- 2 3 Deliverable Graph The Design Response Spectrum For The Project Site And Conditions After Asce 7 16 Figure 11 4 1 U 1 (40.37 KiB) Viewed 54 times
11.4.3 Site Class. 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. Where the soil properties are not known in sufficient detail to determine the site class, Site Class D, subject to the requirements of Section 11.4.4, shall be used unless the authority having jurisdiction or geotechnical data determine that Site Class E or F soils are present at the site. For situations in which site investigations, performed in accor- dance with Chapter 20, reveal rock conditions consistent with Site Class B, but site-specific velocity measurements are not made, the site coefficients Fa, Fy, and FPGA shall be taken as unity (1.0). 11.4.4 Site Coefficients and Risk-Targeted Maximum Considered Earthquake (MCER) Spectral Response Acceleration Parameters. The MCER spectral response acceleration parameters for short periods (SMS) and at 1 s (SMI), adjusted for site class effects, shall be determined by Eqs. (11.4-1) and (11.4-2), respectively. SMS=FgSs SM1=FvS₁ where Ss = the mapped MCER spectral response acceleration parameter at short periods as determined in accordance with Section 11.4.2, and S₁ = the mapped MCER spectral response acceleration parameter at a period of 1 s as determined in accordance with Section 11.4.2 (11.4-1) (11.4-2) where site coefficients F and F, are defined in Tables 11.4-1 and 11.4-2, respectively. Where Site Class D is selected as the default site class per Section 11.4.3, the value of F, shall not be less than 1.2. Where the simplified design procedure of Section 12.14 is used, the value of Fa shall be determined in accordance with Section 12.14.8.1, and the values for F, SMS, and SMI need not be determined. Site Class Table 11.4-1 Short-Period Site Coefficient, Fa Mapped Risk-Targeted Maximum Considered Earthquake (MCE) Spectral Response Acceleration Parameter at Short Period Sg ≤ 0.25 Ss=0.5 Sg=0.75 Sg=1.0 Sg=1.25 Sg 2 1.5 B C D E F Spectral Response Acceleration, Sa (g) Sps 0.8 0.8 1.5 2.4 4.2 SDI See Section 11.4.8 0.8 0.8 0.8 0.8 1.5 1.5 1.5 1.5 2.2" 2.0⁰ 1.9⁰ 1.8" See See See Section Section See Section Section 11.4.8 11.4.8 11.4.8 11.4.8 See See See See Section Section Section Section 11.4.8 11.4.8 11.4.8 11.4.8 0.8 0.8 Note: Use straight-line interpolation for intermediate values of S₁. "Also, see requirements for site-specific ground motions in Section 11.4.8. 0.8 0.8 S₁= 0.8 0.8 1.4 1.7⁰ See Section 11.4.8 See Section 11.4.8 S, =Sor Ti 1.0 Period, 7 (sec) FIGURE 11.4-1 Design Response Spectrum 11.4.5 Design Spectral Acceleration Parameters. Design earthquake spectral response acceleration parameters at short periods, Sps, and at 1-s periods, Spi, shall be determined from Eqs. (11.4-3) and (11.4-4), respectively. Where the alternate simplified design procedure of Section 12.14 is used, the value of Sps shall be determined in accordance with Section 12.14.8.1, and the value for Sp₁ need not be determined. SDS=SMS SDI = SMI (11.4-3) (11.4-4)
2. For periods greater than or equal to To and less than or equal to Ts, the design spectral response acceleration, Sa, shall be taken as equal to Sps. 3. For periods greater than Ts and less than or equal to TL, the design spectral response acceleration, Sa, shall be taken as given in Eq. (11.4-6): (11.4-6) 4. For periods greater than TL, Sa shall be taken as given in Eq. (11.4-7): SD1 T Sa To=0.2(SD1/SDS) Ts=SD/SDs, and SDITL T² (11.4-7) where SDs = the design spectral response acceleration parameter at short periods SD1 = the design spectral response acceleration parameter at a 1-s period T = the fundamental period of the structure, s T₁ = long-period transition period(s) shown in Figs. 22-14 through 22-17.