Transcript Slide 1

Seismic Vulnerability Risk
Assessment for Essential
Structures in Clark County
Nevada
Ronald L. Sack
Tyson Day
Arya Ebrahimpour
Jared R. Keller
Josh Baird
Scope of the Project
• Part of a larger project entitled “Earthquakes in
Southern Nevada – Uncovering Hazards and
Mitigating Risk.”
• The objectives are to:
– Perform risk assessment of the critical infrastructure
in Clark County, Nevada (65 Fire Stations, 18
Police Stations, 3 Hospitals, 277 Schools); and
– Develop a web- and GIS-based visualization
product for general public, planners, and emergency
response specialists.
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Literature
• Design provisions:
– NEHRP Recommended Provisions, ASCE-7,
UBC, and IBC (2000, 2003)
• Evaluation tools:
– ATC Reports, FEMA RVS Method, and HAZUSMH Program (Levels 1, 2 & 3)
• Technical articles
– McCormack et al. (1997), Perry and O’Donnell
(2001), Hwang, et al. (2000), etc.
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Tools, Sources, & Communications
• Evaluation tools selected:
– FEMA-154 and HAZUS-MH (Level 2)
• Sources of information
– Building plans, web sites (longitudes and latitudes,
addresses, etc.), CC Building Dept., CC School District,
and UNLV faculty and students.
• Communications
– Web-based bulletin board
– E-mail, telephone, mail, FAX, etc.
– Project website: http://www.isu.edu/engineer/earthquake/
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Remainder of the Presentation
• Josh Baird:
– Building Classifications
– Example of Building Data Retrieval
• Jared Keller:
– Overview of FEMA 154 and HAZUS-MH
– Example of Building Evaluation
– Running HAZUS (after the presentation)
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Building Classifications
• Using FEMA 154 - Rapid Visual Screening of
Buildings for Potential Seismic Hazards
– Federal Emergency Management Agency
– Data collection Forms
– Building classifications
• Explain Classifications
• Example of a typical building
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Description of Model Building Types
W1:
W2:
S1:
S2:
S3:
S4:
S5:
C1:
C2:
C3:
PC1:
PC2:
RM1:
RM2:
URM:
Wood Light Frame
Wood Frames Commercial and Industrial
Steel Moment Frames
Steel Braced Frames
Steel Light Frames
Steel Frames with Concrete Shear Walls
Steel Frame with Infill Masonry Shear Walls
Concrete Moment Frames
Concrete Shear Wall Buildings
Concrete Frame with Infill Masonry Shear Walls
Precast/Tilt-up Concrete Shear Wall Buildings
Precast Concrete Frames
Reinforced Masonry Bearing Wall Buildings with Flexible Diaphragms
Reinforced Masonry Bearing Wall Buildings with Stiff Diaphragms
Unreinforced Masonry Bearing Wall Buildings
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W2: Wood Frames, Commercial and Industrial
• Large apt.
complexes,
Commercial or
Industrial
structures
• Usually 1-3 stories
• 5,000 ft2 or more
• Few interior walls
(if any)
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W2: Wood Frames, Commercial and Industrial
• The floor and roof
framing consists of
wood or steel
trusses, glulam or
steel beams, and
wood posts or steel
columns.
• Lateral forces are
resisted by wood
diaphragms and
exterior stud walls.
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PC1: Precast/Tilt-up Concrete Shear Wall Buildings
• One or more stories
• Precast concrete
perimeter wall
panels cast on site
and tilted into place
• Steel plates provide
connections (#7)
• Lateral forces
resisted by the
precast concrete
perimeter wall
panels
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PC1: Precast/Tilt-up Concrete Shear Wall Buildings
• Wall panels may be
solid, or have large
window and door
openings.
• Foundations consist of
concrete-spread
footings or deep pile
foundations.
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RM1: Reinforced Masonry Bearing Wall Buildings
with Flexible Diaphragms
• Bearing walls that consist of
reinforced brick or concrete
block masonry (cmu)
• Wood floor and roof framing
consists of steel beams or open
web joists, steel girders and
steel columns (flexible)
• Lateral forces resisted by the
reinforced brick or concrete
block masonry shear walls
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•Foundations
consist of brick or
concrete-spread
footings.
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Information Retrieval
• Compiled List
– Addresses
• Plans (from website)
– Year Built
– No. of Stories
– UBC Code used
– Building Type
– Total Floor Area (If not exact, estimated)
• FEMA Data Form
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Typical School
• Hal Smith
Elementary School
• Find
– Address
– No. Stories
– Year Built
– Total Floor Area
– Building Name
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Information Retrieval
• Address
– From Compiled List
– 5150 East Desert Inn
Road, Las Vegas, NV,
89122
• No. Stories
– From Wall Elevations
– 15-20 feet / story
– 1 story
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Information Retrieval
• Year Built
– From Plans
– 1999
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Information Retrieval
• Code Used
– From Structural Drawings (usually)
– 1994 UBC
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Information Retrieval
• Building Type
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Information Retrieval
• Building Type
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Information Retrieval
• Total Floor Area
– From Plans
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Information Retrieval
• Total Floor Area
– Total = 60,105 ft2
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Hal Smith E.S.
•
•
•
•
•
•
•
•
Address
No. Stories
Year Built
Total Floor Area
Building Name
Falling Hazards
Building Type
Comments
– Code Used
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Analysis Overview
• FEMA 154
• HAZUS-MH
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FEMA-154 Overview
• Rapid Visual Screening (RVS) of Buildings for Potential
Seismic Hazards
• Developed by the Applied Technology Council of Redwood
City California under contract from the Federal Emergency
Management Agency (FEMA)
• Established a method for performing rapid on-site “sidewalk”
surveys of existing buildings without requiring structural
calculations
• Using statistical analysis, a “structural score” for a building is
developed; this score is then compared to a predetermined
“cut-off score”
• Buildings receiving a score lower than the “cut-off score”
are determined as a potential seismic risk
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FEMA-154 Uses
• Ranking a community’s seismic rehabilitation needs
• Design seismic mitigation programs
• Develop inventories of buildings for use in regional
earthquake damage and loss impact assessments
• Planning post earthquake building safety evaluations
• Developing building specific seismic vulnerability
information
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FEMA-154 Procedure Overview
• Planning:
– Selection of desired buildings to participate in the survey
– Determination of “cut-off” score
• The calculated final score is an estimate of the probability that the building
will collapse; therefore a “cut-off” score is used to establish desirable
seismic reliability
– A score of 3 implies that there is a 1 in 1000 chance that the building will
collapse
– A score of 2 implies that there is a 1 in 100 chance that the building will
collapse
• A higher “cut-off” value implies greater desired safety but increased
rehabilitation costs prior to an earthquake
• A lower “cut-off” value equates to increased seismic risk with lower
rehabilitation costs prior to an earthquake
• A “cut-off” score of 2.0 is suggested based present seismic design criteria;
therefore, for the purpose of this survey, a “cut-off” score of 2.0 will be
used
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FEMA-154 Procedure Overview
• Planning:
– Selection and Review of Data Collection Form
• There are three predefined seismicity regions, namely High, Moderate, and
Low)
• Seismicity regions are defined based upon either the short or long period
spectral acceleration response (SAR) for a given location
– Low:
Long Period (1.0 sec) SAR < 0.067g
– Moderate: 0.067g < Long Period (1.0 sec) SAR < 0.200g
– High:
0.200g < Long Period (1.0 sec) SAR
• Seismicity regions can be determined by using NEHRP developed
maps or the USGS web page
• A seismicity region of “High” will be used for this study
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FEMA-154 Procedure Overview
• Completing the Data Collection Form:
– Year built:
• Used to determine if the building was built before or after
significant changes to seismic design code were implemented
– Total Floor Area:
• Not directly used in calculating the structural score; however can be
useful in determining rehabilitation/replacement costs
– Building Sketches:
• Used to determine if any vertical or plan irregularities exist
• Can also aid in estimating total floor area
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FEMA-154 Procedure Overview
• Completing the Data Collection Form (Cont):
– Soil Type:
• The soil types are defined in accordance to NEHRP 1997
Provisions
• Used to determine the modified structural score if applicable since
buildings constructed on Hard Rock will behave differently than
those constructed on Soft Soil
• The basic structural scores presented in FEMA-154 were
developed for an assumed Soil Type B (Rock) in accordance with
the NEHRP 1997 Provisions
– Building Type:
• The building type is categorized into one of 15 classes based
upon the structure’s primary lateral-load-resisting system
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FEMA-154 Procedure Overview
• Obtaining the “Structural Score”
– The final “structural score” is determined by adding (or
subtracting) the various score modifiers from the “Basic
Structural Hazard Score”
• Completing the Analysis
– If the obtained final “structural score” is below the “cutoff” score the building will require additional evaluation
with the aid of a qualified structural engineer
– If the obtained final “structural score” is greater than the
“cut-off” score the building should perform well in a
seismic event
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FEMA-154 Advantages/Disadvantages
• Advantages:
– Simplicity
– Relatively low cost to gather the required field data
– Provides effective estimates for determining future emergency planning
or mitigation
– Effective screening process for detailed evaluations
• Disadvantages:
–
–
–
–
Generalized results for each building type
Pass/Fail results
Three pre-determined seismicity regions (lack of refinement)
Does not incorporate seismic event when determining the final
“structural score”
– Very conservative
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HAZUS-MH Overview
• Hazards, US—Multi-hazards
• Developed by the Federal Emergency Management
Agency (FEMA) by the National Institute of Building
Sciences (NIBS)
• Nationally applicable methodology for estimating
potential earthquake losses on a regional basis.
• Developed by a team of earthquake loss experts
composed of earth scientists, engineers, architects,
emergency planners, etc.
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Demand-Capacity Curves
Structural Fragility Curves
1.00
Probability
Spectral Acceleration (g’s)
HAZUS-MH Overview
Capacity Curve
PGA[C]
PGA[E]
S
0.75
M
0.50
E
C
0.25
PGA[M]
PGA[S]
SD[S]
SD[M]
SD[E]
SD[C]
Spectral Displacement (inches)
Spectral Displacement (inches)
te
n
C
om
pl
et
e
Ex
25%
siv
M
e
od
er
at
e
Sl
on
e
50%
ig
h
t
75%
N
Probability
100%
0%
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Probability Distribution
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HAZUS-MH Uses
• Anticipating the possible nature and scope of
emergency response needed to cope with an
earthquake related disaster
• Developing plans for recovery and reconstruction
following a disaster
• Mitigating the possible consequences of earthquakes
• Generate an estimate of the consequence to a city,
region, or location for a given earthquake with a
specified magnitude and location
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HAZUS-MH Overview
• Planning:
– Selection of buildings to analyze
– Selection of scenario seismic event
• Independent research
• Provided historic seismic events
• Select a location from a list of provided/known fault lines
– Determine desired level of analysis/results
• Structures
• Lifelines
• Economic/Social impact
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HAZUS-MH Overview
• Data Collection:
– Same as FEMA-154 with a few changes
• Year Built helps determine seismic design level (High, Moderate, or Low)
• Floor Area is used to calculate expected building damage both physically
as well as financially
– Additionally:
• Latitude and Longitude to adequately determine the ground response with
respect to a given seismic event
• Construction Quality: Inferior, Meets, or Superior to code
• Estimated building cost
• Occupancy load during different times of the day
• Shelter capacity
• Number of beds for hospitals or trucks for fire stations
• Back-up power
• Etc.
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HAZUS-MH Advantages/Disadvantages
• Advantages:
– Flexibility
– GIS platform
– Provide estimates of the loss of functionality or percent damage for a
given structure/facility
– Provides effective estimates for determining future emergency planning
or mitigation
– Incorporates seismic event when determining probabilities
• Disadvantages:
–
–
–
–
Complex data setup/collection (data manipulation)
Flexibility
Must perform a Level 2 analysis for competent results
Does not directly incorporate building characteristics such as soft
stories or vertical/plan irregularities
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Example
• Hal Smith Elementary School
– 5150 E. Desert Inn Rd
Lat:
36.1295
Long: -115.0637
– Year Built: 1999
– Building Type: RM1
– Design Code: UBC 1994
– Area: 60,105 ft2
– Plan Irregularities: Yes
– No. Stories: 1
– Vertical irregularities: No
– Soil Type: D (assumed)
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Example—FEMA
Since
1 .7  2 .0
FAILS
Therefore it will
require additional
evaluation
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Example—HAZUS-MH
Hal Smith E.S.
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Example—HAZUS-MH
• Seismic Event:
– Location of epicenter:
(36.290, -115.160)
– Fault name: Eglington
– Magnitude: 6.30
– Depth: 12 km
– Rupture Length: 12.94 km
– Rupture Orientation: 0.00°
– Attenuation Function:
WUS Shallow Crustal
Event-Extension
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*
HAZUS Developed Long Period (1.0 sec)
Contour Map
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Example—HAZUS-MH
Estimated Structural Damage:
Name
Hal Smith E.S. (259)
None
Slight
Moderate
Extensive
Complete
72.30%
14.60%
10.90%
2.20%
0.10%
e
C
om
pl
et
e
siv
te
n
Ex
M
od
er
t
ig
h
25%
at
e
50%
Sl
Probability
75%
N
on
e
100%
0%
Estimated Functionality
Name
@ Day 1
@ Day 3
@ Day 7
@ Day 14
@ Day 30
@ Day 90
Hal Smith E.S. (259)
72.20%
72.60%
86.40%
86.80%
97.70%
98.80%
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Example—Comparison
• FEMA-154
– Ranks the building as a potential hazard
– With a final score of 1.7 the probability of collapse is 2%
• HAZUS-MH
– Verifies that the high seismicity FEMA region is
appropriate
– Demonstrates that significant damage is possible
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Project Update
• Building Analysis
– 20 of 65 Fire Stations
– 3 of 18 Police Stations
– 3 of 3 Hospitals
– 73 of 187 Elementary Schools
– 0 of 51 Middle Schools
– 14 of 39 High Schools
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Issues
• Seismic Event
– What is an appropriate event?
– What is a likely event?
•
•
•
•
Magnitude
Epicenter
Depth
etc.
• Data Entry
– Database manipulation
– Software compatibility
– Manual entry
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Proposed Project Uses
• FEMA-154 Results:
– Develop a list of potentially hazardous buildings
• HAZUS-MH Results:
– Estimate regions that are more susceptible to seismic events
– Estimate loss of functionality for specific buildings
• Overall
– Develop a mitigation plan for seismic rehabilitations
– Develop a list of buildings that may be used as shelters
– Develop a better understanding of building behavior for a given
building type (RM1, PC1, etc)
– Develop a contingency plans for emergency response
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