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南非土木工程施工标准 CT2部分：屋顶木结构 英文原文节选 20100079 2-9 |
4.6.2.2.2 When trusses are lifted by hand, care shall be taken to prevent excessive lateral bending
when sliding them over walls and when tipping them upright on the walls (see figure 3). Where
cranes are used, the following rigging shall be used to lift single trusses and groups of trusses into
position:
a) for trusses that have a span of up to 6 m, a single pick-up point shall be used to pick up not more
than three trusses as shown in figure 4;
b) for trusses that have a span of between 6 m and 9 m, two belt slings with hooks or a looped sling
shall be used such that the distance between slings is approximately half the length of the truss
and the angle between the two slings is less than 60° as shown in figures 5 and 6;
c) for trusses that have a span of between 9 m and 18 m, a spreader bar that is sufficiently rigid so
as not to bend sideways when the truss is lifted, and is between two-thirds and three-quarters
the length of the truss, shall be used with slings at suitable intervals as shown in figures 7 and 8;
and
d) for trusses that have a span of between 18 m and 30 m, an inflexible "strongback" secured to the
truss at intervals of 3 m or less, that has a length of at least two-thirds of the truss span, shall be
used as shown in figures 9 and 10.
4.6.2.2.3 When using rigging, care shall be taken not to damage the timber and connectors at the
pick-up points.
NOTE Canvas slings are preferable to chain slings.
4.6.2.2.4 Multiple trusses that comprise identical trusses joined side by side should preferably be
assembled on the ground to form a complete unit. Where a multiple truss is too heavy to lift or
handle, it may be assembled in situ.
4.6.2.2.5 Once trusses have been lifted into position, they shall be checked for any damage that
might have occurred during the lifting and handling operations. A damaged truss shall be removed
or repaired so that the truss as erected does not compromise its design intent or performance in
use (or both).
NOTE A competent person, as defined in SANS 10400, should assess any damage to the trusses and review
the suitability of the repairs.
4.6.2.3 Temporary bracing
4.6.2.3.1 The first truss shall be lifted into position onto the wall plates and temporarily braced to
the ground or wall plate (see figure 11) with grade 5 timber that has a minimum size of
76 mm × 38 mm or poles with a diameter of not less than 100 mm, or supported against the gable
end so that the truss is both straight and vertically plumb. Thereafter, the next few trusses may be
lifted into position at their correct spacing and fixed in position with temporary runners and bracing
(see figure 12).
4.6.2.3.2 The erected trusses shall be lined up, levelled, plumbed and straightened before the
installation of the permanent web and rafter bracing. Thereafter, the remainder of the trusses may
be erected, ensuring that temporary bracing and runners are fixed as the erection of trusses
proceeds.
SANS 2001-CT2:2009
Edition 1.1
16
4.6.2.3.3 If it is necessary to insert wedges or packs between the wall plate and the bottom chord,
wedges shall be installed from both sides. Where required, packs or wedges should be made of
rectangular blocks of timber at least the same width as the wall plate.
NOTE The diagonal members brace the truss against lateral movement so that it does not change its shape.
Bracing ensures that
● trusses erected correctly will remain vertical,
● the top and bottom chords will remain straight,
● truss spacing will remain constant, and
● compression members do not buckle.
4.6.2.4 Permanent bracing
Upon completion, all trusses shall be checked for straightness, plumbness and that they are level,
and shall be adjusted, as necessary, on the wall plate. The remainder of the permanent bracing
shall be fixed.
4.6.3 Erection of rafters and purlin beams
Rafters and purlin rafters or purlin beams (or both) shall be erected straight and plumb at the
required slope (see figure 13). Where 50 mm × 228 mm rafters are used, the timber shall be free
from any serious warping which might affect the straightness and plumbness of the rafters when
fixed in position.
4.7 Installation of battens and purlins
4.7.1 Battens and purlins shall be continuous over at least three rafters (i.e. two rafter spacings)
and shall be fixed to every rafter that they cross. Battens of size 38 mm × 38 mm shall be nailed to
rafters with 75 mm wire nails, and battens of size 38 mm × 50 mm shall be set on edge with 90 mm
wire nails. Purlins shall be fixed to rafters in accordance with figure 14. Care shall be taken not to
split any of the members during the nailing process.
4.7.2 The ends of battens and purlins shall be sawn square and butt-jointed centrally over the
rafter member so as to provide suitable bearing and fixing. Alternatively, battens may be spliced in
close proximity to rafters by means of nailed splices or connector plates, as shown in figure 15.
4.7.3 Joints in battens shall be arranged so that not more than one batten in any three is joined
(spliced) on any one rafter (see figure 16(c)).
4.7.4 Purlins shall be spliced in accordance with figure 16. Splices shall be located in close
proximity to rafters and shall be staggered so that there is not more than one splice in three
consecutive purlins. Purlins and rafter splices shall not be located within 1,5 m from the gable ends.
4.8 Ceiling assembly
Brandering of size 38 mm × 38 mm required to support gypsum plasterboard, fibre-cement board or
similar board shall be securely spiked to the supporting timbers with 75 mm wire nails at centres
that do not exceed 450 mm. Cross brandering shall be cut in between the longitudinal brandering
and skew nailed to the same, using 75 mm wire nails at centres that do not exceed 900 mm.原件下载： 
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