as 1684 section 8 - racking and shear forces 1 section 8 - racking (bracing) and shear forces week...

AS 1684 SECTION 8 - RACKING AND SHEAR FORCES

1

SECTION 8 -

RACKING (BRACING)AND SHEAR FORCES

WEEK 13


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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.


3

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.


4

G a b l e e n d b r a c i n g

C r o s s o r s h e e tb r a c i n g

C r o s s o r s h e e tb r a c i n g

W i n d

S u b f l o o r c r o s s - b r a c i n g ,c a n t i l e v e r e d s t u m p s o rb r a c i n g w a l l

FIGURE 8.1 VARIOUS BRACING SYSTEMS

CONNECTING HORIZONTAL DIAPHRAGMS


5

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.


6

NOTES to Figure 8.12.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.


7

NOTES to Figure 8.13.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.


8

Wind produces horizontal loads on buildings that must be transmitted through the structure to the foundation.


9

• 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.


10

• 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.


11

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

With ceiling diaphragm


12

Wind forces on the roof are carried to the ceiling sheeting (ceiling diaphragm) via the roof & ceiling framing

Wind forces on the are carried to the ceiling

sheeting (ceiling diaphragm) via the wall & ceiling framing

top half of th is wall

Ceiling diaphragm

Wind forces transfered to the ' are carried down to the slab and the ground via bracing walls.

ceiling diaphragm'BraceWind forces on the bottom half of

th is wall are carried direct to the ground slab & footings.

via the wall fram ing,


13

Wind forces on the roof are carried to the ceiling sheeting (ceiling diaphragm) via the roof & ceiling fram ing

Wind forces on the bottom half of th is wall are carried to the flooring (floor diaphragm) via the wall & floor framing

Wind forces on the top half of th is wall are carried to the flooring (floor diaphragm) via the wall & floor fram ing

Wind forces on the bottom half of th is wall are carried direct to the ground slab & footings.

via the wall fram ing,

Wind forces on the are carried to the ceiling

sheeting (ceiling diaphragm) via the wall & ceiling framing

top half of th is wall

Ceiling diaphragm

Floor diaphragm

Wind forces transfered to the ' are carried down to the ';f

via bracing

ceiling diaphragm'loor

diaphragm '

Wind forces transfered to the 'floor are carried down to

via bracing walls.

diaphragm '

the slab/footings & ground

Brace

Brace

Brace


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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.


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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:


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• Determine the wind classification

• Determine the wind pressure

• Determine area of elevation

• Calculate racking force


17

NOTE: To calculate the number of braces required for wall bracing, the required racking force (kN) is divided by the capacity of each brace.


18

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).


19

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.


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8.3.1 General

(f) Check even distribution and spacing

(g) Check connection of bracing to roof/ceilings and floors


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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.


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When wind flows over a building it applies different pressures (forces) on a flat vertical wall to that on the sloping roof surface.

* These values are indicative only and will vary with roof pitch, building height to depth ratio etc.

Pressure on roof- 0.77 kPa*

Pressure on wall- 1.10 kPa*

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.


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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.


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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 ...........


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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.

vertical wall

Sloping roof surface All vertical

surface this is the worst wind direction

+


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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.

W IND DIRECTION 2

h

Area of e levation

W IND DIRECTION 2

h

Area of e levationArea of elevationGable End

W IND DIRECTION 2

GableEnd

Hip End

W IND DIRECTION 1


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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).

Ceiling diaphragm

Floor Slab

This is the area used to calculate single or upper storey bracing


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This is the area used to calculate lower storey bracing

Ceiling diaphragm

Floor diaphragm

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)


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Note 3 of Figures 8.2 (A, B & C) pg 113 statesThe 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


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Include the area of enclosed verandah in the total area. Also include any roof area over an open verandah

Building with open and enclosed verandahs, with main roof pitched from verandah beams.

Width Width

Width

Building with open and enclosed verandahs, with main roof pitched separately from verandahs.

Calculate area of enclosed verandah separately using its width and pitch and distribute bracing accordingly.

Do not include areas of open verandahs

Open Verandah

Open Verandah

Enclosed Verandah

Enclosed Verandah


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8.3.4 Racking force (pg 116)

The total racking force, in kN, shall be calculated as follows:

Projected area of elevation (m2)

Lateral wind pressure (kPa)

Total racking force

x

=


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TABLE 8.1 (pg 116)

•Gable ends and flat, vertical surfaces only


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T A B L E 8 . 1

P R E S S U R E ( k P a ) O N P R O J E C T E D A R E A — S I N G L E S T O R E Y , U P P E R O F T W OS T O R E Y , L O W E R S T O R E Y O R S U B F L O O R O F S I N G L E O R T W O S T O R E Y —

A L L V E R T I C A L S U R F A C E E L E V A T I O N S ( G A B L E E N D S , S K I L L I O N E N D S A N DF L A T W A L L S U R F A C E S )

W in d d i re c t io n W ind d ire c t ion

W ind d ire c t ion W ind d ire c t ion

W ind d ire c t ion

W ind d ire c t ion

W i n d c l a s s i f i c a t i o n P r e s s u r e ( k P a )

N 1 0 . 6 7

N 2 0 . 9 2

N 3 1 . 4

N 4 2 . 1


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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.


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N2

continued

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 0.40 0.51 0.65 0.73 0.72 0.78

T A B L E 8 . 2

P R E S S U R E ( k P a ) O N P R O J E C T E D A R E A — S I N G L E S T O R E Y O R U P P E R O FT W O S T O R E Y — L O N G L E N G T H O F B U I L D I N G — H I P O R G A B L E E N D S

N O T E : S ee F ig u re 1 .1 fo r gu idan ce on d e te rm in ing .W

W

WW ind d ire c t ion

W ind d ire c t ion

WIND 90O TO RIDGE

A3


36

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.


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N2

continued

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 0.40 0.51 0.65 0.73 0.72 0.78

N O T E : S ee F igu re 1 .1 fo r g u id an ce on de te rm in ing .W

W ind d ire c t ionW ind d ire c t ion

W W

TABLE 8.3PRESSURE (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


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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.


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N2N2

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

T A B L E 8 .4

P R E S S U R E ( k P a ) O N P R O J E C T E D A R E A — S I N G L E S T O R E Y O R U P P E R O FT W O - S T O R E Y — S H O R T E N D O F B U I L D I N G — H I P E N D S

W in d d i re c t io n W in d d ire c t io n

N O T E : S ee F ig u re 1 .1 fo r g u idan ce on de te rm in ing .W

WIND PARALLEL TO RIDGE

A3


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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.


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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 0.92 085 0.78 0.79 0.83 0.84 0.83 0.85

TABLE 8.5

PRESSURE (kPa) O N PROJECTED AREA— LOW ER STOREY OR SUBFLOOR OFSINGLE OR TW O STO REY— SHORT END OF BUILDING— H IP ENDS

W in d d i re c t io n

N O T E : S ee F ig u re 1 .1 fo r g u id an c e o n d e te rm in in g .W

WIND PARALLEL TO RIDGE

A3


42

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)


43

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.


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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.

8.3.6.2 Nominal wall bracing


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The minimum length of nominal bracing walls shall be 450 mm.

The bracing capacity of nominal bracing is scheduled in Table 8.17.

8.3.6.2 Nominal wall bracing

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


46

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.

Th is section o f w all shee ting is counted as nom inal b racing .M in im um length 450m m .

S tructural brace

The section of w all shee ting that overlapsthe S tructu ra l b race m ust not be coun tedas nom ina l b racing .


47

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 ratings.

8.3.6.3 Structural wall bracing


48

A2

A4

T A B L E 8 .1 8

S T R U C T U R A L W A L L B R A C I N G( M A X I M U M W A L L H E I G H T = 2 .7 m )

T y p e o f b r a c in g

B r a c in g

c a p a c i ty

( k N / m )

( a ) T w o d ia g o n a l l y o p p o s e d t i m b e r o r m e ta l a n g l e b r a c e s

4 5 x 1 9 m m o r 7 0 x 1 9 m m h a rd w o o dt im b e r b r a c e f i x e d to e a c h s tu d a n d p l a te w i th 1 /5 0 x 2 .8 m m g a lv. f la t h e a d n a i l

1 8 0 0 m m m in . t o2 7 0 0 m m m a x .

F i x b o t t o m p la t e t o f lo o r f r a m e o r

s la b w i t h n o m in a l f i x in g o n ly

( s e e Ta b le 9 .4 )

3 0 t o

6 0

G a l v. m e t a l a n g le (1 8 x 1 6 x 1 .2 m m )b r a c e f i x e d t o s t u d s w i th o n e 3 0 x 2 .8 m m n a i l a n d t o p la t e s w i t h 2 / 3 0 x 2 . 8 m m g a lv. f la t h e a d n a i l s

N O T E : A l l f la t h e a d n a i ls s h a l l b e g a lv a n iz e d o r e q u iv a l e n t .

0 .8

A 3


49

TABLE 8.18 (continued)

A3

A4

) Metal straps — Tensioned

Te n s io n e d g a lv a n iz e d m e t a l s t r a p w i th m i n . t h ic k n e s s o f 0 .8 m m a n d m i n . n e t s e c t io n a l a r e a o f 1 5 . 2 m m , f i x e d to s tu d s w i th o n e 3 0 x 2 .8 m m g a lv a n i z e d f la t h e a d n a i l

a n d t o p l a te s w i th 3 /3 0 x 2 .8 m m g a lv a n i z e d f la t h e a d n a i l s

2

( o r e q u iv a le n t )


1 8 0 0 m m m in . t o2 7 0 0 m m m a x .

3 0t o6 0

F ix b o t t o m p la t e t o f lo o r f r a m e o r s la b w i t h n o m in a l f i x in g o n ly ( s e e Ta b l e 9 . 4 )

1.5

Type of bracing

Bracing

capacity

(kN/m)


50

Type of bracing

Bracing

capacity

(kN/m)

) 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.

3 0 x 0 .8 m m g a lv . s t r a p 3 / 3 0 x 2 . 8 m m g a lv . f l a th e a dn a i l s ( o r e q u iv a l e n t )t o e a c h e n d to s tu d

3 0 x 0 .8 m m g a lv . s t r a p 3 / 3 0 x 2 . 8 m m g a lv . f l a th e a dn a i l s ( o r e q u iv a l e n t )t o e a c h e n d to s tu d

3 0 x 0 .8 m m g a lv. s t ra p 3 / 3 0 x 2 . 8 m m

n a i l s t o e a c h e n d to s tu d g a lv . f l a th e a d


F i x b o t t o m p la t e t o f lo o r f r a m e o r s la b w i t h n o m in a l f i x i n g o n ly ( s e e Ta b le 9 .4 )

1.5A3

A4



51

(d) Double diagonal tension or m etal strap bra ces

3 0 x 0 .8 m m ( o r e q u iv a le n t ) t e n s i o n e d g a l v. m e t a l s t r a p s n a i l e d t o p l a te s w i t h 4 / 3 0 x 2 . 8 m m g a lv. f la t h e a d n a i l st o e a c h e n d

( o r e q u i v a le n t )

3 0 x 0 .8 m m g a lv. m e ta l s t ra p lo o p e d o v e r p la t e a n d f i x e d t o s tu d w i th 4 /3 0 x 2 .8 m m g a lv . f l a th e a d n a i l s ( o r e q u iv a l e n t ) t o e a c h e n d .A l te r n a t i v e ly, p r o v id e s in g les t r a p s t o b o t h s i d e s , w i t h 4 n a i l s p e r s t r a p e n d , o r e q u iv a l e n t a n c h o rs o r o t h e r fa s t e n e rs

3 0 to6 0

1 8 0 0 m m m in . t o2 7 0 0 m m m a x .

F o r f i x in g o f b o t t o m p la t e t o f lo o r f r a m e o r s la b , r e f e r to C la u s e 8 .3 . 6 .1 0

3 .0

TAB LE 8.18 (con tinued )


Type of bracing

Bracing

capacity

(kN/m)

A3

A4


52

( e ) D i a g o n a l t i m b e r w a l l l i n i n g o r c l a d d i n g M i n i m u m t h i c k n e s s o f b o a r d — 1 2 m m f ix e d w i t h2 / 2 0 5 0 m m l o n g T - h e a d n a i l s .I n t e r m e d i a t e c r o s s i n g s o f b o a r d s a n d s t u d s s h a l l b e f ix e d w i t h o n e n a i l .

2 1 0 0 m m m in .

F o r f i x in g o f b o t t o m p la t e t o f lo o r f r a m e o r s la b , r e f e r to C l a u s e 8 . 3 .6 . 1 0

P e r im e te r n a i l s p a c i n g

3 0 x 0 .8 m m G . I . s t r a p t o e a c h c o r n e r o f b ra c in g p a n e l t y i n g s t u d s t o p la t e s 4 / 2 .8 m m d ia . n a i ls e a c h e n d

27

00

mm

ma

x.

4 0 to 5 0

s

N O T E : N o g g i n g s h a v e b e e n o m i t t e d f o r c l a r i t y . S ( m m )6 04 0

2 .13 .0

T A B L E 8 .1 8 ( c o n t i n u e d )


Type of bracing

Bracing

capacity

(kN/m)

A4


53

Type of bracing

Bracing

capacity

(kN/m)


A4

A3

Minimum plywoodthickness (mm)

Studspacing

mmStressgrade

450 600

No nogging(except horizontal

butt joints)

F8F11F14F27

74.543

976

4.5

One row ofnogging

F8F11F14F27

74.543

74.543

(g) Plywood Plywood shall be nailed to frame using 30 mm2.8 mm galvanized flathead nails or equivalent.

W h e re re q u i r e d , o n e ro w o f n o g g in g s ta g g e r e d o r s i n g le l i n e a t h a l f w a l l h e i g h t

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 between top or bottom plate. Fix bottom plate to floor frame or slab with nominal fixing only (see Table 9.4).

3.4


54

M inim um p lywoodthickness (m m )

S tud sp acing(m m )S tress

grade450 600

F 8F 11F 14F 27

7644

976

4 .5F astener sp acing, s

(m m )T op andb ottom p late: M ethod A M ethod B

15050

V ert ica l edges 150Interm edia testuds

300

F ix ing of b ottomp late to f loor fram e

or s lab

(h) Plywood P lywood sha ll b e na iled to fram e us ing 30 2.8 galvanizedflathead na ils or eq uiva lent.

F or M ethod A, M 12 rods sha ll b e used at each end of sheathed sect ion topp late to b ottom p late/f loor fram e. M ethod B has no rods b ut sheath ing sha llb e na iled to top and b ottom p lates and any horizonta l jo ints at 50 m mcentres .

N O T E: F or p lywood f ix ed to b oth s ides of the wall, s ee C lauses 8.3 .6 .5 and8 .3 .6 .10 .

M ethod A : M 12 rodsas shown p lus a13 kN capacityconnect ion a t m ax .1200 m m centres

M ethod B : A 13 kNcapacity connect ionat each end andinterm ediately a tm ax . 1200 m mcentres

M ethod A6 .4

M ethod B6 .0

TAB LE 8.18 (con tinued )

A3

A4

Type of bracing

Bracing

capacity

(kN/m)



55

M inimum hardboardthickness (mm)

Stud spacing(mm)

T ype

450600

RD 5.5 5 .5

G P 6.4 6 .4

Fastener spacing(mm)

T op andbottom p lates

100

Verticaledges

100

(j) Hardboard Hardboard shall comply with AS/NZS 1859.4 .

Hardboard shall be nailed to frame us ing minimum 25 2.8 mm galvanized nails or equivalent.

Nails shall be located a minimum of 10 mm from the vert ical edges and20 mm from the top and bottom edges .

Panel edges shall be supported by studs .

Intermediatestuds

300

3 .4

NO T ES:

1 Noggings have been omitted for clarity.

2 For fix ing of bottom p late to floor frame or s lab, see C lause 8 .3 .6.10 .

F ix bottom p late to floor frame or s lab with nominal fix ing only (see T ab le 9.4) Refer G UIDE NOT E No.9

TABLE 8.18 (continued )

A2

A4

Type of bracing

Bracing

capacity

(kN/m)



56

Minimum hardboardthickness (mm)

Stud spacing(mm)

Type

450 600

GP 6.4 6.4

Fastener spacing(mm)

Top andbottom plates

50

Vertical edges 100

(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 and15 mm from the top and bottom edges.

Panel edges shall be supported by studs.

Intermediatestuds

300

6.0

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.

Type of bracing

Bracing

capacity

(kN/m)


A2

A4


57

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)


58

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)


59

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.

8.3.6.4 Wall capacity and height modification pg 147


60

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.

8.3.6.5 Length and capacity for plywood bracing walls


61

Bracing shall be approximately evenly distributed and shall be provided in both directions (see Figure 8.5).

8.3.6.6 Location and distribution of bracing

Bracing shall initially be placed in

external walls and where

possible at the corners of the building.


62

W in dd ire c t io n W in d

d ire c t io n

AA

B

B

C

C

D

D

E

T o t a l b r a c i n g s t r e n g t h = A + B + C + D , e t c .

N O T E : A , B , C a n d D a r e t h e d e s i g n s t r e n g t h s o f i n d i v i d u a l b r a c i n g w a l l s .

( a ) R i g h t a n g l e s t o l o n g s i d e ( b ) R i g h t a n g l e s t o s h o r t s i d e

FIGURE 8.5 LOCATION OF BRACING


63

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).

8.3.6.7 Spacing of bracing walls in single storey or upper storey of two storey constructionA3


64

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.

8.3.6.7 Spacing of bracing walls in single storey or upper storey of two storey constructionA3


65

TABLE 8.20

MAXIMUM SPACING OF BRACING WALLS — N3 WIND CLASSIFICATION

Maximum bracing wall spacing (m)

Roof pitch (degrees)Ceiling

depth (m)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.

N3


66

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)

8.3.6.7 Spacing of bracing walls in single storey or upper storey of twoA3


67

Wind d i r ec t io n A

Win d d i re

c t ion B

S p a c in g be tw e e n b ra c in gw a l ls fo r w in d d ir e c t io n B

S p a c in g be tw e e n b rac in g w a l ls fo r w in d d ir e c t io n A

FIGURE 8.6 SPACING OF BRACING


68

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.


69

• 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.


70

DiaphragmDepth

D iaphragm

Length

The above diaphragm, has a large length to depth ratio, (the length being the distance between braces) will not transfer the wind loads effectively.


71

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

DiaphragmDepth

D ia p h ra g m

L e n g th

Diaphragm

Length


72

The same diaphragm, with the wind from the other direction, will transfer loads very effectively because its length to depth ratio is small.

Dia

phra

gmD

epth

DiaphragmLength


73

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.

8.3.6.9 Fixing of top of bracing walls


74

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

8.3.6.9 Fixing of top of bracing walls


75

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.


76

Internal brace not connected to floor diaphragm

Internal brace not connected to ceiling diaphragm


77

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.


78

Metal angle brace as per Table 8.18(c)

Total brace capacity =1.5kN x 2.7m =

2.7 m long

4.05kN

In te rn a l b rac ingw all

Top p la te

E xte rna l w a ll

1 /30 x 0 .8 m m G .I strap w ith 6 /2 .8 na ils each end o fs trap in as perTab le 8.22 (k) =

JD 4 tim ber 4.9kN

Connection used equals the total brace capacity.

Refer to table 8.22 pg 155


79

Metal angle brace as per Table 8.18(c)

Total brace capacity =1.5kN x 2.7m =

2.7 m long

4.05kN

Rafter/Truss

Bracing wall

Provide clearancewhere roof istrussed.

Ceiling battens fixedwith 1/3.05 m m O naileither side of wall

in = JD 4 tim ber

3 ba tten to top p la te connec tionsw ith 2/3 .05 m m O na ils pe r battenas pe r Tab le 8.22 (d)

5.4kN

Connections used equals the total brace capacity.

Refer to table 8.22 pg153


80

AS 1684USER G UIDE 5

G U I D E T O T H E U S E O F A S 1684

Fixing of Top of Bracing Walls

Connect braced wall to external wall using 2 straps as perTable 8.22 (k). For JD 4 pine, 4/2.8 d ia nails required each end of each strap to achieve 6.6 kN.

Example 1 - Strapping to external walls

Brace6.12kNcapacity(1.8m x 3 .4kN /m )


81




B race5 .76kNcapac ity(0 .9m x 6 .4kN /m )

Connect braced w all to 6 ceiling jo ists using 2/3.05 dia skew nails per jo ist as per Table 8.22 (i). For JD 4 pine, capacity = 6 x 1.1 = 6.6 kN

Example 2 - Nailing floor or ceiling joists to walls

NOTE: The top plate in the wall m ust provide a continuous tie from the braced section of wall to where the top p la te is connected to the floor, ceiling or roof diaphragm.


82




Connect braced wall to ceiling jo ists or truss bottom chords w ith b locking as per Table 8.22 (j) 4/3.05 dia nails to each block + one strap to the external wall w ith 4/2.8 d ia nails each end of strap.

Example 3 - Combinations

B race6 .75kNcapac ity(0 .9m x 7 .5kN /m )

NOTE: The top plate in the wall m ust provide a continuous tie from the braced section of wall to where the top p la te is connected to the floor, ceiling or roof diaphragm.


83

Nails

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

Screws

No.14Type 17

12 8.3 5.9 8.3 5.9 4.3

(a)

P r o v id e c le a r a n c ew h e r e r o o f i s t r u s s e d

B r a c in g w a l l

9 0 x 3 5 m m

t r i m m e r o n f l a t

F 8 o r9 0 x 4 5 m m F 5

4 / 7 5 m m n a i l s a s p e r t a b le o r 3 / N o . 1 4

t y p e 1 7 s c re w s

2 / 7 5 m m n a i l s e a c h e n d a s p e r t a b l e o r 2 / 7 5 m m N o . 1 4 t y p e 1 7 s c r e w s

NOTE: For trussed roofs, nails or screwsthrough the top plate shall be placed inholes that permit free vertical movementof the trusses.

TABLE 8.22

FIXING OF TOP OF BRACING WALLS

Shear capacity (kN)

Unseasoned

timber

Seasoned

timber

Rafters, joists or trusses

to bracing wall

J2 J3 J4 JD4 JD5 JD6

A3

A4


84

Screws

1/No.14Type 17

4.8 3.5 2.5 3.5 2.5 1.8

2/No.14Type 17

9.7 6.9 4.9 6.9 4.9 3.6

3/No.14Type 17

13 9.3 6.6 9.8 7.4 5.4

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 12 8.0 5.1 8.4 5.9 4.0

(a)

P r o v id e c le a r a n c ew h e r e r o o f i s t r u s s e d

B r a c in g w a l lS c r e w s o r b o l t sa s p e r t a b le

T r i m m e r :o n e b o l t : 9 0 x 3 5 m m

t w o b o l t s : 1 2 0 x 3 5 m m

F 8 o r : 9 0 x 4 5 m m F 5

F 8o r : 1 2 0 x 4 5 m m F 5

F r a m in g a n c h o rs( le g s n o t b e n t )6 / 2 .8 m m n a i l se a c h f a c e

NOTE: For trussed roofs, screws or bolts through the topplate shall be placed in holes that permit free verticalmovement of the trusses.

2/M12 13 9.3 6.1 9.8 7.0 4.9

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall


(b)


85

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall


Nails

3.05 6.6 4.7 3.4 5.0 4.2 3.1

(c)

9 0 x 3 5 m m b r id g i n g p ie c e

F 8

B r a c in g w a l l

Tw o lo o p e d s t r a p s ( 3 0 x 0 . 8 m m G . I . )4 / 2 .8 m m n a i l s e a c h e n d a n dt o b r id g i n g

3 / 7 5 m m n a i l sa s p e r t a b le

3 0 (m a x )

G a p b e tw e e nt o p p la t e a n d t ru s s

3.33 7.4 5.3 3.7 5.5 4.6 3.5


86

(d)

R a f te r o r t r u s s

B ra c in g w a l l

P ro v id e c le a ra n cew h e re ro o f is t r u s se d

2 /3 .0 5 m m n a i ls p e r b a tte n , 3 .5 m m h o le s s h a l l b e d r i l le d in b a t te n to a l lo w fo r t r u s s d e f le c t io n

C e i l in g b a tte n s f ix e d w i th 1 /3 .0 5 m m n a i le ith e r s id e o f w a l l

2.5 1.8 1.3 1.8 1.5 1.1

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall



87

Nails

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

2/No.14Type 17

9.7 6.9 4.9 6.9 4.9 3.6

(e)

B r a c i n g w a l l

G a p t o t r u s s

9 0 x 3 5 m m F 8 o r 9 0 x 4 5 m m F 5 t r im m e r

S h e a r b lo c k sn a i l e d , b o l t e d ,o r s c r e w e da s p e r t a b l e

N a i l in g p la te s o r f r a m in g a n c h o r ( le g s n o t b e n t ) t o e i t h e r e n d o f n o g g i n g 6 / 2 .8 m m n a i l s e a c h fa c e o r 2 /N o . 1 4 T y p e 1 7 b a t t e n s c r e w s e i t h e r e n d

3/No.14Type 17

13 9.2 6.6 9.8 7.4 5.4


TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall


A3

A4


88

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall


A4

NOTE: For truss roof, nails through thetop plate shall be placed in holes thatpermit free vertical movement of thetrusses.

Nails

2/3.05 1.4 1.1 0.77 1.1 0.90 0.66

(i)

B r a c i n g w a l l

R a f t e r , c e i l i n g jo is t , o r b o t t o m c h o r d

2 s k e w n a i l s p e r c r o s s in g s iz e a s p e r t a b l e

2/3.33 1.7 1.2 0.85 1.2 1.0 0.75


89

Nails

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

2/No.14Type17

9.7 6.9 4.9 6.9 4.9 3.6

(j)

B ra c in g w a ll

B loc k ing p ie c e sla rg e e n o u g h toa v o id s p l i t t in g

G a p be tw e e n top p la te a n d t ru s s

N a ils , sc re w s o r b o lt s a s p e rtab le b lo c k s to b e b o th s id e so f ra f te r o r b o t to m c h o rd

3/No.14Type17

15 10 7.4 10 7.4 5.4

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall



90

Straps Nails

4/2.8 4.3 3.1 2.2 3.3 3.0 2.1

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

(k)

I n t e r n a l b r a c i n g w a l l

To p p la t e

E x te r n a l w a l l

2 /3 0 x 0 .8 m m G . I s t r a p s w i t h n u m b e r o f n a i l s e a c h e n d o f s t r a p s a s p e r t a b le

2

6/2.8 13 9.3 6.6 9.8 8.1 6.1

TABLE 8.22


Shear capacity (kN)

Unseasoned

timber

Seasoned

timber


to bracing wall



91

The bottom plate of timber-framed 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

8.3.6.10 Fixing of bottom of bracing walls pg 155


92

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.

8.3.6.10 Fixing of bottom of bracing walls


93

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 be used.

8.3.6.10 Fixing of bottom of bracing walls


94

TABLE 8.23 P153- AS1684.2 TABLE 8.24 P149- AS1684.3

UPLIFT FORCE AT ENDS OF BRACING WALLS

Uplift force at ends of bracing walls (kN)

For bracing walls rated at (kN/m) capacity

Wall

height

(mm) 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 8 10

2400 2700 3000

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.


95

M10 cup-head

16 14 10 10 7 5

(a)

M 1 0 cu p h e a d b o l ts o r N o . 1 4 Typ e 1 7 b a tte n s c re w s a s p e r ta b le , w i th m in . 3 8 m m p e n e tra t ion in to f lo o r in g a n d /o r jo is t

2/No.14 Type17 screws

11 8.4 4.8 9.0 7.2 5.4

TABLE 8.24

FIXING OF BOTTOM OF BRACING WALLS

Uplift capacity (kN)

Unseasoned

timber

Seasoned

timberFixing details



96

Bolts

M10 18 18 18 15 12 9

(b)

B o l t s a s p e r t a b le

D o u b le jo is t o r 4 5 0 m m l o n g f u l l d e p t h c le a tn a i l e d t o jo i s t w i t h 6 /7 5 x 3 .1 5 m m n a i l s

M12 27 27 26 20 16 12

TABLE 8.24



Unseasoned

timber

Seasoned




97

M10 bolt

18 18 18 15 12 9.0

(c)

B e a re r o r u n d e rb a t te n

S o lidn o g g in g

B o lt a s p e r ta b le

M12 bolt

27 27 26 20 16 12

TABLE 8.24



Unseasoned

timber

Seasoned




98

A4

2/No. 14Type 17screws

12 8.3 5.9 8.3 5.9 4.3

3/No. 14Type 17screws

17 13 9.0 13 9.0 7.0

(d)

1 2 0 x 70 m m b r id g in g p ie c e o n f la t

M 1 0 b o ltS c rew s o rc o a c h (1 25 m m lo n g )

s c re w s

e a c h e n d o fb r id g in g p ie c ea s p e r ta b le

2/M12coachscrews

18 18 13 15 12 9.0

TABLE 8.24



Unseasoned

timber

Seasoned




99

M10 bolt

18 16 11 15 12 9

(e)

1 0 0 x 5 0 m m b r id g in g p ie c e o n e d g e

B o lt a s p e r ta b le

2 n a i l in g p la te s e a c h e n d o f b r id g in g , le g s n o t b e n t, w i th 6 /2 .8 m m n a i l s to e a c h fac e

M12 bolt

22 16 11 18 15 11

TABLE 8.24



Unseasoned

timber

Seasoned




100

M10 bolt

18 18 18 15 12 9

(f)

M12 bolt

27 27 26 20 16 12

H o o k e d o r b e n ta n c h o r b o l t a s p e r t a b le

1 8 0 m m m i n .

TABLE 8.24



Unseasoned

timber

Seasoned




101

(g)

F i r e d ,s c r e w e d ,c h e m ic a l o r e x p a n d i n gm a s o n r y a n c h o r

Refer to manufacturer’s specifications

TABLE 8.24 (continued) P154- AS1684.2 TABLE 8.24 P150- AS1684.3

TABLE 8.24



Unseasoned

timber

Seasoned




102

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.

8.3.7 Roof Bracing pg 158

8.3.7.1 Pitched roofs (coupled and non-coupled roofs)


103

(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 accordance with engineering principles.

8.3.7.1 Pitched roofs (coupled and non-coupled roofs)


104

R i d g e b o a rd

R a f te r

G a b l e e n dM i n . 1 9 x 9 0 m m o r 2 5 x 7 5 m m b r a c e a t a p p ro x i m a t e ly 4 5 to r a f t e r s o n b o t h s id e s o f r i d g e

A l te r n a t i v e b r a c in g : o p p o s in g b ra c e s f r o m r id g e b o a r d t o in t e r n a l w a l l s a t a p p r o x i m a t e ly 4 5

FIGURE 8.9 GABLE ROOF BRACING

as 1684 section 8 - racking and shear forces 1 section 8 - racking (bracing) and shear forces week...

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