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Earthquake Engineering

Earthquake Engineering. “8.9 Quake Strikes Japan—Nation’s worst in 140 years”. Airport, Sendai, Japan. Fukushima- Daichi nuclear power plant. Earthquakes Past and Present. Sendai, Japan (8.9 magnitude). historical Seismicity Map. http://earthquake.usgs.gov/eqcenter/recenteqsww/.

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Earthquake Engineering

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  1. Earthquake Engineering

  2. “8.9 Quake Strikes Japan—Nation’s worst in 140 years” Airport, Sendai, Japan Fukushima-Daichi nuclear power plant

  3. Earthquakes Past and Present Sendai, Japan (8.9 magnitude) historical Seismicity Map http://earthquake.usgs.gov/eqcenter/recenteqsww/ http://earthquake.usgs.gov/earthquakes/world/seismicity_maps/world.pdf

  4. A pan-global issue…. http://www.mapsofworld.com/world-major-earthquake.htm

  5. Some Major Earthquakes, Past and Present Christchurch, NZ 2011 Talca, Chile 2010 Port-au-Prince, Haiti, 2010 Guandong, China, 2008 Fukuoka, Japan, 2005 Izmit, Turkey, 1999 Northridge, CA, 1994 Mexico City, 1985

  6. Why bother?

  7. Sendai Japan Earthquake 2011 Amazing engineering: Buildings Sway Without Collapsing

  8. Different Buildings Different model parameters

  9. The Fundamental Questions • Can we predict how different buildings will respond to an earthquake? • How can we use this information to engineer a safe structure

  10. Tabas, Iran 1978 Earthquake Acceleration record is messy. No way to integrate Duhamel’s integral. No worries, computers to the rescue! Relative motion of building and ground Impulse Response Function Measured Acceleration/USGS data

  11. Ground acceleration (units of g) z = 0.05is assumed Z(t) meters marks |z|max If we found |z|max for a continuous range of wo, we’d get the Spectral Displacement (Displacement Spectrum) Z(t) meters Z(t) meters

  12. Averaged Spectra To Many (88) Earthquakes Spectra For El Centro Ground Motion Velocity Acceleration Displacement Natural Period (sec) Figure Credits: L A Chopra, Dynamics of Structures, Chap 6 Right: G. Housner “Strong Ground Motion” in Earthquake Engineering, R Wiegel, editor.

  13. Tripartite Representation SD = spectral displacement SV = spectral velocity SA = spectral acceleration SA/wo = SV = woSD

  14. Housner Spectrum Spectrum for one earthquake Spectrum averaged over 88 earthquakes

  15. Housner spectrum for z = 0.05

  16. Seattle Monorail • Seattle, WA is a beautiful city, but is prone to large earthquakes. The monorail on the bridge has previously been measured to have a natural period of 2 s. Damping is assumed to be 2%. During an earthquake, is the trolley likely to derail? Use the Housner spectrum to find out! Picture from: http://bcostin.wordpress.com/2008/02/25/seattle-worlds-fair-1962-postcards/seattle-monorail/

  17. Beach House • You are hired as an architectural engineer to build a California dream house on a hillside. The structure can be idealized as shown (on chalkboard). The frame is built out of concrete (E = 30x109 Pa). The support columns have a cross section of 10 inches squared. Assume damping is 5%. Determine the base shear in each column, which is more likely to fail?

  18. What we need to guard against Buckling SmaSHING/POUNDING

  19. Base Isolation Configuration Figure credit: Michael D. Symans, PhD Rensselaer Polytechnic Institute: http://www.nibs.org/client/assets/files/bssc/Topic15-7-SeismicIsolation.pdf

  20. Reduced Shearing in Superstructure. Conventional Building Base-Isolated Building Figure credit: Michael D. Symans, PhD Rensselaer Polytechnic Institute: http://www.nibs.org/client/assets/files/bssc/Topic15-7-SeismicIsolation.pdf

  21. Lead-Rubber Bearing Shear Modulus E ~ 0.5 – 1.0 MPa Figure credit:sMichael D. Symans, Rensselaer Polytechnic Institute: http://c.ymcdn.com/sites/www.nibs.org/resource/resmgr/BSSC/Topic15-7-SeismicIsolation.pdf

  22. LRB decreases keff and wo Reduces shearing in columns…………but increases displacement

  23. LRB Isolation in Action Rubber Base Isolators

  24. Lead Rubber Bearing (LRB) in Action UCSD testing facility LBRs in Japan

  25. How do we model what we just saw? Displacement , u

  26. Frictional Pendulum System Image credit: http://www.asee.org/documents/sections/pacific-southwest/2008/Porbaha_Ali_et_al%20Base%20isolation.pdf

  27. Concept of Frictional Pendulum Image credits: http://www.asee.org/documents/sections/pacific-southwest/2008/Porbaha_Ali_et_al%20Base%20isolation.pdf http://nees.buffalo.edu/docs/dec304/FP-DC%20Report-DEMO.pdf; laconservancy.org

  28. Frictional Pendulum Restoring/Recentering Force Frictional Force Pendulum Period: T

  29. The quantitative model Frictional Force Restoring/Recentering Force

  30. Force vs. Displacement Hysteresis Loop

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