are balsa wood towers stronger than balsa wood bridges?

Answer 1

I think that depends on how they were designed and what criteria you use to determine "stronger".

Answer 2

I am not familiar with the designs you mention but you could try searching for photos of railroad bridges. A great many RR bridges were steel truss designs. In general, you want to look at the areas of highest stresses, both high tensile and high compressive stresses. Balsa wood (like most materials) are stronger in compression than in tension, so, for the same level of load, the compressive members can be smaller cross section than the tensile members. Keep in mind that, in compression, you have to worry about buckling. Also consider areas of stress concentrations, specifically, joints. Inspect the individual pieces of balsa wood, any irregularities in the balsa wood can act as stress concentrators. Another consideration is the amount of flexibility. Consider a 4 legged table. If the table is completely rigid and the 4 legs are not EXACTLY the same length, only 3 legs will be touching the floor. So... if you have carefully calculated the max load divided by 4, in reality, 3 legs will be experiencing more load than you calculated (33% of the load vs 25% and one leg will experience 0%). This is a great project. If you have the time and the balsa wood, build and test some prototype bridges first. Pay particular attention to where the prototypes fail and how they fail. Good luck

Answer 3

Most of the time, yes. The reason is that balsa wood is stronger in compression (how a tower works) than in bending (how a bridge works). But a particular layout might be stronger for a bridge than for a tower.

Answer 4

You bet they are.