Pryda Advises On Giant Span Truss Construction For Aged Care Facility – November 2012

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Multi facets of Pryda expertise and equipment have been successfully brought together with Keith Timber for the manufacture of some of the longest span prefabricated timber roof trusses ever built and used in a large South Australian aged care facility at Gawler north of Adelaide.

Earlier this year, builders Warburton Nominees approached South Australian Pryda fabricator Keith Timber Group (situated at Keith) to supply roof trusses for the approximately 80-bed aged care facility, a two-storey building where the first floor was supported by a suspended concrete slab with timber wall frames.

The proviso was that no internal bearings were to be incorporated into the building design, so all roof trusses had to clear the entire span without any other means of support.

In all, there were seven sections of trusses involved in the construction process. Three of those contained roof trusses measuring a massive 19 metres to 23 metres long and four metres high, while the remaining sections were a more manageable nine to 11.5 metres.

Keith Timber Group was well positioned to construct the super long prefabricated timber roof trusses, having in recent years installed a Hundegger fully automated saw and Pryda C4 table press that was able to cope with the project.

A Pryda fabricator since 1995, the company mainly supplies prefabricated roof and floor trusses and wall frames to the South Australian residential building market but is more than happy to diversify into commercial construction.
Many commercial project engineers are now acknowledging the cost effective benefits of prefabricated timber roof trusses, particularly where the building doesn’t require the trusses to stabilise the building.

Design of the giant spans was carried out using the latest Pryda Build i software, which enables the roof truss configuration to be seen in an interactive revolving 3D landscape that greatly increases detailer efficiency.

Keith Timber Group then consulted closely with Melbourne Pryda engineers who suggested strengthening each large span truss using double or triple 35mm thick timber. The company also used bigger nailplates and changed web profiles to meet the demands of the much bigger truss construction.

Pryda engineers recommended off panel point splices that allows chords to be flipped end for end where possible to offset splices within the laminated truss, explained Keith Timber truss detailer Steve Hancock.

The trusses were so large that each one had to be individually and manually manufactured on the press using the whole table, which normally is set up for two jobs at a time.

Once completed, the trusses were ejected from the table press and moved out of the factory by the out feed, before being manually shifted to the pack where they were nail laminated.

Extendable trailers and wide load escorts were used to transport the largest spans from Keith to the Gawler building site. The first section of trusses was transported when required in mid-October (with the final delivery a month later) and the Adelaide-Melbourne highway closed at Murray Bridge town, to enable the trucks to pass safely over the bridge.

On site, the giant trusses were lifted in to place using a 16-metre spreader bar and multiple slings to maintain their integrity.