Preliminary Findings of Transportation Infrastructure...

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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

Thanks!Gracias!

Please contact Dr. W. Phillip Yen at wen-huei.yen@dot.govfor further information