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Preliminary Findings of Transportation Infrastructure Performance of the Offshore Maule Earthquake in Chile
by US DOT/FHWA Transportation Infrastructure Reconnaissance Team
W. Phillip Yen, Daniel Alzamora, Ian Buckle, Jeffrey Ger, Genda Chen, Tony Allen, Juan Arias
AcknowledgementsFHWA HRT Office & HRDI OfficeFHWA International Program OfficeFHWA Field/ Technical Service Office (RC & FL)US Embassy in Chile & Chilean Embassy in USMOP, International Program OfficeMOP, Bridge Design OfficeMOP, Concession OfficeUniversidad CatolicaUniversidad de Chile
Magnitude 8.8 - OFFSHORE MAULE, CHILE2010 February 27 06:34:14 UTC
Earthquake Details
Magnitude 8.8
Date-Time Saturday, February 27, 2010 at 03:34:14 AM at epicenter
Location 35.909°S, 72.733°W
Depth 35 km (21.7 miles) set by location program
Region OFFSHORE MAULE, CHILE
Distances
95 km (60 miles) NW of Chillan, Chile105 km (65 miles) NNE of Concepcion, Chile115 km (70 miles) WSW of Talca, Chile335 km (210 miles) SW of SANTIAGO, Chile
Location Uncertainty
horizontal +/- 6.2 km (3.9 miles); depth fixed by location Program
Parameters NST=391, Nph=391, Dmin=987.2 km, Rmss=1.17 sec, Gp=14°, M-type=teleseismic moment magnitude (Mw), Version=8
Source • USGS NEIC (WDCS-D)
USGS Data
Chilean Seismic Design CodesBefore 1950s based on the handbook published by Alberto Claro Velasco “Normas para el Cálculo y Proyecto de Puentes Carreteros de Hormigón Armado”
After 1960 Inspired by Japanese Bridge Seismic Design Practice
After 1971 Influenced by Japanese and AASHTO Bridge Codes
in early 1970s Cs =0.12gAfter 1985, seismic design code is similar to AASHTO Division 1A, using Cs = 0.15gAfter 2002, Similar to AASHTO w/ Cs = 0.3g for all bridges using working stress method
Note: Concessions Bridge Design was influenced by Spanish Design & Practices – starting from 1996
Washington, Oregon and California States’ Subduction Fault Zones Chilean Subduction Fault Zones
Subduction Fault Zones
US DOT/FHWATransportation Infrastructure Reconnaissance Team (TIRT) Members
Phillip Yen (FHWA), LeaderDaniel Alzamora (FHWA)Jeffrey Ger (FHWA)Ian Buckle (UNR)Genda Chen (Missouri S&T)Tony Allen (WSDOT)Juan Arias (EERI) -- Guest memberDavid Lau (Canada) – Guest member
•Sheila Duwadi: Team Coordinator FHWA
Supporting members from Chile•Rodrigo Oviedo (Univ. Catolica)•Mauricio Guzman (MOP)•Sandra Achurra (MOP)
US DOT/FHWA TIRT Team Mission
Working with Chilean bridge engineers to perform a thorough post-earthquake investigation concentrating on highway bridges, tunnels, and retaining walls in the areas affected by the earthquake, including the cities of Concepcion and Santiago. Documenting and analyzing the performance of these infrastructures, including damaged and non-damaged conditions. This information will then be used to assess, refine and improve design codes and standards that benefit both countries and the general engineering community.
Summary of the trip
5 Meetings with MOP and Universities 3 meetings w/MOP (Concession, Bridge
Design and Office of International Program) 2 Meetings w/ University of Chile
Post-EQ Investigations in 32 sites 4 major cities – Santiago, Concepcion, Curico & Constitucion.
Traveled more than 1,000 miles in 8 days. 2 + 1 vehicles
Total 12,000 (roughly)Federal 10,000 Concessions 2,000Damaged 100
Collapsed - 20*12 Pedestrian*8 Overpasses
Infrastructure Sites Visited by FHWA Team: 32More than 1,000 miles of road travel
Bridges in Chile
Transportation Infrastructure Performance
Bridge designed with Chilean Seismic Design codes performed very well. Concessions’ bridges did not perform as well.
Bridges severely damaged or collapsed due to insufficient seat width and/ or transverse/ rotational constrains - including shear keys, most of them were constructed after 1996.
Tsunami area
Bridges performed well with shear reinforcement
Highway pavements did not perform well
Ground failure caused bridge damage or collapses.
MSE wall and anchored retaining wall performed well
Tunnels were not damaged
Superstructure Rotation
Close-up View of Earthquake-Induced Damage at E. Abutment
Abutment Sidewalls Damaged
W. Abutment
E. Abutment
Acute Corner
Puente Miraflores with ~20° Skew (E. Bound Traffic)
Obtuse Corner
Superstructure Rotation
Overpass of Route 5 in Romero Av. with ~20° Skew
Sidewall Damaged Sidewall
Intact
Overpass of Route 5 in Puente Chada with no Skew
E. Abutment W. Abutment
Superstructure Rotation
Flexible Steel Brackets (West Bound Traffic Closed due to Earthquake-Induced Damage, Lo Echevers)
Elastomeric Bearing Overloaded (East Bound Traffic Open, Lo Echevers)
Superstructure Rotation
Summary of Field Observations The decks of all skewed bridges experiencing
in-plane rotations (e.g. Miraflores, Lo Echeveres, Romero Av., and Hospital) consistently turned toward the acute corner of the bridges regardless of their skew orientation.
The decks of regular bridges with no skew (e.g. Chada) rotated counter clockwise similar to the nearby skewed bridge (Romero Av.). The Las Mercedes bridge also rotated counter clockwise.
Rotation in straight bridges (R5)
Puente Chada
Rotation in skew bridges (Route 5)
Romero Bdg
Superstructure Rotation
Plausible Causes Dominant rotational mode of vibration in
terms of ground motion effects (as illustrated in next slide)
Rotation amplification due to the bouncing effect of abutment once in contact
Rotational component of ground motions (need to be verified with the use of time history analyses)
Steel Superstructure Bridges
Steel Girder DamagePuente Cardenal Raul Silva Enriquez 20-span structure built in 2002 NE portion supported on drilled shaft foundations SW portion supported on ? (more flexible) One expansion joint in the middle of the bridge One expansion joint at each end of the bridge deck The bottom flanges of end girders are fixed to abutment
Puente Pichibudis (Earthquake & Tsunami) Single-span, steel girder structure in the City of Iloca End concrete diaphragms
Puente Cardenal Raul Silva Henriquez
•Transverse horizontal shear induced damage of diaphragmsand girders
•Bending of steel girders about weak axisat north abutment
•Fracture of web and bottom flange and buckling of stiffeners at north abutment
Buckled brace diaphragmabove pier support
Girder bending in weak axis
Puente Cardenal Raul Silva Enriquez
Back Wall on NE Abutment
Bridge Spans
Web Fracture
Masonry Plate Anchored into Abutment Seat
Underneath Bridge Deck Temporary
SupportBearing Stiffener Buckled
Web Buckled
Weld Fractured
Flange & Bearing Stiffeners Welded to Masonry Plate
Damages due mainly to Longitudinal Earthquake Force
Fixed bearing on exp. joint
Fix Bearing
Crack
SlabExp. Joint
Flange Buckling
Puente Cardenal Raul Silva Enriquez
End Diaphragm Damage
Buckling
Puente Cardenal Raul Silva Enriquez
Temporary Support at the NE End of the Bridge
Floor Beam Welded to Girder
Two Vertical Supports on Each Side
X-Bracing
Puente Pichibudis
Overview of the Bridge under Earthquake and Tsunami Effects
Deck and Approach
18 cm
Lateral Offset
Pipeline
Puente Pichibudis
Global Displacements
Less Twist on Inland Side
More Twist on Ocean Side
Steel Girder Damage
Summary of Field Observations Global transverse displacement and twist Elastomeric bearing / Neopreme pad displaced Bottom flanges of girders fractured No apparent impact from Tsunami
Plausible Causes Excessive earthquake force mainly along the bridge Fixed supports of girders by welding their bottom flanges
to masonry plates that are anchored into the abutment
Bridge Damaged by Superstructure Large Movement
Bridge collapse or damage due to transverse movement
•Shear Key Issue•Concrete Diaphragm
Steel stopper does not perform well, and is flexible
Steel stoppers on concrete pedestals
Flexible steel stopper
Bridges with shear concrete blocks performed well
Bridges have shear concrete blocks which performed well
Skewed Vs Straight Bridges
Two overpass bridges across a railway: one is skewed and the other is straight
Skewed BridgesRotation
Concrete Diaphragm
Distribute seismic lateral load uniformly to each bearing.Reduce superstructure falling off the beam cap.provide stability of girders
Performance w/ and w/o Concrete Diaphragm
Bridge collapse or damage due to superstructure longitudinal movement
Small seat widthBack wall damaged due to poundingSteel girder damaged due to longitudinal
movementBridge collapsed due to simple support
beams with non-integral abutments.
Small Seat Width
Pounding on Backwall
Girder Damaged
Vertical Restrainers
Longitudinal movement of simple support beams with non-integral abutments.
TUBUL Bridge
Longitudinal movement of simple supported spans
Bio Bio
Tsunami area
Geotechnical Observations
Puente Biobio
Puerto Coronel Puente LLacolen
Effects of lateral spreading caused by liquefaction on Bridge Foundations
Puente RamadillasEffects of liquefaction caused settlement
Puente Juan Pablo II
Estribo Francisco Mostazal (Estribo “Verdadero”)MSE wall supported Bridge abutment
Americo Vespucio/IndependenciaExamples of free standing walls
Walls in general performed very well.
Puente La Mochita
Puente Raqui 2
Examples of liquefaction induced lateral spreading damage
Landslides in Tubul Bridge Area
Geotechnical Suggestions
Expand the geo-hazards mapping program already started in Chile to identify problem soils (e.g., soft, liquefiable, or unstable soils) that could increase potential for bridge or other structure failure during the design earthquakeDo ground improvement to prevent liquefaction at bridge foundations and abutmentsContinue to use drilled shaft foundations when liquefaction is likely to improve the likelihood that the bridge will survive the earthquakeImplement a shaft integrity testing program to verify shaft qualityWalls performed very well, but pay special attention to wall corners, as wall corners tend to attract forces
SummarySeat Length Support Increase Seat Width – Good Investment Minimum Seat Width as used in the US
Skewed/ Curved Bridges Rotational Constraint
Accelerated Bridge Construction Diaphragms and continuous span preferred
Alternative measure to repair Isolators – Reduce the Demand Forces
Long Duration Effects Pounding Effects
Approaches (Back fill) Should Be Designed by Geotechnical EngineersBridge Performed Well in Tsunami Area
