huangyhg

averaging loads
my client wants to use the second floor of a former jail facility (which was designed for a 40 psf live load) for storage of banker's boxes, stacked seven high in a rack system (live load = 146 psf at the boxes).
i produced a report which shows how to lay out the boxes, with wide aisles in between, so as not to exceed the 40 psf live load. the building inspector in the city where the facility is located will not accept this, stating that our state's building code requires 125 psf minimum uniform live load for storage.
any ideas? the client does not want to upgrade the existing floor.
daveatkins
check out our whitepaper library.
i think he's clearly wrong, but now that he's judged it that way, i don't think you have a choice but either upgrade the floor or tell the client that it can't be done.
change gravitational acceleration from 386 in/sec^2 to 386*40/125, lol?
the only other option is to justify it by calcualtions.
either:
1. if you have enough information check that the existing structure works under the loads.
or
2. do a calculation justifying that the moment is no more than 5% above the design moment (there is a 5% increase allowed somewhere but i cant re
i don't have a solution for you, dave, but this is why architects will go to great lengths to label the room anything but "storage".
i agree with the building inspector. the design load is based on the occupancy classification of the floor. if the code requires 125 p.s.f. for storage then that is what the floor should be designed for.
the problem the building official is trying to avoid is future change in what is stored and how it is stored. the current owner, if he recieved approval to follow your shelving plan, at some time in the future, he could narrow up the asiles and add more storage.
after all structural engineers and building inspectors are overly conservative. we always determine the load and double it don't we.
a more important consideration is a future owner who decides that since the room is a storage area that he can load it up to 125 psf because that is what is required by the state code.
an additional comment about engineers; i have been told that after hurricane katrina, that there was a new respect for the engineers that had over designed all the buildings built before the hurricane.
along the lines of jike's post ... maybe define the room as "filing". for my 2c worth, it looks like a reasonable analysis has been completed, creating a reasonable floor plan for comply with the building's limitations
the files are only temporary pieces of furniture, but you know it is going to be used as a storage room, so you are responsible for the future use as a storage room. since your plan was submitted and rejected by the city, there is a record that you were aware of the new proposed use.
i suspect that your client knew of the possible problem from the change of use and wanted to find someone to sign off and minimize or eliminate his liablity.
dick
you didn't state the building code here - but in the ibc, section 1607.2 it states: "for occupancies or uses not designated in table 1607.1, the live load shall be determined in accordance with a method approved by the bulding official."
you could probably successfully convince the building official that your bankers boxes, stacked as required by you (and the layout permanently posted on the wall) is not a use designated by the table - i.e. the 125 psf light storage isn't what you are technically doing.
however, you would then need to convince the official that your layout, and the resulting 40 psf average live load, is ok.
i think the building inspector is absolutely spot on. neither you nor the inspector can control how this 40 psf (2 kpa) floor is used by this owner and, perhaps more importantly, future owners.
it is not an impropbable sceanrio that a future tennant or owner will increase the amount of storage on that floor 'assumming' it it fit for that type of loading, i.e. 125 psf (6 kpa).
how did you get the 40psf average load? if your bankers boxes are more than 40psf and you apply the 40psf between them then you technically get more than 40psf!
i think you guys are missing what daveatkins is doing here.
i would agree that the building official is interpreting the code the right way for this application, but the previous posts are assuming the space is being designated as "storage".
consider a typical office building where the original design for the second floor is 50psf (office space). a future client wants to use a portion of the room for storing boxes. does this mean that the original design should have been for 125psf? we can't assume what future tenants/clients will use the space for. daveatkin's client is using this room/space for storage, but may not be reclassifying the space. a future tenant could use it for anything.
for this application, the current tenant should be able to use this space to store the boxes with an approved plan from an engineer while satisfying the building inspector. if a new tenant moves in, he/she has a responsibility to verify the space has the capacity to be used as storage or whatever use he/she intends.
i think daveatkins is on the right track as long as the client understands that deviation from his layout plan could spell disaster for the floor framing. with that said daveatkins needs to weigh his liability if the plan isn't followed to the t.

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