Concrete Masonry Walls

[2meterman]

I've got an interesting project where an old elevator is being replaced by a new smaller elevator. The new installation requires the elevator guide rails to be attached to stand off brackets. The brackets are then attached to a Non-grouted CMU Wall

The loading of the bracket is 8,500 lbs with an eccentricity of 28". This gives a large moment at the face of the wall.
The loads are high enough that you can't use expoxy grouted bolts or wedge anchors to secure the bracket to the face of the wall. I decided to thru bolt the bracket to the CMU Wall with a plate on the opposite side of the bracket.

My questions are 1) How do you calculate the shear capacity of the bolt as it bears on the shell of the cmu wall?
2) How do you calculate the tension capacity of the bolt through the face of the wall?

Anybody know of a reference book where I can figure out the capacities of the bolt for shear and tension in the non-grouted cmu wall?

Though it has now occured to me that the CMU wall may not have the structural capacity to take the large bending moment at its mid span in the weak axis.

I await your responses and comments with much anticipation!

 

[DaveAtkins]

Review your loads. I have designed a lot of elevators, and normally the large (buffer) load is a point load to the mat footing at the bottom of the shaft. The guide rails generally take very small loads (a few hundred pounds), at an eccentricity of only a few inches.

DaveAtkins

 

[SperlingPE]

Review loads as indicated above.
Wall may require reinforcing.
There are several ways to reinforce an existing masonry wall.
The easiest is from the top if accessible.
Face shells may also be removed for the installation of reinforcing and grout.
If a very tall wall, both methods may be needed to insure reinforcing gets in the correct location.
Review your conditions. If reinforcing is required, you may be able to install bolts at the same time.

 

[dik]

You may be able to create a separate framing within the existing shaft if you have sufficient space... DaveAtkins is correct about small loads, but you should check for braking loads (they can be significant) and possibly transfer these to the base...

Dik

 

[RareBugTX]

2meterman:

Since there is room, I would design a new steel frame inside, and wouldn't mess with unreinforced cmu that is hard to grout,labor, reinforced, etc, etc.

Frame as required for axial, dynamic load and brace in x and y in plan.(Use up your avaiable space)

I would check the foundation for this new frame.

Again, forget fooling around with existing unreinforced masonry, it is not worth it.

That's my 2 cents.