structures_notes - CEE 431/ESS 465 Introduction to...

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CEE 431/ESS 465 Introduction to Earthquake Structural Engineering Design Ground Motions Most (but not all) earthquakes occur near the boundaries of tectonic plates, which are constantly in motion. Seismicity in the Northwest is dominated by the subduction of the Juan de Fuca plate beneath the North American plate. In the United States, most structures are designed considering ground-motion parameters likely to be exceeded 10% of the time within 50 years. Therefore, according to the Poisson Model, P [ N 1] = 1 – e - λ t = 1 – e - λ 50 = 0.10 Solving for λ , results in λ = 0.00211/year. The average return period is 1/ λ =475 years. Critical structures (major bridges, hazardous facilities, emergency response centers) are often designed for site-specific ground-motion parameters that are the result of a formal Probabilities Seismic Hazard Analysis. The level of ground shaking at a particular site depends on: magnitude and type of earthquake fault (e.g., strike-slip, normal) depth of earthquake source distance from earthquake source to site geological/geotechnical effects, such as reflections, site amplification, liquefaction and landslides.
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structures_notes - CEE 431/ESS 465 Introduction to...

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