New steel column to existing foundation

[William_291]

I have this steel column that will sit right on the edge of the existing strip footing, which is supporting an existing concrete wall (8m high with lightweight roof). To avoid overturning, I am thinking of having a new pad footing and tie it to the existing strip footing using dowel bars.
If this sounds rational to you, how do I design the dowel bars? (my thoughts are design the new pad footing plus the strip footing (with same length) as a whole footing and work out the bending moment & shear at joints and design dowel accordingly (what about the min. embedment for dowel bars?)

If no, what would you recommend?

Thanks for reading and any suggestion will be appreciated.

 

[hetgen]

why is the existing footing only 350mm [14-in] wide? Is it a ground beam supported on piles?

 

[MotorCity]

I've done this before and its very feasible. In addition to sizing the footing extension for overturning, you will also need to consider bearing pressure and sliding. You can design the horizontal bars using the shear friction concept and roughen the edge of the existing footing that the extension will be poured against. Your biggest challenge will probably be the anchor rods. Unless you use post installed anchor rods in the footing extension, you will have a combination of cast in place and post installed anchor rods. If your sketch is drawn to scale, it does not look like you have a very large edge distance for anchor rods in the existing footing. You may need to consider having the base plate straddle the joint between the new and existing foundation in order to buy a little more edge distance for the anchor rods.

 

[William_291]

Thank you.
@hetgen. It is not on piles. Not sure about the width as the existing one is not done by me. But the load from existing footing is quite small.
@MotorCity, thanks for reminding me of the anchors in baseplate. I am just curious that since I tie the new footing to existing one, will this new footing be part of concrete cone subjecting to breakout and hence edge distance is not a concern even if anchors are installed in existing footing?