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Pier Pressure

State to enforce weight limits
on Milton-Madison Bridge

Tests of 80-year-old piers
may determine decision on whether
to build new or use existing pillars

"If we didn’t feel the bridge was safe,
we would close it down." – Andrea Clifford,
Public Information Officer for Ky. Transportation Cabinet

By Konnie McCollum
Staff Writer

April 2009 Indiana & Kentucky Edition Cover

April 2009 Indiana & Kentucky Edition Cover

(April 2009) – A longstanding, vital Ohio River crossing for interstate commerce between Indiana and Kentucky is about to be shut down for an indeterminable time. That’s because the Milton-Madison Bridge is deteriorating at a faster rate than officials anticipated, according to a December 2008 biennial inspection.
As a result, a 15-ton weight limit that will ban loaded semis and other heavy vehicles from the 80-year-old bridge will go into effect in early April. Kentucky Transportation Cabinet officials call the weight limit a precautionary measure until repairs can be made to the damaged parts. They plan to post signs to warn truckers of the new weight limit and task highway enforcement officers to monitor the restrictions.
Vehicles weighing more than 15 tons must take an alternate route to cross the Ohio River. The nearest Ohio River bridges are 46 miles downstream in Louisville, Ky., and 26 miles upstream at Markland Dam above Vevay, Ind.
Although the permanency of the weight restriction won’t be known until repairs and an in-depth inspection have been made, the issue has again raised questions about the urgency of replacing the functionally obsolete and structurally deficient bridge.
“If we didn’t feel the bridge was safe, we would close it down,” said Andrea Clifford, Public Information Officer for District Five of the Kentucky Transportation Cabinet. “We saw more rapid deterioration than seen in the last fracture critical report done in 2006. We implemented the weight restriction because we want to prevent the problems from deteriorating further.”

• For more information about the Milton-Madison Bridge Project, visit: www.MiltonMadisonBridge.com.

At issue is deterioration on a gusset plate on the Indiana side of the main truss, several vertical posts in the deck trusses and two splice plates on the lower chord of the small truss, said Clifford.
After the repairs are finished by the end of the summer, the bridge will be inspected “like a fine tooth comb,” said David Steele of the Kentucky Transportation Cabinet. “We’ll decide after that whether to lift the (weight limit) restriction.”
Corey Murphy, executive director of Madison’s Economic Development Partners, said as long as the weight limit is temporary, there will be ways for businesses to work around the issue. “If it becomes permanent, that will be another challenge. Looking at the positive side of this, we are going to use this opportunity to keep pushing forward in clear, concise agreement for a new bridge. Time is of the essence.”

Carrying the load on the bridge

Several area trucking companies also hope the weight restrictions are not permanent. At Madison Tool and Die, owner Gary Sparks said the new weight limit is “pushing us on extra mileage and time.” He wasn’t sure if his company would be able to pass those costs onto his customers. “More than 30 percent of our business will be affected,” he said.
In Milton, Indiana-Kentucky Trucking Inc. runs more than 60 trucks a day across the bridge. Owner Robert Parker said the effects of the limit depend on how long it is in place. He said the 1997 rehabilitation was tough on his company, a building materials trucking firm that has been in business since 1978.
“We couldn’t come across the bridge loaded or unloaded because of width restrictions,” he said. “This time at least it sounds like we will be able to cross unloaded.” His semi-trucks weigh 24,000 pounds when empty.

Pier Graphic

He worried about competition setting in because of the extra charges that will be tacked on for the extra mileage his drivers will be forced to go. “This is going to affect all of us, from the cost of steeper groceries to people building homes,” he said.
Clifford said the $200,000 needed for the bridge repairs will come from a bridge maintenance fund, and Indiana and Kentucky will equally share the cost. She said this setback doesn’t impact the Milton-Madison Bridge Project, a three-year, $5 million engineering study for a bridge replacement led by Wilbur Smith Associates of Lexington, Ky. “Both transportation departments are committed to solving the problems in an expeditious manner.”
Already, the project has worked to develop a purpose and needs statement, part of the necessary federal requirements that will help screen and narrow the options for the project.

There are currently four options for the project that all have to be considered:
• Do Nothing Option: This would eventually result in the total closure of the bridge for vehicle traffic by 2025.
• Rehabilitation Option: This would slow the rate of deterioration but could result in full closures totaling 12-18 months.
• Superstructure Re-placement: This would use existing piers and widen them for a wider superstructure. It would be more cost-effective and possibly faster than a new bridge on a new location, but would result in a nine-month closure, officials said. The superstructure replacement would depend on whether tests on the existing piers determined this option is a possibility. The superstructure consists of that portion of the bridge above the bearings, including the deck, handrail, curbs, floor system and structural members.
• New bridge on a new location: Several new locations have been identified, and a screening process will narrow those options.

“We are trying to move as quickly as possible. We have a sick bridge, although I’ve seen much worse,” said John Carr, a Wilbur Smith Associate who serves as the project manager.
“We bought some time with the 1997 rehabilitation, but if we have to do another one, we may not be able to keep the bridge open at all during it.” Another rehabilitation project would slow everything down and could actually keep the bridge closed longer than a superstructure replacement, he said.
There would be advantages and disadvantages for a superstructure replacement. The cost would be far less than that of a new bridge, and there would be considerable time savings.
“If we choose to put a new superstructure on top of the existing piers, we could possible have that done within three years, but it would mean a bridge closure for up to nine months,” said Carr. “In today’s environment, we need to carefully work to make money stretch.”

Testing the piers

John Carr

Carr

Already, geotechnical crews from the Kentucky Trans-portation Cabinet have worked to obtain pier core samples from the bridge. Engineers will test the viability of the existing piers, which could be used during a replacement of the superstructure, an alternative being considered for the Milton-Madison Bridge Project. Results are expected in the spring of this year.
Bart Asher, a civil engineer in the Kentucky Transportation Cabinet’s Division of Structural Design-Geotechnical Branch, said that the re-use of foundations from one bridge to the next has been a fairly common practice.
“Although many people believe that state government transportation departments have deep pockets, we are also struggling to do more with less funding, just like everyone else,” he said. “Revitalization or reuse of all or part of an existing structure is an important tool.”

Bart Asher

Asher

He said one thing people need to keep in mind is that historically, a good mixture of concrete actually gains strength over time. “The normal compressive strength used in normal current designs is 3,500 pounds per square inch. Preliminary results indicate that the concrete samples taken from the Milton-Madison Bridge range from 6,000 to 13,000 pounds per square inch, which is very encouraging for the reuse of the piers.”
“The level of testing for evaluation of the re-use of a substructure will vary depending on the structure,” he said. “Sometimes visual inspections and review of existing plans is all that is needed.”
In the case of the Madison-Milton Bridge, visual inspections are just a part of the inspection. A major river bridge is defined as being more than 500 feet in length, according to Carr. The current Milton-Madison bridge has a span more than 600 feet.

Sean Pickerrell

Photo by Don Ward

Sean Pickerrell of Elizabethtown, Ky.,
guides the drill machine
into the ground on
the Milton, Ky., side
of the Milton-Madison
Bridge. He is one of
several state
employees taking
core samples in early
March that will be
tested in Frankfort, Ky.,
to determine the condition
of the concrete piers.

Asher said that in the visual evaluation, numerous inspections of the visible portions of the piers have been undertaken by experienced engineers and technicians. These inspections can tell officials a great deal about a structure. “Some of the recent issues with the truss that resulted in the weight limits were discovered in part from visual inspections,” he said.
As part of those visual inspections, there were several methods used, including impulse response, impulse radar, corrosion rate testing and hammer soundings, which are basically tapping the concrete with a hammer to evaluate its competence.
Also on the Milton-Madison Bridge, there was several other tests including drilling. Asher said the drilling of the pier concrete from the top of the pier and 50 feet into the bedrock was an important test because it allowed engineers to examine the competency of the concrete from the top of the pier all the way down.
“As you know, this bridge is 80 years old,” he said. “Construction procedures were different in that era” There were questions that needed to be answered as to how the concrete was placed, its homogeneity, or makeup, and in general the quality control that was used in its placement. “The drilling answered many of the questions,” he said.

Getting to the bottom

The piers rest on bedrock. Retrieval of the bedrock cores will allow the engineers to test the suitability of the bedrock under the piers for the capability of supporting additional loads.
Many other tests are conducted on the samples (see graphic, page 22). Asher said those tests are conducted so engineers and officials can make an “informed decision” about whether the piers can be reused. One of the firms involved in the project, Construction Technology Laboratories of Skokie, Ill., will take the results and calculate the anticipated remaining service life of the piers, he said.
During the testing of the piers, Asher said numerous problems were encountered but none that were not resolved. One included extremely cold weather during drilling, which caused extensive problems with sample retrieval.

Bart Asher

Photo provided

Bart Asher hangs from under the
deck of the Milton-Madison Bridge
during testing in February.

Another was the potential impact of extended drilling on the Peregrine falcons who live on the bridge. The Kentucky Department of Fish and Wildlife Resources helped resolve that issue.
Asher said the concrete was extremely hard and difficult to drill, and several drill bits had to be tried in order to get through the piers. “This is a good thing, though,” he said. They also hit numerous pieces of steel in the pier that slowed drilling production.
During a superstructure replacement for a bridge, the piers would be widened and new caps would be added. Carr said the bridge would be open for traffic while that work is being completed.
Then the old steel of the bridge would be lifted off and dismantled, and the new trusses and steel would be put back on using a crane.

Core samples

Photo provided

The core samples of
bedrock are tested in the lab.

A superstructure replacement would affect the design, said Carr. Only arches and trusses could be considered. During a February public meeting in which audience members were polled about their design preferences, cable stay bridges were among the most popular.
“We could even build a truss that would be wider but that would replicate the existing bridge,” said Carr.
Aaron Stover, a civil engineer at Michael Baker Corp., another firm working in collaboration on the bridge project, said the idea of replacing the superstructure of a bridge on existing piers is not new to Ohio River Bridges.
Two projects, the Sewickley Bridge, just outside of Pittsburgh, and the Williamstown Bridge over the Ohio River between Williamstown W.Va., and Marietta, Ohio, have already been completed.
“Our company is currently involved with several projects in Connecticut and Pennsylvania, where the superstructure is being replaced,” he said. “We have also completed similar project in Pennsylvania and Ohio within the last five years.”
Stover noted that the Sewickley Bridge and the Williamstown Bridge piers were 70 and 90 years old, respectively, when their superstructures were replaced. Both bridges are still in service today.

Drill bit

Photo provided

A drill bit used to cut
throught the tough bedrock.

Asher said his agency recently did an intensive investigation on a stone masonry abutment, or bridge end foundation, which was built in the pre-Civil War era. The re-use of that structure is still in question. “We have re-used numerous foundations of stacked stone,” he said.
In Wolfe County, Ky., a bridge is being constructed on a tall concrete pier that is about 50 years old.
Only one of two piers on that bridge was re-usable.
The Roebling Bridge across the Ohio River between Cincinnati and Covington, Ky., was constructed in 1866 and is still in use today. The pier towers are original on that suspension bridge.
Carr said officials on the project are “well aware of the financial burdens and hardships the communities.

Back to April 2009 Articles.

 

 

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