Wisconsin Avenue Viaduct Design-Construction Highlights

HARRY H. EDWARDS INDUSTRY ADVANCEMENT AWARD

Stephen P. Wanders The new Wisconsin Avenue Viaduct in Mil P.E., S.E. waukee, Wisconsin, is an imaginatively de Manager, Transportation Services signed 1456 ft (443.80 m) long eleven-span CH2M Hill, Inc. Dayton, Ohio precast, prestressed concrete arch struc ture. A key element in the design of this bridge is the use of curved U-shaped pre cast, post-tensioned arch segments that functioned as both load-carrying structural members and as self-supporting permanent forms. The deck is formed by standard AASHTO pretensioned concrete girders that frame into cast-in-place cross beams. The innovative use of precast arch segments Mark A. Maday, P.E., S.E. and standard girders shortened the con Project Engineer struction period and cost an estimated $2 CH2M Hill , Inc. Milwaukee, Wisconsin million Jess than a similar cast-in-place con crete arch bridge. This article discusses the design challenge, design solution, aesthet Charles M. Redfield, P.E. ics, structural design considerations, con Consulting Engineer Mill Valley, California struction highlights, and cost breakdown.

n February 1988, the City of Milwaukee, Wisconsin, began planning the replacement of an old viaduct struc I ture over the Menomonee River Valley. The bridge, which provided an important link in the local transportation system, was slowly deteriorating and becoming too costly to maintain. The 1 0-span, open spandrel-arch viaduct with eight graceful arches was both the gateway to the downtown Mil waukee area and an important landmark. As the state's fust large-scale concrete bridge, it was eligible for inclusion in Jiri Strasky, Ph.D., P.E. the National Register of Historic Places. The City of Mil Consulting Engineer waukee wanted the new structure to be at least as impres Mill Valley, California sive as the one that had served the city so well since 1911 .

20 PCI JOURNAL Fig. 1. The arch concept was developed specifically because of the expressed vi sual importance of the original viaduct.

To solve this problem, the CH2M is at the same time aesthetically pleas verse cross beams reduced the depth Hill, Inc., design office in Milwaukee ing (see Fig. 1). This article describes of the structure, which enhanced ap was retained to provide planning and the design concept, aesthetics, struc pearance, and eliminated bearings to engineering services. Assisting the tural design features, construction as minimize maintenance requirements. project team were consultants Charles pects, and cost considerations. The use of cast-in-place concrete M. Redfield and Jiri Strasky as well as closures for all precast components the client, the City of Milwaukee, and and the absence of bearings improved the Wisconsin Department of Trans DESIGN SOLUTION the structure's strength and durability. portation (DOT). The goal of the de The new viaduct is a precast, pre To accomplish this integration, a spe sign was to seek a delicate balance be stressed concrete strutted arch, the first cial concrete mix was specified. The tween structure, function, aesthetics, of its kind in the United States. The mix was workable without segrega cost, and funding to satisfy the diverse strutted arch derives its name from its tion, yet delayed initial set for long pe interests of the various parties in structural function and the shape of its riods under varying temperatures. volved in the project. main load-carrying members. The U Because vertical loads from the Specifically, two major design crite shaped precast, post-tensioned arch deck are transmitted only at the arch ria needed to be addressed in the struc segments were curved and came in crown and pier walls, a true parabolic tural solution: pairs. The U-shape facilitated handling arch was not required, and straight • The public's desire to retain a tradi and transportation. struts would have sufficed. However, tional arch design appropriate to the An important design concept was the to produce an arch-like shape, the sup bridge's surroundings. use of the precast arch segments as porting segments were intentionally • A state-of-the-art simple girder self-supporting permanent formwork curved and designed to resist the re structure with a replaceable deck for casting concrete in other parts of the sulting eccentric axial loads. that conforms to the maintenance structure. This feature minimized the Supporting the deck framing only at policies and budget advocated by need for ground supported falsework. midspan allowed the use of standard the DOT. Standard AASHTO pretensioned pretensioned concrete girders. This The design of the new bridge ful concrete girders were used to frame will facilitate deck replacement if it is filled both requirements by providing the bridge deck. The unique method of needed in the future. a simple and economical structure that framing the deck girders into trans- Because interior vertical load-carry-

September-October 1994 21 8 X 48.16 l t22.86t (75') I (8 X 158')

Fig. 2. Schematic views of (top) the elevation of the bridge, (left) the elevation of a typical span, and (right) a typical section. Note: Dimensions are in meters. U.S. customary units are in parenthesis. ~ ing elements are not require , the vation of a typical arch span, and a are frame connected with the deck and spandrel areas look relatively open and typical section. A detailed partial gen piers. The arch ribs form a continuous graceful. Complementing the struc eral plan and elevation of the bridge is arch structure of eight spans. ture's architectural character is a con given in Fig. 3. The precast segments have a trough crete railing that was developed by the The main spans consist of 32 pairs cross section and were concentrically Texas Department of Transportation. of curved, U-shaped, precast concrete post-tensioned for handling and erec Post-tensioning was used to rein segments. Each arch segment is 79 ft tion. Once erected, the troughs were force both the arch ribs and cross (24.10 m) long by 7 ft 3 in. (2.21 m) filled with concrete and combined beams in the superstructure. It opti wide by 3 ft 5 in. (1.04 m) deep. with the precast segment to form the mized their size and shape, provided Reuse of casting forms afforded the completed arch ribs. The precast arch continuity, and increased durability. efficiency of mass production, thus segments are 78 ft (23 .80 m) long and Lastly, a dense concrete bridge deck significantly lowering the cost of each weigh about 61 tons (55 metric tons). overlay was specified to produce a segment and reducing construction At a distance of 20 ft (6.09 m) from smooth driving surface and to increase time. Fig. 4 shows the framing plan of the crown at the bottom comers of the durability. an arch rib for Spans 4 through 9. Fig. trough cross sections, two anchor 5 shows a plan, elevation, and detail of blocks were provided for anchoring a precast concrete arch rib. short continuity cables over the crown. STRUCTURAL DES"W The typical span of 158ft (48.16 m) The webs were connected by a slender The viaduct has 11 spans - one is formed by twin parallel arch ribs diaphragm to eliminate secondary 75 ft (22.86 m) span at the west end, that support a deck assembled from stresses due to transverse moments eight 158ft (48.16 m) main arch spans, pretensioned concrete girders and a from prestressing. and 42 and 75 ft (12.80 and 22.86 m) composite slab. The same deck is used The precast and cast-in-place con spans at the east end - for a total for the end spans. crete of the arch ribs were made com length of 1456 ft (443. 80 m). The Each individual arch rib is assem posite by reinforcing steel stirrup dow clear roadway width between curbs on bled from four precast segments con els protruding above the bottom slab the structure varies between 58 and nected at the crown with a post-ten of the troughs and by overlap of rein 70ft (17.76 and 21.41 m) with a 7ft sioned concrete joint. The ribs are forcing steel coupled with the precast (2.10 m) sidewalk on the north side. supported by massive piers of rein web reinforcing bars. Reinforcing bars The deck area covers 101,076 sq ft forced concrete with cast-in-place also protrude from both ends of the 2 (9400 m ). joints between the precast arch seg precast arch segments where they Fig. 2 shows a schematic view of ments and the pier caps. The piers also overlap to form continuous reinforce the elevation of the entire bridge, ele- support the twin spandrel walls that ment of the joints.

22 PCI JOURNAL en (!) ~ (!) 3 CT (!) b (") 0 CT l ' I l I ..~ ,' \\\ ' I I I ~ 5 r!- -i-l--i-H1- r-l c_~7H ARCH RIB=+------;~1 - 1 I ' ------:>--T-1 I g "~"' -- \\' I- r 1 I. 5_ I l I !j 1 1 !j 1 1 ij 1,.?. \ - '-\\\"\---;c,._,l !j I ~ARYSIUL ~ .~J... ( I 1...: I jr~3!oo.oo I 1....: I fr~.!saoo SHEETPlMC-...... _ ; I ""'-= f~~ts;t too\ \ \\\ I I...: ~~,7+74.00) 'f-+' ___ :__ ,.,:/:::_+a ... n -----p- ----,~ L--- \ \ • \ I I I ~ ~ ~ ~ . ~ ~---;::::__.....----- ~HJI~~~ ----r------·- ----t------~ --

~------' \\ ---nT------~rr------\I\ '\ ~r\ SRi%£ RALS ANO UCHT POLES HO T SHOMIH IN Pl.AN FOR ClARITY..

au } I

~= =~-~ .] CL 15.67

r51l'-o"'

ELEVAVQN

~ Fig. 3. Partial general plan and elevation of bridge. ARCH RIB fRAMING PLAN - SPANS 4 THRV 9 (CTARO

Fig. 4. Framing plan of an arch rib for Spans 4 through 9.

Standard 45 in. (1143 mm) deep, The girders have only two continu 1. Erect the precast arch segments. Type III AASHTO pretensioned con ous longitudinal reinforcing bars situ 2. Connect and prestress the seg- crete girders were used to span the deck. ated close to their top and short rein ments at the crown. A typical span is formed by 2 x 8- 76 ft forcing bars situated at their ends. The 3. Fill the arch with concrete. (23.16 m) long concrete girders and a girders are pretensioned with draped 4. Erect the pretensioned deck girders. composite slab. A total of 155 girders strands. The strands protrude from the 5. Cast the deck slab, diaphragms, were used that varied in length from 39 ends of the girders and are anchored in and cross beams. to 76 ft (11.89 to 23.16 m). Special de the post-tensioned transverse cross Except for temporary use of fal se tailing was provided at the ends of the beams. Because the strands are bent work support while erecting the arch girders to facilitate an integrated con and sufficiently anchored, they func elements at the crown, no other nection to the cross beams. tion as reinforcing steel, resisting both ground supported falsework was Fig. 6 shows a girder framing plan negative and positive bending mo needed because the arch ribs served as for Span 3. Elevation and typical sec ments that occur in the joints during the platform for deck construction. tions of pretensioned concrete girder their service life and will occur during A static analysis of the structure together with strand details at girder the eventual replacement of the deck. was carried out using conventional ends are shown in Fig. 7. Figs. 8a and 8b show the detailed practices and standard computer pro The girders are supported by cast-in erections steps used in constructing grams for plane and space frames. place cross beams situated above the the bridge. Fig. 9 is a simplified The structure was modeled as a con spandrel walls and at the arch crown. schematic showing the erection se tinuous arch that supported the gird They are stiffened at their midspan by quence of one span. ers at their midspans. The girders additional cast transverse diaphragms. The bridge was designed to allow were framed into the spandrel walls To allow movement of the deck with progressive erection from one abut that were fixed into the piers. temperature changes and with creep ment to the other, eliminating the need S i nee both the arches and deck and shrinkage of concrete, the cross to temporarily strengthen the piers for were assembled from concrete com beams are framed into a slender span excessive unbalanced lateral thrust. ponents cast at different ages, and the drel wall. Two walls are provided at The sequence of construction gener structure underwent deformation each pier, and the adjacent cross beams ally followed distinct, overlapping changes during erection, creep and are separated by expansion joints. stages that were arranged to keep un shrinkage of the concrete signifi Thus, the deck forms a two-span con balanced thrust within acceptable lim cantly affected the performance of tinuous frame structure for the live its. A typical arch span was con the structure. To account for these load within each arched span. structed in five stages: volume changes, a detailed computer

24 PCI JOURNAL GENERAL NOlES· I. AROf Rf8 fl..DIENTS ARE JO£NnCAL D«:EPT AS N01FD. Z. TH£ ARCH fiDIENTS SHALL BE PROWJ£0 Mf7H A SUITABlE UF71HG DOfCE FOR HANDUNG MD EREC TINC THE fi£NENTS. I .l ALL RfJHFORCING IH AACii EJ.DI(NT5 SHALL 8£ £POXY COA.TlD • .f. INTEHTIOHALLY ROUGHDIINrrRKIR NIO END CONTACT SURF'ACE'S OF ElEitiENT. .5. ONE ARCH RIB CONSISTS OF FOUR ARCH RIB El.DIEHTS.

PRESTRESSING NOTES (POST- TENSIONING): '· ~!N~Jf~~~~~~~~~5~s1-~~~t~LR!/:n~OOH ~~~1, ~ ~~ b~s. OETAJLS ON 1H£SC PlANS HA \£ BEEN Dfm.QPED FOR 0.~ 2. ~f[Jwr-'a..JNnJ""~~~~~IH~~~~uffncwN«J ARCH RIB PLAN FRICT10N HA \o£ TAKEN ptAC£ P • fo.JK ~=s- :: ~~m=~~ P-292K 1 17-f" OM BAR T£HDOH: P • JIO K ffliC T10N COEF'RCICNT: MOS6tE CO£mCI£NT: STRAND AHD BAR TENDONS AHCWJR SET:

J,. T£HOON FTJRCC DUE TO .M.CKING SHALL NOT EXCCFO A IJAXIMIAI OF' 75 PERCeNT OF 1Hf; ~=!JlD~~~Slf?Gcu'J.'RAN'Wf§31_1/ifi../l'f.,RfN?!JER SEAT1NG SHALL NOT

4. 1H£ 3 - 0.6" DIA STRAND TDIOOHS SHALL flE SJRESSED Jt) Po • SO K PER TfNOON BCFOR£ LJFTJNC PRFCAST D..DIENT OlJT OF TH£ CAS11NG FTJRM. F1JU. STRESSING OF 1EHDOHS SHALL 8£ OOHE' SHOR n. Y BEFORE TRANSPORT TO »£ JOB SIT£, NO SOONER THAN 50 DA t'S AFTER CAS T1HG. S. CONCReTE" STRENGTH AT TMI£ OF IHiffAL. S7R£SSIHC SHALL 8£ fC - .1500 PSI MNIIMM. 6. ALL DUCTS SHALL BE ROUND AND OF SDII- RfGID GAL V/INIZED COHSTRUC T10N: ~f 5§~f~.. ;!:1S~!1!~ = ~tt" +.005't!! stOP£ FROM S.P. TO S.P. 7. BEARING PU 1£5 FOR rEHOONS LARGER JHA/11 P - 1:50 K SHALL BE SVPPU£D llf7H ADf'OUATE SPffAL RDHFORCOIEHT AS SHOWN 1H OCTAII.. ll. STRESSING SEQUENCE 7D 8C ARRANG£D IN ORDER 70 A \oOIO £CCEH1RK:: OR O\o£R· S7Rf'SSINC CONOITJOHS. fl. ALl. TEJtiiJONS SHALl. fl£ GROUTED AND AHQ-KJRAC£ POCKETS FlU£D llfl'H HON·SHRIHK CXINCR£1£. 75'-10 " 10. GROUT \o£H1S SHALl. 8£ PROWlED A T ALL ANOUJRAGES OR AS INDICA 1ED IN 1HE ORA llfNGS.

I 1. 1H£: CONTRACTOR SHAU. 8C RCSPONSI9L£ FOR AU. IKCESSARY ADJJ~TS OF THE: R£/NFORCING STm Waf ltiAY INTERffRE IW 7H 7H£ STRESSING AND PU.OHG OF 1H£ DOliN STA UQN ARCH RIB ELEMENTS UP STAUON ARCH RIB ElEMENTS POST· TFHSIONING JENDCWS. ALL ROHFORCEMCNT AD.AJSJMOIT PR SHALL BC ARCH RIB ELEYAVON SUBNITTED lO THE: EHGINEIR FOR APPROVAl. J2 . FVU. SAF£TY PR£CAU110NS SHALL. 8£ TAKEN •7H ALL S1R£SSIHG Cf'E'RA JJQIIIS. L£IDill + 11 - ~~ • TZ- ,•' ,' ,s~l!:buru:JI.~t C) I I * ,._,.,.. ~ a'i I b. I I I .. 2 '- 0" opnQN "A" opnQN •a• DETAIL CD

stfOlt!NG DIMENSIONS AND POST-lENS!ON/NG SHOit!NG 8EINFQRC!NG SECTION 0'\

Di Fig . 5. Plan, elevation, and detail of precast concrete arch rib. 1\) 0>

f~~T STA JJH2.00 w~--T ~------_jl~~~-~·~·------1 STAf~ Gn OO 5PAN 2

l -~ -

I..WC A G/RQER fRAMING PLAN - SPAN J

GltmEB fBEC.llati. fl.(k'd llati.S 5PNI STA ...,.,., ...,.,., -2 -~ 11+ 4400 ...... 111. 16 -5.,_,. 81.00 ...... - J2+ff.Z5 ..... 81.23 .,_.. , -·81. .. 81. .. -·81.45 er. ~ -·IIU Z 1:1.f.U. 15 ..... tn.Zf 8 1.42 ..... 81.58 ll1.50 81.J2 8J.rf f2+ t 7.00 87.3 7 81.54 8 7. 72 ..... 52.02 IJ.#H 8 7.57 8 7.!JO JIQJE;. a£VA110NS ARC BOTTOII OF GIRDeR AT POINT SHOWN.

c... 0 c :IJz f:. Fig. 6. Girder framing plan (Span 3). 7S-U

NO. $ S nRRUP$ IH P.AJRS ~ ~ STIRRUP SPACING SP I r4 SPAC£5 • s·- 7'-o· tO SPA. e 9SPA e 7SPA e f1 SPA . 7SPA. e gSPA e fOSPA e 14 SPAC!'S e 6 '" - 7'-o• SP ... - ... - ... I: ~ :: \"·- ,.. .. J.,,·-o·- .,._:T -J,. .. ;t_, •._s-1' ·-o·-7'-01 , .. _e· -J·I ~~· _7'-ts I ... I if,g 5 C

GIRDER &tH.fi!fi@lbjf1D LOAD (E5111WA 1lD AT SID DA rs AFT£'R R£L£AS£)

G/RQER NOTCS; f. ALL SJJRIIft.PS SHALL BE IN PAIRS. TQP \rtEW OF G/RQER ENDS 2. 1J1I£ GRDERS SHALL BC PR0\4DfD IWTH A SIATASLE UF71HC D£WC£ FOR HANOUNG AND £RCC1WG 1HE GR)fJitS..

~ ALL GlftiiERS SHALL B£ CAST FUti lENGTH AS SHOtW. SHEAR TEElli DETAIL Cf\ 4. STRANDS SHALL BE FWSH IW1H £ND OF QRDER. UNl£SS N01£D OlHER*SE. 5. ~~~ilf~~~~(F1R~&

I. ~~~ ~~- 4 AND NO.~ S11RRUP$8'". B£HD CACHEHD OF 2 NO. 5 BARS 7. lMTA SHOteHIN 001.£ClKW DATA IS THCORflJCAL AND flAY VARY IW1H ~ S71f£NGTH, VARWil.E Pff£STR£SS CONDfTIOHS AND PR£Sm£SS 1'" OIA.. HOLES AT QIROER £NOS, Tl'P. 4 ~~Wflf~s'fROllf:lt'BAsm ON STRNID ARRANGIEliCNT SHOIIH. SHALL 8£ 5.lOO p.t

I. r:=~~T~:g,~~,=~~ 10. wr5ai.1..AN£OIJ INSERJS AND C0NN£CTJON Of'T..U.S AS AMY 8£ RE'OURfD FOR n..OOR DRAIN 8RACJI('£1S AND VTIJTY DUCT SUPPORTS NOT SHOMH. ~~BAI~rlcv~ rr. ALL GIRO£'R RE1NF"ORCINC PRO.ECJWC ~ro D£CK 1'-o•..._ LAP SHALL 8£ EPOXY c:QitJm.

12. PR£S1R£SSINC STRANDS SHALL 8£ )t'" OIA t/NC'OARD ~-MIRf'LOW R£LAXA »>N STRANDS COI¥"0RttMHG TO MSHro ~ GRAD£ 270. f.J. PR£S1R£SSIHC SlRAICJS SHALL 8£ BCNT caD MI'7H A 1t1H11U1t1 8ENO RNJIUS OF~.

SECTION UD

Fig. 7. Elevation and typical sections of pretensioned concrete girder together with strand details at girder ends (Spans 2 and 3}. -o ERECT10N SEQUENCE Q c.... 0 c zJJ F= Fig. 8a. Erection sequence of bridge (Stages 1 through 4). (/) C1) ""0m 3 r::r C1) 6 u 0 r::r ~ ......

ERECTION SEQUENCE

~ Fig. 8b . Erection sequence of bridge (Stages 5 through 8). (a) Erection of arch segments on temporary supports

(b) Continuity post-tensioning across crown

(d) Lowering girder on to temporary supports

(e) Placement of cross beams and deck

Fig. 9. Simplified erection sequence for a single span.

30 PCI JOURNAL Fig. 10. Use of precast concrete allowed work to continue through the winter. It Fig. 11. Special falsework was needed also minimized the need for shoring and falsework to avoid disrupting heavily to support the arch rib shoring towers traveled train routes. over the river. analysis of time-dependent effects was conducted by Jiri Strasky. By being able to predict the deformations and redistribution of internal forces within the structure, stresses could be checked and appropriate connections could be devised between the struc tural members.

CONSTRUCTION HIGHLIGHTS Demolition of the old deteriorated bridge began in October .1991. The contractor had only 24 months to carry out the demolition and construct the new bridge. Construction began in January 1992, Fig. 12. lnfill concrete was cast simultaneously on both sides of the arch ribs to 3 months into the 6-month demolition maintain symmetric loading. Top forms contained the concrete in the arch ribs. phase. Excavating, forming, and plac ing concrete for the 10 sets of piers progressed along with the construction struction site. A light sandblast finish center of the span. After closure cast of abutments and retaining walls. The was applied to the arch segments and in-place concrete was placed at the exposed flat surface areas of the cast they were treated with a clear, non crown, the arch segments were post in-place concrete for the substructure staining penetrating silane sealer. The tensioned together, and reinforcing feature decorative rustications. Steel producer used two forms to cast 64 steel was placed within the U-shaped forms for the piers and abutments arch segments. The segments were par segments to prepare them for the infill were lined with plywood and styro tially post-tensioned before lifting pour. Erection and post-tensioning of foam panels to create the relief pattern them out of the casting forms. The seg the arch segments were completed in the panel. To protect the concrete ments were fully post-tensioned just over a 7-montb period. surface during overhead construction, prior to transporting them to the bridge Figs. 10 through 15 show the bridge styrofoam was left in place. site to minimize time-dependent creep during various stages of erection. The precast concrete arch segments deformations. The infill pour of the arch ribs was were post-tensioned at the PBM Con Two cranes were used to erect the accomplished using two movable crete plant in Rochelle, Illinois, about arch segments by placing them on the forms attached by J-hooks to epoxy 120 miles ( 194 km) from the con- pier caps and temporary towers at the coated reinforcing steel located in the

September-October 1994 31 arch ribs. Two crews of ten, each as sisted by one crane, worked simulta neously on the infill pour, starting at the base of each arch rib and advanc ing to the crown. Four arch ribs were thus poured and finished concurrently in one day. The contractor worked on the infill pours into the winter months. This ne cessitated using heated concrete for at least two arch spans, pumping heat into the arch cavity, covering with in sulation, and wrapping with blankets. While work on the arch spans pro gressed, the casting of the pretensioned concrete girders had already taken place at Spancrete Industries, Inc., in Waukesha, Wisconsin, not far from the construction site. The specified com pressive strength of the concrete gird Fig. 13. Deck girders were temporarily supported on the arch crown and pier walls, ers varied from 6000 to 7000 psi (4 I to eliminating the need for ground supported shoring. 48 MPa) with a minimum required re lease strength of 5300 psi (37 MPa) for to support the pretensioned concrete erection of the girders, the cross the 7000 psi (48 MPa) girders. girders. The scaffolding supporting beams and deck sections of individual The contractor formed and poured the girders and the forms for the cross spans were poured concurrently. The the spandrel walls between the arches beams were attached to the arch girders were then connected to the in and erected falsework and scaffolding crown and the spandrel walls. After place cross beams.

Fig. 14. Work progressed from east to west- footings and piers, arches, girders and beams, and finally the deck.

32 PCI JOURNAL Fig. 15. Overall view of bridge showing erection of arch ribs.

Fig. 17. The viaduct is a prominent symbol of pride for an entire neighborhood in the location, known as "The Valley." The visual quality of the neighborhood is enhanced by the new structure.

Fig. 16. The viaduct was opened to traffic ahead of schedule on November 13, 1993.

The deck included three cross July 1993 to allow sufficient time for beams in each deck pour, spaced at casting the concrete bridge railing the beginning, middle and end of the with special lighting standards. The deck section. The first beam received structure was officially opened to traf a full dose of retarder because the fic ahead of schedule on November concrete had to remain fluid for at 13 , 1993. Final completion of auxil Fig. 18. The innovative engineering least 3 hours. The central beam re iary works and landscaping was not solutions used for the viaduct ceived a one-half dose of retarder to finished until the summer of 1994. demonstrate that transportation improvements designed for cost provide a l 'h-hour delay in set. The Figs. 16 through 18 show the com sensitive communities can be both third beam, being cast on completion pleted bridge. functional and aesthetically appealing. of the deck, did not require the re tarder. To faci I itate concrete place ment, all three cross beams contained COST OF PROJECT tiona!, less costly hi ghway bridge. The a superplasticizer because of the From the beginning of the project, strutted arch design proved to be an eq heavy reinforcing steel requirements the City of Milwaukee stressed the im uitable compromise that still achieved and post-tensioning ducts located in portance of aesthetics. A structure was the project goal of building an aestheti the confined cross beam forms. called for that would emulate the de cally pleasi ng structure within the allot Construction proceeded smoothly sign of the historic viaduct. However, ted time frame and budget established without any significant delays. The the primary funding agencies had es for the project. contractor completed the deck pours in tablished a budget for a more func- The innovative use of precast con-

September-October 1994 33 crete components and a conventional CONCLUDING REMARKS The innovative solution used for the deck using pretensioned concrete project advances the state-of-the-art in girders shortened the construction pe The new Wisconsin Avenue Viaduct designing transportation improve riod and saved an estimated $2 mil attests to the many advantages of using ments for cost-effective communities lion compared to a similar cast-in precast, prestressed concrete bridge de that also want aesthetically appealing place concrete arch bridge. The actual signs and construction techniques, par infrastructure. The new viaduct shows total cost of the project (which in ticularly in locations subject to extreme that it is possible to replace old facili cluded the demolition of the old differences in temperature. By using ties that have served the public so well viaduct, approach spans, roadway and precast concrete components, bridge for decades without sacrificing our na site work, plus the new bridge) was engineers can create visually appeal tional heritage and appreciation for the $13.8 million. The cost of the bridge ing and structurally efficient designs, beauty of a structural art form. structure itself amounted to $10.3 thus helping the communities they million. Therefore, the unit cost of serve realize both benefits from essen the bridge per deck area came to tial infrastructure. CREDITS 10,300,000/101,076 = $102 per sq ft. A major design feature of the struc ture was the use of precast U-shaped Owner: arch segments that served as load • Jurisdictional Authority: City of PEER RECOGNITION carrying structural members and as Milwaukee, Wisconsin. The Wisconsin Avenue Viaduct self-supporting permanent forms. • Funding Agency: Wisconsin Depart won a Bridge Design Award and the Concrete was placed in the precast ment of Transportation, Waukesha, Harry H. Edwards Industry Advance arch forms to complete the structural Wisconsin. ment Award in the 1994 PCI Design arch ribs. Awards Program. The jury citation Supporting the deck framing only at Engineering Firm: read: "For the innovative dual use of midspan allowed the use of standard • Prime Consultant: CH2M Hill, Inc., precast U-shaped arch segments as pretensioned concrete girders and will Milwaukee, Wisconsin. load-carrying structural elements and facilitate conventional deck replace as self-supporting permanent forms. ment if needed in the future. Because • Subconsultants: This concept reduced concrete weight, interior vertical load-carrying ele -Charles M. Redfield, Consulting decreased falsework requirements, ments were not required, the spandrel Engineer, Mill Valley, California. saved erection time, and cut construc areas look more open and graceful. -Jiri Strasky, Consulting Engineer, tion costs." The use of precast concrete arch seg Mill Valley, California. In addition, the design of the bridge ments minimized the need for ground received an Honor Award in the supported falsework, saving time General Contractor: Lunda Construc American Consulting Engineers Coun and money. tion Company, Black River Falls, cil's (ACEC) 1994 Engineering Excel The cast-in-place joints for all pre Wisconsin. lence A wards competition. cast components were designed to ac The new bridge has been accepted count for structural behavior and Precast Concrete Manufacturers: with enthusiasm by motorists and the changes to the structure during its con • Arch Segments: PBM Concrete, general public. The structure retains struction, allowing continuity rein Inc., Rochelle, Illinois. the aesthetics of the classic arch form forcement to extend through each and is already a focal point and center joint. The result is durable joints that • Girders: Spancrete Industries, Inc., of attention in the City of Milwaukee. will require little future maintenance. Waukesha, Wisconsin.

34 PCI JOURNAL