Response Modification Coefficient for Modal Analysis per ASCE 7-16 with ideCAD
How ideCAD defines the response modification coefficient R according to ASCE 7-16 for two earthquake directions?
Seismic reduction for modal analysis is determined automatically by R/I_{e}
R and I_{e} coefficients in the equations are defined by the user.
R and I_{e} coefficients are selected by the user in the analysis settings wizard, and report results are checked automatically.
SYMBOLS
R = The response modification factor in Table 12.2-1
I_{e} = The Importance Factor
The seismic force-related design parameters, such as story drift values, support forces, and individual member forces for each mode of response are calculated using each mode's properties and the response spectra divided by the quantity R ∕ I_{e}. The value for displacement and drift quantities is multiplied by the quantity C_{d }∕ I_{e}.
The design response spectrum is simulated of linear elastic structures. The inelastic behavior of the structure is explained by dividing the spectral coordinates by the response modification coefficient, R. Multiplying the spectral coordinates by the Importance Factor, Ie, provides the additional power needed to improve the performance of important structures. The displacements that are calculated using the response spectrum must be amplified by C_{d} and reduced by I_{e} to produce the expected inelastic displacements.
Structural System Type | Response Modification Coefficient, R | Overstrengh Factor, Ω_{o} | Deflection Amplification Factor, C_{d} | Structural System Limitations Including Structural Height, h_{n} (ft) Limits | ||||
---|---|---|---|---|---|---|---|---|
Seismic Design Category | ||||||||
B | C | D | E | F | ||||
A. Bearing Wall Systems | ||||||||
A1 - Special reinforced concrete shear walls | 5 | 2^{1/2} | 5 | NL | NL | 160 | 160 | 100 |
A2 - Ordinary reinforced concrete shear walls | 4 | 2^{1/2} | 4 | NL | NL | NP | NP | NP |
A3 - Detailed plain concrete shear walls | 2 | 2^{1/2} | 2 | NL | NP | NP | NP | NP |
A4 - Ordinary plain concrete shear walls | 1^{1/2} | 2^{1/2} | 1^{1/2} | NL | NP | NP | NP | NP |
B. Building Frame Systems | ||||||||
B1 - Steel eccentrically braced frames | 8 | 2 | 4 | NL | NL | 160 | 160 | 100 |
B2 - Steel special concentrically braced frames | 6 | 2 | 5 | NL | NL | 160 | 160 | 100 |
B3 - Steel ordinary concentrically braced frames | 3^{1/4} | 2 | 3^{1/4} | NL | NL | 35 | 35 | NP |
B4 - Special reinforced concrete shear walls | 6 | 2^{1/2} | 5 | NL | NL | 160 | 160 | 100 |
B5 - Ordinary reinforced concrete shear walls | 5 | 2^{1/2} | 4^{1/2} | NL | NL | NP | NP | NP |
B6 - Detailed plain concrete shear walls | 2 | 2^{1/2} | 2 | NL | NP | NP | NP | NP |
B7 - Ordinary plain concrete shear walls | 1^{1/2} | 2^{1/2} | 1^{1/2} | NL | NP | NP | NP | NP |
C. Moment-Resisting Frame Systems | ||||||||
C1 - Steel special moment frames | 8 | 3 | 5^{1/2} | NL | NL | NL | NL | NL |
C2 - Steel special truss moment frames | 7 | 3 | 5^{1/2} | NL | NL | 160 | 100 | NP |
C3 - Steel intermediate moment frames | 4^{1/2} | 3 | 4 | NL | NL | 35 | NP | NP |
C4 - Steel ordinary moment frames | 3^{1/2} | 3 | 3 | NL | NL | NP | NP | NP |
C5 - Special reinforced concrete moment frames | 8 | 3 | 5^{1/2} | NL | NL | NL | NL | NL |
C6 - Intermediate reinforced concrete moment frames | 5 | 3 | 4^{1/2} | NL | NL | NP | NP | NP |
C7 - Ordinary reinforced concrete moment frames | 3 | 3 | 2^{1/2} | NL | NP | NP | NP | NP |
D. Dual Systems with Special Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic Foces | ||||||||
D1 - Steel eccentrically braced frames | 8 | 2^{1/2} | 4 | NL | NL | NL | NL | NL |
D2 - Steel special concentrically braced frames | 7 | 2^{1/2} | 5^{1/2} | NL | NL | NL | NL | NL |
D3 - Special reinforced concrete shear walls | 7 | 2^{1/2} | 5^{1/2} | NL | NL | NL | NL | NL |
D4 - Ordinary reinforced concrete shear walls | 6 | 2^{1/2} | 5 | NL | NL | NP | NP | NP |
E. Dual Systems with Intermediate Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic Foces | ||||||||
E1 - Steel special concentrically braced frames | 6 | 2^{1/2} | 5 | NL | NL | 35 | NP | NP |
E2 - Special reinforced concrete shear walls | 6^{1/2} | 2^{1/2} | 5 | NL | NL | 160 | 100 | 100 |
E8 - Ordinary reinforced concrete shear walls | 5^{1/2} | 2^{1/2} | 4^{1/2} | NL | NL | NP | NP | NP |
F. Shear Wall-Frame Interactive System with Ordinary Reinforced Concrete Moment Frames And Ordinary Reinforced Concrete Shear Walls | ||||||||
F1 - Shear wall-frame interactive system | 4^{1/2} | 2^{1/2} | 4 | NL | NP | NP | NP | NP |
G. Cantilevered Column Systems Detailed to Conform to the Requirement for | ||||||||
G1 - Steel special cantilever column systems | 2^{1/2} | 1^{1/4} | 2^{1/2} | 35 | 35 | 35 | 35 | 35 |
G2 - Steel ordinary cantilever column systems | 1^{1/4} | 1^{1/4} | 1^{1/4} | 35 | 35 | NP | NP | NP |
G3 - Special reinforced concrete moment frames | 2^{1/2} | 1^{1/4} | 2^{1/2} | 35 | 35 | 35 | 35 | 35 |
G4 - Intermediate reinforced concrete moment frames | 1^{1/2} | 1^{1/4} | 1^{1/2} | 35 | 35 | NP | NP | NP |
G5 - Ordinary reinforced concrete moment frames | 1 | 1^{1/4} | 1 | 35 | NP | NP | NP | NP |
H. Steel Systems not Specifically Detailed for Seismic Resistance, Excluding Cantilever Column Systems | ||||||||
H - Steel Systems not Specifically Detailed for Seismic Resistance | 3 | 3 | 3 | NL | NL | NP | NP | NP |