Best structural analysis software for multiple support conditions

[dozer]

I've been using STAAD for years. I very often have cases where I'm designing large equipment that has to be analyzed being lifted in the horizontal position, lifted in the vertical position and analyzed in place. This, of course, requires different support conditions for different load cases. STAAD allows this but they have some really dumb a$$ rules about redefining support conditions in the same file. I've asked them to join the rest of us in the 21st century and not make it so hard but I've decided they are never going to do it. Does anyone know of good software that will handle something like this with ease? Something that was actually intended to handle this and not just an afterthought they shoehorned into their code.

 

[IDS]

I'd imagine that most general purpose FEA programs would do what you want.

The only one I am familiar with is Strand7 which provides for the following options:

Multiple "Freedom Cases" can be defined which can be:

1) Combined with selected Load Cases in linear analyses.
2) Different factors applied (to node displacements) in an incremental non-linear analysis
3) Switched on or off in a non-linear staged analysis.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[WARose]

I very often have cases where I'm designing large equipment that has to be analyzed being lifted in the horizontal position, lifted in the vertical position and analyzed in place. This, of course, requires different support conditions for different load cases. STAAD allows this but they have some really dumb a$$ rules about redefining support conditions in the same file.

Me personally, I wouldn't want all that in the same file. But to answer your question, are you sure the CHANGE command won't do that (in STAAD)? I seem to remember some way you could do that in the load cases/combinations. (That may be the "dumb a$$" rule you were talking about.)

 

[dozer]

WARose, It is precisely the CHANGE command that will allow you to do multiple support conditions. I'm asking is there a program like STAAD that does this better. There are actually two dumb a$$ rules. Here they are from the help file concerning the CHANGE command:

- allows the re-specification of the supports with another SUPPORT command that causes the old supports to be ignored. The SUPPORT specification must be such that the number of joint directions that are free to move (DOF or "releases") before the CHANGE must be greater than or equal to the number of "releases" after the CHANGE.

- the supports must be specified in the same order before and after the CHANGE command. To accomplish this when some cases have more supports than others do, you can enter unrestrained joints into the SUPPORT command list using FIXED BUT FX FY FZ MX MY MZ. It is best to put every joint that will be supported in any case into every SUPPORT list.

I'm looking for a program that will allow you to respecify supports without having to ensure they are in the same order and qty. as the one before and you don't have to worry about the number of degrees of freedom.

I've went the multiple file route many times and it's no picnic. Any change you make in one file you have to make in all. I used to design offshore structures (not in STAAD, thank goodness) that would have in-place, loadout, transport, and lift conditions. It was a massive PITA to keep all the files in sync.

 

[bones206]

Would it be a helpful workaround to define all support DOFs as springs? Then you could assign really low spring constants for releases and really high constants for fixed support DOFs, modifying with the CHANGE command as needed.

 

[dozer]

Bones, interesting suggestion. I may give that a try but I'm still looking for suggestions for a better program. I don't want to have to use workarounds to make it behave like I want it to.

 

[Mohanlal0488]

I have to agree with IDS.

Strand7 is one of the best FEA packages I have ever worked on.
Unbelievably powerful!!!

 

[dozer]

I downloaded the Strand7 help file. It's ability to do construction sequence looks like it may do what I what. I didn't see where it would do design though. The word "design" isn't even listed in the index. Will it not do code checking? I would be most interested in it being able to check per AISC 360 various editions but having other codes available would be a plus.

 

[IDS]

dozer - They have a concrete design add-in, which I have but never use. As far as I know they don't have any steel design (other than libraries of steel cross section shapes).

I just checked the help. It looks like they only cover Eurocode 2 and AS 3600 (Australian code for concrete buildings), but best check with your regional supplier.

Doug Jenkins
Interactive Design Services

http://newtonexcelbach.wordpress.com/

 

[Mohanlal0488]

Strand7 can only do FEA. If you get the API you can program the required codes into the software.
If you are looking for something similar to Strand7 that has codes I would suggest Lusas.
I messed around with it for a short time, the biggest downfall is it's poor interface and as with any software that has built in codes it lacks some of the useful postprocessing features which Strand7 has.

 

[Ussuri]

Another method is to define your supports as a load case by using prescribed displacements. So you define your supports with set displacement of say 0.001mm and then ensure you apply the displacement load case first before any other loads.