Prize Bridge Award:Grade Seperation MARITIME OFF-RAMP he 2,356’ long "Maritime Off- Ramp” is one of seven bridge Tcontracts in ’s I-880 Replacement Project. The Maritime Off-Ramp replaced a concrete struc- ture on Cypress Street (now named the Nelson Mandela Parkway) in Oakland. The “Maritime Off-Ramp,” also known as the Horseshoe Line or “HS” Line because of its 250’ radius horseshoe shape, is an orthotropic steel bridge. The remainder of the bridges in the project are steel plate girder bridges with concrete decks or post-tensioned cast-in-place con- crete. The “HS” Line becomes California’s sixth orthotropic bridge.Loma Prieta Earthquake On October 17, 1989, the Loma Prieta earthquake (magnitude 7.1) occurred near Oakland and , California. The I-880 Cypress Street Viaduct, a two-level reinforced concrete structure com- pleted in 1957 carried I-880 freeway traffic through . The upper roadway collapsed result- ing in 41 deaths and 108 injuries. A portion of the roadway between 7th and 34th streets was removed due to the damage. I-880 is a critical interstate free- way connecting San Jose and the East Bay Area to San Francisco, Sacramento and the Sierra Nevada. The I-880 Freeway Viaduct was a section of I-880 that carried between 140,000 and 160,000 vehicles per day and provided for eight lanes of mixed-flow traffic.

THE I-880 REPLACEMENT PROJECT The I-880 Replacement Project was designed and then built in seven separate construction contracts to avoid impacting traffic in this impor- tant transportation corridor. “The Maritime Off-Ramp” is a new unique curved steel orthotropic bridge that provides access to the through a U-turn from Westbound I-80. The project’s $1.1 billion budget, consisting mainly of federal emer- gency relief funds from FEMA, is divided into approximately $650 mil- lion for construction and $350 mil- lion for right-of-way acquisition, rail-

Modern Steel Construction / September 1998 road and utility reloca- tion, traffic manage- ment, transit enhance- ment, and a number of commitments to the City of Oakland. An orthotropic steel bridge with trapezoidal ribs was selected to cross over th busy I-80 freeway to minimize travel delays or lane closures during bridge erection to commuters and highway traffic. The bridge utilized reinforced concrete “T” bents with a single col- umn with spiral rein- forcing ties. Two special bearings connect the superstructure to each “T” bent. A new joint shear criteria for rein- forced concrete design was first used on the project. The level of reinforcement in the design was higher than previous projects.

SPECIAL ISSUES Some of the details used on the “HS” Line were first utilized on the Golden Gate Bridge. Caltrans pro- vided technical assistance and con- struction inspection to the Golden Gate Toll Bridge Authority for the replacement of the original rein- forced concrete deck with an orthotropic steel deck in 1984. Many welding details for the trapezoidal rib were repeated for the “HS” Line. The transverse flexural stiffness of the orthotropic steel deck is critical for the long-term behavior of the asphaltic overlay. The weight-saving concerns, which guide the seismic cal optimization study. The need for details were developed to reduce the design, dictate minimal overlay pile compliance at the interface of number of locations where opposite thickness. This leads to a compliant soft mud with the stiff underlayment face welding would occur since lami- deck system that is very sensitive to leads to steel piles. The deep overly- nar tearing could result. The trape- temperature and to local deflections ing mud layer requires very long zoidal rib is the most popular system imposed by concentrated wheel piles because of the high seismic used in about 95 percent of all loads. The cyclic nature of this load- loads. Cost is reduced by minimizing orthotropic deck bridges built world- ing only increases the problem of the number of steel piles while keep- wide. The ribs were fabricated in compliance between overlay and ing the pile cap at a reasonable size. tangent chords to accommodate the steel underlayment. The long-term Also, the need for pile ductility and sharp radius of the superstructure. delamination danger of the overlay elastic pile cap behavior dictates the It was unfeasible to form the rib sec- is greatly reduced by providing a use of 42” diameter pile with the pile tions in the same curved configura- uniform stiffening pattern with rela- cap dimensions chosen. The hexago- tion of the bridge. The ribs were tively closely spaced components and nal pile cap shape results from the therefore welded as tangent chords a relatively stiff top deck plate. “isotropic” nature of the seismic to the top deck plate to approximate loading imparted by the soil struc- the radius of the girders. FOUNDATION DESIGN ture interaction with the “plastic An important detail of the The hexagonal foundations with hinge” load reaction at the pier base. orthotropic design is the welding of the seven, “medium size” 42” diame- No welds were allowed to cross the closed rib stiffener to the top ter, steel piles were the result of a over another weld and plates were deck plate. The specifications structural geotechnical and economi- coped to avoid the occurrence. The required this to be an 80 percent included in the design to allow the fabrication of the girders in the smallest sections possible. The large size and weight of indi- vidual girder components created some difficult handling and fitup problems. This was further compli- cated due to the curved configura- tion of the girders. The top deck plates with the welded rib sections proved difficult to handle. Once all sub-assemblies were fitted together, most welding was required to be per- formed in the vertical and overhead positions within the closed box sec- tions. The girder sections were too large to turn to allow welding in the optimum flat and horizontal welding positions. The contractor fabricated 13 full bridge-width orthotropic sections 7’- 0” deep by 35’-6” to 37’-6” wide, with lengths varying from 123’ to 219’ per section. The sections ranged in partial penetration groove weld. To ed bridge sections. The rubber delta weight from 250 tons to a maximum ensure that welding would be of the shaped “dock fenders” were used to of 459 tons. All sections were highest quality, the specifications absorb kinetic energy occurring dur- shipped with a steel orthotropic deck required that the rib welds be made ing a seismic event at the hinges in and with the installed steel barrier using the automatic submerged arc the superstructure. Rubber fenders rails. The total weight of all fabricat- process. Deck plates were oriented were used as bumpers to reduce ed steel equaled 5014 tons. so the grain or rolling direction of forces transmitted in a compression ERECTION PROCESS the steel plates was centered on the shock wave in the longitudinal axis longitudinal axis of the bridge. of the bridge. A creative solution for the instal- To maximize fatigue life and Larger delta shaped rubber fend- lation was conceived by the erector avoid Category “E” details, intersec- ers were used as part of cable that utilized “SHLHP” (Special tion of rib welds at their juncture restrainer system when the seismic Heavy-Lift Hydraulic Platform) with the diaphragm welds were forces would try to pull apart the which consists of two self-propelled avoided by large copes at the weld bridge segments at the two hinge hydraulic platforms braced in tan- intersections. These copes were sections. The lower mass of the steel dem with a strut beam. They had sealed by injecting polystyrene foam orthotropic superstructure plus the the capacity to build the 13 full into the rib compartment to prevent energy damping system reduce seis- bridge- width (35.5’) sections as one entrance of moisture or other corro- mic forces on the concrete columns welded unit. sion contaminants. An orthotropic and substructure. A 20-line, two-file Scheuerle steel barrier system using structural PTFE (poly-tetra-fluoro-ethyl- hydraulic trailer with a custom- steel fabricated in the approved ene) spherical bearings were used to designed spacer frame was used to FHWA barrier configuration was allow for rotation and expansion of off-load the girders at Oakland. The designed. To reduce deadload and members. These bearings can resist frame between the axles distributed simplify composite action welded higher lateral forces including seis- the load over a wider path to meet steel was selected. The system was mic forces. A central shear key pipe structural requirements on the dock. designed to be higher because of the was added for additional lateral The girders were set on temporary heavy truck traffic using the sharp capacity. cribbing in the staging area. The off- horseshoe bend on I-80 traffic. The load sequence and staging locations barrier was fabricated in 20’ long FABRICATION OF ORTHOTROPIC required careful planning since the components that bolt to an internal BRIDGE SECTIONS girders could not pass each other in “W” flange system welded to the The unusually large dimensions the staging area once they were off- orthotropic superstructure. A series and weight of the orthotropic box loaded. Therefore each section was of access panels on the exterior allow girders would limit their fabrication moved three times: first from the the removal of damaged barrier to only the largest fabricators. fabrication facility to the barge, sec- after a vehicle collision. Consequently, Caltrans directed the ond from the barge to the staging consulting engineers to provide area beside the I-80 freeway and SEISMIC DETAILING FEATURES detailing to allow for flexible section finally erected. Each section was The bridge has several unique size. A minimum and maximum sec- step jacked to a height on cribbing seismic detailing features including tion piece size was specified with very close to final bridge elevation. the use of rubber dock fenders as optional or variable splice locations. Closure of I-80 adjacent to the seismic shock absorbers reducing Both transverse and longitudinal Toll Plaza for the San Francisco- transmission force between complet- bolted splice alternatives were Oakland Bay Bridge was required for setting of the three of the 13 sec-

Modern Steel Construction / September 1998 tions. The sections were staged on the east side of the freeway and Maritime crossed over during night erection. Off-Ramp This could only take place in a ten- Owner: hour window beginning at midnight California Department of on a Saturday night. A stiff financial Transportation fine was stipulated for each minute exceeding this time limit by the con- Designer: tractor. The first section was erected Tudor Engineering, at the west abutment and allowed Oakland, CA the team to practice for the erection over the freeway. Consulting Firm: The five mile freeway link, con- ICF Kaiser Engineering Inc., necting the Nimitz Freeway directly Oakland, CA to the Bay Bridge Toll Plaza, opened for business by 5 a.m. Wednesday, General Contractor: July 23, 1997, in time to ease the Kiewit-Marmolejo (joint venture) pressure of the morning commute. Vancouver, WA The section of freeway opening Wednesday was only the first link of Detailer: the I-880 Replacement Project. Candraft Detailing, Inc., Port When completed, the freeway sec- Coquitlam, BC, Canada tion is expected to carry 118,000 cars a day. Fabricator: Universal Structural Inc., Vancouver, WA (NSBA Member)

Erector: Shaughnessy & Company, Auburn, WA