ASPIRE Summer 08 - Aspire - The Concrete Bridge Magazine
ASPIRE Summer 08 - Aspire - The Concrete Bridge Magazine ASPIRE Summer 08 - Aspire - The Concrete Bridge Magazine
Girders on the draw pontoons, wherethe profile grade drops to the lowestpoint, use dapped ends and endblocks—with some cantilevering overpiers. To open the navigation channel,three lift spans are raised to allow thedraw pontoons to retract underneath.The draw span necessitates minimizingthe deck elevation while maintainingsufficient vertical clearance formaintenance vehicles underneath andto clear most storm waves.Temporary ballast water is used in thepontoon’s internal cells to balance thepontoons as the superstructure loadsare added. Regular monitoring of thepontoon freeboard (distance from topof the deck to water line) is needed tomaintain a level and stable structure atdockside. Specialized survey equipmenttracks the top plane of the deck as itmoves with the wind, waves, and theaddition of new loads. Constructionmeasurements are then referencedto this fluctuating theoretical plane.Permanent rock ballast is used to makefinal adjustments.Gravity AnchorConstructionFrom the public’s perspective, thereinforced concrete gravity anchorswere said to look like giant “tea cups,”measuring 29 ft tall and rangingin diameter from 46 ft to 60 ft. Theanchors are massive, stout vessels thatmust float initially. Built in Seattle, thelarge bowl-like structures were towed50 miles to Hood Canal, then loweredto the canal floor and filled with crushedrock ballast.The draw spans open for large vessels and submarines in the Hood Canal.The ballasting is required to attain thefinal submerged anchor weight, keepingthe pontoons in alignment during stormswithout shifting the anchors on the softsoil slopes. While the geometry of theanchors is complex, the general designdetails are straightforward. The anchorshave 3 in. of concrete clear cover to allreinforcement and a low-permeability,4000 psi concrete mix made with peagravel. Vertical post-tensioned bartendons are used in the walls at thepicking eye locations to distribute theshear forces from the setting operations.After the new east half of the bridgeis floated into place, 3-in.-diameteranchor cables will be threaded throughthe 27-in.-diameter pipe cast inside4.5-ft-thick, heavily reinforced walls andattached to the pontoons to complete theanchorage connections for the floatingbridge. Some of the gravity anchors areoffset nearly 2000 ft from the bridgealignment and rest in water as deepas 340 ft below mean tide. Cathodicprotection systems are used to protectthe anchor cables, thereby protecting thepontoons and the anchors.Floating into the FutureFrom the anchors 340 ft below thewaterway’s surface to the pontoonsand elevated roadway, the concreteof the new Hood Canal Bridge willbe tested regularly by the elements.High-performance concrete and theextensive use of pretensioning and posttensioningwill ensure that it passes itsdaily trials. The WSDOT has been able tolearn from its past experience to create anew structure that has set the standardfor floating bridges in the Washingtonstate highway system and beyond. Thenew Hood Canal Bridge is a balance ofform and function, putting innovativeideas into action and paving the way forimproved transportation well into thefuture._____________Mark A. Gaines is assistant stateconstruction engineer and Joseph M.Irwin is communications consultantfor the project with the WashingtonState Department of Transportation,Olympia, Wash. Michelle L. Tragesser iswith Parametrix, Tacoma, Wash., and istechnical services manager for the projectThe elevated roadway uses precast,prestressed concrete I-girders, and stay-inplacedeck panels. This construction methodreduced formwork efforts and improvedsafety for the over-water constructionactivities.For more information on this or otherprojects, visit www.aspirebridge.org.20 | ASPIRE, Summer 2008
BRIDGESFORLIFE ®FEATURING HIGH-PERFORMANCE BRIDGES2008 PCINATIONAL BRIDGECONFERENCEU.S. Department of TransportationFederal Highway AdministrationCosponsored by the Federal Highway AdministrationThe PCI National Bridge Conference (NBC) is the premiernational venue for the exchange of ideas andstate-of-the-art information on concrete bridge design,fabrication, and construction—particularly precast,prestressed concrete bridges. Public agenciesand industry have joined forces and are committedto bringing together the nation’s most experienced,expert practitioners. More than 90 papers will be presentedin 23 individual sessions. The NBC will be heldin conjunction with the PCI Annual Convention andExhibition, which offers additional opportunities.Sunday afternoon, October 5Opening Session featuring the 2008 PCI BridgeDesign Award PresentationsSpotlight State Plenary Session – The WashingtonState Department of TransportationMonday, October 6Technical Education SessionsTuesday, October 7Technical Education SessionsSocial Events and GatheringsThroughout the event, you’ll have ample time tonetwork with colleagues and establish or renewacquaintances. Social events include an openingreception gala, sumptuous buffet luncheons sponsoredby our exhibitors, and a banquet. Above all,you’ll have the opportunity to immerse yourself inthe state of the art of concrete bridges. An excitingprogram of tours and activities for accompanyingguests is also available.Special BonusThose registering for the National Bridge Conferencealso have the opportunity to participate in all the excitingcommittee meetings and educational sessionsof the PCI Annual Convention and Exhibition.For a listing of papers and presenters, and to viewregistration details as they develop, visit the conferencewebsite atwww.pci.org/news/bridge_conference/index.cfm.For more information, contact John Dick;Tel.: (312) 360-3205; Fax (312) 786-0353; orEmail: jdick@pci.org.OCTOBER 5–7, 2008, ROSEN SHINGLE CREEK RESORT, ORLANDO, FLA. PLAN NOW TO ATTEND!CON08-1192_HalfPgAd.indd 16/12/08 4:06:58 AMASPIRE, Summer 2008 | 21
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- Page 28 and 29: AvoidingLANDSLIDESby Kevin Harper,
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- Page 32 and 33: ECONOMICAL BRIDGEWIDENINGby Craig A
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- Page 41 and 42: Precast Span-by-SpanPrecast Balance
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- Page 49 and 50: The Methow River Bridge usesWSDOT
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BRIDGESFORLIFE ®FEATURING HIGH-PERFORMANCE BRIDGES20<strong>08</strong> PCINATIONAL BRIDGECONFERENCEU.S. Department of TransportationFederal Highway AdministrationCosponsored by the Federal Highway Administration<strong>The</strong> PCI National <strong>Bridge</strong> Conference (NBC) is the premiernational venue for the exchange of ideas andstate-of-the-art information on concrete bridge design,fabrication, and construction—particularly precast,prestressed concrete bridges. Public agenciesand industry have joined forces and are committedto bringing together the nation’s most experienced,expert practitioners. More than 90 papers will be presentedin 23 individual sessions. <strong>The</strong> NBC will be heldin conjunction with the PCI Annual Convention andExhibition, which offers additional opportunities.Sunday afternoon, October 5Opening Session featuring the 20<strong>08</strong> PCI <strong>Bridge</strong>Design Award PresentationsSpotlight State Plenary Session – <strong>The</strong> WashingtonState Department of TransportationMonday, October 6Technical Education SessionsTuesday, October 7Technical Education SessionsSocial Events and GatheringsThroughout the event, you’ll have ample time tonetwork with colleagues and establish or renewacquaintances. Social events include an openingreception gala, sumptuous buffet luncheons sponsoredby our exhibitors, and a banquet. Above all,you’ll have the opportunity to immerse yourself inthe state of the art of concrete bridges. An excitingprogram of tours and activities for accompanyingguests is also available.Special BonusThose registering for the National <strong>Bridge</strong> Conferencealso have the opportunity to participate in all the excitingcommittee meetings and educational sessionsof the PCI Annual Convention and Exhibition.For a listing of papers and presenters, and to viewregistration details as they develop, visit the conferencewebsite atwww.pci.org/news/bridge_conference/index.cfm.For more information, contact John Dick;Tel.: (312) 360-3205; Fax (312) 786-0353; orEmail: jdick@pci.org.OCTOBER 5–7, 20<strong>08</strong>, ROSEN SHINGLE CREEK RESORT, ORLANDO, FLA. PLAN NOW TO ATTEND!CON<strong>08</strong>-1192_HalfPgAd.indd 16/12/<strong>08</strong> 4:06:58 AM<strong>ASPIRE</strong>, <strong>Summer</strong> 20<strong>08</strong> | 21
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