Dynamic Characterization and Site Response Studies for an Offshore Site Based on Detailed Geotechnical Tests

2015 ◽  
Vol 6 (1) ◽  
pp. 50-80
Author(s):  
T. G. Sitharam ◽  
Naveen James ◽  
Monalisha Nayak
Keyword(s):  
Ground Motion ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Site Characterization ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Undisturbed Soil ◽  
Design Response Spectrum ◽  
Laboratory Test Results

The uniqueness of this paper is large amount of field test data and in addition laboratory test results on undisturbed soil samples, has been analyzed to capture the effect of local site condition and material properties of overlying soil on seismic ground motion characteristics. This study involves the seismic site characterization and ground response analysis of an offshore site in Western Yemen. From the results of field and laboratory tests, dynamic properties such as shear modulus and damping ratio for a very low to high strain levels was determined and site characterization was also carried out. Using seismic cone penetration test (SCPT) data a new correlation has been developed to predict the shear wave velocity. Synthetic ground motion was generated using Boore's stochastic modeling technique for ground response analysis and peak ground acceleration (PGA) was evaluated and presented in the paper. This paper also presents a site specific design response spectrum based on Eurocode, corresponding to 475 and 2500 year return period.

scholarly journals Evaluation of Dynamic Properties and Ground-Response Analysis of Soil Reinforced with Cement and Biopolymer

2020 ◽  
Vol 20 (5) ◽  
pp. 291-296
Author(s):  
Seongnoh Ahn ◽  
Kwangkuk Ahn ◽  
Changho Lee ◽  
Jun-Dae Lee ◽  
Jongwon Jung
Keyword(s):  
Seismic Performance ◽  
Dynamic Properties ◽  
Ground Improvement ◽  
Damping Ratio ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Ground Acceleration ◽  
Design Earthquake ◽  
Earthquake Damages

In Korea, earthquakes have continued to occur even after the occurrence of Gyeongju and Pohang earthquakes of 2016 and 2017, respectively, raising awareness of earthquakes. Because earthquakes cause damage to not only structures but also humans, it is essential to improve the seismic performance and design earthquake-resistant structures to minimize earthquake damages. If the seismic performance of a structure is improved through ground improvement and reinforcement, ground response analysis should be performed considering the dynamic properties of the site of the structure. In addition, cement has been widely used as a material for ground improvement, but recently, ground improvement methods in which biopolymers are utilized for ecofriendly construction have been investigated extensively. However, studies on the changes in the dynamic properties of ground improved using biopolymers, and the ground-response analysis has not been investigated in detail. In this study, resonant column tests were performed using samples mixed with cement and sodium alginate to evaluate the effects o f ground improvement using a biopolymer. In addition, the dynamic properties of the improved samples were adopted in performing the ground response analysis, which demonstrated confirmed the ground stability after ground improvement. From the results, the ground dynamic properties, shear modulus, and damping ratio were influenced when the biopolymer and cement were mixed with the soil. Furthermore, the ground response analysis confirmed that the maximum ground acceleration on the surface decreased.

Importance of Site-Specific Dynamic Soil Properties for Seismic Ground Response Studies

2018 ◽  
Vol 9 (1) ◽  
pp. 78-98 ◽  
Author(s):  
Shiv Shankar Kumar ◽  
Arindam Dey ◽  
A. Murali Krishna
Keyword(s):  
Soil Properties ◽  
Dynamic Properties ◽  
Damping Ratio ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Site Specific ◽  
Dynamic Soil Properties ◽  
Acceleration Time Histories ◽  
Seismic Ground Response

This article highlights the implication of site-specific properties on seismic ground response studies. One-dimensional equivalent linear ground response analysis was carried out using site-specific dynamic properties of locally available soils of Guwahati city, and the results are compared with those obtained using existing strain-dependent dynamic properties. Acceleration time histories from three strong motions were used. It was observed that an input motion having a higher peak bedrock acceleration, utilizing experimentally obtained dynamic soil properties, exhibits 38% and 24% lower peak ground acceleration and peak spectral acceleration, respectively, in comparison to the results obtained using standard VD-SI soil models. The amplification characteristics of the strong motions are observed to be significantly influenced by the degradation of damping ratio beyond 1% shear strain. The results highlight the necessity of conducting GRA of any region considering its regional dynamic soil properties to obtain more realistic outcomes.

Seismic Ground Response Analysis of Some Typical Sites of Guwahati City

2013 ◽  
Vol 4 (1) ◽  
pp. 83-101 ◽  
Author(s):  
Shiv Shankar Kumar ◽  
A. Murali Krishna
Keyword(s):  
Ground Motion ◽  
Amplitude Ratio ◽  
Response Spectrum ◽  
Strong Motion ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Ground Acceleration ◽  
Surface Level ◽  
Guwahati City

In this study, one dimensional equivalent–linear ground response analyses were performed for some typical sites in the Guwahati city, India. Six bore locations covering about 250 km2 area of the city were considered for the analyses. As the strong motion significantly influences the ground response, seven different recorded ground motions, varying in magnitude (6.1 to 8.1) and other ground motion parameters, were adopted. Seismic site analyses were carried out for all layers of borelogs using all the seven earthquakes. Results are presented in terms of surface acceleration histories, strain and shear stress ratio variation, response spectrum, Fourier amplitude ratio versus frequency. The results indicate that accelerations were amplified the most at the surface level. The range of peak ground acceleration (PGA) values obtained at the ground surface is about 0.2 g to 0.79 for a range of PGA considered at bedrock level (rigid half space at bottom of borelog) of 0.1 g to 0.34 g. The Fourier amplifications of ground motion at surface are in the range of 4.14 – 8.99 for a frequency band of 1.75 Hz to 3.13 Hz. The maximum spectral acceleration at six locations varies in the range of 1.0 g – 4.71 g for all the seven earthquakes. The study clearly demonstrated the role for site effect and the type of ground motion on the ground response. For a given earthquake motion, amplification factors at surface level change by almost about 20% to 70% depending on local site conditions.

A Site Specific Study on Evaluation of Design Ground Motion Parameters

2010 ◽  
Vol 1 (1) ◽  
pp. 1-24 ◽  
Author(s):  
A. Boominathan ◽  
S. Krishna Kumar
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Site Specific ◽  
Specific Analysis ◽  
A Site

Design ground motions are usually developed by one of the two approaches: site-specific analyses or from provisions of building codes. Although contemporary codes do consider approximately the site effects, they provide more conservative estimates. Hence it is preferred to carry out site specific analysis which involves both the seismic hazard analysis and ground response analysis. This article presents a site specific analysis for a seismically vulnerable site near Ahmedabad, Gujarat. The seismic hazard analysis was carried out by DSHA approach considering seismicity and seismotectonics within 250km radius. The site is predominantly characterized by deep stiff sandy clay deposits. Extensive shear wave velocity measurement by cross hole test is used for site classification and ground response analysis. The ground response analysis was carried out by equivalent linear approach using SHAKE2000. It is found that the deep stiff soil site considered is found to amplify the ground motion. The site specific response spectra obtained from RRS analysis is compared with the codal provision which reveals high spectral acceleration in site specific spectra for mid period range.

Challenges in the definition of input motions for forensic ground-response analysis in the near-source region

2021 ◽  
pp. 875529302110013
Author(s):  
Nikolaos Ntritsos ◽  
Misko Cubrinovski ◽  
Brendon A Bradley
Keyword(s):  
Ground Motion ◽  
Ground Motions ◽  
Source Region ◽  
Strong Motion ◽  
Target Site ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Recording Station

This article scrutinizes the determination of input motions for forensic ground-response analysis in the near-source region, based on recorded surface ground motions at strong-motion station sites, from the same event. The first part of the article draws upon observed ground motions from the 22 February 2011 6.2 Mw Christchurch earthquake to discuss key challenges of the problem associated with the strong spatial variation of ground motion in the near-source region. Effects from the complexity of the rupture, propagation of seismic waves through complex geological structures, and site characteristics are explored. It is argued that, because of the strongly varying source-path “signature” on near-source ground motions, “reference” input motions for ground-response analysis must be specific to, and have similar signature characteristics (be “compatible”) with, the target site which is subject to the analysis. The second part of the article presents a four-step procedure for the derivation of site-specific input motions involving (1) determination of the reference layer where the input motion is to be applied in the analysis, (2) record selection considering the appropriateness of the recording station site for deconvolution and its compatibility with the target site, (3) deconvolution of the selected record to remove local site effects from the recorded ground motion, and (4) scaling of the deconvolved motion to account for differences in the source-to-site distance between the recording station and the target site. As part of the proposed procedure, a novel (amplitude-duration) scaling method is presented. Results from one-dimensional (1D) effective-stress analysis of two target Christchurch sites using input motions from the proposed procedure are used to critically evaluate the procedure and discuss essential requirements for its successful application.

Effects of Soil Parameter Variabilities on the Estimation of Ground-Motion Amplification Factors

2019 ◽  
Vol 35 (2) ◽  
pp. 907-928 ◽  
Author(s):  
Bo Li ◽  
Mahesh D. Pandy ◽  
Kao-Shan Dai ◽  
Yang Lu ◽  
Yu-Zhou Zhou ◽  
...  
Keyword(s):  
Ground Motion ◽  
Soil Column ◽  
Response Analysis ◽  
Soil Profiles ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Amplification Factors ◽  
Soil Parameter ◽  
Ground Motion Amplification ◽  
The Mean

Ground-motion amplification factors (GMAFs) are used to characterize amplification of a ground motion propagating from the bedrock to the ground surface. They are usually determined by ground response analysis, in which the soil parameter variabilities and input motion uncertainties contribute to their uncertainty. The construction of design response spectra requires mean GMAFs or GMAFs with different probability levels. Thus, it is significant to study the sensitivity of soil parameter variabilities and the number of random soil profiles for the estimation of GMAFs. This study investigates the minimum number of random soil profiles required to represent the extent of the epistemic uncertainty in the GMAFs obtained from ground response analysis. It shows that at least 20 and 60 random soil profiles are respectively required to estimate the mean and standard deviations of GMAFs with the maximum relative difference below 10%. In addition, potential reasons for a reduction in the mean GMAFs resulting from randomization of the soil column properties are discussed.

Investigation of the Performance of Simplified Constitutive Models in Nonlinear 1D Effective Stress Ground Response Analysis

2021 ◽  
Author(s):  
Caroline Bessette ◽  
Samuel Yniesta
Keyword(s):  
Pore Pressure ◽  
Ground Motion ◽  
Effective Stress ◽  
Spectral Response ◽  
Constitutive Models ◽  
Excess Pore Pressure ◽  
Response Analysis ◽  
Total Stress ◽  
Ground Response ◽  
Ground Response Analysis

ABSTRACT Several building codes, such as the National Building Code of Canada, recommend that an effective stress ground response analysis be performed if a liquefiable stratum is identified within a soil profile. Although, constitutive models for total stress ground response analysis have been well verified against earthquake recordings, existing models for effective stress ground response analysis have yet to be thoroughly validated. This article investigates the predictions of five pore pressure models derived for effective stress ground response analysis. First, a dataset of five downhole arrays and two centrifuge experiments in which a potential of liquefaction was identified is presented. The profiles and ground-motion recordings are selected to represent a broad range of soil properties, ground-motion intensities, and excess-pore pressure generation levels. The differences between predictions of the effective stress models against commonly used 1D ground response total stress equivalent-linear and nonlinear analyses are evaluated. The predicted and measured motions are compared in terms of spectral response and amplification factor. The pore pressure response of all models is evaluated as a function of shear strain and found to agree well with published correlations representing the expected behavior of liquefiable soils. Although, the models show the ability to capture liquefaction triggering, the results indicate that for the selected dataset, total stress simulations were found to be, at least, as precise and accurate as the effective stress simulations. Therefore, simplified models for effective stress ground analysis should be used with caution by practicing engineers to predict surface spectra but can be used confidently to assess the potential for liquefaction triggering.

scholarly journals Seismic Ground Response Analysis of Input Earthquake Motion and Site Amplification Factor at KUET

2021 ◽  
pp. 45-54
Author(s):  
Sonia Akter
Keyword(s):  
Ground Motion ◽  
Shear Wave Velocity ◽  
Amplification Factor ◽  
Site Response ◽  
Site Amplification ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Kobe Earthquake ◽  
Earthquake Motion

Ground motion is the movement of the earth's surface due to explosions or the propagation of seismic waves. In the seismic design process, ground response analysis evaluates the impact of local soil conditions during earthquake shaking. However, it is difficult to determine the dynamic site response of soil deposits in earthquake hazard-prone areas. Structural damage has a great influence on the selection of input ground motion, and in this study, the importance of bedrock motion upon the response of soil is highlighted. The specific site response analysis is assessed through “DEEPSOIl" software with an equivalent linear analysis method. Furthermore, four input motions including Kobe, LomaGilroy, Northridge, and Chi-Chi were selected to obtain normalized response spectra. This study aims to obtain the site amplification of ground motion, peak spectral acceleration (PSA), and maximum peak ground acceleration (PGA) based on shear wave velocity from the detailed site-specific analysis of Bangabandhu Sheikh Mujibor Rahman hall at Khulna University of Engineering & Technology. The maximum shear wave velocity obtained was 205 m/s while the amplification factor varied from 4.01 (Kobe) to 1.8 (Northridge) for rigid bedrock properties. Furthermore, the Kobe earthquake produced the highest (4.3g) PSA and the Northridge earthquake produced the lowest (1.08g) PSA for bedrock, with Vs=205 m/s. The surface PGA values were acquired in the range of 0.254g (Northridge) to 0.722g (Kobe), and the maximum strain values for Kobe earthquakes were in the range of 0.016 to .303. Therefore, the surface acceleration values were very high (>0.12g) for the Kobe earthquake motion.

A Site Specific Study on Evaluation of Design Ground Motion Parameters

2012 ◽  
pp. 18-42
Author(s):  
A. Boominathan ◽  
Krishna Kumar S.
Keyword(s):  
Seismic Hazard ◽  
Ground Motion ◽  
Hazard Analysis ◽  
Seismic Hazard Analysis ◽  
Response Analysis ◽  
Ground Response ◽  
Ground Response Analysis ◽  
Site Specific ◽  
Specific Analysis ◽  
A Site

Design ground motions are usually developed by one of the two approaches: site-specific analyses or from provisions of building codes. Although contemporary codes do consider approximately the site effects, they provide more conservative estimates. Hence it is preferred to carry out site specific analysis which involves both the seismic hazard analysis and ground response analysis. This article presents a site specific analysis for a seismically vulnerable site near Ahmedabad, Gujarat. The seismic hazard analysis was carried out by DSHA approach considering seismicity and seismotectonics within 250km radius. The site is predominantly characterized by deep stiff sandy clay deposits. Extensive shear wave velocity measurement by cross hole test is used for site classification and ground response analysis. The ground response analysis was carried out by equivalent linear approach using SHAKE2000. It is found that the deep stiff soil site considered is found to amplify the ground motion. The site specific response spectra obtained from RRS analysis is compared with the codal provision which reveals high spectral acceleration in site specific spectra for mid period range.

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