Effects of Ground Slope on Site Factors and Development of Adjustment Factors Using 2D FE Analysis for Charleston, SC
Publication: Geo-Congress 2023
ABSTRACT
In engineering practice, one-dimensional seismic site response computer programs were used to estimate the spectral responses at the ground surface, assuming level ground conditions. However, in reality, the ground surface and subsurface layers can be inclined, which may affect the propagation of earthquake waves through soil layers. This study aims to conduct two-dimensional (2D) site response analyses to develop slope adjustment factors to update the site coefficients computed from one-dimensional (1D) analyses for Charleston, SC. Eleven shear wave velocity profiles were generated considering the mean shear wave velocity (Vs) profile, mean ± 1σ (σ = standard deviation) of the natural logarithm of Vs, and variation in the thickness of quaternary soil layers. The modulus reduction and damping curves were developed based on the region-specific relationships. Four earthquake time histories that represented site-specific seismic hazards were selected. Finally, 308 2D finite element models were developed and analyzed considering seven ground inclinations (0o, 1o, 2o, 3o, 4o, 5o, and 6o), 11 Vs profiles, and four earthquake time histories. The results show significant differences between 1D and 2D analyses, justifying the importance of considering sloping ground conditions in seismic analysis to capture the realistic ground motion characteristics at the site. Based on the results, a set of slope adjustment factors were developed for various average shear wave velocities at top 30 m (Vs30) and ground inclination (θ) cases. These slope adjustment factors can account for the mild sloping ground (θ≤6o) effect by multiplying it with site factors obtained from the 1D analysis for their respective combination of Vs30, ground inclination, and spectral period.
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Information & Authors
Information
Published In
Geo-Congress 2023
Pages: 246 - 256
History
Published online: Mar 23, 2023
ASCE Technical Topics:
- Analysis (by type)
- Continuum mechanics
- Dynamics (solid mechanics)
- Earthquakes
- Engineering fundamentals
- Engineering mechanics
- Finite element method
- Flow (fluid dynamics)
- Fluid dynamics
- Fluid mechanics
- Fluid velocity
- Geohazards
- Geomechanics
- Geotechnical engineering
- Geotechnical investigation
- Hydrologic engineering
- Methodology (by type)
- Numerical methods
- Seismic tests
- Seismic waves
- Shear waves
- Site investigation
- Slopes
- Solid mechanics
- Tests (by type)
- Two-dimensional analysis
- Water and water resources
- Wave velocity
- Waves (mechanics)
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