WAREHOUSE SHELVING

[gida2]

I've been tasked to analyze the loading capacity (stacking height, unit loading etc..) of our warehouse shelves.

However, from what I found searching the code sites IBC etc... this seems to be an OEM question (unknown) or should be a question for the municipality inspectors (hate to dig up any problems).

Anyone know how about analyzing shelving (rack) units in warehouses? This seems to be a complicated problem since you not only have to look at the dead loads but you also
have to consider the shelving system a multi degree of freedom system under seismic design loads based on the international building codes.

Any help is appreciated,

Thanks

 

[JAE]

Most shelving systems are unique, custom proprietary "products" that individual companies develop and manufacture. To analyze these things structurally would be a fairly complex task. Many times the shapes used to frame the shelves are not your typical tubes, but sometimes are custom cross sections. Field measurements of the cross sections, samples of the materials for lab testing (for material strengths) and a close investigation of the connections would be required.

My first thought would be to find the manufacturer and see what info can be derived from them (if possible).

I do remember some years ago interviewing for a position with a company that made bleachers. (I know, its not shelving but the principle is the same).

The manager said he was looking for a structural engineer to come in and analyze their bleacher systems using "all the latest software". I saw some manufactured samples of the bleachers - very complex, retractable, etc. and figured I'd have a bad time getting to the bottom of it all.

I asked him how they designed the right member sizes since he hadn't "analyzed" it yet. He stated that they just piled up sandbags on mock-up bleachers and once it all fell down they'd add up the weight and get a unit load - if greater than 100 psf then they were A-OK. heh.

 

[mrMikee]

gida2,

There is something in the IBC concerning racks in the seismic chapter for non building structures, or is that now in ASCE 7-02? I'm not sure. I do remember some complaining when the UBC years ago started specifying seismic for racks. Our vendors said they were the experts and the code writers were too conservative. In my opinion however I don't think some of them really know for sure what these structures are good for but continue to make them lighter. And as JAE said they are typically customized shapes sometimes of surprisingly (to me anyways) light gauges, punched full of all kinds of holes for shelves etc.

Despite what the sales guys tell you they do fall down occasionally. Several years ago a large unit load rack building for Quad Graphics, a publisher north of Milwaukee, collapsed for no apparent reason. I'm not sure if the results of the investigation were published.

If I were to analyze existing racks for capacities I would start with looking at the provisions in the IBC and/or ASCE. I would also look for the rack manufacturer’s spec which is published by RMI. My guess is that most of us would come up with something heavier than the OEMs.

If the racks you are concerned about are for heavy loads, are large systems, rack buildings, and so on, I would get a consultant hopefully with rack design experience.

Regards,
-Mike

 

[henri2]

Gida2,

Have you checked Chapters 3 and 4 of FEMA 460--Seismic Considerations for Steel Storage Racks Located in Areas Accessible to the Public?

http://www.bssconline.org/RackWkshp/RackFinalReport/RackGuide.html

 

[gida2]

Thanks for the help. I looked at the IBC and it refers to the RMI code for rack systems. However, I do not have access to this specification.

Since I live in Rhode Island - I think designing it for seismic loads is too conservative and complicated unless you have beam properties and FEA software.

I'll try to come of with a conservative model and recommend capacities based on AISC allowables. I'll verify my results with systems on the market.

 

[mrMikee]

I was looking for something else and ran across this. Could be interesting.

http://www.bssconline.org/RackWkshp/RackFinalReport/Chapter4.pdf#search='pallet storage psf'

-Mike

 

[BSE05]

gida2 I'm located just south of boston, let me know if you need assistance on this. lbombardier@cirees.com