[Alberta's Child]

It's a bit more complicated than that. There are different safety factors for dead load (the weight of the structure itself), live loads (the occupants), and environmental loads (wind, snow, earthquakes, etc.). And these safety factors vary for buildings and bridges, too.

Very few applications in civil engineering would use a safety factor of 5. In fact, structures tend to have lower safety factors than many other applications like mechanical systems, aircraft, etc. because the loads tend to be very predictable.

[Will88]

If you haven’t come across the posts yet, a witness said that something fell from a crane and that caused the collapse. And other reports that the crew was conducting stress tests when it collapsed.

Nothing confirmed yet, AFAIK.