c. Design of building
Note: Many of the calculations in this example were carried out in a spreadsheet format. The calculations carry
more significant digits than are shown in the steps below. Some of the results may be slightly different in the last
digit due to accuracy carried by spreadsheet as compared to the accuracy shown in steps.
The building design follows the steps for Performance Objective 1A set forth in Table 4-5.
A.1 Determine appropriate Seismic Use Group and analysis procedure.
The garage structure is a Standard Occupancy Structure. This classifies it as Seismic Use Group I. The
structural system performance objectives are determined from Table 4-4.
Seismic Use Group:
2/3 MCE (A)
Minimum Analysis Procedure:
Linear Elastic w/ R Factors
A.2 Determine site seismicity.
It is assumed for this problem that we have the values:
SS = 0.75 g
S1 = 0.40 g
A.3 Determine site characteristics.
It is assumed for this problem that we have soil type D
Soil Type: D
A.4 Determine site coefficients.
From Tables 3-2a and 3-2b for the given site seismicity and soil characteristics the site coefficients are:
Fa = 1.2
Fv = 1.6
S MS = Fa SS = (1.2)(0.75g) = 0.90g
S M1 = Fv S1 = (1.6)(0.40g) = 0.64 g
A.6 Determine design spectral response accelerations.
For Performance Objective IA (Protect Life Safety) FEMA 302 requires that the design spectral
accelerations be calculated as 2/3 of the adjusted MCE spectral response accelerations.
S DS = 2 / 3S MS = (2 / 3)(0.90g) = 0.60g
S D1 = 2 / 3S M1 = (2 / 3)(0.64) = 0.43g
For regular structures, 5-stories or less in height, and having a period, T, of 0.5 seconds or less, the design
spectral accelerations need not exceed:
S DS ≤1.5Fa = (1.5)(1.2) = 1.80g > 0.60g
S D1 ≤0.6Fv = (0.6)(1.6) = 0.96g > 0.43g