How do engineers demolish a skyscraper?
First, the building is stripped as much as possible, removing copper wire and aluminium for recycling, as well as all the windows and insulation to prevent health-and-safety hazards from flying debris. Then explosives are used to shatter the load-bearing structures on some of the floors. The explosives are synchronised using detonating cord – a thin plastic pipe filled with an explosive called pentaerythritol tetranitrate, which burns at four miles per second. The aim is for the upper storeys to fall vertically down so that the whole building collapses onto its own footprint and surrounding buildings aren’t damaged.