scholarly journals Deterministic Investigation of Effect of Stress Drop on Seismic Site Response Analysis of Allahabad City

2020 ◽  
Author(s):  
Keshav Kumar Sharma ◽  
Kumar Pallav ◽  
Shashi Kant Duggal
Keyword(s):  
Stress Drop ◽  
Site Response ◽  
High Stress ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Contour Plot ◽  
Spectral Acceleration ◽  
Ground Acceleration ◽  
Seismic Site Response ◽  
Finite Fault

Abstract Due to the high stress of Faizabad ridge close to Allahabad city and the absence of strong-motion records for any engineering studies, it is essential to use a stochastic model to study the deterministic earthquake scenario of Allahabad city. The work investigates the effect of stress drop for an earthquake on 30 sites (83 boreholes) located across the city using 1-D seismic site response analysis. The ground motion has been simulated for Allahabad fault using stochastic finite fault model for stress drop ranges from ~70 bar to ~200 bars. Simulation results show the Peak Ground Acceleration (PGA) value of 0.026 g and 0.085 g at 70 and 200 bars stress drops, respectively. Site response results reveal that Indian Standard IS: 1893-2002 underestimates the PGA at higher stress drop compared to the estimated spectral acceleration values. Further, the lower stress drop can give a higher mean spectral acceleration at a long-period. Contour plot of surface-level PGA, low and high period spectral acceleration with response spectra for Allahabad city shows the variation with stress drop.

scholarly journals Stress-independent parameters for stress-strain relationship and damping in nonlinear one-dimensional seismic site response analysis

2021 ◽  
Vol 15 (1) ◽  
pp. 14-29
Author(s):  
Nghiem Manh Hien
Keyword(s):  
Finite Element ◽  
Site Response ◽  
Computer Code ◽  
Site Response Analysis ◽  
Response Analysis ◽  
Ground Acceleration ◽  
Maximum Shear Strain ◽  
Seismic Site Response ◽  
Independent Parameters ◽  
Modulus Reduction

The modulus reduction and damping curves represent the nonlinear behavior of soil under cyclic load. In the literature, those curves were produced from lab tests of soil at particular confining stresses. This study developed a set of parameters that can be used to normalize the modulus reduction and damping curves to be stress-independent. The proposed formulations for the stress-independent parameters were implemented in the finite element code SRAP and validated through producing shear modulus reduction and damping curves that match the existed ones. Nonlinear 1D seismic site response analyses were conducted for centrifuge experiments to verify the developed computer code. Comparisons of the analysis results between SRAP and another computer code were presented in terms of maximum and minimum displacement, peak ground acceleration, maximum shear strain profiles, and response spectra. Keywords: backbone curve; hysteretic damping; dynamic soil model; stress-independent parameters; finite element method; nonlinear 1D seismic site response analysis.

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