Numerical Analysis of Free Field under Horizontal Seismic Excitations

2012 ◽  
Vol 166-169 ◽  
pp. 2005-2008
Author(s):  
Shou Long Chen ◽  
Chun Yi Cui ◽  
Zhong Tao Wang
Keyword(s):  
Seismic Waves ◽  
Soil Depth ◽  
Soft Soil ◽  
Free Field ◽  
Low Frequency ◽  
Seismic Excitations ◽  
Finite Element Program ◽  
Element Program ◽  
Frequency Components ◽  
Free Bank

Based on Newmark-β gradual integration method and elastic-plastic mechanical theory, numerical analyses of the effects of soft soil depth and thickness on the characteristics of seismic response of free bank field with soft soil layers are conducted by using finite element program Midas/GTS. The numerical results show that the high frequency components of seismic excitations can be filtered and the low frequency components are amplified correspondingly when seismic waves are transmitted through the free bank field from the bedrock.

Finite Element Analysis of Bridge-Foundation Interaction System under Horizontal Seismic Excitation

2014 ◽  
Vol 490-491 ◽  
pp. 691-694
Author(s):  
Shou Long Chen ◽  
Chun Yi Cui ◽  
Yan Sun
Keyword(s):  
Finite Element ◽  
Seismic Waves ◽  
Soil Depth ◽  
Soft Soil ◽  
Soil Layer ◽  
Element Analysis ◽  
Interaction System ◽  
Frequency Components ◽  
Bridge Foundation ◽  
Pile Length

Based on Newmark-β gradual integration method and elastic-plastic mechanical theory, numeriacl analyses of effects of soft soil depth and thickness and pile length on the characteristics of horizontal seismic response of bridge-foundation interaction system with soft layers conducted by using finite element program Midas/GTS. The numerical results show that: (1) The high frequency components of seismic excitations can be filtered and the low frequency components are amplified correspondingly when seismic waves are transmitted through soft soil layer, and thicker and lower soft soil layer can amplified this effects; (2)The extremum force of abutment shows decreases first then increases with depth decreasing, and displacement of abutment top and bottom has the same law with seismic waves, and the thicker and lower soft soil layer or shorter piles can aggravate abutment force and deformation; (3)Shear extremal stress shows decrease from top to bottom and the thicker and lower soft soil layer or shorter piles are adverse on piles; (4)Moment extremal expresses first increase then decrease with pile length and the lower and thicker soft soil layer or shorter piles can enlarged piles moment.

Analysis of Raft Foundation with EPS Geofoam for Earthquake Resistant

2014 ◽  
Vol 695 ◽  
pp. 613-616
Author(s):  
Mohd Faiz Mohammad Zaki ◽  
Mohammad Fadzli Ramli ◽  
Afizah Ayob ◽  
Mohd Taftazani Ahmad
Keyword(s):  
Structural Engineering ◽  
Soft Soil ◽  
Simulation Models ◽  
Soil Mass ◽  
Dynamic Force ◽  
Finite Element Program ◽  
Eps Geofoam ◽  
Raft Foundation ◽  
Element Program ◽  
Innovative Material

It is becoming a great challenge for civil engineers to design a foundation which able to minimize the effect of an earthquake. A major earthquake produces a strong ground motion in the subsoil and surface structures supported on the soil mass will be induced to move and absorb the dynamic forces. Seismic retrofit of existing foundations is an alternative. However, the modification of this existing foundation toward earthquake resistances raises issues which are far from being totally resolved. Innovative material such as EPS is widely accepted in structural engineering due to its characteristic to absorb the dynamic force effectively. This EPS material demonstrated the practicality and has been applied for geotechnical engineering for various reasons. Based on this, a research which is related to the application of EPS in mitigating the earthquake forces, particularly for raft foundations was conducted properly in this research. The various types and thickness of EPS located beneath the raft foundation and over the soft soil are studied. A finite element program is utilized to develop the computer simulation models. Based on the results, Expended Polystyrene (EPS) Geofoam, placed beneath the raft foundation is able to produces the minimum settlements when subjected to earthquake loading rather than raft foundation modeled without EPS and increasing the density of EPS will simultaneously decrease the settlement of a foundation.

Evaluation of the effect of depth to bedrock on seismic amplification phenomena

2020 ◽  
Author(s):  
gaetano falcone ◽  
giuseppe naso ◽  
stefania fabozzi ◽  
federico mori ◽  
massimiliano moscatelli ◽  
...  
Keyword(s):  
Seismic Waves ◽  
Site Response ◽  
Soft Soil ◽  
Free Field ◽  
Response Spectra ◽  
Maximum Depth ◽  
Response Analysis ◽  
Local Conditions ◽  
Seismic Amplification ◽  
Bedrock Depth

<p>When an earthquake occurs, the propagation of the seismic waves is conditioned by local conditions, e.g., depth to seismic bedrock and impedance ratio between soft soil and seismic bedrock. Bearing in mind that the maximum depth of site prospections generally does not extend up to seismic bedrock depth, a parametric study was carried out with reference to ideal case studies in order to investigate the effect on local seismic amplification of the depth to bedrock.</p><p>The results are presented in terms of charts of amplification factors (i.e., ratio of integral quantities referred to free-field and reference response spectra) and minimum depth to investigate vs building type. These charts will allow defining the thickness of the cover deposit that should be characterised in terms of geophysical and geotechnical parameters in order to perform seismic site response analysis according to a precautionary approach, in areas where depth to seismic bedrock is higher than conventional maximum depth of site surveys.</p>

Analysis for the 3-Dimensional Time History Response of a Base-Isolated Building Structure

2011 ◽  
Vol 368-373 ◽  
pp. 1961-1964
Author(s):  
Jin Xia Kang
Keyword(s):  
Composite Structures ◽  
Seismic Waves ◽  
Three Dimensional ◽  
Time History ◽  
Economic Benefits ◽  
Seismic Structure ◽  
Finite Element Program ◽  
Concrete Frame ◽  
Element Program ◽  
Lateral Displacements

In this paper, the models of traditional anti-seismic and base-isolated masonry and concrete frame composite structures were created by the three-dimensional finite element program and their time history responses were analyzed under the actions of different seismic waves. The results show that whether they were under the action of frequently occurred earthquake or rarely occurred earthquake, the story shears of base-isolated structure are far less than those of traditional anti-seismic structure; the lateral displacements of the former are nearly translational, while those of the latter are approximately parabolic; and the fundamental period of the former is much longer than the counterpart. In conclusion, the seismic fortification intensity of base-isolated structure is one or two degree less than that of traditional anti-seismic structure, and adopting the base-isolated structure will protect the life-safety and property of people and achieve good economic benefits as well.

The effect of Yucca Fault on seismic wave propagation

1971 ◽  
Vol 61 (3) ◽  
pp. 697-706 ◽  
Author(s):  
Walter W. Hays ◽  
John R. Murphy
Keyword(s):  
Wave Propagation ◽  
Seismic Wave ◽  
Seismic Waves ◽  
Low Frequency ◽  
Test Site ◽  
Seismic Wave Propagation ◽  
Nevada Test Site ◽  
Basement Rocks ◽  
Geological Discontinuity ◽  
Frequency Components

abstract Yucca Fault is a major structural feature of Yucca Flat, a well-known geological province of the Nevada Test Site (NTS). The trace of the Fault extends north-south over a distance of about 32 km. The fault plane is nearly vertical and offsets Quaternary alluvium, Tertiary volcanic tuffs and pre-Cenozoic basement rocks (quartzites, shales and dolomites) with relative down displacement of several hundred feet on the east side of the fault. Data recorded from the CUP underground nuclear detonation in Yucca Flat typify the effect of the fault on near-zone (i.e., inside 10 km) seismic wave propagation. The effect of the fault is frequency dependent. It affects the frequency components (3.0, 5.0, 10.0 Hz) of the seismic waves which have characteristic wavelengths in the order of the geological discontinuity. Little or no effect is observed for low-frequency components (0.5, 1.0 Hz) which have wave-lengths exceeding the dimensions of the geological discontinuity. The effect of the fault does not represent a safety problem.

scholarly journals Influence of Tunneling in Cohesionless Soil for Different Tunnel Geometry and Volume Loss under Greenfield Condition

2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Raja Kanagaraju ◽  
Premalatha Krishnamurthy
Keyword(s):  
Free Field ◽  
Deformation Modulus ◽  
Cohesionless Soil ◽  
Support Pressure ◽  
Measuring Instruments ◽  
Volume Loss ◽  
Tunnel Face ◽  
Finite Element Program ◽  
Element Program ◽  
Tunnel Size

This paper presents the numerical analysis of settlement to profile the vulnerable zone or influence zone due to tunneling activities in cohesionless deposits for free field or Greenfield conditions. The analysis considers the factors like saturated density (γsat), unsaturated density (γunsat), angle of shearing resistance (φ), deformation modulus (ES), volume loss (VL), and the support pressure of the shield head at the tunnel face. The obtained results using a finite element program (FEM) PLAXIS 3D are compared with measured and predicted surface settlement using field measuring instruments, and analytical and empirical solution show a reasonable agreement and are found to be conservative. From literature, for Greenfield condition the ground settlement equal to 10 mm is taken as the minimum value to map the influencing zone considering the fact that the structure which lies beyond this zone would undergo negligible settlement. Settlement trough and 10 mm settlement contour characteristics are presented for different tunnel sizes placed at the same depth and the same tunnel size placed at different depths, respectively. Various influencing zones are arrived for the sandy grounds of different denseness based on the parametrical studies involving parameters such as tunnel size “D,” tunnel axis depth “z,” and volume loss “VL.”

The value of very low frequencies and far offsets for seismic data in the Permian Basin: Case study on a new dense survey from the Central Basin Platform

2022 ◽  
Vol 41 (1) ◽  
pp. 34-39
Author(s):  
Vincent Durussel ◽  
Dongren Bai ◽  
Amin Baharvand Ahmadi ◽  
Scott Downie ◽  
Keith Millis
Keyword(s):  
Seismic Data ◽  
Seismic Waves ◽  
Waveform Inversion ◽  
Low Frequency ◽  
Central Basin ◽  
Permian Basin ◽  
Depth Of Penetration ◽  
Low Frequencies ◽  
Frequency Components ◽  
Band Limited

The depth of penetration and multidimensional characteristics of seismic waves make them an essential tool for subsurface exploration. However, their band-limited nature can make it difficult to integrate them with other types of ground measurements. Consequently, far offsets and very low-frequency components are key factors in maximizing the information jointly inverted from all recorded data. This explains why extending seismic bandwidth and available offsets has become a major industry focus. Although this requirement generally increases the complexity of acquisition and has an impact on its cost, improvements have been clearly and widely demonstrated on marine data. Onshore seismic data have generally followed the same trend but face different challenges, making it more difficult to maximize the benefits, especially for full-waveform inversion (FWI). This paper describes a new dense survey acquired in 2020 in the Permian Basin and aims to objectively assess the quality and benefits brought by a richer low end of the spectrum and far offsets. For this purpose, we considered several aspects, from acquisition design and field data to FWI imaging and quantitative interpretation.

The Soft Soil Foundation Consolidation Numerical Simulation Based on the Model of Modified Cam-Clay

2014 ◽  
Vol 580-583 ◽  
pp. 3223-3226 ◽  
Author(s):  
Xiao Jie Gu ◽  
Tai Quan Zhou ◽  
Song Cheng
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Soft Soil ◽  
Analysis Model ◽  
Element Analysis ◽  
Consolidation Process ◽  
Full Account ◽  
Finite Element Program ◽  
Modified Cam Clay ◽  
Element Program

The clay layer finite element analysis model , which is established by using finite element program to simulate the embankment filling , takes the intercoupling between water and clay in drainage consolidation process into full account. The use of the effective stress principle consider the characteristics of clay such as nonlinerity , large deformation and so on ,carry out the plane strain finite element analysis on the clay and solve a series of engineering problems.

Landslide mobility analysis for design of multiple debris-resisting barriers

2015 ◽  
Vol 52 (9) ◽  
pp. 1345-1359 ◽  
Author(s):  
J.S.H. Kwan ◽  
R.C.H. Koo ◽  
C.W.W. Ng
Keyword(s):  
Debris Flows ◽  
Free Field ◽  
Three Dimensional ◽  
Mobility Model ◽  
Mobility Analysis ◽  
Finite Element Program ◽  
Laboratory Test Results ◽  
Dimensional Finite Element ◽  
Element Program ◽  
Three Dimensional Finite Element

Multiple debris-resisting barriers have been commonly used worldwide to mitigate debris flows in drainage lines. However, a well-developed methodology to assess the mobility of debris flows with consideration of the obstruction of the barriers does not exist. A free-field debris-flow condition that omits the presence of multiple debris-resisting barriers is commonly considered in design, although the effects of the barriers could be critical in determining the dynamics of the landslide debris including debris velocity and debris thickness. This paper proposes a staged debris mobility analysis that accounts for the effects of multiple debris-resisting barriers. The staged analysis adopts solutions of a depth-averaged debris mobility model. The input parameters of the analysis have been established from field data and laboratory test results. Rigorous numerical simulations of debris flows intercepted by multiple debris-resisting barriers have also been undertaken using the three-dimensional finite element program LS-DYNA to provide results for benchmarking the output of the staged analysis.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

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