G'day and Welcome back to Buildsum and this is part 3 of the series on calculating wall bracing and in this
video we're going to look at determining the end elevation and then calculate the
racking force that our wind loads are going to put in our building okay so we
going to look at wind direction one first which is blowing onto the long side of our
building okay so this is the elevation of our building now the table at the top
of the table there's a little diagram and it points out that you don't have to
look at the whole wall elevation you only have to calculate from halfway up
the wall okay and there's also a little note at the bottom of the page there
somewhere that says that you don't have to worry about the eaves unless they
stick of more than a meter past the outside of your wall you don't have to
calculate the eaves as well so that yellow area there is basically what
we're going to calculate in this little step so a bit of information
so the roof ptch of 30 degrees we know the building length we know the
widths it gives us a half span of 3.635m which you'll see
why in the moment and our wall height in this case was 2.7 so to work
out the elevation of the wall area this half of the wall we're just going to go
the length of the building times by half the wall height which gives us an area
of 20.034 to work out the roof what I do is I instead of trying to work
these out separately I'm going to cut this triangle off and stick
it on over here and make this one rectangle okay so this length here is
the length of the roof - the half span of the building okay so length of the
roof - a half span gives us 11.205 the height of the roof okay because our
pitch is 30 degrees it's TAN 30 times the half span they
gives us the rise of the roof so that gives us 2.099 and if it times those
threw together 11.285 by 2.099it gives us an area of 23.519
for the roof so then we add the roof and the wall together
that gives us a total area of this elevation of 43.553
metres squared okay so we'll stick that in a little memory bank
somewhere we know that area we can then do wind direction too so the short end
of the building similar process we only have to work out half the wall and the
roof don't have to worry about the eaves so same information so to work out the
wall length or width of the building times half the wall height gave us
9.815 to work out the roof I've done the same as what I did
before cut this bit off stick it over here
make it a rectangle so the length of the building minus the half span gives us
the same number 3.635 we already know the height of the
roof from our previous calculation so 2.099 so times them
together we get a total area of our roof of 7.063 square
meters so the roof plus the walls gave us a total area factor wind direction
two of 16.578 square meters so now we know the areas
of our elevations we can calculate the racking force so remembering from the
the previous video that we had a wind direction one had a wind pressure of
1.1 kiloPascals our area of the elevation is 43.553
we times those together and we get a total racking force acting on wind
direction one of 47.908 so that's basically
kiloPascals acting on that area okay and then we do the same for wind direction -
wind direction 2 had a pressure of 1.2 kiloPascals times that by our elevation
there's the area of our elevation 16.878
okay gives us a total racking force on wind direction 2
of 20.254 so now we know what the force is that's
acting on our elevation and the next video we can start to look at getting
enough bracing into our building to actually resist that force G'day I'm
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