Influence the overall strength of a truss bridge?

[lineup]

Hi all, I've been looking at a few trusses lately and was wondering what the main factors are that influence the overall strength of a truss bridge? I have an idea that the more members taking loads, the stronger the truss, hence members should be at sharper angles. Of course i could be dead wrong, perhaps certain angles allow a better distribution of loads through all members thus allowing a greater overall load to be placed on a truss bridge? I Am looking at point-loads specifically but would be interested in moving loads as well.

 

[TVP45]

There are ways I might suggest.

One is to take the classic truss designs (Pratt, Burr, king-post, queen-post, etc.) and ask why they worked well enough to have been used. Try something like, for example, a bridge across a 5 meter wide creek, using different trusses. Take a walk around and find truss designs in real life, particularly railroads (they were usually cheap and strong). Study those.

The other is to download one of the free, or low-cost shareware, programs and simply "play around" with different ideas.