# Nonlinear Static Analysis : Ties and Struts
Analysis of structures with ties and struts is the simplest non-linear option. No special action is required by the user to activate this option as it depends only on the types of elements in the model.
The effect of the geometric stiffness can be included by selecting a static P-delta analysis rather than a static analysis.
# Modelling implications of ties and struts
The following elements cause a solution to be non-linear:
- Tie – tension only elements that otherwise resemble bars.
- Strut – compression only elements that otherwise resemble bars.
- Cables – similar to tie element but the properties are specified differently.
Non-linear behaviour is only appropriate for a static analysis and cannot be incorporated into a modal analysis (dynamics or buckling). In these cases these elements behave as bars.
# Non-linear static analysis
The analysis of ties and struts uses an iterative solution technique, which means that each load case has to be considered separately. The number of iterations required for convergence of each task is shown in the report view.
If the solution fails to converge or the results are insufficiently accurate (for example as indicated by a large residual in the Total Loads and Reactions) then you can adjust the number of iterations and the convergence tolerance in the
# Results of non-linear static analysis
The same set of results is available from a non-linear static analysis as for a linear static analysis. However in this case superposition of results is not valid. Details of results available and how they can be viewed are in the Results Display Options section.