Steel Baseplate for a Wood Column?
Steel Baseplate for a Wood Column?
(OP)
I've got a 6x6 DF No. 2 post with about 11,000 lbs vertical load resting on a 6" reinforced slab (assume 3000 psi). According to Tomanovich's GRDSLAB calculator this will not work. Typically I would say cut the concrete and put in a square footing. However, why not just use a steel base plate so as to avoid having to cut the concrete?
Maybe the steel would have to be too thick in order to distribute the load and spread it enough to make it work. Has anyone ever tried this for columns on existing slabs?
Maybe the steel would have to be too thick in order to distribute the load and spread it enough to make it work. Has anyone ever tried this for columns on existing slabs?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com






RE: Steel Baseplate for a Wood Column?
If it is an existing SOG, I just cut in a new footing and install a Simpson post base. If the slab is elevated, then what you propose makes more sense.
Mike McCann, PE, SE (WA)
RE: Steel Baseplate for a Wood Column?
This is correct and the reason why a base plate probably won't do the trick. I've done similar things for construction loads but that involved a grillage of timber members acting as the base plate. Ultimately, the base plate has to be pretty stiff relative to the SOG.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.
RE: Steel Baseplate for a Wood Column?
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Steel Baseplate for a Wood Column?
Think about it this way: Fold a plate, say 24" by 24", so that you have a channel with two equal legs and a depth of 6". That's what happened to work for me the last time I did this, but you can adapt it easily. Quarter inch plate is easy to fabricate and won't be expensive at all. You can also have a welded channel made if quarter inch is too thin for your application.
You need to know a fair amount about the slab to do this right, and should likely consider grout injection as well in order to fill any voids under the slab.
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
Cutting and pouring a new footing is pretty simple. The steel option is a little more complicated.
When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.
-R. Buckminster Fuller
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
Mike McCann, PE, SE (WA)
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
Mike McCann, PE, SE (WA)
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
It gives huge capacities, but I am not totally sold on it yet.
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
1. "Load Testing of Instrumented Pavement Sections - Improved Techniques for Appling the Finite Element
Method to Strain Prediction in PCC Pavement Structures" - by University of Minnesota, Depart. of Civil
Engineering (submitted to MN/DOT, March 24, 2002)
2. "Dowel Bar Optimization: Phases I and II - Final Report" - by Max L. Porter (Iowa State University, 2001)
3. "Guide to Design of Slabs-on-Ground" - ACI 360R-10 - by American Concrete Institute (2010)
4. "Slab Thickness Design for Industrial Concrete Floors on Grade" (IS195.01D) - by Robert G. Packard
(Portland Cement Association, 1976)
5. "Stresses and Strains in Rigid Pavements" (Lecture Notes 3) - by Charles Nunoo, Ph.D., P.E.
(Florida International University, Miami FL - Fall 2002)
How does the Shentu method differ? Do you have any references or sources that I can investigate.
Bottom line though, the trouble of fabricating a special steel base plate coupled with my lack of knowledge of the subgrade, concrete strength and reinforcement have me heavily leaning to just having them bite the bullet and cutting the slab and pouring the new footing. My central post loads at approx. 11,000 lbs are heavy enough that leaving anything to chance would probably not be responsible.
A confused student is a good student.
Nathaniel P. Wilkerson, PE
www.medeek.com
RE: Steel Baseplate for a Wood Column?
RE: Steel Baseplate for a Wood Column?
I'm really interested in Manstrom's point about not knowing the bearing capacity / modulus of the subgrade. Whenever I've done this, it's been with assumed values. I've always figured that the base course would dominate the stiffness and slab flexural stresses would govern the design for most applications.
I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.