V. K. Kumar, P.E., S.E.Vice President, International Portsand TerminalsBERGER/ABAM Engineers Inc.Federal Way, Washington

John C. Bardi, P.E.Project Engineer

BERGER/ABAM Engineers Inc.Federal Way, Washington

An historic world-class shipyard, Bath Iron Works— a subsidiary of General Dynamics and a majorbuilder of complex, technologically advancednaval vessels — required a significant facilitymodernization and shipway expansion to meetcontract production deadlines. A value-engineeredprecast concrete redesign replaced the originalcast-in-place plan for the pile-supported openwharf platform. An extensive precast concreteframing system provided the most efficient anddurable solution to construct this large overwatershipbuilding platform in the harsh conditions ofcoastal Maine. Innovative detailing and a flexibleprecast redesign were key to meeting the owner’saccelerated schedule for critical shipbuildingcapabilities. Moreover, the precast system enabledthe contractor to overcome daunting siteconditions, including a high mean water level,cold weather, tidal cycles and currents, strongwinds, and the variable geotechnical substrate forthis fast-track project.

Overwater construction in a marine environment pre-sents challenges not found in typical building pro-jects. These challenges are compounded when the

facility is located on Maine’s rugged coast, requires an ac-celerated schedule, and has a finish grade just 6 ft (2 m)above mean high water. Under difficult site conditions, in-novative design is required to successfully meet the needsof both owner and contractor.

Precast Framing System Provides Innovative Solution to Modernization of Shipbuilding Facility

20 PCI JOURNAL

William J. Bohlen, P.E.Senior EngineerBERGER/ABAM Engineers Inc.Federal Way, Washington

COVER FEATURE

George Y. Sheng, P.E.Senior Engineer

BERGER/ABAM Engineers Inc.Federal Way, Washington

The modernization of the majorshipbuilding facility at Bath IronWorks (BIW) is known as the LandLevel Transfer Facility. This expan-sion project creates a more efficientand economical shipbuilding facilityand provides the owner with the capa-bility to construct, repair, and retrofitlarge ships on a level platform ratherthan a traditional inclined shipway orfloating dry dock.

The Land Level Transfer Facility, a$240 million project, includes a 15acre (6 ha) land level platform for shipassembly and a 750 ft (230 m) floatingdry dock for ship launch and retrieval.The shipbuilding platform consists oftwo distinct components: a 10 acre (4 ha) retained-fill structure inside asteel sheet pile cofferdam, and a 5 acre(2 ha) pile-supported open wharf plat-form constructed just outside the lineof cofferdam cells. The wharf is thesubject of this article.

The open wharf supports the outer-most of three new parallel shipwaysflanked on each side by a craneway.The overall dimensions of the openwharf are approximately 250 ft (76 m)wide by 850 ft (260 m) long. Fig. 1shows a schematic layout of the ship-yard.

Supporting the new westernmostShipway 1 is the retained-fill portionof the facility. Shipway 2 is situated inthe middle of the new facility and issupported by the sheet pile cofferdam.Shipway 3 is located on the pile-sup-ported open wharf platform east of theexisting fill area. An aerial view of thecompleted shipyard shows the new fa-cility’s first keel assembly under wayon Shipway 1, with the new floatingdry dock visible in the foreground (seeFig. 2).

PROJECT CHALLENGESThe open wharf was extremely chal-

lenging for all parties involved for avariety of reasons. Bath Iron Workshad contracted to build several newships for the United States Navy basedon a long-term schedule that couldonly be met with the production capa-bilities of the completed facility. (Seesidebar, “Distinguished ShipbuildingHistory,” p. 29.) The harsh coastalMaine winter climate was an addi-

May-June 2003 21

Pile-SupportedWharf

Filled Area

Landing Grids

ExistingPier

Dry DockSinking Basin

Dry Dock

Subassembly Building(Existing)

Fig. 1. Schematic site plan of Bath Iron Works shows the existing shipyard andconstruction of new shipbuilding facilities, including the precast pile-supportedopen wharf structure.

Fig. 2. Aerial photo (looking north) of the completed shipyard expanded facilities inoperation. Photo courtesy: Bath Iron Works.

Kennebec River

Cellular Cofferdams

N

22 PCI JOURNAL

tional challenge, where strong winds,snow, and ice floes routinely shutdown marine construction (see Fig. 3).Finally, the overwater constructionwas impacted by the need to set thefinish grade of the new structure at thesame elevation as the existing land-

based shipbuilding facility, nominally6 ft (2 m) above high water, thus sub-merging portions of the superstructureframing with each tidal cycle.

The preliminary design for the openwharf consisted largely of cast-in-place elements supported on concrete-

filled steel pipe piles. The prime de-sign/build contractor, Clark Buildersof Maine, LLC, and its marine worksubsidiary, Atkinson Construction, im-mediately saw that a precast concreteframing system would provide a moresuitable means to meet schedule de-mands and maintain productivity inthe aggressive environment. AtkinsonConstruction contracted withBERGER/ABAM Engineers Inc., aconsulting engineering firm specializ-ing in the design of marine structures,and initiated a value-engineered re-design of the open wharf structure uti-lizing precast concrete components tothe greatest extent possible.

KEY DESIGN CRITERIAThe following elements were in-

cluded in the scope of the project:• Uniform shipyard platform live

load: 800 psf (38.2 kN/m2).• 471 ton (4190 kN) total working

capacity ship unit transporter: twolines of eight axles for a total of six-teen axles, with four tires per axle.Maximum axle load of 72.6 kips (323kN).

• 790 ton (7030 kN) total workingcapacity ship unit transporter: two ex-terior lines of nine axles and one inte-rior line of six axles for a total oftwenty-four axles, with four tires peraxle. Maximum axle load of 79.6 kips(354 kN).

• 90 ton (800 kN) mobile crane:maximum outrigger load of 187 kips(832 kN) on a 28 in. (710 mm) squarepad.

• 300 ton (2700 kN) gantry crane:equivalent working crane rail load of38.1 kips per lineal ft (556 kN per lin-eal meter).

• Shipway loads: 600 tons (5400kN) at 12 ft (3.7 m) on center, appliedas two equal loads of 300 tons on eachside of shipway centerline, or anequivalent working load of 50 kips perlineal ft (730 kN per lineal meter).

PRECAST MODULARFRAMING SYSTEM

The redesigned wharf representswhat is possibly the largest pile-founded wharf of its kind to have anentirely precast framing system. The

Fig. 3. Coastal Maine in winter presents harsh weather conditions for marineconstruction. The average low temperature for December in coastal Maine is about15 F (–10 C). Photo courtesy: Guy F. Atkinson Construction Company.

Fig. 4. Block diagram of basic components of the pile-founded open wharf system.Precast concrete units provided design flexibility for special utility vaults andcomplicated structural geometries.

May-June 2003 23

redesign includes a foundation of pre-cast, prestressed concrete piles fram-ing into precast concrete subcaps,which in turn support precast concretetransverse and longitudinal beams,utility tunnels, utility vaults, and deckpanels (see Fig. 4). Precast concreteelements not only economize and ac-celerate construction, but they alsoprovide the flexibility to form specialvaults, abrupt angular changes, andother difficult closures and connec-tions in a controlled environment (seeFigs. 5 to 8).

The use of precast pile caps repre-sents a departure from the more com-mon construction method utilized inthe marine construction industry. Typ-ically, the pile caps are cast in place toprovide a measure of pile location tol-erance and to simplify the detailing ofthe beam that completes the pile bentin the transverse direction. In thiscase, a carefully detailed precast sub-cap was utilized, which when erectedonto and connected to the pile becamea monolithic extension of the pile.

This precast subcap (see Fig. 9) wasdesigned to function as a staging plat-form on which precast transversebeams are erected, which in turn sup-port precast deck panels that span inthe longitudinal direction, and longitu-dinal precast beams that support craneor shipway loads. Once these beamsare integrated with each other andwith pile reinforcement projectingfrom the subcap, the structural fram-ing transfers load to the pile as if thesubcap no longer existed. With properdetailing, the structural system at thisstage is the same as if the transversebeam had been a continuous cast-in-place member.

An additional benefit of the precastsubcap system was seen in the case ofthe deeper precast longitudinal beamssupporting the heavily loadedcraneways and shipway. Due to theadded beam depth, these locationswould have required a local loweringof a traditional cast-in-place pile cap.A precast subcap provided the abilityto erect these beam members at thesame elevation as the transverse pre-cast beams, creating a deep compositesection after placement of all cast-in-place concrete as well as an efficienttwo-way grid beam system to help dis-

tribute crane and shipway loads tomore piles. Additional detailing coor-dination was required to ensure thatfour precast members could land on asingle cap without interference of the

projecting reinforcing bars or piledowels (see Fig. 10).

Specialized precast sections had tobe developed to accommodate the ex-tensive utilities system required for

Fig. 5. Typical precast framing and integrated deck system.

Fig. 6. Section at shipway showing shipbuilding and transfer systems.

Fig. 7. Section at craneway and utilidor.

24 PCI JOURNAL

shipbuilding. A number of utility tun-nels and vaults, including those forwater, sewer, electrical, steam, com-pressed air, and welding gases, wereincorporated into the framing scheme.

A commitment to the alternativeprecast design on the part of the me-chanical and electrical designers wasrequired because many of the vaultsand tunnel sections had to be re-designed in order to fit within thestandard precast framing modules.Much of the benefit of the precast al-ternative might have been lost with-out this special attention to detail dueto the difficult overwater forming andcoordination required at each of the

numerous vault and tunnel locations.Mean high water elevation is ap-

proximately 3 ft (1 m) above the tunnelcap soffit, or 1 ft (0.3 m) above the tun-nel soffit. Although precast compo-nents aided the contractor greatly in se-quencing the work at these elevations,the contractor needed to coordinatework in these locations with the diurnaltidal cycles, and special attention to thesmall closures in this area was still re-quired. The transverse beams were de-tailed to support both the vault and thedeck panels/vault lids, and arranged sothat the vaults hung from the transversebeams yet still cleared the sides of thepile caps (see Fig. 11).

Fig. 9. Precast pile subcaps in staging yard. Careful detailing of subcaps translatedinto a smooth integration and connection with deck and pile elements. Photo courtesy: Guy F. Atkinson Construction Company.

Effective waterproofing details werecritical for openings and connectionsof the precast concrete elements thatwould be repeatedly submerged inseawater. Epoxy-coated reinforcingbars were used in the utility trenchesto minimize corrosion in the brackishenvironment, and special bentonitewaterstops were used at all utility tun-nel construction joints and closures lo-cated below the mean high water line.

It is significant that the precast sys-tem was adopted even after substantialcompletion of the original design andconstruction on other portions of theproject had already begun. Beyond theeconomic investment required to com-plete the value-engineered design, thecontractor had much at stake in re-gards to construction schedule. To theextent possible, the redesign was fast-tracked in order to limit the associatedscheduling risk. Although extensivecoordination was required between thevarious members of the design team,the final result was fruitful, as the pre-cast framing system enabled the con-tractor to deliver a more serviceableand durable product to the ownerwhile maintaining a very tight con-struction program.

PRECAST CONCRETESOLUTIONS

The primary reason for selecting aprecast framing system was the con-tractor’s desire to eliminate all overwa-ter forming, so as to minimize cold-weather concreting which would havebeen costly and time consuming. Asthe design team developed the revisedframing concepts, other benefits mate-rialized; these included improvedscheduling, an optimized pile layout/deck system, improved structural ser-viceability, and increased durability.

Even with the contractor working ona fast-track schedule, it became clearthat construction of the superstructureframing would have to continuethrough two Maine winters, a time inwhich it is common for concrete workto be shut down. To maintain theschedule, precast components wereproduced in an efficient assembly-linesequence, indoors or in warmermonths, yet erected throughout theyear. By providing protection for the

Fig. 8. Typical precast concrete utility vault and connection detail to transversebeam showing clearance of pile cap.

May-June 2003 25

small closure pours and a special cold-climate concrete mix, progress wasmade even in the coldest weather,when larger-scale cast-in-place workwas not feasible. Meanwhile, pile in-stallation continued throughout theyear, allowing it to stay ahead of thedeck construction schedule.

The selection of precast and precast,prestressed concrete beams and panelsallowed the designers to streamlinemember sizes, effectively simplifyingconstruction. This led to an optimizedpile layout, reducing the total numberof piles required by providing a layoutin which each pile was at or near its300 ton (270 Mg) capacity. These ben-efits were seen even while providingthe superior serviceability characteris-tics of a prestressed (and virtuallycrack-free) soffit in a marine environ-ment. For these reasons, the precastconcrete alternative design was mutu-ally beneficial to the prime contractorand the owner.

An important part of the redesignwas the improved value of the precast,prestressed concrete piles over steelpipe piles. It was shown that the pre-cast piles had a lower initial cost thanthe pipe piles as well as a lower life-cycle cost associated with providingand maintaining a corrosion protectionsystem. This translated directly to amajor cost savings for the owner, andalso provided a more serviceable anddurable facility for the long term.

While the original design used both24 and 30 in. (610 and 760 mm) con-crete-filled steel pipe piles, the con-crete pile design simplified construc-tion by using one size of concrete pilefor all conditions, from the typicalareas of the deck to the most heavilyloaded areas directly supporting theshipway. The final pile design yieldeda first-of-its-kind solid 28 in. (710mm) octagonal pile with a 300 ton(2700 kN) axial capacity. Piles werespaced as close as 6.0 ft (1.8 m) oncenter at heavily loaded shipways andcraneways, and as far apart as 20.75 ft(6.3 m) in more lightly loaded areas.

A corrosion inhibitor was specifiedfor the pile concrete mix to further en-hance the prestressed pile performancein the marine environment. A total of1315 precast piles varying in lengthfrom 30 to 110 ft (9 to 34 m) were

Fig. 10. Precast design flexibility meant that the deeper longitudinal craneway beamsand transverse beams could be erected at the same elevation. Note that four precastmembers rest on a single pile cap without interference to numerous reinforcingelements. Photo courtesy: Guy F. Atkinson Construction Company.

Fig. 11. At high tide, precast transverse beam detailing provides support for both theutility vault and deck panel/vault lid while hanging clear of the pile caps below.Photo courtesy: Guy F. Atkinson Construction Company.

fabricated. The precast piles were fab-ricated by Northeast Concrete Prod-ucts at their plant in Plainville, Mas-sachusetts, and trucked one by oneapproximately 170 miles (270 km) toa staging area about 2 miles (3 km)upriver from the site. A marine load-out facility was provided at this loca-

tion for placement of the piles onscows for pick-up to the pile-drivingderrick barge.

For piles longer than 110 ft (34 m),the maximum size deliverable bytruck, a composite concrete and steelpile was implemented. These pilesconsisted of 90 ft (27 m) precast con-

26 PCI JOURNAL

crete piles and employed a steel pipepile extension located well below thepoint of fixity (of the soil) to extendthe pile into the underlying bedrocklayer. Another benefit of the compos-ite design was that it reduced theweight of the pile, providing moreflexibility for pile installation. How-ever, special rigging was required toavoid overstressing the pile in thesplice area during its lofting into thehammer leads (see Fig. 12).

Approximately 25 percent of allprecast concrete piles were installed ascomposite piles. If all of the piles onthe project were laid end to end, theywould cover a distance of 22 miles (35km). Including the steel pipe pile ex-tensions, that distance becomes 25miles (40 km).

To attain the required 300 ton (270Mg) axial capacity, a 28 in. (710 mm)solid octagonal section was chosen. Ahigh concrete strength [8000 psi (55

MPa) at 28 days], a circular strandpattern, and a heavy circular reinforc-ing spiral were selected to provide afairly ductile pile. In this departurefrom traditional East Coast construc-tion methods, use of an octagonalshape provided a more efficient sec-tion than the typical square pile with acircular strand pattern.

LOAD ANALYSIS ANDMODELING

Detailed investigation of the pile-soilinteraction was required to satisfacto-rily bracket the design so that one pilesize could be used in all cases. Endconditions ranged from fixed-pinned atzero overburden locations to fixed-fixed in deep zones. Since the stiffnessof the alluvial material was highlyvariable from boring to boring, severalof the deep overburden locations hadto be checked. After analyzing allcases, the resulting maximum effectivepile length elected for the design of allpiles was 70 ft (21 m).

Extensive three-dimensional analy-sis was required to demonstrate thatthe final piling layout would supportall possible load combinations associ-ated with ship assembly. This was accomplished by means of a three-dimensional analysis model and a nu-merical influence field approach. Inthe model, the deck was subjected to apoint load moving incrementally intwo directions, creating thousands ofindividual load cases. Outputting re-sults for all the load cases at any onelocation provided enough data to cre-ate a three-dimensional influence fieldfor a specific pile.

Construction of the three-dimen-sional numerical influence field wasaccomplished by post-processing rawcomputer model output using a cus-tomized spreadsheet. The computationof maximum pile loads was made onthe same spreadsheet by overlayingnumerical footprints representing thevarious live loads over the field of in-fluence ordinates, much as if the foot-prints were drawn to scale and tracedonto a contour map (see Fig. 13).

Analysis of the non-prestressedtransverse beams was performed usingthe same three-dimensional model asthat used for the piling. This enabled a

Fig. 13. Pile design influence field loading analysis data representation.

Fig. 12. Precast piles being lofted with specialized rigging. High strength concretewas used in the 28 in. (710 mm) solid octagonal section piles with spiralreinforcement to provide both strength and ductility. Photo courtesy: Guy F. Atkinson Construction Company.

May-June 2003 27

similar influence field approach to de-termine the maximum stresses onthese elements. Longitudinal beamssupporting shipway and crane loadswere designed using an influence lineapproach while considering the vary-ing vertical stiffnesses of bents in dif-ferent locations on the wharf.

Deck panels were designed in thesame way for uniform load, but withspecial plate modeling for concen-trated loading. In the case of both pan-els and crane beams, special consider-ation had to be given to prestressdevelopment and load transfer, due tothe relatively short span length [16.0 ft(4.9 m)] between bent centerlines.

The composite 20 in. (510 mm) deckslab was designed to work as a one-way system, although particular atten-tion had to be given to the two-wayperformance of the precast deck panelsat their longitudinal shear keys. Elec-trical and mechanical conduits locatedin the cast-in-place topping limited theprecast deck panel depth to 8 in. (203mm), making the panel too thin for atypical shear key detail (see Fig. 14).Because the very large concentratedloads can easily overload deck panelsif sufficient shear transfer is not avail-able, special nonlinear finite elementanalysis was performed to demonstratethat the stiffness of the 12 in. (305mm) composite topping was enough tosubstitute for the action of a shear key.

Analysis showed that the toppingdoes transfer enough shear to dis-tribute load to adjacent panels, al-though with an associated transversemoment and a tendency for the paneljoint to open. However, crack widthsassociated with opening at the jointunder the heaviest concentrated loads— generally transient in nature —were computed to be less than thestandard accepted criterion for marineconstruction, or 0.006 in. (150 μm).

A similar analysis was made at theends of the deck panels, where pro-jecting strands would have made erec-tion difficult because of closely spacedstirrups projecting from the beams.Strands were, therefore, burned flushwith the panel ends. However, analy-sis showed that at bents with thelongest and most elastic piles, concen-trated loading can create positive mo-ment at the face of support.

Additional inelastic analysis demon-strated that while the joint would tendto open at the bottom of the joint insuch a case, crack widths would re-main small, and reinforcement re-quirements could be handled with alayer of bars (apart from typical nega-tive moment steel) located just abovethe top of the panel.

Fig. 14. The precast deck panel was limited to an 8 in. (203 mm) depth, too thin forshear key performance. Special nonlinear finite element analysis demonstrated thatthe composite topping was sufficiently stiff for adequate load transfer. Photo courtesy: Guy F. Atkinson Construction Company.

Fig. 15. Once the precast piles were driven to refusal in the pre-drilled rock sockets,temporary bracing was installed to maintain position until the final deck integration.Photo courtesy: Guy F. Atkinson Construction Company.

CONSTRUCTIONAn important issue for the success

of the precast system was control ofthe tolerances of both the pile locationand the erection of subsequent ele-ments. The team adopted the philoso-phy that all caps and beams must beplaced on the grid lines, and that anypile tolerance issues must be adjusted

28 PCI JOURNAL

mm) diameter steel casing was low-ered and cleaned out down to the rockelevation. A second inner casing wasthen spun into the bedrock using aspecialized drill to create a 30 x 30 in.(760 x 760 mm) minimum socket.After the hole was flushed clean of de-bris, the pile was lowered into posi-tion, the outer casing extracted, andthe pile proofed by driving to refusal.Once the piles were proofed, tempo-rary bracing was provided until thepiles and following deck elementswere fully integrated (see Fig. 15).

Rather than shift a subcap to accom-modate an improperly positioned pile(which would in turn require the shift-ing of subsequent precast elementsand likely cause erection interfer-ences) sufficiently large voids wereprovided in the subcaps. Then, if thepiles were not within the strict 3 in.(76 mm) tolerance limits, special andfast-tracked coordination between thecontractor, the design team, and theprecaster began.

The team produced a custom precastsubcap designed to resist the higherunbalanced loads, yet still provide thestandard bearing surfaces so that fol-low-up work was unaffected. In a fewcases, special cast-in-place modifica-tions were required, but in general theprecast system proved to be readilyadaptable in the field.

The additional coordination effortspent on the design and constructionof the piles and caps began to pay offduring the construction of the super-structure. Erection of the precastbeams and deck panels proceeded veryquickly because the caps were kept towithin the nominal positioning toler-ance — this despite the fact that someof the closures became crowded withreinforcement projecting from all fourhorizontal directions as well as verti-cally from the pile heads.

The beam ends essentially createdthe side forms for the closure pour.Additional formwork was only re-quired to close the gaps at the cornersof the beams, and the precast subcapprovided an efficient platform to sup-port this work. Once these closureswere made, the precast deck panelswere placed, followed by the finaldeck topping (see Figs. 16 and 17).

The erection of the various utility

within the pile cap. But because of thehighly varying geotechnical profile ofthe site, pile installation to the re-quired tolerance proved challenging.

Subsurface conditions consisted ofloose-to-medium dense alluvial sanddeposits overlying dense gneiss.Depth from the final deck grade to therugged underlying bedrock variedfrom approximately 25 ft (8 m) tonearly 150 ft (45 m), while the over-

burden depth varied from zero toabout 100 ft (30 m). In some cases,the local profile of the gneiss bedrockstratum was found to be sloping muchmore steeply than 45 degrees.

All of the precast piles were in-stalled from a sophisticated barge-mounted template, which had beenguided into position using the GlobalPositioning System (GPS). Once thebarge was positioned, a 36 in. (915

Fig. 17. Carefulcoordination was

required to ensurethat bars

projecting frompiles, subcap,

transverse beamsand longitudinal

beams did not create

interferencesduring erection. Photo courtesy:

Guy F. AtkinsonConstruction

Company.

Fig. 16. Closeup of construction showing crane beam closure. Photo courtesy: Guy F. Atkinson Construction Company.

May-June 2003 29

Fig. 18. Aerial view(looking west)shows constructionsequence at theLand Level TransferFacility. The totalproject added 15 acres (6 ha) of the modernshipbuildingfacilities in Bath, Maine. Photo courtesy:Bath Iron Works.

DISTINGUISHED SHIPBUILDING HISTORY

by D. Joseph Comeau, Jr.Manager of Facility Engineering, BIW

In the 1840s, The Bath Iron Works in Maine began pro-ducing the finest steel-hulled ships in the world. The year1890 saw BIW winning contracts for two steel-hulled gun-boats, initiating a fruitful relationship between BIW andthe U.S. Navy which continues to this day. Over the lastcentury, BIW has provided battleships, frigates, cruisers,and destroyers for the Navy. Since the 1950s, BIW hasserved as the lead shipyard for ten surface ship classesproduced by the U.S. Navy, more than any other U.S.shipyard. In 1995, BIW was purchased by General Dy-namics, further enhancing the company’s technologicalexpertise and capabilities.

Today, BIW, the second largest private employer in theState of Maine, builds AEGIS Destroyers — the most ad-vanced and capable warships in the world. With the com-pletion of a facility modernization in 2001, BIW became astate-of-the-art shipbuilding facility. These improvementswill enable the company to remain the “best value” ship-yard in America, offering unprecedented productivity,quality, and affordability to its customers.

Two major milestones in BIW’s long history are worthyof mention:

• Between 1940 and 1945, BIW built 82 naval de-stroyers, totaling more ships than the production of theentire Japanese Empire.

• In 1987, the USS Thomas Gates, the first BIW-builtguided-missile AEGIS cruiser, was delivered.

USS ArleighBurke

30 PCI JOURNAL

vaults and tunnels went quickly forthe marine contractor as well as themechanical and electrical subcontrac-tors (see Fig. 18). The modular drop-in design allowed for the sections tobe quickly turned over for utility in-

stallation, helping keep all aspects ofthe project on schedule. Again, thisimproved construction schedule morethan made up for the redesign effortsrequired of each of the various trades.At times, over six barge-mounted and

Table 1. Precast components for the Land Level Transfer Facility, Bath Iron Works.*Component Dimensions Number of pieces

Precast prestressed concrete piles 28 in. (710 m) octagonal section, of varying lengths, totaling 105,000 lineal ft (32000 m) 1315

Precast concrete pile caps2 x 5.5 ft (0.6 x 1.7 m) section of varying length, with openings for 1 to 3 pile integration

6698400 total lineal ft (2560 m)

Precast concrete transverse beamsMain transverse framing element 2 x 3.5 ft (0.6 x 1.1 m) section of varying length

6149250 total lineal ft (2820 m)

Primary longitudinal member for supporting vessel construction and transport loading

Precast prestressed shipway beams 2 x 6 x 12.5 ft (0.6 x 1.8 x 3.8 m) 192

2400 total lineal ft (730 m)

Primary longitudinal member for supporting crane loads

Precast prestressed crane beams 2 x 8 x 12.5 ft (0.6 x 2.4 x 3.8 m) 206

2530 total lineal ft (770 m)

Modular unit to fit in deck framing

Precast concrete utility tunnels Typical size 4.5 ft deep x 10 ft wide x 12.5 ft long (1.4 x 3.0 x 3.8 m) 121

1550 total lineal ft (470 m)

Special precast utility access tunnel modular unit

Precast concrete utility laterals 14 ft wide x 4.5 ft deep (4.3 x 1.4 m) – length varies 20

210 total lineal ft (64 m)

Provided for electrical, mechanical, sewer, oil-water separation, and crane power

Precast concrete utility vaults Modular design to fit in framing system 39

Size varies, typically 5 ft deep x 6 ft wide x 12.5 ft long (1.5 x 1.8 x 3.8 m)

Precast prestressed concreteMain deck element – structurally composite with concrete topping

deck panelsTypical size 8 in. (200 mm) x 6 ft (1.8 m) x 13.5 ft (4.1 m) long, varied to suit deck geometry 1699

22,930 total lineal ft (6990 m)

Similar to deck panel, with some lids removable for tunnel access

Precast concrete utility tunnel lids Typically 8 in. x 6 ft x 9 ft long (200 mm x 1.8 m x 2.7 m) 226

2030 total lineal ft (619 m)

Total pieces 5101

* Total dimensions for this pile-supported structure were 920 ft long x 258 ft wide (280 x 79 m), amounting to 220,660 sq ft (20500 m2), or 5.1 acres (2.1 ha).

Item Cost

Cost of cranes and equipment $60 million

Cost of precast open wharf platform $25 million

Cost of retained-fill structure and other work $155 million

Total project cost $240 million

Table 3. Project timeline.Project stage Time

Completion of preliminary design October 1998

Start of precast design November 1998

Start of precast manufacture March 1999

Start of pile driving March 1999

Completion of precast design April 1999

Start of precast superstructure erection July 1999

Completion of pile driving April 2001

Completion of project July 2001

Table 2. Project cost data. crawler cranes were required to main-tain the accelerated constructionschedule (see Fig. 19).

The sheer magnitude and complex-ity of the completed project is a note-worthy achievement in itself. A com-bined total of 5101 precast concretemembers were produced and installed,including 42 main product types andan even larger number of subcategoryelements (see Tables 1, 2, and 3). Dueto the size and scope of this project,the work was necessarily dividedamong three precast manufacturers(see “Credits”).

CONCLUDING REMARKSThe single most important aspect of

the project is the benefit realized bythe owner and the contractor due tothe adoption of the precast framingsystem. By maintaining a fast-trackconstruction schedule despite difficultworking conditions, the contractor wasable to help the owner successfullymeet critical deadlines for vessel con-

May-June 2003 31

tract construction. At the same time,the owner has been provided a modernfacility with superior serviceabilityand durability that will fulfill the ship-building production needs for its 50-year service life and beyond.

The Bath Iron Works – Land LevelTransfer Facility is an excellentdemonstration of how a precast con-crete system provides flexible, innova-tive, and cost-effective solutions tochallenging site and schedule issuesfaced by the owner and the contractor,particularly in a design-build scenario.

ACKNOWLEDGMENTSThe authors wish to express their

appreciation for the efforts of PhillipSheridan, project engineer for Guy F.Atkinson, and his construction engi-

neering team, whose coordination en-sured successful completion of thecomplicated precast system. The au-thors also wish to thank McCoy Butlerof Moffatt & Nichol Engineers for hisvaluable input during the design andconstruction phases of the project.

CREDITSOwner: Bath Iron Works, Bath,

Maine, a Division of General Dy-namics, Falls Church, Virginia

Prime Contractor: Clark Builders ofMaine, Boston, Massachusetts

Marine Contractor: Guy F. AtkinsonConstruction Corporation, Denver,Colorado

Prime Consultant: Moffatt & NicholEngineers, Baltimore, Maryland

Open Wharf Consultant: BERGER/

ABAM Engineers Inc., FederalWay, Washington

Precast/Prestressed Concrete Compo-nent Manufacturers: - Bayshore Concrete Products, CapeCharles, Virginia, in associationwith Precast Structures, Inc.,Auburn, Maine, for precast/pre-stressed deck panels, precast/pre-stressed crane and shipway beams,and precast concrete pile caps.- Rotondo Precast, Rehoboth, Mary-land, a division of Oldcastle Precast,Northeast Group, Bethlehem, NewYork, for precast concrete utilitytunnels and lids, precast concretetransverse beams, and precast con-crete utility vaults.- Northeast Concrete Products,LLC, Plainville, Massachusetts, forprecast/prestressed concrete piles.

Fig. 19. Overviewof project showingnumerous barge-mounted cranesoperating at theBath Iron Worksconstruction site.