galvanized tube column base plate

[structSU10]

Has anyone done a check on the base plate for a galvanized tube column? The shop drawings for the base plate showed a solid plate, but the entire inside are of the tube is removed from the base plate to allow for galvanizing (which was not shown on the shops). I would imagine there is more concern than just the bearing area left, but am unsure exactly what that check may be.

 

[BAretired]

I think one concern might be that the base plate cannot develop sufficient bending capacity at the face of the column.

BA

 

[dhengr]

StructSU10:
I agree with BA. Furthermore, on the compressive side of the column, the base pl. bending will pry on the root of the fillet weld btwn. the base pl. and the HSS, it will cause tensile stresses across the root of that weld, never a good thing. On the tension side of the column you do not have the continuity of the base pl. beyond to help distribute the bending moment into the HSS and the base pl. beyond. They should have drilled a drain hole in the base pl., not cut the whole thing out inside of the HSS. Is there a significant bending moment on the column? Does the base pl. bearing check? What are the member sizes, weld sizes, loads and moments?

 

[paddingtongreen]

You don't say what was at the other end of the tube! In the electrical transmission business, the top is left open with a mere air escape hole at the base end, the last part to submerge.

Michael.
"Science adjusts its views based on what's observed. Faith is the denial of observation so that belief can be preserved." ~ Tim Minchin

 

[rowingengineer]

I like gusset plates in situations like this.

http://www.nceng.com.au/

"Programming today is a race between software engineers striving to build bigger and better idiot-proof programs, and the Universe trying to produce bigger and better idiots. So far, the Universe is winning."

 

[dik]

rowing... I try to avoid gussets because it's generally less costly to use a thicker base plate.

Dik

 

[BAretired]

If the entire inside area of the tube is removed, gusset plates may be the only reasonable alternative. It appears to me that the shop erred in removing so much material from the base plate, particularly if it wasn't shown on the shop drawings.

BA

 

[nutte]

Is this for a building, or for a light pole or something similar? This base plate detail is commonly used for poles. The column is socketed inside the base plate, with a fillet weld on top of the base plate and another on the bottom, on the inside.

 

[structSU10]

This is for a building. All the columns in question are leaning columns. HSS12x12's and they technically still have plenty of bearing area left. If you make the argument of a 45 degree projection down from the face of the column through the base plate, even that area alone is adequate for bearing stress.

At first look I thought some lateral columns came into the mix but that wasn't the case. If it were I can imagine many more issues, but in the situation I think I am ok.

 

[JLNJ]

Can you make a 45 degree projection on the outside face when there is no corresponding material on the inside face to balance it out? If you have no plate bending capacity you have just the end bearing on the column cross section. Maybe a little extra if you have a decent column to plate weld.

Wouldn't a couple of small weeps take care of the galvanizing issue? Why cut out the whole plate?

 

[hokie66]

Regardless of the design load, I wouldn't want a 12 x 12 column to be hollow at the base plate. Can you use a loose bearing plate under the whole thing?

 

[structSU10]

We have leveling plates at all columns which should help the situation. There is about a 1/2" or so projection to the inside of the column, so not quite completely cut out.