Site Class

1 Second Period Maximum Considered Response Spectral

Acceleration

S1 ≤ 0.1

S1 ≥ 0.5

S1 = 0.2

S1 = 0.3

S1 = 0.4

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

a6

E

3.5

3.2

2.8

2.4

F

a

a

a

a

a

second, SM1 adjusted for site class effects are calculated as follows (FEMA 302, Eq. 4.1.2.4-1 and

4.1.2.4-2):

SMS = Fa S S

(Eq C-1)

and

SM1 = Fv S1

(Eq C-2)

These values define the elastic spectra. These values are reduced to define design earthquake spectral

4.1.2.5-1 and 4.1.2.5-2):

2

SDS =

SMS

(Eq C-3)

3

and

2

SD1 =

SM1

(Eq C-4)

3

From these terms a design response spectrum is developed as indicated in Figure C-1 (FEMA 302,

Figure 4.1.2.6). For the natural period of the structure, T this spectrum defines values of effective

acceleration. The three regions of this spectrum are defined as follows:

SDS

Sa=SD1/T

SD1

Ts

To

1.0

Period T

5

6

a indicates that a site-specific geotechnical investigation and dynamic site response analyses shall be performed.

C-2

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