Tower Crane Virtual Conference: Building skyscrapers7 April 2021
Bosko Mujika, R&D manager at Jaso Tower Cranes and Andrew Coffin, Cost & Engineering manager at Australian lifting equipment provider and Jaso’s distributor Titan Cranes talked about a solution the companies co-developed for high rise construction sites with limited usable space.
Mujika talked about the increased rate of urbanisation, which has made space the most precious asset in cities and is leading to the construction of more high rise buildings. He said there is pressure for fast erection process and hoisting speed, posing challenges to productivity and safety.
Jaso’s R&D department has been working closely with clients to find solutions. “Some examples of this collaboration are: the high capacity crane models developed for PPVC, the high speed hoisting mechanisms offering up to 300tm per minute, recovery cranes for dismantling tower cranes for high buildings, and special internal climbing systems,” said Mujika.
The manufacturer worked together with Titan to develop the Lift Shaft climbing system, also called the three beam climbing system. The crane is positioned within the building’s concrete core and climbs using a three beam climbing system. “The climbing is very fast and safe, it is not necessary to move collars between different levels. Also the hydraulic system has been designed taking into account safety and serviceability. For example, the cylinders for moving the outriggers can be replaced on site, with a crane erected on the beams without any major dismantling.”
Titan’s Coffin said for projects with space constraints, the option to locate a crane central to the building footprint without requiring any slab penetrations improves constructability and efficiency.
Titan was contracted by LendLease to provide the entire lifting scheme for the International Towers Sydney, which consists of three commercial skyscrapers that form the core of a residential, retail and leisure development. The three towers range from 168m tall through to 217m. Multiple cranes were deployed, at some point 12 cranes operated simultaneously.
“Each tower needed multiple hooks and LendLease intended to construct the core well in advance of the floor slabs. This meant an internal core climber was the ideal solution. This meant internal and external cranes could work close to each other safely. On one of the towers a builders hoist was placed in the same core as the tower crane between the chocks, maximising the use of available space on site.
Coffin added that potential hurdles of using an internal climbing sequence were considered when developing the chock system; a chock is a frame that is used to transfer the loads from the crane to the building. “Our preference was the rolling system. The chocks we designed pushed the loads into the corners of the Lift Shaft. This minimises the implications on the structure in terms of sheer, and reduces the necessary sheer reinforcement needed in the core. We found the most efficient design used adjustable rollers in the shaft corners to allow for core construction tolerances during climbs and bearing plates in each corner for in service conditions.”
In terms of tolerance associated with the lift core construction, Coffin said there is a theoretical tolerance equating to approximately 30mm on each side which is more than it sounds. “With Jaso we developed adjustable rollers, which in conjunction with steel packers, can take up to this tolerance and more.
“Our collaboration has lead to the development of a new system that allows the use of high capacity cranes such as the Jaso J438PA.2R to be placed on top of this climbing system. With builders methodologies shifting towards modularisation and lifting larger compartments, this system allows us to offer solutions to projects that would have previously been beyond our capacity.”