FAQ 002339 EN-US 12/01/2017

General

Which shape functions does RFEM 5 use for 1.) volume elements and 2.) shell elements? Are they linear or quadratic shape functions?

Answer

Generally we use identical bilinear approach functions with 2, 3 or 4 edge nodes depending on which element you use but there are differences in the quadrature. The differences in squaring are as follows:

Elastic calculation:

 

Fachwerkstab: analytically 2 knots 3 degrees of freedom
Bar: analytically 2 knots 6 degrees of freedom
Surface (plate): analytic (LYNN-DYLON element)

Area (wall): quadrilateral Gauss quadrature 2x2, 3-edged selective quadrature (epsilon_x; epsilon_y; gamma_xy)
Volume: Gauss quadrature 2x2

 

Non-linear calculation (eg plasticity etc.):

 

Bar:

in the longitudinal direction of the rod 2-point Gauss quadrature

across the cross section 2x2 Gauss quadrature


Surface (plate):

in the element area: 2x2 Gauss quadrature quadrangular, 3-point Gauss quadrature 3-angular

9-point Gauss-Lobatto quadrature per thickness


Wall - 2x2 Gauss quadrature quadrangular, 3-point Gauss quadrature 3-sided
Volume - 14-point reduced Gauss quadrature (equivalent to 3x3x3 Gauss quadrature)

Keywords

FE elements plasticity

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