Huge Concrete Pour for Central City
Huge Concrete Pour for Central City
The largest concrete pour in the Christchurch CBD since the earthquakes gets under way at 2.30am on Saturday at Antony Gough’s $140 million The Terrace.
Almost 900 cubic metres of concrete – the equivalent of 180 standard concrete trucks - will be poured on the central city site over an eight-hour period on Saturday morning.
The pour will allow the erection of columns and beams on the second of four buildings under construction for the initial stage of The Terrace development and begin to provide a strong sense of the scale and shape of the finished building.
The Terrace project – the CBD’s first major rebuild project - will transform the iconic site bounded by Oxford Terrace, Cashel Mall and Hereford Street into a dynamic hub of retailers, hospitality providers, office space, a boutique hotel and car-parking.
“It is coincidental but highly symbolic that this major concrete pour is taking place on the third anniversary of the catastrophic 2011 earthquake,” said Antony Gough.
“It is a sign of significant progress within the heart of the city and it is important for everyone to feel that our city is being rebuilt.
“The Terrace is a hugely exciting project, combining central city hospitality, with retail and significant commercial activity, including Westpac as an anchor tenant,” he said.
Stage One of The Terrace will include three buildings facing onto Oxford Terrace and a fourth facing Hereford Street. These buildings will house retail, hospitality and office tenants and they are scheduled for completion by late 2014- early 2015.
The completed project will employ up to 2,000 people on site, occupying 45,000 square metres of built space. Laneways, courtyards and roofed terraces will connect the eight buildings and central courtyard with the different elements of the development.
The Terrace and Ballantynes will bookend and anchor the revitalised city centre, with The Terrace providing important connections and access to the Avon River, the City Mall and the rest of the central city.
The concrete raft foundation has an area of 1,267 square metres and contains over 155 tonnes of reinforcing steel.
Due to the large number of potential hospitality tenancies to be located within the building all the underground building services have been installed within the raft. That includes:
• Water supply
• Fire sprinkler/hydrant mains
• Greasy waste
Two large grease interceptors have been cast 3 metres below the raft to separate greasy waste from hospitality tenancies before the water is discharged.
The reinforced concrete raft can be likened to a very stiff mattress of concrete sitting on the ground. The building sits on top of that “mattress.” The structural engineering advantage of using a stiff concrete raft foundation is that the foundation system is extremely robust in terms of resisting damaging foundation settlements following future earthquakes and is very easy to recover from settlement if it should happen.
Structural concrete rafts are typically between 600mm and 800mm thick for buildings 3 to 5 stories. They have the ability to minimise differential settlement and hence limit the effect on the super structure. The raft foundations provide a good solution by integrating with the low damage sliding hinge joint structure and strongly anchoring the columns to the ground.
Overall the raft acts as one large foundation pad that has a benefit of reducing the footprint pressure on the ground and lessens the stress on the subsoils. It is reinforced top and bottom to resist bending forces from the building weight and to also resist the forces from earthquake loads. A sophisticated finite element analysis is undertaken to combine all loadings and earth pressures and the reinforcement is designed accordingly.