prize bridge award: reconstructed new yyork rroute 3367

There are approximately 19,000steel truss bridges in the UnitedStates, most of which were built over50 years ago and have not had thebenefit of regular, thorough cleaning.It was not until recently that bridgeowners gained an awareness andappreciation for a good inspectionand maintenance program. Cleaningstructures of de-icing salts and otherdebris was virtually unheard of in theearly years of these structures.Critical structural elements wereallowed to deteriorate as a “natural”course of events. Even under theseharsh conditions, many truss struc-tures have demonstrated the longevi-ty of steel as a building material bysurviving and performing satisfactori-ly for the better part of the past cen-tury.

With an increased effort placed oninspection and load rating, however,some of these bridges have been identi-fied as being structurally deficient andmarked for replacement. Because of theirage, it is often accepted that these bridgesare at the end of their useful life. Theproject described in this submission pro-vides credible evidence that this is notnecessarily true. Though a steel bridgemay be 60 years old, the employment ofnew technology, such as super-lightadvanced composite decks, can rejuve-nate and extend the service life of “tired”steel bridges a point the deck replace-ment at Bentley Creek illustratesperfectly.

PPrroojjeecctt OObbjjeeccttiivveeRemove the 14 Ton weight restriction

as quickly as possible to satisfy the pub-lic’s demand for highways withoutimpediments to local commerce.

PPrroojjeecctt DDeessccrriippttiioonnThe 1940s vintage bridge carrying

New York State’s Route 367 over Bentley

Modern Steel Construction / July 2000

NNeeww YYoorrkk RRoouuttee 336677 oovveerr

BBeennttlleeyy CCrreeeekkVillage of Wellsburg, New York

Prize Bridge Award: Reconstructed

Jurors Comments

...brings old iron together with new high tech

materials (FRP) to extend the service life of a

bridge in this quiet country setting. Innovative

concept to extend the life of old steel bridges...

Creek in Chemung County found new lifewith the installation of a lightweight fiberreinforced polymer (FRP) compositedeck. Though it was considered a primecandidate for replacement due to its age,condition and 14 ton weight restriction,the service life of the bridge has beenextended by an expected 30 years bymerely replacing the deck, performingsome minor steel repairs and painting thestructure.

A 32 psf FRP deck replaced the 170psf original concrete deck and excessivecourses of asphalt wearing surfaces thathad been added over the years. Becausethe new deck is radically lighter than theoriginal deck the bridge load ratingswere almost doubled, raising them higherthan the original design. This was possi-ble despite the fact that the structuralsteel had suffered some section loss andcorresponding loss of strength. A totaldead load of 265 tons was removed.

The deck itself rates much higherthan the bridge. It meets a L/800 deflec-tion requirement with an inventory loadrating of HS85 (154 tons). Proof testsindicate that the actual load capacity ofthe deck is even greater than these ana-lytical ratings.

The entire rehabilitation project wasconducted by the New York StateDepartment of Transportation’s (NYS-DOT) in-house maintenance staff overthe course of two construction seasons.During 1998, the old deck was removed,areas of extreme section loss wererepaired and a temporary steel grate deckwas installed. In 1999, after the structurewas painted under contract, the tempo-rary deck was removed and replaced bythe FRP deck. The deck replacementoperation was completed in less than 30calendar days, proving that rapid installa-tion would be a huge benefit in urbanareas where it is especially desirable tominimize disruption to traffic.

UUnniiqquuee aassppeeccttss ooff tthhee pprroojjeeccttThe project was the first application

of a FRP deck on a truss bridge on a statehighway system. Due to this lack ofprecedence, many innovations weredeveloped, these included:

• Deck to steel attachment—a pre-castpolymer concrete haunch with a boltedconnection between the floor beams andthe deck;

• The sizing and design of the decksection to match “existing” thickness sothat approach modification was mini-mized;

• Eliminating the need for using theexisting stringers for support; 4. modulardeck assembly (6 panels covering a 25’ ×141’ area);


• Load carrying deck panel splicedetails;

• FRP curb (behind the steel boxbeam railing); scupper frames cast intoFRP deck;

• FRP sidewalk (which reduced thedead load by 32 tons); and

• Field cut FRP filler panels betweenthe deck and sidewalk to protect the bot-tom truss chord from water intrusion,prolonging the life of the structure.

BBeenneeffiittssA deck replacement can be done in

much less time than a bridge replace-ment project, therefore reducing the neg-ative economic effect felt by local usersand improves safety. Deck replacement isalso done with less environmental impactby eliminating any in-steam channelwork and disturbance to vegetated areas.The strategy may be able to be used tosave an otherwise obsolete structure. Incases where the structure has historic sig-nificance, it can make rehabilitation afeasible alternative when it might nothave been previously. A comparison ofactual costs to replace a similar truss sug-gests that there is substantial economicbenefits as well. The value of this projectwas $876,0001 versus $2.3 million fordesigning and constructing a similarlysized truss replacement.

The benefits of installing a FRP com-posite deck onto a steel truss bridge aremanifold:

• Shortens project development timeto implementation;

• Dramatically improves load ratings; • Removes a hindrance to local com

merce;

• Protects structural steel from theweather;

• Improves feasibility of rehabilitatinghistoric structures;

• Short duration, less disruption totraffic, affecting goodwill, economics, andsafety;

• Environmentally friendly; • Cost savings over replacement; and •Extends service life with minimal

effort. Though the amount of new structural

steel was minimal on this project, thesuccessful rejuvenation of this 60 yearold truss makes a convincing argumentthat steel is a very durable and long last-ing construction material.

Project TeamOwner:

New York State DOTDesigner:

Wagh Engineers, P.C.Steel Erector:

New York State DOT BridgeMaintenance

General Contractor:New York State DOTMaintenance

The new CSX Bridge spans overthe Tennessee River Slough atBridgeport, Alabama and is a modernsingle-track railroad structure, 1469’in length, with ten simply supported,steel composite deck plate girderspans and a ballast deck. The bridgeis located on the CSX Nashville-Chattanooga main line, an sees anaverage of 27 trains per day.Bridgeport is located in the northeastcorner of Alabama, approximately 30miles downstream from Chattanooga,Tennessee. The new bridge replacesan historic deck truss structure on aseparate parallel alignment.

The new span layout has two endspans at 147’2” and eight interior spansat 146’10” between piers. The actualgirder span between bearings is typical inall ten spans, and is 144’0”. The steelsuperstructure is a redundant system withfour deck plate girders spaced on 4-ft.centers that are composite with a rein-forced concrete deck. The girders are9’4” deep and use ASTM A709 Grade50W weathering steel.

The substructure consists of hammer-head piers with circular columns foundedon steel H-piles. Each pier column is7’6” in diameter with an average columnheight of 45’. The geology of the site iskarstic with variable weathering of lime-stone and dolomite. The rock is variableand contains voids that are filled withsoil. Due to the variability of the rockand soil, dynamic testing of piles wereused to verify pile capacities. Piles weredriven to lengths of up to 200’ in somelocations. The use of steel piles wereshown to be very effective in developingrequired bearing capacity and in havingsplicing capability to accommodate thevariable rock profile.

Overall, this state-of-the-art railroadbridge design incorporated strength,function, economy, safety, constructabili-ty and aesthetics. Specific innovative fea-tures that were included are:


CCSSXX BBrriiddggee oovveerr

TTeennnneesssseeee RRiivveerr SSlloouugghhBridgeport, Alabama

Merit Award: Railroad

River is an economical and aestheticallypleasing design with low maintenanceweathering steel girders and slender cir-cular pier columns. It combines therequired strength, function and service-ability with a clean slender appearancethat blends well with the natural riverenvironment and wooded riverbanks.

• Use of Grade 50W weathering steelfor initial economy, long term low main-tenance and aesthetics;

• Use of bolted stiffener and bracingconnections for improved fatigue resis-tance;

• Use of four girder system for redun-dant fatigue and fracture considerations;

• Use of solid plate diaphragms withaccess holes for ease of fabrication;

• Use of dual inspection walkwayswithin outside girder panels for ease ofaccess and inspection;

• Use of uniform girder span layoutfor economy of repetition;

• Use of economical span lengths forplate girder design, balancing superstruc-ture and substructure costs;

• Use of circular reinforced concretepier columns for strength, hydraulics andeconomy.

The existing bridge is an historicstructure, and will be kept and main-tained by the city of Bridgeport as apedestrian bridge providing access to anisland in the Tennessee River at thislocation. The bridge was originally con-structed in the early 1850s and has por-tions of the original masonry piers andabutments still in use. The originalbridge had timber trusses and has beenmodified several times over the years.During the Civil War, the bridge was thefocal point of several conflicts betweenUnion and Confederate forces vying forits strategic importance in transportationand communication. The bridge super-structure was destroyed and rebuilt twiceduring this period. Five of the deck trussspans were reconstructed last in 1910,and the other four spans in 1930. Theseexisting spans are all steel pin-connecteddeck trusses. General bridge deteriora-tion and related high maintenance costshave lead to the need for replacement.The new plate girder bridge built alongside the old historic truss bridge illus-trates the state-of-the-art in modern rail-road bridge design as contrasted by theslender clean lines of the new and thedeep busy appearance of the old.

Numerous other environmental issueshad to be mitigated in order to obtain apermit for the new bridge includingavoiding two archaeology sites adjacentto the new alignment on the island, wet-land impacts on the island and threat-ened and endangered species impacts inthe river.

Final design was completed inFebruary 1997, and the constructioncontract was awarded in April 1997.Construction began in May 1997 and wascompleted in November 1998.

The CSX Bridge over the Tennessee


Project TeamOwner

CSX TransportationDesigner

HDR Engineering, Inc.Steel Fabricator

Carolina Steel CorporationSteel Detailer

Carolina Steel CorporationSteel Erector

Scott Bridge Company, Inc.General Contractor

Scott Bridge Company, Inc.

The bridge provides a connectionbetween two extensive city trail systems.That system includes a trail system thatparallels the river and connects to anextensive city-wide network of non-motorized facilities. Even though this isthe site of a previous bridge crossing, thelocation was re-evaluated to verify thatCalifornia Street was still the optimallocation for the bridge. The preferred siteand type of structure was determinedthrough an extensive consultant led pub-lic involvement process involving theentire community. Once the structuretype and location had been determinedthen detailed plans were developed toconstruct the project. The study andenvironmental assessment began in 1996.Construction of the bridge started in thefall of 1998. It was dedicated and openedto the public in October 1999.

AApppplliiccaattiioonnss ooff TTeecchhnnoollooggyyWhile cable-stayed structures are not

a new construction method, this choicewas selected for this site because it pro-vided both a cost-effective method tospan the river at this location and an aes-thetically pleasing structure. The use ofcable-stay in combination with a steel

M issoula is known asMontana’s bicycling town. The city ofMissoula has long been a supporterof non-motorized transportation, andhas been proactively developing asystem of trails, bike-lanes and side-walks. A bicycle/pedestrian bridgeacross the Clark Fork River has beena need in this area of town since anaging structure was torn down at theCalifornia Street location in the mid-1980s. Additionally, the river hasbeen a substantial obstruction totravel about town for wheelchairusers. In 1996 the city of Missoulahired our firm to perform a study ofconstructing a new bridge. Thatstudy evolved into the design of theCalifornia Street Bridge project.

The project consisted of the construc-tion of a new bicycle/pedestrian bridgeand included the following key elements:

• Developing and evaluating alterna-tives;

• Preparing an environmental assess ment; and

• Preparing construction documents.


CCaalliiffoorrnniiaa SSttrreeeett BBrriiddggee

Missoula, Montana

Merit Award: Special Purpose

truss permitted the resulting structure tobe relatively thin for the 400’ span cross-ing. This also proved to be less costlythan other options investigated in theconceptual stages of the project. It wasestimated that the structure cost 30% lessthan a more conventional bridge design.

The construction staging and assem-bly areas available for use were limited.Use of the truss bridge design permittedassembly of major elements either on theground or off site. The could later beassembled over the river. The design wasaccomplished so that the superstructureelements of the truss, floorbeams anddeck could be constructed incrementally.The truss portion was designed to be self-supporting, to facilitate erection and topermit the connection of the cable-stayedportion after bridge erection and beforecasting of the concrete deck surface.

TTeecchhnniiccaall VVaalluueeThe use of the truss in combination

with the cable-stayed method of supportdemonstrates the ability to erect a bridgeover a very large river without use ofunusually large equipment or disruptionto a sensitive river setting. The incremen-tal construction method was also impor-tant in that it facilitated the constructionand minimalized the disruption to thesurrounding land users. The elements ofa composite concrete deck, steel trussesand the cable-stays act integrally to pro-vide the efficient use of materials withinthe structure.

SSoocciiaall aanndd EEccoonnoommiicc CCoonnssiiddeerraattiioonnssMissoula is known as Montana’s bicy-

cling town because of its extensive use ofnon-motorized forms of transportation.Missoula is home to the University ofMontana which also generates significantinterest in pedestrian and bicycle usewithin the community. This crossing pro-vides a critical route for residents travel-ing between residential areas of Missoulato the downtown area. This bridge alsoserves as a key link in the non-motorizednetwork that serves the University andother areas of town.

required careful planning and execution.The site had limited area to use for

staging the construction. The design wasdeveloped to permit segmental erectionof the structural elements. This permittedthe partial assembly of large pieces priorto erecting them over the river. The trusswas erected in four pieces and boltedtogether over the river and the cable-stays fastened afterwards.

MMeeeettiinngg tthhee OOwwnneerr’’ss EExxppeeccttaattiioonnssThe Owner had limited funds with

which to erect this structure. Yet theywanted an attractive structure that wouldenhance this area and attract people tothe trail system. They also faced signifi-cant public concern over the aesthetics ofthe new bridge. All of these hurdles wereover come as a result of the consultant’sapproach to the public involvement anddesign processes. The resulting structureis about 30% less costly than other avail-able options. It has resulted in a spectac-ular looking structure that supports apedestrian live load of 85 lbs. psf.

The bridge is also located near a largeapartment complex used by people whoexperience mobility impairments. Thetrail system and bridge design permiteasy access for wheel chair bound usersto cross the river. Prior to constructionof the bridge these users were restrictedto using buses or some other vehicle tocross the river because of the lack ofother wheel chair compatible crossings.

The bridge was sponsored by thecity’s Redevelopment Agency to increasethe city’s pedestrian trail system and isviewed as a vital link to revitalizing theriverfront area in Missoula. The bridge isa critical link between trail systems thatextend widely on each side of the river,as well as up and down its shores.

The selection of the location andbridge type were both key elements ofthe design process. The city’s objectivewas to involve as much of the communityas possible in the process so that accep-tance and use of the bridge would bemaximized. Our team made extensive useof computer based visualization methodsto provide the public with technicallyaccurate views of how different types ofbridge structures would appear at variouslocations. Several innovated public coor-dination efforts were conducted wherecitizen input was solicited to develop theconcepts for the structure. The citizensactually provided input for the type andlocation they preferred. The final selec-tion was made and computer generatedrenderings completed prior to construc-tion. The actual structure duplicates theconceptual plans developed in the earlystages, from the detail of color to majorelements.

CCoommpplleexxiittyyThe design of the foundations, espe-

cially the center pylon foundation,required careful design and planning totake advantage of an island in the river.Each support is founded on drilled shaftconcrete foundations. Earlier attempts onother projects to use this type of founda-tion along the Clark Fork River inMissoula had resulted in significant costoverruns when large boulders wereencountered in construction, this timespecial care was taken to properly locateand design them to minimize possibleconstruction problems.

The erection sequencing had to bedeveloped in detail to balance the con-struction loads on the truss and cable-stayed elements. A casting pattern wasdeveloped to cast the concrete deck ofthe bridge without displacing the truss.Tensioning of the cables to provide thecorrect profile for the bridge deck also


Project TeamOwner

City of MissoulaDesigner

Carter & Burgess, Inc.Steel Fabricator

Egger Steel CompanySteel Detailer

JDB DetailingSteel Erector

Iroquois Industrial, Inc.General Contractor

Bodell Construction Co.

The original Bloomington FerrySwing Bridge was closed in 1976 dueto structural deterioration and rebuiltin 1977 with a new superstructure onthe original center pivot pier andabutments. This bridge was closed tovehicular traffic in 1995 andreplaced with the new TrunkHighway 169 (TH 169) crossing overthe Minnesota River approximatelyone-half mile upstream.

As part of the Minnesota Valley StateTrail System a pedestrian/bicycle cross-ing over the Minnesota River was origi-nally planned to be incorporated into thenew TH 169 river crossing. However,during the Environmental ImpactStatement process conducted as part ofthe TH 169 project, the U.S. Fish andWildlife Service and the MinnesotaDepartment of Natural Resources indi-cated that the new TH 169 crossing wasnot a suitable environment for pedestri-ans and bicyclists. These agencies recom-mended that the trail cross the MinnesotaRiver elsewhere. The decision was madeto use the old Bloomington Ferry Bridgeas a pedestrian/bikeway bridge. However,the existing bridge, if utilized, wouldhave required a great deal of renovationand maintenance to remain in use.Estimated costs associated with this workled to the conclusion that repairing andrenovating the old bridge was not a cost-effective, long-term solution. Therefore,the decision was made to construct a newpedestrian/bikeway bridge at the locationof the old Bloomington Ferry Bridge.

A bridge type study was prepared forthis location and proposed several struc-ture types and aesthetic treatments.Several site constraints had to be over-come for this project, including:

• developing a structure that providedan unrestricted opening for theMinnesota River (the old bridge, with itscenter pier, caused problems with iceflows and mobility of boaters);


BBlloooommiinnggttoonn FFeerrrryy

PPeeddeessttrriiaann BBrriiddggeeShakopee, Minnesota

Merit Award: Special Purpose

abutments and piers and decorative orna-mental metal railings were utilized.Unpainted weathering steel was chosenfor the girders. The use of unpaintedweathering steel girders enabled thedesigners to satisfy the need for both afunctional and aesthetically pleasingstructure, with clean lines, that will com-plement the heavily wooded natural set-ting in which the bridge is located.

This project utilizes a conventionaltype of bridge structure in an innovativeuse of span lengths and formed shape. Aspan length of 255’ for the center spanpushes the limits for a conventionalpedestrian girder. This use of simple con-ventional methods of a counterweightand a thick end span deck to overcomethe uplift forces at the abutments allowedthe designers to maximize the centerspan length while utilizing simple andeasy methods to overcome difficult erec-tion and construction issues.

An important aspect in bridge engi-neering is the use of materials in the cor-rect shapes and proportions for the specif-ic site location. This project achieves thatgoal at this environmentally sensitive area.

• keeping the proposed structureabove the 100-year flood elevation;

• wide seasonal fluctuations in riverelevations;

• maintaining difficult site grades andmeet current bicycle design standards;and

• retaining aesthetic views of this envi-ronmentally sensitive area within theMinnesota Valley Wildlife Refuge.

A three-span parabolically archedwelded steel plate girder structure with acast-in-place concrete deck was selectedfor the site. In order to fit the site con-straints of the river banks, and the needto provide an unrestricted opening forthe Minnesota River, span lengths of 90’-255’-90’ were selected. This end spanratio of 0.35 created a difficult upliftproblem for the designers to overcome.Several options were developed and eval-uated during the design process toaccount for the uplift. The chosen solu-tion was a combination of a concretecounterweight at the abutments and athickened concrete deck in the endspans. This solution required the design-ers to provide a construction sequence toassist the contractor. During erection ofthe beams, the contractor was required toprovide a temporary tie-down system atthe abutments until the counterweightswere poured.

The steel girder consisted of a para-bolically arched bottom flange and variedfrom a web depth of 66” at the centerspan and abutments to 120” at the piers.Due to the Minnesota River’s wide sea-sonal fluctuation in river elevations, thecontractor constructed cofferdams tofacilitate construction of the piers, whichwere located at the edges of the river.Even with the aid cofferdams, the con-tractor was unable to work in the river atvarious times due to seasonal flooding.

To complement the aesthetics of thisproject site, cut stone treatments on the

Project TeamOwner

Minnesota Department ofTransportation

DesignerSRF Consulting Group

Steel FabricatorPDM Bridge

Steel DetailerTrevian Projects LTD.

Steel ErectorHigh FIve Erectors, Inc.

General ContractorLunda Construction Co.

Improvements to Garden StateParkway Interchange 159 in BergenCounty, New Jersey, provide a much-needed direct connection betweenthe southbound Garden StateParkway and eastbound I-80, animportant commuter route to NewYork. Previously, this was a cir-cuitous route taken either throughseveral local streets or via NJ Route17. This project has relieved severepeak-hour congestion on local streetsas well as regional congestionextending to NJ Route 17.

The new ramp alignment includes aneight span, continuous, sharply curved,and horseshoe-shaped 834’ long curvedmonocell steel trapezoidal box girdersuperstructure with a radius of 230’.

Opened to traffic in January 1998,this bridge is the first monocell box gird-er vehicular bridge in New Jersey. Thesolid stainless steel reinforcement used inits deck was also another first in NewJersey. This usage represents the largestquantity of stainless steel reinforcementin a transportation project in the UnitedStates.

The project was completed six monthsahead of schedule and at a total cost of$8,339,000, less than one percent overthe bid amount of $8,260,000. This slightincrease was due to additional roadwaybarriers.

Several innovative features wereincorporated into the project to addressthe many challenges posed during designand construction phases. Providing forthermal movements without introducinglarge stresses was a major challenge insuch a sharply curved structure. Thesuperstructure was designed with fixity atthe abutment ends only, therefore allow-ing for unrestricted thermal movementsat all other interior supports. At the sametime, seismic movements and forces hadto be accommodated without penalizingonly the abutments. We developed amethod that would both engage one ofthe interior piers to share seismic forces


GGaarrddeenn SSttaattee PPaarrkkwwaayy

IInntteerrcchhaannggee 115599Bergen County, New Jersey

Merit Award: Short Span

Project TeamOwner

New Jersey HighwayAuthority (Garden StateParkway)

DesignerParsons Brinckerhoff-FG

Steel FabricatorTampa Steel Erecting Co.

Steel DetailerTensor Engineering Co.

Steel ErectorArcher Steel ConstructionCo., Inc.

General ContractorsRailroad Construction Co.(The RCC Group)

while still allowing for design thermalmovements. The deck slab is the topflange of the box structure and for eco-nomics, a non post-tensioned reinforcedconcrete deck slab was also specified.Recognizing that future deck slabreplacement would be impossible withoutclosing the bridge a new method toextend the life of the deck was necessary.This resulted in the use of solid stainlesssteel reinforcement for the deck slab at asmall increase in initial cost.

Community involvement meetingswere held and a great effort was expend-ed to assuage the concerns of the severalimmediate neighbors to the project. As aresult, restricted hours for steel H-piledriving, monitoring vibrations during piledriving and the construction of a perma-nent detour route for oversized vehicleson an adjacent property were all incorpo-rated. Special architectural treatmentswere specified within the substructure inorder to enhance the appearance of thebox girder, and paint schemes were care-fully considered to achieve the best adap-tation of the structure to the environ-ment.

This complex yet aesthetically pleas-ing structure was built well ahead ofschedule due to the environment ofteamwork that prevailed among thedesigner, client, and contractor for theentirety of the project.

The first curved steel monocell boxgirder vehicular bridge in New Jerseywas successfully constructed with no sig-nificant problems and opened to traffic,providing a much needed link betweentwo major commuter routes.

The Garden State Parkway (GSP) is,at once, both a major north-south routeon Interstate Route I-80, as well as amajor east-west route intersect in BergenCounty—a densely populated area ofnorthern New Jersey. Until completion ofthis ramp, the southbound GSP had nodirect connection to eastbound I-80. Theprevious, indirect circuitous connectionwas through several local streets and sig-nalized intersections, or via NJ Route 17,another heavily traveled commuter route.This created a source of severe morningpeak hour congestion on the affectedlocal streets. Regional traffic on thealready congested NJ Route 17 was seri-ously affected by commuters bound forNew York who used Route 17 to accessRoute I-80. Various studies firmly estab-lished the need for a direct link betweenthe two arteries.

The new direct connection ramp fromthe southbound GSP to eastbound I-80 isan extension of the existing off-ramp atInterchange 159. The new ramp passes


under the I-80 bridge in the western-most span, runs parallel to the south-bound GSP and curves sharply in a loopto connect with eastbound I-80. The sin-gle lane ramp crosses over a light indus-trial area on a sharply curved viaductwith a 230’ radius.

The new off-ramp crosses the existingI-80 overpass structure under its westerlyspan. The existing west abutment is astub abutment on steel H-piles. The frontrow of piles is battered and the verticalunderclearance in this span is limited.Therefore, retaining the large sloped fill,in order to construct the new ramp,posed another challenge. This was over-come by construction of a cast-in-placesoil nailed retaining wall, another first inNew Jersey roadway construction.

The ramp structure is an 875’ long(measured along the centerline) horse-shoe shaped eight span continuous steelmonocell trapezoidal box girder madecomposite with a cast-in-place reinforcedconcrete deck slab. The 24’ roadway issuperelevated at 6% and has 1’6” barriercurbs on each side. The box girder webplates are spaced at 12’6” on centers atthe top, resulting in 7’3” wide deck over-hangs.

The span arrangement (measuredalong the bridge centerline) consists of

six interior spans of 118’5” each with endspans of 78’9” and 85’9”. The verticalprofile of the ramp is a constant 0.5%upgrade ascending from the GSP toRoute I-80 EAST BOUND.

The semi-stub abutments are conven-tional reinforced concrete, supported on140 ton capacity steel H-piles. Taperedsolid wall piers, shaped to accentuate thetrapezoidal shape of the superstructure,also have special architectural surfacetreatment.

T he Merritt Parkway was originally constructed between 1934and 1940. The design of the parkwayincluded more than 70 bridges. TheMerritt Parkway got its name fromCongressman Schuyler Merritt, whowas one of the highway’s earliest andmost persistent advocates. The intentof this parkway was to provide aclear and unobstructed drive in a“park-like” setting from theHousatonic River in Stratford,Connecticut to the New York stateline that was free of heavy commer-cial trucks.

To go along with the parkway theme,a Highway Department staff architectnamed George Dunkelburger designedthe facade of each bridge. The designsrange from Neoclassical to Art Dec. Notwo bridges along the parkway have thesame design, but many features such asthe State Seal are duplicated. Most of thebridges are rigid frame structures thatwere designed to provide slender linesmeant to prevent the steel frame fromcompeting with the architectural featuresof each design. These bridges are a mon-ument to the art of combining form andfunction.

The bridges of the Merritt Parkwayhave been celebrated for many years bythe citizens of Connecticut. They havealso been awarded the status of being list-ed on the National Register of HistoricPlaces. At this time, many of the bridgesare reaching the end of their service life.This has brought about a need for reha-bilitation of these beautiful structures.

RReehhaabbiilliittaattiioonn NNeeeeddThe condition of the 65 year old

bridge had become a concern, althoughthe real driving force behind the projectwas the need for acceleration and decel-eration lanes on the parkway. Thisrequired the widening of the bridge oneach side in order to accommodate thenew lanes. The widening consisted of17.75’ extensions of the original bridge.The original bridge framing was salvagedand re-painted and the original abut-ments were also rehabilitated. The newbridge extensions would cover all of the


MMeerrrriitttt PPaarrkkwwaayy oovveerr RRoouuttee 112233Norwalk, Connecticut

Merit Award: Reconstructed

riveted frame was constructed with ahaunched section. This not only provideda slender flowing profile, but it also mim-icked the moment diagram of the bridge.This variable haunch allowed the designof the new frame to include a constantflange cross section over the entire lengthof the frame (including the vertical legs).This greatly reduced fabrication expensesby eliminating flange transition splices.

Hidden Bolted Field Splices: The orig-inal design of the Route 123 Bridgeincluded field splices located near theinflection points along the span. This wasnot a visual problem since the splicerivets were visually lost in the continuousriveting of the structure. The new struc-ture is a welded steel frame that is veryclean in profile. The design was modifiedfrom the original by shifting the boltedsplices down into the column legs thatare cast integral with the abutments. Thisprovided a clean bolt free look to the fas-cia frame. The designers feel that had theengineers of the 1930s had modernwelding technology available to themthey would have opted for this type ofclean design.

Welding Details: The design of a rigidframe requires the development of detailsthat are not common to conventionalmodern stringer bridges. The elbow andbase plate details carry significantmoments. The design team wanted toavoid sharp angle point connections atthe elbows in order to limit the possibilityof stress concentrations. The resultingcurved flange elbow joint has a combina-tion of ring compression and ring tensionthat induces compression forces in theweb. Diagonal stiffeners were designed tocarry these forces between the flanges.The base plate moments had to be trans-ferred from the relatively small flanges

into a large base plate. A design weldinga simple base plate on the end of theframe would require a very thick plate inorder to accommodate the large bendingstresses in the base plate. By designing astiffened base plate the anchor bolt forcesare transferred to the flanges throughvertical fillet welds in place of trying totransfer force through the base plate.The design of the elbow and base platewas based on information published inOmer W. Blodgett’s book, Design ofWelded Structures.

AAeesstthheettiicc CCoonnssiiddeerraattiioonnssThe Route 123 Bridge, as well as the

entire Merritt Parkway, is listed on theNational Register of Historic Places. TheConnecticut DOT has made an effort inthe last ten years to maintain, restore andpreserve the historic character of thelandscape and bridges. Many citizens ofthe area are familiar with each individualbridge along the parkway with theirunique features ranging from ornamentalironwork of fig leaves, to castings ofPilgrims and Indians, all of which pro-vide a whimsical experience while driving the parkway. The design of theRoute 123 Bridge frame provides slenderlines that are inconspicuous and unob-trusive. It is well known among architectsthat dimensional scale of structural ele-ments is a key feature as to how a structure is interpreted.

The structural frame with thehaunched webs is an important part ofthe aesthetics on the Route 123 Bridge.The Maryland DOT Aesthetic BridgesUser Guide states that, “Haunches areimportant visually because they make thebridge seem thinner by reducing theaverage depth while leaving the length

original architectural features of thebridge, therefore it was decided to repli-cate the features of the original bridgewith modern building material such aswelded steel.

Some thought was given to re-creatingriveted steel frames to exactly match theoriginal, but it was felt by the designteam that if George Dunkelburger hadthe use of modern welded steel he wouldhave used it.

BBrriiddggee IInnffoorrmmaattiioonnThe Route 123 Bridge is a single span

rigid frame structure with a reinforcedconcrete deck. The approximate dimen-sions and information about the bridgeare as follows:

• steel rigid frame with integral abut-ments;

• span: 66’; skew: 38 degrees;• six original riveted steel frames spaced

at 11’;• four new welded steel frames spaced

at 9’;• frame web depth at abutments: 3.5’;

and• frame web depth at mid-span: 1.5’.

IInnnnoovvaattiivvee DDeessiiggnn FFeeaattuurreessThe Route 123 Bridge is not a typical

highway structure. In a day wherestringer span bridges are the norm, thisbridge stands out as a unique and sophis-ticated structure. The original bridge wasconstructed in the 1930s. It has manyunique features that had been lost overthe years where lowest possible costdesigns won out over more innovativeand more visually appealing designs.

Integral Abutments: Many states aremoving in the direction of jointlessbridge design using integral abutments.Recent articles have stated that jointlessbridge technology was pioneered in the1950 in several states. The Route 123Bridge was designed and built almosttwenty years before these more modernjointless designs. The bridge has func-tioned well for over 65 years, which isthe greatest test to this technology.

Rigid Frame Design: The structuralsystem of the Route 123 Bridge consistsof a single span steel rigid frame. Thereare many advantages to this type ofdesign. The foremost advantage is theability to produce very elegant slenderstructural members over the span. TheRoute 123 Bridge has a mid-span frameweb depth of only 18”. This is remark-able considering the span is over 66’ andthe frame spacing is 9’ on center.

Haunched Web Profile: The original


the same. Haunches visually demonstratethe flow of forces in the bridge.” Thesteel frame on the Route 123 Bridgeachieves this aesthetic standard. The steelframe is clean and simple and it does nottry to compete with the architectural finishes on the parapets and wing walls.

SSuummmmaarryyThe following items summarize the

design of the Route 123 Bridge:

• The design includes a steel rigidframe structure that is cast integralwith the abutments.

• The frame design with the haunchedweb produces a constant flange sizeand a mid-span depth of only 18” fora 66’ span.

• The bolted splices are concealed with-in the integral abutments.

• Unique stiffening details were devel-oped at the frame elbows and baseplate.

• The bridge was designed to replicatethe original historic structure usingmodern steel fabrication techniques.

Project TeamOwner

Connecticut Department ofTransportation

DesignerConnecticut Department ofTransportation

Steel DetailerJohn Metcalfe Company

General ContractorWatertown ConstructionCompany

The 200’ Franklin Square Bridgeis part of the Manhattan approach tothe Brooklyn Bridge. Due to itstrapezoidal span, each of the six pin-connected eyebar trusses that sup-port the bridge have a different span.Since 1883, various alterations haveincreased dead load significantly.Preliminary analysis suggested, andsubsequent sophisticated analysisproved that, the bridge wasn’t safe.The New York City Department ofTransportation (NYSDOT) issued anemergency contract for retrofit to theconsulting engineer who performedthe analysis. The final designemployed six steel arches foundedinto the original masonry abutmentsto support the six wrought iron truss-es.

Replacing the trusses was ruled out bythe client because of the bridge’s historicimportance; in addition, the bridge hadto remain open. The restoration of anhistoric structure was accomplished in anemergency situation and under stringenttraffic restrictions. The client’s requestthat the consulting engineer use arches tosupport existing trusses was unusual, aswell as adding additional complexity. Theengineer’s design neither altered norcompromised the elegant appearance ofRoebling’s original structure, despite itscomplex geometry and outdated materi-als.

The Manhattan approach to historicBrooklyn Bridge incorporates a 200’bridge over Franklin Square inManhattan at the junction of Pearl andCherry Streets. The bridge’s supportingstructure consists of six pin-connectedeyebar trusses. Each truss has a differentspan, because the bridge is trapezoidal inplan. Transit tracks, supported on anopen steel structure, were removed andreplaced with a reinforced concrete deck.The original Belgian block roadways andwooden pedestrian promenade in thecenter were both replaced with thickerconcrete decks.

In preparing a design for the re-deck-ing of the Brooklyn Bridge approaches,the engineering consultant performed ananalysis of the Franklin Square Bridgeusing the current dead load. Appearancesto the contrary, it revealed that the


FFrraannkklliinn SSqquuaarree BBrriiddggeeBrooklyn, New York

Merit Award: Reconstructed

Project TeamOwner

New York City DOTDesigner

Weidlinger Associates, Inc.Steel Fabricator

Harris Structural Steel Co.Steel Detailer

Graphics for Steel StructuresSteel Erector

Koch Skanska, Inc.General Contractors:

Koch Skanska, Inc.

nificantly to the complexity of the pro-ject. The results more than made up forthe challenge of the arch solution: theappearance of the bridge was improvedby adopting this scheme over the originalgirder scheme.

IInnnnoovvaattiioonnThe arches, in which no members

were perpendicular to any other mem-bers, were an extension of Roebling’scomplex geometry.

One way to conceptualize the designapproach is to visualize that the originalsteel trusses of the Franklin SquareBridge were supported on falsework fromunderneath during construction. In the1999 retrofit design, the engineering con-sultant used steel arches as permanentfalsework to support the historic struc-ture above. The trapezoidal plan of Thebridge required arches with six differentspans, reflecting the six different trussesabove, ranging from 147 to 190’.Furthermore, the panel points on thetrusses above were arranged in a patternthat was skewed to the axis of the bridge.The truss verticals, which were strongcompression members directly support-ing the floor beams, were used as the ele-ment into which a vertical force wasintroduced to relieve the trusses. Becausethe pattern of these vertical members wasskewed to the bridge the posts set on topof the arch had to conform to this pat-tern.

The singular arch geometry, with vir-tually no members perpendicular to anyother members, was a detailer’s night-mare. Usually, the floor beams on askewed bridge are made perpendicular tothe main carrying members to simplifythe geometry. Roebling was not so kindas to retrofit engineers, who had toextend the geometry of his originaldesign into the much more complexgeometry of an arch structure.

RReessppeecctt ffoorr OOrriiggiinnaall DDeessiiggnnThe advantages of working within the

limits of Roebling’s geometry were that itmaintained the appearance of the bridgeand visually enhanced the unequal cur-vature of the arches. The arches added acurvilinear element to the structure thatcontrasted with the lattice of the wroughtiron trusses and are reflective of themasonry arches crossing other streets.Working with the client, a color schemewas selected to delineate new structurefrom old, so that the historic and retrofit-ted portions were easily identifiable.

Arches were composed of three ele-ments to facilitate erection and designedto stand alone.

bridge trusses were overloaded.Alterations made to the bridge over itslifetime, to accommodate an increase inthe volume of vehicular traffic, hadincreased dead load significantly.

John Roebling designed the trussmembers of the Franklin Square Bridgeas part of his original Brooklyn Bridgescheme using materials that date to thatera. The trusses were made of wroughtiron common for the 1880s, but nottoday. Since wrought iron offers excellentductility and consistent strength, and hassuperior resistance to corrosion, thebridge was able to sustain the increase ofapplied loads without incident since1883, its trusses showing no visible signsof distress.

The pins connecting the truss mem-bers were made of carbon steel, a fore-runner of today’s A36 steel. In the simpleelastic analysis requested by the client,some of the pins were found to bestressed beyond the yield threshold and,in some cases, beyond the full plasticmoment capacity. The lack of visible dis-tortion in the pins suggested that a redis-tribution of the forces in the eyebars wastaking place. The engineering consultantdeduced that there was reserve strengthnot indicated by the preliminary analysis,which was insufficient to determine theactual safety of the bridge.

The engineering consultant chose toperform a more sophisticated sequentialfailure analysis, because of the uncertain-ties involved. The loading was increasedin steps until overall yield of the bottomchord was reached. The results of thisanalysis showed that the reserve againstfull yield was inadequate. NYSDOTissued an emergency contract to the engi-neering consultant for design and con-struction of a retrofit to provide adequatesupport for the increased loads.

AAeesstthheettiicc aanndd TTeecchhnniiccaall CCoommpplleexxiittyyIn addition to meeting safety require-

ments the retrofit structure would haveto be attractive, in keeping with the ele-gance of the original bridge. It was giventhat the original historic trusses shouldnot be altered in appearance. Replacingthe trusses was ruled out for another rea-son: the bridge had to remain open totraffic.

The final design employed six steelarches spanning the full length of thebridge to support the original six wroughtiron trusses; the arches were foundedinto the original masonry abutments.While steel arched bridges are notuncommon, the client’s request that theengineering consultant use arches to sup-port the existing trusses, in order to mini-mize traffic interference and for aestheticreasons, was unusual and contributed sig-

It was desirable that all the arches besprung at the same elevation and that thecrowns be as close as possible to theexisting structure above. As a result, thearches all had different radii. Each archwas composed of three elements, whichwere spliced together in the field to facil-itate erection. The arches were designedas three centered arches with the radiichanging at the splice points and selectedto approximate a parabolic shape. Inorder to reflect the solid plate top chord,the arch ribs were I-sections fabricatedfrom steel plate; bracing and columnswere rolled sections with webs pierced toreflect the lattices of the existing bridge.

Pre-calculated loads were jacked intothe arches at the interface between thecolumns and the truss panel points.Because the arches and trusses behavedifferently under temperature changes,these forces were calculated to relievethe bridge without lifting the truss off itsbearings on hot days, while providingadequate support on cold days. The archeswere further designed to stand alonewithout the stiffening effect of the trusses.

SSoocciiaall aanndd EEccoonnoommiicc CCoonnssiiddeerraattiioonnssDesign and construction decisions

favored traffic safety and convenience.The arches were erected with limited

lane closures. The six arch ribs wereerected in six nights, with the streetbelow the bridge closed from 9:00 p.m.to 6:00 a.m. Only one lane above thebridge was closed, so that the truss abovethe arch being erected could be used tolift the rib into its final position. Otherwork was performed with only partialclosure of the street below, minimizingthe effect of the construction on automo-bile traffic. Traffic safety and conve-nience was also enhanced by the designitself. The use of arches left the entirewidth of the street open without columnsor piers, which a traditional temporaryshoring scheme would have required.

cule span, the deck type and the drivesystem. After the final design had beenstarted, in July 1995, WisDOT decided toaccelerate the schedule. The project teamcompleted the design in April 1996, sev-eral months ahead of the original sched-ule.

The new double-leaf rolling lift spanprovides better approach alignments,incorporates a number of new technolo-gies and has been designed to preservemany of the aesthetic attributes of theoriginal bridge. Named after the leg-endary Green Bay Packer linebacker,Ray Nitschke, the new bridge was openedto traffic in October 1998.

UUnniiqquuee oorr IInnnnoovvaattiivvee AAssppeeccttssNew or innovative technologies

employed in the replacement bridgeincluded the first use of exodermic gridfor the bridge deck and the first use of aclosed loop hydraulic drive system on abascule bridge. Another unique and chal-lenging aspect of the project was the useof the metric system.

The exodermic deck, a proprietarysystem, incorporates a reinforced con-crete deck that is cast on top of and com-posite with a steel grid and the floorbeams. This deck system has excellentriding characteristics and low mainte-nance costs in comparison to open griddecks. The deck system makes maximumuse of the compressive strength of theconcrete and the tensile strength of thesteel grid. The horizontal shear is trans-ferred between the concrete and the gridthrough partial embedment into the con-crete of the steel grid tertiary bars andstuds. The concrete slab is 114 mm thickand the total deck thickness is about 246mm. The concrete is cast full depth overthe floor beams and studs are welded tothe floor beam to achieve compositeaction with the floor beams. The decksystem spans between floor beams,spaced at 4.1m, eliminating the need forlongitudinal stringers.

The hydraulic motor drive, a closedloop hydraulic system, consists of onehydraulic power unit, two hydraulicpower motors and two rack and pinionsets per bascule leaf. The motors are cou-


The Main Street Bascule Bridgecrossing the Fox River in Green Bay,Wisconsin, was experiencing ongo-ing, expensive machinery problemsand increasing misalignment due tounknown foundation problems.Originally constructed in 1929 thebridge had become an historicallandmark, however, in the summerof 1992, the City of Green Bay had

decided to replace the four-lanebridge with a new bascule span on adifferent alignment to the north. Thedesigners of the replacement bridgefaced and met numerous technicaland aesthetic challenges.

A study of options for the new cross-ing, authorized by the WisconsinDepartment of Transportation (WisDOT),included the investigation of variouschannel and approach roadway align-ments, as well as alternatives for the bas-

RRaayy NNiittsscchhkkee MMeemmoorriiaall BBrriiddggee

Green Bay, Wisconsin

Merit Award: Moveable Span

Project TeamCo-Owners

Wisconsin Department ofTransportation and the Cityof Green Bay

DesignerParsons Brinckerhoff

Steel FabricatorPDM Bridge

Steel DetailerTensor Engineering, Inc.

Steel ErectorHi-Boom Erecting, Inc.

General ContractorsLunda ConstructionCompany

Consulting FirmGraef, Anhalt, Schloemerand Associates, Inc.

pled to the pinion shaft by the use of ashrink disc, allowing the easy removal ofthe motor from the shaft for mainte-nance. The hydraulic power unit allowsdifferential load sharing between the pin-ions of the same leaf. The hydraulicmotors are capable of smooth rotation atvery slow speed, which allows very reli-able and smooth span control duringacceleration, full speed and span seating.Routine maintenance includes checkingfluid levels, filters and leaks. This systemhas the lowest maintenance requirementsof the three systems studied.

EEccoonnoommiicc BBeenneeffiitt oorr CCoosstt EEffffeeccttiivveenneessssooff DDeessiiggnn

The estimated construction cost forboth of the proposed bridge types,Scherzer bascule and Trunnion bascule,was determined to be very close. Theproject team decided to use a Scherzerbascule since most of the movablebridges in WisDOT District 3 areScherzer’s, it was believed that in keep-ing with the familiar bridge design main-tenance would be somewhat easier.

SSttrruuccttuurree CCoonnffiigguurraattiioonnEach leaf consists of two main girders,

1880 mm deep at the center break and4300 mm deep at the pinion. The girderflanges vary from 30 mm x 480 mm atthe tip to 90 mm x 600 mm at the pinion.Each leaf rolls on a 3 m radius tread cast-ing. The floor beams are spaced at 4.1 mand vary in depth from 1200 mm at thegirder to 1376 mm at the center of theroadway. The 2.4 m sidewalks on eachside are supported on brackets and can-tilevered from the girders. The counter-weight is supported by a combination ofthree vertical beams and two horizontaltrusses. Each leaf is braced by a series ofthree longitudinal cross frames and later-al bracing at the bottom of the floorbeams.

AAeesstthheettiicc CCoonnssiiddeerraattiioonnssIn deference to the original bridge

and its landmark status, the design teamincorporated a number of architecturalfeatures from the original structure in thedesign of the new bridge. The new tendertower replicates the octagonal shape ofthe original tower and includes a clay tileroof of the same type as was used on theoriginal operator’s house. A decorativeterra cotta cornice from the originalhouse was also salvaged and reused. Thedesign team designed a steel railing toclosely match the railing on the originalstructure and the tender tower wasstained red to match the color of theNeville Public Museum and the old

C&NW Railroad Depot. Accent lightinginstalled along the edge of the bridgedeck serves further to highlight thestructure at night, in particular the grace-ful arch of the main girders.

TTyyppee ooff bbaassccuulleeThe team considered two types of

conventional bascules, a Trunnion bas-cule and a Scherzer bascule—the typeeventually selected. Trunnion basculespivot about a fixed shaft or trunnion,whereas Scherzer bascules roll back-wards as they rotate open. The Scherzerbascule is supported on heavy treadplates. Gravity and pintles, otherwiseknown as gear teeth, in the tread plateprevent the bridge from moving out ofline as it rolls open. The drive machineryis mounted on the movable leaf betweenthe girders. The Scherzer basculerequires a slightly smaller opening anglethan the trunnion bascule because itmoves away from the channel as it opens.

RRooaaddwwaayy ddeecckkEngineers evaluated three roadway

deck types: conventional open steel grid,steel grid half-filled with concrete andexodermic. Each deck type was evaluatedagainst three criteria that included firstcost, maintenance cost and ride quality.The exodermic deck was chosen for thisproject based on a reasonable first cost,low maintenance cost and excellent rid-ing characteristics. The exodermic deckis heavier than an open grating deck, butit can span greater distances than eitheran open grid deck or half-filled grid,thereby simplifying the floor framing.

MMeecchhaanniiccaall ddrriivvee ssyysstteemmThe project team examined three

types of mechanical drive systems: a tra-ditional electric motor and gear drive sys-tem, a hydraulic cylinder system and alow-speed/high-torque hydraulic motordrive system. The hydraulic motor systemwas determined to have a slightly higherfirst cost than the hydraulic cylinder sys-tem, but less than the gear drive system.Maintenance and operational advantagesled to the selection of a low-speed/high-torque hydraulic motor system for thisproject.

FFoouunnddaattiioonnAs the design of the superstructure

and mechanical and electrical systemsprogressed, the team performed a alter-native foundation analysis to determinethe optimal foundation type for the bas-cule piers. The new bridge was analyzedin accordance with FHWA HEC-18 and

determined to have potential local scourto depths of nearly 14 m in the vicinity ofthe bascule piers. Soil conditions fromthe river bottom to the top of bedrockwere found to be extremely poor. Theselected foundation type was 2.4 m cais-sons, socketed into sound rock.


Situated in the Big South ForkNational River and Recreation Areathe bridge is a four-span weldedplate girder structure with spans of145’/220’/350’/280’. The superstruc-ture is composed of four girdersspaced 12’ on centers, supporting a42’wide composite concrete slab.Rising over 200’ above the river,with only limited workspace forcranes, weights needed to be held tothe minimum practical. Using HPS70W steel helped achieve this.

Because the bridge site was located ina national park and near a historic dis-trict it was necessary to develop a projectthat minimized impacts both physicallyand visually on the surrounding area.Accordingly, the approach roadway andbridge combined to limit alterations tothe landscape by virtually eliminatingexcavation. Additionally, the bridgedesign provided for erection of steelgirders from the existing road networksupplemented by incremental launchingof sections comprising the third pier’snegative moment section and span four.Further, aesthetic considerations wereaccomplished through the use ofunpainted weathering steel, to blend intothe forest setting and use of rusticationstrips at 10” intervals vertically on thepier columns to enhance the visual pro-portions of their extreme heights.

OOppttiimmiizzaattiioonn aanndd IInnnnoovvaattiioonn iinn DDeessiiggnnOptimization of design must start at

the initiation of the design process. Witha length of 995’, a totally jointless bridgewas not practical. Further, abutment one,on the low end of the 2.24% grade, wasfounded on rock. Pier one, 63’ in heightand only 145” from the first abutment,was determined to be easily deflected13/8”, the maximum possible displace-ment, without any significant momentaddition at its base. Similarly, the secondand third piers, with column heights of


SSttaattee RRoouuttee 5522 oovveerr

CClleeaarr FFoorrkk RRiivveerrMorgan County, Tennessee

Merit Award: Medium Span

to erect. Stockpiled prices for HPS 70Wsteel for both bridges were $0.30 perpound. The completed cost for the com-plete structure was $95.34 psf.

In conclusion, State Route 52 over theClear Fork River project was a textbookexample of how sensitivity, careful plan-ning, astute design and innovation cancome together to create a virtually main-tenance free, economical, environmental-ly sensitive and monumental bridgecrossing.

183’ and 124’ respectively, could alsodeflect the maximum amount based onthermal movement accumulations pre-suming that the first abutment was fixed.Calculations also indicated that the forcedeveloped by gravity loads acting on thefrictional resistance of sliding bearingsurfaces would exceed the force requiredto deflect the piers. Accordingly, it wasdecided to design the bearings at the firstabutment and all piers as fixed.Expansion bearings and a roadwayexpansion device were placed only at thesecond abutment.

The next consideration for optimiza-tion was selection of a web depth andthickness. Generally speaking, in spansup to 350’ transversely stiffened girdersare more economical than transverselyand longitudinally stiffened girders.Further, optimization is achieved whenthe depth to thickness ratio is at the max-imum allowable limit. In this case a 96”deep, 3/4” web was chosen for the non-hybrid HPS 70W section over the secondand third piers. In the positive momentsection, analysis was required to deter-mine the minimum allowable thicknessof the web. The 96” grade 50W web wasonly 1/2” thick.

CCoonnssttrruuccttaabbiilliittyyIn order to utilize the smaller reason-

able section in the positive momentregions it was necessary to break the pos-itive moment pours into segmentsremembering that, as a slab section ispoured and cured, subsequent stressesare accumulated on the resulting com-posite section.

Span one and span two, up to thedead load inflection point near the sec-ond pier, were designed as non-hybridusing grade 50W steel. The negativemoment sections at the second and thirdpiers were designed solely of HPS 70W,while the positive moment sections ofspans 3 and 4 were designed as hybridgirders, utilizing grade 50W webs andcompression flanges while using HPS70W in the tension flanges. All stiffenersand cross frame material are grade 50W.

Utilizing HPS 70W for the pier sec-tions at the second and third piersreduced their lifting weights 30% over agrade 50W design.

EEccoonnoommiiccssThe overall cost of the girders for the

Clear Fork River bridge, in place, was$1.03 per pound, vs $1.18 per pound fora similarly designed all HPS 70 bridgeconstructed previously even though thegirders were fabricated at the same plant,shipped further and were more difficult


Project TeamOwner

Tennessee DOTDesigner

Tennessee DOT Division ofStructures

Steel FabricatorTrinity Industries

Steel DetailerAlabama Structural Detailers

Steel ErectorJ. S. Rollins, Inc.

General ContractorJ & M, Inc.

C ommunity involvement wascritical in selecting the replacementfor an existing landmark bridge inIndex, Washington. The new WesSmith Bridge, named after a localresident that has lived and worked inthe town of Index for 80 years, is asteel tied arch bridge with bolted boxtie girder, welded box arch,Vierendeel struts, cable hangars anddrilled shaft foundations. The steelcoating consists of thermal metalizedspray galvanizing.

While a concrete arch alternative wascompetitively bid against the steel alter-native, the concrete arch was not costcompetitive due to the remote site andrequirement for significant shoring to beplaced in the river.

CCoommmmuunniittyyIndex is a small community located

on the bank of the north fork of theSkykomish River. The bridge serving thistown is vital to its existence and is recog-nized as a signature of the town. Theonly other access to the town is a 25 milelong primitive gravel road not suitable foremergency services or school bus travel.The existing bridge was a 220’ long, sin-gle lane, steel truss with a timber deck.Even though this 1917 bridge had beenrehabilitated in 1980 it was classified asstructurally deficient and functionallyobsolete.

After numerous meetings of theCitizen’s Advisory Committee it wasdecided that the new bridge would betwo lanes wide with sidewalks on eachside and would be built on the samealignment as the existing bridge. Thepreferred structure type was an 80 m tiedarch, allowing for a long span with mini-mal structure depth and no supports inthe river. The visual impacts of the arch-es above the roadway complimented thesteep canyon walls.

AAeesstthheettiiccssThe aesthetics of the arch were con-

sidered when developing the structuralsystems for the arch. Vierendeel strutswere used to provide maximum views of


WWeess SSmmiitthh BBrriiddggeeIndex, Washington


tally sensitive north fork of theSkykomish River. A full member laydown was completed at the fabricatorbefore holes were drilled in the coverplates to assure members would fit in thefield.

The tie girder was erected first usingtemporary supports at the edge of theriver. Tie-downs at the abutments wereused to eliminate supports in the river.Arch sections were erected using false-work supported on the tie girder. Ahydraulic jacking system at the top of thefalsework towers was used to jack thearch up into final position to install thelast arch section. Cable hangers wereinstalled and the arch falseworkremoved. The hangers were adjusted forfinal geometry and load by adjusting thebolts at deck level. The construction was

completed without requiring falsework inthe river, which is habitat for the endan-gered Chinook salmon and Bull trout.

PPeeddeessttrriiaann EElleemmeennttssThe Wes Smith Bridge is located at

the edge of the town of Index. It receivesfrequent use by pedestrians and sight-seers. The river is a popular white waterrafting destination so river views are impor-tant. A combination pedestrian/traffic barrierwas placed at the edge of the structure toprovide a pedestrian friendly facility withgood views both up and down the river.The sidewalk opens between the hangersystem and roadway to provide additionalwidth of sidewalk and allow pedestrian tocross from one side of the bridge to theother as river rafters float by.

the surrounding mountains. The barrierat the edge of the roadway was eliminat-ed and combined with the pedestrianrailing to better provide views up anddown the river. Sidewalks were providedon both sides of the bridge for easyaccess for local town residents.

TTeemmppoorraarryy DDeettoouurrThe existing truss was used as a tem-

porary detour during construction so thatthe new bridge could be built on thesame alignment as the existing bridge. Acrane located on each bank of the riverrelocated the existing truss. There wereno supports required in the river toaccomplish truss relocation. Total road-way closure was six hours, with traffictemporarily diverted onto a gravel countyroad.

SSttrruuccttuurraall DDeettaaiillssFour 1.8 m diameter drilled shafts

were used to support the arch with one ateach corner of the bridge. The steel boxarch section was sized to accommodateerection and inspection. Splice locationswere selected based on the maximumsize member that could be delivered tothe site. The tie girder is a bolted steelbox so there is redundancy in the tensionmember. Steel transverse floor beamswere used to support the cast in placeconcrete deck. The continuous concretedeck acts as a horizontal diaphragm,eliminating the need for cross-bracingthe floor system. Vierendeel struts wereselected to laterally brace the arch whilemaintaining open views of the surround-ing mountains.

The end floor beams were designedwith a full moment connection to thearch and tie intersection. This connectionreduced the effective length factor toallow a reduction in the number ofvierendeel struts required. The interiorfloor beams had flange connections tostabilize the tie girder and prevent longi-tudinal movement between the tie girderand floor beam at the top flange.

The bearings were designed to allowfor movement during construction so thatthe tie girder would support the load.After the deck was placed, the bearingswere fixed so they would provide lateralsupport to the drilled shafts. The fixedbearings provided for the longitudinalseismic force to resist the soil at eachabutment.

CCoonnssttrruuccttiioonn SSeeqquueenncceeThe construction sequence identified

in the plans allowed erection to takeplace without impacting the environmen-


CCooaattiinngg SSyysstteemmThe county had a strong desire to

achieve a durable and low maintenancestructure. The coating system used on thenew bridge is a shop applied thermalspray coating of aluminum and zinc. Thesplice plates and reinforcing steel werehot-dip galvanized. These coating sys-tems provide both barrier protection andgalvanic protection minimizing futuremaintenance costs and ensuring a longstructure life.

SStteeeell AAlltteerrnnaattiivvee CCoosstt CCoommppaarriissoonnA concrete tied arch alternative was

designed and competitively bid againstthe steel tied arch alternative. Six bidswere received, with five of the six biddersbidding the steel alternative. The low bidon the steel alternative was $2,562,597,9% lower than the concrete alternativebid of $2,808,605. All of the five steelbids were at or below the concrete alter-native bid. The concrete arch was notcost competitive due to the remote siteand requirement for significant shoringto be placed in the river during tie andarch erection.


Project TeamOwner

Snohomish CountyDesigner

HNTB CorporationSteel Fabricator

Oregon Iron WorksSteel Detailer

John Newell & AssociatesSteel Erector

J & S ConstructionGeneral Contractor

Mowat Construction Co.

Trunk Highway 61 (TH 61) runsalong the scenic north shore of LakeSuperior in Minnesota. The highwaycrosses the Gooseberry River withinGooseberry Falls State Park, whichattracts 580,000 visitors annually. Builtin 1922, the old bridge over the riverconsisted of a 150’ arch shaped decktruss with 60’ beam spans at both ends.A third arch was added, in 1937, toaccommodate a 30’ roadway with 5’ side-walks on both sides, which act as viewingplatforms for waterfalls located west andeast of the bridge. A visitor center islocated near the north end of the bridgeand there is also an additional roadsideparking at the south end, both of whichmake the area around the bridge heavilycongested with pedestrian traffic andcause safety concerns.

By 1990, the bridge was badly deteri-orating. An arch type bridge was chosenfor replacement in order to maintain thelook of the old bridge from both theupper and lower falls, where it frames theriver gorge scenery. The new bridgewould be built in conjunction with a newvisitor center located away from the road.

The new bridge consists of a 154’main steel arch span supporting a 14”deck slab with three concrete slab spanson both ends varying in length from 16to 24’. The cross-section for the mainspan consists of 2 box shaped fixed arch-es 42.5” deep by 29.5” wide. In order tomaintain bridge access for pedestrianviewing of the waterfalls, and at the sametime reduce pedestrian traffic on thehighway, an 8’ walkway was provided atdeck level on one side of the bridge withanother 8’ walkway suspended below thebridge on the other side. These walkwaysconnect with trails that run throughoutthe park. Tubular steel sections wereused for the pier columns, spandrelcolumns, the struts that brace the archesand the tension members which suspendthe walkway underneath. A slab span sys-tem which runs between the pier andspandrel cap beams was chosen to reducesuperstructure depth and to be more aes-


TTrruunnkk HHiigghhwwaayy 6611 oovveerr

GGoooosseebbeerrrryy RRiivveerrLake County, Minnesota


thetically pleasing. The new pedestrianrailing was designed to look similar to theold rail for historic reasons. During theGreat Depression, rock walls located atthe south abutment of the old bridge hadbeen built by the Civilian ConservationCorps. These walls were saved and thenew abutment, directly adjacent to theold, was constructed with a rock facing tomatch the old wall.

TH 61 is the only road along thenorth shore to Canada and no practicaldetours are available. This coupled witha tightly confined area made stage con-struction a requirement. Due to the steepslopes and an environmentally sensitivearea the contractor was constantly chal-lenged during construction.


Project TeamOwner


DesignerMinnesota Department ofTransportation

Steel FabricatorThe D.S. Brown Company-Lewis Engineering Division

Steel DetailersThe D.S. Brown Company-Lewis Engineering Divisionand Tensor Engineering Co.

Steel ErectorM.A. Mortenson Company

General ContractorsM.A. Mortenson Company

This $21.8 million project con-nects US 35 to WV62 over theKanawha River near Buffalo, WestVirginia. The bridge site is in theKanawha Valley of Putnam County,West Virginia, halfway betweenCharleston, the state’s capital andlargest city, and Huntington, the sec-ond largest city in the state. Thebroad Kanawha Valley is surroundedby rolling hills and dotted with farm-ing communities and newer subur-ban areas.

Although Putnam County is one ofthe fastest growing counties in the stateof West Virginia, there was no bridgecrossing the Kanawha River within milesof Buffalo. The new Lower BuffaloBridge opens up some of the best land inthe state to economic development andprovides a direct connection to a new US35 upgrade under construction and I- 64.

The bridge had to be completed andopen to traffic by mid-1998 to allow forthe new Toyota manufacturing facility inBuffalo to ship state-of-the-art engines.The bridge also had to span the naviga-ble Kanawha River with minimal false-work and span over areas on both bankswith known archeological deposits.

EEnnvviirroonnmmeennttaall CCoonncceerrnnss The flood plain area at the Lower

Buffalo Bridge site is an establishedarcheological dig site with numerousNative American campsites and artifacts.An environmental consultant for theWest Virginia Department ofTransportation (WVDOT) performedboth phase one and phase two archeo-logical surveys at the proposed bridge siteand identified archeologically sensitiveareas on both riverbanks. Constructionactivity for a new bridge over these sensi-tive areas was limited to the depth of cul-tivation (about 30”). Excavation andfoundation work could not begin untilafter an extensive phase three survey wascompleted.

Rather than perform the lengthyphase three survey work, the WVDOTdecided to design and build a five spanstructure with the piers and abutments


LLoowweerr BBuuffffaalloo BBrriiddggeeBuffalo, West Virginia

Merit Award: Long Span

Project TeamOwner

West Virginia Department ofTransportation

DesignerBRW/Hazelet & Erdal

Steel FabricatorStupp Bridge Company

Steel DetailerStupp Bridge Company

Steel ErectorTri-State Steel Construction

General ContractorNational Engineering

bridge was fracture critical. To provideredundancy, permanent cross-framesthroughout the length of the bridge weredesigned to transfer the weight and liveloading from one box to the other in theevent that a girder section was crackedand became unserviceable.

Another example of the structure’stechnical originality was the use of large,torsionally rigid box girder field sectionsto reduce the number of individual fieldpieces and field bolted connections. Thedesigners located field sections to limitshipping pieces to 100 tons or less. Actualshipped pieces ranged in size from up to92 tons and 113’ long. By choosing atwin box girder superstructure thedesigners were able to minimize thenumber of field bolted cross-frames con-nections between girder lines. A shopinstalled top lateral bracing system,which was designed to support the boxgirder sections on their side, providedexcellent torsional rigidity during ship-ping and erection.

The use of unpainted weathering steelfor the bridge provided corrosion resis-tance, reduced shop fabrication time,eliminated the need for future mainte-nance painting and enhanced the overallappearance of the structure. The burntsienna color of the unpainted weatheringsteel complements the rural landscape.The color of the steel girders contrastswith and delineates the lighter gray anddark shadows of the piers and deck fas-cia. The overall appearance is that of astructure that truly belongs in a valleylandscape.

The bridge design provides an attrac-tive, proportional and balanced structure.Although the box girder sections are 10to 13’ deep at midspan and haunch to 18’over the piers, the long spans give theimpression of a slender ribbon stretchedfrom bank to bank.

CCoonncclluussiioonnSteel fabrication began in March 1997

and proceeded concurrently with thebridge substructure construction. Thesteel erection was complete in August1998, and the concrete deck, parapets,and overlay were cast in the fall in timefor traffic to cross the bridge in October1998.

located outside of the archeologicallysensitive areas. The Lower BuffaloBridge, with and overall length of 1,850’and spans of 269’, 394’, 525’, 394’, and269’, easily clears the sensitive areas. Theuse of a steel girder superstructureallowed great flexibility in locating piersand abutments.

FFeeaattuurreess ooff tthhee SSttrruuccttuurree The Lower Buffalo Bridge is on a tan-

gent alignment. The approach roadwayon the west bank of the Kanawha Riverhas a 330’ radius curve with a spiral. Theroadway grade is 3% on the west side and5% on the east side on a 790’ verticalcurve. The profile grade provides a 68’vertical clearance from normal river poolelevation to the bottom of the steel gird-ers, and the two river piers provide a500’ wide navigation channel.

The bridge section has two 12’ trafficlanes, two 6’ shoulders and concreteparapets. Right-of-way was purchasedadjacent to the bridge for a future dualstructure. A constant deck cross slope of.02%, and the use of a box girder super-structure, allows for a future structure tobe easily built with a widened four laneroadway.

The bridge superstructure consists oftwin haunched composite steel box gird-ers on 20’ centers supporting a reinforcedconcrete deck with parapets. The boxgirder webs are plumb and on 10’ centerswith 4’-4” deck overhangs. The steel boxgirder profile haunches over the piersand smoothes out into parallel flangeboxes at midspan. The two steel box gird-ers are supported on curved columns.

Details of the structure include aclean and uncluttered box girder under-side, interior box lighting, completeinspection access and the use of Grade50W steel throughout. Additionally, iden-tical box girders with a symmetric spanarrangement permit significant duplica-tion in fabrication. Constant 36” wide top flanges simplified the instal-lation of stay-in-place forms.

The structure is fully continuous fromabutment to abutment. Expansion andcontraction is accommodated by the useof steel finger joints with neoprenetroughs at the abutments and guidedsteel pot bearings at the two approachpiers and abutments. The two river piershave pot bearings fixed against tempera-ture movement. Full depth box girderinterior stiffeners permit the verticalreaction over the piers to remain alignedwith the supporting column throughoutthe range of temperature movement.

None of the 3,200 tons of Grade 50Wstructural steel used to fabricate the

The 48th Street entrance rampto the northbound Franklin D.Roosevelt (FDR) Drive in New YorkCity had been closed to traffic since1987. In 1996, after nine years ofextensive traffic congestion onManhattan’s east side, elected offi-cials and the New York StateDepartment of Transportation (NYS-DOT) made a commitment to thecommunity to reopen the 48th Streetentrance ramp as quickly as possible.

OOwwnneerr’’ss CCrriitteerriiaaAs part of the State’s commitment to

the community and to the traveling pub-lic, the following critical issues wereaddressed:

• Fast-track schedule that would per-mit the ramp to open quickly. NYSDOTestimated 15 months for final design and18 months for construction;

• Technological improvements to theramp design to improve safety, reducemaintenancence and be aestheticallycompatible with the United Nations/EastSide Manhattan neighborhood;

• Community participation program toensure that neighborhood concerns wereaddressed. These provisions includedfunctional aspects of the design, as wellas noise concerns for residential areasand security concerns at the UnitedNations garage during construction.

• Construction staging to maintainthree lanes of traffic on northbound andsouthbound FDR Drive during peakhours, and minimal closures of lanes atnight.

EEssttaabblliisshhiinngg aa FFaasstt-TTrraacckk SScchheedduulleeNYSDOT’s original schedule for

reopening the ramp on a fast-trackschedule called for a time frame of 15months for final design and 18 monthsfor construction, for a total of 33 months.

/ Modern Steel Construction / July 2000

4488tthh SSttrreeeett EEnnttrraannccee RRaammpp

ttoo FFDDRR DDrriivveeNew York, New York

Merit Award: Grade Separation

AAccccoommmmooddaattiinngg CCoommmmuunniittyy CCoonncceerrnnssA priority for NYSDOT in the design

and construction of the ramp was toaddress the various concerns ofManhattan’s east side community.

First, the community requested thatthe new ramp not preclude the potentialfor future pedestrian and bicyclist accessto a future East River esplanade. As aresult, the new ramp is located north ofthe previous ramp location to allow spacefor a future pedestrian and bicyclist rampfrom First Avenue to a future esplanade.

Secondly, the project team met withthe United Nations regularly during thedesign stage to discuss potential securityissues. As a result, the contract docu-ments include special notes and details toaddress these security concerns.

Thirdly, to alleviate concerns aboutconstruction noise during nighttimehours, noise-intensive operations wererestricted at night. In addition, the con-tract documents included a contractorincentive for early completion of the pile-driving operations for the foundations.

Finally, to inform the community ofthe project’s progress throughout thedesign stage and also to give the commu-nity the opportunity to voice their con-cerns, NYSDOT and our firm met withthe community regularly during thetwelve months of design to discuss theproject progress. Task force meetingswere held during construction to keepthe interested parties informed about theproject’s progress and to discuss any con-cerns. A web page for the project keptthe public informed during construction.

CCoossttDesign was completed under budget.

The construction contract, bid at verycompetitive prices, was also completedwithin the budget and the contractorreceived the full incentive bonus.

CCoonncclluussiioonnThe design of the 48th Street

entrance ramp required a coordinatedapproach to integrate NYSDOT’s criteria,the concerns of the community and alevel of technological sophistication thatimproves vehicular safety and futuremaintenance.

Cooperation between designers andNYSDOT accelerated the actual designwork and produced final contract docu-ments in twelve months, shaving threemonths off NYSDOT’s design schedule.

In addition, the contract was bid in acost-plus format that requires contractorsto bid a contract amount for work itemsand to commit to a maximum construc-tion duration. Detailed constructabilityanalyses were performed during design,reducing NYSDOT’s construction sched-ule by six months.

The contractor who was awarded theproject was able to reconstruct the rampand open it to traffic in seven months,which was five months ahead of our fir-m’s schedule. A project that began with a33 month schedule had been completedin 19 months.

TTeecchhnnoollooggiiccaall IImmpprroovveemmeennttssThe new ramp, one of the first com-

posite box girders to be used in the NewYork metropolitan area, is a continuousfour-span bridge, approximately 133 min length, comprised of twin steel boxgirders. The ramp has a horizontal curva-ture of 90 degrees with a 50 m radius.The box girder design was selectedbecause its configuration is particularlycompatible with the client’s criteria:

• The box girder design offers clearaesthetic advantages over I-beam con-struction. In response to its highly visiblelocation, the new ramp design is a sleekfour-span bridge with trapezoidal boxgirders. The new ramp’s longer spansreduce the number of columns and pro-mote a a clean appearance;

• Box girders are an efficient structur-al cross-section which resists the hightorsional stresses caused by tight curva-ture; and

• Box girders reduce maintenancerequirements as compared to I-beamconstruction. Because box girders do nothave exposed lower flanges to collectdebris, maintenance requirements arereduced.

NYSDOT’s goal was to comprehen-sively address all technical issues relatedto the ramp design. The new entranceramp at 48th Street had to alleviate thecongestion along First Avenue while pro-viding a safe access for the vehicular traf-fic. Our firm’s design of the reconstructedramp included geometric improvementsthat doubled the acceleration distance ofthe previous ramp, therefore allowing fora longer acceleration lane for enteringvehicles to merge with the northboundmainline traffic. Major restriping and sig-nage was also included to facilitate themerge between the ramp vehicles andthe vehicles traveling on the northboundmainline FDR Drive.

Project TeamOwner

New York State DOTDesigner

TAMS Consultants, Inc.Steel Fabricator

Tampa Steel Erecting Co.Steel Detailer

Tensor Engineering Co.Steel Erector

Rice-Mohawk ConstructionCompany

General ContractorDeFoe Corp.

T he Universal Boulevard(Republic Drive) /I-4 Interchange,provides direct access to a majortheme park, Universal Studios, andeases traffic congestion on one of thebusiest stretches of I-4 in Orlando,Florida. The new Ramp H over thewestbound C/D Bridge is part of theRepublic Drive / I-4 Interchangewhich carries one lane of traffic fromwestbound I-4 to Universal Studiosand the surrounding community.The Ramp H bridge represents aunique, economical and yet aestheti-cally appealing solution to the com-plications imposed by crossing abraided ramp with severe skew. URSGreiner Woodward Clyde served as asubconsultant to Ivey Harris & Wallsand was responsible for the design ofall three grade separation structuresplanned for this interchange.

BBrriiddggee DDeessccrriippttiioonn The new bridge consists of seven

equal spans, simply-supported, with 88’per span, making a total bridge length of616’. The bridge alignment follows amild 2.25 degree curve. The deck widthis 30’ and consists of an 8-inch-thickconcrete deck slab supported by andcomposite with three lines of W36 × 245rolled steel beams (Grade 50). The sub-structure piers are aligned radial to thebaseline and consist of four hammerheadpiers and three straddlebent piers locatedat the central portion of the bridgelength. The piers are conventionally rein-forced concrete supported on pile foun-dations.

DDeessiiggnn CChhaalllleennggeess Although the bridge crosses over a

two lane roadway only 46’-6” wide itincludes travel lanes, shoulders and traf-fic barriers, the required minimumbridge length is in excess of 600”. This isa result of severe 82.5 degree skew


RRaammpp HH oovveerr WWeessttbboouunndd CC//DD

RReeppuubblliicc DDrriivvee//II-44 IInntteerrcchhaannggeeOrange County, Florida

Merit Award: Grade Separation

capacity of the beams and the 8” thickdeck slab. The beams are simply-sup-ported by piers with inverted “T” capcross-sections. The use of shorter, simplespans benefited the overall bridge econo-my in several ways:

• Standard rolled beam shapes couldbe used that are easily shipped with nofield splicing;

• The discontinuity at the beam endsallowed the structural section of the piercap to extend into the superstructure andreduce the overall structural depth. Thisis achieved without the complications ofan integral pier cap;

• The superstructure dead load reac-tions were minimized allowing for strad-dle piers designed using reasonable pro-portions.

Based on project bid tabulations andfinal quantities, the total constructioncost for the bridge (excluding retainingwalls) was $1,172,000, which equates toa unit cost of $63.43 psf of bridge.

AAeesstthheettiiccss Although the substructure may be the

predominant aesthetic feature of thebridge’s overall appearance the relativeproportions of the substructure andsuperstructure, and the variations inwhich they intersect, allow for the two toblend together as one form adapting tothe site. The pier columns, which are in asustained and direct view from the lowerroadway traffic, utilize rusticated surfacesto soften the appearance of the large col-umn faces. The bridge also has the

unique feature of displaying its uniqueaesthetic appeal to those traveling underthe bridge.

between the two roadway alignments.Additionally, to provide the requiredminimum vertical clearance of 16.5’ forthe lower roadway the structure depthwas limited to a total of 7’. This is a resultof two roadway geometric constraints onthe vertical profiles: the lower roadwayprofile could not be dropped due to thehigh water table and its affect on theroadway subgrade and the bridge profilecould not be raised due to the close prox-imity of an at grade intersection to thewest and the I-4 exit ramp tie-in to theeast.

DDeessiiggnn SSoolluuttiioonnss A common solution for relatively nar-

row structures with severe skews, such asthe one found here, is a bridge structurewith a continuous superstructure and sin-gle column piers along the bridge center-line. However, although this would min-imize the main span length the resultingspan length required would be in excessof 300’, which was unacceptable giventhe structural depth constraints. Duringthe bridge development phase of the pro-ject, two general bridge types utilizingshort span lengths were evaluated: a sin-gle span structure with AASHTO beamsframed transverse to the direction of traf-fic and supported with two long substruc-tures running the length of the bridge oneach side and a multi-span structure withbeams framed parallel to traffic and sup-ported with hammerhead piers wherespace permits, and straddle piers other-wise. Based on preliminary constructioncost estimates, the transversely framedoption was significantly more expensive(approximately 50%) and aestheticallyundesirable. The longitudinally framedoption was developed further to compareAASHTO type beams and rolled steelbeams. For identical span arrangements,a direct cost comparison between thebeam types showed them as being essen-tially equal in cost (within 6%). Rolledsteel beams were selected based on aes-thetic and lightweight considerations, andto provide consistency with the two othersteel plate girder bridges within the inter-change.

DDeessiiggnn EEccoonnoommyy With a total structural depth limita-

tion of 7’ (including pier cap depth), amaximum rolled beam depth of 36” wasavailable for structural optimization. Aseven span arrangement with three girderlines using W36 × 245 rolled steel beamswas found to be the most economical,resulting in approximately 25 lb. persquare foot of structural steel deck area.A generous beam spacing of 10’ withoverhangs averaging 5’ optimized the


Project TeamOwner

Universal City DevelopmentPlanners

DesignerURS Greiner WoodwardClyde

Steel FabricatorCarolina Steel Corporation

Steel DetailerABS Structural Corporation

Steel ErectorV & M Erectors

General ContractorHubbard ConstructionCompany

The Kuparuk River on the NorthSlope of Alaska is a typical northernstream with water flows of less than5,000 cubic feet per second (cfs) formost of the year, but large springbreak up floods that can exceed140,000 cfs extending over a 2 milewide flood plain. In addition to thistremendous amount of water, large 5’thick, fresh water ice floes also occurduring spring floods. To supportdevelopment of the new Kuparuk oilfield, an access road was built acrossthe Kuparuk River in the late 1970sat a location where the flood plain isapproximately 10,000’ wide.Economically bridging this floodplain for the spring break up flood


KKuuppaarruukk RRiivveerr

SSuubbmmeerrssiibbllee BBrriiddggeeNorth Slope of Alaska

Special Award: Special Purpose

Jurors Comments

Bold application of steel...a structure that must

endure extremely heavy vehicle loads and face

one of nature’s most hostile environments:

arctic cold, large-scale ice flows and

overtopping spring floods.

has presented a design challengesince the original construction of thisaccess road.

For nineteen years, the gravel road atthe east and west channels of theKuparuk River was breached annuallyand allowed to wash out during springbreakup, resulting in a six to eight weekroad closure interrupting access to theKuparuk oil field. Historically, the cost ofpermanent bridges to provide access tothe field were found to be cost prohibi-tive due to extreme environmental condi-tions, gross vehicle loads of up to4,000,000 pounds and the riverhydraulics in which large water flowsmust be passed during the spring floods.The innovative solution consists of sub-mersible bridges in combination withpaved roadway sections that are allowedto overtop during peak spring break-upfloods.

The new Kuparuk River east (210’long) and west (150’ feet long) channelsubmersible bridges, completed in 1999,reduce the closure period of this criticalroad link to a maximum of one week peryear and eliminate the need to annuallyreconstruct the road. The cost savings ofmore than three million dollars per yearin oil field operational and advancedmaterial purchase costs will pay for theproject cost in four years.

The crossings pass the peak springbreakup flows (typically more than seventimes greater than summer flows)through and across the existing SpineRoad by using a combination of weldedsteel submersible bridges and paved lowwater roadways. The short-span, stout,welded steel structures are elegant intheir simplicity and are a practical, cost-effective answer to permanently crossinglarge, dynamic arctic coastal plain rivers.

DDeessiiggnn aanndd CCoonnssttrruuccttiioonnThe bridges are designed to support

any oil field vehicle currently in opera-tion on Alaska’s north slope. The largestof these vehicles weighs approximately3.8 million pounds while others havemaximum wheel loads that exceed 370kips (185 tons). The entire load carryingcapacity of the bridge is provided by thewelded steel structure. The concrete deckwas provided as a driving surface, for lat-eral buckling support of girders, and toensure composite action for horizontalloads and lateral ice loads.

Environmental loads for the bridgeconsist of wind, seismic, river current,buoyant and river ice loading. For thisdesign, wind, seismic, current and buoy-ant forces were insignificant when com-pared to the ice loading. Design ice


thickness was 52” of hard structural ice(5’ total nominal ice thickness) that iscapable of imposing tremendous loads onthe bridge deck and ice breakers.

The bridge substructure consists oflarge diameter, heavy wall and weldedsteel pipe piles—the only practicalmethod to support the massive vehicleloads. Each pile bent, spaced at 30’ con-sists of four vertical 36” diameter, 1” wallAPI 5LX-52 pipe piles driven to 80’ pen-etration to support the heavy vehicleloads and provide lateral support for iceloads. Required vertical capacity (designload) of each pile was 750 kips (375 tons)which was easily achieved using aDelmag D-62 diesel impact hammer,rated at 165,000 foot-pounds of energy.Each in stream pile bent has a steel icebreaking pipe installed at 45 degrees onthe upstream side. When impacted by anice floe, this design will fail the ice sheetin bending, rather than crushing, sub-stantially reducing the lateral force on asingle ice breaker from approximately750 kips to 320 kips. This unique designsaved time and cost by reducing the iceloads to the structure, providing reason-able tolerances for field fit-up and utiliz-ing a vertical pile in lieu of more expen-sive and impractical (for installation inhard permafrost) batter piles.

The pipe piles were slotted at cut offto receive the steel box pile cap. The slot-ted pile to pile cap connection providedboth a full moment connection for lateralload resistance and the load transfer forvertical loads, eliminating the need forbearing stiffeners. Cost saving 1½” interi-or bearing stiffeners attached to the topflange of the pile cap also eliminated theneed for bearing stiffeners in the girders.

The bridge abutment design utilizesopen sheet pile cellular structures, a

rugged and proven innovation utilizedthroughout the Pacific Northwest. Theseabutments are constructed in a circulararc in which the sheet pile cell remainsunclosed beneath the roadway. As isfound in closed cellular structures, hoopstresses are generated between the sheetpiles, but with the open cell abutmentsthe hoop stress is resisted solely by soilfriction along at the tail ends of the struc-ture. For these submerged structures, thetail ends of the central cell (tailwalls)were protected from scour by inclusion ofshort wingwalls on the upstream anddownstream sides. Wingwalls were con-structed in a circular pattern and behavein the same manner as the central sheetpile cell. This abutment type is not scoursensitive since sheet pile embedment atthe streamside face is not required forthe abutment stability.

The submersible bridge design utilizes30’ spans that allow an extremely shal-low, high-capacity deck and girder sys-tem. The superstructure consists ofeleven 22½” deep steel plate girders at 3’spacing encased in cast-in-place structur-al concrete. The girders were constructedusing ASTM A572, Grade 50 materialmeeting Charpy V-notch impact criteriaof 15/12 (avg./min.) foot-pounds at -50°F for cold weather performance.

The steel structure also served asformwork for the superstructure concreteby eliminating the need for falsework andminimizing on-site construction time andcosts. A 26” diameter fabricated steelhalf-pipe deck nose is welded to the edgeof the upstream girder to provide a roundsurface that further limits ice crushingloads on the deck. The deck nose is fittedwith guardrail support pipes that arewelded to the outside girders. A rolledplate welded to the downstream girder

Project TeamOwner

Phillips Alaska, Inc.Designer

Peratrovich, Nottingham, &Drage

Steel FabricatorsJesse Engineering Company

General ContractorAlaska InterstateConstruction

provided the concrete formwork on theother side of the bridge. Steel plateplaced on the bottom flange of the plategirders and attached with intermittent fil-let welds served as the underside con-crete form for the bridge.

The bridge design required an easilyremovable guardrail for the crossing ofoilfield vehicles up to 60’ wide. Weldedsteel pipe sleeves at the edges of the deckprovide support for the removableguardrails. The identical sections ofguardrail, each fourteen feet long, areeasily removed and replaced as the pipelegs slide into the pipe supports in thebridge deck. This system has receivedmuch praise for its ease of use, especiallyin extremely cold weather.

FFaabbrriiccaattiioonnFabrication of welded steel bridge

components was a critical element to thesuccess of this project. All of the compo-nents of the bridge were shop fabricatedinto sections that were easily transportedto the site to minimize costs. Both thedesign engineer and general contractorworked carefully with the fabricator toassure that all fabricated pieces would beeasily erected in the field. Careful matchmarking of each fabricated member andthe fabricator’s careful attention to detailallowed the structure to be erected intemperatures averaging -30° F and windspeeds of up to 20 mph without requiringfield modifications.

CCoonncclluussiioonnBy utilizing a combination of durable,

submersible bridges and paved low waterroadways an innovative solution wasdeveloped to provide reliable access tothe Kuparuk oil field for 51 weeks out ofthe year. The unique design kept the costof the project within reasonable limits forcrossing two river channels in a floodplain over two miles wide. The projectwas designed and constructed on timewith a tremendous cost savings over tra-ditional, elevated bridge designs. Thissuccessful design promises to serve as amodel for future expansion of the infra-structure on the North Slope of Alaskaand in other climates around the world.

The bridge is a three span con-tinuous welded plate girder with a124’ main span and 52’ end spans. Ithas six girders with a 53” webs in theend spans, parabolic haunches at thepiers and 32” webs in the main span.The bridge replaces a bridge with ahaunched concrete slab main spanflanked by deck girder end spanshidden by walled enclosures.

The aesthetics of the new bridgeremind motorists that this is the northerngateway to Minneapolis. The girders werehaunched to give a slender appearance tothe main span. Enclosed end spans givethe appearance of a walled abutment,retaining the style of the original bridge.The end span enclosures have a randomstone surface finish, giving texture to thevertical faces. Aesthetic requirementscalled for an unobstructed view without apier in the median of the highway below,and a shallow structure depth. This was


TTrruunnkk HHiigghhwwaayy 4477

uunnddeerr SSaaiinntt AAnntthhoonnyy BBoouulleevvaarrddMinneapolis, Minnesota

Prize Bridge Award: Short Span

Jurors Comments

A beautiful bridge...elegant and shallow main

span...interesting concept to counterweight

the short back spans and hide them

behind the abutments.

accomplished by using three span contin-uous girders. A pier wall and side wallscreate a hollow enclosure for the endspans. Counterweights were used toshorten the end spans in order to main-tain similar proportions to the originalbridge while controlling uplift at theabutments. The end spans were nothaunched at the pier for ease of fabrica-tion and to allow more depth for the con-crete counterweights at the abutments.


Project TeamOwner


DesignerMinnesota Department ofTransportation

Steel FabricatorEgger Steel Company

Steel DetailerEgger Steel Company

Steel ErectorHigh Five Erectors, Inc.

General ContractorLunda Construction Co.

T he Old Plank Road Trail(OPRT) Bridge in Frankfort, Illinoiscarries a bicycle path and pedestrianwalkway along an old railway align-ment across U.S. Route 45 at a skewof 43 degrees. A new bridge wasrequired because of a major upgradeof U.S. 45 at this location, includinga profile raise and widening to fourlanes. The bridge was designedunder the direction of the IllinoisDepartment of Transportation(IDOT), and completed in 1999.

The defining structural feature of thebridge is an A-frame pylon with its legsstraddling the highway at right angles(actually 2 degrees off a perfect rightangle, to avoid an existing drainage struc-ture). Thus, the main load carrying com-ponent, the pylon, spans the shortest dis-tance across the highway. The skeweddeck structure is suspended from thepylon by cables. There are no piers; fromabutment to abutment the deck super-structure is supported only by the cablesextending from the top of the pylon.

The abutments are set well back fromthe edges of the highway, yielding a totalbridge length of 180’ measured along theskewed deck. Four hanger cables fromthe top of the pylon, two on each side ofthe deck, divide the 180’ length of theskewed superstructure into three 60’ seg-ments.

The basic dimensions of the bridgeare indicated in its simplified plan andelevation. The pylon is 82’ high and itslegs are 114’ apart at the base. The high-way below is 73’ wide overall (includingfour traffic lanes, shoulders and a medi-an). The suspended structure is 180’long, at a skew of 43 degrees.

DDeettaaiillss ooff SSttrruuccttuurreeThe pylon legs are steel pipe sections of

30” outside diameter and 5/8” wallthickness. The material is of 36 ksi yieldstress. The lower 12’ of each leg is filledwith concrete to improve resistance totraffic impact.

The suspended structure is framed insteel. The main longitudinal girders areW27 rolled beams, 12’ apart. W14 floor


OOlldd PPllaannkk RRooaadd TTrraaiill BBrriiddggeeFrankfort, Illinois

Prize Bridge Award: Special Purpose

Jurors Comments

Unique use of skewed A-frame pylon to

suspend a plate girder superstructure. A light,

airy open design...a unique through-the-leg

superstructure...Very interesting concept.


beams at 12’ centers span between thelongitudinal girders and support a cast-in-place reinforced concrete deck. Thegirders and floor beams are of Grade 50steel. Shear studs connect the steel fram-ing to the concrete. The overall depth ofthe suspended structure, excluding thecustom-designed railings, which arelargely open and visually transparent, isonly 27”.

Four hangers support the suspendeddeck structure, each a 1½” diameterbridge strand, with standard open strandsockets at both ends.

The pylon is supported at the base ofeach leg by battered and vertical piles.An integral abutment design, with verti-cal piles at each abutment, is used for thedeck structure. Internally reinforcedearth walls are used for the abutmentsand wing walls.

The designers of the OPRT Bridgedecided not to use plastic encasement orother heroic measures for protection of

the hangers from corrosion. Instead, thehangers were made easily inspectableand replaceable. The bridge was designedto permit removal of one or all of thehangers with a single temporary supportin the median of U.S. Route 45. Thisdesign feature, which required little addi-tional strength in the structure, was alsoexpected to be useful during erection ofthe bridge.

DDeessiiggnn CCrriitteerriiaa aanndd SSttrruuccttuurree BBeehhaavviioorrCurrent AASHTO, Guide

Specifications for Design of PedestrianBridges, were used for design of thebridge. The design live load was a distrib-uted pedestrian load or a single H-10truck. The design was based on completethree-dimensional analysis with finiteelements representing the deck (thisdesign did not differ significantly from apreliminary design based on a simple“back-of-an-envelope” analysis).

The calculated live load deflections

(2.3’ maximum) and the combination ofnatural frequency (1.0 hertz) and massare well within the recommendations inthe AASHTO, Guide Specifications.

AAnnaallyyssiiss ooff CCoossttThe OPRT Bridge was advertised, bid

and contracted as part of a much largerproject (with a total construction cost ofabout $10 million). The four bidsreceived were within a 10% band, butthe cost of bridge items in the bidsranged from about $422,000 to$857,000. This suggests an artificialbreakdown of prices by the bidders andmakes it difficult to reliably isolate thecost of the bridge from the overall bidprices. However, the bid prices supportestimates prepared during design, whichindicated that a conventional crossingwith a pier in the median of U.S. 45would have cost about the same as thedesign that was adopted. The strikingappearance and the elimination of thecenter pier and the related safety benefitswere achieved at little or no extra cost.

OOtthheerr PPootteennttiiaall AApppplliiccaattiioonnssThe diagonal-pylon concept devel-

oped for the OPRT Bridge is applicableto a wide range of crossings for roadwaysand walkways over land or water andshows a design that was proposed recent-ly for a 40’ wide roadway crossing over arail yard in Chicago—a solution aban-doned for urban-planning reasons infavor of a tunnel.

Though the full benefit of the diago-nal-pylon concept will not be realized inbridges that are not skewed the conceptmay prove to be a viable alternative toconventional designs even for certainnon-skewed crossings.

HHiigghhlliigghhttss ooff OOPPRRTT BBrriiddggee DDeessiiggnnThough the bridge is skewed, the

main load carrying component, thepylon, spans the shortest distance acrossthe highway below.

The clear span under the bridge isbetween the legs of the pylon, ratherthan on each side of it as in conventionalcable-stayed bridges.

The large angle between the plane ofthe pylon and the deck structure, theskew, allows the deck to restrain or“brace” the pylon in the out-of-planedirection. Thus, the overall structuralconcept is one in which the pylon sup-ports the deck vertically while the decksupports the pylon laterally.

The challenge presented by theextreme skew of the crossing was turnedinto an advantage through this uniquestructural design.

The cost is comparable to that of aconventional bridge with an additionalpier at the center of the crossing.

The structural concept developed forthis bridge is applicable to a wide rangeof skewed crossings for roadways andwalkways over land or water.

Project TeamOwner

Illinois Department ofTransportation

DesignerTeng & Associates, Inc.

Steel FabricatorIndustrial Steel Construction,Inc.

Steel DetailerB & D Detailing Inc.

Steel ErectorAngus Contractors Inc.

General ContractorK-Five Construction Corp.

Consulting FirmHerlihy Mid-Continent Co.


The Fore River is an importantnavigable waterway serving bothcommercial shipping and recreation-al boating activities of the Portland-South Portland area. The old mov-able bridge spanning the navigationchannel was a two leaf Sherzerrolling bascule type providing achannel clearance of only 98’ hori-zontally and less than 24’ abovemean high water vertically when thebridge was closed. The draw spanprovided a narrow entryway with lessthan 5’ side clearances, at times, forlarge tankers and cargo ships todelivering oil and cargo to the termi-nals located in the upper Fore River.The bridge is also an integral part ofthe area’s transportation networkwith over 30,000 vehicles per daytraveling between the two cities.

Public debate about replacing the oldbridge started as far back as 1951.Numerous studies were conducted toevaluate the deteriorating structural con-dition of the old bridge and to determinethe feasibility of rebuilding or replacingit, including the possibility of a tunnelcrossing. Other studies focused on navi-gational needs and potential navigationimprovements that would be provided bya bridge replacement.

It was not until 1987 that a plan toreplace the old bridge was accepted bylocal, state and federal officials, clearingthe way for the design and constructionof the Casco Bay Bridge.

The Casco Bay Bridge is the MaineDepartment of Transportation’s largestbridge construction project to date. The4,748’ long structure includes a mid-levelmovable bascule span over the naviga-tional channel of the Fore River thatflows into Casco Bay. The span is one ofthe largest of its type in North Americaand it is a trunnion bascule with a cen-ter-to-center trunnion distance of 285.5’.The new span has a horizontal channelclearance width of 60 m (196.85’), over100’ wider than the old movable span,making the passage through the bridgesafer for navigation. The new span is alsohigher providing 65’ of vertical clearanceat the center of the channel, with thebridge in the closed position, thusdecreasing the number of openings of the


CCaassccoo BBaayy BBrriiddggeePortland, Maine

Prize Bridge Award: Moveable Span

Jurors Comments

Innovative...unique trunnion strut, graceful lines

and aesthetic pier shape...excellent

presentation to make a moveable bridge

aesthetically appealing.

span and reducing delays to bridge users.

BBaassccuullee SSppaann DDeessiiggnnThe design of the bascule span incor-

porates the state-of-the art in bridgedesign and construction for structural,mechanical and electrical systems andconforms to both AASHTO’s, StandardSpecifications for Movable HighwayBridges, and Standard Specifications forHighway Bridges, 15th Edition, using adesign live load of HS25 and alternatemilitary loading. The specifications aresupplemented by the latest industry stan-dards applicable to each individual disci-pline.

ASTM A709, Grade 36 and Grade 50painted structural steel, was used for thebascule superstructure. Due to the size ofthe bascule leaves and the need for coun-terbalancing, it was beneficial to providean efficient structure which minimizesthe weight of the leaves where feasible toachieve an economical design. Thereduced mass of the leaves also results incost-effective design of the support sys-tem, balance system and drive system.Still, for the bascule leaves strengthdesign is not always the controlling fac-tor. Live load deflection of the can-tilevered leaves at mid-span had to becontrolled to minimize any potentialproblems with the span locks. Parabolic-shaped steel I-girders were chosen toconform to the moment envelope of thecantilevered leaves for efficient distribu-tion of materials and ease of fabrication.Similarly, the full-depth floor beamswere configured as trusses with readilyavailable rolled shape members designedto have adequate load carrying capacityas well as to provide torsional rigidity forthe entire movable leaf during span oper-ation. The floor beams support the galva-nized stringers, open grid decking, steelbarriers and steel sidewalks.

UUnniiqquuee FFeeaattuurreessEach bascule leaf is counterweighted

with a concrete-filled steel box at theheel end between the pair of I-girders.The box is 16’ × 19’ × 30’ and is formedwith 3/4” stiffened steel plates. Due tothe size of the counterweight, and the 78degree angle of opening needed for thebascule leaf, a sizable clear space had tobe provided between the supportcolumns to allow for the movement ofthe counterweight. The conventional bas-cule bridge pivot consists of a trunnionshaft through the girder web with sup-port bearings on each side of the web.This arrangement was not feasible forthis structure. An innovative concept wasadvanced to solve this problem and was


accomplished by the use of the trunnionstrut. A stiff space truss (referred to as thetrunnion strut) spans between each pairof support girders. At each end of thestrut a trunnion shaft penetrates the maingirder web to engage the strut in order totransfer the load of the bascule leaf to thesupporting trunnion bearing. The singlebearing at each girder is supported by anexterior column. This arrangementopened up an uninterrupted spacebetween supports for the movement ofthe counterweight. A large percentage ofthe steel used for the strut is distributedto the corners for efficient use of materialto provide a very stiff element with con-stant section property in any orientation.The required stiffness is used to controlthe deflection in order that camber andload distribution will not be a problem,thus controlling the alignment of thebearings.

The sizeable 1500 ton dead load perbascule leaf required support bearingscapable of supporting very heavy loadswhile limiting the size of the trunnionbearings. Special maintenance freespherical plain bearings with sliding con-tact surface combination of steel and spe-cial bronze was specified. The slidinglayer is composed of discs of bronze

material inserted in recesses milled intothe inner steel spherical convex surface.The special bearings, specifically manu-factured in the United States for this pro-ject, are capable of supporting very heavyradial loads and axial loads. These maybe the only bearings of this type used forbridge application in this country.

FFoouunnddaattiioonn aanndd SSuubbssttrruuccttuurreeAlthough alternate 7’ diameter drilled

shafts and H-pile foundations weredesigned for this bridge, the contractorselected the later for construction. Highbending capability required for the H-pile foundation resulted in the specifica-tion of A572 high strength HP14 × 117steel piles, reinforced with cover platesnear the tops of the piles. A total of 231piles were utilized for each bascule pier.A critical length of embedment of the H-piles was required to develop sufficientanchorage of the piles against lateralloads. Difficult pile driving conditionswere anticipated in the glacial till materi-al, based on available geotechnical infor-mation, but did not present any signifi-cant problems during construction.

A pair of unique, reinforced concretepiers were designed to emphasize theentrance to the harbor. The fully

screened and enclosed piers were desir-able due to their ability to protect thebridge’s operating machinery from theweather, as well as keeping out birds.The shape of the pier tops is more or lessdefined by the arc of travel of the coun-terweight within when the leaves open orclose. The reduced width of the lowerportion of the mid-level bridge piers alsoresulted in a savings of material.

PPiieerr PPrrootteeccttiioonnA pier protection system consisting of

four cellular sheet pile dolphin and fend-ers demarcating the boundaries of thechannel was designed to prevent, or atleast minimize, any damage to the bridgepiers due to vessel impact.

Concrete from the old bridge wasrecycled by processing the demolishedconcrete into a consistent gradation andused as granular fill for the cellularsheet-pile dolphins.

Clusters of 36” diameter fusion-bond-ed epoxy coated steel pipe piles andwales consisting of W24 × 117 rolledbeams form the protective fender systemalong each edge of the channel. Thewales were faced with ultra high molecu-lar weight (UHMW) polyethylene rubbingstrips for decrease vessel impact forcedue to the very low coefficient of friction.The UHMW material was also selectedfor its durability and resistance to deteri-oration.

Efficient energy absorbing kinematicrubber fenders were introduced at thepier locations to provide the minimumoffset of the fender, and maximize thechannel width opening to satisfy the nav-igational clearance requirements of theU.S. Coast Guard.

EElleeccttrriiccaall//MMeecchhaanniiccaallThe state-of-the-art electrical system

includes automatic control which is per-formed by the programmable logic con-troller (PLC) for sequencing of the vari-ous operating steps required by themovable span. Solid state speed controlsare also used to provide a higher degreeof accuracy in bridge movement.

The bridge drive machinery uses asingle enclosed drive arrangement foreach leaf to enhance reliability and mini-mize maintenance. The main motors andmotor brakes, including the auxiliarydrive system, were pre-assembled on thedrive unit in the manufacturer’s facilityin an attempt to provide more accuratealignment of the various components.

Unique “wet” type disc brakes werespecified for the bridge machinery. Thesecompact brakes provide an efficientbraking system and also have excellentcorrosion resistance.

AAeesstthheettiiccssSpecial consideration was given to the

visual impact of the bridge on the land-scape of Portland Harbor. An aestheticcommittee was established to provideinput and guidance to finding a designthat would complement its environmentand serve as a new landmark forPortland Harbor. By taking advantage ofthe long curvilinear alignment of the newstructure the design team endeavored toachieve the concept of a continuouslyflowing ribbon in space, punctuated onlyat the bascule span.

The treatment of the large basculepiers commanded the attention of twonationally renowned bridge architects.

The upper section of each bascule pierabove the shaft is shaped to conform tothe enclosed space required to accommo-date the movement of the counterweightas the span opens and closes. It also pro-vides a protective enclosure for the trun-nion bearings and the machinery whichoperates the span. The bascule span isviewed as an accent to the desired ribboneffect.

A special red color was selected forthe paint on the structural steel girders toenhance their appearance and blend inwith the red brick seen on many ofPortland’s waterfront buildings.


Project TeamOwner

State of Maine Departmentof Transportation

DesignerModjeski and Masters, Inc.

Steel FabricatorTampa Steel ErectingCompany

Steel DetailerTensor Engineering Co.

Steel ErectorCianbro Corporation

General ContractorsCianbro Corporation

Consulting FirmT.Y. Lin International

The bridge, located six kilome-ters northwest of downtown Chicago,is part of a $12.6-million improve-ment project along a section of NorthDamen Avenue. The mixed-useproperties surrounding the site arerapidly transitioning from factories tomini-malls and condominiums. Inview of this redevelopment, the cityof Chicago proposed to build a signa-ture bridge at this site to act as thefocal point for the overall public andprivate revitalization of the area.

Among the project’s innovations arethe arch ribs, which are freestanding andconstructed without lateral bracing.Additionally, the arch is not tied. Tiedarches represented potential durabilityand safety concerns for both the FederalHighway Administration and the city ofChicago, concerns which were avoidedby eliminating the tie.

BBrriiddggee DDeessccrriippttiioonnThe new structure spans 94 m over

the river and carries two lanes of traffic,with sidewalks along each side, in eachdirection. The two ribs are fabricatedfrom 1.2 m-diameter steel pipe that isformed into a compound circular curveusing induction heat bending. Each riblies in a vertical plane and is locatedbetween the roadway and sidewalks. Theribs have a constant wall thickness of 25mm throughout their length, and is filledwith concrete over a distance of 8 m ateach end in order to resist the higherthrust and moment near the springpoints.

The superstructure is comprised of alongitudinally post-tensioned, cast-in-place concrete deck and stiffening girdersthat are supported by transverse steel boxbeams. The transverse beams act com-positely with the deck. The beams aresupported from the ribs by structuralstrand hangers anchored at the bottomflange and attached to the ribs using steelgusset plates and an open socket. Thegusset plates penetrate the rib and arewelded to stiffener plates and bolted toangles to transfer the hanger forces into


DDaammeenn AAvveennuuee AArrcchh BBrriiddggeeChicago, Illinois

Prize Bridge Award: Medium Span

Jurors Comments

The use of bent, steel pipes for the arches

without lateral bracing is

innovative...aesthetically pleasing

the rib.The semi-integral abutments and rib

thrust blocks are founded on a commonreinforced concrete cap. Each cap is sup-ported by six 2.1 m-diameter drilledshafts that extend to bedrock.

IInnnnoovvaattiioonnssThe structure is a unique blend of

materials and components that aredesigned to result in a rapid speed ofconstruction, an aesthetically pleasingappearance and excellent long-termdurability. The concrete deck is post-ten-sioned and overlaid with a latex modifiedconcrete wearing surface to improve therideability and durability of the bridgedeck system. The longitudinal concretestiffening girders are connected to thetransverse steel floor beams using contin-uous post-tensioning clamping the twocomponents together to achieve structur-al continuity. This innovative method ofconnecting the steel floor beams to theconcrete stiffening girders greatly simpli-fied the fabrication and construction ofthe floor system and allowed each mater-ial to be used where it is most effective.

The ribs are freestanding and con-structed without lateral bracing. Thiseliminates the traditional cross bracingassociated with the design of convention-al arch bridges, which detracts from theclean appearance and elegance of a soar-ing arch rib, increases the constructioncost and represents a maintenance andperformance problem to the owner.

The ribs are unique in that they werefabricated from 1.2 m-diameter pipeinstead of a traditional box section that isfabricated using welded plates. Use of apipe section resulted in a significantreduction in wind pressure on the ribsand resulted in improved aesthetics.

The ribs were fabricated using aninduction heat bending process.Induction heat bending is commonlyused to fabricate large diameter utilitypipes but is not typically used to fabricatestructural bridge steel. After investigatingseveral concepts for fabrication of theribs, it was concluded that induction heatbending should be specified as the pre-ferred method.

Induction bending utilizes an induc-tion-heating coil to create a narrow, cir-cumferential heated band around thematerial to be bent. Once the heatedband has attained the desired tempera-ture the material is moved through thecoil at a predetermined speed. A radialarm that rotates about a central pivotpoint, and is clamped to the leading edgeof the pipe, applies the bending moment.


After the material passes through thecoil, an air or water spray quenches it.

SSoocciiaall aanndd EEccoonnoommiiccaall CCoonnssiiddeerraattiioonnssThe project was driven by the owner’s

desire to build an aesthetically pleasingstructure that added value to the sur-rounding community. The bridge hasbecome a catalyst for the overall publicand private revitalization of the area andstands as an identifier or signature of thecommunity as a whole.

This crossing of the Chicago Riverprovided an important access point to theriver, as well as to the city’s riverwalkdevelopment program, which is a longterm project ment to provide a continu-ous linear parkway and bike trail systemalong both sides of the river. The bridgespan was adjusted to provide for theriverwalk along both banks.

The existing bridge represented afunctional traffic problem to the city, dueto the importance of Damen Avenue as atransportation arterial. The existingbridge was in such poor structural condi-tion that traffic was restricted from fourto two lanes until it was replaced. A newbridge was needed, and was needed soon,as residential and retail developers wereadvancing new projects in the area. Thedesign and detailing of the bridge weretailored to maximize the opportunity foroff-site construction and large componenterection in order to minimize construc-tion time. This allowed the contractor tocomplete the construction and reopenthe bridge to traffic in just eight months.

The new bridge provides the publicwith a safe and reliable structure that atthe same time livens up their journeywith its dramatic appearance.

DDeessiiggnn PPrroobblleemmss aanndd SSoolluuttiioonnssThe owner’s goal of designing an arch

bridge that could be opened to trafficwithin eight months created a complexdesign and construction challenge.

Arch structures generally take longerto build than conventional bridgesbecause of the long lead-time required toprocure and fabricate the steel ribs.Therefore, in an effort to speed the con-struction process, the bridge configura-tion was optimized to minimize falseworkrequirements and strive to make thebridge self-supporting during each stageof construction. This resulted in the com-pletion of rib erection, hanger and beamerection, superstructure casting and post-tensioning, approach slab placement andtraffic control installations in approxi-mately one-and-a-half months. This is aremarkable construction scheduling andengineering achievement on behalf ofthe contractor that, in our opinion, wasfacilitated by the configuration anddetails of the structure.

Arches are exceptionally sensitive toplacement of unsymmetrical loads duringconstruction. The deck placement proce-dure was developed in such a way as tomaximize the contractor’s options fordeck placement, and minimize the poten-tial for overstressing the ribs during thedeck pour. The contractor ultimatelyelected to utilize dual finishing machinesand pumps working symmetrically fromthe center of the bridge outward, as origi-nally conceived by the team.

The bridge foundations were compli-cated considerably by the presence ofexisting underground structures, includ-ing a maze of timber piles supporting theexisting retaining walls. The new founda-tions had to be designed to account for

the difficulties of working around theseexisting piles. Drilled shafts with suffi-cient diameter were selected to deal withinterference with the existing piles.

Although the owner’s goals created acomplex design and constructionchallenge in the optimization of thestructure and meeting the project sched-ule, the final design resulted in a simpleform that utilizes conventional methodsof construction.

AAeesstthheettiicc CCoonnssiiddeerraattiioonnssA successful design is one that main-

tains a careful balance between techno-logical and aesthetic considerations. Theultimate goal must be to achieve harmo-ny with the surroundings with simpleforms and minimal current, as well asfuture resources. When this goal isachieved bridges can be a vital part ofthe community. Vital not only from thestandpoint of commerce, safety andmobility, but also as a landmark or trib-ute to the creativity, fortitude and tech-nological proficiency of the people whodesign, build, and use them. The city ofChicago recognizes this principle anduses bridges and other public worksbeautification projects as a tool to stimu-late commerce and revitalization of acommunity or area. Therefore, the visualand functional friendliness of the sitereceived considerable attention from thedesign team.

All architectural features weredesigned to enhance or compliment thenatural elegance of the arch form. Theribs are painted red and are highlightedat night with underlighting located in thedeck. Precast abutment towers withcarved granite caps are located at oppo-site corners of the bridge. Belvederes arelocated at the other two corners to pro-vide a location for pedestrians to stop andlook out over the river. A staircase wasconstructed at the northwest corner ofthe bridge to allow access to the futureriverwalk below. Ornamental handrailsare located along both sides of the side-walks and will be painted red to matchthe color of the ribs.

Careful attention was given to thespecifications regarding finish and colorof the precast and cast-in-place concreteon the bridge and approaches to ensureconsistent or complimentary textures andcolors. The color of an existing retainingwall was integrated into the overall struc-ture using a concrete stain. The contrac-tor was required to construct mock-upsfor approval of all critical concrete ele-ments prior to starting production.

MMeeeettiinngg CClliieenntt NNeeeeddss

The Damen Avenue Arch Bridge rep-resents the successful integration of all ofthe clients project goals relating to aes-thetics, speed of construction, con-structability, durability and cost. Thefinal contract documents were deliveredto the client on schedule.

The design facilitated the contractormeeting the owner’s schedule of openingthe bridge to traffic within eight months.The bridge has also received numerousawards and a very favorable architecturalcritique by the Chicago Tribune.


Project TeamOwner

City of Chicago Department ofTransportation

DesignerJ. Muller International

Steel ErectorSteppo Construction

General ContractorWalsh Construction Companyof Illinois

Engineering & Erection ProceduresDanny’s Construction Co.

Consulting FirmTranSystems Corp.

As water leaves the swift-mov-ing Saint Clair River, located at thesouthern tip of Lake Huron in theswift-moving Saint Clair River, itforms an international boundarybetween Ontario and Michigan. Foralmost 60 years, international accessbetween Port Huron, MI, and PointEdward, Ontario, has been providedby a cantilever truss bridge built nearthe north end of the river.

The Michigan Department ofTransportation(MDOT) and The BlueWater Bridge Authority in Ontario arejointly own and operate this cantileverbridge—each collects tolls from trafficentering the bridge, and traffic leavingthe bridge must pass through customsand immigration on each end.

DDeessiiggnn ooff tthhee NNeeww BBrriiddggee In 1993, the owners retained a design

team to develop studies and plans for thenew bridge. The first phase of the workto prepare engineering studies for thenew crossing and develop a study report.

The preliminary cross-section wasestablished as a three-lane deck withsidewalk, traffic barriers and pedestrianrailing. The preferred alignment adjacentto the existing bridge was set. All projectdocuments would be completed in SIunits. The design would conform to thenew AASHTO LRFD Bridge DesignSpecifications and major provisions of theOntario Highway Bridge Design Code(OHBDC), with the LRFD wing the pri-mary specification.

SSeelleecctteedd SSttrruuccttuurree For the main river crossing, a contin-

uous tied-arch was selected withapproaches of box girders and multi-girder spans. A requirement for the mainbridge construction was that the work bedivided equally between the owners, andthat the construction be equally dividedbetween a contractor from Canada andone from the United States in a joint ven-ture contract dictating that two fabrica-tors and two steel suppliers be required.A considerable effort was required duringthe design to ensure that the details,


SSeeccoonndd BBlluuee WWaatteerr BBrriiddggeePort Huron, Michigan

Prize Bridge Award: Long Span

Jurors Comments

Classic concept of semi-through arch

in a modern, simple and clean design...Side-by-

side technologies, 60 years apart...Elegant long

span structure.

materials, standards and procedures inthe plans were proper for construction inboth countries.

The main span deck is reinforcedconcrete for three traffic lanes and apedestrian sidewalk. The stringers arerolled beam sections made continuousand composite with the deck slab. Thefloor beams are welded I-sections withwelded transverse stiffeners. Steep road-way grades (4.65%) and channel clear-ance requirements resulted in a shallowsuperstructure depth, limiting the avail-able web depth for the floor beams,resulting in the need for intermediatefloor beams between vertical locations.Welded I-members were used for thefloor system lateral bracing.

Under dead load only, an uplift condi-tion would occur at the anchor span endbearings. A counterweight was added toprovide a positive reaction under allloading conditions, except the mostextreme live load case, and the bearingshere are designed to resist the upliftresulting from that case. The floor systemat the anchor end required modificationto accept a concrete counterweight.Intermediate stringers were added to thetypical cross-section in the two end pan-els. Stringer depth was increased to 36’ inthese two panels to support the concretemass. The stringers were coped over thefloor beams to accommodate theirincreased depth.

Power-driven, rail-mounted platformtravelers provide access to the undersideof the deck and floor system. One travel-er rests near the anchor piers at each endof the bridge, and each is capable of tra-versing the entire length of the archstructure. Access to the remainder of thebridge is provided by an integrated sys-tem of crosswalks, ladders, stairways, rail-ing and handropes. The special consider-ation given to access inside the tie girderresulted in forced ventilation, adequatelighting and special surface finishing ofthe interior.

A number of steel arch bridge spanshave been built, and many of these aresimple spans using a horizontal steel tiemember from end-to-end of the arch toresist the horizontal force of the arch, butless than six continuous tied-arch bridgeshave been previously used in NorthAmerica.

When the vertical load on the archvaries, some flexural strength and stiff-ness is required, since the arch cannotchange its shape to accommodate thechange. The tie member is commonlysupported by the arch so they can acttogether flexurally, and the bridge flooris commonly attached to the tie.


Since the tie girder and arch rib acttogether flexurally, it is possible tochoose, by selective proportioning, themember that will carry most of the flex-ural stresses. For this design, the tie gird-er, which directly supports the bridgedeck, was chosen to be the principalmember and it is proportioned to be con-siderably stiffer than the arch rib.

This bridge layout consists of severalbasic segments: the main support framingconsists of the end segments made up ofthe anchor spans (85 m) and those por-tions of the main span extending fromthe main pier to the knuckle joints (36m); the middle segment or main arch(209 m) between the knuckle joints (basi-cally independent, closed units, exceptfor the flexural continuity of the tie gird-er and arch rib at the knuckle joint);steel vertical columns and hangers con-nect the arch rib and the tie girder; andsteel floor beams supporting the steelfloor stringers are attached to the tiegirders.

AArrcchh DDeettaaiillss The continuous tied-arch requires a

number of special design considerations,as do the LRFD requirements, and thedemands of the owners for this crossing.

The arch rib is a box about 1.2 m ona side made of welded steel plates, andnear each end is a welded closure plateto seal the main length of the arch ribmembers. These sealed sections are notpainted, but they have been partiallyevacuated, then filled with dried air andsealed. Pressure test points are located inthe end portions of the members forlong-term monitoring of interior pres-sure.

The tie girder is a steel box built upby bolting, and consists of steel plateswith corner connecting angles it is about1.2 m wide by 2.5 m deep. The tie girderis the tension member that provides thesole horizontal support for the entirearch. In addition, the tie grinder pro-vides most of the flexural resistance ofthe arch segments, it is the quintessentialfracture critical member. Mitigation mea-sures were proposed in the study reportto make this tied-arch structure, thenunder federal moratorium, acceptable tothe owners. Clearly, mitigation measurestranslate into additional, necessary costs.If the tie were a steel box assembled bywelding, it is possible that, under theimpact of varying loading, a crack mightpropagate across the entire member(using the welds as a path from one plateto the other). For this reason, it wasdecided that the tie girder would notcontain any welding but rather, would beassembled by high-strength bolts. Evenwith such measures a potential crackcould propagate across one of the platesor elements of the tie girder. Therefore,as a safeguard, the tie girder was propor-tioned so that it could withstand the lossof any one plate or element. These mea-sures gave the tie girder the internalredundancy desired and removed thespecter of fracture-critical fabricationrequirements.

Temperature changes and loads onthe bridge cause movements at the sup-ports. The main arch bearing in Ontariois fixed against sliding with the othersdesigned for longitudinal sliding. Thecapacity for sliding is provided by incor-porating Teflon on polished stainlesssteel within the bearing. At the Michigan

main pier, this bearing design accommo-dates movement of over 300 mm con-traction and over 400 mm expansion. Atough flexible disk in compression is apart of the bearing’s support for verticalload, and permits the small rotation thattakes place at the support joints.

In addition to the bolting used toassemble the tie girder, all the memberconnections are made with high-strengthgalvanized bolts The paint system usedon the bridge consists of a coat of zinc-rich primer, a second coat of epoxy and atop coat of light grey urethane. Theprimer was shop-applied to all surfaces ofcompleted members with the final twocoats were shop-applied to all, exceptfaying surfaces at field connections.

AArrcchh EErreeccttiioonn Erection from the water, which would

have been difficult due to the speed ofthe current, was banned by the U. S.Coast Guard. The design plans included afeasible erection procedure in accor-dance with LRFD specifications. First,under this plan, the anchor span waserected using temporary bents and thenplaced a falsework tower over the mainpier. Erection of the main span wasaccomplished by cantilevering from thispoint, using stays secured at the anchorpier and passing over the tower to sup-port the river span sections.

Each half of the arch was erected by acontractor from that country. To handlethe uplift created by the cantilevering,special tie rods were set into the anchorpier footing and for attachment to the tiegirder at the point of the stay attachment.

LLRRFFDD SSppeecciiffiiccaattiioonnss The bridge was designed using the

1994 AASHTO LRFD Bridge DesignSpecifications. The completed edition wasreleased shortly before the start of finaldesign. Specific project design criteria,begun during the study phase, weredeveloped and shown on the plans.These began by establishing the LRFD asthe basis for design and continued withfurther definition and refinement, allspecific to this project.

The loadings and traffic patterns onthe existing bridge had been studied bythe design consultant previously, thefindings were a fairly common condition,bumper-to-bumper traffic, with a highproportion of trucks over the full-lengthof the main bridge and approaches, wait-ing to pass immigration and customs. Theexperience with this bridge was one ofthe reasons that the LRFD specificationscontains a “Strength II” load conditionwhere in a special loading applicable to aspecific bridge is used. The special load-ing condition, as selected and included inthe design criteria, consist of loading anytwo lanes uniformly with an intensity of24 kN/m centered in each lane with noconcurrent load in the third lane or side-walk, no superimposed concentratedloads and no impact.

None of the arch segments carries itsload as an arch until the segment isclosed, or joined, with the tie. Until thatis achieved, the members are all merelybeams requiring falsework and tempo-rary support. The detailed erectionsequence shown in the plans included:staging; falsework and temporary bracinglocations; temporary bracing locationsand loadings; deflections and procedures

for making closures of the several seg-ments of the tied-arch. The final designand detailing of the permanent membersof the tied-arch was checked and adjust-ed to accommodate the loadings from theconstruction sequence.

The design criteria indicates therequirements for deck replaceability, andthe plans include staging diagrams forthe feasible procedure applicable to eachpart of the bridge.

Project TeamCo-Owners

Michigan Department ofTransportation & Blue WaterBridge Authority

DesignerModjeski and Masters, Inc.

Steel FabricatorsPDM Bridge and CanronConstruction Corp.

Steel ErectorCanron and Traylor Brothers

General ContractorsPCL/McCarthy, A jointVenture

prize bridge award: reconstructed new yyork rroute 3367

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