Problem Description

The program designed concrete columns for an incorrect shear demand (Vu) when all of the following conditions occurred:

1. The columns spanned multiple stories.
2. The columns were not braced by beams at the intermediate levels.
3. The columns were part of a intermediate or special moment frame.

The problem affected all ACI design codes.

Reason

Columns that are part of intermediate or special moment frames must be designed for a shear demand associated with probable flexural strength (Mpr). When determining Mpr, the program looked at the top and bottom of each column segment and did not consider the bracing condition at each end of the segment. When one end of the segment was not braced, as would occur when no beam frame into the column, the program returned a value of 0 for Mpr.

Solution

We are working on a fix for this problem.