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Evaluation of Earthquake Waves Amplification Due to Trapezoidal Hill by 1D and 2D Time Domain Analysis (In Persian)

Authors:
Arash Shareghi at Urmia University
Arash Shareghi
Masoud Amelsakhi at Qom University Of Technology
Masoud Amelsakhi
Abdollah Sohrabi-Bidar at University of Tehran
Abdollah Sohrabi-Bidar
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Abstract and Figures

Evaluation of strong ground motion up beneath the construction is important in both geotechnical engineering (site effect) and earthquake engineering aspects (analysis of earth behavior). The common methods of microzonation in geotechnical engineering is based on one dimensional dynamic analysis, in which ground surface is supposed to be horizontal, however in many cases, because of variety of topography conditions, recorded responses are different on the top of topography and their corners. In this study, FLAC 2D software as finite difference software, is used to analysis the trapezoidal hill with different shape ratios. These topography models are analyzed by far field earthquake records, and their dimensionless amplification ratios are compared with obtained results of one dimensional analysis. Assessment of these two analysis methods in some points on the topography and around it, demonstrated considerable differences that evident necessity of two dimensional analysis in earthquake geotechnical engineering.
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 arash_shareghi@yahoo.com
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
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SV, P



    SH


Downloaded from jeg.khu.ac.ir at 11:36 IRST on Monday December 26th 2016

SV  

. Bouchon . Geli . Sanchez-Sesma . Pedersen . Moczo
        

SV, P 

SV

SV


  

    
       








       




FLAC
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



. Bouckovalas . Gazetas . Adames . Chang-Guk
. Gyeongju . Explicit
      
 
:m/sVs=
ν=
kg/mρ=SV
/R=λ


     


FLACR=λ/R=
SV
    

(X) (L)


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

M=kmD>
m/sPGA=

m/sVs>. Wong

PGD
(cm)
PGV
(cm/s)
PGA
(m/s2)
Distance
(km)
Station/
Component
Record
ID
NO.




Amboy
 P




So. San Francisco,
Sierra Pt. 
 P




Lake Hughes #9
 P




LA - Wonderland
Ave
 P




Mt Wilson - CIT
SeisSta
 P




Leona Valley #3 
 P




San Gabriel - E.
Grand Ave. 
 P




Anza - Red
Mountain 
 P




Silent Valley -
Poppet F
 P




Lake Hughes #9
 P





Mt Wilson - CIT
SeisSta 
 P





SAHOP Casa
Flores 
 P



kg/mρ=MPaE=
ν=
   

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




ξ=

ANSYS 
ANSYS 

ANSYS






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



  
. Lysmer . Kuhlemeyer
Δlλ


 

        
         

   
DFLAC



A          
A
ADFLAC
A


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
DFLAC
. Free Field

          
   PGAresponse
      
   PGAIncident
       




.


           



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     
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           
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NEHRPIBC
  ECAFPS    
AFPS
EC 


AFPS 
ECEC

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      


AFPS    
EC   شهوژپ
AFPS


 
     


            

             



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
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AFPS EC
D D, X/L=





            
 
  

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
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ResearchGate has not been able to resolve any citations for this publication.
Finite element method accuracy for wave propagation problems [J]
Article
  • May 1973
The purpose of this paper is presentation of the results of a study concerning the accuracy of displacements caused by a single, harmonic, one-dimensional elastic wave propagating through a finite element mesh. Results are presented for the steady-state response of a finite model of the semi-infinite elastic constrained rod; both the homogeneous and two material cases were analyzed.
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Strong ground motion and site effects
Book
  • Jan 1997
The effects due to local topography and geology on strong ground motion are reviewed. These can modify the ground shaking to a large extent and are relevant in the seismic design of structures, that are expected to perform satisfactorily when subjected to earthquakes. Although the coverage of these issues is far from being exhaustive, we hope to stimulate interest in this problem. Several relevant issues are discussed and references are given so that it is possible to pursue independent study. The potential for damage of moderate near-field earthquakes is at least as large as that from very large far-field seismic events. The 1995 Kobe and the 1985 Michoacan earthquakes, respectively, are, perhaps the most dramatic examples of these two kinds of events. They show how important site effects can be.
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Three-dimensional scattering by two-dimensional topographies
Article
  • Jan 1994
Three-dimensional seismic responses of two-dimensional topographies are studied by means of the indirect boundary element method (IBEM). The IBEM yields, in the presented form, very accurate results and has the advantage of low computation cost. In IBEM, diffracted waves are constructed in terms of single-layer boundary sources. The appropriate Green's functions used are those of a harmonic point force moving along the axis of the topography in a full space. Obtained results are compared against those published by other authors. -from Authors
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Effect of topography on surface motion
Article
  • Apr 1973
The effect of topography on surface motion is investigated in the cases of incident SH, P and SV waves. Several types of topography ranging from a ridge to a valley are used. Different incidence angles are considered for a wavelength interval extending from 2h to 20h, where h is the vertical dimension of the anomaly. The computation is made by using a single frequency method developed by Aki and Larner and by synthesizing the results in order to get a solution in the time domain. A method of correction taking into account the residual stress is added. The surface displacement appears to be very much influenced by surface irregularities. In the case of a ridge, a zone of amplification takes place near the top, whereas, for a depression, a zone of attenuation occurs near the bottom. An application to the Pacoima Dam accelerograph site suggests that the high accelerations recorded there during the San Fernando earthquake could have been amplified between 30 and 50 per cent by the uneven topography.
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Diffraction of P, SV and Rayleigh waves by topographic features: a boundary integral formulation
Article
  • Jan 1991
A method is presented to compute the diffraction of P, SV, and Rayleigh waves by an irregular topographic feature in an elastic half-space. It is based on an integral representation of the diffracted elastic fields in terms of single-layer boundary sources that is derived from Somigliana's identity. Introduction of boundary conditions leads to a Fredholm integral equation of the second kind for boundary sources. A discretization scheme based on the numerical and analytical integration of exact Green's functions for displacements and tractions is employed. Calculations are performed in the frequency domain and synthetic seismograms are obtained using the fast Fourier transform. In order to give perspective on the range of effects caused by topographic anomalies, various examples that cover extreme cases are presented. -from Authors
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Numerical evaluation of slope topography effects on seismic ground motion
Article
  • Aug 2005
  • SOIL DYN EARTHQ ENG
This paper presents results of numerical analyses for the seismic response of step-like ground slopes in uniform visco-elastic soil, under vertically propagating SV seismic waves. The aim of the analyses is to explore the effects of slope geometry, predominant excitation frequency and duration, as well as of the dynamic soil properties on seismic ground motion in a parametric manner, and provide qualitative as well as quantitative insight to the phenomenon. Among the main conclusions of this study is that this kind of topography may lead to intense amplification or de-amplification variability at neighboring (within a few tens of meters) points behind the crest of the slope, especially for high frequency excitations. Nevertheless, a general trend of amplification near the crest and de-amplification near the toe of the slope seems to hold for the horizontal motion. As a result of these two findings, it becomes evident that reliable field evidence of slope topography aggravation is extremely difficult to establish. Furthermore, this study highlights the generation of a parasitic vertical component of motion in the vicinity of the slope, due to wave reflections at the slope surface, that under certain preconditions may become as large as the horizontal. Criteria are established for deciding on the importance of topography effects, while approximate relations are provided for the preliminary evaluation of the topographic aggravation of seismic ground motion and the width of the affected zone behind the crest.
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Effect of surface topography on the diffraction of P, SV, and Rayleigh waves
Article
  • Jan 1982
A generalized inversed method for boundary conditions is adapted for boundary value problems in elastic wave propagation. Two exact solutions; the first for SH-wave scattering by a semi-cylindrical canyon, and the second for P-wave scattering by a cylindrical cavity are used to test the accuracy of this approximate method. Subsequent applications of this numerical method involve problems not solvable by exact methods, these include the diffraction of P, SV, or Rayleigh waves by irregular surface topographies.
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Simplified Frequency Content Estimates of Earthquake Ground Motions
Article
  • Feb 1998
It is often useful in earthquake engineering practice to characterize the frequency content of an earthquake ground motion with a single parameter. Three simplified frequency content parameters are examined: mean period (T-m), predominant period (T-p), and the smoothed spectral predominant period (T-o). These frequency content parameters are calculated for 306 strong motion recordings from 20 earthquakes in active plate-margin regions. These data are used to develop a model that describes the magnitude, distance, and site dependence of these frequency content parameters, Nonlinear regression analyses are performed to evaluate model coefficients and standard error terms. The results indicate that the traditional T-p parameter has the largest uncertainty in its prediction, and that previous relationships proposed to predict T-p are inconsistent with the current data set. Moreover, T-m is judged to be the best simplified frequency content characterization parameter, and it can be reliably estimated.
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Evaluation of seismic ground motion induced by topographic irregularity
Article
  • Feb 2007
  • SOIL DYN EARTHQ ENG
Results of an extensive numerical study on the 2D scattering of seismic waves by local topography are presented. The investigation has been conducted using the direct boundary element method. Several types of topography (slopes, canyons and ridges) are considered. The influences of some key parameters, such as exciting frequency and geometry of the irregular feature, on surface ground motion are studied in detail. It is found that local topographic conditions play an important role in the modification of seismic ground motion at the irregular feature itself and its neighbourhood. The present results can be considered to be useful from the viewpoint of earthquake engineering and seismology.
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