====== DG shell boundary conditions ======

Since shell formalism only takes displacements into account, rotating boundary conditions are imposed though a DG formulation.

===== Materials =====

As for [[doc:user:start#boundary condition elements]], there is no material to associate to an element.

===== Elements =====

Since no material is required, the first stage consists in defining an ElementProperties:

  prp = ElementProperties(typeEl)
  prp.put(param1, value1)
  prp.depend(param1, fct1, Lock1)) #facultatif
  ...

where

|''typeEl'' | desired type of element (for example ''BoundaryDgShellFirstDegreeElement'')|
|''param1''| name of the property associated to the element (for example ''STIFFMETHOD'')|
|''value1''| value of the corresponding property |
|''fct1''| function which characterizes the dependency of the property (optional: no fct if no dependency) |
|''Lock1''| [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |

====  BoundaryDgShellFirstDegreeElement ====

DG interface element to insert on shell boundaries to provide BCs. These are 2-nodes linear lines, but they are interfering over all neighboring dofs.

By default, stresses are integrated over dim*2 integration points. The material used is  [[doc:user:elements:shells:interface#dgShellMaterial]].

====  BoundaryDgShellSecondDegreeElement ====

Same as ''BoundaryDgShellFirstDegreeElement'', but 8-nodes second order shell element.

====  BoundaryDgShellNineNodeSecondDegreeElement ====

Same as ''BoundaryDgShellSecondDegreeElement'', but 9-nodes second order shell element.

====  BoundaryDgShellSixteenNodeThirdDegreeElement ====

Same as ''BoundaryDgShellNineNodeSecondDegreeElement'', but 16-nodes third order shell element.

==== Parameters of shell boundary conditions elements ====
^   Name            ^     Metafor Code     ^  Dependency ^
| ''MATERIAL''    | Number of the material to consider              |  -  |
| ''STIFFMETHOD'' | Method used to compute the stiffness matrix \\ = ''STIFF_ANALYTIC'' : analytic matrix (default) \\ = ''STIFF_NUMERIC''  : numerical matrix            |  -  |
| ''BENDING_NPG''  | Number of integration points along one direction for bending solving \\ = 2 classical solving  (second order)\\ = 3 EAS solving with 22 or 7 added modes (8 or 9-nodes second order)\\ = 4 solving without EAS (16-nodes third order)|  -  |
| ''NORMAL_PT1''| First point governing the element of the shell normal |  -  | 
| ''NORMAL_PT2''| First point governing the element of the shell normal |  -  |


===== Interactions =====

Once created, the element is generated by a ''DgShellInteraction'':

  dgBound = DgShellInteraction(number)
  dgBound.push(gObject1)
  dgBound.push(gObject2)
  ...
  dgBound.addProperty(prp)
  interactionset.add(dgBound)  # the interaction is added in InteractionSet

or 

  dgBound = interactionset.add( DgShellInteraction(number) )
  dgBound.push(gObject1)
  dgBound.push(gObject2)
  ...
  dgBound.addProperty(prp)

| ''number'' | Number of the material to consider |
| ''gObject1'', ''gObject2'' | mesh geometric entities |
| ''prp'' | [[doc:user:elements:general:def_element_properties|Properties]] of the [[#Eléments|DG boundary condition elements]] to generate |

Generally, entities are lines or groups of nodes on a line.