Designing a Beam for Materials Class Project

[Cyrus]

I have to design a beam for my Materials Class design project to be tested on a univ. bending machine. We have to be within 2.5" by 5" in max size, and 24" long. I wrote a MATLAB prog to calculate every possible configuration to optimize what sizes to pick for a block, a T beam and an I beam, but I am having trouble calculating Q for certain members to see what type of nail spacing I need. Here is a Pic of what I am not sure. What would be my effective area, for the horizontal members? Would it be everything above where the nail is, would it be from that nail to the next nail directly above it? I am thinking its everything above but my book is horrible in explaining it. The red are nails. So, for example, what is the Q for each of the verticle boards? Likewise, what about the horizontal ones? The top board is simple, but any board below it is a problem. Thanks!

 

[Cyrus]

I found out the anwser, if anyone cares. The nail spacing for the web can be any value, becuse there is no shear along the length of the board trying to rip the boards appart along the length. The only nails under shear are the ones in place vertically, due to comp. of shear. Neat. I got all the dimensions and am going to make my T beam this sunday. Turns out a T beam deisgn is nearly as efficient as an I beam. The only difference in cross sectional area is .004 inches square, and the T is a lot easier to construct. Yay for matlab, that code really saved me tons of work and time figuring out a beam design based on the size constraints. We will test the beams out on friday. If anyone cares, Ill post how well we did. It has to support 3kip before breaking or we fail.

 

[Danger]

Good for you, getting it figured out. I'm sorry I couldn't help you any, but it's totally out of my realm.

 

[Cyrus]

Ok, so I got a friend at work to run a finite element analysis on my beam and come up with a deflection picture for my technical report. ITS AWESOME! Anyways, here it is! Even the computer agrees that my beam should work, in theory at least! ;-) . We break the beams tommorow, provided that it does not snow.
https://www.physicsforums.com/attachments/5800

I will be lighting a candel to the beam gods tonight! Please do the same! ;-)

 

[Danger]

Congrats. That's a cool picture. Hope it works as planned.

 

[Cyrus]

Here is the beam a team mate made using autocad, SWEEETTTT!https://www.physicsforums.com/attachments/5804

You can see its a 4 piece design. A top cap to build up the web, two side members to make up the web, and a one piece flange at the bottom.

This beam looks photoreal, I am sitting here in awe...

 

[Cyrus]

Success!

So we broke our beams today. Every materials class in the school did the test today. I’m happy to report that my beam was the BEST! We built two of them, one a backup. The point was to have the beam fail as close to 3kip as possible but not under. Our beam failed at 3390 and weight 1.7lbs. The second backup beam held an impressive 4850 lbs! The machines limit was 5000lbs! The only group that also went that high made a massive mammoth of a block weighing in at 2x our weight. Brains over brawns...my MATLAB code worked to give us that weigth/stregth ratio edge. Most other groups failed UNDER 3000llbs, by most, I mean like 90%. Sad, oh well their loss is my A+.

Now I have to do the analysis write up, I'll post that up here once its compeleted if anyone cares to read it.

 

[Pyrrhus]

Nice work! cyrusabdollahi!, i found this interesting. Keep us updated.

 

[Danger]

Good on ya, mate. It definitely pays to think things through.

 

[Cyrus]

Thanks guys!

 

[Cyrus]

Ok, the paper is done. Its kinda long, ~20 pages of text and another 16 pages of MATLAB code. Ill figure a way to zip it so it will let me upload it. If not ill put it on a site and provide the link, if anyones interested. Please be brutally honest in what you think of it.

 

[Cyrus]

I got it loaded up on my website. Check it out! Tell me what you think! I think its pretty good! I still have to put the MATLAB code up though.
http://www.angelfire.com/realm3/cyrusabdollahi/ES220.htm
Click on the link, then keep hitting cancel when it asks you for password and it should show up. If u think it stinks, let me know too! Its a big file, so let it load for a bit. It was a group project, group meaning I did all the work...heheehe. I had too much fun to let anyone do anything.

 

[Pyrrhus]

I saw it fast, but the work it's presented decently. I'll let you know later on what i think of the content. Nice pics!

 

[Pyrrhus]

Cyrus, i read the report. I think it's very good, but with a nicer format and less theoretical information, it'll be better. Afterall, you are designing beams which data is for engineers to read, supposedly we know what the centroid and moment of inertia is, but still good. Nice work.