Understanding imported Nastran constraints

On import, this software groups single point constraints (SPC) bulk data entries in the solver import file together for display in the Simulation Navigator. Constraints that share all the following attributes are collected in the same group:

• Card name (SPC, SPC1, SPCD)

• Nastran constraint set ID (SID)

• Constraint value

• Constrained degrees of freedom (DOFs)

Before grouping constraints, the software combines constrained degrees of freedom associated to a given node, provided that they share the same card name and Nastran constraint set ID.

For example, consider the following entries in a Nastran input file:

SPC,100,1000,123SPC,100,1000,456SPC,101,1000,123SPC1,101,1000,456

Each of these constraints is applied to node (called a grid point in Nastran) 1000. In this example, the first two SPC entries share the same bulk data entry name and the same SID. Therefore, on import, their degrees of freedom are combined. The third entry has the same bulk data entry name but a different SID, so it is not grouped with the first two. Similarly, the fourth entry has the same SID as the third bulk data entry, but a different bulk data entry name, so it not grouped with the third.

To summarize, from four Nastran constraint bulk data entries, three constraints are created:

• A constraint for node 1000 having the card name SPC_1 and fixed DOFs 123456.

• A constraint for node 1000 having the card name SPC_2 and fixed DOFs 123.

• A constraint for node 1000 having the card name SPC1_1 and fixed DOFs 456.

Likewise, the software groups load bulk data entries from the solver input file together in the Simulation Navigator. If loads share all the same Pre/Post attributes, they are grouped as a single Pre/Post load with the name of the Pre/Post load card.

The following figure shows imported Nastran loads and constraint sets as displayed in the Simulation Navigator. Each constraint represents a grouping of Nastran SPC bulk data entries sharing the same constraint set ID and constraint value. Loads and constraints are listed by their bulk data entry name.

Load Container Constraint Container

Imported loads and constraints as displayed in the Simulation Navigator

Learn more

Extended mesh validity checking during import (Nastran and ANSYS)

Importing RBE2 and RBE3 elements

Understanding the import of Nastran SETs

Import of SPOINT bulk data entries

Importing and exporting table extrapolation options

Exporting and importing CBEAM and CBAR elements with the OFFT field

Importing physical property data as element-associated data

Managing element conflicts when appending a Nastran input file

Look up more details

Importing Nastran data

Import for connection elements

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Pre/Post video examples

Bulk Entry Descriptions

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Understanding imported Nastran constraints, Simcenter 3D 2021.1 Series

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