When K factors other than 1 are used (either directly, or indirectly by setting the slab or beam Behavior), it is possible that the structure may become unstable or nearly unstable. This is generally not a problem unless the Custom option is used.

Interaction of KMrs and KMr or KMs Stiffness Factors

If custom settings are used, and both KMrs and KMr or both KMrs and KMs are reduced, the elements may become unstable and the analysis results may be suspect. For this reason we recommend that these parameters be kept within a limited range:

• KMr / KMs ≥ 0.5 or KMrs / KMs ≥ 0.5
• KMs / KMr ≥ 0.5 or KMrs / KMr ≥ 0.5

Similar instabilities can occur with KVrs and KFr/KFs.