ASPIRE Summer 08 - Aspire - The Concrete Bridge Magazine

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Precast, prestressed concrete beams were used because of a lack of clearancefor falsework and to speed construction.Limited Vertical ClearanceOne of the significant logistical concernswas the inadequate vertical clearanceavailable for using falsework. Using castin-placebox girders to replicate the lookof the existing bridge and surroundingstructures would have required falseworkspanning three traffic lanes in eachdirection, he explains. “The availablevertical clearance was not adequate toaccommodate falsework deep enoughto span three lanes of traffic. This wasthe key factor in choosing precastconcrete.”The girders and deck panels also offereda shortened construction time, as theycould be fabricated off-site and erectedquickly upon arrival. “The precast girderssignificantly reduced the timeframe forimpacting on-going traffic,” he says.The project was designed in six months,with construction taking about 1 year.But the actual road closure to erect theprecast girders amounted to only 2 daysduring this period.Although cast-in-place girders could notbe used due to falsework requirements,the concern was that the use of precast,prestressed concrete bulb-tee girderswould not blend with the appearanceof the rest of the bridge, or with otherbridges in the area. “We usually seecast-in-place box girders being used inCalifornia, and the agencies involvedin this project wanted to match theirdesign,” Kazmi explains.To replicate that look, precast, prestressedconcrete rectangular box girders wereused as the exterior girder on each side ofthe bridge. The girders were deeper thanthey were wide and featured a roundedoutside fascia corner to replicate the lookof cast-in-place box girders. The designprovided the box shape that all the bridgesoffered to drivers nearing the structures,he says. Inside girders, which are viewedonly when cars are directly beneath them,are bulb-tee sections. “Motorists see thelook of a concrete box-girder bridge asthey approach, and the structure blendswell with the adjacent structures.” Thiscombination of girders kept the cost ofthe project in line by using less expensivebulb-tee girders in the less visible area, henotes.AestheticsThe existing structure and several structures along the corridor arecast-in-place box girder bridges with vertical webs for the exteriorgirders. The use of more typical precast, prestressed concrete girdersat this location would not have matched the aesthetic characterof the bridges. The problem was addressed by the use of precast,prestressed concrete rectangular box girders with a rounded outsidecorner for the exterior girders. This gives the motorist the look of aconcrete box girder bridge and the structure blends well with theadjacent structures.Speed of Construction and Public SafetyAnother challenge on this project was the need for a structuretype that could be built quickly and would significantly reduce theduration of the inconvenience to the on-going traffic. This was largelyachieved by the efficient use of precast, prestressed concrete girdersas well as permanent precast concrete deck panels.32 | ASPIRE, Summer 2008
While preparation work was underwayat the site, the girders were cast at theprecaster’s Perris, Calif., plant. Oncethey arrived at the site, all 32 girderswere erected in 2 days, while the roadunder the bridge was closed and trafficrerouted. Traffic could flow under thebridge while the precast concrete deckpanels were being installed. “Beingable to keep traffic open while thedeck panels were installed provided aconsiderable advantage.”The project achieved all the goals set forit, by combining several types of girdersand maximizing the benefits offeredby the precast concrete design. “Therewere a number of factors that createdkey challenges on this project,” saysKazmi. “But solutions for all of themwere made possible because of the useof precast concrete members.”Economical, Efficient&Elegant SolutionsBridge ServicesPlanningDesignInspectionRehabilitationProgram ManagementConstruction ManagementWorldwide Expertise & Local ExperienceMillburn, NJ 973.379.3400Pleasanton, CA 925.469.8010Pensacola, FL 850.484.6011Mississauga, ON 905.855.2010For more information on this or otherprojects, visit www.aspirebridge.org.Hatch MottMacDonaldRobert ShulockPractice Leader, Highways & Bridges206-855-0968QAEdison Bridge, Fort Myers, FloridaHow do you connectthe rebar?Use the…NMBSplice-Sleeve ®System.How to do it in Precast…cross-sectionQAHow is the moment connection made?All you need is an emulative detail,reconnect the concrete and rebar.Mill Street Bridge, Epping, New HampshireSPLICE SLEEVE NORTH AMERICA, INC.WWW.SPLICESLEEVE.COM11003_SPLICE_.5bridge_win08.indd 111/30/07 10:51:14 AMASPIRE, Summer 2008 | 33
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Page 24 and 25: Replacement of the I-10 Bridgesacro
Page 26 and 27: Precast, prestressed concrete girde
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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