SYMBOLS
Eh = Horizontal seismic load effect
hwall = height of shear wall
hwp = height of wall pier
Lwall = length of shear wall
Lwp = length of wall pier
ρ = Redundancy factor
QE = Effects of horizontal seismic forces from V or Fp
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A redundancy The Redundancy factor, ρ, is used to for the seismic force-resisting system in each of two orthogonal directions for all structures in accordance with Eq. 12.4-3.
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According to 12.3.4.1 - ρ is 1.0 for the following:
Structures assigned to Seismic Design Category B or C
Drift calculation and P-delta effects and story drift calculation
Design of collector elements, splices, and their connections for which using the seismic load effects , including with the overstrength factor of Section 12.4.3, are used
Design of members or connections where the seismic load effects, including overstrength of Section 12.4.3, are required for designfactor
Diaphragm loads determined using Eq. (12.10-1), including the limits imposed by Eqs. (12.10-2) and (12.10-3)
Structures with damping systems designed in accordance with per ASCE Chapter 18
Design of structural walls for out-of-plane forces, including their anchorage
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Redundancy Factor, ρ, for Seismic Design Categories D through F
For structures assigned to Seismic Design Category D and having with extreme torsional irregularity as defined in Table 12.3-1, Type 1b, ρ is equal equals 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 Moreover, the software uses 1.3 unless one of the following two conditions is occuredoccurs.
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
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according to Table 12.3-3.
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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.
Lateral Force-Resisting Element | Requirement |
|---|---|
Braced frames | Removal of an individual brace, or connection thereto, would not result in more than a 33% reduction in story strength, nor does the resulting system have an extreme torsional irregularity (horizontal structural irregularity Type 1b). |
Moment frames | Loss of moment resistance at the beam-to-column connections at both ends of a single beam would not result in more than a 33% reduction in story strength; nor does the resulting system have an extreme torsional irregularity (horizontal structural irregularity Type 1b). |
Shear walls or wall piers with a height-to-length ratio greater than 1.0 | Removal of a shear wall or wall pier with a height-to-length ratio greater than 1.0 within any story, or collector connections thereto, would not result in more than a 33% reduction in story strength; nor does the resulting system have an extreme torsional irregularity (horizontal structural irregularity Type 1b). The shear wall and wall pier height-to-length ratios are determined as shown in Figure. |
Cantilever columns | Loss of moment resistance at the base connections of any single cantilever column would not result in more than a 33% reduction in story strength; nor does the resulting system have an extreme torsional irregularity (horizontal structural irregularity Type 1b). |
Other | No requirements. |
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