# Nonlinear Static Analysis

There are several different types of nonlinear analysis, but there are two different effects that need to be considered.

**Geometric nonlinearity**– 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 nonlinearity**– where the loading causes material to behave in a nonlinear manner, typically through yielding.

Different analysis options in GSA allow these effects to be accounted for in different ways.

The simplest geometrically nonlinear 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 nonlinearity problem is static analysis with ties and struts. In this case the material can take either no compression or no tension.

More general nonlinear static analysis will model both geometrical and material nonlinear effects. Nonlinear data types are made available in the data tables. The options given are the basic Nonlinear static analysis and Fabric analysis. Once a nonlinear analysis preference has been set and the model defined it can be analysed with a nonlinear analysis solver.

There are two analysis solvers for nonlinear 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 nonlinear static analysis

Nonlinear static analysis of ties and struts