ASPIRE Spring 08 - Aspire - The Concrete Bridge Magazine

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Spalling of concrete cover on the columnsresulted in areas of exposed spiralreinforcement.The pink color shown in this girder from the Puyallup bridge fire indicates that theconcrete was exposed to temperatures higher than 500 ˚F.Concrete Core SamplesEight vertical concrete cores from thehot zone, two vertical cores from thecoolest zone, and eight horizontal coresfrom the hot zone were removed fromthe prestressed concrete beams. Sevencores were examined petrographicallyin general accordance with ASTMC 856. The extent and severity of firedamage was based on observed changesin aggregate and cement paste color,mineralogy, and microstructure. Based onthe petrographers’ evaluation, which alsoincluded some informal heating tests,the state was convinced that surfacetemperatures on the bottom flangesoffits exceeded 1500 °F during the fire.Compression tests performed on coresamples indicated that much of theundamaged concrete had a compressivestrength exceeding 9000 psi. Significantportions of core samples from thehottest zone, however, were fracturedand untestable.Eight concrete cores were taken fromthe two columns at Pier 9. Theseconfirmed the existence of delaminationsin the interior core of the column. Themaximum depth of fracture was foundto be 5 in. from the original surfaceand more than 1 in. inside the verticalcolumn reinforcement. Aside from thedelaminations, the concrete remainingin the column appeared to have verygood strength.A core sample from the crossbeam atPier 9 did not show any abnormalitiesand indicated that the crossbeamsustained only superficial damage fromthe fire.SummaryThe railroad tanker fire subjected all 15girders in Span 8 to intense heat in ashort period of time. Flame temperatureswere estimated to be approximately3000 °F and surface temperatures on thesoffit of the prestressed concrete girdersmay have reached 1700 °F. Internaltemperatures in the bottom flange andwebs were estimated to range from500 to 1100 °F. The prestressing steelsurvived the fire without noticeable lossof prestress.Rapid identification of concrete damagezones can be made by observing thevariation in concrete color immediatelyfollowing a fire. The visual colormapping correlated very well withvariations in concrete hardness. Therebound hammer test validated thevisual observations and provided anobjective description of the damagedareas. With this information, rationaldiscussions could be made about repairor replacement.All 15 lines of girders in Span 8were damaged by the fire butthe bridge was opened on thenext morning.26 | ASPIRE, Spring 2008
ReferenceDesign for Fire Resistance of Precast,Prestressed Concrete, Second Edition,MNL-124-89, Precast/PrestressedConcrete Institute, Chicago, IL, 1989,96 pp.AcknowledgementThis article is based on a full-length papertitled “Inspections and Repair of a FireDamaged Prestressed Girder Bridge,”presented at the International BridgeConference, Pittsburgh, June 2004, PaperNo. IBC-04-17 which is available at www.aspirebridge.org/resources._____________________Richard B. Stoddard is Bridge DesignEngineer with the Bridges and StructuresOffice of the Washington StateDepartment of Transportation.Advertisers IndexBASF.. . . . . . . . . . Inside Back CoverBentley/LEAP .. . . Inside Front CoverCampbell Scientific.. . . . . . . . . . . 63CH2M Hill .. . . . . . . . . . . . . . . . . . . 7DSI. ........................ 15Eriksson Technologies.....Back CoverFinley Engineering.. . . . . . . . . . . . 51FIGG .. . . . . . . . . . . . . . . . . . . . . . . . 3Gerdau Ameristeel............. 27Lehigh Cement................ 23PCAP—CABA.................. 14Scott System ................. 33Splice Sleeve. ................ 33Stalite....................... 57Standard Concrete Products..... 43T.Y. Lin International .. . . . . . . . . . . 5Williams Form Eng. Corp. ....... 61VSL .. . . . . . . . . . . . . . . . . . . . . . . . . 4ZBar ad_BRis_Aspire-Mar:Zbar ad 2/14/08 1:20 PM Page 1High PerformanceCorrosion ProtectionPatent-PendingDual CoatingProcessSome surface damage occurred in the topflanges.Fusion-Bonded PowderOuter Coating…ZBAR’s first line of defenseagainst water and chlorideswhich lead to corrosion.Thermal Zinc Inner Coating…Durable; providing sacrificialgalvanic protection if damaged.Next GenerationCorrosion ProtectionCompliant WithThe Federally FundedHighways for Life Program…Contact Us For Complete Details.Damage concrete surrounding the straightprestressing strands was easy to remove.For more information on this or otherprojects, visit www.aspirebridge.org.CALL 888-637-9950 FORSALES & ORDERING INFORMATIONwww.gerdauameristeel.com/zbarASPIRE, Spring 2008 | 27
Page 1 and 2: THE CONCRETE BRIDGE MAGAZINESPRING
Page 4 and 5: EDITORIALPhoto: Ted Lacey Photograp
Page 6 and 7: READER RESPONSEw w w . a s p i r e
Page 8 and 9: CONTRIBUTING AUTHORSCONCRETE CALEND
Page 10 and 11: FOCUSCH2M Hill’sHolisticApproachb
Page 12 and 13: As the largest highwayconstructionp
Page 14 and 15: ‘Designers are starting to treat
Page 17 and 18: Post-tensioning is being utilized o
Page 19 and 20: Aesthetic requirements played a key
Page 21 and 22: Photo: U.S. Fish & Wildlife Service
Page 23 and 24: Although flame temperatures at this
Page 25 and 26: HPCSafe, Affordable,and Effi cient2
Page 27: within the concrete just inside the
Page 31 and 32: The 1.3-mile-long Des Plaines River
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Page 41 and 42: A view of the nearlycompleted first
Page 43 and 44: An ‘Environmentally Friendly’ B
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Page 51 and 52: loads include the usual wind, therm
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