# Nonlinear Static Analysis
There are several different types of non-linear analysis, but there are two different effects that need to be considered.
- Geometric non-linearity – where the loading causes changes in the shape of the structure which must be taken into account in order to get an accurate solution.
- Material non-linearity – where the loading causes material to behave in a non-linear manner, typically through yielding.
Different analysis options in GSA allow these effects to be accounted for in different ways.
The simplest geometrically non-linear problem is a static P-delta analysis. This takes account of the fact that displacements in the structure can be either beneficial or detrimental to its performance.
The simplest material non-linearity problem is static analysis with ties and struts. In this case the material can take either no compression or no tension.
More general non-linear static analysis will model both geometrical and material non-linear effects. Non-linear data types are made available in the data tables. The options given are the basic Non-linear static analysis and Fabric analysis. Once a non-linear analysis preference has been set and the model defined it can be analysed with a non-linear analysis solver.
There are two analysis solvers for non-linear analysis. One is called GsRelax and is based on Dynamic Relaxation, the other is an explicit solver. The GsRelax solver takes a completely different approach to the GSS solver. Because of this some data items function differently with the GSS and GsRelax solvers. Other data items are only appropriate for use with a specific solver option. The data affected is mentioned briefly below and is covered in detail in the relevant data definition sections.
# More:
Modelling implications of non-linear static analysis
Non-linear static analysis of ties and struts