Column Encsed in Masonry- Unbraced Length?

[ToadJones]

I have a series of columns with over half of the column encased in masonry. That is, one entire flange and nearly all of the web is encased in masonry with only the one flange exposed to the interior of the building.
Question is, does the masonry provide support as far as unbraced length in the weak direction? Strong direction?

I'm inclined to say that the masonry provides weak axis support only.

 

[hawkaz]

I hesitate to do this type of connection. With thermal or building movement the column will expand/react differently than the masonry wall. The masonry will inevitably crack.

I prefer to put a gap or expansion joint material around the column.

 

[ToadJones]

I agree.
However, this is not a new building.

 

[csd72]

I would check to see if the brick is tight up against the column web (if you can), and also that thereis not any signs of deterioration around the column.

I have treated it as restraint in the past.

 

[JAE]

A typical detail for this condition is where wire or crinkle strap masonry ties are attached to the column at intervals and extend into the mortar joints. This creates a degree of bracing to the column in the weak action for column capacity calcs. I'd worry about the robustness of the wall to prevent twisting so the Lb length for bending might not be fully provided by the wall...perhaps to some minimal degree.

But the wire ties have more of a tension-only capacity. If there is wall on both sides, I'd tend to consider the wall as a column bracing element. If the wall is only primarily on one side (the column is very near the end of a wall) then I'd be more conservative and ignore the wall.

 

[a2mfk]

Agree with JAE and others... Do you really need the bracing to get it to work? If yes, maybe you can add a more robust attachment to the wall to ensure proper bracing?

 

[ToadJones]

It has been about a month since I looked at the building.
I was actually shocked at how perfectly tight the masonry was to the building column web.

 

[ishvaaag]

Essentially you are describing one of the biggest notional failures of how the steel buildings were being constructed in Spain till the early 70's. They had columns with battens, and inside the pair of the simple members constituting the column a short stub of double tee or channel, or worse, even on the battens, continuous beams were supported. Essentially, so, a gravity system. In the best cases (most fortunately by the seventies') a 3 plane system of bracing was added, but in the cases that not, it was the masonry itself -and floor system, sometimes just laid unattached on the beams- what was providing for stability and whatever bracing available. Essentially they were replicating ways of the past, where no clear assignment of the structural function was given to the components; most reform works' parties were and are unaware of the proper functionality and it is one of the causes of accidents happening at such works.

In all, for the worse cases, what supported was complementing the ability of what supporting to provide the expected functionality. Exactly like in your case. Anytime that I have been practicing, and now by the code in the final report for the construction, the works that need to be kept untouched as components of the structural safety and integrity must be identified in the document and postmarked in-situ.

 

[peconsultant]

Even though the masonry is "perfectly tight" to the column web, I wouldn't count on any restraint unless there is some sort of mechanical anchorage between the steel and the masonry.

 

[MikeHalloran]

I'd guess the perfectly tight part is spackle backed by styrofoam.



Mike Halloran
Pembroke Pines, FL, USA

 

[peconsultant]

Adding to my above post ... the masonry would have to be anchored at the top and bottom. Otherwise, you are just getting a stiffened section (again, assuming that there is a mechanical attachment between the masonry and steel).

 

[hokie66]

If it is an old building with brick masonry built tight against the column on both sides, I think the column is well braced in the weak axis direction. If concrete masonry, then a lot depends on the detailing.

 

[ToadJones]

Hokie- yes, it is brick laid extremely tight/neatly into the column web. The masonry work on this building is impressive. The craftsmanship is great, almost hard to believe.
Definitely not styrofoam and caulk.
It is an old building and there is no bracing on the columns in the weak direction of the columns/building on the original drawings. I'm just starting to look at this building, so maybe I missed something so these are jsut thoughts at this point, but it appears the lateral stability of the building in the direction opposite the main bents is basically a masonry shear wall integral with the columns.