Redundancy factor, ρ, is automatically obtained horizontal seismic forces according to ASCE 7-16 Section 12.3.4.


SYMBOLS

ρ = Redundancy factor

QE = Effects of horizontal seismic forces from V or Fp


A redundancy factor, ρ, is used to the seismic force-resisting system in each of two orthogonal directions for all structures in accordance with Eq. 12.4-3.

According to 12.3.4.1 - ρ is 1.0

  1. Structures assigned to Seismic Design Category B or C

  2. Drift calculation and P-delta effects

  3. Design of collector elements, splices, and their connections for which the seismic load effects, including overstrength of Section 12.4.3, are used

  4. Design of members or connections where the seismic load effects, including overstrength of Section 12.4.3, are required for design

  5. Diaphragm loads determined using Eq. (12.10-1), including the limits imposed by Eqs. (12.10-2) and (12.10-3)

  6. Structures with damping systems designed in accordance with Chapter 18

  7. Design of structural walls for out-of-plane forces, including their anchorage


12.3.4.2 Redundancy Factor, ρ, for Seismic Design Categories D through F

For structures assigned to Seismic Design Category D and having extreme torsional irregularity as defined in Table 12.3-1, Type 1b, ρ is equal 1.3.

For other structures assigned to Seismic Design Category D and for structures assigned to Seismic Design Categories E or F, ρ is controlled automatically. And the programme use 1.3 unless one of the following two conditions is occured.

Seismic Design Categories E and F are not allowed to use because extreme torsional irregularities are prohibited (see Section 12.3.3.1).
a. Each story resisting more than 35% of the base shear in the direction of interest comply with Table 12.3-3.


b. Structures are regular in plan at all levels provided that the seismic force-resisting systems consist of at least two bays of seismic force-resisting perimeter framing on each side of the structure in each orthogonal direction at each story resisting more than 35% of the base shear.