LEAP Concrete Substructure - P Delta vs Moment Magnification

Question

Per AASHTO LRFD code requirements unintended eccentricity is handle by the reduction factors 0.85 (spiral) and 0.80 (tied). The program however ignores this requirement and goes back to the old ASD code practice of increasing the moments by considering a minimum eccentricity. Why is this done and how is it acceptable?

Vinay mysore · Answer

In LEAP, the reduction factors 0.85 (spiral) and 0.80 (tied) are considered to place the cap on the usable of the column for unintended eccentricity. On the other hand, the min eccentricity is still being used in the column design. Typically, the moment due to the min eccentricity is triggered in the biaxial bending analysis. However, if the min eccentricity is triggered, it usually generates slightly more conservative in column design. Hope this clarifies.