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Belt Conveyor Truss Loads on Walkways

Belt Conveyor Truss Loads on Walkways

Belt Conveyor Truss Loads on Walkways

(OP)
Two things, Live Loads and Snow Loads on conveyor box trusses with walkways supported from a cantilevered outrigger for material handling applications. What have you typically used for the walkway live load? I've seen multiple answers ranging from 20-60 psf. In ASCE-7 I think the closest Occupancy or Use in Table 4-1 would be "Catwalks for maintenance access" which is 40 psf. Also, do you include snow load on your expanded metal, gripstrut, or grating conveyor walkways? I know engineers that argued both sides. Just looking for some different opinions here, I have always included snow on the walkway. Thanks.

RE: Belt Conveyor Truss Loads on Walkways

Also check if the material being conveyed can pile up on those walkways.

RE: Belt Conveyor Truss Loads on Walkways

I would use 60 psf as a minimum (ASCE 7-10 "walkways and elevated platforms"). Higher (up to 100 psf) if it is reasonable for workers to carry heavy tools or possibly machinery parts on the walkway.

For industrial purposes, I consider a "catwalk" to be of minimal width which, by it's location, is clearly intended for use only by workers (no tools, parts, or other extra load).

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RE: Belt Conveyor Truss Loads on Walkways

(OP)
I have also seen trusses that had a localized design value and an overall design value for the walkway. For example, design the local members and grating for 50 psf and when looking at the entire truss use 20 psf. To me something like this makes sense because these types of structures might only see max 2-3 people on it at a given time maybe once or twice a day and using 60 psf over the whole truss would be very conservative. Those values were from a specific clients specs and not every client has specs that cover this topic.

RE: Belt Conveyor Truss Loads on Walkways

PolishPower:
Take a look at OSHA Stds. and see how they apply to your situation. I think they talk about 300lb. workers, with 50lbs. of tools and the possibility of several workers in a fairly small space for maintenance work, and the like. I tend to agree with SRE, they could be hauling a motor, or some such, up that conveyor box truss walkway, which is in good part, intended for servicing and maintaining the conveyor. And, at some time you are going have three guys and two motors in a confined area on the walkway, all at one time. That walkway can also retain snow and ice under the right conditions. I might not design the whole box truss for 100 lbs./sq.ft. on the walkway, but I probably would use 100 lbs./sq.ft. for the walkway itself, and then also consider extra loads in some specific areas, or 300-500 lbs. (man and motor) on discrete smaller areas.

RE: Belt Conveyor Truss Loads on Walkways

I would likely design the entire thing for 100psf, and ignore the effects of anything else, i.e. a guy with a motor, snow etc. If designed for 100psf, then you could make the argument that number encompasses the possible other loading situations, i.e. live and snow or equipment being hauled up it.

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