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

The parameters

*S*and_{S}*S*_{1}shall be determined from the 0.2 and 1-second spectral response accelerations shown on Figures 1613.3.1(1) through 1613.3.1(8). Where*S*_{1}is less than or equal to 0.04 and*S*is less than or equal to 0.15, the structure is permitted to be assigned_{S}*Seismic Design Category*A.**FIGURE 1613.3.1(1) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 0.2-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B*(continued)***FIGURE 1613.3.1(1)‒continued RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 0.2-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(2) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B*(continued)***FIGURE 1613.3.1(2)‒continued RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR THE CONTERMINOUS UNITED STATES OF 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(3) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR HAWAII OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(4) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR ALASKA OF 0.2-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(5) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR ALASKA OF 1.0-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(6) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR PUERTO RICO AND THE UNITED STATES VIRGIN ISLANDS OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(7) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR GUAM AND THE NORTHERN MARIANA ISLANDS OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS B**FIGURE 1613.3.1(8) RISK-TARGETED MAXIMUM CONSIDERED EARTHQUAKE (MCE**_{R}) GROUND MOTION RESPONSE ACCELERATIONS FOR AMERICAN SAMOA OF 0.2- AND 1-SECOND SPECTRAL RESPONSE ACCELERATION (5% OF CRITICAL DAMPING), SITE CLASS BBased on the site soil properties, the site shall be classified as

Where the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the building official or geotechnical data determines Site Class E or F soils are present at the site.

*Site Class*A, B, C, D, E or F in accordance with Chapter 20 of ASCE 7.Where the soil properties are not known in sufficient detail to determine the site class, Site Class D shall be used unless the building official or geotechnical data determines Site Class E or F soils are present at the site.

The maximum considered earthquake spectral response acceleration for short periods,

where:

*S*, and at 1-second period,_{MS}*S*, adjusted for_{M1}*site class*effects shall be determined by Equations 16-37 and 16-38, respectively: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 spectral accelerations for short periods as determined in Section 1613.3.1. |

S_{1} | = | The mapped spectral accelerations for a 1-second period as determined in Section 1613.3.1. |

**TABLE 1613.3.3(1) VALUES OF SITE COEFFICIENT***F*_{a }^{a} SITE CLASS | MAPPED SPECTRAL RESPONSE ACCELERATION AT SHORT PERIOD | ||||

≤ S_{s}0.25 | S = 0.50_{s} | S = 0.75_{s} | S = 1.00_{s} | ≥S_{s} 1.25 | |

A | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 |

B | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |

C | 1.2 | 1.2 | 1.1 | 1.0 | 1.0 |

D | 1.6 | 1.4 | 1.2 | 1.1 | 1.0 |

E | 2.5 | 1.7 | 1.2 | 0.9 | 0.9 |

F | Note b | Note b | Note b | Note b | Note b |

a. Use straight-line interpolation for intermediate values of mapped spectral response acceleration at short period, S._{s} |

b. Values shall be determined in accordance with Section 11.4.7 of ASCE 7. |

**TABLE 1613.3.3(2) VALUES OF SITE COEFFICIENT***F*_{V}^{a} SITE CLASS | MAPPED SPECTRAL RESPONSE ACCELERATION AT 1-SECOND PERIOD | ||||

≤S_{1} 0.1 | S_{1} = 0.2 | S_{1} = 0.3 | S_{1} = 0.4 | ≥ S_{1}0.5 | |

A | 0.8 | 0.8 | 0.8 | 0.8 | 0.8 |

B | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |

C | 1.7 | 1.6 | 1.5 | 1.4 | 1.3 |

D | 2.4 | 2.0 | 1.8 | 1.6 | 1.5 |

E | 3.5 | 3.2 | 2.8 | 2.4 | 2.4 |

F | Note b | Note b | Note b | Note b | Note b |

a. Use straight-line interpolation for intermediate values of mapped spectral response acceleration at 1-second period, S_{1}. |

b. Values shall be determined in accordance with Section 11.4.7 of ASCE 7. |

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

where:

*S*and at 1-second period,_{DS},*S*, shall be determined from Equations 16-39 and 16-40, respectively:_{D1}where:

S_{MS} | = | The maximum considered earthquake spectral response accelerations for short period as determined in Section 1613.3.3. |

S_{M1} | = | The maximum considered earthquake spectral response accelerations for 1-second period as determined in Section 1613.3.3. |

Structures classified as

*Risk Category*I, II or III that are located where the mapped spectral response acceleration parameter at 1-second period,*S*, is greater than or equal to 0.75 shall be assigned to_{1}*Seismic Design Category*E. Structures classified as*Risk Category*IV that are located where the mapped spectral response acceleration parameter at 1-second period,*S*is greater than or equal to 0.75 shall be assigned to_{1},*Seismic Design Category*F. All other structures shall be assigned to a*seismic design category*based on their*risk category*and the design spectral response acceleration parameters,*S*and_{DS}*S*, determined in accordance with Section 1613.3.4 or the site-specific procedures of ASCE 7. Each building and structure shall be assigned to the more severe_{D1}*seismic design category*in accordance with Table 1613.3.5(1) or 1613.3.5(2), irrespective of the fundamental period of vibration of the structure,*T*.**TABLE 1613.3.5(1) SEISMIC DESIGN CATEGORY BASED ON SHORT-PERIOD (0.2 second) RESPONSE ACCELERATION** VALUE OF S_{DS} | RISK CATEGORY | ||

I or II | III | IV | |

S < 0.167g_{DS} | A | A | A |

0.167g ≤ S < 0.33g _{DS} | B | B | C |

0.33g ≤ S < 0.50g _{DS} | C | C | D |

0.50g ≤ S_{DS} | D | D | D |

**TABLE 1613.3.5(2) SEISMIC DESIGN CATEGORY BASED ON 1-SECOND PERIOD RESPONSE ACCELERATION** VALUE OF S_{D1} | RISK CATEGORY | ||

I or II | III | IV | |

S < 0.067g_{D1} | A | A | A |

0.067g ≤ S < 0.133g_{D1} | B | B | C |

0.133g ≤ S < 0.20g_{D1} | C | C | D |

0.20g ≤ S_{D1} | D | D | D |

Where

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

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

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

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).

*S*is less than 0.75, the_{1}*seismic design category*is permitted to be determined from Table 1613.3.5(1) alone when all of the following apply:1. In each of the two orthogonal directions, the approximate fundamental period of the structure,

*T*, in each of the two orthogonal directions determined in accordance with Section 12.8.2.1 of ASCE 7, is less than 0.8_{a}*T*determined in accordance with Section 11.4.5 of ASCE 7._{s}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).

Where the alternate simplified design procedure of ASCE 7 is used, the

*seismic design category*shall be determined in accordance with ASCE 7.