The general details given in Clauses 9.2.2 to 9.2.11 shall apply to all connections and fixings.
9.2.2 Corrosion protection and steel grade
All metal used in structural timber connections shall be provided with corrosion protection appropriate for the particular conditions of use.
Where corrosion protection of steel is required it shall be in accordance with AS/NZS 4791, AS/NZS 4534, AS 1397 and AS 1214. The level of corrosion protection provided shall take into consideration weather exposure, timber treatment, moisture and presence of salt.
The minimum corrosion protection that shall be applied to metal straps, framing anchors and similar structural connections shall be Z 275. The minium thickness of metal strap shall be 0.8 mm.
Where other types of corrosion protection are provided, they shall satisfy the requirements of the relevant authority.
The min. steel grade for metal strap, framing anchors and similar structural connection shall be G 300. The grade of all other metal components shall be in accordance with the relevant Australian Standards.
9.2.3 Straps, bolts, screws, coach screws and framing anchors
Straps, bolts, screws, coach screws and framing anchors shall be manufactured in accordance with, or shall comply with, the material requirements of the relevant Australian Standards.
9.2.4 Steel washers
The size of steel washers shall be determined from Table 9.1.
Circular washers of equivalent thickness and with the same net bearing area are also permitted to carry the same full design loads. For thinner washers or washers with smaller net bearing areas, the design loads shall be reduced in proportion to the reduction of thickness and net bearing area, that is, less the hole diameter.
TABLE 9.1 STEEL WASHERS
Bolt or coach screw diameter (mm) Washer size (mm)
M10 cup-head Standard
M12 cup-head Standard
M16 cup-head Standard
M10 bolt or coach screw 38 × 38 × 2.0 M12 bolt or coach screw 50 × 50 × 3.0 M16 bolt or coach screw 65 × 65 × 5.0
9.2.5 Drilling for bolts
Bolt holes in unseasoned timber shall be 2 mm to 3 mm greater in diameter than the bolt diameter, and for seasoned timber they shall be 1 mm to 2 mm larger than the bolt diameter. Bolt holes in steel shall provide a snug fit; that is not more than 0.5 mm larger than the bolt diameter.
9.2.6 Drilling for coach screws
Drilling for coach screws shall be as follows: (a) Hole for shank—shank diameter + 1 mm. (b) Hole for thread—root diameter.
The minimum penetration of the threaded portion of screws and coach screws into the receiving member shall be not less than 35 mm for screws and 5 times the diameter of coach screws, unless otherwise noted.
9.2.8 Framing anchor and strap nails
All nails used for framing anchor and straps shall be corrosion protected flat-head connector nails. Clout shall be not used for this purpose.
9.2.9 Alternative metal strap size
Except for diagonal metal strap braces, metal strap with a minimum net section of 21 mm2 may be used in lieu of 30 × 0.8 mm strap.
9.2.10 Joining of top plates
Top plates in walls shall be joined by one of the methods shown in Figure 9.2 for the relevant wind classification.
Nogging as for top plate 3/3.05 mm nails each side of joint
Stud Ribbon plate construction 1200 mm min 2/75 3.05 mm
nails at each stud
Top plate
Stud Stud
Plate connector
(i) (ii) (iii)
(a) Suitable for wind classification C1
Nogging required where join is between studs 80 mm 50 mm 3/No 14 type 17 batten screws or 2/M10 cup-head bolts either side of join
Nogging required where join is between studs 200 mm 2/30 x 0.8 mm G.I. straps 6/30 x 2.8 mm nails each end of each strap
Nogging required where join is between studs
2/framing anchors legs not bent 6/30 x 2.8 mm nails each end of each anchor
(iv) (v) (vi)
(b) Suitable for wind classifications C1 to C3 FIGURE 9.2 JOINING OF TOP PLATES
9.2.11 Tie-down of members joined over supports
Unless shown or illustrated, the uplift capacities given in the relevant details in Tables 9.16 to 9.25 apply to members that are continuous over supports. Where members are joined over supports, consideration shall be given to the effect of reduced end distances for connectors (bolts, screws, etc.).
Where members are joined over supports such as shown in Figure 9.3(b), the uplift capacity shall be equal to the uplift capacity as if there were no join over the support as the full strength of the connection is maintained.
NOTE: As a general guide, where members are joined over supports, such as shown in Figure 9.3(a), the uplift capacity should be equal to half the uplift for the number of connectors (i.e., bolts) shown as the required end distances are reduced.
50 min. 50 min. 50 min. 50 min. (Halved Joint) (a) Type 1 (Mitred joint) 2 straps 2 or 4framing anchors (b) Type 2
FIGURE 9.3 JOINING MEMBERS AT SUPPORTS
Fixing and tie-down requirements shall be provided, where required, in accordance with the procedure set out in Figure 9.4.
FIGURE 9.4 FLOW CHART SHOWING PROCEDURE FOR TIE-DOWN REQUIREMENTS