Users:General FEM Analysis/Elements Reference/NURBS BRep Edge beam

Coded and tested.

Contents 1 Element Type 2 Degrees of Freedom 3 Parameter Description 4 Example of a Complete Input Block 5 Element Loading 6 Benchmarks 7 References

Element Type

This element formulation is based on geometric description. The center line of the beam is described by a NURBS curve within the parameter space of a NURBS surface. The beam is therefore autmatically coupled to the surface.

• This element provides a geometrically nonlinear, isogeometric spatial beam within a NURBS surface.
• Torsion without warping is included.
• Twisting is dependent or dependent of the underlying NURBS surface.
• Mass computation is implemented.

Degrees of Freedom

The element uses the translatoric degrees of freedom (Disp_X, Disp_Y, Disp_Z) at each control point. There is an optinial, additional, rotational degree of freedom (Rot_Tan), if the beam is twisted independently to the surface.

Parameter Description

Compulsory Parameters
Parameter	Values, Default(*)	Description
MAT	EL-MAT int	Linking to a material input block
INT_TYPE_NURBS_BREP_BEAM	FULL, USER	Control of integration type. If USER, the optional Parameter GAUSS_U (and GAUSS_V) has to be defined
AREA	float	area of the cross section of the beam
IY	float	moment of inertia
IZ	float	moment of inertia
IT	float	moment of inertia around the beam axis
TOR	int	beam twisting is independent of surface. The parameters 1 (yes) and 0 (no) are valid.
Optional Parameters
Parameter	Values, Default(*)	Description
GAUSS_U	int	Number of Gauss point per element. Must only to be defined when INT_TYPE_NURBS_BREP_BEAM = USER
AXIS	AXIS float1 float2 float3 float4	Definition of the cross sectional principal axis. Second axis is perpendicual to first and tangent of the curve. float1 is the position on the curve and float - float4 the direction (x,y,z). Base vectors are normalized and linearly interpolated for postions inbetween the defined ones. Axes for start and end knot of the NURBS curve are mandatory. (not yet working!)

Example of a Complete Input Block

EL-PROP 1 : NURBS_BREP_BEAM  
  MAT= EL-MAT 1
  AREA = 1.0
  IY = 1.0
  IZ = 1.0
  IT = 1.0
  TOR = 0 or 1
  INT_TYPE_NURBS_BREP_BEAM = USER or FULL
  GAUSS_U = 4

Element Loading

The Cord_3D_NURBS element is able to carry the following loads:

• dead load
• snow load
• pressure load
• moment load

Benchmarks

Currently, no main benchmark file in the Carat++-repository is available.

References

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