ASCE 7- STANDARD TSUNAMI CHAPTER

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ASCE 7‐ STANDARDTSUNAMI CHAPTER

Media Event

September 28, 2016

Portland, OR

Gary Chock, S.E., D.CE, F.SEI, D.M. ASCEStructural Engineer, Hawaii and California

Diplomate, Coastal Engineer, of the Academy of Coastal, Ocean, Port and Navigation Engineers ASCE Structural Engineering Institute Fellow

ASCE Distinguished Member

Yong Wei, Ph.D.Research Scientist, University of Washington - Joint Institute for the Study of the

Atmosphere and Ocean, & NOAA/Pacific Marine Environmental Laboratory

Dan Cox, Ph.D. Professor of Civil and Construction Engineering

Oregon State University

Designing Structures for Tsunami Resilience using the New Chapter

6 of ASCE 7-16

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Principal Topics

Introduction

Scope of the ASCE 7-16 tsunami provisions

Tsunami Risk Categories

Probabilistic Tsunami Design Zone Maps

Structural Design for Tsunami Effects

Vertical Evacuation Refuge Design

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A new Chapter 6 - Tsunami Loads and Effects for the ASCE 7-16 Standard has been approved, applicable to AK, WA, OR, CA, and HI .

Tsunami Provisions have been approved to be referenced in the IBC 2018

Final ASCE 7-16 Standard to be published at the beginning of 2017, in hardcopy and electronic digital versions.

State Building Codes would be adopting the IBC -2018 in ~2020

ASCE will be publishing a tsunami design guide in early 2017 with numerous design examples.

The Tsunami Resilient Provisions of ASCE

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Tsunami Disaster Resilience by Design

Without hazard maps and design requirements, there hasn’t been any consideration of tsunami hazard in the design of structures in the five western states.

ASCE 7-16 provides a means to effectively influence community resilience and the reliability of critical infrastructure in design. Many people can be saved in multi-story buildings, and many structures can be designed to withstand tsunami effects.

Maps and criteria in the ASCE 7 design standard are based on engineering risk analysis and reliability targets, rather than deterministic scenarios.

The ASCE 7 tsunami provisions apply to design for community planning and resilience before a tsunami event.

After a tsunami, it will have even more significance as a means to plan, site, and design what (and where) is appropriate and necessary in reconstruction, to enable communities to Building Back Better.

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Max Considered Tsunami, MCT and Tsunami Design Zone

The ASCE 7 Tsunami Loads and Effects Chapter is applicable only to the states of Alaska, Washington, Oregon, California, and Hawaii, which are tsunami-prone regions that have quantifiable hazards.

The Maximum Considered Tsunami (MCT) has a 2% probability of being exceeded in a 50-year period, or a ~2500 year average return period.

The Maximum Considered Tsunami is the design basis event, characterized by the inundation depths and flow velocities at the stages of in-flow and outflow most critical to the structure.

The Tsunami Design Zone is the area vulnerable to being flooded or inundated by the Maximum Considered Tsunami. The runup for this hazard probability is used to define a Tsunami Design Zone map.

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Principal Topics

Introduction






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Fluid-Structure Interaction

Structural Loading

Structural Response

Scour and Erosion

Consequences(Life and economic losses)

Warning and Evacuation Capability

Tsunami inundationModeling to Define Tsunami Design Zones

Sources and Frequency

Tsunami GenerationDistant and Local Subduction Zones

Open Ocean Propagation

Offshore Tsunami Amplitude

Loads and Effects incorporating Coastal, Hydraulic, Structural, and Geotechnical Engineering

Maps based onProbabilisticTsunami HazardAnalysis (PTHA)

StructuralReliabilityValidated

Societal Impact Assessment for the Five Western States by USGS

Tsunami-Resilient Engineering Subject Matter Incorporated in ASCE 7

Coastal Inundation and Flow Velocities

Performance by Risk Category

Seismic Source Assessment by USGS

Scope of ASCE 7

Chapter 6

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ASCE 7 Chapter 6Tsunami Loads and Effects

6.1 General Requirements

6.2-6.3 Definitions, Symbols and Notation

6.4 Tsunami Risk Categories

6.5 Analysis of Design Inundation Depth and Velocity

6.6 Inundation Depth and Flow Velocity Based on Runup

6.7 Inundation Depth and Flow Velocity Based on Site-Specific Probabilistic Tsunami Hazard Analysis

6.8 Structural Design Procedures for Tsunami Effects

6.9 Hydrostatic Loads

6.10 Hydrodynamic Loads

6.11 Debris Impact Loads

6.12 Foundation Design

6.13 Structural Countermeasures for Tsunami Loading

6.14 Tsunami Vertical Evacuation Refuge Structures

6.15 Designated Nonstructural Systems

6.16 Non-Building Structures

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Principal Topics

Introduction






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Risk Categories of Buildings and Other Structures per ASCE 7

Risk Category I Buildings and other structures that represent a low risk tohumans

Risk Category II All buildings and other structures except those listed inRisk Categories I, III, IV

Risk Category III Buildings and other structures, the failure of which couldpose a substantial risk to human life.Buildings and other structures with potential to cause asubstantial economic impact and/or mass disruption ofday-to-day civilian life in the event of failure.

Risk Category IV Buildings and other structures designated as essentialfacilitiesBuildings and other structures, the failure of which couldpose a substantial hazard to the community.

The scope of the tsunami provisions targets the performance of Risk Category III and IV buildings and critical infrastructureRisk Category III and IV structures within the TDZ are subject to the tsunami provisions

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Risk Category II Buildings – Determined by Local Code Adoption

The state or local government has the option to determine a threshold height for where tsunami-resilient design requirements for Risk Category II buildings shall apply in accordance with the state or local statute adopting the building code with tsunami-resilient requirements.

The threshold height would depend on the community’s tsunami hazard, tsunami response procedures, and whole community disaster resilience goals. Considerations of evacuation egress time from a local community would also be a consideration.

When evacuation travel times exceed the available time to tsunami arrival, there is a greater need for vertical evacuation into an ample number of nearby Category II buildings that are sufficiently tall.

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Principal Topics

Introduction






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M8.8 Maule Eq.Feb, 27, 2010

M9.0 Great East Japan Eq.Mar, 11, 2011

Subduction Zones

• Alaska-Aleutian

• Cascadia

• Kamchatka-Kuriles & Japan Trench

• Chile-Peru

Tsunami-genic Seismic Sources of Principal Relevance to the USA

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Relevance of Tohoku Lessons to the USA

Cascadia Subduction Zone is larger than the zone that ruptured in Tohoku

Cascadia Subduction Zone governs both the MCE and MCT

1700 Cascadia M9 Earthquake is only the most recent of numerous great earthquakes and tsunamis throughout the past 10,000 years.

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State Population at Direct Risk (USGS Lower-bound estimates)

Profile of Economic Assets and Critical Infrastructure

California 275,000 residents plus another 400,000 to 2,000,000 tourists; 840 miles of coastline

>$200 Billion plus 3 major airports (SFO, OAK, SAN) and 1 military port, 5 very large ports, 1 large port, 5 medium ports

Total resident population of area at immediate risk to post-tsunami impacts: 1,950,000

Oregon 25,000 residents plus another 55,000 tourists; 300 miles of coastline

$8.5 Billion plus essential facilities, 2 medium ports,1 fuel depot hub

Total resident population of area at immediate risk to post-tsunami impacts: 100,000

Washington 45,000 residents plus another 20,000 tourists; 160 miles of coastline

$4.5 Billion plus essential facilities, 1 military port, 2 very large ports, 1 large port, 3 medium ports


Hawaii ~200,000 residents plus another 175,000 or more tourists and approximately 1,000 buildings directly relating to the tourism industry; 750 miles of coastline

$40 Billion, plus 3 international airports, and 1 military port, 1 medium port, 4 other container ports, and 1 fuel refinery intake port, 3 regional power plants; 100 government buildings


Alaska 105,000 residents, plus highly seasonal visitor count; 6,600 miles of coastline

>$10 Billion plus International Airport’s fuel depot, 3 medium ports plus 9 other container ports; 55 ports total


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PTHA - Tsunami Design Zone

Subduction Zone Earthquake Sources are consistent with USGS Probabilistic Seismic Hazard model.

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RUNUP ELEVATION: Difference between the elevation of maximum tsunami inundation limit and the (NAVD-88) reference datum

INUNDATION DEPTH: The depth of design tsunami water level with respect to the grade plane at the structure

INUNDATION LIMIT: The horizontal inland distance from the shoreline inundated by the tsunami

Figure 6.2-1

Terminology

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Tsunami Design Geodatabase being hosted by ASCE on an electronic database

Probabilistic Subsidence Maps

PTHA Offshore Tsunami Amplitude and Predominant Period

Disaggregated source figures

Runup, or Inundation depth reference points for overwashedpeninsulas and/or islands to be presented in an electronic map

Tsunami Design Zones organized by state (all applicable areas in the five western states)

62 nondigital Tsunami Design Zone pdf maps for specific areas that are equivalent to the digital maps

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Tsunami Design Zone Map Coverage

State Dominated Sources Maps completed

WA Local 100%

OR Local 100%

AK Local 100% (maps not shown for coastlines with “bad” DEMs)

HI Distant 100%

CA Distant 100%

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PTHA Offshore Amplitudes Tsunami Inundation Modeling

Reconstruct disaggregated scenarios using a combination of “unit tsunami sources”: • Source location• Rupture area• Slip

Target of source reconstruction: PTHA offshore wave amplitudes•Reconstruct tsunami sources to match the offshore PTHA tsunami amplitudes

•Tsunami inundation modeling for reconstructed sources

Derive probabilistic TDZ maps using an envelop of inundation lines obtained from above steps

- Source disaggregation and selection

Courtesy of Thio et al. (2010)

- 2,475-year offshore tsunami amplitudes and wave period

Courtesy of Thio et al. (2010)

Procedure of Tsunami Design Zone (TDZ) Development

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West Pacific East Pacific

Methodology - NOAA Propagation Database of Tsunami Unit Sources

Tsunami unit source:• 100 km × 50 km• Placed along subduction zones and known tsunamigenic

faults• Aligned to fit known fault geometries• Tsunami propagation computed using shallow-water

equations with a grid resolution of 4 arc sec (~7.2 km)• Can be linearly combined for source magnitude > 7.5

Aleutian Trench: side view Aleutian Trench: Aerial view

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Amplitude (ft) 27Period – Ttsu (min) 20Longitude -124.5820Latitude 46.9000

Model Source(Average slip = 25.9 m)

Tsunami Design Zone: Ocean Shores and Westport, WA

Runup Height 8.23 ft (MHW)Runup Height 15.76 ft (NAVD88)Lat: 47.08000Long: 235.95500

Tsunami Design Zone: Seaside to Warrenton, OR

Amplitude (ft) 36Period – Ttsu (min) 19Longitude ‐124.2670Latitude 46.0570


Model Source(Average slip = 29.1 m)

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Amplitude (ft) 10Period – Ttsu (min) 32Longitude -121.9530Latitude 36.6920

PTHA Disaggregated Hazard

Model Source (avg. slip 41.0 m)Tsunami Design Zone

Monterey, CA


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Principal Topics

Introduction






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Structural Loads

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Tsunami Loads and Effects

Hydrostatic Forces (equations of the form ksρswgh) Unbalanced Lateral Forces at initial flooding Buoyant Uplift based on displaced volume Residual Water Surcharge Loads on Elevated Floors

Hydrodynamic Forces (equations of the form ½ ksρsw(hu2) Drag Forces – per drag coefficient Cd based on size and element Lateral Impulsive Forces of Tsunami Bores on Broad Walls: Factor of 1.5 Hydrodynamic Pressurization by Stagnated Flow – per Benoulli Shock pressure effect of entrapped bore

Waterborne Debris Impact Forces (flow speed and √k m) Poles, passenger vehicles, medium boulders always applied Shipping containers, boats if structure is in proximity to hazard zone Extraordinary impacts of ships only where in proximity to Risk Category III & IV

structures

Scour Effects (mostly prescriptive based on flow depth)

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29Minami Gamou Wastewater Treatment Plant - subjected to direct bore impact

SendaiBore Strike on R/C Structure

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SendaiBore Strike on R/C Structure

Video 1 Minami Gamou

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Velocity Analysis

Video rate of 30 fpsTime from Frame 260 to 316 = 1.87 sec.Distance between buildings = 12.2 mBore velocity = 12.2/1.87 = 6.5 m/sJump height approx. 5.5m over approx. 0.5m standing water

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NEESR – Development of Performance Based Tsunami Engineering, PBTE

Video 2 Wall Force-Pressure

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Minami Gamou Wastewater Treatment Plant - subjected to direct bore impact

Bore Strike on R/C Structure

Lidar Scan of deformed shape

Structural drawings obtained from the Wastewater Treatment Plant

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Types of Floating DebrisLogs and Shipping Containers

Power poles and tree trunks become floating logs

Shipping containers float even when fully loaded

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6.1 m x 2.4 m x 2.6 m and 2300 kg empty

Containers have 2 bottom rails and 2 top rails

Pendulum setup; longitudinal rails strike load cell(s)

ISO 20-ft Shipping Container

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Shipping Container Impact

Video 3 Shipping Container

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Aluminum and Acrylic Containers in Water

Hinsdale Wave Research Laboratory Container hits underwater load cell to measure the force

1/5 scale model containers of aluminum and acrylic

Guide wires controlled the trajectory

Column and load cell at top of photo

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Impact with Load Cell

In-air tests carried out with pendulum set-up for baseline

In-water impact filmed by submersible camera

Impact was on bottom plate to approximate longitudinal rail impact

In-air impact In-water impact

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Container Impact

Video 4 Container in Flume

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Side View

Video 5 Container Impact

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Principal Topics

Introduction






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Use of Designated Tsunami Evacuation Buildings

Designated evacuation building

KamaishiMerchant Marine Dormitory

All other buildings destroyed or totally

flooded

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Ocosta Elementary SchoolWestport, WashingtonAmerica's first tsunami vertical evacuation refuge structure

The gym is designed to be 30 feet above grade and 55 feet above sea level following earthquake-induced subsidence. Tsunami inundation depth is about 20 ft.

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New 100,000sf multi-story Marine Studies Initiative (MSI) facility will be a new building located at the Hatfield Marine Science Center, a research and teaching facility located in Tsunami Design Zone of Newport, Oregon.

Should be designed to meet or exceed ASCE 7-16 tsunami requirements, which will also allow it to provide a additional place of safety on its roof during a “MCT” tsunami (per ASCE 7, approximately 10 ft. of inundation depth), or greater.

Designing for Tsunami ResilienceHatfield Marine Science Center

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Basic Lessons for Design of Buildings from Past Tsunami and confirmed in Design Examples

It is feasible to design certain buildings to withstand tsunami events

Multi-story (and larger buildings) with robust structural systems can survive.

Seismic design has significant benefits to tsunami resistance of the lateral-force-resisting system.

Local structural components may need local “enhanced resistance”

Foundation system should consider uplift and scour effects particularly at corners.

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Summary

The ASCE 7 provisions constitute a comprehensive method for reliable tsunami structural resilience, making tsunamis a required consideration in planning, siting, and design of coastal structures in the five western states.

Probabilistic Tsunami Hazard Analysis is the basis for the development of 2475-yr MRI Tsunami Design Zone maps.

Specified design procedures are provided for all possible loading conditions

Coastal communities and cities are also encouraged to require tsunami design for taller Risk Category II buildings, in order to provide a greater number of taller buildings that will be life-safe and disaster-resilient, especially where horizontal egress inland to safe ground takes longer than the travel time of the tsunami.

ASCE will publish a companion Tsunami Design Manual in early 2017 providing background and examples demonstrating application of these new tsunami design provisions.

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The ASCE Tsunami Loads and Effects SubcommitteeInquiries to: Gary Chock, Chair, [email protected]

THANK YOU

Documents

ASCE 7- STANDARD TSUNAMI CHAPTER