Prestress

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.

The tendon prestress option allows for the prestress to be offset by a constant distance from the centre of the member or element in the thickness direction to induce bending.

The prestress or initial strain is applied in either the local x or y direction or in both directions.

A member or element with a positive prestress tends to contract, as in a prestressed slab.

Definition

Name

The name is only used as a convenient way of identifying a load (optional).

Entity type

This specifies whether a list of members or elements will be used to define which entities the load will be applied onto.

In sculpt: The entity type is set to either members or elements based on what is in the current selection set.

Entity list

This specifies a list of 2D members or elements to load using any one of the forms detailed in our entry on lists. The list may be a single item.

In sculpt: The entity list is set to the 2D members or elements in the current selection set. The entity list cannot be edited in the dialog.

Load case

The load case in which the load applies. The load case gives a way of grouping load effects together.

Type

The user has a choice of the type of loading applied to the members or elements.

• Prestress force – an in-plane force applied to the memeber or element
• Initial strain – an initial in-plane strain is specified in the member or element
• Tendon prestress – an in-plane force is applied to the member or element at an offset from the neutral axis. Only the latter option induces forces and moments in the member or element.

Direction

The direction in which the load applies in element local axes. This can be x, y or both x and y directions where x and y are element local directions. If prestress loads are specified for a member, GSA will apply the load to the constituent elements in the direction of the elements' local axis.

Prestress force

The prestress force (load per unit length) to apply to the member or element.

Initial strain

The initial strain in the member or element.

Tendon prestress, offset

The prestress force (load per unit length) and offset (in the local z direction) to apply to the member or element. When the offset is specified the member or element is loaded by an in-plane force and a moment.