A new accelerated bridge construction solution

makes its commercial debut in a statewide

bridge replacement project in Pennsylvania.

A NEW TAKE
on Plate Girders BY TOM STOCKHAUSEN

THE PENNSYLVANIA Rapid Bridge Replacement Project (PRBRP) is

Tom Stockhausen ambitious in scope, to say the least.
(thomas.stockhausen The project involves replacing 558 structurally deficient bridges over
@cdrmaguire.com) a three-year span, and the majority of the bridges in the project are short
is president of CDR spans proposed to be replaced with concrete structures. Approximately
Bridge Systems, LLC. 10% of the bridges restricted the general contractor (Walsh/Granite) to a
five-week maximum detour, thereby necessitating accelerated bridge con-
struction (ABC).
As an alternative to concrete, general contractor Walsh/Granite
turned to the folded steel plate girder (FSPG) system for multiple re-
stricted-detour bridge projects under the PRBRP. FSPG bridges were
first constructed as demonstration projects in Massachusetts and Ne-
braska using Accelerated Innovation Deployment Grants from the Fed-
eral Highway Administration (FHWA). When compared to concrete,
they can be erected faster, last longer, require roughly the same level of

JANUARY 2017
 Installing the first section. The folded steel plate girders are fabricated from a single steel plate of uniform thickness that
is bent along multiple lines using a hydraulic metal press brake, forming a trapezoidal-shaped
section that is open at the bottom

maintenance and compete in terms of cost. As of publication, tour time frame by more than 50% as well as accelerated design
four of the seven bridges ordered by Walsh/Granite have been and manufacturing. An added benefit was the improved quality
manufactured and two have been erected. The three others of the deck concrete because it was constructed in a controlled
are currently being manufactured. environment.
The ability to standardize the FSPG process is part of what
Concurrent Construction significantly reduced the design and manufacturing time. With
Conventional construction of a typical precast 60-ft bridge 11 standard sizes, design basically involves selecting the appro-
was estimated by Walsh/Granite to take about 11 weeks fol- priate size girder for the span length and opening, then detail-
lowing design and manufacturing of the bridge beams. In many ing the horizontal and vertical geometry of the specified deck.
rural areas where detours are quite lengthy, the 11-week detour This allowed superstructure design for the Pennsylvania proj-
placed a severe impact on local residents, in particular emer- ects to be accomplished in a matter of days.
gency vehicles and school buses. However, the FSPG solution CDR Bridge, which designs and manufactures the FSPG
moved much of the construction process off-site, where it was system, was also able to reduce total production time for the
performed concurrently with demolition of the old bridge and Pennsylvania bridges to as little as 14 weeks, including steel
construction of new abutments—which reduced the typical de- procurement. Manufacturing took place in three steps: forming

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 Installing the third section.
the steel, galvanizing it and then precasting the deck
panels. For this project, the girders were formed by
Folded Steel Plate Girders cold bending ½-in. plate steel. Shear studs, sole plates
What is a folded steel plate girder (FSPG)? and bearing stiffeners were welded and flange separa-
Developed at the University of Nebraska-Lincoln, the girders tors were bolted to complete the first step. The steel
are fabricated from a single steel plate of uniform thickness that fabrication process took less than three weeks for four
is bent along multiple lines using a hydraulic metal press brake, girders of a typical two-lane bridge.
forming a trapezoidal-shaped section that is open at the bottom. The second step in the process was applying cor-
The plate thickness of either 3∕8 in. or ½ in. can accommodate rosion protection via hot-dip galvanizing, which took
all span lengths by simply changing the location of the bends. only a few days to complete. The galvanizing has a
Only the width of the top and bottom flanges and the depth of guarantee of 25 years and reduces maintenance over
the web vary depending on span length. However, the maximum that time frame to a level equivalent to or better than
span length for FSPG bridges is currently limited to 60 ft. that of concrete. Removable, galvanized bird screens
The FSPG system eliminates the need for internal and ex- were added to the open bottom of the FSPG gird-
ternal cross frames due to the large amount of lateral stiffness ers and allow easy inspection of the girders while still
generated by the design. The absence of cross frames in the keeping birds and other critters from nesting on the
system results in less costly details, and the need for welding is bottom flanges.
significantly reduced. The open bottom geometry of the gird- The final step in the manufacturing process was
ers simplifies inspection, and the hot-dip galvanization process precasting the deck panels to form the composite sys-
is used for corrosion protection. tem. Precasting the panels (for the four folded steel
Two companies—CDR Bridge Systems and HBS—have plate girders) took about three weeks. Once the pre-
been granted exclusive distribution rights, and the steel is fab- cast decks were completed, the prefabricated units
ricated by approved fabricators. (You can view standard draw- making up the superstructure were ready for ship-
ings at www.cdrbridges.com.) ment to the construction site for erection.

JANUARY 2017
 The first of the Pennsylvania FSPG bridges—a two-lane, 50- production priorities to meet Walsh/Granite’s changing sched-
ft bridge near Bradford, Pa.—was erected this past October in ule. That proactive coordination enabled the team to meet every
less than three hours. Closure pours (to complete construction erection schedule—especially important on an ongoing project
of the superstructure) took only a few days, which enabled the involving multiple bridges spread over a large area.
bridge to be reopened in 30 calendar days, five days ahead of the Another benefit of this proactive approach was that each
accelerated, five-week schedule for the project detour. This is a member of the team brought ideas and energy to the table
full month faster than it would have taken using conventional that improved the process and the system. The engineers ag-
cast construction. The second Pennsylvania FSPG bridge was gressively responded to design changes to substructure and
erected near Lewiston, Pa., just two weeks later—and took only roadway design, shop drawings and RFIs. The fabricator pro-
2½ hours. cured extra material so that it was prepared for any changes
during fabrication. And the design and precast teams worked
Enhanced Accelerated Construction together to solve an issue with lifting the exterior girders, add-
These first few FSPG units have provided our steel fabri- ing inserts into the barriers to balance the lift and keep the
cation and precast concrete partners with valuable experience exterior units from rolling during erection.
that has led to improvements in their processes and further The entire team worked together to create a better, faster
reductions in manufacturing time for future bridges. It also re- and more constructable product. It also proved that ABC is
inforced the need for communication throughout the process. not just about accelerating the schedule at the job site but
The team maintained constant communication with the con- rather accelerating the entire process of design, manufacturing
tractor, so that everyone knew precisely where each bridge was and construction.  ■
in the design and production process. We were able to adjust Owner
schedules through the supply chain without interrupting our Plenary Walsh Keystone Partners
other team members’ business. The responsiveness of the team
General Contractor
resulted in the completion of production in advance of sched-
Walsh/Granite JV
uled erection for every bridge despite changing erection dates.
In addition, the Walsh/Granite design-build team proactively Architect and Engineer
managed the schedule, thanks to such practices as a weekly dis- HDR, Inc.
cussion of detailed preproduction tasks between the teams. CDR Superstructure Engineer/Supplier
shared changes with its team and coordinated adjustments to its CDR Bridge Systems, LLC, Pittsburgh

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