Import NASTRAN File: Rigid Bodies and Constraint Entities

Description

NASTRAN uses RBE1 to define a rigid body element (form 1). Straus7 imports RBE1 rigid bodies as multi-point links.

NASTRAN uses RBE2 to define a rigid body element (form 2). Depending on the selected components, Straus7 imports RBE2 rigid bodies as XY-plane, YZ-plane, ZX-plane or XYZ rigid links, or multi-point links.

NASTRAN uses RBE3 to define an interpolation constraint element. Straus7 imports RBE3 interpolation constraint elements as multi-point links.

NASTRAN uses RROD to define rigid pin-ended rods. Straus7 imports RROD rigid pin-ended rods as pinned links.

NASTRAN uses RBAR to define rigid bars. Straus7 imports RBAR rigid bars as XY-plane, YZ-plane, ZX-plane or XYZ rigid links, or multi-point links.

NASTRAN uses MPC to define multi-point constraints. Straus7 imports MPC multi-point constraints as multi-point links.

Single Point Constraints

NASTRAN uses SPC and SPCD to define single-point constraints or enforced displacements on one or two nodes. Straus7 posts a node restraint for each node specified. The component numbers (C1, C2) identify the fixed degrees of freedom. For example, the component "126" indicates that the DX, DY and RZ directions are fixed.

If a non-zero displacement (D1, D2) is specified, the restraint becomes a prescribed displacement in each specified direction. If the displacement is zero or undefined, the restraint becomes fully fixed in each specified direction.

SPC entries, like most bulk data attributes, are posted in an additive manner. A given node may have up to six different SPC entries, where each entry specifies a restraint in a given direction. For example, one SPC entry may specify that for a given node, DX, DY and DZ are fully fixed, but RX, RY and RZ are free. Another SPC entry may specify RX, RY and RZ are fully fixed, but DX, DY and DZ are free. The net effect of importing both entries is that all six degrees of freedom are fully fixed.

NASTRAN uses SPC1 to define single-point constraints for N nodes. Straus7 posts a node restraint for each specified node. As with the SPC and SPCD entries, the component number C defines which degrees of freedom are to be fully fixed.

Straus7 also supports the alternate THRU format to specify a range of node numbers.