The serious accident of a screen falling during the MIRROR concert drew much attention from the general public. On the evening of August 1, the government released a photo inside the coliseum saying that from initial evidence, one of the steel cables connecting the screen was found to have snapped open.
Combining the photo and other information, people start to speculate that one of the steel cables linking the screen might have first become loose, leading to the other cables not being able to take the extra load, which eventually broke and caused the screen to fall. But at the moment it is still not able to confirm why the cable became loosened in the first place.
The government set up a task force to investigate the cause of the accident. On the evening of August 2, the group released the first photos after its inspection at the Hong Kong Coliseum.
It can be seen that there are black electric wires and a broken silver steel cable on one side of the screen, and the cable and screen are connected by eyebolts. However, it is a pity the status on the other side of the fallen screen cannot be seen. Anyway, there is still a silver cable hanging above the stage.
It is suspected to be the steel cable that was originally connected to the other side of the screen. There was a ring-like component with a linking screw.
It is noted that the black wires are used for power supply and signal transmission, while the steel cables are used for supporting the load. It can be seen from the pictures of the scene that the screens still hanging overhead now are connected by two black wires and two steel cables.
It is suspected that at the time of the accident the lifting eyebolt on one steel cable became loose, and the steel wire rope on the other side failed due to the increased loading, resulting in the accident.
Ngai Hok-yan, a registered structural engineer, said in an interview with the media that as the screw trunk could not be seen from the picture, it was suspected that the screw became loose, causing the screen to tilt to one side. And when the other steel cable could not take up the increased load, it snapped open leading to the fall of the screen.
He went on to point out that the screw body is usually inserted with a “safety pin” to prevent it from coming loose or fixed by welding. Either method is not complicated at all. If there is an accident due to this, he would describe it as a “low-level mistake.”
He said that the components might have come loose at a high level. For example, the screw cap might have become loose, causing the screw body to separate from the steel frame of the screen; another possibility is that the opening in the steel frame may be too large, and the screw might have just pulled out.
Another report quoted some backstage supporting staff of the concert saying that the screens were made to move up and down and also rotate, to create some real-time visual effect. There had been certain modifications to all such routine movements during the concert. These new requirements, no doubt, would impart much more stress on the whole cable structure, compared with suspension of the device at rest.
The investigation continues.