Design-Build: The Royal Park Temporary Bascule Bridge
by G. Alan Klevens, P.E., Senior Associate and Steven A. Shaup, P.E., Senior Engineer
Lichtenstein Consulting Engineers, Inc.
ASHE Gold Coast Section

In September 1998, the State of Florida issued a Declaration of Emergency that allowed a design-build contract to be issued in January 1999 for the design, construction, three-year maintenance and operation, and removal of a temporary bascule bridge and fixed approach spans to carry four lanes across the Intracoastal Waterway in Palm Beach County, Florida. The aggressive schedule in the scope of work dictated that design and construction were to be completed within 12 months. Lichtenstein Consulting Engineers led the design team for PCL Civil Constructors, Inc., who was low bidder at approximately $10.6 million. Construction featured innovative steel-framed bascule piers and reuse of the existing bascule leafs by floating the leafs into position using barges. The project received a 2001 National Design-Build Award from the Design-Build Institute of America.

Background
The original parallel bridges with rolling lift movable spans connected the City of West Palm Beach and the Town of Palm Beach in Florida and were constructed in 1929 and 1959. During a 1997 routine underwater inspection, extensive marine borer damage was discovered in the timber piles supporting the 1929 structure. The deterioration was so extensive that the Florida Department of Transportation (FDOT) instrumented and load tested the structure. In 1998, measuring permanent deflection at one of the piers of the 1929 structure, FDOT permanently closed the two lanes carried by this bridge. As the newer structure depended on the older structure for its lateral stability, the entire structure was in danger of collapsing. Based on these facts, the State of Florida issued its Declaration and the project was fast-tracked to bid.

Design Features
To complete the project under budget, the design team worked with the Contractor to develop structural systems that would minimize construction time and costs. To minimize construction time, systems were designed to allow simultaneous on-site construction and off-site fabrication. To reduce construction costs by minimizing demolition and disposal costs and maximizing salvage value, steel components were designed that could be reused after removal from the bridge.

For the fixed approach span bents and bascule piers, steel pipe piles were used. The preferred size of the pipe piles was chosen by the Contractor to ensure that the piles had maximum value to them after demolition of the bridge. The pipe piles had great bending strength, so the use of battered piles was avoided, except where the channel was the deepest.

For the fixed approach span superstructure and intermediate bent caps, rolled steel beams were used at most locations. The steel bent caps were designed so that they could later be separated at the field splice and used as construction crane bents on future projects. Sizes were selected that were in the Contractor's inventory or could be easily purchased with no lead time.

Remaining intermediate bent caps were of concrete precast construction, fabricated in two pieces in an off-site casting yard after as-built surveys were taken of the driven piles. The two pieces were placed atop the driven steel piles, grouted to the piles and joined together by a concrete closure pour.

The bascule piers were fabricated as a steel truss system. This system allowed the Contractor to fabricate the system off site while on-site construction proceeded. The steel frame was designed to be used initially during construction as a pile driving template and then in service for the bracing and horizontal load carrying system of the bascule piers. By using the frame as a pile driving template, the contractor ensured that the piles would be driven in the design location, within the tolerances required by the rolling lift bascule spans. The system works by distributing vertical and horizontal loads from the most severely loaded piles to adjacent piles through the bracing system. Component sizes for the bracing and load distribution system, consisting of wide flange steel sections, were selected from the Contractor's inventory or were most readily available and could be easily purchased with no lead time. Using steel-framed bascule piers allowed for a major savings in the demolition cost of the structure.

The flat tread castings for the existing structure were reused; after cleaning, the castings were shop-bolted to a steel wide flange shape to provide strength and properly support the castings within the required mechanical tolerances for flatness. This assembly was brought into the field and bolted to a set of W920 (W36) shapes shop-welded together side by side and positioned on a steel cap plate atop the driven piles. The side by side W920's (W36) provided the field adjustment necessary to position the bascule leafs on the flat tread castings.

Reuse of Existing Bascule Leafs
The existing bascule leafs were moved, one at a time, from their original location into place on the new steel-framed bascule piers by varying the water levels inside the barge compartments and using the tide to raise and lower the leafs. The waterway was closed to boat traffic while the barge was put into position and one leaf was removed from the existing structure. Once done, the barge was towed to a nearby sand bar and boat traffic allowed to resume. The flat tread castings were then removed, sent to the shop for cleaning and bolting to the wide flange shape, and reinstalled on the new bascule piers. The barge with the removed bascule leaf was then towed to the new bascule pier, where it was placed on the reused tread castings. This method of reusing the bascule leafs did not require demolition of the existing concrete counterweights, saving time and cost.

Project Completion
The structure was opened to traffic in January 2000, within the allowable contract time dictated by FDOT. With the milestone bonus achieved, and authorized contract changes because of unforeseen conditions that could not have been assumed at the time of bid, the final contract value was approximately $11.2 million.

The project received the 2001 Design-Build Institute of America National Design-Build Award in the civil, under $15 million category.