Design Response Spectrum to ASCE 7

ASCE 7-16﻿
Design Response Spectrum to ASCE 7-16
Risk-Targeted Maximum Considered Earthquake ﻿(MCER​)
 Spectral Response Acceleration Parameters 
The spectral response acceleration parameters for the ﻿MCER​
 (maximum considered earthquake) for short periods (﻿SMS​
) and at 1 second (﻿SM1​
), adjusted for site class effects, will be determined using the following equations:
﻿
SMS=FaSSSM1=FvS1S_{MS} = F_a S_S  \quad \quad S_{M1} = F_v S_1SMS​=Fa​SS​SM1​=Fv​S1​
where site coefficients ﻿Fa​
 and ﻿Fv​
are defined in Tables 11.4-1 and 11.4-2, respectively
Note: Electronic values of mapped acceleration parameters and other seismic design parameters are provided at the U.S. Geological Survey (USGS) website
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 ASCE 7-16, Chapter 20.
﻿
ASCE/SEI 7-16 Minimum Design Loads and Associated Criteria forBuildings and Other Structures
﻿
ASCE/SEI 7-16 Minimum Design Loads and Associated Criteria forBuildings and Other Structures
﻿
ASCE 7-22﻿
Two-Period Design Response Spectrum to ASCE 7-22
Risk-Targeted Maximum Considered Earthquake ﻿(MCER​)
 Spectral Response Acceleration Parameters 
Risk-targeted maximum considered earthquake ﻿(MCER​)
 spectral response acceleration parameters ﻿SS​
, ﻿S1​
, ﻿SMS​
, and ﻿SM1​
 shall be obtained from the USGS Seismic Design Geodatabase for the applicable site class.
Site Class The site shall be classified as Site Class ﻿A
, ﻿B
, ﻿BC
, ﻿C
, ﻿CD
, ﻿D
, ﻿DE
, ﻿E
, or ﻿F
 in accordance with ASCE 7-22, Chapter 20
 
﻿
Note: In the ASCE 7-22, the "Short-Period Site Coefficient" and the "Long-Period Site Coefficient for a 1.0-second period" are now derived from the USGS Seismic Design Geodatabase. This marks a significant change from the ASCE 7-16, where these coefficients were extracted from tables that often required interpolation. The shift to using the USGS database in ASCE 7-22 streamlines the process by providing direct, location-specific values, enhancing accuracy and reducing the manual steps needed in seismic design calculations.
﻿
Risk-Targeted Maximum Considered Earthquake ﻿(MCER​)
 Response Spectrum 
Where an ﻿MCER​
 Response Spectrum is required, it shall be determined by multiplying the Design Response Spectrum by 1.5.
Design Spectral Acceleration Parameters. 
The spectral response acceleration parameters for earthquakes at short periods, ﻿SDS​
, and at 1 second periods, ﻿SD1​
, will be determined using the following equations:
﻿
SDS=23SMSS_{DS} = \frac{2}{3} S_{MS} \quad \quad SDS​=32​SMS​
﻿
SD1=23SM1S_{D1} = \frac{2}{3} S_{M1}SD1​=32​SM1​
﻿﻿SMS​
: ﻿MCER​
, 5%-damped, spectral response acceleration parameter at short periods adjusted for site 
﻿﻿SM1​
: ﻿MCER​
, 5%-damped, spectral response acceleration parameter at a period of 1 s adjusted for site effects
To plot the design response spectrum, it is necessary to know the parameters that shape the spectrum using the following expressions:

﻿
TO=0.2(SD1SDS)TS=SD1SDST_O = 0.2 \left( \frac{S_{D1}}{S_{DS}} \right) \quad \quad T_S = \frac{S_{D1}}{S_{DS}}TO​=0.2(SDS​SD1​​)TS​=SDS​SD1​​
Where ﻿Sa​
 is the design spectral response acceleration, and ﻿T
 is the fundamental period of the structure.
For periods shorter than ﻿TO​
:
﻿
Sa=SDS(0.4+0.6TTO)S_a = S_{DS} \left( 0.4+0.6 \frac{T}{T_O} \right)Sa​=SDS​(0.4+0.6TO​T​)
For periods greater than or equal to ﻿TO​
 and less than or equal to ﻿TS​
:
﻿
Sa=SDSS_a = S_{DS}Sa​=SDS​
For periods greater than ﻿TS​
 and less than or equal to ﻿TL​
:
﻿
Sa=SD1TS_a = \frac{S_{D1}}{T}Sa​=TSD1​​
For periods greater than ﻿TL​
:
﻿
Sa=SD1TLT2S_a = \frac{S_{D1}T_L}{T^2}Sa​=T2SD1​TL​​
﻿
 Design Response Spectrum (ASCE 7-16)
Two-period Design Response Spectrum (ASCE 7-22) 
ReferenceASCE 7-16: Minimum Design Loads and Associated Criteria for Buildings and Other Structures - Chapter 11: Seismic Design Criteria.
ASCE 7-22: Minimum Design Loads and Associated Criteria for Buildings and Other Structures - Chapter 11: Seismic Design Criteria.
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