By: Bill Wilson, Editor
Fate pulled Bob Rusch from the audience.
The Oklahoma Department of Transportation bridge division
engineer was attending a conference with his fellow peers in Atlantic City, and
one of the sessions he sat in on was how the city of Birmingham, Ala., handled
a span collapse. Less than a week later, a barge crashed into the I-40 bridge
in Oklahoma during the early morning of May 26. Rusch was now an active
participant in a disastrous discussion.
"I was asleep when it happened," he told Roads
& Bridges. "I was surprised it was that particular bridge because in
my mind that was the best of our navigation spanning structures. I never had
any concerns about that bridge."
Rusch and several other ODOT officials were flown to the
nearest airport and driven to the site where one devastating hit tore limbs
from the I-40 bridge and ruthlessly ripped families apart. Fourteen people
died, two piers were destroyed and a third was in critical condition. The
state's money route--in terms of moving commerce--had hit rock
bottom.
"We have to be prepared to react to eventualities like
this," said Rusch. "It's part of the job. It's not a
pleasant part, but it's something we have to do to be able to serve the
traveling public."
Over the course of the next 11/2 months, reaction was
unique, strong and efficient.
By the hour
When responding to an emergency, one has to drive fast and
keep a cool head. ODOT knew this, and within days went against customary
procedures and held a rare pre-bid meeting (June 8) for potential bidders at
the bridge site without a complete set of construction plans. Many of the
contractors helped with initial clean-up efforts, so they were familiar with
the scene. Still, ODOT wanted to exercise every precautionary measure.
"We wanted to make sure we were getting all the
relevant questions that needed to be fielded," said Rusch. "A lot
of questions were in relation with part of the structural steel span (span
four) that was remaining to be replaced. At that time, the span was still
hanging in the river, and they wanted to know exactly how much was going to be
left when they got their hands on it."
Normally, a transportation commission meets monthly to award
contracts. The contractor then has 10 days to execute the contract and return
it to ODOT. Another 14 days pass before ODOT sends the contract back to the
contractor, and a work order is issued two weeks later. With the I-40 bridge,
bids were read on June 12 at 11 a.m., an emergency commission meeting took
place at 2 p.m. to award the contract, the contract was signed at 4 p.m. and a
work order was effective at 6 p.m.
The A+B contract was drawn up by the hour instead of the
day. ODOT allowed a maximum B bid of 1,728 hours. Gilbert Central Corp., Ft.
Worth, Texas, the eventual winner of the job, came in at 1,368 hours. An
incentive/disincentive value of $6,000 an hour was assigned. The sum was based
on user costs--originally calculated in excess of $230,000 a day--for
detoured traffic. Eastbound I-40 traffic faced a crippling 57-mile detour route
using State Highway 2, State Highway 9 and U.S. 59. ODOT later conducted
traffic counts on the detour routes to determine the effect on local traffic
and the diverted I-40 motorists and revised the $230,000 daily user costs to
$430,000.
Before Gilbert Central won the job there was a three-day
scramble to get a hold of suppliers and subcontractors to complete the bid
process. ODOT turned to its website to post any project revisions, and it was
up to the contractor to make the adjustments and apply them to its bid.
Gilbert Central's networking capability was a huge
advantage after it was awarded the job. The company is a unit of Peter Kiewit
Sons' Inc., Omaha, Neb., which has more than 30 district and area offices in the U.S. and
Canada.
"Just getting the resources there was a big
deal," Jim Poe, Gilbert Central's assistant project manager for the
I-40 bridge, told Roads & Bridges. "We had to have enough maintenance
people to get the cranes going, and equipment and materials were coming into
the job from across the country."
Built with speed
While Gilbert Central called on some friends, ODOT hooked up
with the California Department of Transportation (Caltrans) and the Texas
Department of Transportation for any kind of tips on how to handle such a
disaster. Caltrans, with its earthquake experience, actually sent a crew to the
site.
Underwater inspections were conducted to check the standing
piers east of the wreckage, and an actual wrecking ball was used to remove the
part of the steel span (span four) that slumped into the water. A crane with
sheers was used first, but it was difficult to manipulate so the decision was
made to go with the wrecking ball. Caltrans marked off exactly how much needed
to be removed--125 ft--and workers actually stood on the span to
closely monitor the demolition. Excess steel was cut with a torch. Concrete
barrier walls were used as counterweight during removal. When span four went
down it created a full load on span five, and the counterweight prevented
another collapse.
A barge-mounted A-frame with cable winches pulled chunks of
damaged concrete to the surface, and Gilbert Central soon moved in with truck
loads of rock fill. The fill--60,000 tons of it--was used to build an
access road into the river so crews could reconstruct piers two and three on a
dry surface rather than water.
"It allowed us to build quicker," said Poe.
Quick thinking came into play with substructure
reconstruction. Casings for 9-ft-diam. drilled shafts had to be fabricated for
the job. Instead of waiting, Gilbert Central ordered 12-ft-diam. casings from
New York for the first three drilled shafts before the custom-made versions
arrived. The 60-ft-deep drilled shafts were placed 27 ft into solid rock.
Column design took a different turn to what was originally
constructed. To accelerate erection, it was decided to leave some of the
existing substructure in the water. To build around the foundations, the
traditional two-column design was scratched for a three-column alternative.
Longer spans also helped.
A concrete plant was located just two miles from the site,
and Gilbert Central opted for a high-early strength concrete, where more cement
is used in the mix. To quickly determine when the new concrete reached the
required strength workers used the intelliRock maturity system, (Circle 926)
developed by Nomadics Construction Labs, Stillwater, Okla. At the same time
concrete was placed in the formwork, one or more intelliRock maturity loggers
were placed in the structure. The loggers processed the time-temperature
history of the structure and stored the resulting maturity history of the
concrete at the specific location of the logger. The corresponding strength of
the structure was determined at any time from the maturity data provided by the
logger in conjunction with previously determined strength-maturity relationship
data. On average, the cure time was less than 24 hours.
Pier construction consisted of the drilled shafts, a crash
wall (10-ft-tall solid mass of concrete which lies on the three drilled shafts),
the three circular columns, a cap and concrete beams. Steel beams were used
when the bridge was first built, but the short time frame called for precast
bulb tee BT72 concrete girders, 12 on each of spans one, two and three.
Gilbert Central executed single-deck pours on spans one, two
and three. Span four, which consisted of separate eastbound and westbound
spans, contained some of the trickiest of tasks. ODOT was able to save a
portion of the original section by knocking out the 125 ft of hanging concrete
and then flame straightening--both vertical and horizontal--mangled
steel beams. Initially, one of the four steel girders did not sit right, but
this problem was resolved with the weight of the concrete deck pour (there was
one eastbound pour and one westbound pour).
When it came to connecting the new steel with the flame
straightened steel on span four, Gilbert Central used an existing splice to tie
the two together.
For deck connection prior to the two pours, dowel rebar was
attached to the existing deck of span four. A 3/4-in. expansion joint was
installed to allow the separate spans to react independently.
A modular expansion joint connected the concrete girders of
span three to the new portion of span four.
The I-40 bridge was completely healed in less than 47 days,
which earned Gilbert Central almost $1.5 million in hourly incentives.
