Recycled Skyscraper - World Building of the Year

[jaxlongtimer]

This is an amazing story of a world first, a 49 story, 1970's skyscraper, "upcycled" into a brand new larger skyscraper.  If you open the full article there is a neat time lapse of how it was done.  The article also describes technical hurdles such as matching up to the shrinking and moving of the original structure.

Once Sydney's tallest building, the AMP Centre was showing its age. The outdated 1970s structure had come to the end of its lifespan, and the tower's owners wanted to replace it with something bigger, better and more energy-efficient.

But demolishing high-rises comes with significant environmental costs, from construction waste to the CO2 emitted by heavy machinery. So in 2014, Australian investment firm AMP Capital launched an architectural competition with an unprecedented brief: To build a new skyscraper without demolishing the old one.

Dubbed the world's first "upcycled" high-rise, the resulting tower opened earlier this year and, on Friday, was named World Building of the Year 2022. Standing at 676 feet tall, the vastly expanded 49-story skyscraper, now known as Quay Quarter Tower, retained more than two-thirds of the old structure, including beams and columns, as well as 95% of the original building's core.

"The tower was coming to the end of the end of its life, in terms of viability... but the structure and the 'bones' can actually last a lot longer," said Fred Holt, a partner at the Danish architecture firm behind the design, 3XN, in a video interview. "You can't always retain everything. But if you can retain the structure — and that's where the majority of your embodied carbon is — then you're lowering your footprint."

After removing unsalvageable parts of the old building, construction workers erected a new structure beside it that they then "grafted" onto what remained. A contemporary glass facade was wrapped around them both to create a single skyscraper. The new design doubled the building's available floor space and, in turn, the number of people it can accommodate, from 4,500 to 9,000....

....The ambitious project, which 3XN completed alongside engineering firm Arup and Australian architecture practice BVN, posed a slew of design challenges. Among the first was simply determining whether the existing building matched its original design.
High-rises often shrink under their own weight, especially in the first few months after completion. As a result, the old AMP Centre "was at a slightly different level than was on the drawings," said Holt, explaining that concrete "spreads and drops" as it fully dries....

....To counter this, engineers installed hundreds of sensors around the building to track even the tiniest movements. This data fed into what Holt described as a "digital twin" — a dynamic computer model of the tower — that was used to make real-time adjustments and ensure that "everything worked, shifted and shortened the way it was supposed to."

Workers also left a gap of 4 meters (13 feet) between the new and old structures until the very last stages of construction, giving the new concrete time to settle before the final "graft" was carried out....

https://www.cnn.com/style/article/australia-quay-quarter-tower-skyscraper/index.html