JMG Engineers & Planners (JMG) were engaged to undertake modifications to the existing Wilsons Shed for INCAT Tasmania in late 2016, with works being undertaken in 2017. The modifications were to allow the production of a new vessel and included raising a section of the existing portal frame building by nominally 2 metres. JMG were the original designers of the building back in 1998.
Several scenarios were investigated based on speed of construction and cost. Undertaking the works between the construction of vessels was a critical element to the design and JMG worked closely with the Builder John Smith to optimise the final design. The design involved ‘splitting’ the portal frame at the eave and creating new ‘infill’ section to be bolted back in. Bolting was chosen over welding where possible to limit time onsite as all bolt holes etc could be undertaken prior to lifting the roof, in fact the infill sections were bolted onto the underside of the existing haunches prior to removing the portal beams. The roof was lifted 2 bays at a time and as the infill sections were pre-installed the removal and installation could be undertaken in one movement, with the Builder only having to bolt them back in place whilst supported by the cranes.
Consideration of the existing portal columns also had to be considered when the beams were removed, these were temporarily propped back so they did not deflect and hence aligned with the bolts when re-installing. The whole works were closely planned and detailed with the Builder and Client to ensure all risks were reduced and all possibilities considered and eliminated to ensure that there were no surprises or hold ups once lifting commenced.
The project went together extremely well, without any complications and in within the time allocation between boat builds.