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Seismology and Earthquake Engineering :Introduction Lecture 3.

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Presentation on theme: "Seismology and Earthquake Engineering :Introduction Lecture 3."— Presentation transcript:

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 Source Path Site

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

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

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

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

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

20 Ground Failure Landslides Engineering for Earthquakes Before After

21 Ground Failure Landslides Engineering for Earthquakes Before After

22 Ground Failure Landslides Engineering for Earthquakes Taiwan El Salvador

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

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

25 Ground Failure Liquefaction Engineering for Earthquakes Niigata, Japan

26 Ground Failure Liquefaction Engineering for Earthquakes 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 Seismic Loading on Structures Earthquake motion Gravity load (vertical) Weight of structure Weight of contents Vertical seismic loads Horizontal seismic loads

34 Seismic Loading on Structures Earthquake motion

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

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

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

38 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 Prestressing strands Tension

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

44 Structural Materials Steel Light, ductile Easy connections

45 Structural Damage Masonry Iran San Francisco Watsonville

46 Structural Damage Timber

47 Structural Damage Timber Soft first floor

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

49 Structural Damage Reinforced Concrete Insufficient confinement

50 Structural Damage Reinforced Concrete Increased confinement

51 Structural Damage Steel Fractured weld

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 Soil Improvement Densification Vibroflotation Gravel inserted as vibroflot is extracted

56 Soil Improvement Grouting/Mixing

57 Structural Retrofitting Column jacketing Steel jacket

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

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

65 Flexural connectors dissipate energy Post-tensioned bars stretch as walls rock

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

67 New Structural Systems Base isolation Ground shaking transmits force into structure Ground moves, structure doesnt Requires something strong vertically, but soft laterally

68 New Structural Systems Base isolation Rubber bearings

69 New Structural Systems Dampers – shock absorbers


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