Numbers for beam loading calculation

[Eric The Viking]

I'm sorting out my sagging ceilings (see another thread). I've just about got my head around the calculations to spec the beams involved, but need some values for the weight of the structure I'm supporting.

It's lath+plaster ceiling, with 2x4" ceiling joists on 11" spacing. Does anyone have any idea how much this might weigh for a given area? Any units will do, imperial or metric - I'll convert them.

Many thanks if anyone knows this!

Cheers,

E.

 

[jasonB]

Well I can give you

Plaster 12mm thick = 23kg/m2
4x2 joists at 600 cts = 16kg/m2 so about double that for 11" cts
Plus a bit for the laths say 2-3 kg/m2

J

 

[Eric The Viking]

Jason, that's brilliant!

Thanks ever so much.

E.

 

[jasonB]

Thats should have been 6kg/m2 for just the joists not 16

 

[whiskywill]

When I used to dabble in house extensions and conversions I always added 30lbs/ft2 or 146kg/m2 floor loading to any dead load imposed by the materials of construction of the building. If you don't add anything for these loads you could get bounce from anybody walking on the floor above.

This is an American site but has some useful information about dead and live loads. http://www.awc.org/technical/spantables/tutorial.html

 

[Eric The Viking]

When I used to dabble in house extensions and conversions I always added 30lbs/ft2 or 146kg/m2 floor loading to any dead load imposed by the materials of construction of the building. If you don't add anything for these loads you could get bounce from anybody walking on the floor above.

Quite so.

It turns out that the structural load is far less than the dynamic load. I'm allowing roughly 200kg/m^2 for dynamic load at the moment - will see where that takes me regarding the steel to be used.

It's an unorthodox problem, with an unorthodox solution, hence a lot of calculations before doing anything. I'm not looking for close to 'adequate' but instead to find out how big a safety margin I can obtain (there are limitations as to the size of steel that can go in).

Cheers,

E.

 

[Dibs-h]

You might find the following useful,

http://www.oakworthtimberengineering.co ... iteria.pdf

gives the dead loads for some finishes and the live (imposed) loads in most circumstances.

200Kgf/sqm is higher than required - 153kgf\sqm is equivalent to the req'd 1.5KN/sqm

HIH

Dibs

 

[colinc]

hi,

not sure what you are designing, but do remember to check for both strength and deflection - the latter may be the more onerous criteria.

regards,

Colin

 

[Eric The Viking]

Absolutely. Deflection (well, 'bounce' from dynamic loadings) is the key criterion in this instance.

My difficulty is that I'm having to use "unequal angle" steel instead of an I-beam, in a somewhat unorthodox way, and the relevant information (modulii, etc.) isn't as readily available.

I'm getting there though. I'm being very conservative with the numbers, but with cost and size constraints on the steel, I need to be sure it's going to work with a good safety margin.

Cheers,

E.