# 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/Ie

• R and Ie coefficients in the equations are defined by the user.

• R and Ie 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
Ie = 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 ∕ Ie. The value for displacement and drift quantities is multiplied by the quantity Cd ∕ Ie.

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 Cd and reduced by Ie to produce the expected inelastic displacements.

Structural System Type

Response Modification Coefficient, R

Overstrengh Factor, Ωo

Deflection Amplification Factor, Cd

Structural System Limitations Including Structural Height, hn (ft) Limits

Seismic Design Category

B

C

D

E

F

A. Bearing Wall Systems

A1 - Special reinforced concrete shear walls

5

21/2

5

NL

NL

160

160

100

A2 - Ordinary reinforced concrete shear walls

4

21/2

4

NL

NL

NP

NP

NP

A3 - Detailed plain concrete shear walls

2

21/2

2

NL

NP

NP

NP

NP

A4 - Ordinary plain concrete shear walls

11/2

21/2

11/2

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

31/4

2

31/4

NL

NL

35

35

NP

B4 - Special reinforced concrete shear walls

6

21/2

5

NL

NL

160

160

100

B5 - Ordinary reinforced concrete shear walls

5

21/2

41/2

NL

NL

NP

NP

NP

B6 - Detailed plain concrete shear walls

2

21/2

2

NL

NP

NP

NP

NP

B7 - Ordinary plain concrete shear walls

11/2

21/2

11/2

NL

NP

NP

NP

NP

C. Moment-Resisting Frame Systems

C1 - Steel special moment frames

8

3

51/2

NL

NL

NL

NL

NL

C2 - Steel special truss moment frames

7

3

51/2

NL

NL

160

100

NP

C3 - Steel intermediate moment frames

41/2

3

4

NL

NL

35

NP

NP

C4 - Steel ordinary moment frames

31/2

3

3

NL

NL

NP

NP

NP

C5 - Special reinforced concrete moment frames

8

3

51/2

NL

NL

NL

NL

NL

C6 - Intermediate reinforced concrete moment frames

5

3

41/2

NL

NL

NP

NP

NP

C7 - Ordinary reinforced concrete moment frames

3

3

21/2

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

21/2

4

NL

NL

NL

NL

NL

D2 - Steel special concentrically braced frames

7

21/2

51/2

NL

NL

NL

NL

NL

D3 - Special reinforced concrete shear walls

7

21/2

51/2

NL

NL

NL

NL

NL

D4 - Ordinary reinforced concrete shear walls

6

21/2

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

21/2

5

NL

NL

35

NP

NP

E2 - Special reinforced concrete shear walls

61/2

21/2

5

NL

NL

160

100

100

E8 - Ordinary reinforced concrete shear walls

51/2

21/2

41/2

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

41/2

21/2

4

NL

NP

NP

NP

NP

G. Cantilevered Column Systems Detailed to Conform to the Requirement for

G1 - Steel special cantilever column systems

21/2

11/4

21/2

35

35

35

35

35

G2 - Steel ordinary cantilever column systems

11/4

11/4

11/4

35

35

NP

NP

NP

G3 - Special reinforced concrete moment frames

21/2

11/4

21/2

35

35

35

35

35

G4 - Intermediate reinforced concrete moment frames

11/2

11/4

11/2

35

35

NP

NP

NP

G5 - Ordinary reinforced concrete moment frames

1

11/4

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

JavaScript errors detected