# Scaling Design Values of Combined Response per ASCE 7-16 §12.9.1.4

How does ideCAD scale design values of combined response according to ASCE 7-16? • The combined response for the modal base shear (Vt) is compared with the calculated base shear (V) using the equivalent lateral force procedure automatically. If it is less than 100% of the calculated base shear (V) using the equivalent lateral force procedure, the forces are multiplied by V∕Vt automatically. • Where the combined response for the modal base shear (Vt) is less than CsW, drifts are multiplied by CsW∕Vt automatically.

Symbols

V = The equivalent lateral force procedure base shear
Vt = The base shear from the required modal combination
Cs = The seismic response coefficient
W = The effective seismic weight
R = The response modification factor in Table 12.2-1
Ie = The Importance Factor
SD1 = the design spectral response acceleration parameter at a period of 1.0 s
T = The fundamental period of the structure(s)

A base shear (V) is calculated in each of the two orthogonal horizontal directions using the calculated fundamental period of the structure T in each direction and the procedures of Section 12.8.

The seismic base shear, V, in the earthquake direction considered, is determined by the following equation. Scaling of Forces per ASCE 12.9.1.4.1

If the calculated fundamental period exceeds CuTa in a given direction, CuTa is used in lieu of T in that direction. Where the combined response for the modal base shear (Vt) is less than 100% of the calculated base shear (V) using the equivalent lateral force procedure, the forces is multiplied by V∕Vt.

Scaling of Drifts per ASCE 12.9.1.4.2

If the combined response for the modal base shear (Vt) is less than CsW, and where Cs is determined with Eq. (12.8-6), drifts are multiplied by CsW∕Vt.   JavaScript errors detected