A primer on the strength of materials - Metals

The cases we've looked at so far have been clear cut cases of a structural element being overloaded. Before I go on to other cases we need to understand what is happening when a structural element is overloaded. What is happening when something is overloaded? Logically if something is overloaded we need a bigger beam or something, but we also need to consider what the beam is made out of and how strong that is.

The strength of any structural element is related to:

1. Its geometry/shape
2. The material it is made out of.
3. External factors such as bracing.

1 and 3 we will go over another time, the geometry of structural beams is a complex subject in of itself. In virtually all structures today the primary structural elements are steel, wood, masonry and concrete or some combination thereof. This post will look at steel and metals in general.

Hyatt Regency Walkway Collapse

http://en.wikipedia.org/wiki/Hyatt_Regency_walkway_collapse

Here we have a walkway suspended from the ceiling and two connection details. Both of them are bad for different reasons. However one of them theoretically works, and the other killed 111 people. Which is the one that killed over a hundred people and left over 200 injured?

Versaille Wedding Hall disaster

This is a public blog posting of a structural engineering discussion thread on a forum I post on. I figured that since I was spending the time to write up these pieces that I may as well post them outside that insular forum and make these educational posts public.

This post will be about the Versaille wedding hall disaster if you hadn't guessed already.
http://en.wikipedia.org/wiki/Versailles_wedding_hall_disaster

This structural collapse is also notable for being caught on camcorder:

The wiki explains it quite well, but this case is notable because it could have easily been avoided. One should note that structural failures often occur because many things fail, and it is often ignorance which leads to catastrophe. Although the building in this case was not correctly built/designed, it still would not have failed if there were not even further errors down the line. This is fairly typical of massive structural failures - it is often a combination of many things going wrong that cause a structure to fail, and even an incorrectly constructed building is far tougher than most will give it credit for (but not always).


So what went wrong?