The ThermalLoad object represents a thermal load applied to the structure.  All the thermal loads applied in a particular load case are stored in a ThermalLoads collection within the LoadCase object.  These loads can be accessed via the ThermalLoads property of the LoadCase object.  The methods and properties of the ThermalLoad object are summarised in the following table.

The Application, Frame, Number, Label and Index properties as well as the Delete method are common to many objects and are described in Chapter 2.

A thermal loading is added to a load case using the AddLoad method of the ThermalLoads collection.  This first parameter of this method specifies the element to which the load is to be applied.  The next parameter specifies the direction of the thermal gradient and takes an enumerated value of type mfDOF.  Although this enumerated type has six values, thermal loads can only be applied using the mfDOFy and mfDOFz directions.  The next two parameters are optional and specify the temperatures to be applied at the top and bottom of the element.  These values are set using the temperature units set within the Multiframe application.  The final two parameters are also optional and specify the depth and thermal coefficient to be used for the load.  If omitted, these values default to the depth of the elements section and a thermal coefficient 11.7mc.  For example, the following code adds a thermal load to the first load case.  The load applies a temperature gradient in the direction of the elements local y-axis, with temperatures of 25 and 150 units at the top and bottom of the element.

Dim myLoad as Multiframe.ThermalLoad

’Add load of magnitude 10.5 units to node 12
set myLoad=myFrame.LoadCases(1).ThermalLoads.AddLoad(12,mfDOFy,25,150)

The AddLoad method can also take an extra optional parameter that specifies if the load is to be applied in the global or the local nodal coordinate system.  By default, all Thermal Loads are added in the local nodal coordinate system. 

Multiple thermal loads can be created using the AddLoads method of the ThermalLoads collection.  This method returns a ThermalLoadList containing each of the loads added to the specified load case.  Each parameter in the AddLoads method may be either an array, containing values for each of the new load, or a single value that will be applied to each new load.  Several examples of how this method may be used are as follows:

Dim myLoads as New Multiframe.ThermalLoadList
 Dim myVar as Variant

’Get reference to thermal loads collection
 With myFrame.LoadCases(1).ThermalLoads

  ’Add a single load
  set myLoads =.AddLoads(12,mfDOFy,10.5,20.5)

  ’Add the same load at nodes 1,2 and 5
  set myLoads =.AddLoads(Array(1,2,5),mfDOFy,-10,10)

  ’Add two loads at node 12
  myVar=Array(mfDOFy, mfDOFz)
  set myLoads =.AddLoads(12,myVar,Array(7.5,5.5),120.0)

  ’Add two loads
  myVar=Array(4, 5)
  set myLoads=.AddLoads(myVar,myVar,Array(7.0,5.5),Array(9.5,5.6))

  ’Add a single load to each node in frame
  set myLoads =.AddLoads(myFrame.Elements,2,-50,50,250,12.3)

End With

The first parameter of the AddLoads method is a variant parameter identifying the element to which the loads are to be applied.  This parameter may specify the elements by an integer index, an array of integer indices, an Element object, an Element List, or an Elements collection.

A thermal load can be modified via the ThermalLoad object.  This object has properties describing the element to which the load is applied, the direction ft the temperature gradient, and the magnitude of the temperatures at each face of the element.

The element at which the load is applied is identified by the Element property of the ThermalLoad object.  This property returns the Element object corresponding the element at which the load is applied.

The DOF property controls the direction in which the temperature gradient is applied.  The property is an enumerated value of type mfDOF.  Although this enumerated type has six permissible values, thermal loads may only be specified with values of mfDOFy or mfDOFz that correspond to a temperature gradient applied in the directions of the elements local y and z axes. The direction of the thermal loading may also be specified using the Kind property.  This property is a character string describing the direction in which the load is applied.

The magnitudes of the temperatures at each face of the element are referenced by the Ttop and Tbottom properties of the ThermalLoad object.  The Ttop property specifies the temperature on the face of the element lying in the positive plane of the local element axis in which the thermal load is applied.  Conversely, Tbottom is the temperature at the face in the negative plane.  The values of these properties are specified in terms of temperature units currently set within the Multiframe application.

The Depth property of the ThermalLoad object specifies the depth over which temperature gradient is applied.  This is described using the current displacement units.  The thermal coefficient used to model the material in the thermal load is referenced via the Coeff property that is expressed using the current units of thermal expansion

The LoadCase, Frame and Application properties of the thermal load object identify its parent objects.  These properties cannot be modified.