Sunday, March 24, 2013

Steel Bridges -- the weird way

I am working on two things at the moment. One is a coastal wave model that often makes me feel like a blind astronomer. When it works, it is wonderful, but when it doesn't I spend weeks poking around trying to figure out why it is hiccupping. Akin to sticking your hand in a black box of spagetti, trying to ferret out the one strand of angel hair pasta.

The other is something I do in my spare time, when it exists. It has absolutely nothing to do with waves and fluid mechanics, so I don't think it will be featured in this blog just yet. I need to be more comfortable with my progress on it, anyway.

However, seeing as it is pasta-black-box time in my research once again, I think I will take this opportunity to write about something else completely unrelated to coastal research--a finished project I constructed in my senior year.

I built a steel-chain compression walking bridge.

It was one of those school projects which could have been made to meet spec with some 2x4's and a couple of screws, easy. But my senior design class was all about making things harder for no good reason.

So, yes, we could have made an arch bridge out of wood. And it would have worked just fine, spanning 10 feet and being over 3 ft off the ground with ease. But why do that when you can do something completely crazy, and build an arch bridge out of traditional tension elements?

Because learning to weld. And making crazy mechanisms to avoid as many calculations as possible.

In short, because fun.

Prototyping. With paperclips.

Basically, the original idea was to hang the chain and weld it into place, capturing a natural and perfect arch shape.

Compression testing for different link sizes.

Turns out hanging over ten feet of chain in the lab and leaving it until we felt like welding was not going to be an option. So we decided to weld individual segments straight and then piece them together. 

Our janky weld set-up. But, hey, behind the appropriate screen!

Partly welded chain, partly not. We left one link free for each straight segment, so we could...

Hang the chain length between a ladder and a doorframe and weld each joint together? Not planned at the last minute. Nope.

Securing the ladder. Steel chain is heavy, man.

This actually was not overkill. By a long shot.

At some point we had to deal with the deck. Unlike the chain arch, this took all of two hours. I am really comfortable working with wood thanks to non-academic projects in undergrad.

The two completed arches! Now to put everything together...

We needed to support the endload somehow. So we were lazy -- well, mainly pressed for time -- an basically tacked on some 4x4's on the ends

Which made the arch structure completely useless. See? I said at the beginning that the design specs could be met with nothing more than some wood and screws. 

Having proved that to ourselves, we decided we might as well be all in or nothing. So we went back to weld eight more compressive elements for the ends of the bridge and to brace the joints of each arch.It meant several more hours in lab, and lots of time readjusting the design and angles of every new element, but it was worth it.

Testing day. We definitely had the easiest set-up. Just planted the thing on the ground.

Loading the bridge with concrete blocks. The goal was 2000 lbs without failure.

 And, almost passed the 2000 lb distributed load test with ease. Less than an 1/8'' deflection. Barely measurable.

Also, as it turns out, holds five point loads quite nicely. 

I think the bridge is currently the desk of some civil engineering professor. Rather fitting.

The bridge testing day was by far one of the best days my senior year. Building something is an accomplishment. I realized that day that all of the hard work, backtracking, and flexibility needed to complete a project well was worth the trouble. You cannot schedule everything ahead of time, for certain (as much as I would like to pretend otherwise).

Also, I realize that mechanical engineering majors must have all of the fun all of the time, if they get to build things their entire undergraduate career. I take small satisfaction in the thought that they will not be building bridges, though--and certainly not ones that have no business existing.

Thursday, March 14, 2013

Yup, I'm still alive

If anyone has been reading this, you may have noticed that I stopped updating early last semester (I'm a grad student, I think in terms of academic years).

This is not by accident. Semesters eat my life, just in general. It is difficult to justify doing "frivolous" things that my advisor or professors will never see. Heck, I'm still shocked /you/ are reading this.

However, that is no excuse for my failure to update during winter break, or even before classes in January. So, the way I see it, you are owed at least two more entries to this thing before summer begins.

Before I officially begin either of those entries, however, I wanted to explain the real reason I have not been keeping up with this blog, especially during the winter. Last semester, a lot of things changed for me. I stayed in roughly the same geographic location, but I became a new kind of student with different responsibilities and a wildly different living situation.

My world basically flipped upside down without my approval. Adjusting takes time, and doing good work while adjusting is completely possible (especially if you are as stubborn as I am), but takes a nontrivial amount of effort. Occasionally this means ignoring things. Occasionally it means sacrificing things. But it had to happen, and I am hopefully close to righting my world (or reorienting what I consider to be "up"...metaphorical gravity is a funny thing).

Additionally, I realized that I did not feel like chronicaling old projects in detail on this thing. It is a good exercise, sure, but that's why I have a lab notebook. I find it dull, and I can only imagine how a reader feels about it.

Therefore, I plan to revive this blog during the spring semester in a tentatively new direction. Excrutiatingly detailed projects, written like a science paper, just won't cut it anymore. Instead, I have a couple of new topics I hope to get in written form in the near future--/concise/ written form, mind you.

The candidates are:

- welded chain steel bridge (chain as a compressive element! The one project my senior year I felt proud of)

- how to choose an advisor (part II! With nuts!)

- waxing eloquently about the oceans (I gave two talks last semester about this, and only further realized my passion for keeping our world in some semblance of working order)

- Teaching (fluid mechanics, what else? I have ducklings now!)

- Grad projects (?? Let us be honest, I have no idea how much of what I currently do can be published casually in a blog. Name of the game in science).

So. Hold me to at least two of the above topics and I will consider myself to have made up for December and January.

In the meantime. Things change. Hence the title of this blog ("fluid" archive. Get it? Get it? Poke.) I'll try to keep this at least moderately active depsite all of the craziness of real life.