I have to build a popsicle bridge for school. It will be tested by hanging a hook with a bucket and filling the bucket with bricks or some other weight. I was wondering if a truss box kinda shaped or an arch would be stronger. Please let me know ASAP.
2007-01-29 14:53:59 · 4 answers · asked by i_need_answers 1 in Science & Mathematics ➔ Engineering
I would recommend a truss, probably a bow truss. There are a couple of things to know about trusses. First is that since bridges SPAN something, and the weight will be placed in the middle, the truss will want to deflect down in the middle, this is called bending. A phenomena called moment is the force that produces bending. The maximum moment is in the middle of the truss.
The bending moment is resisted by the truss with the top chord and bottom chord. The bottom chord is usually straight and is a TENSION member. The top chord will depart immediately from the bottom chord to a maximum distance (in the middle) away from the bottom chord then come back to meet it at the other end.
This is the key. The further the top and bottom chords are away from each other the more moment they can resist.
The diagonals are used to resist the other force, shear, which is zero in the middle, but maximum at the ends.
I would use double sticks for your chords and sandwhich the single diagonals in between.
Look up a bow truss for a model. Do a bit of study on trusses. They are facinating structures.
2007-01-30 11:27:48 · answer #1 · answered by daedgewood 4 · 0⤊ 0⤋
Curved shapes are pretty strong as they distribute weight, but triangular shapes are very strong too. What about an arch made of triangles? Look at different bridges and the history of bridges and see which kind has been around, or lasted longer. I think I'd go with an arch bridge. Look how many of the arch bridges and other arch shaped constructions the Romans made which are still standing.
2007-01-29 15:18:18 · answer #2 · answered by Anonymous · 0⤊ 0⤋
I would elect truss design for the simple fact that trusses are better to resist point loads (loads at nodes) while arches are better for distributed loads.
The best possible scenario, is to try to keep as many members in tension, because (a) glue and wood is very strong in tension, (b) long slender members have a tendancy to buckle.
Look up a Pratt Truss for ideas, or check this place out.
http://pghbridges.com/basics.htm
2007-01-29 17:10:21 · answer #3 · answered by Daniel W 3 · 0⤊ 0⤋
of course it depends on the rules... but i have found the simplest designs win these contests most often.
2007-01-29 16:35:30 · answer #4 · answered by Jesters Deadd 2 · 0⤊ 0⤋