1. Seismology and Earthquake Engineering :Introduction Lecture 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. Site Response Problem:
Predict the response of a soil deposit due to earthquake excitation
Site
Path
Source

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

16. Soft clay amplified bedrock motions by factor of 5
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. Site Response 1989 Loma Prieta Earthquake M = 7.1 Over 60 miles away
Yerba Buena Island
Treasure Island
Oakland
Yerba Buena
Island
Treasure
San Francisco
Rock
Soft soil

18. Soft soil amplified bedrock motions by factor of 2-3
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
Soft soil – 0.15g
Rock

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

20. Engineering for Earthquakes
Ground Failure
Landslides
After
Before

21. Engineering for Earthquakes
Ground Failure
Landslides
After
Before

22. Engineering for Earthquakes
Ground Failure
Landslides
El Salvador
Taiwan

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

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

25. Engineering for Earthquakes
Ground Failure
Niigata, Japan
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 Horizontal seismic loads
Seismic Loading on Structures
Vertical seismic loads
Gravity load (vertical)
Weight of structure
Weight of contents
Horizontal seismic loads
Earthquake motion

34. Seismic Loading on Structures
Earthquake motion

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

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

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

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

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

40. Structural Materials
Timber

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

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

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

44. Structural Materials
Steel
Light, ductile
Easy connections

45. Structural Damage
San Francisco
Masonry
Watsonville
Iran

46. Structural Damage
Timber

47. Structural Damage
Timber
Soft first floor

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

49. Structural Damage
Reinforced Concrete
Insufficient
confinement

50. Structural Damage
Reinforced Concrete
Increased
confinement

51. Structural Damage
Fractured weld
Steel

52. Engineering for Earthquakes
Mitigation of seismic hazards
Geotechnical
Structural

53. Soil Improvement
Mitigation of liquefaction hazards
Densification
Grouting/Mixing

54. Soil Improvement
Densification
Dynamic compaction

55. Gravel inserted as vibroflot is extracted
Soil Improvement
Gravel inserted as vibroflot is extracted
Densification
Vibroflotation

56. Soil Improvement
Grouting/Mixing

57. Structural Retrofitting
Steel jacket
Column jacketing

58. Structural Retrofitting
Column jacketing
External
ties

59. Structural Retrofitting
Column jacketing
Fiber composite wrap
Composite wall retrofit

60. Structural Retrofitting
Bracing

61. Structural Retrofitting
Shear Walls

62. New Structural Systems

63. New Structural Systems

64. New Structural Systems
Post Tensioned Bars (ungrouted)
Fiber Reinforced Grout
U Flexural Plate (UFP) Connector
Foundation

65. Flexural connectors dissipate energy
New Structural Systems
Flexural connectors dissipate energy
Post-tensioned
bars stretch as
walls rock

66. Post-tensioned bars snap walls back into place
New Structural Systems
Post-tensioned bars snap walls back into place

67. Requires something strong vertically, but soft laterally
New Structural Systems
Base isolation
Requires something strong vertically, but soft laterally
Ground shaking transmits force into structure
Ground moves, structure doesn’t

68. New Structural Systems
Base isolation
Rubber bearings

69. New Structural Systems
Dampers – shock absorbers