Seismic Vulnerability Risk Assessment for Essential Structures in Clark County Nevada

1
Seismic Vulnerability Risk Assessment for
Essential Structures in Clark County Nevada

• Ronald L. Sack
• Tyson Day
• Arya Ebrahimpour
• Jared R. Keller
• Josh Baird

2
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.

3
Literature

• Design provisions
• NEHRP Recommended Provisions, ASCE-7, UBC, and
  IBC (2000, 2003)
• Evaluation tools
• ATC Reports, FEMA RVS Method, and HAZUS-MH
  Program (Levels 1, 2 3)
• Technical articles
• McCormack et al. (1997), Perry and ODonnell
  (2001), Hwang, et al. (2000), etc.

4
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/eart
  hquake/

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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)

6
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

7
Description of Model Building Types

• W1 Wood Light Frame
• W2 Wood Frames Commercial and Industrial
• S1 Steel Moment Frames
• S2 Steel Braced Frames
• S3 Steel Light Frames
• S4 Steel Frames with Concrete Shear Walls
• S5 Steel Frame with Infill Masonry Shear Walls
• C1 Concrete Moment Frames
• C2 Concrete Shear Wall Buildings
• C3 Concrete Frame with Infill Masonry Shear
  Walls
• PC1 Precast/Tilt-up Concrete Shear Wall
  Buildings
• PC2 Precast Concrete Frames
• RM1 Reinforced Masonry Bearing Wall Buildings
  with Flexible Diaphragms
• RM2 Reinforced Masonry Bearing Wall Buildings
  with Stiff Diaphragms
• URM Unreinforced Masonry Bearing Wall Buildings

8
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)

9
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.

10
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.

12
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

• Foundations consist of brick or concrete-spread
  footings.

13
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

14
Typical School

• Hal Smith Elementary School
• Find
• Address
• No. Stories
• Year Built
• Total Floor Area
• Building Name

15
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

18
Information Retrieval

• Building Type

19
Information Retrieval

• Building Type

20
Information Retrieval

• Total Floor Area
• From Plans

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Information Retrieval

• Total Floor Area
• Total 60,105 ft2

22
Hal Smith E.S.

• Address
• No. Stories
• Year Built
• Total Floor Area
• Building Name
• Falling Hazards
• Building Type
• Comments
• Code Used

23
Analysis Overview

• FEMA 154
• HAZUS-MH

24
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 communitys 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 lt 0.067g
• Moderate 0.067g lt Long Period (1.0 sec) SAR lt
  0.200g
• High 0.200g lt 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 structures 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 cut-off 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

32
HAZUS-MH Overview

• Hazards, USMulti-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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HAZUS-MH Overview
Demand-Capacity Curves
Structural Fragility Curves
Spectral Acceleration (gs)
Probability Distribution
34
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

35
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

36
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.

37
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)

39
ExampleFEMA
Since FAILS Therefore it will require
additional evaluation
40
ExampleHAZUS-MH
Hal Smith E.S.
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ExampleHAZUS-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

HAZUS Developed Long Period (1.0 sec) Contour Map
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ExampleHAZUS-MH

• Estimated Structural Damage
• Estimated Functionality

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ExampleComparison

• 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

44
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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