Civil Engineering Reference
In-Depth Information
Construction of high-rise
building in Berlin, Germany.
(PhotoDisc, Inc./Getty
Images.)
area, and the negative moment regions in the floor girders at the Interior columns are still
underdesigned. Let us address the columns first. To maintain as many similarly sized
columns as possible, and to reduce the amount of steel that must be placed in the columns,
we will use 24
columns for the exterior columns on the two lower floors. To be
compatible with the width of the columns we are now selecting, we will use 18-inch-wide
and 30-inch-deep beams for the floor girders. Again, to be compatible with the columns
and to reduce somewhat the required steel, we will increase the size of the roof girders to
18 inches wide and 24 inches deep. The results of the analysis after this redesign are seen
in Figure 21.8.
These results are acceptable and show that the structure is designed reasonably well.
Additional study could perhaps be done to see if lighter, and therefore more economical,
sections could be used. The final frame is also symmetric, which is consistent with the
load combinations that we used. Recall that we had the wind acting from one side only. If
24
