Seismology%20and%20Earthquake%20Engineering%20:Introduction%20Lecture%203

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
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
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
Site Response
1989 Loma Prieta Earthquake M 7.1 Over 60 miles
away
Oakland
San Francisco
18
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
Engineering for Earthquakes
Ground Failure
Landslides
Yungay, Peru
20
Engineering for Earthquakes
Ground Failure
Landslides
Before
21
Engineering for Earthquakes
Ground Failure
Landslides
Before
22
Engineering for Earthquakes
Ground Failure
Landslides
Taiwan
23
Engineering for Earthquakes
Ground Failure
Liquefaction
Loose Sand
24
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
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
Seismic Loading on Structures
34
Seismic Loading on Structures
Earthquake motion
35
Seismic Loading on Structures
To prevent excessive movement, must restrain
rotation and/or lengthening/shortening
36
Types of structures Moment frame
37
Types of structures Braced frame
38
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
Structural Materials
Concrete Heavy, brittle by itself Ductile with
reinforcement
42
Structural Materials
Prestressed Concrete Strands tensioned during
fabrication
43
Structural Materials
Prestressed Concrete Strands tensioned during
fabrication
Beam on ground no stress
Unreinforced
Prestressed
44
Structural Materials
Steel Light, ductile Easy connections
45
Structural Damage
Masonry
Iran
46
Structural Damage
Timber
47
Structural Damage
Timber
48
Structural Damage
Reinforced Concrete
49
Structural Damage
Reinforced Concrete
Insufficient confinement
50
Structural Damage
Reinforced Concrete
Increased confinement
51
Structural Damage
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
Soil Improvement
Densification
Vibroflotation
56
Soil Improvement
Grouting/Mixing
57
Structural Retrofitting
Column jacketing
58
Structural Retrofitting
Column jacketing
External ties
59
Structural Retrofitting
Fiber composite wrap
Column jacketing
60
Structural Retrofitting
Bracing
61
Structural Retrofitting
Shear Walls
62
New Structural Systems
63
New Structural Systems
64
New Structural Systems
65
New Structural Systems
66
New Structural Systems
67
New Structural Systems
Base isolation
Ground shaking transmits force into structure
Ground moves, structure doesnt
68
New Structural Systems
Base isolation
Rubber bearings
69
New Structural Systems
Dampers shock absorbers