engineering

A building suddenly collapsing after a 7.1 earthquake strikes Mexico City. - can someone explain why there is no resistance as it came down.

A building suddenly collapsing after a 7.1 earthquake strikes Mexico City. - can someone explain ...
https://www.youtube.com/watch?v=MaMYaje7-pM

It would appear to be made of brick, which performs poorly in earthquakes if not reinforced.

Example:

See the swaying? Because it's fixed to the ground, one side is put in tension and the other sees more compression than normal, then the building leans the other way and the side with the tension load switches. Masonry/brick buildings do very poorly in tension, brick and mortar has several thousand psi of capacity in compression but only a few hundred in tension.

Best guess (based on the video and common earthquake failure modes for that kind of structure) is the tension loading caused a column to be damaged, then when the building leaned the other way, more load than normal was applied to the damaged column. The column failed and the building underwent disproportionate collapse (that's the rapid collapse you saw).

Collapsing at or near free fall speeds isn't unusual when brittle failure occurs (a common mode of failure for rigid structures like masonry) because the failure is abrupt and the loads it supported are allowed to fall. Building support systems are designed to resist the load of a building at rest. Once all that weight starts to move quickly the remaining support system doesn't have the capacity to slow it down so the failure dominos and the whole structure rapidly collapses.

You prevent this by designing for ductile failure, so more energy is absorbed by deforming the structure and making it clear to the occupants that the building is compromised and they should evacuate. You can reduce the likelihood of brittle failure by using steel to carry tension loads, reduce overall loads using base isolation or avoiding masonry (brittle material) altogether in earthquake prone regions (timber, steel and reinforced concrete have better performance than brick).

Edit~ Clarified disproportionate collapse. I tried to avoid jargon and ended up inserting it in the end with no explanation.

It's still shaking; you can see perturbations in the puddles on the ground.

Stabilise the building? I think it’s a little too late for that.

Colorado State Student Performing Structural Integrity Test (X-Post r/whitepeoplegifs)

I gotta think him landing off center playing a big part here. Landing right above the support definitely helped keep the table up, but still that's amazing it held.

But let's take a moment to thank the plastic retaining its shape. Had it broken, the metal upright could do some damage.

Trying to break metal at it's strongest most stable point. Murica

I know "Rule 6) No low-effort posts. This includes jokes, puns, etc." Technically the title is correct though.

Seriously the first thing that came to my mind when I saw this was "The engineer who designed this table (able to sustain a ~150lbs(?) weight dropped from 3 stories up and remain perfectly intact) built this thing like a rock"

Besides, I didn't know where else on Reddit to go for engineering humor.

Source: https://www.reddit.com/sub/whitepeoplegifs/comments/701q9p/hold_on_guys_ill_be_right_down/?ref=sh...

Original Source:

I make no claim to it being original content from me.

X-Post'd to /sub/therewasanattempt and /sub/idiotsfightingthings because it fit those subs as well

Sourced to: https://www.reddit.com/sub/therewasanattempt/comments/704pox/to_jump_from_3_stories_up_and_break_...

https://www.reddit.com/sub/IdiotsFightingThings/comments/709dio/man_vs_folding_table_xpost_rwhite...

Edit1: Grammar

this gear box

this gear box

Although the concept is really interesting, the video is awful... music volume way too high, voice volume way too low and also voice too monotonous and droning to listen to...

why this isn't efficient or feasible though.

Absolute pain in the ass to manufacture.

Maybe. But there are still some unwritten minimum standards that this video does not live up to...

Thats really cool actually. I wonder if someone after me with more knowledge on this topic will pop in and give reasons why this isn't efficient or feasible though. Hope not lol, because I would love to do away with the regular old gear and chain on any of my bikes.

What an engineer gets his son when he graduates from undergraduate <3

What an engineer gets his son when he graduates from undergraduate <3

Oh we're not supposed to steal them from work?

Just remember to bring them back for calibration every year.

My wife forgot about calibration day while she was out of the country for a work trip, I had to dig through the shed to find the right pair of calipers and then drive them to her work so nobody would get in trouble for having an uncalibrated caliper on hand. I had no idea it was that serious.

Oh, an engineer's C-clamp!

Paper robotics

What type of witchcraft is this!

Don't spread bad information, they are small robots on wheels. They just do a few simple behaviors.

Stop motion animation?

This is really cool. Anywhere I can read about this?

Acrobot (xpost r/interestingasfuck)

The way the robot grabbed the bar again was very impressive and caught me off guard. Well done!

|10| |9| |10| \O/ \O/ \O/ | | | /\ /\ /\

Thanks.

Are you the robot?

This is a mercury vapor rectifier. It turns two or three phase alternating current (AC) into direct current (DC) (xpost r/interestingasfuck)

and now all you need is a chip that you can hold in the palm of your hands, thank goodness for engineers!

It operates on the difference in electron work function between two materials. In this case mercury, which has a very low work function, and carbon/graphite which has a very high work function. So it's easier for electrons to exit the puddle of mercury than to exit the graphite electrodes. Hence it works like a check valve.

The operating principle of semiconductors also operations on difference in excitation energies. However the check valve function in semiconductor diodes is mostly provided by the increase of width of the p-n depletion region when a reverse bias voltage is applied.

But what have we lost? Our grand fathers practiced mad science in rooms full of glowing vials, bubbling concoctions, arcing tesla coils - now where are we? It's just a guy sitting in front of a computer.

Or, now hear me out, 4 diodes and a capacitor :P

My Rubik's Cube Robot executing a solution in 0.76 seconds.

The robot doesn't yet have image recognition so I am using hardcoded solutions. This particular scramble and solution is identical to the one used by the current world record holder (0.637 seconds) and I am using it as a benchmark for testing the stability of the robot and seeing how I compare to the best.

94-year-old Lithium-Ion Battery Inventor Introduces Solid State Battery

94-year-old Lithium-Ion Battery Inventor Introduces Solid State Battery
94-year-old Lithium-Ion Battery Inventor Introduces Solid State Battery

So this potentially allows for smaller batteries of similar range in cars, or similarly sized batteries with 3 times the energy density. That means range could be improved by a factor of a little less than 3. Imagine an electric car went 700-800 miles per charge, and charged fully in a couple of minutes. That would solve the range anxiety problem with electric cars.

6 years & $16 Billion Dollars later, the Hebron Platform is in final stages of construction.

6 years & $16 Billion Dollars later, the Hebron Platform is in final stages of construction.

ITT: People thinking they have a shred of inclination of whether this is going to be profitable or not. I assure you, they've done the math and they think they'll make money, and they know way more than any of us about the specifics.

Try one of these subthreads