HW#9-2 A W 14 x 82 of A992 steel, 16 feet long, is used as a column in an unbrac

Question

HW#9-2 A W 14 x 82 of A992 steel, 16 feet long, is used as a column in an unbraced frame The axial load and end moments obtained from a first-order analysis of the gravity loads (dead and live loads) are shown. The frame is symmetric, and the gravity loads are symmetrically placed. The figure below shows the wind load effects obtained from a first-order analysis. All loads and moments are based on service loads, and all bending moments are about the strong axis. The effective length factors are K 0.85 for the braced case, K 1.2 for the unbraced case, and K,1.0. Determine whether this member is in compliance with the AISC specification. P-120P 240 30 D=15 ft.k 130- 16 D=18 ft.k 130 (a) Gravity b) Wind

Explanation / Answer

from gravity load combination 1.2DL+1.6LL

Pu=(1.2*120)+(1.6*240)=528 kips

Mu=(1.2*18)+(1.6*48)=98.4 kip-ft

From lateral load combination 1.2DL+LL+WL

Pu = (1.2*120)+240+30=414 kips

Mu = (1.2*18)+48+130=199.6 kip-ft

Effective length of column = 16'

axial load capacity of beam = 697 kips from Table 4-1

moment capapcity of beam for unbraced length of 16' = 521-[(521-323)/(33.2-8.76)]*(16-8.76)=462.3 kip-ft

interaction check for gravity load combination :

(528/697)+(8/9)*(98.4/462.3)=0.95

inmtercation check for gravity combination :

(414/697)+(8/9)*(199.6/462.3)= 0.98

The section is in compliance with AISC specification

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