HARRY H. EDWARDS AWARD WINNER

Precast Segmental Seismic Retrofit for the San Mateo - Hayward Bridge

James K. Iverson, Ph.D., S.E. The retrofit of the San Mateo - Hayward Bay Project Manager Carter & Burgess, In c. Bridge is part of the California Department of Oakland, Ca liforn ia Transportation's (Ca ltrans) effort to retrofit the toll bridges in the state of California. As part of this program, the use of precast segmental construction techniques in the San Mateo- Hayward Bay Bridge retrofit project resulted in a constructable and durable retrofit for the rectangular foundations. Th e $102 million construction package included the seism ic retrofit of 20 of these rectangular piers. This article provides an overview of the project design Carlos Banchik, P.E. and construction phases. Precasting of the frames Project Manager Carter & Burgess, Inc. was performed on barges that were towed to the Las Vegas, Nevada site and the frames were assembled and placed around the footings. Arms on the frames reached out to 8 to 72ft (2.4 to 3.6 m) diameter piles driven through the bay mud to firmer soils so the system Robert Brantley, P.E. limited the excessive transverse deflections that Structures Group M anage r Carter & Burgess, Inc. would occur in a severe earthquake. Phoeni x, Arizona

he San Mateo - Hayward Bridge across the San Francisco Bay in California is a 7 mile ( 11 .3 km) T long structure heavily uti li zed by local traffic (see Fig. 1). It connects the city of San Mateo on the San Fran­ cisco Penin sula with the city of Hayward in the East Bay area. The structure consists of three sections, i.e., a 400 ft (122 m) concrete approach structure on the west end, a 2 mile (3.2 km) long main span structure that spans the John Sage, P.E. shipping channel, and a 5 mile (8.1 km) long concrete tres­ Plant Manager tle structure that ties to the east bank of the bay. The bridge Pomeroy Corporation structures were reviewed in 1993 and fou nd to require Peta luma, Ca lifornia retrofit for safety against collapse in a major earthquake.

28 PCI JOURNAL Fig. 1. Panoramic view of th e San Mateo-Hayward Bridge.

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RETROFIT REFERENCE NUMBERS 1 - Bearing reinforcement 5 -Steel plate reinforcement of steel columns 2 -Concrete encasement of spandrel and spandrels 3 - Concrete encasement of column 6 - Reinforcement of stee l column bearings 4 - Concrete overlay and encasement frames 7- Steel encasement of base of bell foundations and steel piles at concrete footings and concrete stubs at Piers 19 and 20

Fi g. 2. Various pi er types of main span bridge.

November-December 1999 29 w 0

\ To San Mateo

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0 10 16 20 36 40 46 60 66 80 86 70 76 80 Fiahing pier

Begin Construction State Route 92 STA 4+ 23.31 End Construction ST A 97+ 01.61

PLAN

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0 HINGE RETROFIT

~ 0 c ELEVATION JJ z 'f::. Fi g. 3. Plan and elevation of main span bridge. CIDH PILE 0 PIERS 2 AND .3 CISS PILE (TYP.) •c• LINE

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PLAN ,.., TYPICAL PRECAST FRAME

•c• LINE 42'-7"± l 42'-7"±

2'-7"± 18'-0"±

,-t----UPPER CONCRETE SPANDREL BEAM RETROFIT

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TYPICAL TRANSVERSE SECTION

Fi g. 4. Typica l rectangular foundation retrofit plan and elevation.

November-December 1999 31 The structure is located almost mid­ with an orthotropic deck and is be­ perstructure. A typical pier and deck way between the San Andreas and lieved to be the first bridge with twin section along with the typical retrofit Hayward Faults, both of which are steel box girders constructed in Cali­ are shown in Fig. 4. only a few miles away. The retrofit fornia, if not the entire Unites States. In deeper waters exceeding 25 ft design project for the approach and At the time of its construction in 1967, (7 .6 m), precast bell foundation sub­ main spans was advertised by the state the 750 ft (228 m) shipping channel structure units were used, which are of California in 1995, along with sev­ span was the longest span for a super­ shown in Fig. 2. These units were eral other bridge retrofits in the major structure with an orthotropic deck. composed of precast concrete parts. A traffic areas of the state. Carter and There are different types of sub­ precast flatplate template was placed Burgess and its design team were cho­ structures supporting the superstruc­ on driven timber piles on the bay floor sen by the California Department of ture and these are outlined in Fig. 2. that had precast holes delineating the Transportation (Caltrans) to perform The type of substructure used de­ pile pattern to be used. Depending on the retrofit design for the approach pended on the depth of the bay water the location, up to 120 steel H piles and main span portions of the struc­ at each pier location. For water depths were driven through the template and ture. The state of California performed up to about 25 ft (7.6 m), conventional left with about a 12 ft (3.6 m) exten­ the design of the trestle retrofit and rectangular reinforced concrete foun­ sion above the template. construction has been completed on dations were used. These were de­ Next, a circular, hollow precast bell­ both the trestle and approach projects. signed as a pile cap for up to 84 steel shaped section was placed over the The 2 mile (3.2 km) long main span H piles, which were typically 14 BP pile extensions and onto the template. structure of the bridge consists of 37 88 sections. Each pier had two of these founda­ spans of steel box girder construction The H piles were driven through the tions, which were linked with a pre­ with spans varying from 208 to 750 ft very soft bay mud in the upper layer cast strut that aligned the two bells (63 to 228 m) in length, with the of soil and into deeper firm stratums. during placement. The two piers at the longest span over the shipping lane. A Driven lengths of up to approximately channel span had four similar bells. plan and elevation of the main span 200 ft (61 m) were used. The tops of Then, a precast circular column was are shown in Fig. 3. The western ap­ the H piles were embedded 6 in. (150 placed on each bell and these were proach structure consists of four spans mm) into the rectangular foundations. linked at the top with a precast span­ of concrete construction and the east­ Rectangular concrete towers con­ drel. The bells and columns were then ern approach, or trestle structure, is nected by concrete cast-in-place span­ filled with concrete. composed of precast piles and deck drels, in either a portal frame configu­ The precast components incorpo­ members with standard spans of 30 ft ration (single spandrel beam) or a rated water seals, which enabled the (9.14 m). Gerber frame configuration (dual concreting to be performed in a dewa­ The main span superstructure con­ spandrel beams), extend from the rect­ tered condition. A rectangular steel sists of twin welded steel box girders angular foundations to the bridge su- column section was placed on the top of each column and these were joined by steel spandrels at the bottom of the superstructure. 6'-0" The retrofit of the main span and ap­ proach was bid in two construction GROUT PRIOR TO LOWERING -i\ 0 packages. Package 1 consisted of the FRAME IN SERVICE POSITION · I \ ! approach structure and the abutment of the approach and main span, which NEW ~ -r-PIN was a building with paint and mainte­ PRECAST iii HOLDER J nance shops and offices in it. Package FRAME :~: Ol i .. i :J1r--NEOPRENE PAD 2, the subject of this article, consisted ~ 5'-2,. X lQ'-0,. 'f of the main span portion of the bridge . ...---->-r_="iJii~~.: i = ~ N These two projects were the first of r; =:: = F' !-----' = :. :11£-==::;;;j;.-{1------ol,. the San Francisco Bay Toll Bridge _j :=:~::= _j seismic retrofits, mentioned earlier, to LL ow begin construction. _I t:J The 28-month design phase of the (j')(r ~u project incorporated several mile­ z I "~" I :::GE CI~I~HOR 0 stones. Preliminary performance crite­ u ~ f- ANCHOR PILE ria were developed initially and analy­ RODS sis and design methods were proposed and carefully evaluated by Caltrans and its "Peer Review" consultants. Vulnerabilities were identified and Fig. 5. Typical section showing precast frame to pile connection. mitigation measures proposed.

32 PCI JOURNAL Each mitigating measure was evalu­ ated not only for seismic perfor­ TRANSFER BEAM---"'"" mance, but for constructability and maintainability as well. Then, the 8" DRILL AND BOND ------.._ PRECAST A 6\7" AS SHOWN TOTAL PRESTRESSED final design proceeded. There were 21 IN 2'-0" DEEP HOLE • CONCRETE major design reviews during the 617 FOUNDATION GIRD ER progress of the work and final 100 t! percent document sets were produced. The seismic analysis of the struc­ tural models subjected the bridge to magnitude eight earthquakes from the adjacent faults. The design was based on multiple support time histories de­ veloped specifically for the project. Several sei smic vulnerabilities were identified by the structural modeling of the bridge and by the detailed anal­ ysis of the individual members. Retrofits were chosen to reliably and economically address each vulnera­ bility. The following sections detail PARTIAL PLAN - PRECAST PRESTRESSED the use of precast concrete encase­ CONCRETE FOUNDATION FRAME ment frames and large diameter steel pipe piles to mitigate the seismic vul­ nerability of the rectangular founda­ tions due to large seismic demand ... displacements. I ~+--~-...::..--==ii=r ------11---·-+..,

DESIGN OF THE 8" DRILL AND BOND --+--­ A 6\7" AS SHOWN TOTAL PRECAST FRAMES 21 IN 2' -0" DEEP HOLE

This section presents information on NEW CONCRETE ---.__._NEOPRENE OVERLAY drift control, overturning precautions, BUMPER PAD and the strengthening of the existing foundation of the San Mateo - Hayward ~~~· ~~iiu·~ D___._-~ ...,_---"'..!"-! Bridge. FOUNDATION FRAME FOUNDATION

Drift Control EXISTING CONCRETE SEAL As the analysis of the project devel­ SECTION A-A oped, it became clear that a major problem was "drift" - longitudinal Fi g. 6. Plan details for grout bag load points. and transverse horizontal displace­ ments of the 20 rectangular founda­ tions due to the large dynamic mass isting pile groups Jacked the ductility Caltrans to the designers to verify pil­ introduced into the system by the rect­ to accommodate· the calculated de­ ing directions and the level of accu­ angular foundations. These excessive mand drifts and they did not have suf­ racy used in the driving operations. drifts could lead to local buckling of ficient tension capacity to resist the The retrofit scheme that was finally the steel H piles used at these founda­ calculated overturning moments acting developed utilized large diameter steel tions and potential collapse of the at these foundations. pipe piles to control the drift. These structure. Several pile types and linking sys­ steel piles were 8 to 12 ft (2.4 to 3.6 As mentioned previously and shown tems to decrease the foundation drifts m) in diameter, with wall thicknesses in Fig. 4, a large number of driven were investigated and constructability of 1.5 to 2.25 in. (38 to 57 mm). steel H piles were used under the rect­ became a major issue. The existing Lengths from about 130 to 170 ft (39 angular foundations and the piles were outer piles were battered, complicating to 52 m) were required to reach into developed only 6 in. (150 mm) into locating the additional new piles nec­ the firmer soils underlying the soft the existing foundation. This connec­ essary to solve the problem. Any con­ surface bay mud. tion provided compressive load capac­ structable design had to avoid interfer­ All work on the placement of the ity, but the tension capacity was very ing with these existing piles. Original frames was over water and was to be limited. Analysis indicated that the ex- pile driving records were furnished by performed from barges. Additionally,

November-December 1999 33 there were low clearances from the ends of the arms on the frame, large tion and 2000 kips (8900 kN) of verti­ water to the deck above and extremely steel pins extend into the top portion of cal uplift. large piles were involved. As the work the piles. This top portion is later Several measures were incorporated progressed, it became clear that the grouted to tie the piles to the precast in the design to account for the under­ piles had to be driven in one piece, frames, as shown in Fig. 5. water marine environment surround­ without field splices, if they were to The lower portions of the piles were ing the precast frames and piles. Meet­ be economically feasible. left filled with the soil they were ings with Caltrans Materials Division The result was the use of a pre­ driven into because the primary func­ personnel resulted in valuable durabil­ stressed concrete frame encasing the tions of the piles are to resist horizon­ ity guidelines that were incorporated footing with four outrigger beams tal motions and overturning tension into the project. Type II concrete with reaching out to allow the large piles to forces. The pins provide a tie for ten­ fly ash and a compressive strength of be located outside the existing over­ sion resistance from the large piles as 6000 psi (41.3 MPa) was utilized. head deck and, thus, allowing them to well as the primary horizontal drift re­ A 706 reinforcing bars with a yield be driven in one piece. A plan and sec­ sistance. As the design evolved and strength of 60,000 psi (413 MPa) and tion of the frame is shown in Fig. 4. the final analysis iterations were com­ a typical concrete cover of 5 in. ( 125 The longitudinal beams were de­ pleted, forces transmitted to the large mm) were provided. signed with inner polystyrene box sec­ piles reached values, depending on the All the reinforcing bars were epoxy­ tions along their central portion to min­ pier location, of up to 760 kips (3380 coated. Also, all miscellaneous steel imize the weight of the frames and kN) in the longitudinal direction, 1850 was hot-dipped galvanized. High reduce their seismic reaction. At the kips (8230 kN) in the transverse direc- strength bars and post-tensioning strands were carefully grouted. For the large diameter steel piles, which would be entirely submerged, an addi­ tional sacrificial thickness was added to the required structural steel wall thickness for corrosion protection. The reinforced concrete frames are precast to minimize costs and built in two segments to allow fitting around the existing pier structure. The two halves are assembled on separate barges above the water and moved into position around their pier. Con­ crete splices are formed and poured in the transverse frame members. Time is allowed for the concrete to achieve ad­ equate strength, and the transverse tie Fig . 7. beams are post-tensioned. Mockup of grout bag. The completed frame is lifted off the barges, which are removed, and then the pins and their encasement reinforcing cage are placed and the completed frame is lowered into place around the foundation. A 3 in. (75 mm) clear area between the frame and the foundation was used to accommodate existing foundation irregularities. The connection between the existing foundation and the precast frames oc­ curs at eight places at the inside cor­ ners of the precast frame. Grout bags were used to provide these horizontal load points between the frame and foundation. Fig. 6 shows the typical plan details for the grout bags. To en­ sure the quality of the completed grout bag assembly, a sample was tested Fig. 8. Typical cofferdam installation. using an underwater mockup.

34 PCI JOURNAL Fig. 9. Precast frame showing completed reinforcing ba r cage.

The test demonstrated that the grout Strengthening of struction and erection of the precast bag could be fi lled effectively and that Existing Foundation frames. the resulting assembly was functional. Analysis of the foundation demon­ Fig. 7 shows the grout bag after the strated that the joints at the foundation Bid and Award Process mockup test was completed. Several and towers were inadequate for the After the technical design and docu­ sample cores were taken from grout in level of stresses induced by maximum ment reviews were completed and all the bag to ensure the quality of the op­ horizontal and vertical movements, regulatory and environmental concerns eration; the holes from these samples even with the frame and piles in place. were addressed, Caltrans conducted a can be seen in Fig. 7. This problem was solved by providing public bid opening on November 4, a reinforced 3 ft (1 m) concrete over­ 1997. The low bidder was a Joint Ven­ Overturning Precautions lay on each rectangular foundation. ture of Morrison Knudsen, Traylor The vertical uplift motions of the Fig. 4 shows a typical overlay. Brothers and Weeks Marine and they foundations are also limited by the To construct the concrete overlays, were awarded the project for their low precast frames. The uplift forces are the contractor utilized reusable coffer­ bid of $102,436,000. Construction transferred by means of short diagonal dams prefabricated from steel sheet started soon afterwards. transfer beams located on top of the piles supported against the existing Imbsen and Associates, Sacramento, frame at the corners, as shown in Fig. foundations with steel braces placed California, provided engineering for 4. The short beams straddle over the over the top of the existing concrete the construction team. Design checks corners of the existing foundation and foundations. Rubber seals were used were performed by the designers and a horizontal neoprene pad is attached at the interface between the cofferdam verified the feasibility of the construc­ to the underside of the transfer beam section and existing foundation to tion systems proposed. at the design bearing point to ensure limit the bay water intrusion. The Pomeroy Corporation contracted to loading at the proper location. pressure of the water keeps the assem­ supply the precast frame segments. Note that there is a 2 in. (50 mm) bly compressed against the existing Pomeroy' s $9,000,000 scope of work gap between the neoprene pad and the foundation. A typical installation is consisted of the fabrication and deliv­ top of the concrete overlay. This gap shown in Fig. 8. ery of the 40 precast concrete frame allows the existing fo undation to de­ halves. The fabrication of these pieces, velop a portion of its capacity before CONSTRUCTION OF with weights up to 525 tons (4 75 t), relying on the strength of the precast required careful planning. frames to transfer the remainder of the THE PRECAST FRAMES Pomeroy's plant, located in Petaluma, overturning tensile forces to the large This sections addresses the bid and California, north of the San Francisco diameter steel piles. award process as well as the con- Bay on a navigable river, provided the

November-December 1999 35 ideal site for manufacturing the large precast concrete frames. The availabil­ ity of a large capacity gantry at the for­ mer Hunter's Point Naval Shipyard meant that the frames could be trans­ ferred from the casting plant to erection barges. The operation also allowed some separation of the casting and erec­ tion activities.

Construction of the Frames Pomeroy chose to cast the frames di­ rectly on their delivery barges to mini­ mize handling of the heavy precast concrete components. Three 34 x 110 ft (10.3 x 33.5 m) barges were outfitted with steel and plywood casting soffits. Wells were cut into the decks of the barges to allow the pinholder to pro­ trude from the underside of the frame. The unusually heavy pipe required for the pins and pinholders to transfer loads between the precast frames and the large diameter caissons was spe­ cially fabricated in Germany. The epoxy-coated reinforcing bar cages were assembled on land in specially built jigs, as shown in Fig. 9. Custom forms, manufactured by Helser Industries in Tualatin, Oregon, allowed the geometry to be modified so that all three different types of con­ crete frames could be cast using only one set of forms. Fig. 10 shows the set­ ting of the preassembled reinforcement on the barge form . Fig. 11 shows the completion of casting of a segment. Fi g. 10. Precast frame showing lowering of reinforcing bar cage onto casting barge. Fig. 12 shows a completed half frame ready for shipment. Production was done in a barge slip, which allowed overhead access for a 110 ton (100 t) capacity travelift. The travelift was used for picking and set­ ting the reinforcing cages, embedded components and steel forms. This op­ eration is shown Figs. 10 and 11. Finished precast halves were cured and temporarily stored on the casting barge until concrete strengths were ad­ equate for erection. The production and erection schedules had to be very closely matched due to the inability to store the finished precast components. Frames had to be cast, delivered and erected at the same rate. Work on ad­ ditional frames could not begin until casting barges were available. A mockup of the closure pour zone used to link two frame halves together Fig . 11 . Precast frame with completion of concrete placement.

36 PCI JOURNAL around an existing pier was made. It each frame must match meant that un­ final design. Early concrete strengths clearly showed that with 72 #II splice usually tight tolerances had to be required for picking and handling had bars, there was a problem with con­ maintained. to be balanced against excessive inter­ gestion in the formwork. This led to Pomeroy also assembled a full-sized nal heat of hydration. The chosen mix the decision to double the amount of mockup of the reinforcing cage re­ contained 71f2 sacks of Type II cement post-tensioning and halve the number quired for the work and this was care­ with a 20 percent fly ash substitution. of reinforcing bars through the closure fully reviewed before the actual Heavy reinforcement, much of it pour for ease of construction. The re­ epoxy-coated reinforcing steel was #11 reinforcing bars with complex ge­ quirement that the protruding reinforc­ fabricated. The concrete mix design ometries, made handling difficult. As­ ing bars in the two closure zones of also required trials to determine the sembling the reinforcing bar cage, in­ cluding the expanded polystyrene inner box section along the side beams, required one week. The com­ pleted cage, 110 ft (33.5 m) long and weighing 120,000 lbs (54 t), was then moved using a travelift onto the cast­ ing soffit on the barge. Triangular spreader frames at each end of the cage with nylon slings were used to support the flexible cage. The forms were then closed around the cage and post-tensioning anchors were added. Each half frame was then cast using a pump truck to supply the 225 3 cu yds (214 m ) of concrete required Fig. 12. Precast frame being readied for shipment. over approximately five hours. Upon setup and adequate curing, the form stripping took place. Each precast con­ crete half frame was completed in about one week.

Erection of the Precast Frames Once two halves were ready, they were shipped 50 miles (80 km) south to Hunter's Point Naval Shipyard, south of San Francisco. At Hunter's Point, the giant gantry shown in Fig. 13 lifted the halves from Pomeroy's barges to erection barges specially built for this project. The U-shaped erection barges have two movable link beams between the two hulls to support the half frames and allow them to be slid into their final position. These link beams are shown in Fig. 14 under the precast frame halves. From Hunter's Point, the half frames were moved to the site, placed around their pier, and readied for splicing. The erection barges, with one matching half frame on each hull, were winched in around a pier, care­ fully located, and anchored with spud piles. Link beams were s lid into place spanning between the hulls to support the frames. The Fi g. 13. Transferring frame segment from casting barge to erection barge with frames, resting on Teflon pads cast test bags . into the bottom of the halves, were

November-December 1999 37 then jacked together into position for the closure pour. Figs. 15 and 16 show this work in progress. NMB grouted couplers were used to splice the longitudinal reinforcing bars in the closure pour and conduits for post-tensioning were placed prior to casting. A closure pour void ready for casting is shown in Fig. 17. The hoisting of each precast con­ crete frame [weighing about 1000 tons (906 t)]was provided by a specially designed set of columns and beams, placed next to the steel jacketed tow­ Fig. 14. ers and supported on top of the newly Matching frame placed concrete overlay, cast over the segments mounted existing foundation. Four PSC multi­ on erection barge. strand jacks were used to lift the frame off the barge and subsequently lower it after removal of the barge. Fig. 18 shows the special jacks sup­ porting the frame that has been lifted into the air with the erection barges re­ moved. The pins and their cages are then placed, as seen in Fig. 19, before the frame is lowered into its final posi­ tion, as shown in Fig. 20. Tremie con­ crete was used to fill the top portion of the steel piles and, thus, make the final connection between the frame and piles. The placing, splicing and lower­ ing of the precast concrete frames took approximately five days, unless in­ Fig. 15. clement weather prevailed. Positioning erection barges around a pier. CONCLUDING REMARKS The seismic retrofit of the San Mateo - Hayward Bridge has proven to be a challenging project. The design and construction of the project were closely linked. The project is midway through construction at this time. Minor construction problems have been encountered, but so far no major problems have arisen. All of the large diameter piles have been driven with­ out encountering any of the existing battered piles. The use of precast concrete encase­ ment frames and large steel piles to retrofit the rectangular foundations has proven to be an advantageous con­ structable option. This desirable pro­ ject outcome is the product of the care and attention to details exhibited by all Fi g. 16. Beams in place to pull segment to final position for closure pour. of the project participants.

38 PCI JOURNAL Fig . 19. Placing joining pin and Fig. 17. Closure pour void ready for casting. reinforcing cage.

Fig. 18. Precast frame lifted and erection barges removed. Fi g. 20. Precast frame being lowered into final position.

The innovative use of precast/pre­ ACKNOWLEDGMENT deck girders and the steel towers stressed concrete in this project was and steel spandrel section of the The design team assembled by Carter recognized with the conferment of the deep-water piers. and Burgess for this project included Harry H. Edwards Industry Advance­ several specialty subconsultants: • URS Greiner reviewed and designed ment Award in the 1999 PCI Design • Carter and Burgess performed the retrofit for the bell foundations Awards Program. In honoring the San project oversight and direction, and performed an independent Mateo - Hayward Bridge project, the and dealt with the design of the check of other designs. awards jury stated: retrofit of the concrete portions of • ICF Kaiser studied the structure "This bridge uses an innovative the piers on rectangular founda­ with a detailed dynamic analysis approach to solve a complex tions, the bridge bearings, inde­ of a bridge structural model com­ problem. It is commendable be­ pendent design check of the steel prising over 2000 elements that cause of its importance for under­ towers and spandrels and coordi­ incorporated all significant non­ water applications. Even with nation of final documents for the linearities. some very large precast elements, entire design. • Anatech, a second analysis firm , the formwork was kept fairly sim­ • Modjesky and Masters performed performed an independent check of ple. The way the load is supported design of the retrofit for the steel the results produced by the design is quite unique. It is an extremely portions of the superstructure and model and performed other analysis clever and elegant solution." substructure, including the steel reviews.

November-December 1999 39 • Athalye Consulting Engineers de­ tion of the specifications was accom­ CREDITS signed the concrete approach span, plished by Todd Goolkasian of Biggs Owner: Department of Transportation, the west abutment, and the main and Cardosa Associates. State of California, Sacramento, span-east approach abutment struc­ Several other consultants con­ California ture (Pier 38), which was part of the tributed to the project development. main span contract. Dr. Nigel Priestley of SEQAD Con­ Engineer: Carter and Burgess, Oak­ • Geomatrix Consultants provided sulting, Dr. A. Astaneh-Asl of the land, California geotechnical consulting, soils analy­ University of California, Dr. Wen General Contractor: Morrison Knud­ sis and modeling. Tseng of International Civil Engi­ senffraylor Brothers/Weeks Marine, John Knudsen and Associates and neering Consultants, George Fotinos A Joint Venture, Foster City, Cali­ Faye Bernstein and Associates pro­ of Ben Gerwick, Inc. and Dr. Yan fornia vided an independent check of the cal­ Xiao of the University of California culations and other design and drafting made up this group, which provided Precast Concrete Manufacturer: assistance. Knudsen also provided pre­ specialized assistance throughout the Pomeroy Corporation, Petaluma, liminary specifications. The finaliza- project. California.

40 PCI JOURNAL