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
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