understanding dead vs live load

[havabeer69]

hey everyone,

building a deck and going through the old engineering stuff i'm just trying to understand the weight ratings of dead vs live load. we're considering changing the decking to FC sheet and tiles.
the dead load is 0.5kPa
the live load 1.5kpa


so does that mean I can have 50kg/m2 of dead/permenant weight
and then 150kg/m2 of non permanent weight on top of it that comes and goes?


I just cant see see a (in theory) 100m2 deck being able to take 15ton of live weight spread over the whole thing??

[Moondog55]

Think of a couple of dozen people headbanging to loud music and jumping up and down in rhythm. 24 * 90kg* the acceleration due to gravity, that's why the live load is in kiloPascals not kilograms

[r3nov8or]

I've been concerned about the total weight too, but then consider the likely use of the deck (for example). At 150kg/m2, it's unlikely every square metre will ever have 2 x 75kg people standing in it at the same time. Even if you have 200 friends around, they aren't going to be comfortable on a 100m2 deck. If the deck has a few tables on it that further reduces the total possible load (unless that's where you dance). It "passively" manages itself :)

[Moondog55]

Decks and balconies have had a habit of collapsing in the past; so the need to built to some sort of minimum safe standard is necessesary
My 90kg per person was perhaps a bit pessimistic, 75 is probably closer to the reality, unless you are hosting a couple of the local rugby teams and we are so old now we no longer dance on tables.

[havabeer69]

it just seems like ALOT of weight that it can handle.

and at what point does overloading the dead load eat into your live load?

[Moondog55]

Good question.
I've always assumed it is when either the total or the localised dead load exceeds 40kg per square metre, four of those afore mentioned rugby players could well fit on a square metre, the design rules have details regarding point loads to cover some things but I'd say they cannot cover all eventualities.
Loading a table that has skinny legs with a full Christmas dinner buffet could easily point load a floor like that