The Merchant’s bridge, which is on the Mississippi River at St. Louis, MO and owned by the TRRA, is used for both class 1 freight and Amtrak.
I wonder what a possible replacement for the 120 year old Merchant’s bridge would look like? Would the railroads accept a cable-stayed bridge for their heavy freight trains?
There hasn’t been an entirely new bridge for railroads built on the Mississippi River in decades. I think the newest rail bridge on the Mississippi is the CB&Q/BN/BNSF bridge at Quincy, IL, built in 1960.
http://www.stlbeacon.org/issues-politics/96-Development/110176-money-to-study-merchant-bridge-replacement
Aging Merchant’s Bridge studied for possible replacement
By Robert Koenig, Beacon Washington correspondent
Posted 5:51 pm Mon., 5.9.11
WASHINGTON - The nearly 120-year-old Merchant’s Bridge across the Mississippi River at St. Louis is being scrutinized for possible rehabilitation or replacement to help relieve some of the rail traffic on the near-capacity MacArthur Bridge - and possibly allow for faster Amtrak train service into the city.
On Monday, the U.S. Department of Transportation announced a $13.5 million grant “to advance the design of a new bridge over the Mississippi River” that might replace the Merchant’s Bridge, which was built in the 1890s to handle mainly St. Louis freight but also handles a limited number of Amtrak passenger trains. The bridge is about three miles north of the Eads Bridge.
The Merchant’s Bridge study grant was bundled by the DOT with an announcement about $2 billion in “high-speed rail awards” that also included $268.2 million to buy 48 high-performance passenger rail cars and 7 quick-acceleration locomotives for the St. Louis to Chicago high-speed rail corridor as well as 7 other Midwest corridors.
Anothe
BNSF just replaced their bridge at Burlington, IA. CP is in the planning stages to replace their bridge at LaCrosse, WI.
For some more information on and photos of this bridge, see:
http://bridgehunter.com/mo/st-louis-city/merchants/
Normally, a “Type-Size-Location Study” would determine what the replacement bridge would look like. However, a number of factors pretty much lead to the replacement looking a lot like the existing bridge, to wit:
- Location is pretty much fixed by the existing track network in the region, plus or minus possibly a few feet.
- Having recently rebuilt the approaches (2005), the owners will be reluctant to toss away that investment/ expense by moving the bridge more than a few feet.
- Most importantly, the Mississippi River there being a navigable waterway, it’s next to impossible to change anything, except to improve navigation by removing obstructions - and that would risk not being able to keep the existing pier locations, which would make a replacement much more expensive. So those pier locations are likely “grandfathered”, and will be kept, unless there’s a serious structural or navigation issue with them “as-is”.
- Hard to find the lengths of the main spans, but they appear to be 3 simple through-truss spans, each about 600 ft. long.
- That’s still an economical length for a truss these days, and the usual span/ depth ratios of 10:1 to 15:1 or so would indicate a maximum depth/ height of 40 to 60 ft. Since that’s more than the usual vertical clearance requirements even for a double-stack train these days - even allowing for future electrification - a through truss is a good choice, though it would likely be deeper in the middle to develop additional strength, just as the existing ones are.
- The situation looks ideal for building the replacement spans on barges, and floating them into place of the existing spans during short closures or outages o