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National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Innovations in Earthquake EngineeringBase Isolation
Fiber Wrap
Dampers
Steel moment frame solutions Redundancy – helps with progressive collapse
Capacity design principles
In general what’s good for earthquake design helps resist blast loads
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Base Isolation TechnologyOne of the most significant developments in earthquake engineering in the past 35 years
It provides the design profession the ability to design a building that is “operational” after a major earthquake
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
The Goals of Base IsolationProtection of Life – Current Code
Additional Benefits of IsolationProtection of Building Frame
Protection of Non-Structural Components and Contents
Protection of Processes and Function
Provide for an operational facility after the earthquake
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Base IsolationHow It Works
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Isolated Structure Conventional Structure
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Ground Forces are amplified
by a factor of 3 to 4 at the
roof.
Conventional Structure
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Forces reduced by 3 to 6 across the isolators
Forces reduced by 8 to 12 at the roof
Isolated Structure
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
During a Richter 8.0 Earthquake a Seismically Isolated Building Will Behave as if it Were Experiencing a 5.5 Earthquake
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Seismic Isolator
Cover Rubber
Energy Dissipation Core
Steel Reinforcing Plates
Internal Rubber Layers
Bottom Mounting Plate
(Top Mounting Plate Not Shown)
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Friction Pendulum Bearing
SECTION
STAINLESS STEELCONCAVE SURFACE
SELF LUBRICATINGCOMPOSITE LINER
ARTICULATINGSLIDER
PLATECONCAVE
HOUSINGPLATE
∆ m = 20 to 30 inchesFmax = 3 to 4 times Fy
∆el
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Applications of Base Isolation1st application in New Zealand in 1974
1st US application in 1984
1st Japanese application in 1985
US - 80 buildings and 150 bridges
Japan - 1000 buildings and 500 bridges
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
San Francisco Airport International TerminalWorld’s Largest Isolated Building
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, LahoreBenefits of Seismic Isolation Retrofit
Work maybe Confined to Basement
Building Can Continue to be Occupied
Often the Most Economic Solution
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Base Isolation and Blast LoadsDoes the use of base isolation help or hurt the response of a building subjected to blast loads
Global impact
Local effects
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Base isolation provides the highest level of protection – “operational” - after a major earthquake
Base isolation has significant benefits for the earthquake protection of historic structures
Base isolated buildings are capable of resisting GSA blast loads and their ability to move reduces the overall impact of the blast force on the building.
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Does Isolation Work?
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Isolated
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Conventional
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Kobe Earthquake Force
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
1994 Northridge Earthquake 31 Hospitals had significant damage
9 Hospitals partially or fully evacuated
USC University Hospital – the first isolated hospital suffered no damage at all
Los Angeles County General Hospital less than 1 mile from the USC isolated hospital had $389 million in damage
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Isolated
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Conventional
National Park Service – Base Isolation and Blast Loads
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Northridge Earthquake Force
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
M
gx&&
1x
µ
ASEISMIC BASE ISOLATION SYSTEMS
1. Pure Friction (PF) System1. Pure Friction (PF) System
the simplest devicethe simplest devicelimits a maximum acceleration transmitted from the limits a maximum acceleration transmitted from the substructuresubstructuremay have an excessive defection or a residualmay have an excessive defection or a residualdeformationdeformationmay be used economically in the simple or smallmay be used economically in the simple or small--scale structurescale structure
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, LahoreAseismic Base Isolation Systems
RubberInner steel plate
Outer steel plateProtective rubber
Flange
gx&&
1x
M
K
C
2. Rubber Bearing (RB) System2. Rubber Bearing (RB) System
widely studied and used over the world widely studied and used over the world consists of alternating layers of rubber and steel plateconsists of alternating layers of rubber and steel plateparallel action of spring and dashpotparallel action of spring and dashpotmainly shifts natural period of the isolated structuremainly shifts natural period of the isolated structure
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
3. Lead Rubber Bearing (LRB) System3. Lead Rubber Bearing (LRB) System
widely studied and used over the worldwidely studied and used over the worldadditional energy dissipation by a central lead coreadditional energy dissipation by a central lead corebilinear model of characteristic curve is usedbilinear model of characteristic curve is used
RubberInner steel plate
Outer steel plateProtective rubber
Flange
Central lead coregx&&
1x
M
Keff
Ceq
Aseismic Base Isolation Systems
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
4. Resilient Friction Base Isolation (R4. Resilient Friction Base Isolation (R--FBI) SystemFBI) System
parallel action of resiliency of rubber and frictionparallel action of resiliency of rubber and frictionof Teflon coated plateof Teflon coated platehas a recovering force by rubber after slidinghas a recovering force by rubber after sliding
gx&&
1x
µ
M
K
C
Cover plate
Central rubber core
Peripheral rubber core
Rubber cover
Connecting plate
Sliding ring
Aseismic Base Isolation Systems
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
5. 5. ElectiriciteElectiricite De France (EDF) SystemDe France (EDF) System
consists of the elastomeric bearing and the frictionconsists of the elastomeric bearing and the frictionplate in seriesplate in seriesbehaves as a RB unit during a lowbehaves as a RB unit during a low--intensityintensityearthquakeearthquakemay have a residual deformation during a highmay have a residual deformation during a high--intensity earthquakeintensity earthquake
`
gx&&
2x
µM
K
C
1x
Reinforced neoprene pad
Friction plates
Stud anchor
Aseismic Base Isolation Systems
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, LahoreSeismic Base Isolation
Structural Dynamics & Vibration Control Lab., KAIST, KoreaStructural Dynamics & Vibration Control Lab., KAIST, Korea
Prof. Dr. Zahid A. Siddiqi, UET, Lahore
Time(sec)
Acc
eler
atio
n(g)
Frequency(Hz)
Mag
nitu
de
0 10 20 30 40-0.4
-0.2
0
0.2
0.4
El Centro
0 2 4 6 8 100
40
80
120
160
200
El Centro
0 1 2 3 4 50
0.5
1
1.5
2
2.5
Mexico City
0 15 30 45 60 75-0.2
-0.1
0
0.1
0.2
Mexico City
0 2 4 6 8 100
100
200
300
400
San Fernando
0 10 20 30 40-1.5
-1
-0.5
0
0.5
1
San Fernando
Sensitivity Analysis
SETTLEMENTS OF FOUNDATIONSSETTLEMENTS OF FOUNDATIONS
NO SETTLEMENT * TOTAL SETTLEMENT * DIFFERENTIAL SETTLEMENTNO SETTLEMENT * TOTAL SETTLEMENT * DIFFERENTIAL SETTLEMENTUniform settlement is usually of little consequence in a buildinUniform settlement is usually of little consequence in a building, but differential g, but differential
settlement can cause severe structural damagesettlement can cause severe structural damage
Tieback InstallationTieback Installation
Rotary Drill HoleRotary Drill Hole
Insert & Grout TendonsInsert & Grout Tendons
Tendons Stressed & AnchoredTendons Stressed & Anchored
BracingBracing
CrosslotCrosslot
RackersRackers
TiebacksTiebacks
Watertight Barrier WallsWatertight Barrier Walls
Keep Water OutKeep Water OutBarrier must reach an Barrier must reach an impervious strataimpervious strataTypesTypes–– Slurry WallsSlurry Walls–– Sheeting w/ pumpsSheeting w/ pumps
Must resist hydrostatic Must resist hydrostatic pressure pressure
Much Has Been Accomplished …Modern Ductile Details
• Initial Failure at ~0.6g
Courtesy of Caltrans
Older Brittle Details• Total Failure at ~0.2g• Retrofit Priority
Courtesy of Caltrans
Example: Applied Engr. ResearchExperimental Validation & Refinement of “Zipper Frame System” Concept
Courtesy of Prof. Roberto Leon, Georgia Tech.
Behavior controlled by brace buckling -system is unable to redistribute forcesefficiently
∆
VV
∆∆
V
Conventional Steel Braced Frame
∆∆∆
VVV
Zipper struts tie all brace-to-beam intersection points together and force all the compression braces to buckle simultaneously (Khatib, Mahin, Pister)
Zipper Frame
Weakens After First Yield
Strengthens After First Yield
YieldYield
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