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Observations and Lessons on Earthquake and Tsunami Risk Mitigation in Padang, Indonesia

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Title: Observations and Lessons on Earthquake and Tsunami Risk Mitigation in Padang, Indonesia


1
Observations and Lessons on Earthquake and
Tsunami Risk Mitigation in Padang, Indonesia
  • Nick Alexander, Degenkolb Engineers
  • Veronica Cedillos, GeoHazards International
  • Louise Comfort, University of Pittsburgh

2
Reconnaissance Team Members
  • EERI Team
  • Deierlein, Alexander, Cedillos, Hausler,
    Henderson, Comfort, Hart, Rudianto, Wijanto,
    Wood.
  • Other US Participants
  • Mooney McGarr, USGS
  • Franco, DiBarnaba, Sandoval
  • Kizzee, Cabrera, Scawthorn
  • International
  • Andalas University
  • ITB University
  • Indonesian Society Geotech. Engrg.
  • Nanyang Tech. University
  • New Zealand Engineers

3
Acknowledgements
  • NSF EERI Learning From Earthquakes Program
  • with additional support from
  • Blume Earthquake Engineering Center, Stanford
  • Pacific Earthquake Engineering Research (PEER)
    Center
  • USGS
  • University of Pittsburgh, GSPIA
  • Team host organizations
  • Degenkolb Engineers
  • Forell Elsesser
  • Build Change
  • GeoHazards International
  • Risk Management Solutions, Inc.

4
History of Padang
Padang City 17th Century Trading Center
Population 900,000 (20x growth since
1940) Capital of West Sumatra
City Center
Old City
Batang Arau River
5
Impact Road Damage
Sengara, I.W. et al., 2009
6
Impact Bridge Damage
7
Impact Foundation Damage
  • Provincial Public Works Building
  • 4 story, built 1976
  • Soft/Weak first story
  • Columns experienced 12 drift
  • Site experienced liquefaction
  • 100 m from Batang Arau River

8
Impact Utility and Lifeline Systems
  • Airport
  • closed 3 hrs, regular ops 1 day
  • Electric Power
  • distributed transformer damage
  • restored 20 within 5 days
  • fully restored within 8 days
  • Phone/Communication
  • landlines OK, cell restored within days
  • Water
  • 1 of 2 main supply pipes and 1 of 2 main
    distillation tanks ruptured
  • back to 60 within 2 weeks
  • Port Facility
  • little damage, south of town

damaged water treatment
9
Outline
  • Building Types and Occupancies
  • Acceleration Response vs Design Base Shear in
    Building Code
  • Typical Building Damage Collapse Mode
  • Building Design Construction in Padang
  • Building Case Studies
  • Summary of Buildings Performance
  • Improving Buildings Performance

10
Building Types and Occupancies
  • Government Offices
  • Schools
  • Hospitals
  • Commercial Buildings
  • Offices and Banks
  • Retail Malls
  • Hotels
  • Home-shops (Ruko)
  • Residential Homes

Primarily Reinforced Concrete Frames with Brick
Infill Walls
Few Steel Moment Frames
URM, Confined Masonry, Wood
11
Comparison to Building Code
Spectral Acceleration - 5 damping - NS
component - stiff soil site
  • Building Code Requirements
  • 1970 Base shear 0.1g, working stress design
  • 1987 PGA 0.25 0.36g, 2 soil types,
    inelastic R4
  • 2002 Similar to 1987, 3 soil types, capacity
    design
  • increase in short period spectral
    demands

12
Building Damage and Collapse
Complete Collapse
  • Story Collapse

13
Building Damage and Collapse
Brick Masonry
Infill Wall NS Damage
14
Building Design Construction
  • Seismic Design Codes
  • Established by national committee (Jakarta)
  • First established 1970, updates in 1987 and 2002
  • Currently revising to model after U.S. IBC ASCE
    7
  • Expertise of Local Professionals
  • Engineering education at university
  • Little professional development continuing
    education in Padang
  • Little training/certification of contractors
  • Code Compliance Quality Assurance
  • Field observations and interviews suggest lack of
    compliance
  • Problems most significant with small projects and
    renovations
  • Common to other developing countries (lack of
    well established process, insufficient resources
    to implement, lack of education)

15
Building Case Studies
  • SMK 9
  • M Djamil Hospital
  • Provincial Planning Building
  • Ambacang Hotel
  • Hotel Mariani
  • Dutch Colonial Chinatown Buildings
  • Lasano Kampong Dalam Village
  • Padang Ruko Buildings

16
SMK 9 School
  • High School
  • 3 story, built 1997
  • Partial floor and stair collapse
  • Weak/Captive Columns
  • 2 casualties (non-students)
  • many students at time of EQ
  • EQ Drills teach duck and cover
  • Students ran out of building
  • No student victims

17
Sentral Plasa Raya Mall
  • 3 story concrete frame/brick infill building
    built in 2005
  • Back end collapsed
  • Brick infill failures
  • Non-structural damage

FRONT END
BACK END
18
Sentral Plasa Raya Mall
  • Heavy mass at the back end
  • Column detailing
  • Small ties with 90 degree hooks
  • Column failure at lap splice

19
Provincial Planning Building
  • 3 story, 1981-83
  • 1st Floor Collapse
  • Configuration
  • Design and Detailing
  • smooth bars
  • small ties w/ 90 degree hooks
  • Construction quality
  • 2 Casualties
  • 80 occupants in building during EQ
  • Impact on rebuilding effort
  • Many files still in building

20
M Djamil Hospital
  • Largest hospital in Padang (800 beds)
  • 13 buildings, only 1 building sustained major
    damage
  • Outpatient Building
  • 3 stories, built in 1982
  • First floor collapsed
  • No casualties
  • Pounding between segments

21
M Djamil Hospital
Vaulted roof at the atrium
Damage at the one end of the cross shape
22
Ambacang Hotel
  • Originally a 1900 Dutch 2-story masonry
    warehouse, later expanded to 5 stories
  • Both concrete steel frames
  • Irregular, no clear load path
  • Partial story collapse at 2nd Floor of main
    building

BEFORE EQ
23
Ambacang Hotel
  • Separate 6 story steel building (built in 2005)
    fully collapsed
  • Poor moment frame connection detail
  • No continuity plate
  • Weak way bending
  • Slender columns
  • 200 fatalities in the hotel (est.)

24
Hotel Mariani
  • 4-6 story 2006 steel building collapsed, 3-story
    1963 concrete building damaged but survived
  • One of few steel buildings in Padang
  • Weak axis column bending led to progressive
    collapse

25
Hotel Mariani
Building collapsed towards the back
Moment frame failed weak way
26
Dutch Colonial Chinatown Districts
  • 100 year old buildings, adjacent to the river
  • Unreinforced masonry buildings w/ wood roofs
    floors
  • Out-of-plane collapse

27
Lasano Kampong Dalam Village
  • Small village in hills outside of Pariaman
  • URM, confined masonry
  • URM houses sustained the most damage
  • Settlement resulted in damage to several homes
  • Liquefaction

28
Lasano Kampong Dalam Village
Confined Masonry Buildings
  • Improved version of URM
  • Promoted in rural areas in Indonesia
  • Reinforced concrete element for confinement
  • Fairly well performance

29
Ruko Buildings in Padang
  • Ruko very common in Padang
  • 2 to 3-story tall
  • commercial residential
  • Stiffness irregularity
  • Various performance
  • Some collapse some minor damage
  • No comprehensive plan check

30
Performance of Concrete Buildings
  • Soft/weak story
  • Weak columns
  • Inadequate steel reinforcement
  • not enough steel
  • nonconforming details
  • Poor quality concrete
  • Insufficient lateral strength and stiffness
  • Brittle architectural finishes

31
Performance of Concrete Buildings
  • Damage to older buildings is not unexpected
  • Damage to newer buildings was greater than
    expected

32
Performance of Steel Buildings
  • Poor moment frame detailing
  • Weak way bending
  • Poor welding
  • Nonconforming to code
  • Slender column sections for moment frame
  • Insufficient strength and stiffness - significant
    drift
  • Non-familiarity with steel design and
    construction in the area

33
Performance of Masonry Buildings
  • Unreinforced Masonry
  • Poor quality materials and workmanship
  • No confinement to prevent out-of-plane wall
    failure
  • Confined Masonry
  • Performed fairly well
  • Guidelines available for single family homes but
    no code provision

34
Improving Buildings Performance
  • Proper enforcement implementation of the
    Building Code
  • continuing education
  • quality assurance
  • training/certifications of contractors
  • Building code provision for residential homes and
    ruko/homeshops
  • Challenge to implement these in the
    re-construction effort

35
Outline
  • Tsunami Risk
  • Preparedness Efforts
  • Tsunami Evacuation during 9/30 Earthquake
  • Performance of Tsunami Evacuation Structures
  • Observations Lessons Learned

36
Tsunami Risk in Padang
  • One of the highest tsunami risks in the world

Risk is a function of the hazard and exposure
37
Tsunami Hazard in Padang
Indian Ocean Tsunami December 2004
Banda Aceh
Killed more than half the population in Banda
Aceh Padang is exposed to a similar hazard from
same fault
Before 2004 Tsunami
Banda Aceh
38
Seismological Background
39
Tsunami Mechanism
40
Tsunami Mechanism
41
  • First big rupture on the Sundamegathrust occurred
    in 2004

The second big rupture occurred in March 2005
Northern part of Mentawai patch remains locked
The third rupture occurred in a series of events,
with an aftershock of M7.9
Source Kerry Sieh
42
Vulnerable Terrain
43
Population Density and Distribution
  • 900,000 people
  • Almost 9,000/km2 at city center
  • gt½ the population lives within a 5 meter
    elevation
  • Mostly fishermen
  • lt30 minutes to evacuate
  • Inundation distance 2 km

44
Preparedness Efforts in Padang
  • One of 6 cities designated to undertake
    earthquake and tsunami risk reduction after 2004
  • Early warning systems
  • Planning evacuation routes
  • Education and evacuation drills
  • duck, cover, hold
  • tsunami evacuation
  • Over 50,000 people will still be unable to
    evacuate within lt 30 minute tsunami arrival time

45
Evacuation Structures Examples
Bridges Designed to be earthquake-resistant and
serve as element of horizontal evacuation
Refuge Structures Designed to rise above the
expected tsunami inundation level, and withstand
the expected earthquake and tsunami forces
provides vertical evacuation
46
Evacuation Structures Existing Buildings
  • Regulation requires all buildings gt 2 stories to
    serve as evacuation site during tsunami
  • Existing Building Surveys
  • 5 different organizations
  • Based on location and capacity, suitability not
    thoroughly considered
  • Seismic deficiencies not considered
  • Buildings used as sites in evacuation simulations

47
Tsunami Evacuation
  • Most people evacuated after shaking
  • Problems with evacuation plan
  • sometimes slow to initiate
  • traffic jams (1-2 hrs)
  • lack of information and coordination
  • Little evidence of vertical evacuation
  • Roads and bridges generally intact
  • Performance of evacuation buildings
  • 1/3 collapsed or heavily damaged
  • 3/4 had sufficient damage to be closed

48
Evacuation Structures Bridges
Coastline
High Ground
49
Evacuation Structures LBA LIA
July 2009
October 2009
  • 4 story language school
  • First 2 stories collapsed

50
Evacuation Structures STBA Prayoga
July 2009
October 2009
  • 4 story junior college
  • Complete collapse

51
Evacuation Structures Plasa Andalas
July 2009
October 2009
  • 4 story mall
  • Partial collapse on 4th floor and fire

52
Good Candidates for Evacuation
  • Indonesian Bank Complex
  • Tsunami evacuation
  • large building
  • elevated site
  • terrace _at_ 20 m
  • on-site security
  • Moderate EQ damage
  • Evacuation lessons
  • public awareness
  • individuals must feel safe confident

53
Good Candidates for Evacuation
  • Major mosques in general are good candidates for
    evacuation
  • Large prayer area
  • Redundant structures
  • Better construction quality
  • Good accessibility
  • People tend to go to mosques after disasters
  • 100 people evacuated to Masjid Taqwa after the
    earthquake

54
Observations and Lessons
  • Overview of Damage
  • Buildings
  • Bridges and Transportation
  • Utility Lifelines
  • Deaths and Injuries
  • Resiliency of Padang City
  • Tsunami Evacuation
  • Tsunami still a threat
  • Inadequate evacuation capacity
  • Evacuation structures are crucial
  • Building Code provisions and enforcement
  • Rebuilding Better / Safer?

55
Thanks!
  • Questions?
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