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.

 

[TehMightyEngineer]

In old mill buildings I've seen bridge crane rails and supporting beams supported on brick pilasters. It can be done, and certainly you could use the CMU for some of the lateral load resistance.

That said, for a modern design I suspect the most efficient way is to use CMU bearing walls for vertical and lateral building forces and a discrete steel frame for the crane. You could anchor the steel frame off of the CMU walls for lateral stability of the steel frame. 2 tons is a small crane, so really you could make almost anything work.

Any reason they want the CMU walls?

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

 

[SteelPE]

That's pretty much what I suspected.

I have no idea why they want full height CMU. The building was originally proposed with a metal skin. I imagine it has something to do with the durability of the block vs the metal panel.

The next issue is the Korfill Hi-R CMU block they want to use. We always have them remove the foam inserts in cells that are to be grouted, but these blocks look like a portion of the web is removed to make way for the foam insert.

 

[WARose]

I personally would advise against CMU seeing crane loads. I don't know what class of service is (i.e. the number of cycles in the crane's service life), but CMU typically does not perform well under high cycle loads.

 

[TehMightyEngineer]

What's the facility usage/environment?

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

 

[SteelPE]

At this point I am not fully sure how often the cranes will be used. I do know the company does mostly misc metal fabrication focusing on ornamental railings.

 

[EdStainless]

Knowing that our cranes each make >50 moves a day I would suggest against transmitting any load to the CMU, unless you want to build very heavy CMU walls and pilasters to carry the full load.
With small cranes like these the issue isn't the load, it is the starting and stopping shocks.
And small cranes move faster. That is a lot of shaking.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, Plymouth Tube

 

[FLCraneBuilder]

CMU walls Not good for tying crane system back - even at two tons.. the tiebacks transmit reversing loads - and shock and vibration
Tying crane system to Double CMU columns - with Rebar AND solid pour in them - not so bad
must use epoxy set anchors in the concrete - no sleeve anchors

Use steel columns to support crane runway beams, 6" or so clear of the CMU columns.. its probably going to be fine

alternate - go to much heavier foundations where crane columns will go and use what I refer to as free-standing columns (they are in fact moment columns)

Lastly, I've seen my competitors tie bay to CMU WALLS with a big plate inside and outside the wall 23" x 24" or so... I would never do it. Customer asked us to quote an extension of existing system using that approach.. I declined. Some one else did it.

 

[SteelPE]

The thought process would be to tie the diaphragm to the perimeter walls. Lateral loads would be transmitted through the steel columns to up to the diaphragm and down to the foundations. Lateral loads would come out of the diaphragm to the CMU through a perimeter angle bolted to the CMU. No ties would be placed from the steel column to the CMU.

I am not sure if this was properly conveyed or not.

 

[WARose]

The thought process would be to tie the diaphragm to the perimeter walls. Lateral loads would be transmitted through the steel columns to up to the diaphragm and down to the foundations. Lateral loads would come out of the diaphragm to the CMU through a perimeter angle bolted to the CMU. No ties would be placed from the steel column to the CMU.

Sounds to me like the CMU still has to stabilize the crane framing laterally. (Unless the steel framing has some lateral force resisting system on it's own.....or I am misunderstanding something here.)

 

[SteelPE]

Yes, the masonry will resist the crane frame laterally through the roof diaphragm. I guess I am having a hard time coming to terms with the fact that the masonry can not resist the loads from the crane. If these walls were concrete would the answer still be the same? I understand that concrete is a better option than masonry, but the loads we are talking about are not going to be very large. Also, since the masonry needs to be supported by the steel frame, how do we prevent the lateral loads from going into the much stiffer masonry wall system (some sort of angle with a horizontal slot I guess)?

Selling the client on an interior steel concentric brace frame is not going to be easy.

 

[TehMightyEngineer]

I see no reason you can't get CMU walls to take the reactions from a series of 2 ton cranes. Going up into the diaphragm of the roof makes sense; then it distributes the lateral loads to the wall in a more traditional diaphragm-shearwall approach.

I am a little confused when you say the masonry needs to be supported by the steel frame. Why? Isn't the masonry your LFRS? It shouldn't care if there's steel framing there or not.

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

 

[WARose]

If these walls were concrete would the answer still be the same? I understand that concrete is a better option than masonry, but the loads we are talking about are not going to be very large.

Reinforced concrete would be fine.....but masonry (as I said) typically does not do well under cyclic loads. The cracking (to name one thing) becomes an issue over time.

Of course, you say these loads are pretty light....so that might help if you had to have it.

 

[TehMightyEngineer]

I respectfully disagree; how does a masonry wall stand up in the wind then?

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

 

[WARose]

I respectfully disagree; how does a masonry wall stand up in the wind then?

We aren't talking nearly the same number of cycles. (Especially if we are talking Class F type crane service.)

It's certainly up to whomever to try it. But be aware of the risks. I've seen masonry walls have issues in such a setting. (I even got measurements to back it up.)

 

[Ron247]

Without knowing some parameters like crane beam span, crane span, wheel loads, service rating, cycles per day etc., I do not know how to offer any real advice. As I recall, longitudinal crane bracing generally is not very large for the crane capacity you are citing. How well will CMU handle the transverse loading? Why not brace the crane with rods/angle?

Before I opted for CMU based on the current crane design loads, 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. It is generally easier to retrofit steel than CMU in the future for higher loadings.

The only difference I see in crane forces as compared to wind/seismic is the application point. Cranes forces are applied more as point loads at specific locations that change with crane location, direction etc. Wind and Seismic are generally more distributed in nature.

 

[WARose]

The only difference I see in crane forces as compared to wind/seismic is the application point. Cranes forces are applied more as point loads at specific locations that change with crane location, direction etc. Wind and Seismic are generally more distributed in nature.

That's alluding to something else I was thinking about: the anchorage of this thing. SteelPE talked about anchoring the "diaphragm to the CMU through a perimeter angle bolted to the CMU".

Well, how do you transmit high cycle loads to CMU through embedded anchor bolts? It's a big enough headache to transmit those types of loads to reinforced concrete, where research is somewhat lacking.....in masonry, it's really lacking. (And what I have seen doesn't make it look good.)

 

[TehMightyEngineer]

Based on what the OP stated I'd guess this is a class D crane at worst.

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

 

[dhengr]

SteelPE:
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.

 

[WARose]

Based on what the OP stated I'd guess this is a class D crane at worst.

That's still (potentially) 500,000 cycles. Even in reinforced concrete, that would result in a minute percentage of a embedded anchor's static capacity being available for cyclic loads.

All I am saying is (at the risk of ): be careful.