Calculate Wall Bracing – Part 4 – Design Bracing Systems – Nominal Bracing – Wind Direction 1


Gday and welcome back to Buildsum and
this is part 4 in the series on calculating wall bracing and now we’re
going to start looking at designing the bracing systems and the first thing we
can look at as far as that’s concerned is what we call Nominal bracing okay so
just to recap so previously we worked out the, the pressure that it’s going to
be applied to our wall and we know that Wind Direction 1 had an area elevation
of 43.553 square metres which gave us a total
racking force of 47.908 kN okay that’s the force that is going to act on that wall and for wind direction too we had 20.254 kN acting in Wind Direction 2 so now we’re going to look
at actually designing the bracing to resist that force and the first thing we
have to consider is what we called nominal bracing okay so nominal bracing
is basically made up of what our internal lining is so for using Gyprock, villaboard or any type of lining boards our
internal lining makes up our nominal bracing so a couple of rules around that
we can only use nominal bracing to resist 50 percent of the total
racking force in any direction and if there’s a panel size that’s less than
450mm we can’t consider it okay so if you go to a section of wall let’s left
and less than 450mm long you can’t include that in your calculations okay
and it should be evenly distributed throughout the building okay other well
that should be pretty normal okay so the tables in the Timber Framing
Code say that the capacity of nominal wall bracing for single sided walls is
0.45 kN per meter and for walls sheeted on both sides its 0.75 kN per meter so basically what we have to do is work out the length of
those walls in the building then times it by the bracing capacity
that will give us how much resistance the nominal bracing is going to give us
let’s do that with our example house so Wind Direction 1 is down the bottom
here the wind’s blowing against the long side the house so that all the
walls at 90 degrees to the Wind Direction alright will be resisting
that so yeah 90 degrees or the same direction as the actual wind direction, I
guess, now there the walls that are actually resist it, Because the wall the
wind will blow against this wall and these walls will help resist the load if
you know what I mean so the first time we can look at is walls with one side
sheeted only so they are your external walls because in this case there’s a
cavity and then the brickwork okay so I’ve got the two external walls and then
I’ve got these two ones here near the near the door so we just work out the
length of those walls so Wall 1 which is starting on the left-hand side the
long wall, 7m long, Wall 2, which is next to the door
it’s 1.1m long Wall 3, 1.1m long and the Wall 4, 7m long so we just add them up there’s me a total length of 16.2m and we times that by our bracing capacity per metre which was
0.45 for single-sided walls so that gives us a total bracing capacity of
7.424 kN for the single sided walls so then we have
to do the double sided walls so here we’ve got a double sided walls
highlighted so all these walls on this side of the building pretty much the
same length so I’m just going to work them out all together okay so 4 walls,
2.5mlong there then we’ve got this wall here so one wall at 3.5m
long there and then these two, so two walls at 2.4m long gives us 4.8 so again times, 4 x 2.5 gives you 10 1 x 3.5 gives you 3.5, 2 x 2.4 gives you 4.8, a total length of 18.3m 18.3 times our bracing capacity for double-sided walls for two sides 0.75
gives us 13.725kN so we add those two amounts together we get a total resistance from our nominal
bracing in wind direction one of 21.150kN so
we can go back over. so we’ve worked at a nominal bracing of 21.150 so we required 47.908 minus the 21.150 it’s less than a half so
we do not have to worry about the 50% rule so we still require 26.758kN of resistance in when Wind Direction 1
all right so that’s Wind Direction 1 done in the next video I’ll have a
look at Wind Direction 2 G’day I’m back just let you know that
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