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Kingston-Rhinecliff Project On Track

(Continued from page 1)

Before setting new deck panels, old channel shear connectors are burned off, and new headed studs welded in place.

  • neering proposal from the contractor included a change to an Exodermic deck design, which spans supports at up to 9 ft. 9 in. (3 meters), and reduces dead load 40% compared to the current State standard reinforced concrete deck. New York State DOT’s high performance con- crete mix was specified for the rein- forced concrete component of the Exodermic deck. To enhance safety while providing an aesthetically pleasing design, the new fas- cia barriers use a half-section“Jersey” shape, faced with a bright white polymer shell. This 32 inch (813 mm) concrete barrier is topped with a 24 inch (610 mm) railing system, affording stunning views of the Hudson River Valley in both direc- tions. Lightweight concrete is used in the barrier to save additional dead load. As a busy crossing with over 20,000 ADT, the owner required that inconven- ience to the traveling public be mini- mized. A detour of 43 miles (72 km) was considered far too long, and the decision was made to keep both lanes of traffic open during the morning and evening rush hours (and holidays), with a single reversible lane allowable at other times. This decision required that work be accomplished in three stages across the two lane bridge. On the two approaches, the stage line is coincident with the cen- terline of a stringer, but on the truss spans, the stage line splice falls between stringers, and was positioned at roughly the third points between supports. A sim- plified detail was developed using bolted splice plates and lapped reinforcing steel to accommodate this‘mid-air’ splice.

Four finger joints on the truss spans are being replaced with large modular joints, asphaltic plug joints are being used between the approaches and the truss spans, and strip seal joints are specified for the approach viaducts.

American Bridge Manufacturing is providing the grid deck, reinforcing steel, and miscellaneous forms and other materials. The over 330,000 square feet (31,000 square meters) of deck replace- ment began in June of 2000, and is scheduled to be completed this year.

Deck Replacement

With the original deck, put into serv- ice in 1957, the structure had a live load rating of HS-18. The shoulder width was only 3 ft. (914 mm) and the railings were of open steel construction. The new deck needed to provide an HS-25 load rating, a wider shoulder to accom- modate maintenance activities and bicy- cle traffic, and a conventional concrete Jersey barrier. To accommodate the increased live load and dead load, a steel grid deck was chosen as the replace- ment.

This project was originally designed with two alternate, precast deck choices, a half-filled grid and an Exodermic deck. The plans as finally bid and awarded only detailed the half-filled grid design, and changed to cast-in-place, staged construction. Because two lanes of traffic had to be maintained during

peak traffic hours, work had to be divided into three stages. On the 5200 feet (1585 meters) of truss spans, there is no stringer located at the stage line. For the half-filled grid deck specified in the plans, the splices between stages required extensive field welding. As the steel grid was to be hot-dip galvanized, welding would have been particularly difficult and time consuming. Contractor Cianbro Corporation of Pittsfield, Maine became interested in the Exodermic design as an alternative. With the Exodermic design, the splice between stages on the truss spans could be accomplished by lapping rebar and by bolting splice plates across the bottom flanges of the structural T’s being used for the main bars of the grid. Field weld- ing was eliminated.

Cianbro proposed a modified half- filled grid design and the Exodermic design as two possible value-engineering changes. The NYSBA and their consult- ants, Modjeski and Masters and Greenman Pedersen, chose an Exodermic deck because of its greater stiffness and strength compared to the alternate deck type. The proposed Exodermic design was reviewed independently by Lichtenstein Consulting Engineers prior to the project getting underway.

The contractor worked with American Bridge Manufacturing to develop details which allowed reinforc- ing to be pre-cut and tied to the steel

On the 5200’ of truss spans, where the construction joint between stages falls between girders, splice plates are bolted in place and reinforcing steel is lapped.

EXODERMIC BRIDGE DECK, INC. • 60 LONG POND RD, LAKEVILLE, CT 06039 • TEL: 860.435.0300 • FAX: 860.435.4868 • info@exodermic.com

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