base isolation and blast loading
DESCRIPTION
EarthquakesWind Blast / Progressive collapseGreen Engineering Sensitivity to Historic Preservation IssuesTRANSCRIPT
National Park Service – Base Isolation and Blast Loads
Base Isolation Technology and
Blast Loading
Dr. Ronald L. Mayes – SGH Dr. Eve Hinman – HCE
National Park Service – Base Isolation and Blast Loads
Engineering Design Issues
Earthquakes Wind Blast / Progressive collapse Green Engineering Sensitivity to Historic Preservation Issues
National Park Service – Base Isolation and Blast Loads
Innovations in Earthquake Engineering
Base 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
Earthquakes can be Catastrophic and Very Expensive
Loma Prieta – $7 Billion $450 Million per Second
Northridge - $30 Billion $2 billion per second!
Kobe - $150 - $200 Billion $7.5 billion per second!!
National Park Service – Base Isolation and Blast Loads
Duration is Magnitude Dependent
1906 San Francisco 8.3 1 min. 1964 Alaska 8.4 4 min. 1989 Loma Prieta 7.1 15 sec. 1994 Northridge 6.7 12 sec. 1995 Kobe 7.1 15 sec.
Loma Prieta, Northridge and Kobe
were not the Big Ones!
National Park Service – Base Isolation and Blast Loads
Current Design CodesExpected Performance
“These design requirements primarily
are intended to safeguard against
major failures and loss of life, NOT to
limit damage, maintain functions, or
provide for easy repairs.”
National Park Service – Base Isolation and Blast Loads
Performance Based Design (PBD)
Owner chooses desired performance Reduce business interruption Reduce damage costs
National Park Service – Base Isolation and Blast Loads
Performance Based Design Documents
Vision 2000Vision 2000 FEMA 356/273FEMA 356/273 ATC 40ATC 40 FEMA 310FEMA 310
National Park Service – Base Isolation and Blast Loads
Operational(Negligible Damage)
Immediate Occupancy(Light Damage)
Life Safety(Moderate Damage)
Collapse Prevention(Severe Damage)
Collapse(Complete Damage)
Damage States & Performance Level Thresholds
National Park Service – Base Isolation and Blast Loads
Base Isolation Technology
One 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
The Goals of Base Isolation
Protection of Life – Current Code Additional Benefits of Isolation
Protection 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
Ground Forces are amplified
by a factor of 3 to 4 at the
roof.
Conventional Structure
National Park Service – Base Isolation and Blast Loads
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
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
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
Friction Pendulum Bearing
SECTION
STAINLESS STEELCONCAVE SURFACE
SELF LUBRICATINGCOMPOSITE LINER
ARTICULATINGSLIDER
PLATECONCAVE
HOUSINGPLATE
National Park Service – Base Isolation and Blast Loads
Applications of Base Isolation
1st 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
US APPLICATIONS
55% Government 45% Private sector 55% New Buildings 45% Retrofit of Existing Buildings
National Park Service – Base Isolation and Blast Loads
US APPLICATIONS 12 Historic building retrofits 8 Hospitals 8 Emergency Operation Centers 7 Manufacturing Facilities 7 Computer Centers 6 University Buildings 6 Court Houses / Police Buildings 3 Laboratories 3 Library / Museums 2 Residences 10 Miscellaneous – Tanks/Labs /Airports /Church etc
National Park Service – Base Isolation and Blast Loads
San Francisco Airport International Terminal
World’s Largest Isolated Building
National Park Service – Base Isolation and Blast Loads
Benefits 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
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
Base Isolation and Blast Loads
Does 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
Threat Definition ISC Security Criteria High Protection
Facility 500 lb weapon
curbside 20 foot standoff
National Park Service – Base Isolation and Blast Loads
Blast Base Shear
US Department of State standards
Seismic Base Shear Governs
National Park Service – Base Isolation and Blast Loads
Air-Blast Effects Direct Air-blast Effects
Local Global
Collateral Effects Progressive Collapse
Time Regime Seconds vs.
Milliseconds
National Park Service – Base Isolation and Blast Loads
Blast Base Shear is a function of:
Total Impulse Period of Vibration Displacement
Ductility
National Park Service – Base Isolation and Blast Loads
Total Impulse Calculation Weapon Size Standoff Building Dimensions CONWEP
National Park Service – Base Isolation and Blast Loads
Kinetic Energy = Strain Energy = Area under F – D Curve
Force
Deflection
National Park Service – Base Isolation and Blast Loads
Force
Deflection
Fy =___2 I___
2T (2 -1)0.5
Fy
National Park Service – Base Isolation and Blast Loads
Yield Level Fy = 0.03W to 0.07W
Yield Displacement = 0 to 0.5 inches
Force
Deflection
Fy
Dy
National Park Service – Base Isolation and Blast Loads
Maximum Displacement = 20 to 36 inches
Maximum Force = 0.15W to 0.25W
Force
DeflectionDmax
Fmax
National Park Service – Base Isolation and Blast Loads
Salt Lake City and County Building
High Risk GSA Building with 20 ft Standoff
Impulse load is 360 kip-sec. Yield Level of the isolators is 3100 kips Isolators displace less than 1 inch For a 10 inch movement in the isolators
the blast load could be 5 times greater
National Park Service – Base Isolation and Blast Loads
Oakland City Hall
High Risk GSA Building with 20 ft Standoff
Impulse load is 300 kip.-sec. Yield level of the isolators is 3060 kips Isolators displace less than 1 inch For a 10 inch movement in the isolators
the blast load could be 6 times greater
National Park Service – Base Isolation and Blast Loads
San Francisco City Hall
High Risk GSA Building with 20 ft Standoff
Impulse load is 480 kip.-sec. Yield level of isolators is 14,000 kips Isolators displace less than 1/4 inch For a 10 inch movement in the isolators
the blast load could be 18 times greater
National Park Service – Base Isolation and Blast Loads
Conclusions
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
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