Earthquakes and Data Centers

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Earthquakes and Data Centers

Andrew W. Taylor, Ph.D., S.E., FACI

7x24 Exchange Fall Symposium

September 11, 2013 Hilton Bellevue

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Earthquakes and Data Centers

3 September 11, 2013

Cascadia Earthquake Sources

Figure Credit: Craig Weaver, Pacific Northwest Coordinator, National Earthquake Program, United States Geological Survey

Figure Credit: Craig Weaver, Pacific Northwest Coordinator, National Earthquake Program, United States Geological Survey Seattle Fault

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Figure Credit: Craig Weaver, Pacific Northwest Coordinator, National Earthquake Program, United States Geological Survey Shallow Crustal Faults

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Average return interval 300 to 600 years Last 4 events: 710, 1150, 1500 and 1700

Last megathrust event: January 26,1700, Magnitude 8.7 to 9.2

Megathrust Events in the Pacific Northwest

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Richter Magnitude: Not used by engineers for design. Richter Magnitude only describes the energy released by an earthquake, not the ground shaking at a particular building site

“Seismic Zones”: The building code stopped using seismic zones in 2000. The Seattle area was in “Zone 3”, but this designation is no longer in the code, or accepted by building officials.

Seismic Hazard Maps: These are “contour maps” that show ground shaking intensity for any location in the United States. The maps provide a much more accurate characterization of seismic hazard than the old “seismic zone” system.

Engineering Coefficients for Design

“Seismic Zones” no longer exist in the building code. Earthquake design coefficients are now obtained from USGS maps.

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Effects of Earthquakes on Buildings

Fundamental Approach -0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0 5 10 15 20 25 Time, seconds A c c e le ra ti o n , g

a

_max

F = M

x

a

Max EQ Force = Building mass x a

_max

?

Analyzing Earthquake Effects

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-0.25 -0.20 -0.15 -0.10 -0.05 0.00 0.05 0.10 0.15 0.20 0.25 0 5 10 15 20 25 Time, seconds A c c e le ra ti o n , g

a

_max

Max EQ Force = Building mass x a

_max

?

F = M

x

a

F = Mxa would be the right

answer only if the building were completely rigid, and elastic… Analyzing Earthquake Effects on Structures

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Earthquake engineering is more complicated

than F = Mxa_max because seismic design must

account for

1. Dynamic response of the flexible building - Distribution of stiffness

- Distribution of mass

- Multiple modes of vibration 2. Inelastic response of the building

- Yielding - Cracking - Friction

Both structural and nonstructural systems are damaged by racking of the structural frame:

Shear Walls Exterior Cladding & Windows

Columns Interior Partitions

Beams Doors

Cross Braces MEP Systems

Foundations HVAC Systems

UPS Systems Fire Suppression Interstory Drift (Structural Racking) What Causes Earthquake Damage?

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Cracking

Photos: Andy Taylor/NIST

What Causes Earthquake Damage?

Cause damage to non-structural components: Equipment Racks (tipping)

Generators, Chillers, Compressors, Pumps Battery Racks

Suspended Ceilings, Light Fixtures Raised Floors

Furniture and Cabinets Elevators

Accelerations

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0.54g

0.45g

0.36g

0.30g

Examples of Floor Accelerations

0.65g

0.24g

Figure Credit: FEMA, courtesy of Wiss, Janney, Elstner Associates

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Mechanical System - 1971 San Fernando Earthquake What Causes Earthquake Damage?

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Retail Stock - 1971 San Fernando Earthquake What Causes Earthquake Damage?

Olive View Medical Center Story •1971 San Fernando earthquake •1994 Northridge earthquake

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1971 San Fernando earthquake Olive View Medical Center Story

1994 Northridge earthquake Olive View Medical Center Story

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Fire sprinkler pipe broken 1994 Northridge earthquake Olive View Medical Center Story

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The current U.S. building code is the 2012

International Building Code, and ASCE 7-10.

The general goal of the code is to preserve the life safety function of a building: prevent injuries and allow safe egress from the structure.

The building code does not generally provide for continued functionality of a building, or even

reparability. For certain important structures, extra strength is provided, and structural racking is

limited.

What Are the Goals of the Building Code?

The Seismic Importance Factor I_e_{, is based on Risk}

Category. It is applied to earthquake design forces.

Risk Category I

e

I or II – Normal Hazard 1.0 III – High Hazard 1.25 IV – Essential Facility 1.5

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The maximum allowed story drift, _∆_a, is reduced for

higher risk structures

Risk Category Relative_∆a I or II – Normal Hazard 100 %

III – High Hazard 80 % IV – Essential Facility 60 %

What Are the Goals of the Building Code?

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Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Performance Based Seismic Design

Performance Based Seismic Design (PBSD) is an approach to earthquake design of facilities that

targets specific performance goals in specific “sizes” of earthquakes. Operational Immediate Occupancy Life Safety Collapse Prevention Frequent 43 years Occasional 72 years Rare 475 years Very Rare

Seismic Performance Goal

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Detailed Performance Goals for Each System

Operational Level Immediate Occupancy Level Life Safety Level Collapse Prevention Level Overall Damage Very Light Light Moderate Severe Personnel Safety No injuries Minor injuries Minor injuries Major injuries or deaths Structural Frame Minor or no damage to structural frame. Since repair is

not required, operations are not interrupted.

Minor, repairable damage to structural frame. Does not interfere with immediate use, but may interfere with long-term use.

Structural frame is permanently damaged and may not be repairable.

Structural frame is near collapse

Cladding Little or no cladding damage. Operations not interrupted for repair.

Minor cladding damage. Does not interfere with immediate operations, but may require future repair or replacement

Damage to cladding, but cladding remains on building. Cladding may have to be replaced.

Extensive loss of cladding

Windows No window damage Minor or no window damage A few windows may be broken Extensive broken windows

Doors No jamming of doors. Some doors jammed. Requires immediate repair.

Some doors jammed. No exits blocked.

Extensive jamming of doors and blocking of exits

Walls Little or no damage to walls. Operations not interrupted for repair.

Minor damage to walls. Requires repair in future

Extensive damage to walls, many not repairable

Mechanical and Electrical Systems

No damage to mechanical and electrical systems. Operations continue uninterrupted. Power and utilities available from auxiliary sources.

Minor damage of mechanical and electrical systems. Repairable in 24 hours or less if repair services are available. Power and utilities may be unavailable.

Moderate damage of mechanical and electrical systems. May not be repairable

Extensive damage of mechanical and electrical systems, not repairable

Elevators Elevators functional Moderate damage of elevators. May not be functional for several days, if repair services are not available

Extensive damage of elevators, may be repairable

Extensive damage of elevators, not repairable

Computers and Data Storage Fully functional. No loss of data. Minor damage, requiring repairs. Data may be lost. Down time depends on availability of repair services

Extensive damage, may not be repairable

Extensive damage, not repairable

Sensitive Equipment No damage to sensitive equipment Moderate damage, requiring repairs. Experiments lost. Down time depends on availability of parts and repair services.

Extensive damage, not repairable Extensive damage, not repairable Operational Immediate Occupancy Life Safety Collapse Prevention Frequent 43 years Occasional 72 years Rare 475 years Very Rare 975 years

Seismic Performance Goal

CUP Labs

Corporate

HeadquartersPed Bridge Corporate Headquarters Corporate

Headquarters

Warehouse

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Practical Considerations for Design

Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Structural Rehab for “Operational” Performance •Modifying an “ordinary” structure to achieve

“Operational” performance in a code-level earthquake is possible, but it is challenging and expensive.

•Similarly, modifying part of an existing “ordinary” structure to create an “Operational” data center usually requires structural and system modifications outside the footprint of the data center.

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Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Preservation of Safety Systems

ASCE 7-10, 13.1.3 – Non-structural components All components must be assigned an Importance

Factor I_p= 1.5 if

• “The component is required to function for life-safety purposes after an earthquake, including fire

protection sprinkler systems and egress stairways.” • The component is required for continuous operation of a Risk Category IV structure

• Component is related to a high-hazard material

Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Anchoring Equipment Racks

• Fastest, easiest, is anchor rods to concrete floor • Unistrut grid on concrete floor provides for future flexibility without concrete drilling

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Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Anchoring Equipment Racks

• For very heavy equipment, consider independent support on a steel frame.

Figure Credit: FEMA

Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

“The 400 Pound Rule” ASCE 7-10, Section 13.1.4

Mechanical and electrical components: structural engineering design of seismic bracing is not required in a high Seismic Design Category (SDC D, E, F) if

a) Weight _≤ 400 lbs., mass center _≤4 ft. above floor

b) Weight ≤ 20 lbs., mass center at any height

c) Weight _≤ 5 lbs./ft. (pipes, conduits), any height

c) Importance factor = 1.0

Technically, all other M & E components require

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Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Raised Access Floors

Two types of raised access floors defined in code: ASCE 7-10,13.5.7.1 = “Ordinary” Access Floor ASCE 7-10,13.5.7.2 = “Special” Access Floor In high Seismic Design Categories (SDC D, E, F) recommend specifying only Special Access Floors

Make explicit choices about how

we want a building to behave in a

specific “size” of earthquake

Seismic Qualification of MEP Equipment

ASCE 7-10, 13.2.1 – Contains requirements for seismic qualification of mechanical and electrical

components with importance factor I_p > 1.0, by

a) Engineering analysis

b) Qualification testing on a shake table

c) “Experience data” (i.e., documented performance in a previous earthquake).

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Trademark Attribution

The KPFF logo is a registered trademark of KPFF Consulting Engineers, in the United States and/or other jurisdictions. Other names used in this presentation are for identification purposes only and may be trademarks of their respective owners.