Fast-Tracked Failure: The Hyatt Regency Walkway Collapse

I've been watching videos from Brick Immortar of late and will have another one from the same channel next week, but I could pick probably any of these videos and post them here. They all seem to analyze famous engineering failures, quickly recap the incident, then summarize the causes of the failure.

This one is one I'd heard about and that I've seen discussed as a famous case of plans being adjusted without proper checking to see if that seemingly minor change would be problematic. This is, however, the first video on the incident that I've seen discuss that the original design would have been problematic over time as well.

Micro Tensile Strength Test of Plastic per ASTM D638

I always like to open these posts with a joke or pun of some sort, but I couldn't come up with one for this video that wouldn't be a stretch, so I'll just get cracking.

The inherent simplicity of a tensile test - just stretch a material specimen - belies the actual complexity present in performing one carefully and repeatably. 

Today's video shows the care that must be taken to perform a tensile test according to industry standards - ASTM D638, in this case - and the stress/strain curve that results from a properly conducted test.

In case you were curious what this whole "ASTM" standard was about, check out this video about the ASTM organization.

How Weed Eaters Work (at 62,000 FRAMES PER SECOND) - Smarter Every Day 236

I've spoken of my love of Destin before. One of the things that I love most about him is his scientific curiosity. He's willing to point a slow-mo camera at just about anything and set up some experiments to teach himself more about whatever that camera points at. It's kind of awesome.

In this one, Destin points his Phantom high-speed at weed eater string to see how the string cuts blades of glass (cut or rip? delaminate or clean slice?) and breaks against various wire fencing materials.

We could do a lot worse than show this when talking about destructive testing in class.

There's also a second video that tries to figure out which shape or string is best. He comes to a conclusion, but I'm not sure he does nearly enough experimenting and variable isolation to actually justify the conclusion he comes to.

Mui Ho Fine Arts Library

At first glance, there's not much thrilling about the library - the Mui Ho Fine Arts Library - in the video above.

There are a bunch of bookshelves in open stacks three stories high.  All in all, meh. That's been done before - and much higher, honestly.

But then you get to the moment in the above video - about 0:55 in - where they mention that the books and the floors and shelves supporting them are NOT actually supported by the floor below but rather are hung from the ceiling.

Tension...not compression.

How cool is that?

I mean, as long as you aren't wearing a skirt, a dress, or high heels, anyway.

Tensile test

Computer modeling is so cool.

Like in this tensile test, you can see that the force concentrates as the cross sectional area of the sample decreases, leading to more and more drastic necking.

I can't see that when I look at a real sample being tested, but with the rainbow coloration for the different amounts of force, I can kind of show that to my students.

MaterialsScience2000

I love seeing the crystal grains develop as the acid etches the metal surface. It's just gorgeous.

The eight-and-a-half-minute video above shows the preparation of a few different samples, some of which show crystals large enough to be seen by the human eye as well as a few samples that have been etched through natural processes over time.

MaterialsScience2000 has ten total videos posted, and many of them are worth a watch, including a thorough explanation of the tests being preformed. Check out these, too...

A36 Steel Tensile Test

At about eight seconds in, I can start to see the necking which causes the force to concentrate on that area which causes further necking which causes force concentration...back and forth until catastrophic failure nearly at the end of the video.

Not much else to say here but that it's a nice video of a tensile test being performed. I just wish we could get a concurrent graph of the stress/strain curve being generated.

Here's another tensile test from a bit further away...

Concrete Countertops: How reinforcing works

Concrete is great under compression but not nearly as good under tension.

A concrete beam would make a lousy support for hanging structures.

Here the president of the Concrete Countertop Institute (really? is there an industry group for every possible subindustry?) uses a Simpsons still to help us understand the issues that exist with a concrete 'beam' like a countertop.

He then brings out a great illustration (at 2:30) of the tension/compression forces that occur on a beam when the beam bends and goes on to explain where the different tension issues occur when a beam is supported on the ends or cantilevered away from the support.

The video is a little long (nearly 10:00 in total length) but does a very good job explaining how and why reinforcement measures have to be used in concrete countertops.

If only it came with a great medallion like this one.

By the way, is that guy to the right in the picture the same one speaking throughout the video?