# Calculate Wall Bracing – Part 2- Determine Wind Pressure

G’day and welcome back to Buildsum and
in this video which is part two of the series on wall bracing we’re going to
work out the wind pressure for both our wind directions
okay so paragraph 8.3.4 racking force says that the
racking force of a building shall be determined by using the method outline
but in this clause all by using the alternative method in appendix F now the
alternative method is a simplified procedure and it’s going to give you a
more conservative or safer solution so it’s going to require more bracing so
we’re going to go with the the more economical type which would be this one
here so the total racking force for each story or level of the building shall be
the product of the projected area of elevation of the building multiplied
multiplied by the lateral wind pressure determined from Table 8.1 to 8.5 the total racking force shall be calculated in both
directions long and short sides of the building so
that’s why we do two wind directions one on the long side one on the short side
okay so the formula to work out wind pressure is done in kilonewtons and the
formula is the total racking force equals the area of elevation in square
metres times by the lateral wind pressure in kiloPascals which is what
we’re going to work out now I’ll show you how to look that up okay so it said
there’s four tables or five tables the table 8.1 is for single
story or upper story or the upper of two-story buildings lower story and
subfloor of a single story or two story all vertical surfaces gable ends ski and
ends flat wall surfaces so if your buildings got a flat gable or a skillion
you would use 8.1 8.2 is a single storey or up a storey of
a two-story building the long length of the building with with a hip or gable
end which is going to be applicable for us for our long side of the building 8.3
the lower storey or subfloor of a single single storey or two storey okay so this
is for the bottom floor on a two-storey house long length for the building so
it’s not going to apply to us 8.4 a single story or upper
story of a two-story building short end of the building so this is again I’ll
apply to us that we’re going to use 8.4 and 8.5
again is for the short end of the building on the lower storey of a
two-storey house so you have to make sure you pick the right table for the
building that you’re actually going to be working this out on so we’re going to
use 8.2 for our long side and 8.4 our short side so this is the table
basically okay so you need a little bit of information, you need to know what
your pitch of your roof is and you need to know how wide or how long your
building is okay so this is Table 8.2 which is we’re going to call
wind direction one and this is acting on the long side of the building all right
remembering that our building the building that I’m using for this series
it had a pitch of 30 degrees it was 14.840m long and 7.270m wide okay so this is the
example so if we look at the column four thirty degrees and then course we’re
looking at the long side of the building and our buildings 14.8
we’re gonna have to use 15.0 so we end up with a wind pressure or lateral
wind pressure for this building of 1.1 acting on the long side of the building
alright so we’ll write that down somewhere so 1.1 and then we’ll look at
the short side so the short side we’re using 8.4 this will be our wind
direction 2 short side the building similar table just different figures
again 30 degree building so we’re going to use the 30 degree column and our
buildings only 7.2 wide so we’ll have to use 8 can’t go under so we use 8 as
they’re building widths and we get a lateral wind pressure on the short side
of 1.2 ok so we can write those down wind prep direction 1 we’re going to get
a lateral wind pressure of 1.1 m kPa and wind direction 2 we get a lateral wind
pressure of 1.2 kPa okay so now we know what pressure the wind is going to put
on those elevations we can in the next video we’ll work out the area of those
elevations and then we can calculate our tracking force today I’m back just let
you know that if you like this video you can subscribe to my youtube channel or
you can follow me on Facebook so you don’t miss out on more great videos