Cs(max) ASCE 7-16

Question

The upper value of 'Cs' computed in accordance with eq. 12.8-2 need not exceed eq. 12.8-3 or 12.8-4, whichever applies. In Frame, under 'Loads and Applied Forces', this check doesn't appear to be included. What am I missing?

Seth Guthrie · Answer

Do you have the option to Apply Section 12.8.1.3 checked? 
 
 Maximum SDS Value in Determination of Cs and Ev: 12.8.1.3 
 The values of Cs and Ev are permitted to be calculated using a value of SDS equal to 1.0, but not less than 70% of SDS, as defined in Section 11.4.5, provided that all 6 criteria defined in Section 12.8.1.3 are fulfilled. 
 A checkbox is added to the load case dialog so that the program check the limitation mentioned in this section. If this option is checked out, the program confirms the criteria 5 and 6 are not violated. After the analysis is completed, the program also checks out the criteria 3 is not violated.

Seth Guthrie · Answer

We don't have a convenient way to force the program to use a specific Sds value (or Sd1 value) for site-specific data. I usually suggest user defined story force because then you are in complete control. manipulating the load case input (T, Ss, S1) does not always result in the specific desired output. 
 What might be useful is a kind of generic seismic load where the user would provide those values directly, but the program would still do the vertical distribution of the force and the accidental eccentricity work automatically. Let us know what might work well for you.