Structural slab put on top on existing wooden bridge
Structural slab put on top on existing wooden bridge
(OP)
On my property in the NC mountains, I have an existing wooden 15'x 40' bridge which has allowed cars, timber trucks, to cross a creek. It has seen better days, and I would like to use it as a form to pour a reinforced concrete slab on top of it; ideally being able to be standalone later on. I would dig out a substantial footer on both ends, frame around all sides, lay a sheet of polyethylene, add a rebar grid on chairs, pour slab. I need help with the rebar part, and slab thickness. 1" rebar 12"OC in a 6" concrete slab? Overlay two 20' rebar by adding a third centered at their joint? Would a 2'x2'x15' footer on both ends be sufficient? The slab would actually be 6" thick at its minimum and 10" at its maximum, due to spacing of 4x10s running the length, on top of regular surface. Pic of bridge attached.






RE: Structural slab put on top on existing wooden bridge
The bridge is a timber tresle with wear strips. Commonly, the wear strips are replaced as they wear. Looks like that needs to be done now. Also, if rot is to occur in the structure, it will most likely occur and hide under the wear stips, attacking the strength of the underlying decking.
You really need to pull in a local structural engineer to help you here. DO NOT attempt to do this yourself.
Your call...
Mike McCann
MMC Engineering
http://mmcengineering.tripod.com
RE: Structural slab put on top on existing wooden bridge
Garth Dreger PE - AZ Phoenix area
As EOR's we should take the responsibility to design our structures to support the components we allow in our design per that industry standards.
RE: Structural slab put on top on existing wooden bridge
RE: Structural slab put on top on existing wooden bridge