# Analysis of Fabric Structures
Fabric structures rely on deflection and prestress to achieve equilibrium. Also fabric material is orthotropic with distinct warp and weft properties. The non-linear solver offers features to deal with both of these issues.
# Modelling implications
Proceed in the same way as for a non-linear static analysis using Quad 4 and Tri 3 element types to define fabric elements. The initial geometry of the fabric surface is a function of the stress in the fabric and the support geometry. To define the geometry prior to analysing the fabric structure, a Form-Finding Analysis can be performed. This is the most likely method of defining a fabric model.
Enter the Fabric Material properties in the fabric materials table. The warp direction will be aligned with the element x axis of each 2D element. It is worth considering this before starting to input fabric elements.
Then open the 2D element properties table. Set the property type to Fabric. Type the Fabric Material property record number to assign the Material.
2D element prestress loading defines the prestress in warp and weft (element x and y) directions. Alternatively the element prestress data (for membrane and 1D elements) will be generated during a Form-Finding analysis.
Spacer elements will probably have been used in a Form-Finding analysis to generate the model. These elements and associated prestress loading should be deleted prior to analysis as a real fabric structure.
# Analysis and results
Once the structural model is defined, the analysis is set-up using the Analysis Wizard as described for the basic Non-Linear static analysis. The “Non-linear static” solver option should be selected in the Analysis Wizard. The GSS solver cannot analyse 2D elements with Fabric Properties and is not appropriate for the large deflection behaviour of these structures. The Wizard then prompts for the data to define the analysis.
Fabric analysis is the same as Non-linear analysis except that fabric elements are enabled. Therefore the same analysis options apply.