Tags: howe truss, k-truss, pratt truss, tips, truss design, warren truss
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Truss Design
Learn all the main types of trusses used in real bridges, and see how to apply them to model bridges. Learn the history of each common truss design. This page is designed to help you make an educated decision about what truss design you should use on your bridge.
Common trusses used in engineering:
Warren Truss
Warren Truss
The Warren truss is one of the most simple yet strong designs. This simple design already existed, but what made the Warren unique is that it uses equilateral triangles. Each side of the triangles are the same length. This marked an improvement over the older Neville truss which did not use equilateral triangles.
Go to a more in depth analysis of the Warren Truss.
Pratt And Howe Truss
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- Pratt Truss
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- Howe Truss
The Pratt and Howe trusses are very similar. In fact, the only difference is the direction the slanted members are angled. This changes which members are in compression and tension. On the Pratt truss, the shorter, vertical members are in compression. However, on the Howe truss, the longer, angled members are in compression. Because most materials (especially wood) that model bridge builders use decrease in the ability to resist compression the longer they are, I think the Pratt truss has an advantage.
There are more factors to consider, however. The Pratt and Howe trusses also differ in how they spread the load to the top and bottom chords. The Pratt truss has larger forces on the top and bottom chords than the Howe. Thus. you’d have to use bigger top and bottom chords.
Go to a more in depth analysis of the Pratt Truss.
Go to a more in depth analysis of the Howe Truss.
K Truss
K Truss
The K truss looks very good on paper. It shortens the lengths of the compression members compared to the other trusses. However, one must wonder if it adds additional weight simply because of the number of members. It is really interesting to note the two green members on the K truss, in theory those pieces could be taken off. However, I had to include them to make the truss design program work. This shows only one orientation of the K truss. If I reversed the direction of the K’s, I wonder how much it would change the forces.
Go to a more in depth analysis of the K Truss.
The one thing I don’t like about this truss is the long vertical compression member in the middle of the bridge. If that one member could be shortened or even eliminated, I think the bridge would become more efficient.The K truss would be the hardest of these trusses to build. This is something worth considering. Making a strong joint that would make the most of the switch between compression and tension of the vertical members would be difficult.
If you are interested in learning more about trusses and truss design, check out Truss Fun, Second Edition
I tried to build using the Bridge Designer, the first example of calculation used in the TRUSS DESIGN page (” On this Warren truss, each of the down arrows represents 50% of the load….). It does not calculate the load distribution:” No solution. Matrix is singular.” If I want to add memebers or nodes the formula relation” member+3=twice the Nodes” is not satisfied. What should I do to get your result?
I can’t really know what went wrong without seeing what you did. Just make sure that you don’t accidentally add an extra node somewhere.
there is mistake in calculating the forces in members of first warren truss,check it
I have double checked the first example and it seems fine to me. You have to remember that changing the dimensions of a bridge will affect its load distribution.
i am designing a bus station for my steel design subject, I would appreciate any ideas or suggestions.
I am doing a sience project on bridges could anyone give me any support?
If a weight was suspended from the middle of the K truss, which member would fail first?
David if i were you i would check the popsicle bridge area if the website it has kits to help you make popsicle stick bridges.
Also Peter i agree these fellas should do some reasearch for themselves but the thing is this is the best website to do it at there a myriads of links and resources about almost every aspect of bridge building design etc. ‘
Also we apologize for any question that we were not able to answer we will try our best to do so.
All you fellas:
Do some research yourself mate. Don’t just wait around for someone to reply to a post. I have got a similar project and have realised that you have to do some work! Answers dont just come without a price!
[edited by admin due to comment policy]
hey i am building a bridge out of popsickle sticks and i can only use 50 of them and it can only be 5 inches high and 4 inches wide
could you tell me the best truss design to use?
thanks man!!!!
Hey….. i am interested…. i have an assesment task for engineering studies. and am finding this website very helpful. although i am having some trouble determining what type of bridge i will use…….. could you give me any helpful hints……
Thanks man.
Wow! This website is sooo interesting.. now it is my home page on my computer!! i love it and its all i do in my free time!
Tap Dancer, sorry for not responding sooner. I got your second email but didn’t get around to answering those last two questions.
4. The tool I use even more than an exacto knife is a small wood saw blade. I got mine at a hobby store, and love it. I find it easier to use, and easier to make square cuts.
5. There are also some products from companies such as Pitsco that make cutting tools that are supposed to keep the wood perfectly square. I haven’t used any yet, but I am sure they work well.
thank you soo much I have been looking at different disigns for a truss bridge im a 8th grade student and Im mix some of the ideas that I’ve seen. I’ve tried to combined the basic ideas of warren, pratt, and howe. I’ve tried pratt and howe. I will also look at the K-truss and see the strengths i think would work best of it because it is a truely unquie disgin that i am glad I’ve found on this web site.
GB Tap Dance builder and i happen to go to the same school and are doing the same project so if you would like i could for ward the questions i asked you as well
these bridges are awsome they give me lots of ideas of how to build a bridge…… thanj you for your help
Hello, I emailed you before about an interview but I accidentally pressed submit before I was done so I would appreciate if you would answer a few more questions:
4. I’m using an Exacto-Knife to cut my pieces of wood, but it is not always square. Do you know of any other kind of knifes?
5. Since the pieces of wood are not always square, I have been sanding them, but it is very time consuming. Do you know of any other way?