When defining or calculating a result combination, I get the message that the addition is not allowed due to failing members. What does this message mean?
For example, it can happen that a tension member of a system is subjected to compression in a load case and therefore fails. The results of this failed member are indicated as zero in this load case. In another load case, the tension member can indeed be under tension, thus removing the member from the system.
Now if the results of these two load cases are added by means of the result combination, the results are summed up from two different structural systems. When using nonlinear elements (for example member with failure due to compression), the load combination should be used.
If you are not sure that the individual load cases are based on the same structural systems, you can also use the result combination.