| Better Bridges
Missouri Cable-Stayed Bridge Opens
After three years, the new Cape
Girardeau Bridge now moves traffic across the mighty Mississippi.
by April Goodwin
 The new cable-stayed structure stretches for the length of 13 football
fields over the famous waterway
Two H-shaped towers, constructed of reinforced concrete, hold up 64
support cables each and extend 330 feet above the water. The cable strands
are concealed by a white, high-density, polyethylene pipe and plastic
sheath. Altogether, the strands that make up the diagonal cables could
span for 171 miles, according to the Missouri Department of
Transportation.
Construction of the Cape Girardeau Bridge, also called the Emerson
Memorial Bridge, is estimated at $100 million; 80% of the funding comes
from the federal government. The other 20% of the cost is split between
Missouri and Illinois.
Getting started
The design of the bridge began in 1996 and major construction started
in June 2000, when the MoDOT awarded a contract to Evansville, Indiana’s
Traylor Brothers Inc., one the foremost bridge contractors in the world.
Traylor Brothers has completed more than 130 major bridge projects,
including some of the largest and most complex bridge projects in the
world.
The MoDOT contracted Traylor Brothers to:
- Complete Pier 2.
- Construct Piers 3 and 4.
- Install 128 stay cables.
- Construct the bridge deck on the main bridge and the Illinois
approach bridge.
- Install 140 decorative lights.
Substructure work included two dredged caissons and two 364-foot-tall
main pylons. Superstructure work included installation of the stay cables,
8 million pounds of structural steel, and an 11-inch-thick precast
concrete deck with 3-inch-thick poured-in-place micro silica fume overlay
concrete.
 The suspended four-lane highway is 96-feet wide, and rises 60 feet
above the Mississippi. The deck is composed of steel plate girders and
floor beams and pre-stressed concrete slabs. A concrete barrier is located
in the center of the bridge, and two concrete railings are placed along
the edges of the deck.
The overall weight of the bridge is 266-million pounds — equal to the
weight of 304 jet airplanes. Crews are using an estimated 13-million
pounds of reinforcing steel and 243,688,500 pounds of concrete to build
the bridge.
Annual status reports
By the summer of 2001, Traylor Brothers had finished the dredged
caisson for the Illinois-side pylon despite some nasty winter weather in
late 2000 and early 2001, and one minor challenge: driving the caisson the
last 10 feet.
In order to force the caisson to sink the final distance, a blasting
subcontractor was hired to set off explosive charges that shook it down. A
total of 58 rounds were needed to complete the job. After the caisson was
landed and the bottom cleaning was finished, it was a mad rush against a
rapidly rising river to get the tremie seal concrete poured.
On Friday, June 1, 2001, the crew received a forecast that predicted
the river to rise above flood stage early the next week. Traylor Brothers
decided to begin the tremie pour the next morning and pour through the
weekend in an effort to beat the flood. Two crews traded 12-hour shifts to
complete the 4,700-cubic-yard pour by early Monday morning. The MoDOT
reported it to be its largest concrete pour on record. Shortly after the
record-breaking pour, the river flooded. As it turned out, if Traylor
Brothers had not pushed through the alternating 12-hour shifts, the crew
would’ve been delayed by about eight weeks.
By the summer of 2002, the 350-foot Missouri pylon was complete and the
crew was focusing on the Illinois pylon, which was well along. Work was
also progressing on the Illinois back pier. Several pours were finished,
including a 1,900-cubic-yard distribution block concrete pour and six-stem
pours, ranging from 750 cubic yards to 1,200 cubic yards. Eleven of the 30
tower leg pours for the Illinois pylon, averaging 80 cubic yards each,
were done, and the follower and sand island cofferdams for that pier had
been removed.
 By the spring of 2003, construction of the 356-foot main pylon in the
center of the river was complete. Stem construction for the Illinois back
pier was also complete and 16 of the 64 stay cables for the Illinois pylon
were installed. Rebar installation and deck concrete placement on the
Illinois approach bridge was in progress and superstructure erection of
the Missouri pylon was well underway. All stay cables were in place by
August. Owens said superstructure finish work, overlay, barrier walls, and
cable grouting should be complete by the end of the year.
Rental equipment
Rental Equipment from RSC, one of three brands belonging to Rental
Service Corporation, Scottsdale, Arizona, North America’s second
largest equipment rental company, played a vital role during construction
of the bridge. Traylor Brothers has rented a variety of equipment from the
local RSC stores since December 2000 — everything from mini excavators,
skid-steer loaders, and air compressors to variable-reach forklifts,
pressure washers, brush chippers, and diaphragm pumps.
The contractor prefers to own its own equipment but occasionally needs
to rent equipment when there isn’t a company-owned machine available —
or when it is more cost effective to rent equipment than to transport an
owned piece to the jobsite. Project Manager Larry Owens says Traylor
Brothers also rents if a piece of equipment is only needed for short-term
use, or if a unique size or capability is required.
In the case of the Cape Girardeau Bridge, Traylor Brothers rented
several items from RSC, including several 120-foot boom lifts, a ride-on
broom, and half a dozen light towers.
The crew used the boom lifts for access when performing miscellaneous
tasks like concrete patching, form stripping, steel bolt ups, and so on.
The broom was used to quickly and efficiently clean up the bridge deck.
The light towers were used for night work.
Time to open
Cape Girardeau has evolved over the past 200 years from the tiny French
trading post it once was. The Bill Emerson Memorial Bridge replaces a
bridge built in 1927 and is expected to handle the increased traffic flow
in the area.
An estimated 14,000 vehicles cross the bridge daily. By the year 2015,
the Missouri Department of Transportation estimates about 26,000 vehicles
will cross the bridge each day.
In mid-August, cranes on barges lowered two 3,700-pound, 6-foot-long
steel girders in place to close the gap.
By September, all of the deck panels were in place, the cables
adjusted, and a 3-inch concrete surface poured across the length of the
span. Then, concrete barrier walls and electrical work were completed and
decorative lighting added. In addition, grout was pumped between the
polyethylene casing and plastic sheathing that covers the steel cables.
After the last of the pre-cast deck panels was erected, a 3-inch
driving surface to the cable-stay portion of the bridge was installed.
Traylor Brothers used special concrete containing silica fume, a byproduct
of silicon metal. Concrete containing silica fume is highly impermeable
and has an estimated life of 50 years.
April Goodwin is a technical writer in Des Moines, Iowa.
Reprinted from Better Roads Magazine
February 2004 |
