Stacked HSS Columns at Steel Stair Tower
Stacked HSS Columns at Steel Stair Tower
(OP)
I have a 6 story stair tower which has a stacked HSS column the whole height of tower. The columns are intersected by the landing members. In essence what I have is a HSS6x2x3/8 column and MC12x10.6 landing member. The HSS6x2 columns have end plates at each end and are welded off to the MC12x10.6 landing member. I was thinking that there was some sort of guidelines for stacked columns. I have never used stacked columns like this before. My bottom column has an axial load of 37 kips.
Do I assume that the axial load is transferred through direct bearing on the channel flanges with stiffeners? Do the welds have to transfer any of the axial load or is there a percentage of the axial load that the welds have to transfer? Any help would be appreciated.
Val
Do I assume that the axial load is transferred through direct bearing on the channel flanges with stiffeners? Do the welds have to transfer any of the axial load or is there a percentage of the axial load that the welds have to transfer? Any help would be appreciated.
Val






RE: Stacked HSS Columns at Steel Stair Tower
p.s :the whole weld area (flanges & web) resist the axial load not just the flanges weld
RE: Stacked HSS Columns at Steel Stair Tower
As for the weld, are you asking about designing the stiffener-to-channel flange weld? If so, then you need to design it for the load also from J10.8. If your web crippling, web yielding, and web buckling strengths are high enough, you might not have to design the weld for much, if any, load.
RE: Stacked HSS Columns at Steel Stair Tower
RE: Stacked HSS Columns at Steel Stair Tower
RE: Stacked HSS Columns at Steel Stair Tower
RE: Stacked HSS Columns at Steel Stair Tower
The channels would previously be welded to the face of the column, wherever they occur. Stair stringer and landing loads are generally small compared to the column or channel capacity and the attachment forces are generally small, even for thin wall HSS sections.
Dik
RE: Stacked HSS Columns at Steel Stair Tower
I would be concerned about the overall stability of the whole system when having columns stacked. You are creating knuckles (pinned condition) at the top and bottom of the landing stringers.
RE: Stacked HSS Columns at Steel Stair Tower
RE: Stacked HSS Columns at Steel Stair Tower
"When columns bear on bearing plates or are finished to bear at splices, there shall be sufficient connectors to hold all parts securely in place.
When compression members other than columns are finished to bear, the splice material and its connectors shall be arranged to hold all parts in line and shall be proportioned for 50% of the required strength of the member.
All compression joints shall be proportioned to resist any tension developed by the factored load combinations stipulated in Section A4"
This statement was taken from AISC 3rd Edition. Other editions are similar to this wording.
RE: Stacked HSS Columns at Steel Stair Tower
The stiffeners will be about 1/8" shorter than the distance between the flanges , the welds therefore need to be designed to take the whole load.
You also need to check the length of 'stiff bearing'at the unsupported end of the channel flange between the stiffeners. Use this to check the stress at the base of the column.
Regards
csd