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T H E C O N C R E T E B R I D G E M A G A Z I N E

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S P R I N G 2 0 0 9

I-76 ALLEGHENY RIVER BRIDGENear Pittsburgh, Pennsylvania

FORTY FOOT PEDESTRIAN BRIDGETowamencin Township,

Montgomery County, Pennsylvania

RICHMOND HILL BRIDGEConifer, Colorado

MINNESOTA I-35W/HWY 62

CROSSTOWN PROJECTCrosstown Commons, Minnesota

FULTON ROAD BRIDGE REPLACEMENTCleveland, Ohio

COTTON LANE BRIDGEGoodyear, Arizona

40thStreetBridgeTampa, Florida
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Bentley/LEAP . . . . . . . . . . Inside Front Cover

Bridge Software Institute . . . . . . . . . . . . . 29

Campbell Scientific . . . . . . . . . . . . . . . . . . 43

DSI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

FIGG . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

General Technologies Inc . . . . . . . . . . . . . . . 4

Headwaters Resources . . . . . . . . . . . . . . . . 48

Larsa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

PB . . . . . . . . . . . . . . . . . . . . Inside Back Cover

PCAPCABA . . . . . . . . . . . . . . . . . . Back Cover

PCI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41, 45

Shuttlelift . . . . . . . . . . . . . . . . . . . . . . . . . . 13

Simone Collins Inc. . . . . . . . . . . . . . . . . . . 25

Splice Sleeve . . . . . . . . . . . . . . . . . . . . . . . . 47

T.Y. Lin International . . . . . . . . . . . . . . . . . 21

ThyssenKrupp . . . . . . . . . . . . . . . . . . . . . . . 17

Williams Form Engineering Corp. . . . . . . . 17

Advertisers Index

ASPIRE S i 2009

C O N T E N T S

Photo: FIGG.

Photo: Simone Collins Inc. Landscape Architecture.

P h o t o : S t a t e H i g h w a y 4 5 I n t e r c h a n g e P B S & J

Photo: PBS&J.

FeaturesPBS&J Standardizing Success 8PBS&J creates innovative solutions by focusing onefficiency, constructability, and long life.

I-76 Allegheny River Bridge 18New Pennsylvania Turnpike Bridge balances aesthetics,economy, and environmental sensitivity.

Forty Foot Pedestrian Bridge 22Integrating Art and Engineering in Public Infrastructure.

Richmond Hill Bridge 26Constant-depth bottom flanges on precast concreteU-girders were converted to a variable depth at thesite to reduce fabrication and transportation costs.

Minnesota I-35W/Hwy 62 Crosstown Project 30Precast segmental construction offered the mostadvantages and was the most attractive option.

Fulton Road Bridge Replacement 34Cotton Lane Bridge 38Combination of local government and developersproduces decorative, cost-efficient bridge design.

Social, Economic, and Ecological Benefitsof Sustainable Concrete Bridges

DepartmentsEditorial 2

Reader Response 4

Concrete Calendar 6PerspectiveSustainabilityGet In, Get Out, and Stay Out 14

Aesthetics Commentary 33

Safety and Serviceability 42

Concrete Connections 44

COUNTYLee County, Florida 46

AASHTO LRFD Specifications 48

8

22

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Photo: Ted Lacey Photography.

John S. Dick,Executive Editor

2 | ASPIRE S i 2009

EDITORIAL

As ASPIRE goes to press, the AmericanRecovery and Reinvestment Act of 2009 (also

known as the Stimulus Act) has been signed intolaw. Whether it will accomplish its intended purposeremains to be seen. However, one thing is certain:

A great many highway and bridge projects will getunderway very soon. Many of these bridges will beconstructed with concrete components, for a range ofgood reasons.

An early assessment indicates some $26.6 billion

will be apportioned to the states for highways andbridges. These funds are in addition to contractauthority provided in FY 2009 and FY 2010. Therules are specific concerning percentages of fundsthat need to be obligated by the agencies within aspecified period of time, time frames for start-up andcompletion of projects, and so forth. But that is beyondthe scope of our concern here.

What is impor tant to understand is that theconcrete industry is poised to respond to this potential

flood of demand. Responsiveness always has beena hallmark of the industry, and it was especially

important during recent natural disasters and overthe past several years when the supply of constructionmaterials was erratic at best.

The owner agencies have increasingly turned toconcrete solutions. In 2008, the Federal Highway

Administration (FHWA) reported statistics taken fromthe 2005 National Bridge Inventory (NBI), the mostrecent year for which complete data are available.For all new and replaced bridges constructed that

year, concrete constituted a 65.5% share based onthe area of decks. Based on the numbers of bridges,concrete accounted for 76.2% of bridges built in 2005.This percentage has continued to increase throughthe years.

There are many reasons for the growth of concretebridges in the United States. Some of these include:

Wide-spread use of high performance concrete,whi ch provi des inc rease d con fid enc e inexceptional long-term performance.

Freedom from routine maintenance and itsinterference with traffic.

Improved efficiencies in construction methodsand in the production of materials, andproductsresulting in lower unit costs.

Confidence concerning supply and relative pricestability.

Exciting solutions that expand the range ofapplications for concrete.

Sensitivity to creating sustainable solutions.

Capability for a wider range of aestheticexpressions.

The ability to meet ever-increasing demandto construct quickly, with improved quality, toreduce the duration of work-zone interference.

ASPIRE is dedicated to bringing to its readers, abroad spectrum of real solutions that illustrate thebenefits achieved with concrete bridges across a widerange of challenges, geographies, and stakeholders.

This issue features examples of how concrete canbe used for long-span bridges or short-span bridges;highway bridges or pedestrian overpasses; andinterstate bridges, urban bridges, or rural bridges.

We hope the stimulus program helps you toproduce more bridges in the coming year, and wehope our efforts at ASPIREgive you new ideas for howto meet those needs quickly, cost effectively, and inaesthetically pleasing ways.

We valu e your opinion about how we aresucceeding. We invite you to share your impressionsand comments about ASPIREmagazine with us. Youcan send an email from www.aspirebridge.org, or evenbetter, fill out the quick survey reached by selectingthe Survey button at www.aspirebridge.org. It offersmultiple-choice and fill-in-the-blank questions. Itlltake less than 5 minutes to complete.

Executive Editor:John S. Dick

Managing Technical Editor:Dr. Henry G.Russell

Managing Editor:Craig A. Shutt

Editorial Staff:Daniel C. Brown, Roy Diez

Editorial Administration:James O. Ahtes Inc.

Art Director:Mark Leader, Leader GraphicDesign Inc.

Layout Design:Marcia Bending, LeaderGraphic Design Inc.

Electronic Production:Chris Bakker,Jim Henson, Leader Graphic Design Inc.

Ad Sales:Jim OestmannPhone: (847) 838-0500 Cell: (847) 924-5497 Fax: (847) [email protected]

Reprint Sales:Mark Leader(847) 564-5409

e-mail: [email protected]

Publisher:Precast/Prestressed Concrete Institute,

James G. Toscas, President

Editorial Advisory Board:Susan N. Lane,Portland Cement Association(PCA)

John S. Dick,Precast/Prestressed ConcreteInstitute (PCI)William R. Cox,American Segmental BridgeInstitute (ASBI)

Dr. Henry G. Russell,Managing Technical Editor

POSTMASTER:Send address changestoASPIRE, 209 W. Jackson Blvd., Suite 500,Chicago, IL 60606. Standard postage paid atChicago, IL, and additional mailing offices.

ASPIRE(Vol. 3, No. 2), ISSN1935-2093ispublished quarterly by the Precast/PrestressedConcrete Institute, 209 W. Jackson Blvd., Suite500, Chicago, IL 60606.

Copyright 2009, Precast/Prestressed ConcreteInstitute.

If you have a project to be considered forASPIREsend information toASPIRE,209 W. Jackson Blvd., Suite 500,Chicago, IL 60606phone: (312) 786-0300

www.aspirebridge.orge-mail: [email protected]

Cover:40th Street Bridge, Tampa, Fla.Photo: PBS&J.

Stimulus Act and theBenefits of Concrete Bridges

Log on NOW at www.aspirebridge.organd take theASPIRE

Reader Survey.

Precast/PrestressedConcrete Institute

Portland CementAssociation

American Coal AshAssociation

Expanded Shale Clayand Slate Institute

Silica FumeAssociation

1American Segmental

Bridge Institute
mailto:[email protected]:[email protected]://www.aspirebridge.org/mailto:[email protected]://www.aspirebridge.org/http://www.aspirebridge.org/http://www.pci.org/http://www.pci.org/http://www.cement.org/bridges/http://www.cement.org/bridges/http://www.acaa-usa.org/http://www.acaa-usa.org/http://www.escsi.org/http://www.escsi.org/http://www.silicafume.org/http://www.silicafume.org/http://www.asbi-assoc.org/http://www.asbi-assoc.org/http://www.asbi-assoc.org/http://www.asbi-assoc.org/http://www.silicafume.org/http://www.escsi.org/http://www.acaa-usa.org/http://www.cement.org/bridges/http://www.pci.org/http://www.aspirebridge.org/http://www.aspirebridge.org/mailto:[email protected]://www.aspirebridge.org/mailto:[email protected]:[email protected]


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Creating Bridges As Art

I-76 Allegheny River Bridge

near Pittsburgh, PA

Owner:

Pennsylvania TurnpikeCommission

Designer:FIGG

Contractor:Walsh Construction Company

Pennsylvanias first

balanced cantilever bridge

provides an aesthetically

pleasing and environment

friendly crossing for

Turnpike customers.

Long spans of 285, 380,

380, 444, 532, and 329and curved piers with

stone texturing are

in harmony with the site.

Environment sensitive design

protects aquatic habitats

and preserves

archeological areas.

Completion planned

for early 2010.

Join the firm whosecustomers have received over

300 design awards for

sustainability, cost-efficiency,

speed of construction and

aesthetic beauty. If you share

our passion for creating bridges

as art, please contact us at

1-800-358-3444.

www.figgbridge.com

Pennsylvanias

Longest Concrete

Segmental Span

An Equal Opportunity Employer

An Environment Friendly Bridge
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THE CONCRETE BRIDGE MA GA ZINE

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WINTER 2009

MAPLEAVENUEBRIDGERedmond,Oregon

FOLSOMLAKECROSSINGFolsom,California

KANAWHARIVERBRIDGEKanawhaCounty,West VirginiaPORTCOLUMBUSINTERNATIONAL AIRPORTCROSSOVERTAXIWAYBRIDGE

Columbus,Ohio

CanyonParkFreewayStationBridge

Bothell,Washington

4 | ASPIRE S i 2009

READER RESPONSE

Editors,

Again thank you for the opportunity to contribute

to your magazine. The latest issue was terrific.

William Collins, vice presidentSimone Collins Inc. Landscape Architecture

Berwyn, Pa.

Editor,

ASPIRE is my favorite technical magazine!

Tim ShellKPFF

Portland, Ore.

Editor,

I am an editor in CH2M HILLs Boise office. I

would like to download the PDF of the article

on Rainbow Bridge and link to it in our office

newsletter. John Hinman, the author, is in our

office.

Eric OdenCH2M HILL

Boise, Idaho

Editors,

Ive had a couple people comment to me in

the last few days about how much they like

ASPIRE. You guys are obviously doing some-

thing right.

Fred Gottemoeller, principalBridgescape

Columbia, Md.

Editor,

Just wanted to say Thanks !! for sending

us the copies of the ASPIRE magazine that

includes the NH article. It is well presented

and formatted, and I was glad to see that the

photos were clear and sharp. Thanks for the

opportunity of having NH prepare an article

for ASPIRE.

Mark W. Richardson,Administrator, Bridge Design Bureau

NH Department of TransportationConcord, N.H.

Editor,

wanted to let you know we thought the

article turned out great (Custom Arches,

ASPIRE, Winter 2009, p.18). Our engineer

in particular was pleased. He was especially

excited about the Aesthetics Commentary

by Frederick Gottemoeller who got what we

were trying to do. Mr. Gottemoeller really

understood our objectives and expressed them

so well.

OBEC Consulting EngineersEugene, Ore
mailto:[email protected]://www.gti-usa.net/


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mailto:[email protected]://www.larsa4d.com/


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Photo:TedLaceyPhotography.

6 | ASPIRE S i 2009

CONCRETE CALENDAR 2009/2010

April 20-21, 20092009 ASBI Grouting Certification TrainingJ.J. Pickle Research Campus

The Commons Center, Austin, Tex.

April 22-26, 2009PCI Committee DaysWestin Hotel, Chicago, Ill.

May 4-7, 2009World of Coal Ash (WOCA 2009)Lexington Convention Center, Lexington, Ky.

May 11-15, 2009PCI Quality Control & Assurance Schools, Levels I, II & IIICertified Field Auditor and Industry Erection Standards Schools

Sheraton Music City Hotel, Nashvi lle, Tenn.

May 31, 2009The Fifth International Conference on Bridge Maintenance, Safety and ManagementAbstracts due May 31, 2009, for IABMAS2010, to be held July 11-15, 2010Loews Philadelphia Hotel, Philadelphia, Pa.

June 14-19, 2009International Bridge ConferenceDavid L. Lawrence Convention Center, Pittsburgh, Pa.

June 15, 2009fib International Congress (hosted by PCI)

Abstracts due June 15, 2009, for this event, to be held May 29-June 2, 2010Gaylord National Resort & Convention Center, National Harbor, Md.

July 5-9, 2009AASHTO Subcommittee on Bridges and Structures Annual MeetingHilton Riverside Hotel, New Orleans, La.

September 13-16, 2009PCI-FHWA National Bridge ConferenceMarriott Rivercenter Hotel and Henry B. Gonzales Convention Center, San Antonio, Tex.

September 21-23, 2009Western Bridge Engineers Seminar

Sacramento Convention Center and Sheraton Grand Hotel, Sacramento, Calif.

October 25-27, 20092009 ASBI 21st Annual ConventionHilton Hotel, Minneapolis, Minn.

November 8-12, 2009ACI Fall ConventionMarriott New Orleans, New Orleans, La.

January 10-14, 2010Transportation Research Board Annual MeetingMarriott Wardman Park, Omni Shoreham, and Hilton Washington, Washington, D.C.

CONTRIBUTING AUTHORS

Dr. Henry G. Russellis an engineering consultant,

who has been involved with the applications of concrete in

bridges for over 35 years and has published many papers

on the applications of high performance concrete.

MANAGINGTECHNICAL EDITOR

Dr. Dennis R. Mertzis

professor of civil engineering

at the University of Delaware.

Formerly with Modjeski and

Masters Inc. when theLRFD

Specificationswere first written,

he has continued to be actively

involved in their development.

Craig Finleyis founder and

managing principal of Finley

Engineering Group Inc. (FINLEY),

a bridge and construction

engineering firm based in

Tallahassee, Fla. A two-time

winner of the ASBI Leadership

Award, Finley has participated on some of the most noted

precast segmental projects of the last 25 years.

Frederick Gottemoeller

is an engineer and architect,

who specializes in the aesthetic

aspects of bridges and

highways. He is the author

ofBridgescape, a reference

book on aesthetics and was deputy administrator of the

Maryland State Highway Administration.

For links to websites, email addresses,or telephone numbers for these events,

go to www.aspirebridge.org.
http://www.aspirebridge.org/http://www.aspirebridge.org/


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ASPIRE S i 2009

AM ERICAN SEGM EN TAL BRIDGE IN ST I TUTE

Mark Your Calendar Today!For these two important1events.April 20-21

2009 Grouting Certification Training

J.J. Pickle Research Campus

University of Texas, Austin

For further details visit www.asbi-assoc.org

October 25-27

2009 ASBI Convention

Hilton Minneapolis

i i

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FOCUS

Many complex, long-span structuresreceive plaudits for innovative conceptsthat stretch bridge design and materialproperties. PBS&J has done its share ofsuch projects, but its designers pridethemselves more on their ability to bringinnovation to the more conventionalstructures that are designed every day. Andtheir work to standardize components andextend durability attributes help createmore efficient and economical designsthat benefit the industry.

Clients come to us because of ourgeneral design philosophy, whichis to create safe designs that are

constructable, explains Amir Kangari,national transportation structuresdirector in the firms Tampa, Fla.,office. Probably most important, inthis litigious environment today, weaim to create high-quality, error-freeconstruction documents that providean economical solution thats innovativeand holistic to the overall transportationneed, not just a bridge that connectstwo points. We apply this philosophyin all of our bridge designs throughoutPBS&Js varied client base, whichincludes surface-transportation, airports,transit, and pedestrian and wildlife-crossing type projects.

PBS&J creates

innovativesolutions by

focusing on

efficiency,

constructability,

and long life

PBS&JSTANDARDIZING SUCCESS

by Craig A. Shutt

8 | ASPIRE S i 2009


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The design for the new taxiway at

the Cincinnati/Northern KentuckyInternational Airport features a

cast-in-place voided-slab concrete

deck superstructure with a 4.5-ft

structural depth to maximize

clearance for an existing underpass.

Post-tensioning eliminated the need

for an intermediate pier, allowing

future expansion of the road.

The 40thStreet Bridge in Tampa,

Fla., features a single post-tensioned

concrete span with special aesthetic

treatments created by local high-school

art students. They learned the basics ofconceptual design, and contest winners

had their designs ideas, colors, and

shapes incorporated into the formal

aesthetic plan.

Adds Joseph McGrew, division managerfor national transportation structures inthe Atlanta, Ga., office, One key goalis constructability. We are always lookingfor opportunities to save money duringconstruction by better understanding

the concerns of the contractor who isconstructing our design.

That focus has led the firms designersto specify concrete components mostoften, he says. The majority of ourdesigns use concrete, with a mix ofboth cast-in-place and precast concretedesigns. The final design often plays tothe regions own strengths, notes RamKozhikote, group manager of structuresin the Orlando, Fla., office. It dependson the availability of precast concrete

plants in the area and what contractorsare most familiar with, he explains. Inthe East and South, precast concretedesigns predominate, whereas WestCoast designs often feature cast-in-place concrete. We are working withthe precast industry in many regionsto revamp I-girder shapes to be moreefficient and competitive.

Concretes flexibility allows us todo things we couldnt do with steelstructures, agrees Glenn Myers,principal technical professional inthe Fort Lauderdale, Fla., office. Wecan cast any shape needed, whichgives us the ability to overcome manychallenges.

An example can be seen in the designfor the north taxiway at the Cincinnati/Northern Kentucky International Airportin Erlanger, Ky. The single-span, 214-ft wide cast-in-place concrete bridgeallows planes weighing up to 1.6 millionpounds to traverse its length, spanningan existing two-lane service road that

ultimately will widen to four lanes. Thebridge required a shallow profile due tothe existing roadway beneath.

During the planning phase, designerssuggested a shal low voided-slab

concrete deck superstructure post-tensioned in both longitudinal andtransverse directions. This designaddressed several issues, includingconstruction efficiency and low, long-term maintenance needs, says Kangari.We created a longer, more open spanwith no intermediate pier, so it doesntbox in the client for future expansion.

Such spans show concretes flexibilityand are becoming more common, thedesigners note. Concrete is a mucheasier material with which to designunusual shapes than other materials,says McGrew. Kozhikote agrees. Manyof our bridge projects are in the mid-length span range, and the concretedesigns compete very effectively withsteel. And now segmental precastconcrete girders are helping to eliminateany disadvantage for longer spans aswell.

One key goal is

constructability.

ASPIRE S i 2009


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PBS&Js work for the State Highway

45 Interchange project in Austin, Tex.,

features full program-management

services on the diamond interchange

consisting of 10 major bridges and

structural designs for several high-

level structures, and a double-deck

structure with on/off ramps. Precastconcrete beams were used for all of

the bridges superstructures. Photos:

PBS&J.

New Standards ComingTo encourage that competition, PBS&Jand others in the precast industry areworking with the central office of theFlorida Department of Transportation toimplement new standards for prestressedconcrete beams, with the goal of extending

their span range to 200 ft. The designs willtake their cue from girders being used inother states, Myers notes. New shapesand higher concrete strengths are allowingus to look at concrete for more efficientdesigns, he says. This work will createa more competitive alternative and opennew design options.

But while PBS&J creates its share oflong-span designs, it shines brightest onits work with midrange, conventionaldesigns. Bringing their innovativeconcepts to these designs creates greatchallenges, says Kangari. All of ourclients are looking for innovative ideas,and to create innovative designs that helpachieve their goals within a conventionaldesign is our greatest challenge.

Long-span, complex bridges offer greater

freedom to create innovative designs, he

notes, because theyre expected in thatcontext. But to convince bridge ownersto use new concepts for designs thatare done day in and day out provides amuch greater challenge, because of theexpected boundaries. It forces us to useall of our creativity in the concept-studyand preliminary-engineering phasesThose portions have become prettyrobust as we engage the client with ourideas for achieving the goals in the mostefficient manner.

An example can be seen in PBS&Js workon the State Highway 45 Interchange inAustin, Tex. The firm provided full program-management services over a 10-yearperiod for the 16.7-mile-long roadwayimprovement project involving 10 majorbridges. In addition, PBS&J providedstructural designs for a portion of the

project including a double-deck structureusing precast concrete Type IV AASHTOgirders with simple spans and conventionallyreinforced concrete straddle bents.

The straddle bents unique shape,requested for aesthetic reasons, waseffectively utilized to create a moreefficient structural design. Piers receiveda special aesthetic treatment, includingashlar stone patterns. It was a simpledesign, which had many aestheticfeatures and the creative touches thathelped its efficiency, says McGrew.

New shapes and higher concrete strengths

are allowing us to look at concrete for more

efficient designs.

10 | ASPIRE S i 2009


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The I-4/Lee Roy Selmon Crosstown Connector in Tampa, Fla., will create a new interchange

between the two freeways. Six PBS&J bridge design teams from different offices are

providing the design work, which will feature both steel and concrete options. The concrete

option will utilize a combination of segmental construction and cantilevered post-tensioned

spliced concrete beams. Standardized components throughout the project will greatly

reduce costs. The project is expected to be let for construction in summer 2009 and take up

to 5 years to complete.

and web thickness. Utilizing this creative

approach, the PBS&J segmental designexperts substantially reduced the estimatedcost of the concrete option.

By standardizing sections in both typesof construction and using similar cross-sections, we reduced costs substantially,McGrew says. Standardization also resultedin the capability to use typical pier widths,allowing a great deal of repetition for piers,which added to the savings. Designers alsoselected one size of drilled shafts, standardfooting dimensions, and elastomeric

bearings for all span-by-span construction.Standardization resulted in tremendoussavings.

Economic issues permeate the designprocess, Kangari notes, taking in not onlyefficiency of component design but alsospeed of construction to lessen user costsand durability issues to extend the bridgesservice life. Our designs today musthelp clients in more than one way, hesays. They must solve greater and morelong-term transportation problems, such

as traffic issues during construction and

maintenance needs.

Lessening traffic disruptions duringconstruction has become a key concern, henotes. Officials are more aware of the costsassociated with those disruptions and theneed to reduce them, says Kangari. Thathas led to the expansion of AcceleratedBridge Construction (ABC) concepts,adds Kozhikote. These techniques includebuilding the bridge at a nearby locationand then moving it into place, requiringonly a brief road closure. Girder launchersand modular designs offer more options.The less mobilization you need at the site,the more reduction in cost, time, safetyneeds and disruption to users. The public isdemanding faster construction.

Longer Service Life NeededMaintenance needs have become a keyissue as demands are being placed tocreate 100-year service lives and find waysto reduce the long-term costs required tomaintain bridges. A 100-year service lifeis becoming more popular because clients

Keys to ConstructabilityInnovations with conventional designstypically focus on issues of constructability,economics, and maintenance, Kangarinotes. Those are the key topics that arisewith every project.

Constructability issues play to concretesstrengths, the designers note. Not only dothe designers work with local contractorsand precasters to ensure each companysstrengths are maximized, but they takefull advantage of concretes capabilities forreplicating components cost-effectively.We focus on finding ways to increaserepetition in our designs to save cost,McGrew explains. Carefully selectingstandard sections early in the design cansave a great deal of fabrication time andcost for the precaster and forming expensefor the contractor.

The efficiencies of that approach wereshown with the design for the I-4/LeeRoy Selmon Connector Interchange inHillsborough County, Fla. The multi-level$450-million complex project, one of thelargest ever in the area, features bothsteel and segmental-concrete options. Thesegmental option consists of both span-by-span and balanced cantilever constructionmethods. The segmental boxes benefitfrom the creative use of external post-tensioning, which allows a reduction in

the principal stresses, shear reinforcement,

We focus on finding ways to increase

repetition in our designs to save cost.

ASPIRE S i 2009 |


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The U.S. 17A/SC 41 Bridge

over the Santee River in

Georgetown, S.C., sits

downstream of Wilson Dam

and the St. Stephens Power

House, making it subject

to frequent flooding. The

1.5-mile-long precast concrete

bridge was designed for

construction in either wet

or dry conditions and meets

seismic performance B

category requirements.

Photo: PBS&J.

are very concerned about their structureslife spans, and they know such durabilityis available, says McGrew. Concretehas an incredible advantage in that area.New admixtures are improving quality anddurability, adds Kozhikote, especially forbridges in aggressive environments such ascoastal areas.

Myers serves as project coordinatorfor the R19A project of the StrategicHighway Research Program conducted bythe National Academy of Sciences. Theproject is examining bridge componentsand systems to find ways to make themlast more than 100 years. Concretework focuses on overcoming corrosionconcerns. Were very early in evaluatingoptions and concepts, but we absolutelyare at the forefront of finding ways toextend durability. It appears that fundingwill be available to get projects going, butmaintenance funds are still constrained.

In addition, PBS&J is developing newdesign criteria to identify the minimumreinforcement required in concretebridge members (NCHRP Project No.12-80). PBS&Js Dr. Jay Holombo, Dr. SamMegally, and Morad Ghali are workingwith Dr. Maher Tadros of the Universityof Nebraska. Their research could improveconstructability and reduce the costs ofconcrete bridge members.

Indeed, the new administrations stimuluspackage will provide the impetus formore projects to begin in both design andconstruction. We expect we will be seeingmore projects being funded in the nearfuture, says McGrew. And we expectto be involved in finalizing many of theexisting designs that are ready but just needapproval, with more going into the pipelineThe designs will be across the spectrum,

including quite a few large projects.

The need for efficiency will increase theinterest in alternative delivery systemsnotes Myers. Design-build options aregrowing, not only because they providespeed of construction but also becausethey improve efficiency, which savesmoney. The design-build approach allowsus to work with contractors in ways thatare most effective for them based on theircapabilities. Doing that provides a betterapproach and a better price than a typica

design can provide. The state DOTs areopen to this system, and it plays to ourown strengths.

Funding also will be supplemented byexternal sources, predicts Kangari. Thereis growing interest in public/privatepartnerships, with private money beinginvested in infrastructure to aid locadevelopments, he says. That can bringmore challenges, as it creates more needsand different agendas, and it also puts thefocus on durability. If private companies

are providing the long-term maintenancethey are very interested in not only gooddesigns but also low maintenance costs.

PBS&Js designers welcome thosechallenges as they work to wring moreefficiency from every structure they create.Our clients appreciate practical solutionsthat meet all of their needs, says MyersBut when something different or uniqueis warranted, we find the solution.

From Four to 4000PBS&J got its start in late 1959, when Howard M. Budd Post, a young resident engineer with theFlorida State Road Department, met Bill Graham while visiting a contractors office. The prominentSouth Florida dairyman offered Post an engineering position with his fledgling land-developmentcompany, Sengra, which was considering converting pastureland into what is now known asMiami Lakes, the first planned new town in Florida.

Post recommended hiring an engineering company instead, suggesting the firm that employedtwo of his best friends, George G. Mooney and Robert P. Schuh, as well as John D. Buckley, one of

the top sanitary engineers in the state. When Graham expressed a disinterest in hiring a large firm,Post offhandedly offered to form a company to do the work. To his surprise, the offer was accepted.

The four men quickly established a corporation, with Schuh being the first to put up his money.As a result, Robert P. Schuh & Associates was born on February 29, 1960. In 1970, the firm wasrenamed Post, Buckley, Schuh & Jernigan Inc. (PBS&J). The firm grew steadily and then took offduring in the 1990s when it acquired a series of related companies in architecture, engineering,and environmental fields.

Today, the employee-owned firm has a staff of more than 4,000 in 80 offices across the UnitedStates and abroad, offering services in transportation, infrastructure planning, constructionmanagement, environmental consulting, urban planning, architecture, and program management.The firm is ranked by Engineering News-Recordas the 25th largest consulting firm.

We absolutely are

at the forefront of finding

ways to extend durability.

For more information on this or other

projects, visit www.aspirebridge.org.



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By using ground-based crane erection of precast segments,

construction does not require the use of large gantries on site.

Photos: Finley Engineering Group Inc.

PERSPECTIVE

Several years ago, even before sustainable developmentwas the important topic it is today, the American SegmentalBridge Institute (ASBI) acknowledged the following phrase asan organization goalget in, get out, stay out.

Cliff Freyermuth, who was then ASBI director, wrote in 2003that this concise statement summed up ASBIs mission of reducing project construction time and reducing the need forproject maintenance activities following construction.

What does that have to do with sustainability? Plenty,

if you consider sustainability more than an issue forenvironmentalists and ecologists. Sustainable Measures,a consulting firm dedicated to promoting sustainablecommunities, says sustainability can be measured by whetherthe economic, social, and environmental systems that makeup the community are providing a healthy, productive,meaningful life for all community residents, present andfuture.

Thats a lot bigger than using energy-saving bulbs in thelighting plan.

At its core, sustainable development offers all kinds ofshort- and long-term benefits to a communitywhetherits the residential community, the driving public, or theenvironment.

With recent advances made in post-tensioned segmentalconcrete bridge construction, were making significantstrides toward achieving higher levels of sustainability in ourprojects as an industry. Specifically, new grouting materialspecifications and new approaches to grouting tendons,improvements in epoxy technology, innovation in post-tensioning systems, and new developments in concrete mixdesigns resulting in better, higher-strength concretes areimproving our ability to get in, get out, and stay out.

SUSTAINABILITY

Get In, Get Out,and Stay Out

by Craig Finley,

Finley EngineeringGroup Inc.


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ASPIRE S i 2009 |

National grouting standards

and a certification program

have contributed to improved

performance. Photo: American

Segmental Bridge Institute.

Grout and EpoxyImprovementsThe Florida Department of Transportation(FDOT), in its Post-Tensioning Tendon

Installation and Grouting Manual,states: Good corrosion protectionof post-tensioning is essential for

structural integrity and long-term durability. Over the years,occasional failures have been

detected that were attributed toinadequate grouting and lack of

overall protection.

Grout originally had two roles in post-tensioned bridge projectsto bond thetendon to the surrounding concrete

via corrugated ducts and to fill theduct and prevent corrosion causedby contaminants. However, problemsarose related to grouting. With noset standards for uniformity, groutingsystems tended to bleed water, incurinstallation voids, and leak at ducts anddeviation pipes. Other issues includedlack of cap protection, chemical issuesfor set and hardening, and ductcracking.

In recent years, the developmentof national grouting standards andspecifications, a grouting certificationp rog ram, and more i n tens i vetraining have dramatically improvedperformance. Now, with virtuallyno grout issues, bridges require lessinspection and maintenance, and theylast longer.

Early epoxy was also sometimesproblematic, failing to properly cure, notproviding the necessary waterproofing tothe deck; and variations in thickness of the

epoxy affected the segment geometry. Asan industry, we learned that a one-size-fits-all approach to epoxy technology wouldnot work, so we developed a variety of

different formulations to address projectvariables such as extreme temperaturesand set times.

Unlike the grouting improvements,which were driven by ASBI and thePrecast/Prestressed Concrete Institute(PCI) in cooperation with the states, theevolution of epoxy mixes was driven bymanufacturers competing to improvea product that as originally introduced,was inadequate.

In both cases, but in different ways,the industrys innovations reinforce thenotion that good construction practice,and the sustainability that accompaniesit, are evolutionary.

Improvements in post-tensioningtechniques are also reaping performanceand durability rewards on major bridgeprojects. These include low-relaxationstrand, improved analysis techniques anddesign software, the use of unbondedtendons in extruded sheathing,encapsulated anchors, diabolos, and

development of prepackaged, non-bleedgrouts for bonded post-tensioning.

An effort is currently underway toestablish a national standard for post-tensioning; just as such standards wereachieved for grouts and grouting.Proponents of this standard (includingthe writer) are reviewing and adaptingstate codes into a single nationalstandard for post-tensioning, with a goalof 12 to 18 months for implementation.


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Aerial view of the Ein Hakore Interchange of Road 431. Precast concrete segmental

bridges offer insights into how durability and sustainable construction intertwine.

Photo: Danya-Cebus.

Longitudinal view of Bridge 22 on

Road 431 in Israel, built in precast

segmental cantilever construction.

Photo: Finley Engineering Group Inc.

Deviation segment featuring post-

tensioning tendon diabolos in the

foreground. Photo: Finley Engineering

Group Inc.

Road 431 in IsraelThe introduction of external post-tensioning tendons has also helpedchange the nature of the corrosionprotection system, as illustrated by theRoad 431 project in Israel.

Time was the most compelling reasonto use precast segmental constructionwith external tendons on the Road431 Ein Hakore Interchange Bridges inIsrael. With a very limited design andconstruction schedule, and several otheraspects of the overall roadway projectdependent on prompt completion of theinterchanges, the project team neededto perform quickly.

The external post-tensioning systemreduced the segment cross-sectional

area, including narrower web width

and bottom slab thickness. This resultedin lower superstructure weight andfoundation loads, and better utilizationand effectiveness of the post-tensioningsystem. With smaller sections, the samepost-tensioning force achieved highercompressive stress in the concrete andreduced cracking potential, meaninglower cost and better performance.

Also, external tendons meant that fewersegments required post-tensioningembedments and associated details, so

segment casting was faster and moreefficient. The system reduced post-tensioning operations in the field asthere were fewer tendons to install,less anchorage hardware, and fewerstressing operations. The continuousduct also reduced the number ofconnections.

When considered collectively, thesefactors positioned the Road 431 projectas a model of sustainability.

Because Road 431 is a build-operate-transfer project, contractor/concessionaireDanya-Cebus was particularly sensitiveto durability issues and conscious ofinspection and maintenance of theinfrastructure. Since it is a toll road, anyshutdown for inspection or maintenancewould reduce income. So staying outwas equally as important as getting inand getting out.

Because external tendons are notencased in concrete, maintenance

teams can ensure that all strands remain

protected against harmful exposuresby simple visual inspection of thetendon ducts. External tendons can beinspected for nearly their entire lengthand repair teams can repair any defectfrom inside the box girder. Such defectswould include grout voids, split ductsand tendon damage.

ConclusionBy focusing on getting in, gettingout, and staying out, a bridge designand construction team can contributegreatly to sustainability goals. Lessconstruction time usually means fewertraffic problems and, as a result, reducedsmog, faster commute times, and anoverall improvement in qualify of life. Amore durable bridge means less downtime for inspection and maintenance,a higher level of safety, and a longer-lasting structure.

In the United States, with billions ofdollars from the stimulus bill likely tobe spent on bridge construction and

reconstruction, and an industry wiselyfocused on increasing sustainability inall areas, we should continue our questfor innovation and improvement in ourconstruction processes and techniques.This way, our countrys investment inbridge infrastructure will be rewardedwith highly efficient, rapidly built, andlow-maintenance structures that do theirjob and do it for a long, long time.




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ASPIRE S i 2009 |

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The Pennsylvania Turnpike Commissionsnew Allegheny River Bridge, nearPittsburgh, is Pennsylvanias first cast-in-place balanced cantilever bridge.The bridge construction began shortlyafter the U.S. Open Championship atOakmont Country Clubs golf course inthe summer of 2007, and the bridgeconstruction will be completed in early2010, ahead of the U.S. WomensOpen Championship at Oakmont. ThePennsylvania Turnpike bisects OakmontCountry Club within the limits of theAllegheny River Bridge project.

The existing Turnpike Bridge overthe Allegheny River was opened inDecember 1951 and carried twolanes of I-76 traffic in each direction.Options to both replace and repair theaging structure were evaluated priorto design of the new bridge. Thenarrow width of the existing bridge,projected traffic demands, and theTurnpike Commissions long-term goalof widening to three lanes in eachdirection led to the decision to replacethe existing bridge.

profile I-76 ALLEGHENY RIVER BRIDGE / NEAR PITTSBURGH, PENNSYLVANIAENGINEER:Figg Bridge Engineers Inc., Tallahassee, Fla.

CONTRACTOR AND POST-TENSIONING CONTRACTOR:Walsh Construction Company, Chicago, Ill.

CONCRETE SUPPLIER:Stone and Company, Tarentum, Pa.

FORM TRAVELERS FOR CAST-IN-PLACE SEGMENTS:NRS-ASIA, Norway

New Pennsylvania

Turnpike Bridge

balances aesthetics,

economy, and

environmentalsensitivity

The new bridge carries I-76 over theAllegheny River and consists of twin2350-ft-long parallel structures foreastbound and westbound traffic withan 8-ft-wide gap between bridges tofacilitate future access. The alignmentof the new bridge is downstream androughly parallel to the existing bridge,allowing two lanes of traffic in eachdirection to be maintained duringconstruction and minimizing traffic

impacts to Pennsylvania Turnpikecustomers. The contract was awardedfor the project in May 2007 with alow bid of $189 million. In additionto the main river bridge, the overallAllegheny River Bridge ReplacementProject also includes three overpassbridge replacements, reconstruction ofthe Allegheny Valley Interchange rampsand interchange bridge, construction ofthree major walls, approximately 2 milesof approach roadway reconstruction,and demolition of the existing bridge.

The New BridgeVariable depth concrete segmental boxgirders which are 26 ft deep at the

by Brian Ranck, PennsylvaniaTurnpike Commission andKen Heil, FIGG

ALLEGHENY

RIVER

BRIDGESustainableDesign andConstruction

A rendering showing the finished bridge and its main span

Rendering: FIGG.


PROJECT


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CAST-IN-PLACE, POST-TENSIONED BOX GIRDER / PENNSYLVANIA TURNPIKE COMMISSION, OWNERPOST-TENSIONING MATERIALS:Schwager Davis Inc., San Jose, Calif.

PREPACKAGED GROUT:Sika, Lyndhurst, N.J.

BRIDGE DESCRIPTION:Twin, 2350-ft-long, segmental box girder bridges built using cast-in-place balanced cantilevers with a 532-ft-long main span

over the Allegheny River

BRIDGE CONSTRUCTION COST:$189 million (total project)

main span piers, 19 ft deep at the sidespan piers, and 11 ft deep at midspan

cross the Allegheny River Valley. Usingtraveling forms, the bridge is being castin place using the balanced cantilevermethod, working from the tops of thepiers. Incrementally working out fromthe piers, five cantilevers result in sixspans of 285, 380, 380, 444, 532, and329 ft. The two end spans include 105-ft- and 69-ft-long portions beyond thebalanced cantilever that are cast in placeon falsework.

The cross section of the segmental box

girder was designed as a single-cellbox girder with a constant core formwithout ribs or transverse drop beams inorder to simplify formwork and castingoperations. Variable wing lengthsaccommodate deck widths from 61 ft(typical) to 84 ft at the westbound endspan adjacent to the interchange.

Each segment is cast with 2 in. ofadditional monolithic top slab concrete

thickness to form an integral wearingsurface. The top flange of the boxand the integral wearing surface werepost-tensioned in both the longitudinaland transverse directions to providecompression in the deck for long-termdurability of the final riding surface.Milling in. at the end of constructionensures the best final riding surface. Thedesign allows for complete removal of theintegral wearing surface and replacementwith an overlay in the future.

ConstructionBalanced cantilever construction beganfrom pier tables cast in place atoptwin-wall piers to provide a platformfor launching the traveling forms. Oneside of the pier table was 16 ft longwhile the other side was 24 ft long; theasymmetry kept the cantilever balanced

The balanced cantilever

construction method allowedtraffic flow through the

Allegheny River Valley on the

roads below while construction

took place 54 ft overhead.

A 4-ft closure is all that

remains to complete a

380 ft span at a height

of 100 ft over the

Allegheny River.

All photos: FIGG.

The Pennsylvania Turnpike Commissions new Allegheny River Bridge will

result in a sustainable bridge that will serve the Pittsburgh area for many years.

ASPIRE S i 2009 |


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Environmental Challenge

A ContextSensitive SolutionFIGG designed the new Allegheny River Bridge to be asustainable, environment-friendly structure that wouldfit in harmony with the landscape around the AlleghenyRiver and Fourteen Mile Island (part of AlleghenyIsland State Park) while preserving the river and otherhistorically significant areas nearby. Span arrangementswere planned to accommodate a busy multi-modaltransportation network that runs through the AlleghenyRiver Valley. The new bridge crosses a local road, Norfolk

Southern Railroad, the two channels of the AlleghenyRiver, Fourteen Mile Island, and Allegheny Valley Railroad.Balanced cantilever construction allows for continual flowof highway, rail, and barge traffic throughout the duration

of construction. The 532-ft-long main span preserves the existing horizontal clearanceneeded for the navigation channel of the Allegheny River, which supports commercialbarge traffic. The new river piers are close to the river banks and island to entirely avoidthe archaeologically sensitive zone on Fourteen Mile Island, while being sensitive to theaquatic habitat. The Allegheny Rivers history of fluctuating water levels also contributed tothe decision for locating piers adjacent to the river banks.

The concrete pier shape was selected by the Pennsylvania Turnpike Commission (PTC) Teamduring the design process using a FIGG Bridge Design Charette. The PTC was presented

with several pier shape options and selected a curved pier that complements the gracefulsweep of the variable depth superstructure. FIGG considered constructability, repetition,and reuse of formwork at all piers during design to maintain an economical pier shape.To simplify construction, a parabolic curve was approximated by combining two circularradii. A variable height rectangular base compensates for the different heights at eachpier. Concrete formliners and earth-toned stain are used to create a stone texture on thepier faces. The stone texture was selected by the PTC to complement existing stonework atOakmont Country Club and the surrounding landscape.

The Pennsylvania Turnpike Commissions new Allegheny River Bridge will result in asustainable bridge that will serve the Pittsburgh area for many years. Built from the topdown to keep traffic flowing, the long, sweeping spans deliver an aesthetically pleasingdesign that also functions to protect the sensitive river environment.

option. The contractor chose pipe piles

for Pier 1 and drilled shafts for Piers 2through 5.

As of January 2009, foundationconstruction is complete, and the twin-wall pier construction is nearly complete,with only Piers 2WB and 5WB remaining.Completion of the eastbound bridge isscheduled for November 2009 toaccommodate a key shift of eastboundtraffic off of the existing bridge and



roadway. Completion of the westbound

bridge is scheduled for early 2010.____________

Brian Ranck is bridge/tunnel maintenancecoordinator, Pennsylvania TurnpikeCommission, Harrisburg, Pa., and Ken Heilis senior bridge engineer, FIGG, Exton, Pa.

to within a half segment to minimize

out-of-balance loads on the piers whileutilizing constant 16-ft segment lengthsfor ease of construction.

Year-round cantilever constructionutilizes four traveling forms for thesuperstructure to meet the projectschedule. Daily low winter temperaturesin nearby Pittsburgh are 20 F on average,making a cold weather concretingplan vital for maintaining production.Construction began at Pier 1 whereaccess was the most straightforward,

with the eastbound (EB) bridge beingbuilt first to allow for traffic phasing.Cantilevers 1EB and 2EB were cast intandem, and then the four travelingforms were alternately advanced to castthe remaining cantilevers. Four-ft-longclosure segments connect each of thecantilevers at the center of the span. Thesuperstructure is supported with internalhigh-strength steel post-tensioningtendons containing nineteen 0.6-in.-diameter strands, and external post-tensioning tendons containing twenty-seven 0.6-in.-diameter strands.

Piers and FoundationsTwin wall piers were selected for anoptimum design that eliminated theneed for temporary towers duringconstruction. Strength and slendernessof the twin walls are balanced with theirheight to provide the required flexibilityfor creep and temperature effects. Thepiers are 100 ft tall for river Piers 2through 5 and 60 ft tall at Pier 1. Allpiers in the river were designed for bargeimpact loading (3000 kip maximum), iceloading, and scour provisions.

Studies during the design phase of thenew Allegheny River Bridge projectindicated that several foundation optionsprovided viable solutions. To stimulate acompetitive bidding arena and maximizeeconomy in the foundations while takingadvantage of contractors expertise,fully detailed foundation bid optionswere included in the bid documents forboth pipe piles and drilled shafts at allpiers. Pier 5, which has relatively shallow

bedrock, also had a spread footing

Photo:F

IGG.

The concrete pier shape was selected by the Pennsylvania Turnpike

Commission Team.



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ASPIRE S i 2009 |

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profile FORTY FOOT PEDESTRIAN BRIDGE / TOWAMENCIN TOWNSHIP, MONTGOMERYCOUNTY, PENNSYLVANIAFUNDING / CONSTRUCTION PARTNER:Pennsylvania Department of Transportation District 6

STRUCTURAL ENGINEER:QBS International Inc., Pennsauken, N.J.

BRIDGE DESIGNER:Simone Coll ins Inc. Landscape Architecture, Berwyn, Pa.

CIVIL ENGINEER:McMahon Associates Inc, Fort Washington, Pa.

GEOTECHNICAL ENGINEER:GeoStructures Inc., King of Prussia, Pa.

PRIME CONTRACTOR:RoadCon Inc., West Chester, Pa.

AWARDS:Award of Excellence, 2008 Portland Concrete Association (PCA); Project of the Year, 2007

American Society of Highway Engineers (ASHE) Delaware Valley Chapter (projects over $5 million)

Integrating Art and

Engineering in Public

Infrastructure

by William Collins, Simone Collins Inc.

Forty Foot Pedestrian Bridge

It took Towamencin Township over twelveyears of planning, design, and constructionto depress the alignment of State Route63 and construct the new Forty FootPedestrian Bridge as the context-sensitive

signature of an 8100-ft-long highwayimprovement project. The new 40-ft-wideby 80-ft-long concrete bridge spansthe highway known as Forty Foot Roadin Montgomery County, Pa. The bridgecreates a safe and accessible pedestrianlink over the five lanes of traffic that bisectthe new Towamencin Town Center.1

The Pennsylvania Department ofTransportation (PennDOT) served as theconstruction and funding partner for thetransportation improvements that were

planned and engineered by the townshipto integrate smart land-use strategies thatincluded parks, trails, streetscape amenitiesstructured parking, and incentives forprivate mixed-use development.

Towmencin Township designed and builta municipal road around the project areaas a bypass to maintain state highwayand turnpike-bound traffic. This earlyinvestment in infrastructure allowedForty Foot Road to be closed for roadwayexcavation and bridge construction withreduced traffic maintenance costs, andcreated a valuable new asset for motoristsand local developers. The bridge wasbuilt as a turnkey element for Townshipownership after completion in 2007.

The Forty Foot Bridge under

night traffic reveals many

of its aesthetic features.

All photos: Simone Collins

Landscape Architecture.



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Infrastructure asCommunity FabricFrom the start, Towamencin Townshipenvisioned the highway project tobe an essential part of the revitalizedcommunity landscapein terms ofwalkability and physical character. Whena central pedestrian bridge was selectedas the preferred alternative for crossing

the highway, the prominent locationdemanded functions and aesthetics abovethe ordinary.

Concrete was selected for its economy,durability, and plastic qualities that coulddeliver a seamless aesthetic in a singlestructural and artistic material. Thesculptural potential of concrete inspireda collaborative process between thebridge designer and structural engineerto incorporate art considerations withinthe engineering decisions. The result is

a practical synthesis of conventionalmaterials and techniques with strategicallyselected, custom concrete treatments foraesthetics in highpriority elements.

Geometry as an AestheticProgram ElementThe Forty Foot Bridge design consciouslyfeatures and mitigates specific geometricproportions. The clear span from centerto center of bearings is 78 ft 6 in. Fasciabeams are engineered as structural

members up to 12 ft deep and 90 ft long,with integrally-formed architecture. Beamdepths were selected to create parapets tocloister the pedestrian environment fromthe traffic below. The bridges width is 40 ftwith curving, cast-in-place planters on bothsides of the concrete deck to modulatespace within the inside faces of theparapets by defining a sweeping, variable-

width promenade. Pedestrian lightingwas designed for safety and ambiance.The cartway is wide enough to serve as acivic space for periodic functions withinthe town center. The cambered deck servespedestrian and bicycle traffic only, but isengineered to support an H-20 truck loadfor maintenance and emergency vehicles.

Engineering Innovation Fascia Beams and HaunchedBox BeamsThe fascia beams are uninterrupted,full-span, full-height beams that extendabove the deck elevation to create theappearance of a rigid frame. They are,however, simple span reinforced concretebeams designed to sit on cast-in-placeconcrete abutments with standard

PRECAST, PRESTRESSED CONCRETE BOX BEAMS AND CAST-IN-PLACE FASCIA BEAMS WITH INTEGRALARCHITECTURE / TOWAMENCIN TOWNSHIP, OWNERCONCRETE SUPPLIER:Berks Products, Allentown, Pa.

WHITE CEMENT SUPPLIER:Lehigh White Cement, Allentown, Pa.

PRECASTER FOR BOX BEAMS:Schuylkill Products Inc., Cressona, Pa., a PCI-certified producer

PRECASTER FOR MSE WALL AND CAP FINIALS:The Reinforced Earth Company, Vienna, Va.

PRECASTER FOR FINIALS AND PYLON CAPS:Architectural Precast Inc., Burlington, Ky.

BRIDGE DESCRIPTION:An 80-ft-clear span by 40-ft-wide pedestrian bridge, exposed aggregate structural deck on conventional spread box beams,

and ornamental fascia beams

BRIDGE CONSTRUCTION COST:$1 million for the bridge as part of a $13 million highway reconstruction project

FAR LEFT: View of pedestrian

environment toward south portal

showing the concrete deck with

cast-in-place planters.

MIDDLE: Exposed aggregate structural

deck. Planter wall forms were designed

to echo the parapet line and the

wingwall rustications.

RIGHT: Structural pylons are clad with

architectural wingwall panels, mirrored

inside and out. Globe lights were

mounted on custom formed pylon caps.

The sculptural potential of concrete inspired a

collaborative process between the bridge designer

and structural engineer

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A view of portal with box

beams, corrugated deck pans,

and fascia beam in place.

Note the haunch on the fascia

beam to support the cast-in-

place structural deck.

laminated neoprene bearing pads. Fasciabeams were engineered to act as standardload-bearing concrete stringers. Theyserve as hybrid members with modifiedgeometry that allows the beams to include

the safety functions of concrete parapets,the sound-dampening functions of soundwalls, and the expansive surfaces for artformsall within the new concrete beamdesign. The L-shaped fascia beams vary indepth from 12 ft at midspan to 8 ft 8 in.over the supports and have a thicknessthat varies from 18 in. to 20 in.

Within each fascia, 15 epoxy-coatedNo. 7 bars provide the primary flexuralreinforcement, and epoxy-coated No. 4stirrups act as shear reinforcement. The

ends of the beams cantilever behind theabutments toward structural pylons whereboth are clad with precast architecturalwingwall panels. The structural concretedeck bears on interior haunches of thefascia beams. This design allows deckedges to be hidden behind the fasciabeams, so that the structural deck is onlyexposed as the wearing surface withaesthetic treatments. Concrete buttresseshidden within the cast-in-place planters tiethe fascia beams structurally to the deck.

The concrete deck is also supported bythree interior 48-in.-wide by 39-in.-deepprecast, prestressed concrete box beams.The beams were haunched 13 in. to simplifythe forming and casting of the cambereddeck. The beams varied in depth from 39in. at the supports to 52 in. at midspan.The interior void form varied in depth aswell, maintaining a constant 3-in.-thick topflange and 5-in.-thick bottom flange.

Art and ArchitectureThe architecture of Forty Foot Bridge

acknowledges typical structural features

such as corbels, spring points, camber,hinges, and keystones. Art lines in theconcrete are graphic interpretations offorces alive within the bridge, includingtension, compression, bearing, and

repose.

The Art Deco motif responds to the boldengineering by exploiting the concretematerial to form elegant, archetypal archshapes as shadowed relief, designedto lighten the apparent mass of thedeceptively large fascia beams. Belowthe arches, the art of the ripple art formschange frequency to express the fluidnature of movements below a bridge, andfunctionally create horizontal shadow linesdesigned to subtly elongate the bridge

visually and de-emphasize the sense ofits vertical dimension.

CAD-generated documents for computer-cut, styrene formliners were used to createmolds up to 4 in. deep for the surfacetopography within the fascia beams. Thecurved top of the fascia beams was anaesthetic decision accommodated by theengineering to soften the shape, reducevisual mass, and create the top line ofthe perceived arch in the fascia beam.

Color for concrete surfaces was specifiedconservatively to allow for multiple fieldmock-ups and photo-rendering studies ofthe actual structure during constructionColor selections were simplified to twocolors and bright white. A light greenwas used below the arch shape to makethe rippled surface visually recede,creating the effect from a distance thatit blends with the sky and landscapebeyond, making the slender white archshape over the road appear to leap tothe foreground. All finished concretesurfaces were treated with a transparent

gloss urethane sealant.

The East fascia beam

showing the rippled

form, abutments,

paver-faced sloped

walls, MSE walls with

precast cap finials,

precast wingwalls,

and pylon cap.

More and more

modern infrastructure

will be needed to relate

to increasing numbers

of people outside of

vehicles and moving at

the speed of foot traffic.



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Foundations, Retaining Walls,and Sloped Paver WallsThe substructures are conventional concreteabutments using standard formliners tomatch the rustications of the adjacentprecast mechanically stabilized earth(MSE) retaining walls. Custom-cast finials

terminate the lines of standard MSE wallcaps at the abutments. Four 85-ft-long MSEretaining walls create the grade separationalong the depressed Forty Foot Road.

The sloped paver walls above the MSEretaining walls were designed at a 1:1gradient to be visible from all directions, andare essential to the success of the designproviding a sense of openness, light, andvisual access between the roadway andpedestrian environments. The 45 degreewalls also serve to limit the height of the

retaining walls to 8 ft, prevent a tunneleffect under the bridge, and expose thewingwalls as visible pylon elementsalleffectively elongating the visual sense ofthe bridge.

The arches formed in the fascia beamsappear to spring from the sloped bearingline formed in the pylon panels. Structurally,the sloped walls act as compressivestructures to bear against the MSE wallsand are tied into grade using the sameconventional geogrid reinforcement as thevertical walls. Concrete unit brick paverswere laid on a mortar bed in a fan patternwith dark mortar to reduce contrast.

Required roadway clearance below thebridge was achieved by partially depressingthe highway and partially elevating thebridge to create subtle 3% approachgradients that allow complete visibilityunder the bridge to the surrounding towncenter landscape.

ConclusionThe highway project, including the FortyFoot Bridge, was let by PennDOT underthe state contracting process, and thelowest prequalified bidder was selected.The product demonstrates that capablefine craftsmanship is available within theindustry to deliver a project with exacting,custom aesthetic specifications.

The success of the fascia beam conceptrelied completely on engineering innovationto create an extraordinary venue forthe proposed artwork, to achieve a rarecollaboration where art considerations

affect geometry, engineering, and construc-

tion methods. The jury for the 2008 PCAConcrete Bridge Awards said Forty FootBridge, is in itself a work of art. Thevisual harmony and scale of Forty FootBridge succeeds in creating an inviting civicplace and a landmark for both motoristsand pedestrians. The structure featuresmodern engineering design infused witha restrained aesthetic that salutes theinspiration of the historic Merritt Parkwaybridges built in the 1930s.

With a pending economic stimulus packageand promised rush of infrastructure projectsin 2009, we understand that what we buildtoday lives with us for the next half centuryor more. Enduring infrastructure andquality jobs require smart choices to ensurethat our special places are protected andimproved by new projects that incorporatethe combined talents of engineers, artists,

and craftspersons. More and more moderninfrastructure will be needed to relate toincreasing numbers of people outside ofvehicles and moving at the speed of foottraffic. Forty Foot Bridge is an example of a21st Century project that borrows the bestfrom two previous eras of infrastructure

by incorporating humanizing art featuresthat gave public works projects of the 1930sdepression-era their unique personalities,with typical standardized, mass-producedefficiencies ushered in with the products ofthe Interstate Highway System of the 1950s.

Reference1.Collins, William, John Ruff, KristenYork, and Bashar S. Qubain, 2008,Forty Foot Road Pedestrian Bridge:Integrating Aesthetics and Engineering,Proceedings of the PCI-FHWA NationalBridge Conference, October 5-7,Orlando, Fla., 22 pp.

____________

William Collins is vice president, SimoneCollins Inc. Landscape Architecture,Berwyn, Pa.



ASPIRE S i 2009 |
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Six prestressed, post-tensioned

trapezoidal U-girders, 60 in. deep,

were used for the superstructure.

215-FT-LONG BRIDGE WITH PRECAST CONCRETE TRAPEZOIDAL U-GIRDERS / COLORADO DEPARTMENT OFTRANSPORTATION, OWNERBRIDGE DESCRIPTION:Four cast-in-place pier columns, six, 60-in.-deep trapezoidal U-girders, and 27 precast, prestressed concrete, variable-

thickness full-width deck panels

BRIDGE CONSTRUCTION COST:$1.354 million ($170.18/ft2)

on the girders and a flared-web detailat the post-tensioning anchor plates.But otherwise, they determined thatthe bridge design, having undergoneintensive design reviews previously,was as cost effective as possible. Thesechanges lowered the precast concrete

girder costs, but they did not provide thesignificant overall project-cost reductionsrequired. Subsequently, the team foundsignificant savings in other areas of theproject, including modifying roadwaygeometry and eliminating retainingwalls. These changes allowed the projectto meet the budget and move forward.

Prior to beginning construction, designengineers created a virtual 3-D model,while the contractor built a full-scalemock-up of the pier leg-to-girderconnections. These are both unusualsteps for a modest project. Becausethis project was far from typical, the

models provided a better understandingof how the components worked for thissignature bridge.

The 215-ft-long bridge features asuperstructure composed of all precastconcrete components. Six prestressed,post-tensioned trapezoidal U-girders,60 in. deep, along with 27 prestressed,variable-thickness deck panels were usedon the project.

Variable-Depth FlangesCreatedCreating the bridge as a precastconcrete structure posed a significantchallenge, in that the original designfeatured a parabol ic girder with

variable-depth bottom flanges to resistthe high negative moments over thepiers. To accomplish this economically,the precaster took the projects variable-depth bottom flanges and substitutedconstant-depth precast flanges with theadditional thickness provided by cast-in-place concrete hidden inside the girder.

The precaster was allowed to createthe constant-depth design as long ashorizontal shear reinforcement wasprovided at the plane between the

precast and cast-in-place concrete.However, rather than have shearreinforcement project above the top ofthe bottom flange, which would havebeen very difficult due to the steel format that location, the precaster providedtransverse grooves that were form-castin the interior of the tub. The groovesprovided an alternative shear-frictionplane. By keeping the bottom flange ata constant depth in the casting yard,fabrication costs and shipping weightswere reduced. This was a significantfactor, as the girders, with a weight ofabout 104 tons apiece, were near thehandling limits for typical cranes.

The Richmond Hill Bridge

in Conifer, Colo., features a

striking design that is enhanced

by the use of precast concrete

components, including

trapezoidal U-girders and full-

depth deck panels. The V-legs at

each end reduce the span length

without encroaching on theroadway.

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In addition, numerous inserts werespecified in the webs and top flangesof the U-girders to facilitate the hidden

pier cap, the hidden thickened bottomflange, and the end diaphragms atthe abutments. Weldable A-706 steelreinforcement was allowed in the girderso that inserts could be positioned incongested areas where there was littleor no room for wire ties.

Upon arrival at the site, an additionalmat of steel reinforcement was placed ata slope inside the U-girder. Field-placedconcrete produced variable-depthbottom flanges that were completelyhidden inside the box.

V-Legs Reflect GirdersThe V-legs that provide a strikingsilhouette for the project take theirshape and dimensions from the precastconcrete U-girders. The width at thetop of each pier leg was sized to slightlyexceed that of the bottom girder flange.Moreover, the webs in standard precastColorado U-girders are sloped at a ratioof 4:1 and this slope was allowed toflow into the pier legs, defining theV-shape. As a result, the legs echothe exterior precast concrete girderfaces. Sun falling on the piers and onthe girders reflects at the same angle,casting shadows of equal intensities onthe pier and girders, visually smoothingthe transition between these connectingelements.

The aesthetic design produced by thetwo precast girder lines was superior tothat of a single, flat bottom flange thatwould have been provided in a cast-in-place superstructure. Because the

interior cells would have been hidden



behind a single flat bottom flange, thecast-in-place approach would haveproduced a visually undesirable tunnel

effect. The transition between eachof the two supports at the top of theslant-Vs into two precast concrete girderlines provided a more visually unifiedappearance than if it consisted of asingle bottom flange.

Precast Deck Panels SelectedFull-width precast concrete deck panelswere chosen, with a cast-in-placealternative offered as well. The girderswere fitted with steel plates embedded inthe top flanges. The required numbers of

studs were field-welded onto the platesat locations lining up with blockouts inthe precast concrete deck panels. Foamboard was carefully sized and glued inplace along the top flange to contain theconcrete used to fill the blockouts andspaces between the tops of the beamsand the bottoms of the panels.

The concrete deck panels weredelivered from the casting yard, liftedonto the girders, and fitted up. Theywere adjusted for height with levelingscrews and clamps. A concrete mixthat was virtually self-consolidatingwith a spread of approximately 22 in.,was used to fill the spaces. This mixexceeded all strength requirementsand did not require internal vibration.Using this flowable mix ensured thatany congested spaces between the deckpanels or within the hidden pier capwere completely filled.

The deck joints were cured underinsulated blankets. High-strength post-tensioning rods were inserted into the

ducts running longitudinally through

the deck. Jacks were positioned, and therods were tensioned. Finally, all shoringtowers (those supporting the girders

and the V-legs) were dismantled, leavinga freestanding structure.

To complete the bridges aesthetics,orange paint highlighted the bridgesface. Painted lines on the exterior websmimic the angles of the internal strandsof the girders.

In addition to the emphasis placed onachieving a high-quality design withinnovative thinking, designers alsoemphasized construction safety. Thiswas also reinforced

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