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  • The use of dissipated energy at modeling of cyclic loaded saturated soils
    Lenart, Stanislav
    The energy concept for the analysis of densification and liquefaction of cohesionless soils was first introduced by Nemat-Nasser and Shokooh (1979). Itis based on the idea that during deformation of ... these soils under dynamic loads part of the energy is dissipated into the soil. This dissipated energy per unit volume is represented by the area of the hysteric strain-stress loop and could be determined experimentally. It considers both the amplitude of shear strain and the number of cycles, combining both the effects of stress and strain. Using the Palmgren-Miner cumulative damage hypothesis, the effect of random motions of an earthquake or other random dynamic load can be taken into account by dissipated energy use. The main advantage of using the dissipated energy was found in case of saturated soils. The relation between dissipated energy and the excess pore water pressure generated in saturated soils during dynamic loading is already well known. Recent studies have shown that similar relations exist also in the case of hydrodynamic pore pressures. Besides relations between dissipated energy and pore pressure changes in saturated cyclic loaded soils, the paper highlights also the relation between dissipated energy and softening of soil during cyclic loading. Softening of soil during cyclic loading, so-called short-term flow, makes a perceivable impact on strain progression. After few cycles of loading soil starts to exhibit very low stiffness at the beginning of a load cycle and it strengthen latter. It is obviously that strain developed during this short-term flow presents the main share of a total strain developed during cyclic loading and it leads therefore the deformation behavior of a soil. The duration of this phenomenon and stiffness of soil during this phase is in the question. It hasbeen found that the duration of softening phase, as well as shear modulus of soil during this phase are both related to residual pore pressure ratio. A simple constitutive model, especially suitable for a cyclic mobility modeling,was developed based on an energy approach. Its main part presents a new pore pressure generation model and findings related to short-term flow anddissipated energy.
    Vir: Earthquake engineering : new research (Str. 295-321)
    Vrsta gradiva - članek, sestavni del ; neleposlovje za odrasle
    Leto - 2009
    Jezik - angleški
    COBISS.SI-ID - 1435751

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