LEAP-UCD-2017 Centrifuge Test Simulation at UNINA

Within the framework of the LEAP-UCD-2017 exercise, Type B simulations of centrifuge tests were conducted assuming a hypoplastic constitutive model for sand. Differently from the most common elastoplastic approach, the hypoplasticity does not decompose the strain rate into elastic and plastic parts and does not use explicitly the notions of the yield surface and plastic potential surface. The process followed to calibrate the constitutive model is presented in detail. The initial state of stresses in the analyzed mesh, the key parameters used in the dynamic simulation phase, and a comparison of the simulation with some experimental results are reported. All the simulations were performed using the model parameters calibrated by using the laboratory test data. Finally, a sensitivity analysis of computed displacement to soil density and ground motion intensity show the influence of such factors on the seismic soil response of liquefiable soils

Granular viscosity from plastic yield surfaces: The role of the deformation type in granular flows

Numerical simulations of granular flows with Navier–Stokes type models emerged in the last decade, challenging the well established depth-averaged models. The structure of these equations allows for extension to general rheologies based on complex and realistic constitutive models. Substantial effort has been put into describing the effect of the shear rate, i.e. the magnitude of the velocity gradient, on the shear stress. Here we analyse the effect of the deformation type. We apply the theories of Mohr–Coulomb and Matsuoka–Nakai to calculate the stresses under different deformation types and compare results to the theory of Drucker–Prager, which is formulated independently of the deformation type. This model is particularly relevant because it is the basis for many granular rheologies, such as the –rheology. All models have been implemented into the open-source toolkit OpenFOAM® for a practical application. We found that, within the context of these models, the deformation type has a large influence on the stress. However, for the geometries considered here, these differences are limited to specific zones which have little influence on the landslide kinematics. Finally we are able to give indicators on when the deformation type should be considered in modelling of landslides and when it can be neglected

On the use of stochastic spectral methods in deep excavation inverse problems

The back analysis or inverse analysis of the field instrumentation data is a common technique to ascertain the design parameter validity in deep excavation projects. That analysis is a process full of uncertainties and relies greatly on the expert judgement. Furthermore, deep excavation geotechnical models tend to be computationally very expensive making the inverse analysis a very lengthy process. In this paper, a Bayesian-type methodology to solve inverse problems which relies on the reduction of the numerical cost of the forward simulation through stochastic spectral surrogate models is presented. The proposed methodology is validated with three calibration examples.Canavate-Grimal, A.; Falcó, A.; Calderón García, PA.; Paya-Zaforteza, I. (2015). On the use of stochastic spectral methods in deep excavation inverse problems. Computers and Structures. 159:41-60. doi:10.1016/j.compstruc.2015.06.009S416015

Vibro-Injection Pile Installation in Sand: Part I—Interpretation as Multi-material Flow

The installation of vibro-injection piles into saturated sand has a significant impact on the surrounding soil and neighboring buildings. It is generally characterized by a multi-material flow with large material deformations, non-stationary and new material interfaces, and by the interaction of the grain skeleton and the pore water. Part 1 in this series of papers is concerned with the mathematical and physical modeling of the multi-material flow associated with vibro-injection pile installation. This model is the backbone of a new multi-material arbitrary Lagrangian-Eulerian (MMALE) numerical method presented in Part 2.DFG, 76838227, Numerische Modellierung der Herstellung von Rüttelinjektionspfähle

Verformungsprognosen fuer Stuetzkonstruktionen

Available from TIB Hannover: ZA 4925(141) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

The role of the brand in Relationship Management

Diese Arbeit befasst sich über notwendige markenpolitischen Maßnahmen im Relationship Management. Dies dient den Zweck um profitable Marken-Kunden-Beziehungen aufzubauen und zu erhalten