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 loads can be applied to a specified list of 1D members or elements. When loads are applied to members, they will be automatically expanded to load the appropriate finite elements.

Either constant temperatures or temperature gradients can be applied to a member or element. In either case the temperature values specified are changes in temperature from ambient.

The temperature gradient is defined by applying temperatures at notional lower and upper surfaces. These do not need to coincide with the actual lower and upper surfaces of the member or element (which may not be known). The temperature gradient is then calculated from the top and bottom temperatures ($T_{p}$ and $T_{t}$) and the top and bottom locations ($p_{p}$ and $p_{t}$) as follows:

$$\frac{dT}{dp} = \frac{T_{top}-T_{bot}}{p_{top}-p_{bot}}$$

This temperature gradient applies to the section as a whole.

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 beam, bar, tie, strut or cable members or elements to which the thermal loads apply 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 beam and bar 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 thermal 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.

• Uniform – a constant temperature rise applied to the whole member or element
• Gradient in y – a temperature gradient is applied in the member or element y direction
• Gradient in z – a temperature gradient is applied in the member or element z direction

Uniform temperature

The temperature rise relative to ambient applied to the whole member or element.

Lower surface, temperature

For temperature gradients the temperature profile is defined by the temperature at two points, referred to as the lower and upper surfaces. This defines the location and temperature rise that applies in the negative y or z directions relative to the neutral axis. A negative value denotes a position below the neutral axis.

Upper surface, temperature

This defines the location and temperature rise that applies in the positive y or z directions relative to the neutral axis.