Reducing Column Effective Length for Added Floors

[NAFTALI-HAKOHEN]

Im designing columns to support an additional 5 storeys ABOVE AN EXISTING CONCRETE BUILDING.

The NEW columns will be adjacent to existing ones (NEW-RED , OLD-GREY, in PLANS BELOW) , and i want to connect the new column to old column (at floor levels)
to reduce effective length from 19 meter column to regular 3.2 meter column.

What force does this connection have to take, how can it be achieved, and how do i guarantee this connection against buckling around both axes?

(In one axis there will be torsional force on any connection...i believe)

thanks for help

 

[jayrod12]

If I understand correctly, you want to connect them to reduce the unbraced length, but do not want to transfer any vertical loads to the existing columns.

Might be prime for some vertically slotted steel connection plates between the two columns on each side of them. In terms of forces required, there's always been that 2% rule, 2% of the compression force, that we use when designing beam flange bracing or top of column bracing in steel. I'd be tempted in this case to look at designing it for 5% just to have some extra capacity kicking around in each orthagonal direction (I would look at each direction separately, not acting concurrently).

 

[dik]

The offset may be tricky with the existing 'final' slab. Can you keep the same column locations for the floor above and design the first new floor to accommodate the transfer forces?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[HTURKAK]

I looked to the section -2 again .. and still trying to visualize the picture.. Pls clarify,
- Is the plan above, for new storeys or existing ones?
- Why is the columns and shear wall is not shown at section -2?
- What is the structural system for existing and new bldg? Flat slab?
- You have added new columns at both sides ( i think, the left columns are box shaped shear walls etc) , but what about the intermediate columns ? (the columns at both sides of 187 cm corridor axis?)..

Pls provide more details to get more valuable responds..

 

[NAFTALI-HAKOHEN]

hi

plan is for existing floor plan, showing new columns on right, adjacent to old ones, and new shear walls that are adjacent to left of structure, these elements 'rise' up above existing 5 floors, and support 5 new floors (6-10)
as can be seen on section. all new vertical elements are marked red.

if maximum axial force in new column is 150 ton, can someone provide a sample detail to connect the new and old columns
to reduce effective length to only one storey height(instead of 6)

thanks

 

[JLNJ]

Is the intent to have two different lateral force resisting systems for the two buildings? Do they work together? Does one lean on the other?

It seems to me that you have more serious challenges here than just the column connection detail.

 

[XR250]

if maximum axial force in new column is 150 ton, can someone provide a sample detail to connect the new and old columns
to reduce effective length to only one storey height(instead of 6)

It concerns me that if you are asking this question, are you qualified to take on a project of this complexity?