Simplified Design for Columns - Simplified Design of Reinforced Concrete Buildings - page 172

Live load moment = 0.035 q Lu ˜ 2 ˜ n 2

= 0.035(0.05)(24)(18.83 2 ) = 14.9 ft-kips ACI Eq. (13.4)

⎡
⎢

12

⎤
⎥

Portion of live load moment to first story column = 14.9 = 6.6 ft-kip

12 + 15

(2) LOAD COMBINATIONS

For the 1st story column:

gravity loads: P u = 487 kips ACI Eq. (9-2)

M u = 1.6(6.6) = 10.6 ft-kips

gravity loads + wind loads: P u = 1.2(340) + 1.6 (9.6) = 423 kips ACI Eq. (9-3)

M u = 1.6(6.6) + 0.8(68.75) = 65.6 ft-kips

or

P u = 1.2(340) + 0.5(56.4) = 436 kips ACI Eq. (9-4)

M u = 0.50(6.6) + 1.6(68.75) = 113 ft-kips

or

P u = 0.9(340) = 306 kips ACI Eq. (9-6)

M u = 1.6(68.75) = 110 ft-kips

Factored loads and moments, and load combinations, for the 2nd through 5th story columns are calculated in
a similar manner, and are summarized in Table 5-6.

Table 5-6 Interior Column Load Summary for Building #2, Alternate (1)

Floor ACI Eq. (9-2) ACI Eq. (9-3) ACI Eq. (9-4) ACI Eq. (9-6)

P u M u P u M u P u M u P u M u

5th (roof) 80 10 90 15 80 13 56 10

4th 186 12 174 25 170 34 119 30

3rd 288 12 257 34 259 54 181 50

2nd 388 13 340 44 348 73 243 68

1st 487 11 423 65 436 113 306 110