A36 vs A992 in Wood Construction
A36 vs A992 in Wood Construction
(OP)
I know that title sounds strange. Someone told me the other day that there is no way an A992 steel beam ever comes close to developing its allowable stress capacity because of the concept that you cannot brace a steel beam's compression flange in wood construction to the extent you can brace it with say, a metal deck or some other concrete/metal composite system. The crushing and giving of the fasteners in a wood plate give just a enough that things are not as well braced.
As a result, this person designs all of their steel beams, in a wood construction setting, with an Fy of 36 ksi instead of 50, regardless of the fact that they are using A992. Has anyone else ever seen this?
As a result, this person designs all of their steel beams, in a wood construction setting, with an Fy of 36 ksi instead of 50, regardless of the fact that they are using A992. Has anyone else ever seen this?






RE: A36 vs A992 in Wood Construction
Example:
W12x14, 20' Unbraced length, maximum uniform load: 16 kip for Fy=50 ksi, 12 kip for Fy = 36 ksi (Ref: AISC Steel Construction Manual, 9th Edition)
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
Assume for example, you have a steel beam W12 "pushing up" into a row of wood 2x10 joists. If the floor overhead is overloaded, the local wood fibers of each joist are going to 'squish" at the small area where the 2x10 crosses the beam flange. The whole W12 and floor will sag under the total load, but that total load is transmitted to the whole through a row of very small 1.5 inch x 3 inch contact points. So, if you had an "infinitely strong" W24 or W36 even, you'd still be squishing wood fibers in the joists.
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
RE: A36 vs A992 in Wood Construction
This seems more like an academic discussion than a real world practical one.
Just upsize the beam so you are less than 24 ksi and be done with it. I imagine if you go over that, serviceability is going to control anyway.