Structural Response to Tsunami Loading The Rationale for Vertical Evacuation

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Structural Response to Tsunami LoadingThe
Rationale for Vertical Evacuation

• Laura Kong
• IOC ITIC
• Ian Robertson
• University of Hawaii at Manoa
• Harry Yeh
• Oregon State University

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Topics

• Pilot Study on current code tsunami design
• Lessons from Indian Ocean Tsunami
• FEMA ATC-64 Project
• NEESR-SG Proposal - Performance Based Tsunami
  Engineering, PBTE

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Seismic/Tsunami Construction,Phase I A Pilot
Study

• Initiated and funded by Washington State
  Emergency Management Division
• One year pilot study
• Joint effort by OSU and UH Manoa
• Culminating in development of proposal for future
  design guideline development

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Project Scope

1. Review current codes for tsunami loading
   provisions
2. Evaluate prototype structures for seismic/tsunami
   design
3. Review past tsunami damage

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1. Review Current Codes

• City and County of Honolulu Building Code (CCH)
• FEMA Coastal Construction Manual (FEMA CCM)
• Dames and Moore 1980
• 1997 Uniform Building Code (UBC 97)
• 2000 and 2003 International Building Code (IBC)
• ASCE 7-98 and ASCE 7-02 (ASCE 7)

• Provisions of codes
• Predominantly intended for residential
  construction or small scale structures.
• Code provisions developed for storm wave
  conditions, storm surge and river flooding.
• CCH and FEMA CCM add reference to tsunami
  conditions.

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Tsunamis covered in CCH and FEMA CCM

• FEMA CCM states that Tsunami loads on
  residential buildings may be calculated in the
  same fashion as other flood loads when the
  tsunami forms a borelike wave, the flood
  velocities are substantially higher.
• Conclusion of FEMA CCM Tsunami loads are too
  great and not feasible or practical to design
  normal structures to withstand these loads.
• (Note that this report was intended for use in
  low-rise residential construction)

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Tsunami Design Vs. Design Stillwater Depth

• FEMA CCM Section 11.7 Figure 11-16

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Design Considerations

• Hydraulic Lateral Forces
• full structure
• individual elements
• Impact Force
• floating debris
• Buoyancy Force
• Scour

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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Design Considerations

• Hydraulic Lateral Forces
• Hydrostatic
• Surge Force
• Breaking Wave Force
• Hydrodynamic
• Impact Force

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• Impact Force (CCH)
• at

where W 1000 lbs
Example Wood Steel RC
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Loading Combinations

• If walls not designed to break away
• Hydrostatic force on building elevation,
  plus hydrodynamic force on sides of structure,
  plus impact force.
• Breaking wave force on building elevation,
  plus hydrodynamic force on sides of structure,
  plus impact force.
• Surge force on building elevation,
  plus hydrodynamic force on sides of
  structure, plus impact
  force.
• Codes call for break-away walls
• In-fill wall capacity min. 10 psf and max. 20
  psf

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2. Prototype Buildings

• Seismic and Wind Design of
• Concrete Buildings.
• S.K. Ghosh and David A. Fanella
• 2003.

• Includes examples of typical concrete building
  design for Gravity, Wind and Seismic loading.
• Considers various wind exposure conditions and
  seismic design categories.
• Shows sample column, beam and shear wall design.

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Building 1 MRF and Dual System
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Building 2 Building Frame System
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Building 3 Bearing Wall System
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Building Design Criteria
Seismic and Wind Design Criteria
SDC Seismic Design Category (Seismic Hazard and
Soil Type)
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Building 1 Results

• Base Shear
• Non-break-away walls

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Building 1 Results

• Base Shear
• Break-away walls

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Building 1Forces on Structural Members

• Column C4 Shear Wall

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Building 1 Results

• Column Design Forces
• Code Tsunami Forces compared with Seismic Design

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Building 1 Results

• Column - Actual Strength
• Code Tsunami Forces vs As-Built Strength

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Building 1 Results

• Shear Wall - Actual Strength
• Code Tsunami Forces vs As-Built Strength

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Building 1 Results

• Shear Wall - Actual Strength
• Recommended Tsunami Forces vs As-Built Strength

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Conclusions

1. The USA building codes do not adequately address
   the flow velocity and subsequent structural
   loading during a tsunami. Experimental
   validation of the velocity, flow depth and
   loading expressions is needed.
2. The tsunami forces often exceed the design forces
   based on wind and seismic conditions
3. However, a review of three typical prototype
   buildings indicated that the as-built capacity of
   individual members is often adequate for the
   tsunami loads
4. The prototype building with moment-resisting
   frame or dual system was able to resist the
   tsunami forces

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Conclusions (cont.)

1. The prototype building with shear wall-frame
   system was able to resist the tsunami forces,
   however individual shear walls perpendicular to
   the tsunami flow may fail and lead to progressive
   collapse of the building
2. The prototype building with bearing wall system
   was not able to resist the tsunami loads and is
   not recommended for construction in tsunami
   inundation zones
3. A structure must resist both the initial
   earthquake ground shaking, as well as the
   subsequent tsunami loads, so that vertical
   evacuation can be recommended to levels above the
   expected maximum flow

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Recommendations

1. Analytical Modeling and experimental verification
   of tsunami flow depth and velocity should be
   performed using a large-scale wave tank
2. Hydrodynamic force and impact force are the most
   probable during a tsunami.
3. Wave tank studies should also be performed to
   verify hydrodynamic loading due to tsunami flow,
   and impact due to waterborne debris
4. Based on these studies the code tsunami loading
   equations should be revised.

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Recommendations (cont)

1. All non-structural walls at the lower levels
   should be designed to break-away during a tsunami
   event
2. Open moment frame or dual systems are recommended
   for lateral framing of buildings in tsunami
   inundation areas
3. Buildings in tsunami inundation areas should
   avoid the use of bearing walls or large
   structural walls perpendicular to the anticipated
   tsunami flow
4. Structures must be able to resist the local
   source earthquake, which often precedes the
   tsunami, with limited structural damage

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Final Recommendation

• Vertical evacuation in multi-story reinforced
  concrete (and structural steel) buildings is an
  appropriate policy for
• All near-source tsunamis
• Remote-source tsunamis in densely populated areas
  where horizontal evacuation is not feasible

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FEMA ATC-64 project

• Initiated by FEMA as follow-on to Pilot Study
• 400,000 funding for 2-year effort
• Development of Design and Construction Guidance
  for Special Facilities for Vertical Evacuation
  from Tsunami
• Applied Technology Council Project Team
• Chris Rojahn Project Executive Director
• Steven Baldridge Project Technical Director

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NEESR-SGPerformance Based Tsunami Engineering,
PBTE

• Proposal to the NSF George E. Brown Network for
  Earthquake Engineering Simulation, NEES
• Small Group project, 1,600,000 over 4-years
• UH, Princeton, Oregon State University
• Development of Performance Based Tsunami
  Engineering
• Will include numerous tsunami wave basin
  experiments to validate run-up and 3-D RANS
  modeling, develop improved loading time-history,
  scour modeling and structural response.
• Result in code adoptable tsunami design provisions

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Thank-you