Min versus default radius - horizontal geometry

Hello Mandar,

Have you set any design standards for the design? If you have toggled any of them to ON, ORD will set the default radius as per the standard selected. You will need to toggle off the setting and then check. Hope this help resolve the issue. Do let me know.

Yes, a design standard was set and the min radius is based on this standard. The question is why can't I use this min radius allowed by the standard. If I use it, I get a warning message. The software suggests a default radius, which is higher than the min radius. My manual calculation also gives me the min radius suggested by the program. So, what is this default radius? It certainly isn't the min radius.

The default radius is used in a couple of commands (chain by PI for example) to base design on a set standard. If you are not likely to use the default, you can alter the standard so it and the minimum are together. The other option is to shut off the warnings in the Civil Message Center, this will show just the errors then with a glyph. 

Thank you for your response. But I still don't understand what that default radius is. How does OpenRoads choose this value?

Second question first, the design standards are stored in a DGNLIB defined by the variable CIVIL_DESIGNSTANDARDSDGNLIBLIST and can be found in the Explorer under Design Standards.

The software will default to this value when using certain commands if a design standard is set during element creation. The place I see it most is the Complex by PI command. While laying out with this command the software populates the radius used in the process is set with the default. The user still has the ability to choose the radius desired.

Hope that provides a little more insight.

Steven:

Thanks a lot for your response. Perhaps I did not frame my question properly. I understand that ORD picks up values from the AASHTO standards and uses them. I can see that the value used for the minimum radius of a curve for a design speed of 75 mph and allowable maximum superelevation of 6% is 2500 from Table 3-7 of the AASHTO Green Book - 2011.  This is value used by ORD for the minimum radius, which is correct.  But the default radius recommended by ORD for this curve is 3910 ft. So, here's my question: how was this value of 3910 ft selected/calculated/obtained by ORD?

I think I am seeing the distinction here. ORD uses ("selects") that value, because it is defined in the DGNLIB as the default radius. Now why that particular value was used to populate the DGNLIB, (or why Bentley added the option) that I can't speak to. I, similar to you, have always really cared about the minimum, and don't recall the AASHTO standards defining anything beyond that. 

I think I am seeing the distinction here. ORD uses ("selects") that value, because it is defined in the DGNLIB as the default radius. Now why that particular value was used to populate the DGNLIB, (or why Bentley added the option) that I can't speak to. I, similar to you, have always really cared about the minimum, and don't recall the AASHTO standards defining anything beyond that. 

I was also running into this issue of how ORD selected a "default" value. I'd rather a minimum radius automatically pop up. How do you set the minimum radius to the default radius?