Re: Bridge Design

I would include with these comments the following remarks:

Try to get as much "air" into the structure as possible, and try to by
this means minimize materials-or-construction. The ratio of load/weight-
-of-structure is critical to success. High load and low weight is what is
most desirable. [I hope your instructor know this!] Finally, examine by
trial-and-error observations exactly how tensions and compressions are
configured under loading. This PROCESS should get you to the best PRODUCT.

- - The original note follows - -

From: [email protected] (Michael Rubin)
Subject: Re: Bridge Design
Date: 12 Jan 1994 20:30:41 -0500

In <[email protected]> [email protected] (Jeff Pearson) writes:

>Newsgroups: alt.architecture
>Subject: Bridge-like structure


> I am currently trying to design a bridge-like structure. I need
>some ideas for a structure that will span approximately 24" and be 2"
>wide. I will be able to use 5 pieces of veneer, white glue, wood glue,
>fiberglass cloth, resin, and epoxy. The veneer is approximately
>1/8"X2"X24". I had an idea to make triangular pockets sandwiched
>between two pieces of veneer and filling those pockets with fiberglass
>cloth and resin. Any other ideas would be a great help. Thanks in

>Jeff Pearson
>[email protected]

Sounds like you're trying to get the Net to help with your homework,
but in the interests of nothing in particular...

You could make a triangular-section beam of 3 pieces of veneer (compression
members) wrapped in fiberglass/resin (tension member). Would require some
thinking and/or experimentation on which direction to lay the fiberglass
and what to do with the other 2 pieces of veneer.

You could make an I-beam with one piece of veneer for the web and two each
for the top and bottom, if you can think of a way to keep the parts together.

You could make 2 of the triangular pockets you suggest, lean them against
each other top-to-top, and put the fifth piece of veneer horizontally as
the bridge deck: /|\
// \\
// \\
// \\
The bottom joints will be under a lot of tension & so must be well glued
& wrapped with fiberglass.

A design parameter to think about: are you allowed to use the objects
the bridge will be sitting on for horizontal as well as vertical
support? If you will be testing on (say) two desks 2 feet apart, your
bridge can be an inverted-V with no bottom chord if the ends are notched
to rest between the ends of the desks.
--Mike Rubin <[email protected]>
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