Opinion requested re: column web stiffening proposal...
Opinion requested re: column web stiffening proposal...
(OP)
Greetings, esteemed structural engineers:
The issue that I face as a mechanical engineer is one that pertains to the subject matter in the following context.
There is an existing structure utilized to support a hydraulic hammer; the hammer is being replaced with another model of 50% greater mass.
A person who identifed himself as a structural engineer in a recent meeting stated that the columns that support the subject equipment are requied to be stiffened.
His proposal is to weld a 1/4"-thick mild steel plate on the exterior of one (1) side of each vertical column web, (also mild steel), approximately 15-feet in height, thus (in section view):
XXXXXXXXXX -- column flange
XX ------ column web (3/8" thickness)
XXxx
XXxx ---- proposed plate addition, fillet welded
XXxx
XX
XXXXXXXXXX -- column flange
Again, as a mechanical engineer only having limited experience with structures, I thought that this proposed method appeared unorthodox. Additionally, I wonder if the heat added, via whatever welding process will be used in this case, would be detrimental to the web material characteristics --- I expressed my opinions but was esentially told to "mind my own business" and that this practice "is common"...maybe it is? Does the AISC address this in any regard in way of eihter condoning or frowning on this type of web "stiffening"?
Any opinions that you could share with me would be most appreciated...as I have written, my structural experience is not that advanced.
Best Regards,
Pete
The issue that I face as a mechanical engineer is one that pertains to the subject matter in the following context.
There is an existing structure utilized to support a hydraulic hammer; the hammer is being replaced with another model of 50% greater mass.
A person who identifed himself as a structural engineer in a recent meeting stated that the columns that support the subject equipment are requied to be stiffened.
His proposal is to weld a 1/4"-thick mild steel plate on the exterior of one (1) side of each vertical column web, (also mild steel), approximately 15-feet in height, thus (in section view):
XXXXXXXXXX -- column flange
XX ------ column web (3/8" thickness)
XXxx
XXxx ---- proposed plate addition, fillet welded
XXxx
XX
XXXXXXXXXX -- column flange
Again, as a mechanical engineer only having limited experience with structures, I thought that this proposed method appeared unorthodox. Additionally, I wonder if the heat added, via whatever welding process will be used in this case, would be detrimental to the web material characteristics --- I expressed my opinions but was esentially told to "mind my own business" and that this practice "is common"...maybe it is? Does the AISC address this in any regard in way of eihter condoning or frowning on this type of web "stiffening"?
Any opinions that you could share with me would be most appreciated...as I have written, my structural experience is not that advanced.
Best Regards,
Pete





RE: Opinion requested re: column web stiffening proposal...
This is a fairly typical column stiffening procedure. Normally you would do it to both flanges, but it does make sense to do it one side only if the bending causes more compresion in that flange.
For typical structural steel grades the welding does not cause any issues with the steel strength( concrete reinforcement is another matter). The welds each side should be intermittent(i.e. 6"@12" o.c. or similar) to avoid warping the column from heating one side more than the other.
If there is a specific AISC reference for this I am not aware of it.
regards
csd
RE: Opinion requested re: column web stiffening proposal...
RE: Opinion requested re: column web stiffening proposal...
The comments by csd72 and civilperson are pertinent if the bending capacity of the column needs to be increased, but that is not necessarily the case.
RE: Opinion requested re: column web stiffening proposal...
I should have read the OP more carefully. Connecting stiffener plates to the web is not a regular practice, connecting plates to the flanges is.
As hokie66 pointed out, we really cannot give you specific comments without all the details.
csd
RE: Opinion requested re: column web stiffening proposal...
Dik
RE: Opinion requested re: column web stiffening proposal...
RE: Opinion requested re: column web stiffening proposal...
RE: Opinion requested re: column web stiffening proposal...
As you have already said its difficult to say without knowing all the parameters.
RE: Opinion requested re: column web stiffening proposal...
agreed that it does add to the area, but if you assume the controlling "r" does not change (not an unusual assumption in this case) and the area of the plate is about 2 in^2 (0.25*8) then the compressive strength of the column in increasing very little (maybe 50-70 kips). This seems small when considering that the weight of the hammer is being increased by 50%.
Of course, maybe it was overdesigned to begin with and doesn't need much help.
RE: Opinion requested re: column web stiffening proposal...
Once the owner has bitten the bullet and agreed to reinforce the column, I would reinforce, and make it really count, such as boxing the column or other obvious means. The numbers may say that the proposed web doubler is adequate, but I would just make it stronger by boxing it.
This conslusion only applies if we're talking about 1 column, not 300.
tg
RE: Opinion requested re: column web stiffening proposal...
It is hard to agree/disagree with the findings unless more details are supplied (i.e column length, profile, lateral stiffening, etc...).
jetmaker
RE: Opinion requested re: column web stiffening proposal...
RE: Opinion requested re: column web stiffening proposal...
Thank you all, so very much, for providing your valuable comments in way of the subject matter.
As an aside, just today the proposed design for column reinforcement was altered to the "boxed-in" configuration in lieu of the initially-proposed web stiffener.
Thanks again for your time and advice.
Pete