# StructuralBC Properties

Boundary condition or boundary load for structural analysis model

**Domain-specific structural workflow is not recommended. New features might not be
compatible with this workflow. For help migrating your existing code to the unified
finite element workflow, see Migration from Domain-Specific to Unified Workflow.**

A `StructuralBC`

object specifies the type of
PDE boundary condition or boundary load on a set of geometry boundaries. A `StructuralModel`

object contains a vector of `StructuralBC`

objects in
its `BoundaryConditions.StructuralBCAssignments`

property.

To specify boundary conditions for your model, use the `structuralBC`

function. To specify boundary loads, use `structuralBoundaryLoad`

.

## Properties of StructuralBC

`RegionType`

— Geometric region type

`'Face'`

for 3-D geometry | `'Edge'`

for 2-D geometry

Geometric region type, specified as `'Face'`

for a 3-D
geometry or `'Edge'`

for a 2-D geometry.

**Data Types: **`char`

| `string`

`RegionID`

— Geometric region ID

vector of positive integers

Geometric region ID, specified as a vector of positive integers. Find the
region IDs by using `pdegplot`

with
`'FaceLabels'`

(3-D) or `'EdgeLabels'`

(2-D) set to `'on'`

.

**Data Types: **`double`

`Vectorized`

— Vectorized function evaluation

`'off'`

(default) | `'on'`

Vectorized function evaluation, specified as `'off'`

or
`'on'`

. This evaluation applies when you pass a
function handle as an argument. To save time in the function handle
evaluation, specify `'on'`

, assuming that your function
handle computes in a vectorized fashion. See Vectorization. For details on
this evaluation, see Nonconstant Boundary Conditions.

**Data Types: **`char`

| `string`

## Boundary Constraints and Enforced Displacements

`Displacement`

— Enforced displacement

numeric vector | function handle

Enforced displacement, specified as a numeric vector or function handle. The numeric vector must contain two elements for a 2-D model and three elements for a 3-D model. The function must return a two-row matrix for a 2-D model and a three-row matrix for a 3-D model. Each column of the matrix must correspond to the enforced displacement vector at the boundary coordinates provided by the solver.

**Data Types: **`double`

| `function_handle`

`XDisplacement`

— x-component of enforced displacement

number | function handle

x-component of the enforced displacement, specified as a number or function handle. The function must return a row vector. Each column of the vector must correspond to the value of the x-component of the enforced displacement at the boundary coordinates provided by the solver.

For axisymmetric models, this property contains the radial component (r-component) of the enforced displacement.

**Data Types: **`double`

| `function_handle`

`YDisplacement`

— y-component of enforced displacement

number | function handle

y-component of the enforced displacement, specified as a number or function handle. The function must return a row vector. Each column of the vector must correspond to the value of the y-component of the enforced displacement at the boundary coordinates provided by the solver.

For axisymmetric models, this property contains the axial component (z-component) of the enforced displacement.

**Data Types: **`double`

| `function_handle`

`ZDisplacement`

— z-component of enforced displacement

number | function handle

z-component of the enforced displacement, specified as a number or function handle. The function must return a row vector. Each column of the vector must correspond to the value of the z-component of the enforced displacement at the boundary coordinates provided by the solver.

**Data Types: **`double`

| `function_handle`

`Constraint`

— Standard structural boundary constraints

`'free'`

| `'fixed'`

| `'roller'`

| `'symmetric'`

| `'multipoint'`

Standard structural boundary constraints, specified as
`'free'`

,`'fixed'`

,`'roller'`

,
`'symmetric'`

, or
`'multipoint'`

.

**Data Types: **`char`

`Radius`

— Radius of circle (for 2-D geometry) or sphere (for 3-D geometry) around reference point location for multipoint constraint

positive number

Radius of a circle (for a 2-D geometry) or a sphere (for a 3-D geometry) around the reference point location for the multipoint constraint, specified as a positive number.

**Data Types: **`double`

`Reference`

— Reference point location for multipoint constraint

2-by-1 numeric vector | 3-by-1 numeric vector

Reference point location for the multipoint constraint, specified as a 2-by-1 (for a 2-D geometry) or 3-by-1 (for a 3-D geometry) numeric vector.

**Data Types: **`double`

## Boundary Loads

`Force`

— Concentrated force

numeric vector | function handle

Concentrated force at a vertex, specified as a numeric vector or function handle.

**Data Types: **`double`

| `function_handle`

`SurfaceTraction`

— Normal and tangential distributed forces on boundary

numeric vector | function handle

Normal and tangential distributed forces on the boundary (in the global Cartesian coordinates system), specified as a numeric vector or function handle. The numeric vector must contain two elements for a 2-D model and three elements for a 3-D model. The function must return a two-row matrix for a 2-D model and a three-row matrix for a 3-D model. Each column of the matrix must correspond to the surface traction vector at the boundary coordinates provided by the solver.

**Data Types: **`double`

| `function_handle`

`Pressure`

— Pressure normal to boundary

number | function handle

Pressure normal to the boundary, specified as a number or function handle. The function must return a row vector in which each column corresponds to the value of pressure at the boundary coordinates provided by the solver. A positive value of pressure acts in the direction of the outward normal to the boundary.

**Data Types: **`double`

| `function_handle`

`TranslationalStiffness`

— Distributed spring stiffness

numeric vector | function handle

Distributed spring stiffness for each translational direction used to model an elastic foundation, specified as a numeric vector or function handle. The numeric vector must contain two elements for a 2-D model and three elements for a 3-D model. The custom function must return a two-row matrix for a 2-D model and a three-row matrix for a 3-D model. Each column of this matrix corresponds to the stiffness vector at the boundary coordinates provided by the solver.

**Data Types: **`double`

| `function_handle`

## Time Variation of Force, Pressure, or Enforced Displacement

`StartTime`

— Start time for displacement component, pressure, or concentrated force load

nonnegative number

Start time for a displacement component, the pressure, or the concentrated force load, specified as a nonnegative number.

**Data Types: **`double`

`EndTime`

— End time for displacement component, pressure, or concentrated force load

nonnegative number

End time for a displacement component, the pressure, or the concentrated force load, specified as a nonnegative number.

**Data Types: **`double`

`RiseTime`

— Rise time for displacement component, pressure, or concentrated force load

nonnegative number

Rise time for a displacement component, the pressure, or the concentrated force load, specified as a nonnegative number.

**Data Types: **`double`

`FallTime`

— Fall time for displacement component, pressure, or concentrated force load

nonnegative number

Fall time for a displacement component, the pressure, or the concentrated force load, specified as a nonnegative number.

**Data Types: **`double`

## Sinusoidal Variation of Force, Pressure, or Enforced Displacement

`Frequency`

— Frequency of sinusoidal displacement component, sinusoidal pressure, or concentrated force

positive number

Frequency of a sinusoidal displacement component, the sinusoidal pressure, or the concentrated force, specified as a positive number, in radians per unit of time.

**Data Types: **`double`

`Phase`

— Phase of sinusoidal displacement component, sinusoidal pressure, or concentrated force

nonnegative number

Phase of a sinusoidal displacement component, the sinusoidal pressure, or the concentrated force, specified as a nonnegative number, in radians per unit of time.

**Data Types: **`double`

`Label`

— Label for use with `linearizeInput`

character vector | string

Label for use with `linearizeInput`

, specified as a
character vector or a string.

**Data Types: **`char`

| `string`

## Version History

**Introduced in R2017b**

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