Title: Observations and Lessons on Earthquake and Tsunami Risk Mitigation in Padang, Indonesia
1Observations and Lessons on Earthquake and
Tsunami Risk Mitigation in Padang, Indonesia
- Nick Alexander, Degenkolb Engineers
- Veronica Cedillos, GeoHazards International
- Louise Comfort, University of Pittsburgh
2Reconnaissance 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
3Acknowledgements
- 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.
4History 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
5Impact Road Damage
Sengara, I.W. et al., 2009
6Impact Bridge Damage
7Impact 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
8Impact 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
9Outline
- 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
10Building 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
11Comparison 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 -
12Building Damage and Collapse
Complete Collapse
13Building Damage and Collapse
Brick Masonry
Infill Wall NS Damage
14Building 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)
15Building 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
16SMK 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
17Sentral 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
18Sentral Plasa Raya Mall
- Heavy mass at the back end
- Column detailing
- Small ties with 90 degree hooks
- Column failure at lap splice
19Provincial 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
20M 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
21M Djamil Hospital
Vaulted roof at the atrium
Damage at the one end of the cross shape
22Ambacang 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
23Ambacang 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.)
24Hotel 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
25Hotel Mariani
Building collapsed towards the back
Moment frame failed weak way
26Dutch Colonial Chinatown Districts
- 100 year old buildings, adjacent to the river
- Unreinforced masonry buildings w/ wood roofs
floors - Out-of-plane collapse
27Lasano 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
28Lasano Kampong Dalam Village
Confined Masonry Buildings
- Improved version of URM
- Promoted in rural areas in Indonesia
- Reinforced concrete element for confinement
- Fairly well performance
29Ruko 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
30Performance 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
31Performance of Concrete Buildings
- Damage to older buildings is not unexpected
- Damage to newer buildings was greater than
expected
32Performance 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
33Performance 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
34Improving 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
35Outline
- Tsunami Risk
- Preparedness Efforts
- Tsunami Evacuation during 9/30 Earthquake
- Performance of Tsunami Evacuation Structures
- Observations Lessons Learned
36Tsunami Risk in Padang
- One of the highest tsunami risks in the world
Risk is a function of the hazard and exposure
37Tsunami 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
38Seismological Background
39Tsunami Mechanism
40Tsunami 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
42Vulnerable Terrain
43Population Density and Distribution
- 900,000 people
- Almost 9,000/km2 at city center
- gtĀ½ the population lives within a 5 meter
elevation - Mostly fishermen
- lt30 minutes to evacuate
- Inundation distance 2 km
44Preparedness 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
45Evacuation 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
46Evacuation 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
47Tsunami 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
48Evacuation Structures Bridges
Coastline
High Ground
49Evacuation Structures LBA LIA
July 2009
October 2009
- 4 story language school
- First 2 stories collapsed
50Evacuation Structures STBA Prayoga
July 2009
October 2009
- 4 story junior college
- Complete collapse
51Evacuation Structures Plasa Andalas
July 2009
October 2009
- 4 story mall
- Partial collapse on 4th floor and fire
52Good 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
53Good 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
54Observations 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?
55Thanks!