Design a Bridge: Win a scholarship to Westpoint

Raxmei · Post by **Raxmei** » 2003-01-21 08:35pm

Red Knight wrote:Ive got mine down to 151,827.13. Its using all carbon tubes, and I dont think I can get it much cheaper.

Try replacing the glowing blue parts with thinner solid bars. Tube is more expensive but no stronger than bar for equivalent mass in tension.

I've gotten down to $140k.

Post by **Beowulf** » 2003-01-21 11:24pm

Anybody able to beat my score?

The Dark · Post by **The Dark** » 2003-01-21 11:26pm

Raxmei wrote:
Red Knight wrote:Ive got mine down to 151,827.13. Its using all carbon tubes, and I dont think I can get it much cheaper.
Try replacing the glowing blue parts with thinner solid bars. Tube is more expensive but no stronger than bar for equivalent mass in tension.

I've gotten down to $140k.

Hmmm...I found the tubes to be cheaper than the bars if it was just tension. Bars were better for stress (red).

Exonerate · Post by **Exonerate** » 2003-01-22 12:16am

Beowulf wrote:Anybody able to beat my score?

I will when I get the time...

Red Knight · Post by **Red Knight** » 2003-01-22 01:22am

A tip: if you go lower than 100mm for tubes, it gets more expensive for some reason.

Ive got it to 148,322.84 using a railroad truss type bridge. Prety sturdy too.

RedImperator · Post by **RedImperator** » 2003-01-22 10:07am

I suspect $124 is getting close to the bottom. Even the very cheapest site layout (24 meters high, standard truss abutments) costs around $80,000, and that design has to be so long that it winds up more expensive than some arches with a shorter span (and greater excavating and abutment costs in the beginning).

My guess is that the cheapest possible design is an arch. I can get away with only two solid members in the entire design (all carbon steel) with an arch, while every truss design I've tried has needed almost all the deck support members to be solid.

Exonerate · Post by **Exonerate** » 2003-01-22 08:32pm

Hmm... Well, I've gotten 1 126k. The best way seems to be distributing all the weigh as equally as possible.

Exonerate · Post by **Exonerate** » 2003-01-22 09:07pm

WOOT! $125,662.52

Post by **Beowulf** » 2003-01-22 09:27pm

$123,900.62

I think that's pretty close to the lowest possible.

It's using the 20m high, 4m arch supports. It has:
4 180mm tubes
8 170mm tubes
4 140mm tubes
4 130mm tubes
14 110mm tubes
4 30mm tubes
and 5 45mm bars

23 joints

all carbon steel

bridge weight: 4231.4 kg

Exonerate · Post by **Exonerate** » 2003-01-22 10:12pm

Beowulf, submit that. I submitted my 125k one, and got like in the top tenth percentile... I'm willing to bet you will get a lot higher

Post by **Beowulf** » 2003-01-22 11:26pm

#17 out of 210... need to get a better bridge...

Exonerate · Post by **Exonerate** » 2003-01-22 11:28pm

Whoa... You're like 40 places ahead of me

Post by **Beowulf** » 2003-01-23 09:28pm

Try harder then...

aerius · Post by **aerius** » 2003-01-23 10:34pm

I've gotten down to $135k with an all tube arch design. It took me the longest time to get something under $160k until I realized the joys of tubes.

Exonerate · Post by **Exonerate** » 2003-01-23 10:40pm

Gah, currently, my design is the cheapest possible with the current configuration... Must find a new design...

Post by **Beowulf** » 2003-01-23 11:25pm

aerius wrote:I've gotten down to $135k with an all tube arch design. It took me the longest time to get something under $160k until I realized the joys of tubes.

you know, in some places bars are cheaper than tubes. When it's under tension, use bars, under compression, use tubes.

The Dark · Post by **The Dark** » 2003-01-23 11:26pm

Beowulf wrote:
aerius wrote:I've gotten down to $135k with an all tube arch design. It took me the longest time to get something under $160k until I realized the joys of tubes.
you know, in some places bars are cheaper than tubes. When it's under tension, use bars, under compression, use tubes.

I thought it was the other way around...merde, no wonder I haven't been doing that good!

ArmorPierce · Post by **ArmorPierce** » 2003-01-23 11:30pm

Got mines to 143k, after that weird stuff started happening.