Connection of Steel Beam to Existing Concrete Column - Thru-bolts?

[kpoint]

Does anyone have any tips/comments/advice for connection of steel beams to existing concrete columns with high loads?
Ex. - W36 beam with endplate to 26"x26" reinforced concrete column.

At first, I decided that I could just use a double clip angle with an endplate using post-installed expansion or adhesive anchors. Then, field x-ray surveying revealed that the existing main reinforcement of the square concrete columns had a concrete cover of +/- 4" to 6", rendering the usual mechanical/adhesive anchors inadequate for the heavy loads (90+ kips) at these connections.

So I'm considering thru-bolting through the entire column. What failure modes would you consider for through bolting the endplate through the column with some fishplates on the other side? So far, I can think of ductile steel shear failure and concrete bearing at the anchors. I'm not sure if side blowout is a possibility or whether I can consider the #10/#11 main rebar + column ties as confining it all. Pryout is not possible because it is a thru-bolt but I can't help but think there could be additional failure modes to consider. Maybe steel failure preceded by concrete edge spalling?

 

[BAretired]

Perhaps you could incorporate the principle of the Ellis Shore.

https://www.google.ca/search?q=elli...jkAsbqiwKploHwBg&ved=0CFYQsAQ&biw=785&bih=464

BA

 

[msquared48]

Boy, you know for a condition like this, and with a high load condition, I would feel much more comfortable structurally with adding to the column sectio9n with a portion on which the new steel beam could bear. Just a thought...

Mike McCann
MMC Engineering

 

[kpoint]

msquared48 - I saw you answered to this similar question

http://www.eng-tips.com/viewthread.cfm?qid=302761

two years ago. I had hoped that some new advances had been made in this area.

And to add to the unease of both of us, this load is also reversible up to 35kips upward. Probably the best solution would have been to weld a rectangular steel collar around the whole column with anchors all around but alas field conditions prevented this solution. Any other suggestions?

 

[msquared48]

Sorry. I will keep mum on the subject...

Mike McCann
MMC Engineering

 

[dhengr]

Kpoint:
Since you have 4-6" clr. to vert. rebars, could you saw cut a couple horiz. grooves in the face of the conc. col. 1.2" high and 2.1" deep, 18" apart vertically, for 1" x 2" bars welded to the back of a husky connection pl. The whole connection pl. gets grouted or epoxied onto and into the conc. col. and now your through bolts, or whatever, don’t have to take the shear of 90k down or 35k up; they just have to take secondary loads and moments. On the outer face of the connection pl. put a seat angle for the 90k down and a single shear pl. for the 35k upward.

 

[kpoint]

msquared48-

I hope I did not come off as sounding rude or anything - I was just commenting that you had discussed this similar topic two years ago and was glad that you came by to respond to this thread as well.

dhengr-

Wouldn't that type of connection now be limited by concrete shear failure in what would essentially by plain concrete (since the main rebar and ties are so far inwards?

 

[msquared48]

No worries...Thanks.

Mike McCann
MMC Engineering