Section 1613A

EARTHQUAKE LOADS

1613 A .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 Chapters 11, 12, 13, 15, 17 and 18 of ASCE 7, as applicable. The seismic design category for a structure shall be determined in accordance with Section 1613 A .

1613 A .2 Seismic ground motion values. Seismic ground motion values shall be determined in accordance with this section.

1613 A .2.1 Mapped acceleration parameters. The parameters SS and S 1 shall be determined from the 0.2 and 1-second spectral response accelerations shown on Figures 1613.2.1(1) through 1613.2.1(10).

1613 A .2.2 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.

Where the soil properties are not known in sufficient detail to determine the site class, Site Class D, subjected to the requirements of Section 1613 A .2.3, shall be used unless the building official or geotechnical data determines that Site Class E or F soils are present at the site.

Where site investigations that are 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 Fa and Fv shall be taken at unity (1.0).

1613 A .2.3 Site coefficients and adjusted maximum considered earthquake spectral response acceleration parameters. The maximum considered earthquake spectral response acceleration for short periods, SMS, and at 1second period, SM1, adjusted for site class effects shall be determined by Equations 16 A -20 and 16-21, respectively:

SMS = FaSS (Equation 16 A -20)

SM1 = Fv S 1 (Equation 16 A -21)

but SMS shall not be taken less than SM1 except when determining the seismic design category in accordance with Section 1613 A .2.5.

where:

Fa = Site coefficient defined in Table 1613 A .2.3(1). Fv = Site coefficient defined in Table 1613 A .2.3(2). SS = The mapped spectral accelerations for short periods

as determined in Section 1613 A .2.1. S 1 = The mapped spectral accelerations for a 1-second

period as determined in Section 1613 A .2.1. Where Site Class D is selected as the default site class per Section 1613 A .2.2, the value of Fa shall be not less than 1.2.

SDS

SD1

(Equation 16 A -22)

(Equation 16 A -23)

where:

SMS = The maximum considered earthquake spectral

response accelerations for short period as determined in Section 1613 A .2.3.

SM1 = The maximum considered earthquake spectral

response accelerations for 1-second period as determined in Section 1613 A .2.3.

1613 A .2.5 Determination of seismic design category. Structures classified as Risk Category I, II or III that are located where the mapped spectral response acceleration parameter at 1-second period, S1, is greater than or equal to 0.75 shall be assigned to 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 1, is greater than or equal to 0.75 shall be assigned to Seismic Design Category F. Other structures shall be assigned to Seismic Design Category D.

1613 A .2.5.1 Alternative seismic design category determination. Not permitted by DSA-SS and OSHPD.

1613 A .2.5.2 Simplified design procedure. Not permit- ted by DSA-SS and OSHPD.

1613 A .3 Ballasted photovoltaic panel systems. Ballasted, roof-mounted photovoltaic panel systems need not be rigidly attached to the roof or supporting structure.

[DSA-SS] Ballasted, roof-mounted photovoltaic panel sys- tems shall comply with ASCE 7 13.6.12.

[OSHPD 1 & 4] Ballasted photovoltaic panel systems shall be considered as an alternative system.