structural response to tsunami loading the rationale for vertical evacuation

Structural Response to Tsunami Loading

The Rationale for Vertical Evacuation

Laura KongIOC ITIC

Ian RobertsonUniversity of Hawaii at Manoa

Harry YehOregon State University

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

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

Project Scope

1. Review current codes for tsunami loading provisions

2. Evaluate prototype structures for seismic/tsunami design

3. Review past tsunami damage

1. Review Current Codes

a. City and County of Honolulu Building Code (CCH)

b. FEMA Coastal Construction Manual (FEMA CCM)

c. Dames and Moore 1980

d. 1997 Uniform Building Code (UBC 97)

e. 2000 and 2003 International Building Code (IBC)

f. 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.

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)

Tsunamis covered in CCH and FEMA CCM

Tsunami Design Vs. Design Stillwater Depth

FEMA CCM: Section 11.7 Figure 11-16

Design Considerations

Hydraulic Lateral Forces– full structure – individual elements

Impact Force– floating debris

Buoyancy Force Scour

Design Considerations

Hydraulic Lateral Forces– Hydrostatic– Surge Force– Breaking Wave Force – Hydrodynamic

Impact Force

Impact Force (CCH)

attg

WVFi Δ

= sd

where W = 1000 lbs

t

VFi Δ

=31

Example: Wood Steel RC

VFi 31= VFi 62= VFi 310=

Wood 1.0 secSteel 0.5 secRC 0.1 sec

tΔ Values:

Loading Combinations

If walls not designed to break away:1. Hydrostatic force on building elevation,

plus hydrodynamic force on sides of structure, plus impact force.

2. Breaking wave force on building elevation, plus hydrodynamic force on sides of structure, plus impact force.

3. 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

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.

Building 1 – MRF and Dual System

Building 2 – Building Frame System

Building 3 – Bearing Wall System

Building Design Criteria

Seismic Wind Building Equiv. TsunamiSDC Speed Location Prone Location

A 145 Miami, FL Kauai, HIC 110 New York, NY Oahu & Maui, HI

D 85 San Francisco, CAWest Coast, US;

Hawaii, HI

E 85 Berkeley, CAWest Coast, US;

Hawaii, HI

SDC – Seismic Design Category (Seismic Hazard and Soil Type)

Seismic and Wind Design Criteria

Tsunami Design Criteria

3 Meter Flow Depth

5 Meter Flow Depth

10 Meter Flow Depth

Building 1 ResultsBase Shear Non-break-away walls

KEY SDC A SDC EADEQUATE WIND GOVERNS (145 mph) EQ GOVERNSMARGINAL Entire Structure Entire Structure

INADEQUATE Base Shear (kips) Base Shear (kips)Seismic Forces 291.10 --

N-S Seismic Forces -- 4,690.00E-W Seismic Forces -- 3,162.00N-S Wind Forces 1,493.50 512.70E-W Wind Forces 498.90 171.50

3 Meter Tsunami 6,280.00 6,280.005 Meter Tsunami 17,400.00 17,400.0010 Meter Tsunami 69,700.00 69,700.00


N-S Load Case 2

E-W Load Case 2

Building 1 ResultsBase Shear Break-away walls

KEY SDC A SDC EADEQUATE WIND GOVERNS (145 mph) EQ GOVERNSMARGINAL Entire Structure Entire Structure

INADEQUATE Base Shear (kips) Base Shear (kips)Seismic Forces 291.10 --

N-S Seismic Forces -- 4,690.00E-W Seismic Forces -- 3,162.00N-S Wind Forces 1,493.50 512.70E-W Wind Forces 498.90 171.50



N-S Load Case 1

E-W Load Case 1

Building 1Forces on Structural Members

Column C4 Shear Wall

Building 1 Results

KEYADEQUATE Max Axial N-S Max E-W Max N-S Max E-W Max MARGINAL SDC Force Bending Moment Bending Moment Shear Force Shear Force

INADEQUATE (kips) (ft-kips) (ft-kips) (kips) (kips)

*EQ C 1,507.64 117.82 117.82 21.82 21.82

3 Meter Tsunami C 1,362.76 121.52 121.52 51.08 51.085 Meter Tsunami C 1,362.76 197.93 197.93 83.82 83.8210 Meter Tsunami C 1,362.76 395.88 395.88 167.66 167.66

*EQ D 1,841.45 228.00 386.18 39.27 77.45

3 Meter Tsunami D 1,512.82 132.56 132.56 57.23 57.235 Meter Tsunami D 1,512.82 217.70 217.70 94.43 94.4310 Meter Tsunami D 1,512.82 435.44 435.44 188.86 188.86

*EQ E 2,124.00 273.82 658.91 58.91 140.73

3 Meter Tsunami E 1,641.11 139.37 139.37 62.41 62.415 Meter Tsunami E 1,641.11 229.36 229.36 103.18 103.1810 Meter Tsunami E 1,641.11 458.74 458.74 206.36 206.36

*Governing design of structure

Column

Column – Design ForcesCode Tsunami Forces compared with Seismic Design

Building 1 Results Column - Actual StrengthCode Tsunami Forces vs As-Built Strength

KEYADEQUATE Max Axial Max Bending Max ShearMARGINAL SDC Force Moment Capacity Strength

INADEQUATE (kips) (ft-kips) (kips)

*EQ C 1,507.64 503.00 115.96

3 Meter Tsunami C 1,362.76 121.52 51.085 Meter Tsunami C 1,362.76 197.93 83.8210 Meter Tsunami C 1,362.76 395.88 167.66

*EQ E 2,124.00 1,274.00 365.40

3 Meter Tsunami E 1,641.11 139.37 62.415 Meter Tsunami E 1,641.11 229.36 103.1810 Meter Tsunami E 1,641.11 458.74 206.36


As-Built Column

Building 1 Results Shear Wall - Actual StrengthCode Tsunami Forces vs As-Built Strength

KEYADEQUATE Max Axial E-W Max Bending Max ShearMARGINAL SDC Force Moment Capacity Strength


*EQ C 3,112.00 2,386.00 535.58

3 Meter Tsunami C 3,111.98 1,670.81 735.665 Meter Tsunami C 3,111.98 3,249.78 1,557.9310 Meter Tsunami C 3,111.98 8,194.21 3,654.17

*EQ D 4,471.00 7,482.00 1,181.89

3 Meter Tsunami D 3,604.43 1,669.01 748.285 Meter Tsunami D 3,604.43 3,245.03 1,586.6110 Meter Tsunami D 3,604.43 8,141.78 3,710.56

*EQ E 5,135.00 9,912.00 1,601.36

3 Meter Tsunami E 3,899.48 1,600.37 738.175 Meter Tsunami E 3,899.48 3,113.38 1,569.2010 Meter Tsunami E 3,899.48 7,726.59 3,644.41

As-Built Shear Wall


Building 1 Results Shear Wall - Actual StrengthRecommended Tsunami Forces vs As-Built Strength

KEYADEQUATE Max Axial E-W Max Bending Max ShearMARGINAL SDC Force Moment Capacity Strength


*EQ C 3,112.00 2,386.00 535.58

3 Meter Tsunami C 3,111.98 768.33 336.885 Meter Tsunami C 3,111.98 1,379.69 584.3210 Meter Tsunami C 3,111.98 2,759.42 1,168.66

*EQ E 5,135.00 9,912.00 1,601.36

3 Meter Tsunami E 3,899.48 734.34 337.615 Meter Tsunami E 3,899.48 1,281.97 576.6810 Meter Tsunami E 3,899.48 2,563.93 1,153.36


As-Built Shear Wall

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

Conclusions (cont.)

5. 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

6. 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

7. 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

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.

Recommendations (cont)

5. All non-structural walls at the lower levels should be designed to break-away during a tsunami event

6. Open moment frame or dual systems are recommended for lateral framing of buildings in tsunami inundation areas

7. Buildings in tsunami inundation areas should avoid the use of bearing walls or large structural walls perpendicular to the anticipated tsunami flow

8. Structures must be able to resist the local source earthquake, which often precedes the tsunami, with limited structural damage

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

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

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

HOTELWAIKIKI

Thank-you

structural response to tsunami loading the rationale for vertical evacuation

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