Educate me on loads please...

Started by NM_Shooter, December 30, 2007, 08:23:23 AM

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NM_Shooter

In looking at a link that MtnDon posted to the AWC span calculator, I started thinking about the live load / dead load specs.  I don't know what this means.  I suspect that:

Dead load:  the weight of all the stuff that is nailed down or fixed... decking for the floor surface, carpet, whatever. 
Live load:  people, furniture, appliances, loads that might vary over time. 

Is this right?

For a loft structure that will be used for mattresses on the deck and maybe a duffel bag or two, what loads should I use for typical lofts? 

Thanks,

Frank
"Officium Vacuus Auctorita"

Daddymem

You got it.  I think of dead loads as static and live loads as dynamic, makes more sense to me.

Here is a more thorough explanation:
http://www.uoregon.edu/~struct/courseware/461/461_lectures/461_lecture17/461_lecture17.html

And an article on the tables:
http://www.umass.edu/bmatwt/publications/articles/understanding_loads_using_span_tables.html
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NM_Shooter

Thanks... from one of those links, I see that:

Living room floors L/360 & 40 psf

Bedrooms and habitable attic floors L/360 & 30 psf

Attic floors with limited storage L/240 & 10 psf.

I am guessing that I can use L/360 and 20psf and be fine for my application.  I am going to run the numbers and find out what this requires.

-f-
"Officium Vacuus Auctorita"

John Raabe

For a usable people loft you should use 30 psf live load. The deflection number will determine how much bounce you will tolerate when the joist or beam is fully loaded. This has little to do with strength and is subjective. 1/360 (or L=length/360) = 1" max deflection in 360" or 30'. For a loft w/ exposed decking and relatively short spans 1/240 would probably be fine for most people.
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