# 32 docs tagged with "definition dialogs"

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## Applied Displacements

An applied displacement allows a fixed displacement to be applied to a node in the structure and calculates the deformation of the structure which results in the specified displacement at the specified degree of freedom. Thus applied displacements may be used to investigate the stiffness of a structure by constraining certain degrees of freedom to move by a fixed amount and noting the forces involved.

## Assemblies

Assemblies are way to define an entity that is formed from a collection of elements or members and can be thought of as a super-element. This is not an analysis entity but just a convenience for post-processing such as cut section forces. Typical uses of assemblies include cores, where the core is modelled with 2D finite elements, or trusses where the truss is modelled with top and bottom chords and bracing. In both these cases the assembly is identified by a list of included elements.

## Axes

This feature enables new user-defined axes systems to be specified e.g. to specify an inclined roller support, to assist in interpretation of results, or to specify the construction grid. Axes systems may be Cartesian, cylindrical or spherical.

Beam Loads are a ways of applying load to beam members and elements offering the commonly used load patterns as different types. When loads are applied to members, they will be automatically expanded to load the appropriate finite elements.

To optimise bridge loading based on an influence line analysis, any uniformly distributed load to be applied to a path needs to be specified either as a standard variable load or a user variable load.

## Constraint Equations

Constraint equations allow a node, in a particular direction to be constrained relative to a set of other nodes. Constraint equations are the fundamental building block for all other constraint types.

## Distortion

Distortions are used to model the effect of introducing a cut in an element and applying a translational or rotational displacement across the cut.

Edge Loads are loads applied to the edge of 2D elements. In general edge loads should be applied with care to ensure that the loading applied to the element is in a direction in which the element is stiff. Edge loads may not be applied to Flat Plate or Fabric type 2D elements.

## Elements

An Element is an entity that is analysed. Its topology and position is defined using Nodes and Offsets. Its orientation is defined by the element axis set which depends on the topology of the element and the orientation node and angle. Its end fixity is defined partly by the behaviour of the Element Type and partly by the element Releases.

Face loads on 3D members or elements are similar to face loads on 2D members or elements, with the additional requirement that the face be selected. Loads are specified as a pressure across the surface.

Face loads should be used where a load distributed over the face of a 2D member or element is required. When loads are applied to members, they will be automatically expanded to load the appropriate finite elements.

## Generalised Restraints

Generalised restraints allow a set of restraint conditions to be applied to a list of nodes, saving the effort of specifying restraints for individual nodes in the Nodes > Restraints table. The generalised restraints and nodal restraints work together to apply restrain to the model. Car must be taken to avoid conflicting constraints.

## Gravity

Gravity loads are a special case of body loads i.e. loads that apply internally throughout the body rather than being applied externally to the body. Unlike the other load types, gravity loads are an acceleration applied to mass in the structure.

These are area loads located in space or, more precisely, on a grid surface which is located in space. The grid surface is also used to identify the elements that are considered during the grid load expansion. Refer to Specifying Grid Loading for details.

These are line loads located in space or, more precisely, on a grid surface which is located in space. The grid surface is also used to identify the elements that are considered during the grid load expansion. Refer to Specifying Grid Loading for details.

These are point loads located in space or, more precisely, on a grid surface which is located in space. The grid surface is also used to identify the elements that are considered during the grid load expansion. Refer to Specifying Grid Loading for details.

## Grid Surfaces

A grid surface is required to in order to apply grid loads to the structure. The grid surface details how the grid load is transferred on to the structure.

## Joints

Joints allow nodes to be tied in the specified translational or rotational directions. Unlike rigid constraints, joints do not impose equilibrium on the model.

Node loads are the most fundamental type of load. A node load is a force or moment applied to a particular node or set of nodes. Node loads can be applied in local (i.e. node constraint axis), global or user defined axis directions. User axes can be Cartesian, cylindrical or spherical.

## Polylines

Polylines are used mainly in conjunction with grid loading to define lines or area that are loaded. Polylines are 2D entities that are interpreted with respect to the x-y plane of a grid plane.

## Pre-stress

Prestress is a general description covering prestress loads, initial strains and initial lengths. In all cases the result is a prestress condition (set of forces and/or moments) in the member or element.

## Pre-stress

Prestress loads can be thought of either as prestress forces, tendon prestress applied to the member or element or an initial strain. When loads are specified for members, they will be automatically expanded to load the appropriate finite elements.

## Rigid Constraints

Rigid constraints define sets of nodes constrained to move as a rigid body. These are commonly use to model rigid diaphragms, where typically the nodes are rigid in the x-y plane but not in the z direction.

## Settlements

A settlement forces a node to move a specified distance in a specified global or local direction in a particular load case, where the node has been restrained in the relevant direction.

## Thermal

In many cases it is useful to consider the effect of thermal loading on a structure. Thermal loads can have two effects. A uniform temperature change causes the entity to expand axially but induces no bending. However, the thermal gradient option defines a linearly varying strain through the thickness of the entity, resulting in both axial expansion and bending. The positions of the temperatures are used to define the temperature gradient.

## Thermal

Thermal loads on 3D members elements can either be uniform giving rise to a uniform thermal strain across the member or element, or variable with temperature specified at each node of an element.

## Thermal

In many cases it is useful to consider the effect of thermal loading on a structure. Thermal loads can have two effects. A uniform temperature change causes the member or element to expand axially but induces no bending. However, the thermal gradient options define a linearly varying strain through the thickness of the member or element so resulting in both in-plane expansion and bending.

## Tied Interfaces

Tied interfaces allow two sets of elements that do not have connectivity to be joined without the need for complex mesh refinement. Instead the elements on one side are taken as primary and the other side as constrained. The nodes on the boundary of the constrained side are tied to the nodes on the boundary of the primary side through a set of constraint equations.