Back in 2012 I wrote about China's Broad Group, which had just built the core structure of a 30-floor hotel in 15 days. Its pioneering methods of constructing tall buildings were attracting a lot of interest.
The group has now erected a 57-story skyscraper in just 19 days. Here's a time-lapse video of the construction.
The BBC has an in-depth report on the project, and the group's plans to build a 220-floor structure - taller than the tallest building currently in existence - in just seven months: four for the foundations, three for the tower itself. Here's an excerpt.
Zhang travelled to Germany, Japan and the US to meet expert engineers, and all of them talked about steel. Steel structures were strongest, but also flexible enough to bend, not break, during a tremor.
The problem was cost - steel was prohibitively expensive for normal buildings.
So Zhang Yue's idea was to make a new, cheaper form of steel structure.
He set up a new wing of his company, called Broad Sustainable Building (BSB), and set to work with a team of architects and engineers.
In 2010 they made their first public prototype - a six-storey building built in a single day for the Shanghai Expo. Since then they've completed more than 30 buildings, including a 15-storey hotel in six days, a 30-storey hotel in 15 days, and the recent Mini Sky City.
The process is always the same.
Steel is delivered to one of Broad Group's six huge hangar-like factories, where it is machine-cut and welded into one of a few basic modules - a column, crossbeam or floor section.
These are then loaded on to lorries and driven to the site, where they are slotted into place like Tetris pieces, and finally bolted and welded together.
All modules bear serial numbers. The more advanced ones, like the 12m x 2m rectangular floor sections, come pre-installed with plumbing, electric wiring and air ducts.
The company says 90% of their buildings' components are prefabricated like this, with only interior finishing required on site.
A “configuration guide” on the company’s website allows prospective clients to select the type of building they require, from hotel to kindergarten to museum.
They can also choose extras, such as a “sky garden”, an “indoor farm” or a helipad.
To demonstrate resilience of the buildings, footage has been released of a model skyscraper surviving the equivalent of a magnitude nine earthquake.
In heavily polluted China, one of the most appealing features of the design may be the interior air quality.
High levels of tiny atmospheric particles called PM2.5 pose a serious health hazard in many cities - at one 20th the diameter of a human hair, they're small enough to lodge in the lungs and enter the bloodstream. Broad Group claims their technology stops 99% of them from getting inside their buildings.
The windows are designed not to open, partly for this reason. They're also made of quadruple-paned glass, one of the features which Zhang says makes his buildings “five times more energy efficient” than conventional ones.
There's much more at the link. Very interesting reading.