Structural Drawing - Seismic Criteria

[WiSEiwish]

Is it generally a good idea to list R, Cd, and Ω for each direction of seismic loading on structural drawings? I would imagine when using a R=3 system, it would only be necessary to include one set of R, Cd, and Ω.

Thanks.

 

[SteelPE]

I usually follow the requirements of IBC section 1603. If you have two different systems in each direction you would want to include this on the drawings somewhere together with some sort of locus so a future engineer looking at your drawings will know what you were talking about (like a north arrow and then reference N-S R=3, E-W R=3.5).

 

[cliff234]

I agree with SteelPE. We list the values in each orthogonal direction. Even if we have the same R factor, the building periods might be different in each direction resulting in different base shears for a long period building. We also list the period and the base shear along with the other values on our general notes. Likewise we list the wind loading base shear on our general notes sheet so that someone looking at the drawings can see the magnitude of each. I always like to know how the wind base shear compares to the seismic base shear - and listing those values on the drawings makes it clear to everyone.

 

[WiSEiwish]

That all makes sense to me. It seemed like a good idea to include both directions, but I wanted to see what other people were doing.

Thanks.

 

[TDIengineer]

On a similar note, I have had a plan check agency require you to list the actual base shear used... As in the mass x Cs. I thought that was not really the spirit of the code. Although knowing the initial bldg design mass would be helpful when evaluating future additions or added mass and the 5% rule.