Columns. Occasionally, there are greater axial forces in higher spans than in lower spans

Bear in mind that when the forces of a column are consulted on screen (using the Columns > Edit option in the Column Definition tab), the worst case forces are those that are displayed.

The worst case forces are the most unfavourable forces for a column, the ones which provide the most reinforcement, in accordance to the code which arise from the simple loadcase combinations.So, it may occur that the most unfavourable combination for a lower span is one whose axial force is smaller than that of a higher span, but on the other hand, has greater moments, resulting in the worst case for that column.

It may also occur that the axial force is identical to that of the span directly above it. The program calculates the forces for each column at the bottom and top of its span, and bottom of the span above it (as in this section, the reinforcement that is resisting the forces, is that belonging to the lower span, i.e. the anchorage reinforcement or splice reinforcement).

In the case of the higher span, its worst case forces can be at its base. Consequently, the axial forces for both column spans are the same. All that has been explained can be checked in the Forces of columns report within the Job reports option. Using this report, it can be seen that the axial forces gradually increase as one moves down floors. These forces are expressed in simple loadcases. If all the combinations stated in the code are carried out manually, it can be seen that the worst case combination is that used and applied as the worst case combination in the program, which provides the same or greater reinforcement with respect to that used in the span below.

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