Building a strong structure bridge. bridge engineers please!?
the bridge is to withstand loads. i know that u will tell me to build a bow truss with the zig zag. well i know that. but wat i am worried about is the joints. what kind of connection should i use? i tot that glue gun would be good. any suggestions? the point of the load is going to be directly in the middle. its a rectangular load placed across the truss.
btw, satay sticks are really very weak. i dunno if the truss design would work ornot. maybe another unique design? please help. its a school project.
Answer:
Hot melt glue is flexible. I would suggest epoxy for a very rigid joint.
I think the point of the exercise is to show how unbelievably strong trusses are using what appears to be "weak" materials.
A triangle is used because it has this unique property: it is the only shape that can't distort unless one of its sides changes sizes (i.e., distorts).
A satay stick is amazingly strong in compression or tension along its length. It is easy to snap it from the side. But set it on end and push *straight* down on the end pointing up (without jabbing it through your hand!) and you'll see that it will "hold" a lot of weight.
This is the key to your truss and the use of the triangle. The truss pushes or pulls along the length of the stick -- where it is strongest, and the triangle won't distort unless the stick deforms -- in its strongest directions.
So you are taking advantage of these two things simultaneously to make a strong structure.
There are lots of kinds of trusses, and I'd look at the links below to see what would be best for you given the "test" that your bridge will be subjected.
The first link is from a kid who made a truss out of balsa wood that held a 30 kg. (66 lb.) weight. Other kids had to make projects out of drinking straws instead of sticks.
try researching arch bridges.
i assume the satay stick can bend.
laminate stick on top of each other and use vertical members to hold the roadway up.
use cross members to stablize the bridge only. i used balsa wood (very soft wood) with this design and it held 8kg.
hope it helps
use wood glue and build up the sections...
brace the failure modes
the built up beams works great!
the one my son built held the required 150 pounds PLUS
the teacher for over 340 pounds
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