Steel plate over timber deck to improve load distribution?
Steel plate over timber deck to improve load distribution?
(OP)
Hello,
I am performing a load rating on a steel beam bridge with transverse timber plank deck. The timber deck is causing the bridge not to rate adequately. I am thinking of ways to temporarily strengthen the deck. I think placing a steel plate (3/4" +/-) over the deck would suffice, but am not finding anything in aashto or elsewhere that indicates how exactly this would distribute the load over the timber deck. The steel plate alone would be adequate to support the loads, although I'm somewhat concerned with the timber underneath crushing. I can assume a 45-degree tire load distribution through the steel plate, although I think that's too conservative.
Any Suggestions?
Thanks,
I am performing a load rating on a steel beam bridge with transverse timber plank deck. The timber deck is causing the bridge not to rate adequately. I am thinking of ways to temporarily strengthen the deck. I think placing a steel plate (3/4" +/-) over the deck would suffice, but am not finding anything in aashto or elsewhere that indicates how exactly this would distribute the load over the timber deck. The steel plate alone would be adequate to support the loads, although I'm somewhat concerned with the timber underneath crushing. I can assume a 45-degree tire load distribution through the steel plate, although I think that's too conservative.
Any Suggestions?
Thanks,





RE: Steel plate over timber deck to improve load distribution?
RE: Steel plate over timber deck to improve load distribution?
RE: Steel plate over timber deck to improve load distribution?
www.PeirceEngineering.com
RE: Steel plate over timber deck to improve load distribution?
RE: Steel plate over timber deck to improve load distribution?
www.PeirceEngineering.com
RE: Steel plate over timber deck to improve load distribution?
RE: Steel plate over timber deck to improve load distribution?
Normally, in timber bridges of this type, there is a wear strip of timber planking normal to the structural planking you describe that functions to span out the wheel load too. This planking is periodically replaced as it wears out, saving the timbers below. This same transverse planking does though create the potential for unoobserved rot of the planking below.
To control spippage, although somewhat unorthodox, you could put an additional timber planking wear strip over the steel plate to define the drive surface. Just a thought.
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Steel plate over timber deck to improve load distribution?
We ended up turnkey replanking the entire timber deck for just under $20,000 using Osmose Railroad Services out of Wisconsin. No gain in the structural capacity on the NBIS superstructure re-rating, but easily bought us another 10 to 20 on the lifespan. We also had a light application of asphalt spray patch applied for traction.
PM me and I'll get you more information if you need / want it. As mentioned, the timber deck is a wear item. I'd underscore that with the client and approach it that way. Depending on what thier replacement horizon is, I'd honestly consider a redecking rather than a patch job if the substructure and other elements are sufficent.