Non-linear combination used as a load case in a linear combination

This feature is only available in 32-bit version using old Post Processing Environment with Sequential analysis functionality activated.

When a linear combination of load cases is being defined, it is possible to add also results of an already calculated non-linear combination of load cases. Such a non-linear combination behaves as a permanent load case in further calculations.

This feature makes it possible to combine e.g. wind or seismic effects (linear calculation) with a non-linear calculation that solves e.g. the effect of the self-weight on an inclined (imperfect) structure. The solution is not perfect, but it significantly reduces the number of required non-linear combinations.

There is no coefficient for this added non-linear combination as principle of superposition does not apply to non-linear calculations.

It is necessary to think carefully about the use of this feature. If for example, the nonlinear model contains members acting in tension only, they are eliminated in the non-linear calculation (if they get under compression), but they remain and act in the model during the subsequent linear calculation.

Note: If the added non-linear combination has not been calculated yet, it is treated as an empty load case, i.e. nothing is added. No special warning is issued about this. The user must make sure that non-linear calculation has been performed prior to the linear calculation in which linear combinations with added non-linear combinations are treated.