Industrial Building - Paper Machine Operating Floor Load 2

[mck26]

Hello all,
I am tasked with structural design of a conventional steel framed operating floor of a paper machine building. The roof and crane above will be a pre-engineered building. I am unsure on floor loading since I have reviewed similar projects with varying loads of 400 - 600 psf (with areas of 1000 psf for roll lay down bays). Does anyone have experience with heavy loads in paper machine facilities? I am interested in applied live loads, and allowable floor deflection for the operating floor and mezzanines. Also, if there are literature references, please let me know. The paper machine itself is a stand along structure.
Thanks,
M

 

[mtu1972]

I've had experience with paper machine building designs as you are describing. Design live loads will probably not be quantified anywhere but have evolved as the paper machines and buildings have gotten bigger. When I got into the pulp and paper industry (1989) we were using about 400 to 500 psf Live Load plus wheel loads from fork trucks. In addition there were specific laydown areas where the house cranes could lay down some of the heaviest rolls and/or pieces of equipment.

Our company then bought a paper machine building in an adjacent state (mid '90's) and we saw that the operating floor designs there were much more conservative. The concrete slab thickness was much greater than we had been using. Their drawings indicated uniform live loads were about 600 psf and that larger point loads (with impact factors) were used. It was decided that we would use these more conservative assumptions for any future designs. My recollection is that we used 15-ton fork trucks (100% of load on front wheels) with an impact factor similar to bridge design. The fork truck loads generally governed the slab design and the uniform load governed the steel design as it's not possible to have the 600 psf LL and the fork truck in the same place at the same time.

Even though the LL's seem excessive, in preparation for down time maintenance and/or rebuilds those floors will be loaded with equipment being stationed for installation/removal from the paper machine. These loads are not uniform but consist of concentrated loads at random positions. It would be impossible to quantify exactly what is tributary to each beam or girder.

Mezzanines were typically designed for 250 psf LL, or the equipment loads as specified by the supplier (whichever is greater).

Deflections are not typically a problem as the steel required to support these higher loads will typically have sufficient stiffness.

One other concern is lateral loading. The buildings I worked on had the floor beams (on the column lines), as part of the cross machine rigid frame system. With a metal building supplier doing the building shell and crane runway, I would have concerns as to how both and framing system will support the lateral loads.

With the consulting company I last worked for, we had a similar situation where the Const. Manager decided to use a pre-engineered metal building as a value engineering decision. As our company was still doing the process and electrical work, the structural department specified the loads and had the metal building design group integrate the floors (operating and mezzanines) into their system so as to integrate all of the load combinations.



gjc

 

[MikeHalloran]

It's been decades since I was in a paper mill, but I've never seen a paper machine that was a standalone structure. I'd guess that such a thing would have to look like a sturdy Vierendeel truss.

The traditional machine comprises a long row of roll stands, large iron castings supporting the ends of multiple groups of steam-heated rolls over which the paper passes during manufacture. The roll stands are bolted to flats fastened atop beams that surround a central clear opening between the operating floor and the floor below. There may be a few beams spanning the opening, but there are also a multitude of large water supply and drain lines going up and down, plus huge vacuum lines and sag space for 'the wire'.

I don't remember an operating floor being at all springy, even under forklift traffic, so it's definitely not L/360. ... but if the machine has a structure of its own, maybe the floor can be less heavy. ... to a point.

The product is usually very large, very heavy rolls of paper, handled by machinery. ... and occasionally dropped.



Mike Halloran
Pembroke Pines, FL, USA

 

[JedClampett]

I've never designed one of these, but aren't they normally concrete buildings? It just seems that you're either going to end up with a forest of steel columns or such massive columns that they're going to be hard to handle/design.
Plus I would be worried about moving machines running into a steel column. Concrete, not so much.

 

[mtu1972]

Jed - My understanding is that they are generally concrete buildings in Europe but have been steel framed in the US from the earliest days. Many of the old Paper Machine buildings (early 1900's) may have been cast-iron. The paper machine itself have generally been cast-in-place concrete, but that framing is in the basement area of the building. Steel columns are not too big and bay spacings vary from 20' to 30' on center.

What can run into the columns are the fork trucks. I've seen numerous bent column flanges.

gjc

 

[mtu1972]

Should have said Paper Machine Support Framing instead of paper machine

gjc

 

[mck26]

Thank you all for the responses. mtu, you are correct with your assessment. We will use 400 psf (operating floor) and 250 psf (mezzanines). The paper machine framing is supported independently from the ground level and the operating floor is a separate framed floor surrounding the machine.