eq1 introduction to earthquake engineering. eq2 sequence plate movement type of faults wave...
TRANSCRIPT
SequenceSequence
Plate movementPlate movement
Type of faultsType of faults
Wave motionWave motion
Energy releaseEnergy release
Urban earthquake riskUrban earthquake risk
Structural performance levelStructural performance level
Evaluation approachEvaluation approach
great earthquake
Tibet
4-10 m
2-20 msurface rupture 1.5 m co-seismic
subsidence
the longer the inactivity the bigger the 'quake’
FaultsFaultsThrough the study of faults and their effects, much can be learned
about the size and recurrence intervals of earthquakes. Faults
also teach us about crustal movements that have produced
mountains and changed continents. Stresses often continue to
build until they exceed the strength of the bond in that section of
crust. The rock then breaks, and an earthquake occurs,
sometimes releasing massive amounts of energy.
Faults vary in length from a few centimeters to hundreds of
kilometers across. Displacements of one side of the fault over the
other vary from fractions of a meter to many kilometers. In many
cases the displacement is not confined to a single fracture but is
distributed throughout a fault zone. Many faults do not rupture the
surface, but when the surface is broken, the fault line is visible as
a fault trace or outcrop.
Contd…
Vertical or horizontal movement may occur along a fault plane.
Sometimes both vertical and horizontal movement occur
simultaneously. Faults are named according to the type of
movement that has occurred. The term slip is used to indicate
relative displacement across the fault. When the movement along
the fault plane is generally horizontal, it is a strike-slip fault. These
are also called lateral faults. Offset streams are found along active
strike-slip faults. A transform fault is a zone of lateral movement
along which the ridges and rises have been offset and along
which the displacement suddenly stops or changes form and
direction. When the movement along the fault plane is
predominately vertical, it is a dip-slip fault. There are sub-
classifications within this category.
Contd…
FaultsFaults
A normal fault occurs when the earth above the fracture moves down in respect to the earth below the fracture. A reverse fault occurs when the rocks above the fracture move up with respect to those below. A reverse fault with an angle of less than 45 degrees is called a thrust fault. Thrust faults are generally characterized by older rocks resting on younger rocks, although in some cases younger rocks may be thrust over older rocks.
FaultsFaults
HAZARDSHAZARDSHAZARDSHAZARDS
ELEMENTS OF ELEMENTS OF URBAN EARTHQUAKE URBAN EARTHQUAKE RISKRISKELEMENTS OF ELEMENTS OF URBAN EARTHQUAKE URBAN EARTHQUAKE RISKRISK
EXPOSUREEXPOSUREEXPOSUREEXPOSURE
VULNERABILITYVULNERABILITYVULNERABILITYVULNERABILITY LOCATIONLOCATIONLOCATIONLOCATION
RISKRISKRISKRISK
Structural Performance LevelsStructural Performance Levels
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Serviceability CollapsePrevention
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ImmediateOccupancy
Damage0% 99%
Serviceability LevelServiceability Level
Negligible structural Negligible structural and nonstructural and nonstructural damagedamage
Utilities are availableUtilities are available Facility is available Facility is available
for immediate re-use for immediate re-use Repair costs are Repair costs are
minimal to nilminimal to nil
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Immediate Occupancy LevelImmediate Occupancy Level
Negligible structural damageNegligible structural damage
Minor nonstructural damageMinor nonstructural damage
Building is safe to occupy but Building is safe to occupy but
may not functionmay not function
Limited interruption of Limited interruption of
operationsoperations
Repair Cost < 15%Repair Cost < 15%
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Collapse Prevention LevelCollapse Prevention Level
Extensive structural and Extensive structural and
non-structural damagenon-structural damage
Extended loss of useExtended loss of use
Repair may not be Repair may not be
practicalpractical
Repair costs >> 30%Repair costs >> 30%
Global Response & PerformanceGlobal Response & Performance
Structural Displacement
Lo
adin
g S
eve
rity
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Evaluation ApproachEvaluation Approach
0 .5 1.0 1.5 2.0 2.5
Spectral Acceleration at Period T
10-1
10-2
10-3
10-4
10-5
Annual Pro
babili
ty o
f Exce
edance
1- Select Hazard Level
2- Determine groundMotion Sa
t
3- Run Analysis
4- DetermineDrift & ComponentDemands
Lateral Displacement -
La
tera
l Fo
rce
- V
CP0
Collapse Preventionmargin = 1.0
Life Safetymargin = 1.33to 1.5
LS
Collapse margin > 1.0
ImmediateOccupancy
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5- Determine Performance
6- Pass or Fail Criterion evaluated on component by component basis