storage floor load requirement

[LutzTD]

I want to build a storage balcony in the phase 1 portion of my garage. I want to use all steel, termites ya know, anyway, I am a BSME but what I dont know is what loads should I calculate for the floor? Ive seen commercial storage floors at 150#/sf with an additional 40#/sf for live loading. If I size it for 200#/sf with a 4x safety factor am I in the balpark? There are a couple 20ft long W14x30 on craigs right now for cheap, I could bolt these in the middle and get a 40ft clear span, but Id like to understand the real requirements

 

[WWIIjeep]

What are you intending to store, and how much? The answer to that will drive your floor loading calcs.

 

[rsanter]

not enough information
what is the intended use?
if you are going to store cylinder heads standing on end then you are falling short. if you are going to use it for general storage then thats another story

bob

 

[mellamoesrico]

http://www.engineeringtoolbox.com/beam-stress-deflection-d_1312.html

Here is a beam load/deflection calculator. Site also has instructions/examples, tables for looking up various structural beam properties used in the equation, etc. Even cooler is that the site is a plugin for google sketchup.

 

[mellamoesrico]

http://faculty.arch.tamu.edu/anichols/index_files/courses/arch331/NS15-2beamdesign.pdf

http://www.etcs.ipfw.edu/~dupenb/ET_200/Beam%20Design.pdf

Here are some more details on the calcs. Just off the top of my head, the beams you're looking at on CL could hold a lot over a 20' span, depending on how close together you space them.

 

[LutzTD]

sorry i have been travelling. as for item stored, it will be general items and spare parts, not much engine and drive train parts but likely body panels and things that take up a lot of space inthe shop that need to out of the way.also would be supplies likesome paints, sandpaper, fiberglass,maybe some aluminum sheet. what I was looking for is just general storage industrial floor loading and live loading, some kind of braek down ofwhat static loads are to be applied. Ive looked at span tables but I want to understand the numbers behind the spans they say are allowable because when I calculate it out based on a max deflection of L/1200 and stress the span tables seem ultra conservative and dont list over 30 feet, I would like to understand what other factors they are considering. my storage loft will by 8or10x40 with one of the short sides supported by the concrete wall

 

[LutzTD]

http://faculty.arch.tamu.edu/anichols/index_files/courses/arch331/NS15-2beamdesign.pdf

http://www.etcs.ipfw.edu/~dupenb/ET_200/Beam%20Design.pdf

Here are some more details on the calcs. Just off the top of my head, the beams you're looking at on CL could hold a lot over a 20' span, depending on how close together you space them.

thats good stuff thanx

 

[akdiesel]

From what read you want to connect two 20' beams together by means of bolts to have an unsupported span of approx 40'? I am no engineer but I would say that would not be a good idea. Just thinking of some steel support beams I have seen as I too would like to get a span like that for a 2000# trolley lift and would require an extremely large I beam.
I would try to put at least one support at the bolted area if possible. Lots of stress on the bolts and / or welds for the gussets.

 

[blkhonda1991]

sorry i have been travelling. as for item stored, it will be general items and spare parts, not much engine and drive train parts but likely body panels and things that take up a lot of space inthe shop that need to out of the way.also would be supplies likesome paints, sandpaper, fiberglass,maybe some aluminum sheet. what I was looking for is just general storage industrial floor loading and live loading, some kind of braek down ofwhat static loads are to be applied. Ive looked at span tables but I want to understand the numbers behind the spans they say are allowable because when I calculate it out based on a max deflection of L/1200 and stress the span tables seem ultra conservative and dont list over 30 feet, I would like to understand what other factors they are considering. my storage loft will by 8or10x40 with one of the short sides supported by the concrete wall

L/1200 is slightly ridiculous, 150psf deadload +40 liveload should be sufficient based on what you are storing, round it up to 200psf. allowable deflection shouldnt need to be any higher than L/360.

 

[LutzTD]

L/1200 is slightly ridiculous, 150psf deadload +40 liveload should be sufficient based on what you are storing, round it up to 200psf. allowable deflection shouldnt need to be any higher than L/360.

I thought so too but it was in one design guide. so with 200#/sqft split with 2 beams supporting the floor I am calculating like .010" deflection with the 40 span W14x30 25200# on a 29000000E steel beam with 2 beams bolted together mid span once I get the layout done I will add aa suport likely sokitting the span 10/30

 

[mellamoesrico]

I doubt you will have 150 lb/sqft of dead load. Even those 14" W beams, plus joists spaced every 16" from beam to back wall (how long?) plus double-layer of 3/4" plywood decking on top of the joists probably won't get you up into that load range. I wonder if the 150 lb/sqft dead load number you got could have been for a steel deck with cement poured on top of it for sound & vibration dampening (common in industry).
Trying to splice the two beams together without a post under the connection is much harder to do w/o losing a lot of strength. That would require more engineering $ to design the joint than just buying longer beam(s). If you must have the vertical support post off-center, I would get beams that will reach from the post to the side walls w/o any splices.
It sounds to me like a call to your local steel supplier is in order. The engineers at those places do these calcs all day. As long as you agree to buy the materials from them, they will run the calcs for you, size the beams to minimize overkill (avoid wasted $ on oversized beams) and (probably) even supply a stamped drawing with your purchase.

 

[72Anthony]

Bolting two 20 foot beams together without a column underneath, resulting a 40 foot span: I would be worried about the shear strength of your bolts. The maximum moment occurs at the mid point.

Im just guessing but maybe that 1/1200 deflection criteria is for some kind of percision machinery.

 

[LutzTD]

I doubt you will have 150 lb/sqft of dead load. Even those 14" W beams, plus joists spaced every 16" from beam to back wall (how long?) plus double-layer of 3/4" plywood decking on top of the joists probably won't get you up into that load range. I wonder if the 150 lb/sqft dead load number you got could have been for a steel deck with cement poured on top of it for sound & vibration dampening (common in industry).
Trying to splice the two beams together without a post under the connection is much harder to do w/o losing a lot of strength. That would require more engineering $ to design the joint than just buying longer beam(s). If you must have the vertical support post off-center, I would get beams that will reach from the post to the side walls w/o any splices.
It sounds to me like a call to your local steel supplier is in order. The engineers at those places do these calcs all day. As long as you agree to buy the materials from them, they will run the calcs for you, size the beams to minimize overkill (avoid wasted $ on oversized beams) and (probably) even supply a stamped drawing with your purchase.

yeh im pulling numbers from all kinds of sources. the 150psf was a load spec for a commercial storage floor, It would be on top of the weight of the construction. I would love to do a poured floor with lightweight concrete.

also I have not priced steel from a source, I know my roof would have been about 50% the cost had I bought materials my self, not sure about where the markup happens. My hope was to catch a used beam on craigs for 10cents/pound, Im not crazy about the bolted idea either, likely ill wait till the right beams show up, theres a 8x4-5/16 wall tube on there right now which my clacs show is ok too, there are two of those 40 feet long which would be plenty strong with good safety factor at 200psf at 40ft span

 

[mellamoesrico]

I envy the selection of stuff on Craigslist in your area. You down near Miami?

How deep are you gonna make the 40 ft wide loft?

If you didn't already have a roof, this loft would probably be made using attic trusses. The normal spec for them is 40 psf live load supported by 10 psf dead structure, for a total load of 50 psf.

Are you sure its necessary to multiply that load by your stated Factor of Safety of 4, to come up with a total load of 200 psf to use in your sizing calcs? Seems overly conservative, considering that deflection is the limiting case here. The strength calculation probably still shows a Factor of Safety of around 2 when the deflection limit is reached.

It would be nice to know what factor of safety they use in the industry, and wether it is applied to the Strenth calculation only, or also to the deflection calculation as well.

 

[LutzTD]

I envy the selection of stuff on Craigslist in your area. You down near Miami?

How deep are you gonna make the 40 ft wide loft?

If you didn't already have a roof, this loft would probably be made using attic trusses. The normal spec for them is 40 psf live load supported by 10 psf dead structure, for a total load of 50 psf.

Are you sure its necessary to multiply that load by your stated Factor of Safety of 4, to come up with a total load of 200 psf to use in your sizing calcs? Seems overly conservative, considering that deflection is the limiting case here. The strength calculation probably still shows a Factor of Safety of around 2 when the deflection limit is reached.

It would be nice to know what factor of safety they use in the industry, and wether it is applied to the Strenth calculation only, or also to the deflection calculation as well.

I am being conservative, since the materials seem to be popping up used to allow me some choices to go extremely strong I will do it. If I was buying new out of pocket maybe not so much. Im hoping someone here wil shed some light on why the span tables go to such big beams for shorter spans.

 

[LutzTD]

I am being conservative, since the materials seem to be popping up used to allow me some choices to go extremely strong I will do it. If I was buying new out of pocket maybe not so much. Im hoping someone here wil shed some light on why the span tables go to such big beams for shorter spans.

anyone have any input on span table values?