RAM SS Redundancy Factors

[scanf1027]

I am using v11.2 and am having trouble with the redundancy factors for seismic analysis. I manually input the rho values as 1.0 in the load combination generator, as my project is SDC B. However, when I check the output it lists varying values of rho, typically 1.5. I checked the Manager Default Utility and the redundancy dialogue box only has IBC 2000 or UBC 1997 listed. My input should override that default anyway, but it doesn't seem to be working.

Any suggestions?

Thanks,

 

[SethGuthrie]

Older codes (IBC 2000, UBC 97) had a specific method for calculating redundancy factors that was applicable to computer analysis, and we implemented that.

The modern codes have a more subjective measure for redundancy. As such, the user must manually enter the redundancy factors (either 1.0 or 1.3 in X and Y) when generating Load Combinations within the Steel Mode for those codes.

Note, the program always calculates Rho per UBC 97 or IBC 2000 as noted. But it does not do anything with those number unless Load Combos are also generated per the same codes. At which point the user can have the program include the calculated Rho factors in the load combination factors OR they can override an put in user provided numbers. If the combos are being generated per some newer code, then the only option is user input values. Hence, the redundancy factor reports are irrelevant unless you are also generating combos based on the older codes.

 

[scanf1027]

Thanks Seth.

It seems odd though that the report doesn't report the actual values used in the analysis.

 

[Gumpmaster]

When you set up your seismic load combinations, is there an option to specify rho in the upper right hand corner?

Also, they're up to version 14 now. There's been a bunch of fixes, upgrades, and updates since then. If you can, it's worth it to upgrade.

 

[scanf1027]

Gumpmaster,
Thanks. I realized after I replied to Seth's post that the rho override takes place after the analysis, which is why I was seeing the calculated rho values.

I wish I could upgrade but it is not my company. I have to say I find it very difficult getting around in RAM and checking various properties seeing results in a quick manner. Maybe it's because it's an older version, but I'm partial to Risa 3D.

 

[scanf1027]

Seth,
I have another question if you don't mind. What am I missing with modeling cantilevers? It seems that I can't model a cantilever with a simply supported beam in the backspan. Am I missing something?

Thanks

 

[SethGuthrie]

For that you should model one simple span beam and one stub cantilever beam.
Note, stub cantilevers have only been around for the last couple of versions (starting w/ v14.02.00.00). Prior to that, a continuous beam with a cantilever was the only option.