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.
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