DAM ENGINEERING-RISA FOUNDATION

[eberger]

Has Anyone setup RISA 3D/foundation to do a stability analysis on a hydraulic structure such as a dam that requires USACE load combination? Or some other analysis software?

 

[Lomarandil]

Yes. You simply need to manually generate the load combinations, instead of relying on the LC generator.

 

[eberger]

thanks, but how do you model the 3D concrete structure? Retaining walls are over simplified and doesn't allow for the unique geometry that I need to recreate.

 

[JoshPlumSE]

I haven't seen much in the way of actual Dams. I have seen plenty of stability analysis of soil supported structures though. My thoughts:
a) Modeling the soil is definitely tricky. RISA is really an elastic analysis program, so you're not going to get much non-linear behavior out of the soil springs. The best you can do is have elastic springs that are compression only or tension only.

b) If the loading is CLOSE to overturning the structure that often creates problems with the solver. To handle this, I often suggest adding a few very soft springs (1/100th the stiffness of the regular soil spring) to provide stability in all directions if overturning occurs. You have to monitor the reactions in these springs. That (along with the deflected shape plots) is what tells you when you've got stability issues.

 

[Lomarandil]

If you really need to capture 3D geometry of your structure, RISA may not be the best option. Solid elements are available, but I get the impression that they are not as user-friendly as other softwares that are built with 3d solid structures in mind.

If a 2D slice of the structure is suitable, plate elements should do nicely.

 

[strucbells]

our dam folks seem to use ANSYS and LS-DYNA for any dam of decent size, especially when seismic loads are involved. not sure RISA/STAAD/etc. can really capture the behavior