Sydney's $6.1-Billion Barangaroo South Planned as Grand Model for Carbon-Neutral Development
The first big challenge in construction was creating the watertight excavation, says Rocco Bressi, senior structural engineer, Lend Lease, Sydney. This work was critical since the water table is a meter below the surface, rendering the basement “basically under water,” Bressi says.
Before beginning sitework, crews tore down the aging wharves, then dumped fill into the harbor to reclaim the area.
Before beginning site excavation, crews installed the 700-m-long, anchored-back structural perimeter diaphragm wall. To minimize water flow from one side of a wall to the other, all panels extend 6 m to 30 m below ground and are socketed into sandstone about a half-meter.
A test bore revealed some obstructions, including old piles and wall structures from the previous port facilities and concrete backfill. In some places, the obstructions were removed.
To expedite the fast-tracked project, some crews began piling work in the unexcavated area, while others excavated the two-story basement at another part of the site.
In March, hydrostatic slab construction began at the lowest basement level. Basement and ground-floor diaphragm slabs will restrain and stabilize the perimeter wall system, says Bressi.
The first office tower and the park are scheduled for completion in mid-2015. The other two towers as well as two waterfront apartment buildings are due for completion at the end of 2015 or in early 2016. The remaining buildings are expected to be finished between 2018 and 2022.
In the office-tower superstructure, floors will be reinforced using a post-tensioned concrete-slab system to allow for an overall shallow structural depth, thereby providing 2.9-m floor-to-ceiling heights rather than the typical 2.7 m, Bressi says.
Even the structural system will contribute to the building’s minimized carbon footprint. To conserve material, columns and core walls will consist of high-strength concrete up to 100 megapascals, Bressi says. “This allows us to use less material and construct thinner walls,” which adds up to a more sustainable project, he notes.
