N.Y.C. Admin. Code § BC 1613: Section BC 1613: Earthquake Loads

1613.1 Scope.

Every structure, and portion thereof, including nonstructural components that are permanently attached to structures and their supports and attachments, shall be designed and constructed to resist the effects of earthquake motions in accordance with ASCE 7, excluding Chapter 14 and Appendix 11A. The seismic design category for a structure shall be determined in accordance with either Section 1613 or ASCE 7.

Exceptions:

1. One- and two-family dwellings three stories or less in height.

2. The seismic force-resisting system of wood-frame buildings that conform to the provisions of Section 2308 are not required to be analyzed as specified in this section.

3. Agricultural storage structures intended only for incidental human occupancy.

4. Structures that require special consideration of their response characteristics and environment that are not addressed by this code or ASCE 7 and for which other regulations provide seismic criteria, such as vehicular bridges, electrical transmission towers, hydraulic structures, buried utility lines and their appurtenances and nuclear reactors.

1613.2 Definitions.

The following terms are defined in Chapter 2:

DESIGN EARTHQUAKE GROUND MOTION.

MAXIMUM CONSIDERED EARTHQUAKE (MCE) GROUND MOTION.

MAXIMUM CONSIDERED EARTHQUAKE GEOMETRIC MEAN (MCEG) PEAK GROUND ACCELERATION.

MECHANICAL SYSTEMS.

ORTHOGONAL.

RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCER) GROUND MOTION RESPONSE ACCELERATIONS.

SEISMIC DESIGN CATEGORY.

SEISMIC FORCE-RESISTING SYSTEM.

SITE CLASS.

SITE COEFFICIENTS.

1613.3 Seismic ground motion values.

Seismic ground motion values shall be determined in accordance with this section.

1613.3.1 Mapped acceleration parameters.

The mapped maximum considered earthquake spectral response acceleration at short periods (S

s

) shall be 0.296 g and at 1-s period (S

1

) shall be 0.061 g. The mapped long-period transition period (T

L

) shall be 6.0 seconds. Alternatively, electronic values of mapped acceleration parameters S

s

and S

1

and other seismic design parameters provided at the U.S. Geological Survey (USGS) website at https://doi.org/10.5066/F7NK3C76 may be used as per the guidelines of ASCE 7, Section 11.4.

1613.3.2 Site class definitions.

Based on the site soil properties, the site shall be classified as Site Class A, B, C, D, E or F in accordance with Chapter 20 of ASCE 7, and this code. Where the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the commissioner or geotechnical data determines Site Class E or F soils are present at the site.

1613.3.3 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters.

The maximum considered earthquake spectral response acceleration for short periods, S

MS

, and at 1-second period, S

M1

, adjusted for site class effects shall be determined by Equations 16-44 and 16-45, respectively:

S

MS

= F

a

S

s

(Equation 16-44)

S

M1

= F

v

S

1

(Equation 16-45)

where:

F

a

= Site coefficient defined in Table 1613.3.3(1).

F

v

= Site coefficient defined in Table 1613.3.3(2).

S

s

= The mapped MCER spectral accelerations for short periods as determined in Section 1613.3.1.

S

1

= The mapped MCER spectral accelerations for a 1-s period as determined in Section 1613.3.1.

Exception: When electronic values of mapped acceleration parameters are used as per Section 1613.3.1 of this code, the site coefficients, F

a

and F

v

, cannot be taken from Tables 1613.3.3(1) and 1613.3.3(2) of this code. Rather, general procedures in Chapter 11 of ASCE 7 shall be followed to determine F

a

and F

v

.

Table 1613.3.3(1) Values of Site Coefficient

F

a

as a Function of Site Class and Mapped Spectral Response Acceleration at Short Periods (S

S

)

a

Site Class

F

a

A

0.80

B (V

s

measured)

0.90

B (V

s

unmeasured)

1.00

C

1.30

D

1.57

E

2.28

F

Note a

a. Site-specific geotechnical investigation and dynamic site response analyses shall be performed to determine appropriate values, except that for structures with periods of vibration equal or less than 0.5 second, values of F

a

for liquefiable soils are permitted to be taken equal to the values for the site class determined without regard to liquefaction in Section 1613.3.4.1.

Table 1613.3.3(2) Values of Site Coefficient

F

v

as a Function of Site Class and Mapped Spectral Response Acceleration at 1-Second Period (

S

1

)

a

Site Class

F

v

A

0.80

B (V

s

measured)

0.90

B (V

s

unmeasured)

1.00

C

1.50

D

2.40

E

4.20

F

Note a

a. Site-specific geotechnical investigation and dynamic site response analyses shall be performed to determine appropriate values, except that for structures with periods of vibration equal or less than 0.5 second, values of F

v

for liquefiable soils are permitted to be taken equal to the values for the site class determined without regard to liquefaction in Section 1613.3.4.1.

1613.3.4 Design spectral response acceleration parameters.

Five-percent damped design spectral response acceleration at short periods, S

DS

, and at 1-s period, S

D1

, shall be determined from Equations 16-46 and 16-47, respectively:

S

DS

= 2/3 S

MS

(Equation 16-46)

S

D1

= 2/3 S

M1

(Equation 16-47)

where:

S

MS

=

The MCE

R

spectral response accelerations for short period as determined in Section 1613.3.3.

S

M1

=

The MCE

R

spectral response accelerations for 1 second period as determined in Section 1613.3.3.

1613.3.4.1 Site classification for seismic design.

Site classification for Site Class C, D or E shall be determined from Table 1613.3.4.1. The notations presented below apply to only materials encountered above rock meeting Class 1a, 1b, or 1c as defined in Section 1803 or rock with shear wave velocity greater than 2,500 feet per second (762 meters per second) to a maximum depth of 100 feet (30 480 mm). Profiles containing distinctly different soil and rock layers shall be subdivided into those layers designated by a number that ranges from 1 to n at the bottom where there is a total of n distinct layers in the upper 100 feet (30 480 mm). The symbol i then refers to any one of the layers between 1 and n. For situations in which site investigations, performed in accordance with Chapter 20 of ASCE 7, reveal rock conditions consistent with Site Class B, but site-specific velocity measurements are not made, the site coefficients F

a

, F

v

, and F

PGA

shall be taken as unity (1.0).

where:

v

si

=

The shear wave velocity in feet per second (m/s).

d

I

=

The thickness of any layer between 0 and 100 feet (30 480 mm).

where:

v

si

= The shear wave velocity in feet per second (m/s).

d

i

= The thickness of any layer between 0 and 100 feet (30 480 mm).

(Equation 16-48)

where: N

i

is the Standard Penetration Resistance (ASTM D 1586) not to exceed 100 blows/foot (328 blows/m) as directly measured in the field without corrections. When refusal is met for a rock layer of Class 1d, N

i

shall be less than or equal to 100 blows/foot (328 blows/m) provided that the extent of the Class 1d material is confirmed by a boring to a depth where Class 1c or better rock is determined, not to exceed 100 feet (30 480 mm). Alternatively, if this boring is not performed, site classification should be based on all soil material that is above the Class 1d layer.

(Equation 16-49)

(Equation 16-50)

where:

Use only d

i

and N

i

for cohesionless soil layers only in Equation 16-50.

d

s

= The total thickness of cohesionless soil layers in the top 100 feet (30 480 mm).

m = The number of cohesionless soil layers in the top 100 feet (30 480 mm).

S

ui

= The undrained shear strength in psf (kPa), not to exceed 5,000 psf (240 kPa), ASTM D 2166 or ASTM D 2850.

where:

d

c

= The total thickness (100-d

s

) (For SI: 30 480-d

s

) of cohesive soil layers in the top 100 feet (30 480 mm).

k = The number of cohesive soil layers in the top 100 feet (30 480 mm).

PI = The plasticity index, ASTM D 4318.

w = The moisture content in percent, ASTM D 2216.

Where a site does not qualify under the criteria for Site Class F and there is a total thickness of soft clay greater than 10 feet (3048 mm) where a soft clay layer is defined by s

u

< 500 psf (24 kPa), w ³ 40 percent, and PI < 20, it shall be classified as Site Class E. The shear wave velocity for rock, Site Class B, shall be either measured on site or estimated by a geotechnical engineer or engineering geologist/seismologist for competent rock with moderate fracturing and weathering. Softer and more highly fractured and weathered rock shall either be measured on site for shear wave velocity or classified as Site Class C. The hard rock category, Site Class A, shall be supported by shear wave velocity measurements either on site or on profiles of the same rock type in the same formation with an equal or greater degree of weathering and fracturing. Where hard rock conditions are known to be continuous to a depth of 100 feet (30 480 mm), surficial shear wave velocity measurements are permitted to be extrapolated to assess v

s

. The rock categories, Site Classes A and B, shall not be used if there is more than 10 feet (3048 mm) of soil between the rock surface and the bottom of the spread footing or mat foundation.

Table 1613.3.4.1 Site Classification

a

Site Class

v

s

N

or

N

ch

s

v

E

< 600 ft/s

< 15

< 1,000 psf

D

600 to 1,200 ft/s

15 to 50

1,000 to 2,000 psf

C

1,200 to 2,500 ft/s

> 50

> 2,000

For SI: 1 foot per second = 304.8 mm per second, 1 pound per square foot = 0.0479 kN/m

2

.

a. If the s

v

method is used and the N

ch

and s

v

criteria differ, select the category with the softer soils (for example, use Site Class E instead of D).

1613.3.4.1.1 Steps for classifying a site.

The following steps shall be performed during the classification of a site:

1. Check for the four categories of Site Class F requiring site-specific evaluation. If the site corresponds to any of these categories, classify the site as Site Class F and conduct a site-specific evaluation according to ASCE 7 and the requirements of Section 1815.

2. Check for the existence of a total thickness of soft clay > 10 feet (3048 mm) where a soft clay layer is defined by: s

u

< 500 psf (24 kPa), w ³ 40 percent and PI > 20. If these criteria are satisfied, classify the site as Site Class E.

3. Categorize the site using one of the following three methods with v

s

, N, or s

u

and computed in all cases as specified.

3.1. v

s

for the top 100 feet (30 480 mm) ( v

s

method).

3.2. N for the top 100 feet (30 480 mm) (N method).

3.3. N

ch

for cohesionless soil layers (PI < 20) in the top 100 feet (30 480 mm) and average, s

u

, for cohesive soil layers (PI > 20) in the top 100 feet (30 480 mm) (s

u

method).

1613.3.5 Determination of seismic design category.

All structures shall be assigned a seismic design category based on their risk category and the design spectral response acceleration parameters, S

DS

and S

D1

, determined in accordance with Section 1613.3.4 of this code or the site- specific procedures of ASCE 7. Each building and structure shall be assigned to the seismic design category in accordance with Table 1613.3.5 of this code, irrespective of the fundamental period of vibration of the structure, T.

Exception: When electronic values of mapped acceleration parameters are used as per Section 1613.3.1, the seismic design category for Risk Category IV structures shall not differ from the values in Table 1613.3.5.

Table 1613.3.5 Seismic Design Category

Risk Category

Site Class

A

B / C / D

E

I / II / III

A

B

C

IV

A

C

D

1613.3.5.1 Alternative seismic design category determination.

The seismic design category is permitted to be determined from Table 11.6-1 of ASCE 7 alone, except for Risk Category IV structures for which Table 1613.3.5 of this code shall be used, when all of the following apply:

1. In each of the two orthogonal directions, the approximate fundamental period of the structure, T

a

, in each of the two orthogonal directions determined in accordance with Section 12.8.2.1 of ASCE 7, is less than 0.8 T

s

determined in accordance with Section 111.4.6 of ASCE 7.

2. In each of the two orthogonal directions, the fundamental period of the structure used to calculate the story drift is less than T

s

.

3. Equation 12.8-2 of ASCE 7 is used to determine the seismic response coefficient, C

s

.

4. The diaphragms are rigid or are permitted to be idealized as rigid in accordance with Section 12.3.1 of ASCE 7 or, for diaphragms permitted to be idealized as flexible in accordance with Section 12.3.1 of ASCE 7, the distances between vertical elements of the seismic force-resisting system do not exceed 40 feet (12 192 mm).

1613.3.5.2 Simplified design procedure.

Where the alternate simplified design procedure of ASCE 7 is used, the seismic design category shall be determined in accordance with ASCE 7.

1613.4 Structural separations.

All structures shall be separated from adjacent structures. When a structure adjoins a property line not common to a public way (typically side or rear lot lines), that structure shall also be set back from the property line by at least 1 inch (25.4 mm) for each 50 feet (15 240 mm) of height and a minimum of 1 inch (25.4 mm) for structures with heights less than 50 feet (15 240 mm). For structures in Seismic Design Category D, refer to ASCE 7 for additional requirements.

Exception: Smaller separations or property line setbacks shall be permitted when justified by rational analysis based on maximum expected ground motions with a minimum separation of 1 inch (25.4 mm) along the full height of the structure.

1613.4.1 Masonry structures.

For structures adjacent to existing unreinforced masonry bearing wall structures, the structural separation shall be filled with a material with a minimum compressive strength of 25 psi (172.37 kPa) and a maximum compressive strength of 100 psi (689.47 kPa). Additionally, when the adjacent wall is a party wall, the party wall shall be made secure by the party responsible for the new construction as per Chapter 33.

1613.4.2 Covers.

The infill material shall be covered on all sides and shall meet the appropriate provisions of Chapter 26. The covering must be of adequate strength to resist the wind loads for cladding as specified in Chapter 16 and shall conform to all applicable provisions in Chapter 14.

1613.4.3 Covers wider than 5 inches (127 mm).

When a building separation wider than 5 inches (127 mm) is created pursuant to Section 1613.4, such separation, at the roof level of the proposed new building, or at the roof level of an existing adjoining building where if that building is lower than the proposed new building, shall have a horizontal cover/closure that conforms with the following:

1. The cover/closure material shall be non-combustible; and

Exception: The cover/closure material used shall be permitted to be combustible material in accordance with Section 1510.9 if all the material on the appropriate roof conforms to the limitations therein, there are no masonry openings in either wall abutting the building separation, and both buildings are non-combustible.

2. The cover/closure shall be capable of withstanding the roof live load of 30 psf (1.43 kPa), securely fastened to the new building, and be of a type that would be capable of preventing unauthorized or accidental access to the space.

1613.5 ASCE 7, Table 12.2-1.

Modify ASCE 7, Table 12.2-1 as follows:

Table 1613.5 Design Coefficient and Factors for Basic Seismic C-Force-Resisting Systems

Seismic Force-Resisting System

ASCE 7 Section Where Detailing Requirements are Specified

Response Modification Coefficient

Over-strength Factor

Deflection Amplification Factor

Structural System Limitations Including Structural Height, h

n

(ft), Limits

c

Seismic Design Category

A. Bearing Wall Systems

—

R

a

S

0

g

C

c

b

B

C

D

d

1. Special reinforced concrete shear walls

l, m

14.2

5

2.5

5

NL

NL

160

2. Ordinary reinforced concrete shear walls

l

14.2

4

2.5

4

NL

NL

NP

3. Detailed plain concrete shear walls

l

14.2

2

2.5

2

NL

NP

NP

4. Ordinary plain concrete shear walls

l

14.2

1.5

2.5

1.5

NL

NP

NP

5. Intermediate precast shear walls

l

14.2

4

2.5

4

NL

NL

40

k

6. Ordinary precast shear walls

l

14.2

3

2.5

3

NL

NP

NP

7. Special reinforced masonry shear walls

14.4

5

2.5

3.5

NL

NL

160

8. Intermediate reinforced masonry shear walls

14.4

3.5

2.5

2.25

NL

NL

NP

9. Ordinary reinforced masonry shear walls

14.4

2

2.5

1.75

NL

160

NP

10. Detailed plain masonry shear walls

14.4

2

2.5

1.75

NL

NP

NP

11. Ordinary plain masonry shear walls

14.4

1.5

2.5

1.25

NL

NP

NP

12. Prestressed masonry shear walls

14.4

1.5

2.5

1.75

NL

NP

NP

13. Ordinary reinforced Autoclaved Aerated Concrete (AAC) masonry shear walls

14.4

2

2.5

2

NL

35

NP

14. Ordinary plain (unreinforced) Autoclaved Aerated Concrete (AAC) masonry shear walls

14.4

1.5

2.5

1.5

NL

NP

NP

15. Light-frame (wood) walls sheathed with wood structural panels rated for shear resistance or steel sheets

14.1 and 14.5

6.5

3

4

NL

NL

65

16. Light-frame (cold-formed steel) walls sheathed with wood structural panels rated for shear resistance or steel sheets

14.1

6.5

3

4

NL

NL

65

17. Light-frame walls with shear panels of all other materials

14.1 and 14.

2

2.5

2

NL

NL

35

18. Light-frame (cold-formed steel) wall systems using flat strap bracing

14.1

4

2

3.5

NL

NL

65

B. Building Frame Systems

—

R

a

S

0

g

C

c

b

B

C

D

d

1. Steel eccentrically braced frames

14.1

8

2

4

NL

NL

160

2. Steel special concentrically braced frames

14.1

6

2

5

NL

NL

160

3. Steel ordinary concentrically braced frames

14.1

3.25

2

3.25

NL

NL

35

j

4. Special reinforced concrete shear walls

l, m

14.2

6

2.5

5

NL

NL

160

5. Ordinary reinforced concrete shear walls

l

14.2

5

2.5

4.5

NL

NL

NP

6. Detailed plain concrete shear walls

l

14.2 and 14.2.2.7

2

2.5

2

NL

NP

NP

7. Ordinary plain concrete shear walls

l

14.2

1.5

2.5

1.5

NL

NP

NP

8. Intermediate precast shear walls

l

14.2

5

2.5

4.5

NL

NL

40

k

9. Ordinary precast shear walls

l

14.2

4

2.5

4

NL

NP

NP

10. Steel and concrete composite eccentrically braced frames

14.3

8

2.5

4

NL

NL

160

11. Steel and concrete composite special concentrically braced frames

14.3

5

2

4.5

NL

NL

160

12. Steel and concrete composite ordinary braced frames

14.3

3

2

3

NL

NL

NP

13. Steel and concrete composite plate shear walls

14.3

6.5

2.5

5.5

NL

NL

160

14. Steel and concrete composite special shear walls

14.3

6

2.5

5

NL

NL

160

15. Steel and concrete composite ordinary shear walls

14.3

5

2.5

4.5

NL

NL

NP

16. Special reinforced masonry shear walls

14.4

5.5

2.5

4

NL

NL

160

17. Intermediate reinforced masonry shear walls

14.4

4

2.5

4

NL

NL

NP

18. Ordinary reinforced masonry shear walls

14.4

2

2.5

2

NL

160

NP

19. Detailed plain masonry shear walls

14.4

2

2.5

2

NL

NP

NP

20. Ordinary plain masonry shear walls

14.4

1.5

2.5

1.25

NL

NP

NP

21. Prestressed masonry shear walls

14.4

1.5

2.5

1.75

NL

NP

NP

22. Light-frame (wood) walls sheathed with wood structural panels rated for shear resistance

14.5

7

2.5

4.5

NL

NL

65

23. Light-frame (cold-formed steel) walls sheathed with wood structural panels rated for shear resistance or steel sheets

14.1

7

2.5

4.5

NL

NL

65

24. Light-frame walls with shear panels of all other materials

14.1 and 14.5

2.5

2.5

2.5

NL

NL

35

25. Steel buckling-restrained braced frames

14.1

8

2.5

5

NL

NL

160

26. Steel special plate shear walls

14.1

7

2

6

NL

NL

160

C. Moment-Resisting Frame Systems

—

R

a

S

0

g

C

c

b

B

C

D

d

1. Steel special moment frames

14.1 and 12.2.5.5

8

3

5.5

NL

NL

NL

2. Steel special truss moment frames

14.1

7

3

5.5

NL

NL

160

3. Steel intermediate moment frames

14.1 and 12.2.5.7

4.5

3

4

NL

NL

35

h

4. Steel ordinary steel moment frames

14.1 and 12.2.5.6

3.5

3

3

NL

NL

NP

i

5. Special reinforced concrete moment frames

n

14.2 and 12.2.5.5

8

3

5.5

NL

NL

NL

6. Intermediate reinforced concrete moment frames

14.2

5

3

4.5

NL

NL

NP

7. Ordinary reinforced concrete moment frames

14.2

3

3

2.5

NL

NP

NP

8. Steel and concrete composite special moment frames

14.3 and 12.2.5.5

8

3

5.5

NL

NL

NL

9. Steel and concrete composite intermediate moment frames

14.3

5

3

4.5

NL

NL

NP

10. Steel and concrete composite partially restrained moment frames

14.3

6

3

5.5

160

160

100

11. Steel and concrete composite ordinary moment frames

14.3

3

3

2.5

NL

NP

NP

12. Cold-formed steel – special bolted moment frame

p

14.1

3.5

3

o

3.5

35

35

35

D. Dual Systems with Special Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic Forces

12.2.5.1

R

a

S

0

g

C

c

b

B

C

D

d

1. Steel eccentrically braced frames

14.1

8

2.5

4

NL

NL

NL

2. Steel special concentrically braced frames

14.1

7

2.5

5.5

NL

NL

NL

3. Special reinforced concrete shear walls

l

14.2

7

2.5

5.5

NL

NL

NL

4. Ordinary reinforced concrete shear walls

l

14.2

6

2.5

5

NL

NL

NP

5. Steel and concrete composite eccentrically braced frames

14.3

8

2.5

4

NL

NL

NL

6. Steel and concrete composite special concentrically braced frames

14.3

6

2.5

5

NL

NL

NL

7. Steel and concrete composite plate shear walls

14.3

7.5

2.5

6

NL

NL

NL

8. Steel and concrete composite special shear walls

14.3

7

2.5

6

NL

NL

NL

9. Steel and concrete composite ordinary shear walls

14.3

6

2.5

5

NL

NL

NP

10. Special reinforced masonry shear walls

14.4

5.5

3

5

NL

NL

NL

11. Intermediate reinforced masonry shear walls

14.4

4

3

3.5

NL

NL

NP

12. Steel buckling-restrained braced frames

14.1

8

2.5

5

NL

NL

NL

13. Steel special plate shear walls

14.1

8

2.5

6.5

NL

NL

NL

E. Dual Systems with Intermediate Moment Frames Capable of Resisting at Least 25% of Prescribed Seismic Forces

12.2.5.1 

R

a

S

0

g

C

c

b

B

C

D

d

1. Steel special concentrically braced frames

f

14.1

6

2.5

5

NL

NL

35

2. Special reinforced concrete shear walls

l

14.2

6.5

2.5

5

NL

NL

160

3. Ordinary reinforced masonry shear walls

14.4

3

3

2.5

NL

160

NP

4. Intermediate reinforced masonry shear walls

14.4

3.5

3

3

NL

NL

NP

5. Steel and concrete composite special concentrically braced frames

14.3

5.5

2.5

4.5

NL

NL

NL

6. Steel and concrete composite ordinary braced frames

14.3

3.5

2.5

3

NL

NL

NP

7. Steel and concrete composite ordinary shear walls

14.3

5

3

4.5

NL

NL

NP

8. Ordinary reinforced concrete shear walls

l

14.2

5.5

2.5

4.5

NL

NL

NP

F. Shear Wall-Frame Interactive System with Ordinary Reinforced Concrete Moment Frames and Ordinary Reinforced Concrete Shear Walls

l

14.2 and 12.2.5.8

4.5

2.5

4

NL

NP

NP

G. Cantilevered Column Systems Detailed to Conform to the Requirements for:

12.2.5.2 

R

a

S

0

g

C

c

b

B

C

D

d

1. Steel special cantilever column systems

14.1

2.5

1.25

2.5

35

35

35

2. Steel ordinary cantilever column systems

14.1

1.25

1.25

1.25

35

35

NP i 

3. Special reinforced concrete moment frames

n

14.2 and 12.2.5.5

2.5

1.25

2.5

35

35

35

4. Intermediate reinforced concrete moment frames

14.2

1.5

1.25

1.5

35

35

NP

5. Ordinary reinforced concrete moment frames

14.2

1

1.25

1

35

NP

NP

6. Timber frames

14.5

1.5

1.5

1.5

35

35

35

H. Steel Systems not Specifically Detailed for Seismic Resistance, Excluding Cantilever Column Systems

14.1

3

3

3

NL

NL

NP

a. Response modification coefficient, R, for use throughout the standard. Note R reduces forces to a strength level, not an allowable stress level.

b. Deflection amplification factor, C

d

, for use in Sections 12.8.6, 12.8.7, and 12.9.1.2 of ASCE 7.

c. NL = Not Limited and NP = Not Permitted. For metric units use 30.5 m for 100 ft and use 48.8 m for 160 ft.

d. See Section 12.2.5.4 of ASCE 7 for a description of seismic force-resisting systems limited to buildings with a structural height, h

n

, of 240 ft (73.2 m) or less.

e. See Section 12.2.5.4 of ASCE 7 for seismic force-resisting systems limited to buildings with a structural height, h

n

, of 160 ft (48.8 m) or less.

f. Ordinary moment frame is permitted to be used in lieu of intermediate moment frame for Seismic Design Categories B or C.

g. Where the tabulated value of the overstrength factor, S

0

, is greater than or equal to 2 1/2, S

0

is permitted to be reduced by subtracting the value of 1/2 for structures with flexible diaphragms.

h. See Section 12.2.5.7 of ASCE 7 for limitations in structures assigned to Seismic Design Category D.

i. See Section 12.2.5.6 of ASCE 7 for limitations in structures assigned to Seismic Design Category D.

j. Steel ordinary concentrically braced frames are permitted in single-story buildings up to a structural height, h

n

, of 60 ft (18.3 m) where the dead load of the roof does not exceed 20 psf (0.96 kN/m

2

) and in penthouse structures.

k. An increase in structural height, h

n

, to 45 ft (13.7 m) is permitted for single story storage warehouse facilities.

l. In Section 2.3 of ACI 318. A shear wall is defined as a structural wall.

m. In Section 2.3 of ACI 318. The definition of "special structural wall" includes precast and cast-in-place construction.

n. In Section 2.3 of ACI 318. The definition of "special moment frame" includes precast and cast-in-place construction.

o. Alternately, the seismic load effect with overstrength, E

mh

, is permitted to be based on the expected strength determined in accordance with AISI S400.

p. Cold-formed steel – special bolted moment frames shall be limited to one-story in height in accordance with AISI S400.

1613.6 Ballasted photovoltaic panel systems.

Ballasted, roof-mounted photovoltaic panel systems need not be rigidly attached to the roof or supporting structure. Ballasted non-penetrating systems shall be designed and installed only on roofs with slopes not more than one unit vertical in 12 units horizontal. Ballasted nonpenetrating systems shall be designed to resist sliding and uplift resulting from lateral and vertical forces as required by Section 1605 of this code, using a coefficient of friction determined by acceptable engineering principles. In structures assigned to Seismic Design Category C or D, ballasted nonpenetrating systems shall be designed to accommodate seismic displacement determined by nonlinear response-history analysis or shake-table testing, using input motions consistent with ASCE 7 lateral and vertical seismic forces for nonstructural components on roofs.