Site Response Analysis for “Side” Soil Profiles

2020 ◽  
pp. 11-17
Author(s):  
Alexander Tyapin ◽  
Nikita Antonov
Keyword(s):  
Site Response ◽  
Time History ◽  
Response Spectra ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Soil Profiles ◽  
Seismic Excitations ◽  
Control Motion ◽  
The Difference ◽  
Upper Boundary

The authors suggest a new procedure of Site Response Analysis (SRA) for the so-called “side” (or additional) soil profiles – Low Boundary (LB) and Upper Boundary (UB). Standards require the analyses of these profiles in addition to the Best Estimate profile (BE) to account for the uncertainty in the input data about soil properties. The authors suggest stopping using the same input time history for all three profiles as a control motion at the surface, because it corresponds to the different physical seismic excitations coming form the depth. This is not in linewith the ideology of Standards. Instead the authors suggest using the same time history as a control motion at the outcropped surface of the underlying half-space. This is also not completely correct, because for these three profiles (BE, UB and LB) the underlying half-spaces are also different. However, due to the physical considerations if all half-spaces are stiff enough, the error should not be so important. The effect of the proposed change is demonstrated on a particular site. The changes in the velocity and damping profiles have proved to be negligible, but the difference in the resulting response spectra at the outcropped surface of the foundation mat has proved to be significant. Generally, the response spectra for the “side” profiles came closer to spectrum for the BE profile. This result reflects the real world logic.

scholarly journals Design Response Spectra Based on Earthquake Hazard Maps and Specific Soil Properties at Indonesian Ports According to SNI 1726 2019

2021 ◽  
Vol 17 (1) ◽  
pp. 41-54
Author(s):  
Christino Boyke Surya Permana
Keyword(s):  
Site Response ◽  
Response Spectrum ◽  
Earthquake Hazard ◽  
Response Spectra ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Spectral Acceleration ◽  
Hazard Maps ◽  
The Difference ◽  
S Period

Indonesia has a new seismic code, namely SNI 1726 2019 (SNI 2019). It is developed based on the 2017 Indonesian Earthquake Source, Hazard Maps, and ASCE 7-16. This paper is intended to explain the procedure for calculating response spectrum according to SNI 1726 2019, at ten ports located in Indonesia. The results are then verified with the software RSA2019.  Furthermore, it will be compared to SNI 1726 2012 (SNI 2012) to see the difference in spectral acceleration value (Sa). The result presents that the ports located in Sorong and Banggai have the highest Sa, whereas the port in Banjarmasin has the smallest value. Port in Surabaya and Tuban have nearly the same Sa due to their close location, while Banyuwangi has a Sa value slightly above them. The ports in Padang, Lampung, and Penajam must use a specific site response analysis to determine the design response spectra, which is not discussed in this paper. The comparison with SNI 2012 shows that the response spectra of SNI 2019 have a higher Sa than SNI 2012. However, in some areas such as Tuban and Sorong, the Sa of SNI 2012 at 0.1 to 0.6 s period are larger than SNI 2019.  

Effect of Parameters on Equivalent Number of Cycles Using ‎Nonlinear Seismic Site Response Analysis

2011 ◽  
Vol 255-260 ◽  
pp. 2365-2369
Author(s):  
Emad Gheibi ◽  
Mohammad Hosein Bagheripour
Keyword(s):  
Site Response ◽  
Time History ◽  
Current Approach ◽  
Earthquake Magnitude ◽  
Soil Liquefaction ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Nonlinear Site Response ◽  
Equivalent Number ◽  
Number Of Cycles

The concept of equivalent number of uniform stress cycles, is essential for assessment of soil liquefaction potential. In this regard, various procedures are used to convert random acceleration time history to uniform cycles having amplitude of 0.65 of peak acceleration. Equivalent number of cycles (Neq) defines equivalent energy generated by harmonic loading as that imposed by irregular motion during an earthquake. Neq is assumed to be a function of earthquake magnitude. Over the past years, in accordance with development in methods of soil liquefaction evaluation, various methods have been proposed to determinate equivalent number of cycles. In particular, parameters like site to source distance (r), have been related directly to Neq. In this study, more than 80 earthquake records have been investigated and their Neqs are assessed using energy approach and nonlinear site response analysis. It is shown that equivalent number of cycles is related to earthquake magnitude (M), r and depth of originated signals. Unlike previous methods which result in scatter in output data, current approach has led to more uniform and consistent results for each earthquake.

scholarly journals A Site-Specific Response Analysis: A Case Study in Hanoi, Vietnam

2020 ◽  
Vol 10 (11) ◽  
pp. 3972 ◽  
Author(s):  
Van-Quang Nguyen ◽  
Muhammad Aaqib ◽  
Duy-Duan Nguyen ◽  
Nguyen-Vu Luat ◽  
Duhee Park
Keyword(s):  
Site Response ◽  
Response Spectra ◽  
Response Analysis ◽  
Specific Response ◽  
Site Class ◽  
Soil Stiffness ◽  
Design Spectrum ◽  
Class D ◽  
The Difference ◽  
A Site

A series of one-dimensional (1-D) site response analyses were performed using the nonlinear (NL) and equivalent linear (EQL) approaches to assess the applicability of the Vietnamese earthquake-resistance design code TCVN 9386: 2012. Six soil profiles were selected from three districts in Hanoi (Vietnam). A number of ground motions compatible with the rock design spectrum were used as input for carrying out analyses. The results highlight that the calculated response is higher than the design spectrum for site class C and lower for site class D. The normalized response spectra of the EQL approach results are higher than those of the NL approach. Moreover, the peak ground accelerations at the surface from EQL analyses are greater than those of the NL method because the latter generates a higher amount of nonlinearity. The results from the NL approach also illustrate that the deamplification phenomenon occurs in the soft soils of the Hanoi region (e.g., soil profile P3 and P5 of site class D). Additionally, the shear strains calculated from the NL method are closely matched with those from the EQL method, the difference between them increasing with a decrease in soil stiffness.

scholarly journals Influence of thick soft superficial layers of seabed on ground motion and its treatment suggestions for site response analysis

2021 ◽  
Vol 13 (1) ◽  
pp. 1273-1289
Author(s):  
Qifeng Jiang ◽  
Mianshui Rong ◽  
Wei Wei ◽  
Bin Zhang ◽  
Jixin Wang
Keyword(s):  
Ground Motion ◽  
Site Response ◽  
Response Spectra ◽  
Activity Level ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Physical Parameters ◽  
Layer By Layer ◽  
Ocean Engineering ◽  
Acceleration Time Histories

Abstract The thick soft superficial layers of the seabed greatly influence ground motion generally. It is worth studying how to find out the influence of these soft layers on ground motion parameters and determine reasonable seismic fortification parameters for ocean engineering. Numerical experiments of site response analysis are designed using two offshore engineering sites in this study. First, the borehole profiles are selected and stripped layer by layer to generate new profiles. Second, 108 acceleration time histories are synthesized which basically represent the diversity of input motions’ amplitude and frequency. Third, a method that can automatically calculate characteristic periods and normalize response spectra is created to improve calculation efficiency. Fourth, peak accelerations, response spectra, and characteristic periods at different depths of the profiles with different stripping depths are calculated. The results show that the thick soft superficial layers can significantly decrease peak ground accelerations and increase characteristic periods, resulting in serious “low-fat” response spectra. The situation can be greatly improved by stripping off the soft superficial layers. After stripping off the thick soft superficial silt layers, if stripping is continued further, the variation in the superficial amplification ratios of peak accelerations and superficial characteristic periods will no longer be drastic, and the superficial amplification ratios and characteristic periods both tend to be mostly the same. The relative deviation of the amplification ratio of peak ground acceleration between a profile stripped and that without stripping can be 143%, and it can be 83% for characteristic period. It is advisable to strip off thick soft superficial layers to perform site response analysis, and the shear force at the bottom of the silt should be considered in engineering based on local seismic activity level, and the silt’s and the structure’s physical parameters.

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