What is the typical way to deal with live loads for movable planters 6

[mistermopar]

I have an 3rd floor exterior courtyard situation (framed floor). The code LL is 100psf for the public area, which is all easy enough, but the architect just introduced dozens of semi-movable planters on us, layed out with various sizes and also in an artistic arrangement (weighing from 490# up to 2300#-see attached pdf). I have ran calcs for all the planter sizes and know the worst case planter weighs in at 193psf.

These planters are intially being laid out by the architect (even though I have it in CAD, they will be undimensioned/uncontrolled in the final prints), and they are technically movable (not easily-but with work the layout could be altered in the future).

This is where I may be overthinking things. I would like to get feedback on whether it is correct practice to go the long route and create load diagrams for each and every joist with the base 100psf everywhere and the 193psf showing where they are drawn by the architect (seems good for lighter floor, but would ignore they can be moved from the original plan and also a TON of drafting/figuring/headaches trying to deal with 'graphic'-only plans), or just add the 100psf and 193psf together (also seems wrong as it is conservative since the planters will always have open walking spaces/paths around them).

Hopefully this is an easy call, I haven't really dealt with this many 'random' objects in such an odd pattern before. I was tentatively thinking bar joists at first design until the architect brought in planters, now I'm thinking full i-beam joists are the way to go if the load jumps to 300psf +/-. Thanks for any help/guidance.

 

[JAE]

You have to figure out what a reasonable "worst case" layout of the planters might be and design for that. And even with a reasonable worst case, I might use a bit larger load factor on the planter loads.

 

[paddingtongreen]

Take the biggest possible load on any one joist from the planters minus 100psf. Design the joists all for 100psf UDL plus the local load from the planter(s).

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[msquared48]

I would design the joists for the 293 figure, but the beams for 100 + 193 factored down to the percent of area covered by the planters relative to the roof area. Seems more reasonable to me.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[wannabeSE]

I would analyze the worst case with a 100 psf uniform load plus 93psf concentrated loads at each planter location. Then compare that with 193 psf uniform load over the entire area. This would bracket the possible solutions to see if being conservative will substantially increase member sizes.

I am assuming that it is unlikely that people or other substantial loads will be ontop of the planters. Also, make sure the planter loads assume the soil is saturated and the planter is overflowing with water(worst case when the irragation control fails or rain water fills the planter).

 

[dhengr]

Just design the whole area for 193 psf, and forget the 100 psf.

 

[mistermopar]

Thanks for the bits of wisdom guys, this list has the most helpful members! I will try several of these ideas and compare the differences btwn them, then decide. Thanks again.

 

[structuresguy]

Ya, i am more into simplification in cases like this. I would just apply 200 psf over everything. Why spend more of your time than needed trying to shave off a few pennies for the owner for something you have no control over? The cost delta will be very small, compared to some of the other approaches discussed (which are all valid, just more work, IMO).

 

[structuresguy]

Oh, forgot to add, do you have any multi-span beams? If so, I would definitely check unbalanced loading, with spans either loaded or unloaded, to find the worst case for shear and bending.

 

[mistermopar]

I do have a single, multi-span support beam, I will make it a point to check for 'skip-loading' as you suggested, thanks for the pointer.

 

[paddingtongreen]

Hmmph. I assumed, because he asked the question, mistermopar didn't want to use the 193/200psf all over.

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[a2mfk]

I'd vote for structuresguy approach. You have no idea down the road that someone's bright idea will not be your worse nightmare. I would rest easy knowing you designed for 200psf LL. Its not that big of an area to sweat a little extra steel tonnage...

You probably have this covered but make sure you design for water ponding up to your secondary drainage system.