2 Bracing using NZS
3604:2011
IN PREPARATION FOR WORKING OUT BRACING REQUIREMENTS FOR A BUILDING,
SOME INFORMATION NEEDS TO BE COLLECTED.
BEFORE STARTING BRACING CALCUALTIONS, the
designer will need to collect the following infor-
mation for the specific building. H for top or single
H for subfloor (Table 5.5)
storey (Table 5.6) h = height of roof above eaves
NZS 3604:2011
Is the building being considered within the scope
of NZS 3604:2011? For this, it must be no more
than 2-storeys and a maximum height of 10 m
from the lowest ground level to the uppermost upper floor level 10 m max. for
portion of the roof. NZS 3604
lower floor level scope
Designs within the scope of NZS 3604:2011
must provide bracing capacity that exceeds the
average
higher of the minimum requirements in NZS ground
3604:2011 for: H for lower of 2
height
storeys (Table 5.7)
○ wind demand – Tables 5.5, 5.6 and 5.7
○ earthquake demand – Tables 5.8, 5.9 and 5.10.
lowest ground point
Wind zone
Some territorial authorities have maps with wind Figure 1 How to work out H and h.
zones. Otherwise, see NZS 3604:2011 5.2.1 to
work out the wind zone. Steps to do this are also
W where roof pitch
on pages 8–10, or consult an engineer. is greater than 25°
When the structure is situated in a lee zone, wind direction along ridge
also see the increased requirements in the notes
at the bottom of Table 5.4.
bracing elements in line with
ridge and wind direction
Earthquake zone
Establish the earthquake zone from NZS
3604:2011 Figure 5.4. For Christchurch, refer to
Building Code clause B1 3.1.2. W where roof pitch
is less than 25°
Floor plan area
What is the floor plan area in square metres at
the level being considered? This is needed for
earthquake demand calculations – the total floor Figure 2 Bracing for wind along the ridge.
4 — Build — Bracing
