Seismology and Earthquake Engineering :Introduction Lecture 3 - PowerPoint PPT Presentation

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Seismology and Earthquake Engineering :Introduction Lecture 3

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  1. Seismology and Earthquake Engineering :IntroductionLecture 3

  2. Hall of Fame (famous earthquakes) 1906 San Francisco

  3. Hall of Fame (famous earthquakes) 1964 Niigata

  4. Hall of Fame (famous earthquakes) 1964 Alaska

  5. Hall of Fame (famous earthquakes) 1960 Chile

  6. Hall of Fame (famous earthquakes) 1971 San Fernando

  7. Hall of Fame (famous earthquakes) 1985 Mexico City

  8. Hall of Fame (famous earthquakes) 1989 Loma Prieta

  9. Hall of Fame (famous earthquakes) 1994 Northridge

  10. Hall of Fame (famous earthquakes) 1995 Kobe

  11. Hall of Fame (famous earthquakes) 1999 Chi Chi (Taiwan)

  12. Engineering for Earthquakes • Geotechnical Engineering Considerations • Site Response – modification of ground • motions by local geologic conditions • Ground Failure – mass movement of soil • (liquefaction, settlement, landslides, etc)

  13. Path Source Site Response Problem: Predict the response of a soil deposit due to earthquake excitation Site

  14. Site Response • Soil response depends on: • Type of soil • Thickness of soil • Stiffness of soil Bedrock • Results: • Some soil deposits amplify bedrock motion • Some soil deposits de-amplify bedrock motion • Some soils do both

  15. Communications Building 30 m soft clay University Rock Site Response • 1985 Mexico City Earthquake • M = 8.1 • Over 200 miles away Young lake deposits

  16. Site Response • 1985 Mexico City Earthquake • M = 8.1 • Over 200 miles away Rock – 0.03g Soft clay – 0.15g Soft clay amplified bedrock motions by factor of 5

  17. Yerba Buena Island Treasure Island Yerba Buena Island Treasure Island Rock Soft soil Site Response • 1989 Loma Prieta Earthquake • M = 7.1 • Over 60 miles away Oakland San Francisco

  18. Soft soil Rock Site Response • 1989 Loma Prieta Earthquake • M = 7.1 • Over 60 miles away Soft soil amplified bedrock motions by factor of 2-3 Rock – 0.06g Soft soil – 0.15g

  19. Before After Engineering for Earthquakes Ground Failure Landslides Yungay, Peru

  20. After Engineering for Earthquakes Ground Failure Landslides Before

  21. After Engineering for Earthquakes Ground Failure Landslides Before

  22. El Salvador Engineering for Earthquakes Ground Failure Landslides Taiwan

  23. Earthquake shaking High contact forces Low contact forces Engineering for Earthquakes Ground Failure Liquefaction Loose Sand

  24. Earthquake shaking Engineering for Earthquakes Ground Failure Liquefaction • Soil wants to densify • Water pressure increases • Contact forces decrease • Strength decreases High contact forces Low contact forces

  25. Niigata, Japan Engineering for Earthquakes Ground Failure Liquefaction Niigata, Japan

  26. Engineering for Earthquakes Ground Failure Liquefaction Moss Landing, California

  27. Engineering for Earthquakes Structures

  28. Engineering for Earthquakes • Structural Engineering Considerations • Design of new structures • Retrofitting of existing structures

  29. Engineering for Earthquakes • Design Considerations • Performance objectives Immediate Occupancy Life Safety Collapse Prevention

  30. Immediate Occupancy

  31. Life Safety

  32. Collapse Prevention

  33. Vertical seismic loads • Gravity load (vertical) • Weight of structure • Weight of contents Horizontal seismic loads Earthquake motion Seismic Loading on Structures

  34. Seismic Loading on Structures Earthquake motion

  35. Rotation Shortening Lengthening Seismic Loading on Structures To prevent excessive movement, must restrain rotation and/or lengthening/shortening

  36. Strong beam/column connections resist rotation • Types of structures • Moment frame

  37. Diagonal bracing resists lengthening and shortening • Types of structures • Braced frame

  38. Shear wall resists rotation and lenthening/ shortening Concrete Shear Wall

  39. Structural Materials • Masonry • Very brittle if unreinforced • Common in older structures • Common facing for newer structures

  40. Structural Materials Timber

  41. Rebar Structural Materials • Concrete • Heavy, brittle by itself • Ductile with reinforcement

  42. Tension Tension Prestressing strands Structural Materials • Prestressed Concrete • Strands tensioned during fabrication

  43. Prestressing strands Rebar Structural Materials • Prestressed Concrete • Strands tensioned during fabrication Beam on ground – no stress Unreinforced Prestressed

  44. Structural Materials • Steel • Light, ductile • Easy connections

  45. Watsonville San Francisco Structural Damage Masonry Iran

  46. Structural Damage Timber

  47. Soft first floor Structural Damage Timber

  48. Axial Overturning Lateral Rebar Reinforced Concrete Column Structural Damage Reinforced Concrete

  49. Structural Damage Reinforced Concrete Insufficient confinement

  50. Structural Damage Reinforced Concrete Increased confinement