Case History: Brooklyn Bridge Redecking L. B. Foster Fabricated Products 1016 Greentree Road Pittsburgh, PA 15220 412-928-7854 Fax (412) 928-3514 www.lbfoster.com Commuters Spared Trafc Nightmares By the 15th of December, 1999 New York City’s historic Brooklyn Bridge had received over 207,000 SF of new bridge deck, the subooring system (stringers) supporting the deck, and a new riding surface. The prospect of redecking such an important trafc link (over130,000 ADT) in a congested urban setting is indeed daunting. What is remarkable is that actual construction did not begin until late June, 1999 and all of the structural steel support deck/overlay work took place during off-peak trafc hours, from 11 PM to 6 AM. Rush-hourcommuters were thus spared the tremendous inconvenience of making their way through a bridge construction zone. Background The previous deck of the Brooklyn Bridge was installed in 1953 and was a unique, 3” deep concrete lled steel grid. An inverted, U-shaped concrete form pan was inserted into a standard 3” grid I-beam section, producing an extremely light (41#SF), shallow, but “closed” deck for the bridge. At the time, ADT was less than 20,000. In an effort to improve on the deck’s ush-lled ride surface, small anti-skids studs were welded to the top of the grid main bars in the 1970’s. Later, in the mid 1980’s, in order to further improve the surface as well as quiet the hum caused by the studs, a thin (1/2) polymeroverlay (trade name Flexolith®) was placed. Fabricated Products
L. B. Foster FabricatedProducts1016 Greentree RoadPittsburgh, PA 15220412-928-7854Fax (412) 928-3514www.lbfoster.com
Commuters Spared Traf c Nightmares
By the 15th of December,1999 New York City’s historicBrooklyn Bridge had receivedover 207,000 SF of new bridgedeck, the sub ooring system(stringers) supporting the deck,and a new riding surface. The
prospect of redecking such
an important traf c link (over 130,000 ADT) in a congested
urban setting is indeed daunting.What is remarkable is thatactual construction did not beginuntil late June, 1999 and allof the structural steel supportdeck/overlay work took placeduring off-peak traf c hours,from 11 PM to 6 AM. Rush-hour
commuters were thus sparedthe tremendous inconvenienceof making their way through a
bridge construction zone.
BackgroundThe previous deck of theBrooklyn Bridge was installedin 1953 and was a unique, 3”deep concrete lled steel grid.
An inverted, U-shaped concreteform pan was inserted into astandard 3” grid I-beam section,
producing an extremely light(41#SF), shallow, but “closed”deck for the bridge. At the time,ADT was less than 20,000.In an effort to improve on the
deck’s ush- lled ride surface,small anti-skids studs werewelded to the top of the gridmain bars in the 1970’s. Later,in the mid 1980’s, in order tofurther improve the surface aswell as quiet the hum caused bythe studs, a thin (1/2) polymer overlay (trade name Flexolith®)was placed.
In 1997 a decision was made by the City DOT to replace the polymer overlay, which was
experiencing delamination.The plan was to remove the
polymer using hydro-millingtechniques, and to install a liquid,waterproo ng membrane and a thin,asphaltic-based wearing courseknown as “microsurfacing”. The“microsurfacing” system was usedon some of the outer roadways of the Manhattan Bridge previously(1996) and the City was pleasedwith the results.
According to NYC DOT DeputyDirector Walter Kulczycki, theoverlay replacement was intendedto extend the life of the deck byseven years, at which time the deck would then be replaced. However,during the Flexolith removaloperation (1998) it was found thatthe concrete ll was failing due toage, allowing corrosion to the steelgrid members. Due to dif cultiesin determining the extent of thecorrosion to the embedded gridmembers, the City decided toreplace the entire deck.
Design-Build ContractChosenOnce the re-decking decisionwas made, the decision to install
given the importance of keepingthis vital artery open during peak hours. And nally, in order to getthe project off the ground andcompleted as quickly as possible,the City invited ve design-buildteams, each comprised of rmswith considerable major bridgeexperience, to submit proposals.
Curved form pan restricted concrete, reduced weight in existing 1953 deck.New grid is standard 3” Tee design; use of lightweight concrete yields
weight neutral deck.
The city had used Design-Buildon projects as early as 1994, andconsidered them successful in that
both time and cost savings had been realized. Again, accordingto Kulczycki, Design-Buildwas selected to minimize thedelay inherent in the normaldesign-advertise-bid procedure.By using a Design-Build format,design work and detailed eldmeasurements began soon after the award. By April of 1999,
just 7 months after receiving anotice to proceed, design detailsand installation procedures were
nalized and structural steeland grid fabrication were wellunderway. The winning team,who submitted a price of $33.5million, consisted of the design rmWeidlinger Associates and general
contractor Yonkers ContractingCompany, Inc. of Yonkers, NY.
Design and ConstructionOptionsDeck dead load was certainly thecritical parameter in selecting areplacement deck. As far as can bedetermined, the existing deck wasa one of a kind system, speciallycon gured for the Brooklyn Bridge.It used a commercially available(in 1953) 3” deep I-Beam section,
between which inverted U-shaped pans were inserted. (See sketch.)It was supported by closely spacedrolled I-Beam stringers. Duplicatingthe existing deck was not possible,as the 3” I-Beam was no longer available. However, L. B. Foster Company supplies, on a regular
a 3” structural Tee instead of anI-Beam. This standard 3” oor waseventually chosen for use.
Also critically important wasa procedure that would allowinstallation of enough deck duringa 7 hour work window so that theentire bridge would have a newdeck in just 150 construction days,a contract requirement. One optioninvolved eliminating the stringersaltogether, and spanning between
oorbeams with the replacementdeck. The oorbeam spacing wasquite manageable (7.5’) and avariety of grid designs could have
been used to maintain the desiredweight. However, this wouldhave required modi cations tothe oorbeams (old riveted, trusselements) to support the deck, anoperation that was deemed tootime-consuming to accommodatethe demanding schedule. And witha $500 per minute penalty assessedfor not opening at 6:00 AM, timewas, as they say, of the essence.
What was chosen as most viablewas to replace the deck, preattachedto the stringers, seating those newstringers on the oorbeams utilizingexisting pedestals.
Deck DetailsBy using a lightweight concretemix, the standard 3’ Tee oor could
be used without any modi cation.And by specifying a “microsurface”overlay, the nished deck wasweight neutral with the previous
oor, had a smooth ride surfaceand was economical as well. Thesteel grid was hot dip galvanizedafter fabrication, a measure of corrosion protection not provided
AC Miller Company precast grid units, using lightweight concrete, in their Spring City, PA facility.
Longitudinal stringers supported by rivited truss foorbeams shown here
to the previous oor. In addition,the bottom surface of the deck, andthe new stringers, were painted.
Also, it should be pointed out thatthe existing oor, owing to theunusual design, had a concretethickness of less than 2” over much of it’s area (see sketch), andyet provided 45 years of service.The full depth concrete of the new
oor, with all surfaces coated,represents signi cant enhancementscompared to the previous design.According to Bolivar Sarmiento of Weidlinger Engineers, who playeda major design role in the project,the expected life of the replacementdeck is 75-100 years.
The Brooklyn Bridge has two 30’wide roadways, each carryingthree traf c lanes. The 3” Tee’s of the grid are transverse to traf c,supported by longitudinal stringerswhich are continuous over 4
oorbeam spaces, or 30’. Theconstruction plan, then, was for a
bridge crew to replace a 30’x 30’section of roadway each night. Inorder to accommodate module sizesthat could be handled within thetight con nes of the bridge, the 30’curb-to-curb roadway width wassupplied in 4 panels approximately7.5’. Commercially availablegalvanizing kettles were alsoeasily able to handle the 30’x 7.5’modules, which had a positive cost
impact on the project.
The steel grid manufacturer for this project was the FabricatedProducts Division of LB Foster Company, Pittsburgh, PA. Foster’srole, however, was much more thansimply a material supplier, as theywere fully responsible for both the
Grid end plates were bolted at longitudinal joint between stringer supports.
Below-deck work platforms important to timely completion of the project.
structural steel fabrication and the precasting operation. First, the grid panels were fabricated at Foster’sBedford, PA plant and shipped toIndustrial Galvanizers, Petersburg,VA. After galvanizing, panelswere sent to Metal Processing of America, Inc. of Brownsville, PA,where the panels were welded to
painted stringers. An importantstep in MPA’s process was theconstruction of full size xtures
Next, the stringer/deck moduleswere shipped to A.C. Miller Company, Spring City, PA for the
pre-casting operation. Like MPA,Miller also constructed extensive
xtures in order to insure proper t. After placing the panels into
the xture, both stringers and grid
to insure proper t-up of the four panels that comprise the 30’x 30’module.
were “squared” and bolted together.Opposite diagonal measurementsof the 30’x 30’ units were required
to be within a 1/2”. Once tted, a118#/CF lightweight mix, includingadmixtures, was placed into the
panels and given a rough nishush with the top of the grid using
a vibrating screed. The pouredconcrete was sprayed with a curingcompound, covered with plastic andleft in the xture for 24 hours. Theywere then transferred to an outsidestorage yard and covered with wet
burlap. Shipping was permittedonce concrete reached 4000 psi.
One key factor to the successfulinstallation of these units inan accelerated fashion was thelongitudinal joint. For this project,that joint was located betweenstringers. There, a bolted connectionwas designed to adequately jointhe two panels. Therefore, noquick-setting concrete was requireddirectly over the stringers, and theamount of quick-set required atthe bolted, longitudinal joint waslimited to small grid pockets. Manyfelt that this decision to locate the
joint between the supports wascritical, and enabled the contractor to open the bridge to traf c at 6:00AM every single day. At transverse
joints over the oorbeams the panels were also bolted together,except where relief joints were
located.
TimelineDuring daylight hours thecontractor was allowed to close onetraf c lane from 7 AM to 3 PM.This allowed for holes to be cutinto the existing deck in advance of nighttime removal.
At 11 PM, the project kickedinto high gear. First, traf c wasdiverted from the half of the
bridge where work was to be performed. (Nighttime traf c onthe Brooklyn Bridge was alwaysBrooklyn-bound, regardless of which side of the bridge was beingworked on. Manhattan-bound traf cwas detoured to the ManhattanBridge.) It should be noted that
NYC DOT provided about 30 traf cagents, located at various entrance/exit ramps, to insure continuoustraf c ow throughout. For the bulk of the project Yonkers used twocrews, each replacing a 30’x 30 areaof deck. At each work zone a single
piece of overhead bracing strut wasremoved, to allow suf cient roomfor the crane to handle modules.
Working from a moveable platform beneath the bridge, workers burnedthe existing bridge stringers off their “seats” on the oorbeams.
(Up to 70% of this cutting wasallowed to take place during theday, to enable timely removal thatevening.) Saws made longitudinaland transverse cuts; old sectionswere then removed.
With traf c diverted from half of the bridge at 11 PM, crews swunginto action. By about 1 AM a 30’section of deck had been removedand workers were busy grindingthe tops of the existing pedestals(seated on oorbeams) to receivethe new bridge stringers. Newmodules were then set in positionon the cleaned pedestals, newstringers were welded in place and
panels were bolted together. Using just 130 construction nights, theentire 3500’ x 60’ roadway of theBrooklyn Bridge was thus replaced.
This project brought together the talents and experience of many individuals, who overcame
Corrosion Protection for Grid Reinforced Concrete Bridge Decks
NOTE: The information contained hereinhas been prepared in accordance withgenerally accepted engineering principles.
However, L. B. Foster Company is notresponsible for any errors that may be contained herein. The user of theinformation provided herein shouldcheck the information supplied and makean independent determination as to itsapplicability to any particular project or application.
tremendous obstacles in serviceto the motorists of NYC. The
New York City DOT deserves
accolades for the commitmentthey demonstrated in keepingconstruction inconvenience to aabsolute minimum. Except for the construction signage that wasevident, a commuter who used the
bridge on a regular basis wouldnot have known that a major rehabilitation effort was underway.Spearheading the project teamfor the city was Assistant DeputyDirector for Bridge Design andConstruction, Walter Kulczycki.The lead Design Engineer for Weidlinger was Ron Mayrburl, and
Nobile Basile headed the effort for Yonkers.
Yonkers Contracting CompanyProject Manager Paul Schisler credits LB Foster Company, and theteam that Foster assembled, who
paid great attention to detail anddimensional issues, which assuredthat deck modules were installedeach evening without dif culty or delay.
One of three traf c lanes available to the contractor during limited daylight hours for preliminary saw-cutting.
