1928-2004: (
Bridge Hunter; no Historic Bridges;
HAER;
Satellite, the approach is now a memorial)
The official name of the new bridge is the Bill Emerson Memorial Bridge.
Whenever I start with an HAER photo of a truss bridge, you know you can probably shed a tear for that bridge. When this opened in 1928, it was the only vehicular bridge across the Mississippi River between St. Louis and Memphis. [
SEmissourian]
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HAER MO,16-CAPGI,6--1
1. CAPE GIRARDEAU BRIDGE, VIEW TO THE SOUTH - Cape Girardeau Bridge, Spanning Mississippi River at State Highway 146, Cape Girardeau, Cape Girardeau County, MO |
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HAER MO,16-CAPGI,6--10
10. CANTILEVER THROUGH TRUSS, VIEW TO THE NORTHWEST - Cape Girardeau Bridge, Spanning Mississippi River at State Highway 146, Cape Girardeau, Cape Girardeau County, MO |
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David Gulden posted
Bill Burnett name that boat maybe HELENA or the HUCK FINN?
Bill Burnett: Silo stack, looks like the Helena. |
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Bridges Now and Then posted
Corporal K. McGrath of Chicago is standing guard at the toll house on the Morgan Oak Street approach to the Cape Girardeau, Missouri, Traffic Bridge, Sunday, February 22, 1942. (Southeast Missourian) |
And since it was replaced in the 21st Century, the new bridge is a cable-stayed bridge. "The Bill Emerson Memorial Bridge, which is named after an eight-term Southeast Missouri congressman who helped secure funding for the project, is a 4,000-foot long, 100-foot wide structure linking Cape Girardeau, Missouri and East Cape Girardeau, Illinois. The bridge includes an eastern approach and a 2,086-foot cable-stayed unit with a 1,150-foot main span. Currently [2003], 14,000 vehicles cross the current Mississippi River Bridge daily – and by 2015, it is projected that 26,000 vehicles will be utilizing the two crossings. The estimated cost of the bridge is $100 million, which is owned by the State of Missouri." [
American Segmental Bridge Institute] Bridge Hunter indicates that the 2018 usage was only 10,992. So the usage went down instead of the predicted up!
As John Weeks points out, this bridge is a monument to pork barrel. I learned yesterday that
a 1952 bridge that carries a major east/west interstate, I-10, and handles 81,100 (2016) vehicles/day has been trying to get replacement funding for over a decade. And that bridge shakes so much that Louisiana gave up trying to keep lights on it. Several articles point out that Bill Emerson was an 8-term representative from Missouri and responsible for obtaining the 80% Federal funding for the replacement. But only John mentions that he served on the Public Works and Transportation committee. Each state had to contribute 10%. "Several factors have been blamed for the bridge's many delays in planning and construction, including Illinois' reluctance to participate in the project, as well as issues with the bedrock of the river (this resulted in the hiring of a new contractor)." [
owlapps]
Again, if you save this photo and view it with a photo app that allows zooming, you should be able to read the text.
Note the wires connecting the cables. That is the first time I have seen that. I first noticed them in this photo that introduced me to this bridge.
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Zachary Bryant Morre posted
M/V Jeff boat southbound cape Girardeau w 25 loads |
While looking for a street view that gives me a better view of the "cross cables," I discovered that they are having to do a major repair already.
"The project consisted on the rehabilitation the West approach, on the Missouri side of the bridge, by replacing the approach slab, repairing the back wall of the abutment and exchanging the modular expansion joints." [
mageba]
It looks like each segment of the cross cable has a turnbuckle. I wonder how often they have to be adjusted. It looks like a maintenance nightmare.
I searched for some photos taken soon after construction to determine if the cross cables were part of the original design or if they were added later as a patch for some sort of problem. They were added. More on the cross cables below.
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Traylor
"The bridge substructure work included two dredged caissons and two 356-foot-tall main pylons. The drilled shaft foundation has 10 drilled shafts that extend into the rock 12 to 15 feet, each with a diameter of 6 feet. The superstructure work included 128 stay cables, eight million pounds of structural steel and a precast concrete deck. The two concrete caissons were located at the Illinois pylon and Illinois back pier of the main cable stayed span. The caissons were approximately 60 feet wide by 100 feet long by 35 feet tall. Each caisson contained 15 dredge wells approximately 15 feet in diameter. Both were constructed using the sand island method with 60-foot-tall sheet pile follower cofferdams attached to the top. The total sinking distance for each caisson was approximately 60 feet." |
This diagram emphasis that the caissons were not needed for the two towers, but for one of the towers and for Pier 4. Pier 2 is built on bedrock.
The bridge contains 8,000 tons of steel and cost $140m. (The $100m figures above were estimates. And, as of 2021, MDOT has not updated
their web site to reflect the actual cost of a bridge completed in 2003.)
Even with a navigation span 1,150', the bridge suffered an
allision by a barge around 9:20pm on Nov 15, 2019. MoDOT inspected the bridge the next morning and the bridge was reopened by 9:30am.
In addition to being a monument for pork barrel spending, is this bridge also a monument for corruption? First of all, construction started in 1997, but it did not open until 2003. But the reluctance of Illinois to fund its 10% and bedrock problems may explain that delay. "The foundation limestone for the seismically critical Pier 3 [the east tower] of this massive new road bridge over the Mississippi River was found to contain huge karstic features, infilled with red clay. Various deep foundation options to support the pier’s footing were examined but found to be not cost effective and practically impossible technically. Geosystems acted as a subconsultant to the bridge designer (HNTB of Kansas City, MO) to review possible foundation remediation options, and 3-fluid jet grouting of the 129 foot by 87.5 foot foundation for a depth of 50 feet below rock head was recommended." [
GeoSystemsBruce]
But the thing that brought the word "corruption" to my mind was the sufficiency rating of this modern bridge:
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Bridge Hunter, average daily traffic is 81,000
"Future prospects: On the long-term replacement list for LA DOTD, but no clear timeframe set" |
Or to the 1965 I-80 bridges in Joliet, IL.
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| Bridge Hunter, average daily traffic is 47,00 (The traffic is that low because it needs more lanes. It causes congestion problems on I-80. These bridges are functionally and structurally very deficient, but IDOT is still not planning to replace them. Given that IDOT is willing to replace truss bridges that are structurally OK just because they don't have 12' lanes and a shoulder, I'm really confused about the I-80 bridge inaction.) |
The bottom line is that this new bridge has a rating below that of two old bridges that are recognized as very bad. The good news is that the cross cables must have done their job because the superstructure is rated Very Good. Following the "
View more at BridgeReports.com" link, we learn the bridge needs work that is estimated as $90,271,000. That is almost as much as its initial construction estimate! But the only problems I can find are the abutment and the protective coating on the pier caps. I find it hard to believe that it would cost $90m to repair those. Is the problem with the bedrock or the piles and the inspection report doesn't have a a method to note that? I can imagine foundation repairs costing a lot. (The inspection report lists the years 1996 and 2001. The bridge wasn't even open then! So I'm confused.)
It was designed to last for 100 years [
nehrp]. But it didn't even make 20 years?
Concerning the Cross Cables
Because this bridge was built in the New Madrid Seismic Zone, 84 sensors were installed in the bridge and nearby ground as part of its construction.
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nehrp
(This is one of several interesting links I've found that MoDOT has broken.) |
A study was done to develop a three-dimensional finite element model of the bridge that was accurate enough to include the sag in the cables and the interactions with the ground. The goal of the model was to determine the vibration modes and frequencies because a cable-stayed bridge is very flexible. In addition to the inputs of traffic and wind loads, earthquake forces were also studied. Specifically, the model was tested with data from a May 1, 2005 earthquake of M4.1 on the Richter scale. After validating the model with data, they then ran the model with a design earthquake. The
Sep 2007 final report [also
transportation.mst.edu] indicated that the vibrations of the tower were within the safety margin. The towers above the cap beam (the beam just under the deck) remained elastic. However, the solid portion of the towers under the cap beam experienced "moderate
yielding out of plane." I think that means the bridge will still be standing but the towers may be a little cracked after a major earthquake. [Item 9 on page vi] However, "cables begin to vibrate severely at a natural
frequency of 0.842 Hz or higher." [Item 5 on page v] I presume the cross cables were added to attenuate these vibrations. The study concluded that all of the cables remained elastic during a design earthquake and were always in tension. Since the cables do not go slack, further seismic analysis can use simpler linear finite elements for the cables. I'm sure that makes the computer simulations run faster.
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ds.iris.edu
The design earthquake was of magnitude 7.5 or greater |
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faculty.ce.cmu.edu
[I didn't understand most of this, but I did learn that the "cap beam" in the tower is the cross member just below the deck. ] |
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ScholorsMine
[This article provides a graphical interpretation of some simulation results. This article also has the above cable safety graphic without the values blacked out.] |
Now I'm left with the question of why is this the only bridge I've seen with cross cables. Have they learned to design the bridges so that the cables don't severely vibrate during an earthquake or is this the only one built so near a dangerous fault?
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