient to "destroy" Turing-completeness, and to make the system's long-Term Behavior computationally predictable. On a more technical level, we deal with long-Term statistical properties of dynamical systems, as described by invariant measures. We show that while there are simple dynamical systems for which the invariant measures are non-computable, perturbing such systems makes the invariant measures efficiently computable. Thus, noise that makes the short Term Behavior of the system harder to predict, may make its long Term statistical Behavior computationally tractable. We also obtain some insight into the computational complexity of predicting systems affected by random noise.
Mark Braverman - One of the best experts on this subject based on the ideXlab platform.
-
space bounded church turing thesis and computational tractability of closed systems
Physical Review Letters, 2015Co-Authors: Mark Braverman, Jonathan Schneider, Cristobal RojasAbstract:We report a new limitation on the ability of physical systems to perform computation-one that is based on generalizing the notion of memory, or storage space, available to the system to perform the computation. Roughly, we define memory as the maximal amount of information that the evolving system can carry from one instant to the next. We show that memory is a limiting factor in computation even in lieu of any time limitations on the evolving system-such as when considering its equilibrium regime. We call this limitation the space-bounded Church-Turing thesis (SBCT). The SBCT is supported by a simulation assertion (SA), which states that predicting the long-Term Behavior of bounded-memory systems is computationally tractable. In particular, one corollary of SA is an explicit bound on the computational hardness of the long-Term Behavior of a discrete-time finite-dimensional dynamical system that is affected by noise. We prove such a bound explicitly.
-
noise vs computational intractability in dynamics
arXiv: Computational Complexity, 2012Co-Authors: Mark Braverman, Alexander Grigo, Cristobal RojasAbstract:Computation plays a key role in predicting and analyzing natural phenomena. There are two fundamental barriers to our ability to computationally understand the long-Term Behavior of a dynamical system that describes a natural process. The first one is unaccounted-for errors, which may make the system unpredictable beyond a very limited time horizon. This is especially true for chaotic systems, where a small change in the initial conditions may cause a dramatic shift in the trajectories. The second one is Turing-completeness. By the undecidability of the Halting Problem, the long-Term prospects of a system that can simulate a Turing Machine cannot be deTermined computationally. We investigate the interplay between these two forces -- unaccounted-for errors and Turing-completeness. We show that the introduction of even a small amount of noise into a dynamical system is sufficient to "destroy" Turing-completeness, and to make the system's long-Term Behavior computationally predictable. On a more technical level, we deal with long-Term statistical properties of dynamical systems, as described by invariant measures. We show that while there are simple dynamical systems for which the invariant measures are non-computable, perturbing such systems makes the invariant measures efficiently computable. Thus, noise that makes the short Term Behavior of the system harder to predict, may make its long Term statistical Behavior computationally tractable. We also obtain some insight into the computational complexity of predicting systems affected by random noise.
Ario Ceccotti - One of the best experts on this subject based on the ideXlab platform.
-
long Term Behavior of timber concrete composite beams i finite element modeling and validation
Journal of Structural Engineering-asce, 2006Co-Authors: Massimo Fragiacomo, Ario CeccottiAbstract:This first part of two companion papers deals with the numerical modeling of timber–concrete composite beams (TCCs) under long-Term loading. All phenomena affecting the long-Term Behavior of timber, concrete, and the connection system, such as creep, mechanosorptive creep, shrinkage/swelling, and temperature variations, are fully considered. The structural problem is solved through a uniaxial finite element model with flexible connection and a step-by-step numerical procedure over time. The important role played by the environmental thermohygrometric variations on TCCs is highlighted through some analyses. The proposed numerical procedure is validated on two long-Term experimental tests in outdoor conditions. Despite some uncertainties in environmental conditions and material properties, a good fit between experimental and numerical results is obtained. A parametric analysis is performed in the second part, showing the contribution of different rheological phenomena and thermohygrometric variations on beam deflection and connection slip. Based on results carried out, a simplified approach for long-Term evaluation of TCCs is then proposed.
D N C Lin - One of the best experts on this subject based on the ideXlab platform.
-
type i planet migration in nearly laminar disks long Term Behavior
The Astrophysical Journal, 2010Co-Authors: Stephen H Lubow, D N C LinAbstract:We carry out two-dimensional high-resolution numerical simulations of type I planet migration with different disk viscosities. We find that the planet migration is strongly dependent on disk viscosities. Two kinds of density wave damping mechanisms are discussed. Accordingly, the angular momentum transport can be either viscosity dominated or shock dominated, depending on the disk viscosities. The long-Term migration Behavior is different as well. Influences of the Rossby vortex instability on planet migration are also discussed. In addition, we investigate very weak shock generation in inviscid disks by small mass planets and compare the results with prior analytic results.
-
type i planet migration in nearly laminar disks long Term Behavior
arXiv: Earth and Planetary Astrophysics, 2010Co-Authors: Stephen H Lubow, D N C LinAbstract:We carry out 2-D high resolution numerical simulations of type I planet migration with different disk viscosities. We find that the planet migration is strongly dependent on disk viscosities. Two kinds of density wave damping mechanisms are discussed. Accordingly, the angular momentum transport can be either viscosity dominated or shock dominated, depending on the disk viscosities. The long Term migration Behavior is different as well. Influences of the Rossby vortex instability on planet migration are also discussed. In addition, we investigate very weak shock generation in inviscid disks by small mass planets and compare the results with prior analytic results.
