Design Considerations for Earthquake Forces - Simplified Design of Reinforced Concrete Buildings - page 295

Seismic Response Coefficient:

S D1
R
I

C s =

⎛
⎜

⎞
⎟

T

For building frame system with ordinary shear walls, the modification factor R = 5 Table 11-1 (ASCE
Table 12.2-1). The occupancy importance factor I = 1 (ASCE 11.5).

0.19
5
1

C s =

0.45 =

0.083

⎛ ⎞

⎜ ⎟

C s should not be taken less than:

C s = 0.01

C s need not exceed:

S DS
R
I

0.28
5
1

C s = = = 0.055

⎛
⎜

⎞
⎟

⎛ ⎞

⎜ ⎟

Use C s = 0.055

Effective Seismic Weight

The effective seismic weight for this case includes the total dead load and the partition weight. The effective
seismic loads for different floors are calculated as follows:

For the first floor:

Slab = (121 ft)(61 ft)(0.142 ksf) =1048 kips

Interior columns (8 columns) = 8 (1.33 ft)(1.33 ft)(13.5 ft)(0.15 kcf) = 28.7 kips

Exterior columns (12 columns) = 12(1 ft)(1 ft)(13.5 ft)(0.15 kcf) = 24.3 kips

Walls = 2[(20.66 ft)(0.66 ft)+2(7.33 ft)(0.66 ft)](13.5 ft)(0.15 kcf) = 94.4 kips

Effective seismic weight (1st floor) = 1048 + 28.7 + 24.3 + 94.4 = 1195 kips

For second to fourth floor:

Slab = (121 ft)(61 ft)(0.142 ksf) =1048 kips

Interior columns (8 columns) = 8 (1.33 ft)(1.33 ft)(12 ft)(0.15 kcf) = 25.5 kips

Exterior columns (12 columns) = 12(1 ft)(1 ft)(12 ft)(0.15 kcf) = 21.6 kips

Walls = 2[(20.66 ft)(0.66 ft)+2(7.33 ft)(0.66 ft)](12 ft)(0.15 kcf) = 83.9 kips

Effective seismic weight = 1048 + 25.5 + 21.6 + 83.9 = 1179 kips