Posi-STRUT Truss System
.
Rafter & Purlin Truss Detailing
Rafter End Details
There is a large number of possible details for the ends of rafter trusses depending on style of eaves and fixing requirements.
Some typical end support construction details suitable for Posi-STRUT rafters up to around 30 degrees pitch are shown as follows:
Purlin End Details
Depending on the end support, there is a wide number of possible end fixing details for Posi-STRUT purlins.
Posi-STRUT purlins may be set out vertically upright between supports, or perpendicular to the pitched rafter support. In the latter case, where the rafter pitch exceeds 5 degrees, it is necessary to fix both top and bottom chords at the support and to provide sufficient lateral support at midspan to prevent truss twisting under gravity.
Some common details (by no means exhaustive) for ends of Posi-STRUT purlins are shown as follows:
Stability Bracing
The following details cover ancillary bracing for truss stability only, and not roof bracing for the total roof or building structure, which will have to be separately designed.
The top chord stability is provided by diagonal strip bracing fixed to both purlin and rafter trusses. The bottom chord is restrained by runners and fly braces at 1.75m centres maximum for 70 wide chords and 2.25m centres maximum for 90 wide chords.
