Abstract: Recently, advanced geotechnical engineering problems
related to soil movement, particle loss, and modeling of local failure
(i.e. discontinua) as well as modeling the in-contact structures (i.e.
continua) are of the great interest among researchers. The aim of this
research is to meet the requirements with respect to the modeling
of the above-mentioned two different domains simultaneously. To
this end, a coupled numerical method is introduced based on
Discrete Element Method (DEM) and eXtended-Finite Element
Method (X-FEM). In the coupled procedure, DEM is employed to
capture the interactions and relative movements of soil particles as
discontinua, while X-FEM is utilized to model in-contact structures as
continua, which may consist of different types of discontinuities. For
verification purposes, the new coupled approach is utilized to examine
benchmark problems including different contacts between/within
continua and discontinua. Results are validated by comparison with
those of existing analytical and numerical solutions. This study
proves that extended-finite-discrete element method can be used
to robustly analyze not only contact problems, but also other
types of discontinuities in continua such as (i) crack formations
and propagations, (ii) voids and bimaterial interfaces, and (iii)
combination of previous cases. In essence, the proposed method
can be used vastly in advanced soil-structure interaction problems to
investigate the micro and macro behaviour of the surrounding soil and
the response of the embedded structure that contains discontinuities.
Abstract: This paper presents the data of a series of two-dimensional Discrete Element Method (DEM) simulations of a large-diameter rigid monopile subjected to cyclic loading under a high gravitational force. At present, monopile foundations are widely used to support the tall and heavy wind turbines, which are also subjected to significant from wind and wave actions. A safe design must address issues such as rotations and changes in soil stiffness subject to these loadings conditions. Design guidance on the issue is limited, so are the availability of laboratory and field test data. The interpretation of these results in sand, such as the relation between loading and displacement, relies mainly on empirical correlations to pile properties. Regarding numerical models, most data from Finite Element Method (FEM) can be found. They are not comprehensive, and most of the FEM results are sensitive to input parameters. The micro scale behaviour could change the mechanism of the soil-structure interaction. A DEM model was used in this paper to study the cyclic lateral loads behaviour. A non-dimensional framework is presented and applied to interpret the simulation results. The DEM data compares well with various set of published experimental centrifuge model test data in terms of lateral deflection. The accumulated permanent pile lateral displacements induced by the cyclic lateral loads were found to be dependent on the characteristics of the applied cyclic load, such as the extent of the loading magnitudes and directions.
Abstract: The objective of this paper is to evaluate the effects of
soil-structure interaction (SSI) on the modal characteristics and on
the dynamic response of current structures. The objective is on the
overall behaviour of a real structure of five storeys reinforced
concrete (R/C) building typically encountered in Algeria. Sensitivity
studies are undertaken in order to study the effects of frequency
content of the input motion, frequency of the soil-structure system,
rigidity and depth of the soil layer on the dynamic response of such
structures. This investigation indicated that the rigidity of the soil
layer is the predominant factor in soil-structure interaction and its
increases would definitely reduce the deformation in the R/C
structure. On the other hand, increasing the period of the underlying
soil will cause an increase in the lateral displacements at story levels
and create irregularity in the distribution of story shears. Possible
resonance between the frequency content of the input motion and soil
could also play an important role in increasing the structural
response.
Abstract: A reliability-based methodology which uses structural demand hazard curves to consider the increment of the ductility demands of structures with tilting is proposed. The approach considers the effect of two orthogonal components of the ground motions as well as the influence of soil-structure interaction. The approach involves the calculation of ductility demand hazard curves for symmetric systems and, alternatively, for systems with different degrees of asymmetry. To get this objective, demand hazard curves corresponding to different global ductility demands of the systems are calculated. Next, Uniform Exceedance Rate Spectra (UERS) are developed for a specific mean annual rate of exceedance value. Ratios between UERS corresponding to asymmetric and to symmetric systems located in soft soil of the valley of Mexico are obtained. Results indicate that the ductility demands corresponding to tilted structures may be several times higher than those corresponding to symmetric structures, depending on several factors such as tilting angle and vibration period of structure and soil.
Abstract: Over the years, it has been extensively established that
the practice of assuming a structure being fixed at base, leads to gross
errors in evaluation of its overall response due to dynamic loadings
and overestimations in design. The extent of these errors depends on
a number of variables; soil type being one of the major factor. This
paper studies the effect of Soil Structure Interaction (SSI) on multistorey
buildings with varying under-laying soil types after proper
validation of the effect of SSI. Analysis for soft, stiff and very stiff
base soils has been carried out, using a powerful Finite Element
Method (FEM) software package ANSYS v14.5. Results lead to
some very important conclusions regarding time period, deflection
and acceleration responses.