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PDFWAC 51-50-1613

Section 1613Earthquake loads.

1613.4 Amendments to ASCE 7. The provisions of Section 1613.4 shall be permitted as an amendment to the relevant provisions of ASCE 7. The text of ASCE 7 shall be amended as indicated in Sections 1613.4.1 through 1613.4.2.
1613.4.1 ASCE 7 Section 12.2.5.4. Amend ASCE 7 Section 12.2.5.4 as follows:
12.2.5.4 Increased structural height limit for steel eccentrically braced frames, steel special concentrically braced frames, steel buckling-restrained braced frames, steel special plate shear walls, and special reinforced concrete shear walls. The limits on height, hn, in Table 12.2-1 are permitted to be increased from 160 ft (50 m) to 240 ft (75 m) for structures assigned to Seismic Design Categories D or E and from 100 ft (30 m) to 160 ft (50 m) for structures assigned to Seismic Design Category F, provided that the seismic force-resisting systems are limited to steel eccentrically braced frames, steel special concentrically braced frames, steel buckling-restrained braced frames, steel special plate shear walls, or special reinforced concrete cast-in-place shear walls and all of the following requirements are met:
1. The structure shall not have an extreme torsional irregularity as defined in Table 12.3-1 (horizontal structural irregularity Type 1b).
2. The steel eccentrically braced frames, steel special concentrically braced frames, steel buckling-restrained braced frames, steel special plate shear walls or special reinforced concrete shear walls in any one plane shall resist no more than 60 percent of the total seismic forces in each direction, neglecting accidental torsional effects.
3. Where floor and roof diaphragms transfer forces from the vertical seismic force-resisting elements above the diaphragm to other vertical force-resisting elements below the diaphragm, these in-plane transfer forces shall be amplified by the overstrength factor, Ωo for the design of the diaphragm flexure, shear, and collectors.
4. The earthquake force demands in foundation mat slabs, grade beams, and pile caps supporting braced frames and/or walls arranged to form a shear-resisting core shall be amplified by 2 for shear and 1.5 for flexure. The redundancy factor, ρ, applies and shall be the same as that used for the structure in accordance with Section 12.3.4.
5. The earthquake shear force demands in special reinforced concrete shear walls shall be amplified by the over-strength factor, Ωo.
1613.4.2 ASCE 7 Section 12.6. Amend ASCE 7 Section 12.6 and Table 12.6-1 to read as follows:
12.6 ANALYSIS PROCEDURE SELECTION
12.6.1 Analysis procedure. The structural analysis required by Chapter 12 shall consist of one of the types permitted in Table 12.6-1, based on the structure's seismic design category, structural system, dynamic properties, and regularity, or with the approval of the authority having jurisdiction, an alternative generally accepted procedure is permitted to be used. The analysis procedure selected shall be completed in accordance with the requirements of the corresponding section referenced in Table 12.6-1.
Table 12.6-1
Permitted Analytical Procedures
Seismic Design Category
Structural Characteristics
Equivalent Lateral Force Procedure, Section 12.8a
Modal Response Spectrum Analysis, Section 12.9.1, or Linear Response History Analysis, Section 12.9.2
Nonlinear Response History Procedures, Chapter 16a
B, C
All structures
P
P
P
D, E, F
Risk Category I or II buildings not exceeding two stories above the base
P
P
P
 
Structures of light frame construction
P
P
P
 
Structures with no structural irregularities and not exceeding 160 ft in structural height
P
P
P
 
Structures exceeding 160 ft in structural height with no structural irregularities and with T <3.5Ts
P
P
P
 
Structures not exceeding 160 ft in structural height and having only horizontal irregularities of Type 2, 3, 4, or 5 in Table 12.3-1 or vertical irregularities of Type 4, 5a, or 5b in Table 12.3-2
P
P
P
 
All other structures ≤ 240 ft in height
NP
P
P
 
All structures ˃ 240 ft in height
NP
NP
Pc
a
P: Permitted; NP: Not Permitted; Ts= SD1/SDS.
[Statutory Authority: RCW 19.27.031 and 19.27.074. WSR 20-21-021, § 51-50-1613, filed 10/9/20, effective 11/9/20; WSR 20-01-090, § 51-50-1613, filed 12/12/19, effective 7/1/20; WSR 19-02-038, § 51-50-1613, filed 12/26/18, effective 7/1/19; WSR 10-03-097, § 51-50-1613, filed 1/20/10, effective 7/1/10. Statutory Authority: RCW 19.27.190, 19.27.020, and chapters 19.27 and 34.05 RCW. WSR 08-01-110, § 51-50-1613, filed 12/18/07, effective 4/1/08.]
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