How are rail cars load rated and what does that load rating mean when rail cars are used as bridges? 4

[cool47]

I am part of community that has a private bridge that consists of two flat bed rail cars suspended from concrete abutments. The side of each car has a capacity of 150,000 lbf given on the side of the car. My question relates to the assumptions that were used to calculate this capacity. Was a uniform load assumed? Was some version of point loading assumed?

 

[TenPenny]

"The side of each car has a capacity of 150,000 lbf given on the side of the car"

What else is on the side of the car? That might help identify what the cars where, and the useful dimensions thereof. The model railroad community has a huge assortment of useful information.

 

[SlideRuleEra]

cool47 - See the 141 page report "Use of Railroad Flat Cars for Low-Volume Road Bridges" prepared for the Iowa DOT. Here are the conclusions:

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[PEinc]

Very nice, SRE and HotRod.

http://www.PeirceEngineering.com

 

[cool47]

Thank you HotRod, SRE, and PEinc

 

[BridgeSmith]

The document excerpt SRE posted draws attention to a significant factor in the rating and capacity - Is there a deck or attachment that provides a means for load sharing (shear transfer) across the joint between the 2 rail cars? This can make a huge difference in the capacity and rating, since the exterior support beams are typically smaller than the interior beams. If a mechanism for shear transfer between the 2 railcars does not currently exist, you may want to consider retrofitting it to provide that.

 

[cool47]

There is a wood deck across the two cars but in my judgement the load transfer would be negligible. Currently because of the approaches to the bridge most traffic across the bridge goes down the middle and the load is approximately shared, approximately half on each structure. I fully understand load sharing would be a non conservative and bad assumption. Your suggestion of tying the structures together is a good one. Cost could be an issue.

 

[SlideRuleEra]

...suggest reading the entire document...

http://www.SlideRuleEra.net

http://www.VacuumTubeEra.net

 

[cool47]

SRE...have down loaded your suggested paper and pursued same. Looks to be right on point. Well read in detail. Thanks.