Truss Reference Material

[MER3]

I am looking for some more in depth reference material for truss analysis. The standard methods we were taught all assume pinned members at each node. Not all trusses are built this way (members continuous across several nodes) and I am trying to analyze them using hand calcs/matrix methods. Does anyone know a good reference for a more accurate analysis?

 

[CANPRO]

I've always modeled the top and bottom chords as continuous, where continuous. Webs modeled with pinned ends. Typical web members won't have much flexural stiffness anyway, and modeling as pinned vs fixed usually won't make much of a difference to the overall truss.

If you want to analyze a truss accurately, I'm not sure hand calcs are the way to go - although certainly recommended for a check on your computer model. To get the most accurate results out of your analysis I would suspect an accurate computer model, including things like joint eccentricity, would be your best bet.

I should also add that this has been discussed many times on this site. You can search for the threads...I've found it easier to search the eng-tips archive via google. Link below.

https://www.google.ca/search?rlz=1C...yE-K6ggedjqf4BA&q=modeling+joists+truss+site:

http://www.eng-tips.com&oq=modeling.......0...1.1.64.psy-ab..8.0.0....0.gVi3r5MIJ-4

 

[MER3]

I had looked at older threads in the past, and most of them seem to discuss how to do this with a program. I do not want to use a program. I understand that the hand calcs for this will be more involved than a typical pinned-pinned truss, but I was hoping there would be some info out there for how to do this using matrix methods. I do not mind having to write a small python script or excel spreadsheet to do the matrix math, I just want to be able to produce it by hand and see every step. To be clear, I am not trying to design a 100+ member truss. I would like to be able to check a small scissor or Pratt truss though (or something along those lines)

 

[Shotzie]

You may want to start with the TPIC documents Link. I believe they get into the finer details of joint capacities, as well as modelling methods based on insertion points.

 

[Agent666]

This paper might be useful to making a determination if you need to consider secondary bending effects, or if simply designing as web members being pinned is acceptable (which it can be in many instances). Link

Depending on the relative stiffness of web vs chords I often check both for piece of mind and to get an envelope of the true behaviour, which is probably somewhere in between.

If you are familiar with the direct stiffness method (as it sounds like you are based on your responses), then its a matter of selecting a member stiffness matrix which includes all the effects that you want to consider. i.e. if you want to include secondary bending (shear deformations, temperature, etc, etc as others that could be included depending on how far into it you want to go).

Then your formulation for the member and global stiffness matrix assembly includes terms for the bending & axial effects, rather than say just the typical axial member stiffness matrix that might be used for a pinned member that can only output axial forces and deformations.

At some point the complexity of it and the time investment involved probably does mean it is likely to be easier to simply use a commercial program, but for smaller problems you can certainly use excel and program the DSM quite easily if you know what you are doing.