Industrial Building With Interior Cranes 4

[SteelPE]

I am currently in the beginning stages of designing a small industrial building (80’x80’). The building is an addition to an existing structure an is to have an eave height of 19’-8”. The client is currently looking to place 3 2-ton bridge cranes inside the building (I say currently because that may change). The client is also looking to use a CMU skin on the outside of the building.

My question is in regards to the CMU skin. Is there any reason why we can’t utilize the skin to resist the lateral loads for the building (wind, seismic and crane)? I have told the client that if they desire cranes then the CMU can not be load bearing (as you will need the perimeter steel to support the cranes). I have designed a few crane buildings but I have never had one with an infill masonry skin around the perimeter.
I have a few other issues, but lets start here.

 

[kissymoose]

aaaaaand I'm stealing that emoticon. That's amazing.

 

[TehMightyEngineer]

I would think it could be done if you pay particular attention to the detailing, reinforcing, grouting, consolidation and constructing of the pilasters on which the crane rail beams rest.

I'm confused, I was never talking about supporting the crane rails on pilasters (thought as I noted in my first reply to OP, I've seen it done in old mills). My concept was always to support the crane rails on steel gravity columns that tie into the roof framing for lateral support. The CMU walls are your lateral force resisting system and building facade.

Even at 2 tons, trying to support the vertical reactions of the crane off of the CMU is definitely inadvisable.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[TehMightyEngineer]

I should also clarify that while I'm still onboard with OP providing crane stability via the CMU walls, it really is much more efficient to brace the crane framing via cross-bracing. Unless there's extreme value to the client in avoiding that I'd go that route first.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[SteelPE]

How do you guys get quotes in here? Let me see if I can do it.

I would question the Client about their thoughts on the future. If they think they will go to larger or more severe cranes in the future, that is what I would base my decision on.

I understand your point, but if a client tells me to design his building for a 2-ton crane I design his building for a 2-ton crane. Retrofitting in the future for an increased in crane size is an enormous issue regardless of what we are using at the perimeter to resist lateral loads.

The problem with CMU components supporting these crane rails is likely, that with the fairly light compressive loading, but a moving load with many cycles and lateral components too, is that this type of loading could rattle the conc. blk. to pieces. I would think it could be done if you pay particular attention to the detailing, reinforcing, grouting, consolidation and constructing of the pilasters on which the crane rail beams rest. They will not be made of typical (single) pilaster blks. The problem is that the light loads don’t induce much compression which would be helpful in this case, and the conc. blk. just do not handle the induced tensions very well without cracking. So, in effect, you want to build a good strong conc. col. using the conc. blk. as formwork, and then tie this into the rest of the wall, and the roof diaphragm for total stability.

I am not supporting the vertical loads of the crane with masonry pilasters, I am using bracketed steel columns (the building will have a steel frame). Lateral shear loads generated by the crane would be resisted by the masonry perimeter walls as transmitted by diaphragm of the steel decking.

 

[bones206]

You mentioned that the building was originally to have a metal panel skin... what was the lateral system for that concept before the CMU was substituted?

 

[SteelPE]

The project was suppose to utilize a inverted V concentric brace frame system when the building had a metal panel skin.

 

[bones206]

Seems like the structure would be cheaper, more efficient and better performing with the braces and metal wall panels. I'm curious why the owner would push for insulated CMU when it will probably cost more, insulate less, take longer to build and possibly crack from the crane usage.

 

[SteelPE]

IDK, I just know the switch from metal panel to CMU came through on the last set of architectural drawings. On this project I am slightly insulated from everyone so it's not easy to get answers. From what I was told today the cranes may just utilize chain hoists vs motorized hoists (again, something that I have never head of before)..... and the cranes are more there for "convenience" rather than necessity. I am not sure how I will proceed, but I am trying to convince everyone to keep the steel bracing.

 

[TehMightyEngineer]

I honestly wonder if they even need a full bridge crane. A pair of monorails down each bay with chain hoists sounds like what they really want. Cheap and easy.

Ian Riley, PE, SE
Professional Engineer (ME, NH, VT, CT, MA, FL) Structural Engineer (IL, HI)

 

[Sawbux]

Are you in a seismic zone? Using a brick exterior would significantly increase seismic loads on the steel frame building. Also the masonry may crack if it relies on the steel frame for top support.


For the cranes, look at Gorbel or Spanco free standing bridge cranes. They are supported from the floor.

 

[GC_Hopi]

Concrete columns are also an option for supporting the crane. It might be worth consideration if the owner is more accepting of concrete.