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Site-Specific Seismic Hazard Analysis and Design Ground Motions

1.6 CEUs | Monday–Tuesday, September 23–24

Instructor

Ayman Shama, Ph.D., P.E., LEED AP BD+C, F.ASCE

Purpose and Background

Specification of design ground motions and their parameters is one of the most challenging tasks in earthquake engineering. Site specific seismic hazard analyses involve evaluation of ground motion parameters at a particular site. Seismic hazard analysis can be done deterministically. Nevertheless, due to uncertainties in earthquake size, location, and time of occurrence; the approach is undertaken probabilistically. This seminar will cover all aspects related to design ground motions by going first through the probabilistic site specific seismic hazard analysis and the evaluation of the hazard spectrum at rock. Next, the process of synthesizing rock design ground motions that are compatible with the hazard spectrum are explained. Ground response analysis to evaluate design ground motions at the surface and different soil levels is covered. Finally, Phenomena such as liquefaction and lateral spreading associated with soil behaviors due to cyclic earthquake ground motions are also presented. The seminar will conclude with seismic slope stability methods.

Topics to be discussed include:

  • Seismicity and characteristics of earthquakes: seismic waves; fault mechanisms; stress drop; attenuation relationships for ground motions; ground motion response spectrum
  • Site specific seismic hazard analysis: Deterministic approach; evaluation of the uniform hazard spectrum through probabilistic methods; the conditional mean spectrum
  • Earthquake rock design ground motions: Outline of the theoretical and seismological models; wavelet-based spectrum compatible methods; code requirements
  • Ground response analyses: nonlinear behavior of soil and strain limits; dynamic soil properties required for ground response; equivalent linear model; one dimensional site response analysis
  • Liquefaction of soils: liquefaction behavior of saturated soils during earthquakes; lateral spreading; mitigation of liquefaction hazard
  • Seismic slope stability: pseudo static method; Newmark method; Seed-Makdisi method for embankments

Seminar Benefits and Learning Outcomes

  • Understand the basic distinctions between different ground motion parameters and their significance in the process of site specific seismic hazard analysis
  • Learn about different spectra, and their applications in earthquake engineering
  • Learn to carry out a site specific probabilistic seismic hazard analysis using simple tools
  • Learn to develop an earthquake ground motion for your project
  • Understand ground response analysis and know how to interpret the results
  • Understand how liquefaction occurs for saturated sands during earthquakes
  • Learn about lateral spreading Phenomenon and lateral spreading loads on deep foundations
  • Learn to carry out liquefaction potential evaluation at a site using simple tools
  • Understand how to run seismic design of an embankment

Assessment of Learning Outcomes

Students' achievements of the learning outcomes will be assessed through solved examples and problem-solving following each session.

Who Should Attend?

This seminar should be of interest to structural engineers, bridge engineers, geotechnical engineers, project managers, architects, and decision makers who wish to learn advanced methods of earthquake engineering.

Seminar Outline

Day 1: 8:30 a.m. - 5:00 p.m. with a 1 hour lunch break

Seismicity

  • Plate boundaries and seismic sources
  • Shallow faults and stress drop
  • Body and surface seismic waves, seismic moment, and earthquake magnitudes

Ground motion parameters

  • Peak ground acceleration and attenuation equations
  • Frequency content
  • The Fourier spectrum
  • Corner and cutoff frequencies
  • The Power spectrum
  • Earthquake duration
  • Response and design spectra

Site-specific seismic hazard analysis

  • Deterministic approach
  • Solved example
  • Aleatory and epistemic uncertainties in seismic hazard
  • Elements of probabilistic site specific seismic hazard analysis
  • Annual frequency of exceedance of events on a seismic source
  • Magnitude recurrence relationships
  • Distance probability distributions
  • Logic trees
  • Determination of the uniform hazard spectrum
  • Simple tool application
  • Conditional mean spectrum

Synthesis of earthquake ground motions

  • Spectrum compatible ground motions
  • Internet-based tool to calculate design ground motions
  • Codes requirements for earthquake design ground motions
  • Other simulation methods
  • Generation using theoretical spectra
  • Generation using Seismological models

Day 2: 8:30 a.m. - 5:00 p.m. with a 1 hour lunch break

Dynamic soil behavior and site response

  • Strain limits and methods of analyses
  • Equivalent linear model for soil response
  • Evaluation of soil dynamic properties
  • Field tests
  • One dimensional ground response analysis
  • Example: Excel spreadsheet tool

Liquefaction of saturated soils during earthquakes

  • Critical state of soil
  • Behavior of saturated sand under cyclic loads
  • Code recommended procedure for evaluating liquefaction
  • Evaluation of CSR and CRR using charts
  • Evaluation of CSR and CRR using empirical models
  • Example using spreadsheet
  • Consequences of liquefaction
  • Method of evaluation: the lateral spreading index
  • Estimation of liquefaction settlement
  • Flow failure
  • Example using spreadsheet
  • Mitigation of liquefaction hazard

Seismic stability of slopes

  • Pseudo static method
  • Newmark method
  • Internet-based application of Newmark method
  • Seismic stability of dams and embankments
  • Solved example

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