Transcript SECTION 8 - RACKING (BRACING) AND SHEAR FORCES WEEK 13

SECTION 8 RACKING (BRACING)
AND SHEAR FORCES
WEEK 13
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
1
8.1 GENERAL
Permanent bracing shall be provided to
enable the roof, wall and floor framework
to resist horizontal forces applied to the
building (racking forces).
Appropriate connection shall also be
provided to transfer these forces
through the framework and subfloor
structure to the building’s foundation.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
2
8.1 GENERAL
Where required, bracing within the
building, which normally occurs in
vertical planes, shall be constructed into
walls or subfloor supports and
distributed evenly throughout.
Where buildings are more than one
storey in height, wall bracing shall be
designed for each storey.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
3
Gable end bracing
Cross or sheet
bracing
Cross or sheet
bracing
Subfloor cross-bracing,
cantilevered stumps or
bracing wall
Wind
FIGURE 8.1 VARIOUS BRACING SYSTEMS
CONNECTING HORIZONTAL DIAPHRAGMS
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
4
NOTES to Figure 8.1
1. The wind force on unclad
frames may be equal to or
greater than those on a
completed clad or veneered
house.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
5
NOTES to Figure 8.1
2.Horizontal wind (racking)
forces are applied to external
surfaces that are supported by
horizontal or near horizontal
diaphragms. Diaphragms
include roofs, ceilings and floor
surfaces including their
associated framing.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
6
NOTES to Figure 8.1
3.Each horizontal diaphragm
transfers racking forces to lower
level diaphragms by connections
and bracing. This continues down
to the subfloor supports or
concrete slab on the ground,
where the forces are then resisted
by the foundations.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
7
Wind produces horizontal
loads on buildings that
must be transmitted
through the structure to the
foundation.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
8
• In a conventionally
constructed house these
loads are transmitted to the
ground by a complex
interaction between the
walls, ceiling/roof structure
and floor structure.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
9
• The ceiling and floor form
large horizontal diaphragms
and normally play an
important part in this action
as most walls rely on
support from this ceiling or
floor diaphragm to prevent
them blowing over.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
10
The wind forces are transmitted to the
ceiling diaphragm from the walls and also
the roof. They are then transferred through
the ceiling diaphragm to the bracing walls
that transmit them to the floor structure,
foundations and then into the ground.
Without
ceiling
diaphragm
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
With
ceiling
diaphragm
11
Wind forces on the roof are
carried to the ceiling sheeting
(ceiling diaphragm) via the roof &
ceiling framing
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
e
Wind forces on the bottom half of
this wall are carried direct to the
ground via the wall framing, slab
& footings.
ac
Br
Wind forces on the top half of this
wall are carried to the ceiling
sheeting (ceiling diaphragm) via
the wall & ceiling framing
Ceiling diaphragm
Wind forces
transfered to the
'ceiling diaphragm'
are carried down to
the slab and the
ground via bracing
walls.
12
Wind forces on the roof are carried
to the ceiling sheeting (ceiling
diaphragm) via the roof & ceiling
framing
Wind forces transfered to
the 'ceiling diaphragm' are
carried down to the ';floor
diaphragm' via bracing
Floor diaphragm
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
ce
ra
Wind forces on the bottom half
of this wall are carried direct to
the ground via the wall framing,
slab & footings.
B
e
ac
Br
Wind forces on the top half of
this wall are carried to the
flooring (floor diaphragm) via
the wall & floor framing
ce
Wind forces on the bottom half of
this wall are carried to the
flooring (floor diaphragm) via the
wall & floor framing
a
Br
Wind forces on the top half of
this wall are carried to the ceiling
sheeting (ceiling diaphragm) via
the wall & ceiling framing
Ceiling diaphragm
Wind forces
transfered to the
'floor diaphragm'
are carried down
to the
slab/footings &
ground via
bracing walls.
13
8.2 TEMPORARY BRACING
Temporary bracing shall be
equivalent to at least 60% of
permanent bracing required.
Temporary bracing may form part of
the installed permanent bracing.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
14
8.3.1 General
Bracing shall be designed and
provided for each storey of the
house and for the subfloor,
where required, in accordance
with the following procedure:
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
15
• Determine the wind
classification
• Determine the wind
pressure
• Determine area of elevation
• Calculate racking force
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
16
To calculate the number
of braces required for wall
bracing, the required racking
force (kN) is divided by the
capacity of each brace.
NOTE:
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
17
The total capacity of each
brace is equal to the
length of the brace
multiplied by its unit
capacity (kN/m) as given
in Table 8.18 (pg 141).
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
18
For example:
a diagonal brace Type (c)
(as per Table 8.18) has a total capacity
of 1.5 kN/m
Multiplied x length of bracing wall
= 1.5kN/m x 2.4m = 3.6 kN
for a 2.4 m long section of
braced wall.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
19
8.3.1 General
(f)
(g)
Check even distribution and spacing
Check connection of bracing to
roof/ceilings and floors
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
20
8.3.2 Wind pressure on the building
Wind pressures on the
surfaces of the building
depend on the wind
classification, width of building
and roof pitch. Tables 8.1 to
8.5 give pressures depending
on these variables.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
21
When wind flows over a building it applies
different pressures (forces) on a flat vertical wall
to that on the sloping roof surface.
Pressure on roof
- 0.77 kPa*
Pressure on wall
- 1.10 kPa*
* These values are indicative only
and will vary with roof pitch,
building height to depth ratio etc.
The tables need to know the ratio between how
much roof area the wind ‘sees’ as opposed to
how much wall area the wind ‘sees’. The building
width and roof pitch will establish this ratio.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
22
8.3.2 Wind pressure on the building
Pressures are given for single storey and
upper storey of two storeys for both long
wind at 90O to the ridge and short wind
parallel to the ridge sides of the building,
and lower storey of two storeys or subfloor for
both long wind at 90O to the ridge and
short wind parallel to the ridge sides of
the building.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
23
8.3.3 Area of elevation
The wind direction used shall be that
resulting in the greatest load for the length
and width of the building, respectively.
As wind can blow from any direction, the
elevation used shall be that for the worst
direction.
For example ...........
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
24
8.3.3 Area of elevation
In the case of a single-storey house having a
gable at one end and a hip at the other, the
gable end facing the wind will result in a
greater amount of load at right angles to the
width of the house than the hip end facing the
wind.
Sloping roof
surface
All vertical
surface \
this is the worst
wind direction
+
vertical wall
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
25
For example, the relatively simple building shape
shown in Figure 8.2(A) must be broken into two
parts (shapes) in Wind Direction 2 because
gable ends are calculated using a different table.
After
calculating
the
separate
bracing
requirements for each part the bracing elements
used must also be distributed accordingly.
WIND DIRECTION 1
Area of elevation
Gable
End
Area of
elevation
Gable End
h
WIND DIRECTION 2
Area of elevation
WIND DIRECTION 2
h
Hip End
WIND DIRECTION 2
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
26
As indicated by Figures 8.2 (A) and Note 1, the
area of an elevation includes only the top half of
the wall.
Note: 1 - h = half the height of the wall (half of the
floor to ceiling height).
This is the area
used to calculate
single or upper
storey bracing
Ceiling diaphragm
Floor Slab
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
27
As indicated by Figures 8.2 (B) and Note 1, the
area of an elevation
For lower storey of two storey section h = half the
height of the lower storey (i.e. lower storey floor to
lower storey ceiling)
Ceiling diaphragm
This is the
area used
to calculate
lower storey
bracing
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
Floor diaphragm
28
Note 3 of Figures 8.2 (A, B & C) pg 113 states
The area of elevation of the triangular portion of
eaves overhang up to 1000 mm wide may be
ignored in the determination of area of elevation.
Area of Elevation
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
29
Include the area of
enclosed verandah in the
total area. Also include any
roof area over an open
verandah
Calculate area of enclosed
verandah separately using its
width and pitch and distribute
bracing accordingly.
Do not include
areas of open
verandahs
Open
Verandah
Enclosed
Verandah
Open
Verandah
Enclosed
Verandah
Width
Width
Width
Building with open and
enclosed verandahs, with main
roof pitched from verandah
Building with open and enclosed
verandahs, with main roof
pitched separately from
beams.
verandahs.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
30
8.3.4 Racking force (pg 116)
The total racking force, in kN,
shall be calculated as follows:
Projected area of elevation (m2)
x
Lateral wind pressure (kPa)
= Total racking force
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
31
TABLE 8.1 (pg 116)
•Gable ends and flat,
vertical surfaces
only
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
32
TABLE 8.1
PRESSURE (kPa) ON PROJECTED AREA — SINGLE STOREY, UPPER OF TWO
STOREY, LOWER STOREY OR SUBFLOOR OF SINGLE OR TWO STOREY —
ALL VERTICAL SURFACE ELEVATIONS (GABLE ENDS, SKILLION ENDS AND
FLAT WALL SURFACES)
Wind direction
Wind direction
Wind direction
Wind direction
Wind direction
Wind direction
Wind classification
Pressure (kPa)
N1
0.67
N2
0.92
N3
1.4
N4
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
2.1
33
Table 8.2 is used for
determining the pressure
on single or upper
storey elevations where
the wind direction is at
90O to the ridge and for
wind speeds N1, N2, N3 &
N4.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
34
TABLE 8.2
continued
PRESSURE (kPa) ON PROJECTED AREA—SINGLE STOREY OR UPPER OF
TWO STOREY—LONG LENGTH OF BUILDING—HIP OR GABLE ENDS
WIND 90O TO RIDGE
A3
W
Wind direction
Wind direction
W
NOTE: See Figure 1.1 for guidance on determining W.
N2
N2
0
5
10
15
20
25
30
35
4.0
0.84
0.74
0.67
0.61
0.61
0.72
0.77
0.76
5.0
0.84
0.71
0.64
0.57
0.58
0.69
0.75
0.74
6.0
0.84
0.69
0.61
0.55
0.59
0.70
0.74
0.74
7.0
0.84
0.67
0.58
0.53
0.59
0.70
0.73
0.74
8.0
0.84
0.65
0.56
0.51
0.60
0.71
0.72
0.75
9.0
0.84
0.64
0.54
0.49
0.61
0.71
0.71
0.75
10.0
0.84
0.62
0.52
0.48
0.61
0.72
0.70
0.75
11.0
0.84
0.60
0.50
0.48
0.62
0.72
0.71
0.75
12.0
0.84
0.59
0.47
0.49
0.63
0.72
0.71
0.76
13.0
0.84
0.57
0.45
0.49
0.63
0.73
0.71
0.77
14.0
0.84
0.56
0.43
0.50
0.64
0.73
0.72
0.77
15.0
0.84
0.55
0.42
0.50
0.65
0.73
0.72
0.77
16.0
0.84
0.53
0.51
0.65
0.73
AS
16840.40
SECTION
8 - RACKING
AND SHEAR FORCES
0.72
0.78
35
Table 8.3 is used for
determining the pressure
on lower storey
elevations where the
wind direction is at 90O
to a ridge and for wind
speeds N1, N2, N3 & N4.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
36
continued
TABLE 8.3
PRESSURE (kPa) ON PROJECTED AREA—LOWER STOREY OR SUBFLOOR OF SINGLE OR
TWO STOREY—LONG LENGTH OF BUILDING—HIP OR GABLE ENDS
WIND 90O TO RIDGE
A3
W
Wind direction
W
Wind direction
NOTE: See Figure 1.1 for guidance on determining W .
N2
N2
0
5
10
15
20
25
30
35
4.0
0.84
0.74
0.67
0.61
0.61
0.72
0.77
0.76
5.0
0.84
0.71
0.64
0.57
0.58
0.69
0.75
0.74
6.0
0.84
0.69
0.61
0.55
0.59
0.70
0.74
0.74
7.0
0.84
0.67
0.58
0.53
0.59
0.70
0.73
0.74
8.0
0.84
0.65
0.56
0.51
0.60
0.71
0.72
0.75
9.0
0.84
0.64
0.54
0.49
0.61
0.71
0.71
0.75
10.0
0.84
0.62
0.52
0.48
0.61
0.72
0.70
0.75
11.0
0.84
0.60
0.50
0.48
0.62
0.72
0.71
0.75
12.0
0.84
0.59
0.47
0.49
0.63
0.72
0.71
0.76
13.0
0.84
0.57
0.45
0.49
0.63
0.73
0.71
0.77
14.0
0.84
0.56
0.43
0.50
0.64
0.73
0.72
0.77
15.0
0.84
0.55
0.42
0.50
0.65
0.73
0.72
0.77
16.0
0.84
AS
SECTION
0.53 16840.40
0.51 8 - RACKING
0.65
0.73
AND SHEAR FORCES
0.72
0.78
37
Table 8.4 is used for
determining the pressure
on single or upper
storey elevations where
the wind direction is
parallel to a ridge and for
wind speeds N1, N2, N3 &
N4.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
38
TABLE 8.4
PRESSURE (kPa) ON PROJECTED AREA—SINGLE STOREY OR UPPER OF
TWO-STOREY—SHORT END OF BUILDING—HIP ENDS
WIND PARALLEL TO RIDGE
A3
W
W
Wind direction
NOTE: See Figure 1.1 for guidance on determining W.
N2
Wind
direction
N2
0
5
10
15
20
25
30
35
4.0
0.92
0.86
0.81
0.77
0.76
0.79
0.82
0.81
5.0
0.92
0.84
0.79
0.74
0.73
0.77
0.81
0.79
6.0
0.92
0.83
0.77
0.72
0.73
0.77
0.79
0.79
7.0
0.92
0.82
0.75
0.70
0.73
0.77
0.78
0.79
8.0
0.92
0.80
0.73
0.68
0.72
0.77
0.77
0.79
9.0
0.92
0.79
0.71
0.66
0.72
0.77
0.76
0.79
10.0
0.92
0.78
0.69
0.65
0.72
0.77
0.75
0.78
11.0
0.92
0.77
0.68
0.64
0.72
0.77
0.75
0.79
12.0
0.92
0.76
0.66
0.64
0.72
0.77
0.75
0.79
13.0
0.92
0.75
0.64
0.64
0.73
0.77
0.75
0.79
14.0
0.92
0.73
0.62
0.64
0.73
0.77
0.76
0.79
15.0
0.92
0.72
0.60
0.64
0.73
0.77
0.76
0.80
16.0
0.92
0.71
0.59
0.64
0.73
0.77
0.76
0.80
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
39
Table 8.5 is used for
determining the pressure
on lower storey
elevations where the
wind direction is parallel
to a ridge and for wind
speeds N1, N2, N3 & N4.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
40
TABLE 8.5
PRESSURE (kPa) ON PROJECTED AREA—LOWER STOREY OR SUBFLOOR OF
SINGLE OR TWO STOREY—SHORT END OF BUILDING—HIP ENDS
WIND PARALLEL TO RIDGE
A3
W
Wind direction
NOTE: See Figure 1.1 for guidance on determining W.
N2
N2
0
5
10
15
20
25
30
35
4.0
0.92
0.90
0.89
0.87
0.86
0.87
0.88
0.87
5.0
0.92
0.90
0.88
0.85
0.85
0.86
0.87
0.87
6.0
0.92
0.89
0.87
0.84
0.85
0.86
0.87
0.86
7.0
0.92
0.89
0.86
0.84
0.84
0.86
0.86
0.86
8.0
0.92
0.88
0.85
0.83
0.84
0.85
0.85
0.86
9.0
0.92
0.88
0.84
0.82
0.84
0.85
0.84
0.85
10.0
0.92
0.87
0.84
0.81
0.83
0.85
0.84
0.85
11.0
0.92
0.87
0.83
0.80
0.83
0.85
0.84
0.85
12.0
0.92
0.86
0.82
0.80
0.83
0.85
0.83
0.85
13.0
0.92
0.86
0.81
0.80
0.83
0.84
0.83
0.85
14.0
0.92
0.85
0.80
0.80
0.83
0.84
0.83
0.85
15.0
0.92
0.85
0.79
0.79
0.83
0.84
0.83
0.85
16.0
0.92
AS
SECTION
085 16840.78
0.79 8 - RACKING
0.83
0.84
AND SHEAR FORCES
0.83
0.85
41
8.3.6.2 Nominal wall bracing (pg 140)
Nominal wall bracing is wall
framing lined with sheet
materials such as plywood,
plasterboard, fibre cement or
hardboard, or the like, with
the wall frames nominally
fixed to the floor and the roof
or ceiling frame. (table 9.4 pg
167)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
42
The most common nominal bracing
material used in houses is plasterboard
wall linings.
Plasterboard, fixed to the wall frame
appropriately (to manufacturers
specification) is given ‘structural bracing’
status with a reasonable strength rating.
Fixed to the wall frame with nominal
fixings, however, its bracing strength is
much lower.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
43
8.3.6.2 Nominal wall bracing
The maximum amount that can be
resisted by nominal wall bracing is 50%
of the total racking forces determined
from Clause 8.3.4 . Nominal wall bracing
shall be evenly distributed throughout the
building. If this is not the case, the
contribution of nominal bracing shall be
ignored.
The minimum length of nominal
bracing walls shall be 450 mm.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
44
8.3.6.2 Nominal wall bracing
The minimum length of nominal bracing
walls shall be 450 mm.
The bracing capacity of nominal bracing is
scheduled in Table 8.17.
TABLE 8.17
NOMINAL SHEET BRACING WALLS
Method
Bracing capacity (kN/m)
Sheeted one side only
0.45 kN/m
Sheeted two sides
0.75 kN/m
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
45
Where sheet wall lining is placed over the top
of a structural brace, the value of the sheet
wall lining can not be given its nominal value
for the section that overlaps the structural
brace.
Structural brace
This section of wall sheeting is
counted as nominal bracing.
Minimum length 450mm.
The section of wall sheeting that overlaps
the Structural brace must not be counted
as nominal bracing.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
46
8.3.6.3 Structural wall bracing
See TABLE 8.18 pg 141
For sheet-braced walls, the sheeting
shall be continuous from the top plate
to the bottom plate
Unless otherwise specified, sheet-
bracing walls shall be a minimum
of 900 mm wide to satisfy the
requirements of their nominated
AS 1684 SECTION 8 - RACKING
ratings.
AND SHEAR FORCES
47
TABLE 8.18
STRUCTURAL WALL BRACING
(MAXIMUM WALL HEIGHT = 2.7 m)
Bracing
capacity
(kN/m)
Type of bracing
(a)
A2
Two diagonally opposed timber or metal angle braces
45 x 19 mm or 70 x 19 mm hardwood
timber brace fixed to each stud and plate
with 1/50 x 2.8 mm  galv. flat head nail
Galv. metal angle (18 x 16 x 1.2 mm)
brace fixed to studs with one
30 x 2.8 mm  nail and to plates with
2/30 x 2.8 mm  galv. flat head nails
Fix bottom plate
to floor frame or
slab with nominal
fixing only
(see Table 9.4)
A4
0.8
30 
to
60 
1800 mm min. to
2700 mm max.
A3
AS 1684orSECTION
NOTE: All flathead nails shall be galvanized
equivalent.
8 - RACKING
AND SHEAR FORCES
48
TABLE 8.18 (continued)
Type of bracing
)
Bracing
capacity
(kN/m)
Metal straps — Tensioned
Tensioned galvanized
metal strap with min.
thickness of 0.8 mm and
min. net sectional area of
15.2 mm 2 , fixed to studs
with one 30 x 2.8 mm 
galvanized flathead nail
(or equivalent) and to plates
with 3/30 x 2.8 mm 
galvanized flathead nails
(or equivalent)
A3
A4
30 
 to
60 
1800 mm min. to
2700 mm max.
1.5
Fix bottom plate to floor
frame or slab with nominal
fixing only (see Table 9.4)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
49
TABLE 8.18 (continued)
Bracing
capacity
(kN/m)
Type of bracing
)
Timber and metal angle braces The maximum depth of a notch or saw-cut shall not exceed 20 mm.
Saw-cuts studs shall be designed as notched.
30 x 0.8 mm
galv. strap
3/30 x 2.8 mm 
galv. flathead
nails (or equivalent)
to each end to stud
A3
1.5
A4
30 x 0.8 mm
galv. strap
3/30 x 2.8 mm 
galv. flathead
nails (or equivalent)
to each end to stud
30 x 0.8 mm galv. strap
Fix bottom plate to floor frame
or slab with nominal fixing only
3/30 x 2.8 mm  galv. flathead
(see
9.4)
(or equivalent) nails to each end
to studSECTION
AS 1684
8 -Table
RACKING
AND SHEAR FORCES
50
TABLE 8.18 (continued)
Type of bracing
TABLE 8.18 (continued)
(d)
Bracing
capacity
(kN/m)
Double diagonal tension or metal strap braces
30 x 0.8 mm galv. metal strap
looped over plate and fixed
to stud with 4/30 x 2.8 mm 
galv. flathead nails (or
equivalent) to each end.
Alternatively, provide single
straps to both sides, with
4 nails per strap end,
or equivalent anchors
or other fasteners
A3
A4
30  to
60 
1800 mm min. to
2700 mm max.
3.0
30 x 0.8 mm (or equivalent)
tensioned galv. metal straps
nailed to plates with
4/30 x 2.8 mm  galv.
flathead nails (or equivalent)
to each end
For fixing of bottom plate to floor
frame or slab, r efer to Clause 8.3.6.10
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
51
TABLE 8.18 (continued)
Bracing
capacity
(kN/m)
Type of bracing
TABLE 8.18 (continued)
(e) Diagonal timber wall lining or cladding Minimum thickness of board—12 mm fixed with
2/20  50 mm long T-head nails.
Intermediate crossings of boards and studs shall be fixed with one nail.
2700 mm max.
A4
30 x 0.8 mm G. I.
strap to each
corner of bracing
panel tying studs
to plates 4/2.8 mm
dia. nails each end
40  to 50 
For fixing of bottom
plate to floor frame
or slab, refer to
Clause 8.3.6.10
Perimeter
nail spacing
s
2100 mm min.
NOTE: Noggings have been omitted for clarity.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
S (mm)
60
40
2.1
3.0
52
TABLE 8.18 (continued)
Type of bracing
(g) Plywood Plywood shall be nailed to frame using 30 mm2.8 mm 
galvanized flathead nails or equivalent.
Minimum plywood
thickness (mm)
A3
Stress
grade
Bracing
capacity
(kN/m)
Stud
spacing
mm
450
600
No nogging
(except horizontal
butt joints)
F8
F11
F14
F27
7
4.5
4
3
9
7
6
4.5
One row of
nogging
F8
F11
F14
F27
7
4.5
4
3
7
4.5
4
3
3.4
Where required, one row of
nogging staggered or single
line at half wall height
A4
NOTES:
1 For plywood fixed to both sides of the wall, see Clauses Error! Reference
source not found. and Error! Reference source not found..
No other rods or straps are required
top or bottom
ASbetween
1684 SECTION
8 plate.
- RACKING
Fix bottom plate to floor frame or slab with
nominal
fixing
only
(see Table 9.4).
AND SHEAR FORCES
53
Bracing
capacity
(kN/m)
TABLE 8.18 (continued)
Type of bracing
TABLE 8.18 (continued)
(h) Plywood Plywood shall be nailed to frame using 302.8  galvanized
flathead nails or equivalent.
For Method A, M12 rods shall be used at each end of sheathed section top
plate to bottom plate/floor frame. Method B has no rods but sheathing shall
be nailed to top and bottom plates and any horizontal joints at 50 mm
centres.
A3
A4
Minimum plywood
thickness (mm)
Stud spacing
Stress
(mm)
grade
450
600
F8
7
9
F11
6
7
F14
4
6
F27
4
4.5
Fastener spacing, s
(mm)
Top and
bottom plate:
 Method A
150
 Method B
50
Vertical edges
150 Method A
6.4
Intermediate
300
studs
Method B
6.0
Fixing of bottom
plate to floor frame
or slab
Method A: M12 rods
as shown plus a
13 kN capacity
connection at max.
1200 mm centres
1684
SECTION
- RACKING
NOTE: For plywood fixed to bothAS
sides
of the
wall, see 8Clauses
8.3.6.5 and
AND
SHEAR
FORCES
8.3.6.10.
Method B: A 13 kN
capacity connection
at each end and
intermediately at
max. 1200 mm
centres
54
Bracing
capacity
(kN/m)
TABLE 8.18 (continued)
Type of bracing
TABLE 8.18 (continued)
(j) Hardboard Hardboard shall comply with AS/NZS 1859.4.
Hardboard shall be nailed to frame using minimum 25  2.8 mm 
galvanized nails or equivalent.
Nails shall be located a minimum of 10 mm from the vertical edges and
20 mm from the top and bottom edges.
Panel edges shall be supported by studs.
Minimum hardboard
thickness (mm)
Stud spacing
(mm)
Type
450
60
0
RD
5.5
5.5
GP
6.4
6.4
3.4
Fastener spacing
(mm)
Top and
bottom plates
100
Vertical
edges
100
Intermediate
studs
300
NOTES:
A2
A4
1 Noggings have been omitted for clarity.
2 For fixing of bottom plate to floor frame or slab, see Clause 8.3.6.10 .
Fix bottom plate to floor frame or AS
slab 1684
with nominal
fixing8only
(see Table 9.4) Refer GUIDE NOTE No.9
SECTION
- RACKING
AND SHEAR FORCES
55
Bracing
capacity
(kN/m)
TABLE 8.18 (continued)
Type of bracing
(j) Hardboard Hardboard shall comply with AS/NZS 1859.4.
Hardboard shall be nailed to frame using minimum 30  2.8 mm 
galvanized nails or equivalent.
Nails shall be located a minimum of 10 mm from the vertical edges and
15 mm from the top and bottom edges.
Panel edges shall be supported by studs.
Minimum hardboard
thickness (mm)
Stud spacing
(mm)
Type
GP
450
600
6.4
6.4
6.0
Fastener spacing
(mm)
A2
A4
Top and
bottom plates
50
Vertical edges
100
Intermediate
studs
300
NOTES:
1 Noggings have been omitted for clarity.
2 For fixing of bottom plate to floor frame or slab, see Clause 8.3.6.10.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
56
EXAMPLE: Required Racking force = 22kN
less provision for 50% nominal bracing = 11kN.
The proposed method of bracing is 2100mm long cut-in timber or
metal angle braces. Type c
Each brace is rated at 3.15kN (2.1 m long x 1.5kN/m).
11kN / 3.15 = 3.5 therefore 4 x 2.1m (12.6kN total) long braces
are required plus 9.4kN of nominal bracing.
(Check that 9.4kN of nominal bracing is achievable and also that
the cut-in braces are not spaced more than required by 8.3.6.7)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
57
EXAMPLE: cont’d
Of course there are other combinations for the above
situation –
4 x 0.9 long ply braces rated at 3.4kN/m = 12.24kN plus
9.76kN of nominal bracing (type g)
or
2 x 0.9 long hardboard braces rated at 3.4kN/m = 6.12kN
plus 2 x 2.1 long metal angle = 6.3kN plus 9.58kN of
nominal bracing. (type l)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
58
8.3.6.4 Wall capacity and height
modification pg 147
The capacity of bracing walls
given in Table 8.18 is appropriate
to wall heights up to and
including 2700 mm. For wall
heights greater than 2700 mm
the capacity shall be multiplied
by the values given in Table 8.19.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
59
8.3.6.5 Length and capacity for
plywood bracing walls
Where the same structural
plywood bracing system is fixed
to both sides of the wall, the
capacity of the wall will equal
the combined capacity of the
bracing system on each side.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
60
8.3.6.6 Location and distribution
of
bracing
Bracing shall be approximately
evenly distributed and shall be
provided in both directions (see
Figure 8.5).
Bracing shall initially be placed
external walls and where
possible at the corners of the
in
building.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
61
A
A
B
D
C
B
C
D
Wind
direction
E
Wind
direction
Total bracing strength = A + B + C + D, etc.
NOTE: A, B, C and D are the design strengths of individual bracing walls.
(a) Right angles to long side
(b) Right angles to short side
FIGURE 8.5 LOCATION OF BRACING
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
62
A3
8.3.6.7 Spacing of bracing walls in
single storey or upper storey of two
storey construction
For single or upper-storey
construction, the maximum
distance between braced walls at
right angles to the building length
or width shall not exceed
9000 mm for wind classifications
up to N2 (see Figure 8.6).
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
63
A3
8.3.6.7 Spacing of bracing walls in
single storey or upper storey of two
storey construction
For wind classifications greater than N2,
spacing shall be in accordance with
Table 8.20 (pg 150) (N3) and Table 8.21
(N4) for the relevant wind classification,
ceiling depth and roof pitch.
NOTE: Ceiling depth is measured
parallel to the wind direction being
considered. AS 1684 SECTION 8 - RACKING
64
AND SHEAR FORCES
N3
TABLE 8.20
MAXIMUM SPACING OF BRACING WALLS — N3 WIND CLASSIFICATION
Maximum bracing wall spacing (m)
Ceiling
depth (m)
Roof pitch (degrees)
0
5
10
15
17.5
20
25
30
35
4
5.9
6.6
7.4
7.5
7
6.4
5.1
4.4
4.2
5
7.4
8.3
9
9
8.6
7.9
6
5
4.7
6
8.9
9
9
9
9
8.8
6.7
5.6
5.1
7
9
9
9
9
9
9
7.1
6.1
5.5
8
9
9
9
9
9
9
7.6
6.7
5.7
9
9
9
9
9
9
9
7.9
7.2
5.9
10
9
9
9
9
9
9
8.4
7.9
6.2
11
9
9
9
9
9
9
8.7
7.9
6.4
12
9
9
9
9
9
9
9
7.9
6.6
13
9
9
9
9
9
9
9
8.1
6.6
14
9
9
9
9
9
9
9
8.3
6.7
15
9
9
9
9
9
9
9
8.4
6.8
16
9
9
9
9
9
9
9
8.6
6.9
NOTE: A ceiling depth of 16 m is to be used for all ceiling depths greater than 16 m.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
65
A3
8.3.6.7 Spacing of bracing walls in
single storey or upper storey of two
Where bracing cannot be placed in
external walls because of openings or the
like, a structural diaphragm ceiling can be
used to transfer racking forces to bracing
walls that can support the loads.
Alternatively, wall frames may be designed
for portal action. (This requires
engineering advice)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
66
Spacing between bracing
walls for wind
direction B
W
in
d
di
re
ct
io
n
Spacing between
bracing walls for
wind direction A
A
W
in d
d
c
ire
ti
on
B
FIGURE 8.6 SPACING OF BRACING
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
67
The ceiling and floor diaphragms
play important roles in the transfer
of wind loads from the walls and
roof to the braces.
The ability of a ceiling or floor
diaphragm to effectively transfer
the wind load depends on the
depth of the diaphragm.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
68
• Narrow or long diaphragms will not
transfer the wind loads as
effectively as a deeper diaphragm.
The smaller the length to depth
ratio the more effective the
diaphragm.
• For this reason the spacing of
bracing walls in limited as per
Clause 8.3.6.7.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
69
m
g
a
r
p h th
a
i
D
g
Len
Dia
phr
De agm
pth
The above diaphragm, has a large length to
depth ratio, (the length being the distance
between braces) will not transfer the wind
loads effectively.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
70
a gm
r
h
i ap gt h
D
en
m
L
g
a
r
h
p
D i a ngt h
Le
Dia
phr
De agm
pth
By adding an intermediate brace, the diaphragm
is broken into two.
Individually they have a smaller length to depth
ratio and will transfer the wind loads effectively
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
71
ap
De hrag
pth m
Di
Dia
phr
Len agm
gth
The same diaphragm, with the wind from
the other direction, will transfer loads very
effectively because its length to depth ratio
is small.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
72
8.3.6.9 Fixing of top of bracing
walls
All internal bracing walls shall be
fixed to the floor for lower storey
bracing walls, the ceiling or roof
frame, and/or the external wall
frame, with structural
connections of equivalent shear
capacity to the bracing capacity
of that particular bracing wall.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
73
8.3.6.9 Fixing of top of bracing
walls
Nominal and other bracing walls
with bracing capacity up to
1.5 kN/m require nominal fixing
only, i.e. no additional fixing
requirements.
For typical details and shear
capacities, see Table 8.22. pg 152
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
74
Fixing of top of bracing walls
Wind loads, transferred from the roof
and walls to ceiling and floor
diaphragms are then transferred
through braces to the ground.
These braces, however, can only
transfer these loads if the brace is
connected to the ceiling or floor
above and the floor below.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
75
Internal brace not
connected to ceiling
diaphragm
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
Internal brace
not connected
to floor
diaphragm
76
The strength of these connections must be at
least equal to the load the brace can transfer
e.g. a cut-in timber or metal brace 2.4 m long
can transfer a total of 3.6kN (2.4 x 1.5kN/m) –
a 3.6kN connection to the diaphragm is
required.
or alternatively the strength of the brace can
be reduced to equal the strength of the
connection(s) .
e.g. if a 2.8kN connection is used for the
above brace, its bracing capacity will be
reduced to 2.8kN.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
77
Connection used equals the
total brace capacity.
1/30 x 0.8 mm G.I strap with
6/2.8 nails each end of
strap in JD4 timber as per
Table 8.22(k) = 4.9kN
Top plate
Refer to table 8.22 pg 155
Internal
bracing
wall
External wall
Metal angle brace
as per Table 8.18(c)
2.7 m long
Total brace capacity =
1.5kN x 2.7m =
4.05kN
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
78
Connections used equals
the total brace capacity.
3 batten to top plate connections
with 2/3.05 mm O nails per batten
as per Table 8.22(d)
in JD4 timber = 5.4kN
Ceiling battens fixed
with 1/3.05 mm O nail
either side of wall
Rafter/Truss
Refer to table 8.22 pg153
Provide clearance
where roof is
trussed.
Bracing wall
Metal angle brace
as per Table 8.18(c)
2.7 m long
Total brace capacity =
1.5kN x 2.7m =
4.05kN
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
79
AS 1684
USER GUIDE
G U I D E T O T H E U S E O F AS 1684
Fixing of Top of Bracing Walls
5
Example 1 - Strapping to external walls
Connect braced wall to external wall using 2 straps as per
Table 8.22 (k). For JD4 pine, 4/2.8 dia nails required each
end of each strap to achieve 6.6 kN.
Brace
6.12kN
capacity
(1.8m x 3.4kN/m)
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
80
AS 1684
USER GUIDE
G U I D E T O T H E U S E O F AS 1684
Fixing of Top of Bracing Walls
5
Example 2 - Nailing floor or ceiling joists to walls
Connect braced wall to 6 ceiling joists using 2/3.05 dia skew
nails per joist as per Table 8.22 (i). For JD4 pine, capacity
= 6 x 1.1 = 6.6 kN
Brace
5.76kN
capacity
(0.9m x 6.4
kN/m)
NOTE: The top plate in the wall
must provide a continuous tie
from the braced section of wall
to where the top plate is
connected to the floor, ceiling or
roof diaphragm.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
81
AS 1684
USER GUIDE
G U I D E T O T H E U S E O F AS 1684
Fixing of Top of Bracing Walls
5
Example 3 - Combinations
Connect braced wall to ceiling joists or truss bottom chords
with blocking as per Table 8.22 (j) 4/3.05 dia nails to each
block + one strap to the external wall with 4/2.8 dia nails each
end of strap.
Brace
6.75kN
capacity
(0.9m x 7.5
kN/m)
NOTE: The top plate in the wall
must provide a continuous tie
from the braced section of wall
to where the top plate is
connected to the floor, ceiling or
roof diaphragm.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
82
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
A3
J2
J3
J4
JD4 JD5 JD6
3.05
3.0
2.1
1.5
2.1
1.8
1.3
3.33
3.3
2.4
1.7
2.4
2.0
1.5
12
8.3
5.9
8.3
5.9
4.3
Nails
(a)
4/75 mm  nails
as per table or
3/No. 14 type 17
screws
90 x 35 mm F8 or
90 x 45 mm F5
trimmer on flat
Screws
No.14
Type 17
A4
2/75 mm  nails
each end as per
table or 2/75 mm
No. 14 type 17 screws
Seasoned
timber
Provide
clearance
where roof
is trussed
Bracing wall
NOTE: For trussed roofs, nails or screws
through the top plate shall be placed in
holes that permit free vertical movement
of the trusses.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
83
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
(a)
(b)
Trimmer :
one bolt:
or:
two bolts:
or:
Seasoned
timber
J2
J3
J4
JD4 JD5 JD6
1/No.14
Type 17
4.8
3.5
2.5
3.5
2.5
1.8
2/No.14
Type 17
9.7
6.9
4.9
6.9
4.9
3.6
3/No.14
Type 17
13
9.3
6.6
9.8
7.4
5.4
M10
6.4
4.1
2.6
4.3
3.0
2.0
M12
7.6
4.9
3.1
5.1
3.6
2.5
2/M10
12
8.0
5.1
8.4
5.9
4.0
13
9.3
6.1
9.8
7.0
4.9
Screws
90 x 35 mm F8
90 x 45 mm F5
120 x 35 mm F8
120 x 45 mm F5
Framing anchors
(legs not bent)
6/2.8 mm  nails
each face
Bolts
Provide
clearance
where roof
is trussed
Screws or bolts
as per table
Bracing wall
NOTE: For trussed roofs, screws or bolts through the top
plate shall be placed in holes that permit free vertical 2/M12
AS 1684 SECTION 8 - RACKING
movement of the trusses.
AND SHEAR FORCES
84
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
J2
J3
J4
Seasoned
timber
JD4 JD5 JD6
(c)
90 x 35 mm F8
bridging piece
Nails
Two looped straps (30 x 0.8 mm G.I.)
4/2.8 mm  nails each end and
to bridging
30  (max)
Gap between
top plate and
truss
3.05 6.6
4.7
3.4
5.0
4.2
3.1
3/75 mm  nails
as per table
3.33 7.4
5.3
3.7
5.5
4.6
3.5
Bracing wall
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
85
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
Seasoned
timber
J2
J3
J4
JD4 JD5 JD6
2.5
1.8
1.3
1.8
(d)
Rafter
or truss
Provide
clearance
where roof
is trussed
2/3.05 mm  nails per
batten, 3.5 mm  holes
shall be drilled in batten
to allow for truss deflection
1.5
1.1
Ceiling battens
fixed with
1/3.05 mm  nail
either side of wall
Bracing wall
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
86
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
TABLE 8.22 (continued)
J2
J3
J4
JD4 JD5 JD6
4/3.05
5.0
3.6
2.5
3.6
3.0
2.2
6/3.05
6.6
4.7
3.4
5.0
4.2
3.1
4/3.33
5.6
4.0
2.8
4.0
3.3
2.5
6/3.33
7.4
5.3
3.7
5.5
4.6
3.5
M10
6.4
4.1
2.6
4.3
3.0
2.0
M12
7.6
4.9
3.1
5.1
3.6
2.5
2/M10
13
8.0
5.1
8.4
5.9
4.0
2/No.14
Type 17
9.7
6.9
4.9
6.9
4.9
3.6
3/No.14
Type 17
13
9.2
6.6
9.8
7.4
5.4
Nails
(e)
Nailing plates or framing anchor (legs not bent) to
either end of nogging 6/2.8 mm  nails each face
or 2/No.14 Type 17 batten screws either end
A3
90 x 35 mm F8
or 90 x 45 mm F5
trimmer
A4
Gap to
truss
Seasoned
timber
Shear blocks
nailed, bolted,
or screwed
as per table
Bracing wall
Bolts
Screws
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
87
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
J2
J3
J4
Seasoned
timber
JD4 JD5 JD6
(i)
Rafter, ceiling joist,
or bottom chord
A4
2 skew nails
per crossing
size as per
table
NOTE: For truss roof, nails through the
top plate shall be placed in holes that
permit free vertical movement of the
trusses.
Nails
Bracing wall
2/3.05
1.4
1.1 0.77 1.1 0.90 0.66
2/3.33
1.7
1.2 0.85 1.2
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
1.0
0.75
88
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
J2
J3
(j)
J4
Seasoned
timber
JD4 JD5 JD6
Nails
Nails, screws or bolts as per
table blocks to be both sides
of rafter or bottom chord
Blocking pieces
large enough to
avoid splitting
4/3.05
5.0
3.6
2.5
3.6
3.0
2.2
6/3.05
6.6
4.7
3.4
5.0
4.2
3.1
4/3.33
5.6
4.0
2.8
4.0
3.3
2.5
6/3.33
7.4
5.3
3.7
5.5
4.6
3.5
Bolts
M10
6.4
4.1
2.6
4.3
3.0
2.0
M12
7.6
4.9
3.1
5.1
3.6
2.5
2/M10
13
8.0
5.1
8.4
5.9
4.0
Screws
Bracing
wall
Gap between
top plate and
truss
2/No.14
Type17
9.7
6.9
4.9
6.9
4.9
3.6
3/No.14
Type17
15
10
7.4
10
7.4
5.4
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
89
TABLE 8.22
FIXING OF TOP OF BRACING WALLS
Shear capacity (kN)
Unseasoned
timber
Rafters, joists or trusses
to bracing wall
J2
(k)
2/30 x 0.8 mm G.I straps
with number of nails each
end of straps as per table
J3
Straps
J4
Seasoned
timber
JD4 JD5 JD6
Nails
4/2.8 4.3
3.1
2.2
3.3
3.0
2.1
6/2.8 6.5
4.6
3.3
4.9
4.0
3.1
4/2.8 8.7
6.2
4.4
6.6
5.4
4.1
6/2.8
9.3
6.6
9.8
8.1
6.1
1
Internal
bracing
wall
Top plate
External
wall
2
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
13
90
8.3.6.10 Fixing of bottom of bracing
walls pg 155
The bottom plate of timberframed bracing walls shall be
fixed at the ends of the
bracing panel and, if required,
intermediately to the floor frame
or concrete slab with
connections determined from
Table 8.18. pg 141
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
91
8.3.6.10 Fixing of bottom of bracing
walls
Where bottom plate fixing
information is not given in Table
8.18, the bottom plates shall be
fixed at the ends of each
bracing panel using tie-down
fixings determined from Table
8.23 and Table 8.24.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
92
8.3.6.10 Fixing of bottom of bracing
walls
For bracing wall systems of
capacity 6 kN/m or greater given
in Table 8.18, which do not
specify intermediate bottom
plate fixings, additional
intermediate bottom plate
fixings of a minimum of 1/M10
bolt, or 2/No. 14 Type 17 screws,
at max.1200 mm centres shall
SECTION 8 - RACKING
be used. AS 1684
AND SHEAR FORCES
93
TABLE
8.23 P153- AS1684.2 TABLE
8.24 P149- AS1684.3
UPLIFT FORCE AT ENDS OF BRACING WALLS
Wall
height
(mm)
2400
2700
3000
Uplift force at ends of bracing walls (kN)
For bracing walls rated at (kN/m) capacity
1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
8
10
2.4
2.7
3.0
3.6
4.1
4.5
4.8
5.4
6.0
6.0
6.8
7.5
7.2
8.1
9.0
8.4
9.5
11
10
11
12
11
12
14
12
14
15
13
15
17
14
16
18
19
22
24
24
27
30
NOTES:
1 Some bracing wall systems require fixings to be full-length anchor
rods, that is from the top plate to the floor frame or concrete slab.
2 The maximum tension load of 8.5 kN given in the Notes to Span
Tables for studs in the Supplements is not applicable when
considering the uplift force at the ends of bracing walls.
3 Where provided, the bottom plate tie-down details given in
Table 8.18 may be used in lieu of the details determined from
Table 8.23 and 8.24.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
94
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
Seasoned
timber
J2
J3
J4 JD4 JD5 JD6
M 10
cup -head
16
14
10
10
7
5
2/No.14
Type17
screws
11
8.4
4.8
9.0
7.2
5.4
(a)
M10 cuphead bolts or No. 14 Type 17
batten screws as per table, with min.
38mm penetration into flooring and/or joist
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
95
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
J2
(b)
J3
Seasoned
timber
J4 JD4 JD5 JD6
Bolts
Bolts as per table
M 10
18
18
18
15
12
9
M 12
27
27
26
20
16
12
Double joist or 450 mm long full depth cleat
nailed to joist with 6/75 x 3.15 mm  nails
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
96
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
Seasoned
timber
J2
J3
J4 JD4 JD5 JD6
M 10
bolt
18
18
18
15
12
9.0
M 12
bolt
27
27
26
20
16
12
(c)
Solid
nogging
Bearer or
underbatten
Bolt as
per table
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
97
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
(d)
A4
Screws or
coach screws
(125 mm long)
each end of
bridging piece
as per table
M10 bolt
120 x 70 mm
bridging piece
on flat
Seasoned
timber
J2
J3
J4 JD4 JD5 JD6
2/No. 14
Type 17
screws
12
8.3
5.9
8.3
5.9
4.3
3/No. 14
Type 17
screws
17
13
9.0
13
9.0
7.0
2/M12
coach
screws
18
18
13
15
12
9.0
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
98
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
Seasoned
timber
J2
J3
J4 JD4 JD5 JD6
M 10
bolt
18
16
11
15
12
9
M 12
bolt
22
16
11
18
15
11
(e)
2 nailing plates
each end of
bridging, legs
not bent, with
6/2.8 mm 
nails to each
face
100 x 50 mm
bridging
piece on
edge
Bolt as per table
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
99
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Unseasoned
timber
Fixing details
Seasoned
timber
J2
J3
J4 JD4 JD5 JD6
M 10
bolt
18
18
18
15
12
9
M 12
bolt
27
27
26
20
16
12
(f)
Hooked or bent
anchor bolt as
per table
180 mm min.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
100
TABLE 8.24
FIXING OF BOTTOM OF BRACING WALLS
Uplift capacity (kN )
Fixing details
TABLE 8.24 (continued) P154- AS1684.2 TABLE
Unseasoned
timber
Seasoned
timber
J2 P150J3 J4
JD4 JD5 JD6
8.24
AS1684.3
(g)
Fired,screwed,
chemical or
expanding
masonry anchor
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
Refer to manufacturer’s
specifications
101
8.3.7 Roof Bracing pg 158
8.3.7.1 Pitched roofs (coupled and noncoupled roofs)
The following shall apply to the
bracing of pitched roofs:
(a)
Hip roofs Hip roofs shall
not require any specific bracing
as they are restrained against
longitudinal movement by hips,
valleys and the like.
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
102
8.3.7.1 Pitched roofs (coupled and noncoupled roofs)
(b) Gable roofs (including cathedral roofs) For wind
classifications up to N2 gable roof buildings with a roof
pitch greater than 10° but less than 25°, shall be
provided with roof bracing in accordance with Clause .
Alternatively, for wind classifications up to N4 and roof
pitches to 35° bracing shall be in accordance with
Table 8.25, Table 8.26, and the following:
(i)
Ridge to internal wall — minimum of two
timber braces in opposing directions at
approximately 45° (see Table 8.25 and 8.26).
(ii)
Diagonal metal bracing — single or double
diagonal bracing shall be designed and installed in
AS engineering
1684 SECTION 8 - RACKING
103
accordance with
principles.
AND SHEAR FORCES
Ridgeboard
Alternative bracing:
opposing braces
from ridgeboard to
internal walls at
approximately 45
Rafter
Gable end
Min. 19 x 90 mm or 25 x 75 mm
brace at approximately 45  to
rafters on both sides of ridge
FIGURE 8.9 GABLE ROOF BRACING
AS 1684 SECTION 8 - RACKING
AND SHEAR FORCES
104