1,721,046 research outputs found
Deformabilità non-drenata statica e dinamica di un'argilla fortemente sovraconsolidata.
No full textForce-based pseudo-static methods versus displacement-based methods for slope stability analysis.
No full textContribution to discussion session 2A (Modelling of shear deformation of geomaterials - Identification of material properties).
No full textThe role of soil constitutive modelling on the assessment of seismic performance of caisson foundations
No full textIn this paper, the influence of inelastic soil behaviour on the seismic performance of bridge piers supported by caisson foundations is assessed. The results of an extensive parametric study, performed assuming a linear elastic and an elastic-plastic soil behaviour, are compared, showing the strong influence of the inelastic soil response. The geometrical properties of caissons and piers are varied; the systems are subjected to seismic records capable of mobilising the shear strength of the soil. 3D dynamic analyses are performed in the time domain and in terms of effective stresses but assuming undrained conditions. The role of soil constitutive modelling is assessed by comparing the deck drift and the forces transmitted by the superstructure to the caissons, both computed under the assumption of linear elastic and elastic-plastic soil behaviour. The results clearly indicate for which systems the linear elastic assumption is satisfactory and when, conversely, soil non-linearities should be considered
Panel Intervention, Discussion Session 4. Displacement and Soil–Structure Interaction: Earth Retaining Structures and Deep Excavations
No full textSeismic performance of two classes of earth dams
No full textIn the last decades, Italy has experienced several strong earthquakes, triggering the attention on the high seismic risk associated with the potential instability of large existing earth dams. Under intense seismic events, dam response depends on various factors including the geometry and the type of water retention scheme. This paper explores the influence of these factors, comparing the seismic performance of two idealized earth dams: a homogeneous dam and a zoned dam. The simplified models adopted in the analyses are representative of these two classes of earth dams, often adopted in the sixties to design various dams located in southern Italy. The idealized models, here examined in detail, have comparable heights and foundation soil conditions, differing in terms of water retention scheme. The seismic response of the dams was evaluated through time-domain nonlinear dynamic analyses in which the same input ground motion, represented by real-time histories, was applied at the base of the models. It is shown that for highly inelastic systems, such as those at hand, duration of input motion should be accounted for in addition to compatibility criteria with a design elastic response spectrum. Also, different slopes of dam flanks, shear strength mobilization at the end of dam construction and high stiffness contrast at the shells-core contacts are shown to result in different deformation patterns at the end of earthquake loading. Some peculiarities in the behavior of these classes of earth dams are highlighted in the paper, providing a guidance for the rational assessment of their seismic performance
A simplified procedure for the evaluation of the seismic performance of bridge piers on caisson foundations
Full text linkIn this paper, a simplified procedure for the evaluation of the seismic performance of bridge piers founded on caissons subjected to strong ground motions is outlined. To this end, the up-per-bound semi-empirical relationships proposed in [1] are considered for the estimation of the seismic performance, expressed in terms of the maximum and permanent values of the deck drift ratio attained during and at the end of the seismic event. These drifts were related to the period ratio Teq/T0 between the fundamental periods of the deck-pier-caisson-soil sys-tem and of the soil column in free-field conditions. The deck drift and the period ratios were extracted from the results of an extensive parametric study, where 14 different systems were subjected to 6 real high-intensity seismic records. In the parametric study, 3D dynamic anal-yses were performed with the Finite Element Method in the time domain, in terms of effective stresses but assuming undrained conditions and adopting an elastic-plastic constitutive model to reproduce the irreversible soil behaviour under cyclic loading. As 3D dynamic numerical analyses are not expected to become an every-day design tool, the period ratios Teq/T0 are evaluated through empirical and analytical relationships available in the literature as well and then compared with the ratios obtained from the parametric study, to assess the possibil-ity of using simplified relationships while still getting a reliable estimate of the deck drift ra-tio. It is shown that these relationships can be profitably adopted provided that a fair estimate of the equivalent shear wave velocity, depending on the intensity of the seismic inputs, is used
Some aspects of the dynamic performance of two classes of earth dams
No full textPotential instability of large existing earth dams is a major source of seismic
vulnerability of Italy. In fact, most of them were designed before the adoption of modern
building codes, without accounting for seismic loads explicitly. Hence, there is an urgent
necessity to investigate the response of most existing earth dams to severe earthquake loading.
This paper compares some aspects of the seismic performance of a homogeneous and a zoned earth dam. The numerical analyses were carried out using two models which were calibrated on the data available from two existing and well documented earth dams. The geometry of the dams was converted into two simplified schemes characterised by the same height and mechanical properties of the foundation soil but by different schemes of water retention. The seismic
response of the dams was evaluated through time-domain dynamic analyses in which the same input ground motion, represented by real-time histories, was applied at the base of the models
Static and dynamic measurements of undrained stiffness on natural overconsolidated clays.
No full text- …
