Lateral sliding connection of masonry wall to steel moment frame 1

[Temporary]

I'm designing a 4-story steel moment frame building with masonry walls. Masonry is outside of steel frame so CMU is not inbetween the columns. Since I'm tying a rigid CMU wall to a very flexible steel moment frame, I need a connection between the CMU and slab (or steel beam) that will allow sliding (about 1" to 1.5" at very top) parallel to the wall, but hard support perpendicular to the wall. Durowal's sliding connections are only oriented to allow vertical sliding, not horizontal. Preference would be not to use a custom built steel connection every so many feet, but it looks like that is the only way at this point. Does anyone have any suggestions?

I'm not the project manager making the final say about what system to use. Moment frame rather than shearwall was mandated due to the 1st floor from wall jutting out so the masonry wall from 2nd floor through roof rests on the steel beam line. Project is in South MS, seismic will likely control in one direction and wind in the other.
Concrete slab on metal deck on steel bar joists on steel beams. CMU is NOT load bearing, only connected for lateral.
P.S. this is a temporary account until mine is fixed, hence the name Temporary.

Thanks much.

 

[apsix]

The only response I can make is that it is a novel structural approach to me. How is the relative movement accommodated at the intersection of the masonry walls parallel and perpendicular to the frame movement?
Don't you have stair and lift shafts you can use to stiffen the building?

 

[msquared48]

Sounds to me like you have a steel moment frame building encased in a CMU exterior shell.

For the localized condition you describe this could be done with a steel angle welded to the frame with slotted holes in the direction of the frame at the CMU wall, or vice- versa.

The problem comes in trying to solve the global solution of the problem. What do you do at the corners of the building? The corner of the frame wants to move parallel to itself, but cannot as it is restrained by the CMU.
It appears that the CMU cannot be continuous around the corner, but must have a gap that allows movement in two directions.

Mike McCann
McCann Engineering

 

[Temporary]

Yeah I thought about that nasty little issue of the corners, but I thought I'd try to slay one giant at a time. I don't have any real intelligent notions as of yet about the corner connection, but after many phone calls to various associations and Durowal, I got a fellow who said they can customize one of their standard wire ties. The peice that connects to the steel frame is vertical to allow for vertical adjustment... he said they could twist the end of the fairly triangular tie, then lay the piece on the steel horizontal and would provide a full 3.5" (1.75" each way) of sliding. The capacity is actually not reduced since pulling the piece on the steel member out (bowing out) is the failure mechanism and this is not really affected. It would increase the cost by maybe in the magnitude of a factor of 5x's, but that would still be way cheaper than a custom steel connection, which is what I was avoiding.
I think we are actually going to be able to go back to a shear wall system for this project (found out after talk with Durowal and posting this question), but it makes for an interesting bit of knowledge for possible future situations. I'll still check back to see if anyone else has any other ideas... would be interesting to see other engineer's approaches.

Thanks for the input guys.

 

[Unionmason]

Temp, what about just installing the wire triangle part of the masonry anchor backwards? I.e. the wider base centered in the slotted wall mounted bracket instead of in the bed joint. Extra ties might have to be used to achieve equal strength as standard installations Another method would be to bend the triangles open to a 'C' shape with the wall bracket centered on one of the unbent (straight) sides so the flimsy wall could move in two dimensions w/o shaking the masonry apart. Thirdly add enough ties until the the masonry will move with the structure in the quake event eliminating the two axis wall ties.