This question is problem 8.3 from Chapter 8 of "Structural Stability of Steel: Concepts and Applications for Structural Engineers Theodore V. Galambos Andrea E. Surovek" 

The frame shown represents an 11-bay frame in which all but the two center columns are pinned. The applied force 4P on the exterior columns represents four bays of gravity load. 

Assess the adequacy of the W10 X 49 column in the frame shown using

a. the second-order method using the NT-LT approach

b. the second-order method using a direct second-order analysis

c. the direct analysis approach

Compare results of the internal forces and moments from the three approaches and discuss how these affect the strength check using the interaction equation.

W- 4P k W27 x 84 DL = 80 psf LL = 40 psf Wind = 20 psf Fy = 50 ksi Frame spacing = 35' W27 x 49 3 @ 35 105 = Fig. p8.3 Load combinations: 1.2D + 1.6L 1.2D + 0.5L + 1.3W 4P 18