Gillespie Crane Services (Gillespies) won the 2017 Lift of the Year in the <20t category for its lift of a 13.4t cantilever roof as part of Delta Demolition’s demolition of the iconic Imax Theatre at Darling Harbour (Sydney), writes Greg Keane.
Gillespies worked closely with Delta in the tender phase of the project, providing a safe methodology for the roof’s removal.
Complicating the work was the tight access for heavy cranes and transport, with the Imax Theatre located between two raised motorways (there was only 5m of separation to one motorway deck). Other challenges were the high vehicular and pedestrian traffic, environmental sensitivity of the area due to its proximity to the harbour, and the need to work at heights.
Gillespies worked closely with Delta and Coffey Structural Engineers (which advised on lift points and signed off on Gillespies’ lift plan) to devise a nine-point lifting method for handling the asymmetric roof.
A 350t Liebherr LTM1350 AT crane with Y Guy and 100t of counterweight was used for the lift, and rigging included soft slings, four spreader bars and eight 10t chain blocks. This complex arrangement allowed the roof to be lifted evenly despite its complex shape. A 39m boom lift was used for rigging the lift.
The load was taken by the crane while the cantilever roof was still attached to the main structure, and then the supports were cut. As a precaution, two 9t lever hoists connected the roof structure to the main building to minimise swing when the load came free, and the two lanes of traffic closest to the lift were closed for the duration of the lift. These precautions were not called upon as the roof moved only 20mm after the supports were cut.
The crane worked at a 20m radius and had a SWL of 35.1t at that distance. While the roof section itself weighed 13.4t, a 50% allowance was applied for demolition work to allow for extra loading when supports are cut, and the rigging added an extra 10t, so that the crane effectively worked at 86% capacity for the lift.
The roof was lowered onto an area on site where it was cut up by a 45t excavator with shears, and the metal was then transported off site for recycling.
The crane was set up on site on January 12, 2017, and the rigging was tested on the following day. This was undertaken as, with an uneven load to be lifted, the rigging with no load is also uneven and testing ensures that the spreader bars will all be level when under load. This necessitates adjustment of the chain blocks to ensure this, with work taking place progressively from the lift point closest to the crane to the lift point furthest from the crane. The crane was derigged after testing.
The actual lift took place on the following day, but the rigging adjustments from the test were retained to save time during the lift. Rigging commenced at 2am and the actual lift commenced a little after 6am.
The LTM1350 actually spent three weeks on site, also assisting with demolition of the main roof when rigged with a luffing fly jib, and Gillespies also supplied a 250t AT crane to the project.
As iconic as the Imax Theatre was, it is being replaced by a 25-storey hotel and serviced apartment development known as The Ribbon that is arguably even more iconic in shape (although the humble author sees the profile as more resembling the fuel tank of a Harley).