Load Nonsway Frames

The architect decided to remove two beams from the second floor of this normal weight concrete building to create a double volume as shown. The beams removed $($D$3$ to C$3$ and D$4$ to C$4)$ are clouded.

Dimensions for all beams and columns are $12$ in $12$ in and concrete compressive strength is $f_c^{\text{'}}=3,500.$

Clear distance between floors:

First floor $14$ ft

Second floor $12$ ft

End moments for exterior columns are almost equivalent, and those exterior columns are bent in single curvature.

Reduction in the critical buckling load as applied from the roof due to this change in kip for column D$4$ is most nearly:

$($A$)470$

$($B$)130$

$($C$)320$

$($D$)600$

First floor and roof