Page Comparison

The elastic deformations calculated under reduced forces (see Section C12.8.6) are multiplied by the deflection amplification factor, C_d, to estimate the deformations likely to result from the design earthquake ground motion. SYMBOLS

C_d = Deflection amplification factor
R = Response modification coefficient
I_e = Importance factor
δ_xe = Deflection

...

The application of the factor R/I_e to the design response spectrum reduces not only design forces but also displacements. To compensate for this, ASCE 7 requires that the deflections at level x at the center of mass, δ_x, be determined in accordance with where C_d is from Table 12.2-1, I_e is from Table 11.5-1, and δ_xe is the deflection determined by elastic analysis with seismic forces reduced by factor R/I_e. Using a value C_d equal to R would result in the displacement δ_x being equal to δ_xe, which would be consistent with the equal displacement rule.

...

Topics covered in this section:

...