CYPE 3D

General properties of the shells

In CYPE 3D, shell elements can be defined. Shells are flat two-dimensional elements with constant thickness and without openings, whose perimeter is defined by a polygon.

For analysis purposes, shells are introduced in the global stiffness matrix of the structure using a three-dimensional finite element model composed of six-node (quadratic) triangular flat shells. The type of element used is based on the overlap of two locally decoupled elements: one provides the axial stiffness (membrane forces) and the other the bending stiffness (panel forces).

The following properties can be defined for each shell:

• Thickness and subgrade modulus
  In the local Z axis direction.
• Material
  Concrete, rolled steel, cold-formed steel, aluminium and generic material (specifying the modulus of elasticity and Poisson’s ratio).
• Position
  With respect to the introduction plane.
• Discretisation
  The density of the mesh can be controlled by defining the maximum size of the triangle in the local x and y axes.
• Direction of the axes
• Internal fixity
  Internal fixity between the edges and other elements of the structure.
• External fixity
  The external fixity of the edges can also be defined, but in this case, the fixity is applied to all the shells sharing that edge. The possible external fixity configurations are the same as those available for nodes in CYPE 3D.
• Integration strips
  Integration strips in shells define lines on which, for a given strip width, the forces corresponding to the shell are integrated to obtain the bar forces.
  

Below are some examples of structures created with shells in CYPE 3D:

Data introduction

Geometric definition, material used, discretisation and integration strips

The “Shells” menu contains the options for introducing shell data (New, Move, Delete, Describe section, Describe disposition, Discretisation, Reverse the direction of the Z axis, Reverse the direction of the X axis, Describe material, Integration strips, Internal fixity, External fixity, Join, Divide, Search).

Each of these options provides help texts explaining how they work.

Importing text files

The text file import format (Tools menu > Import text files) has been extended in order to import shell elements. When this option is activated, a help text is displayed that provides information on the format that the text files must have in order to import a structure correctly.

Importing from DWG and DXF files

3DFace, Polyface mesh and Polygomesh entities are imported as shell elements in the layers where they are defined.

Defining loads

There are two ways of introducing loads on the shells. One is by using the options available in the "Loads" menu, which are identical to those available for bars or nodes. The other is to bring the shell into the area of a panel of loads.

In the first case, the loads that can be introduced are surface loads applied over the entire surface of the shell, their direction of application can be the global z-axis or the local z-axis of the shell.

In the second case, two restrictions must be taken into account:

• If a panel of loads contains a shell, the panel of loads must be completely covered by shells.
• If a shell is in contact with any of the surface loads of the panel the load must completely cover the shell. Under these conditions, the loads generated are again surface loads over the entire shell but whose direction and direction depend on those defined for the panel and the surface loads.

• The deformed shape of the currently selected combination including all elements of the structure and their animation.
  
• The displacements of the shell elements by means of contour plots. The values that can be consulted are:
  
  • Total displacement
  • Displacement in global X, Y or Z axis
  • Rotation about the global X, Y or Z axis
    
• The forces of the shell elements in local axes of the shell using contour plots.
  
• The stresses of the shell elements in local axes of the shell using contour plots. The following stresses can be viewed:
  
  • Normal X
  • Normal Y
  • Shear XY
  • Shear XZ
  • Shear YZ
  • Maximum normal stress
  • Minimum normal stress
  • Maximum shear stress

• These stresses can also be filtered by:
  
  • Top face
  • Bottom face
  • Maximum of both surfaces
  • Minimum of both surfaces
  • Absolute maximum of both surfaces
    

By viewing contour plots, several windows can be kept open simultaneously with different information in each of them.

The configuration of the different contour plot windows is associated with each of the CYPE 3D structure views and is maintained even if the contour plot window is closed as long as the program is not closed.

Reports

The reports that can be obtained in the program are as follows:

• Materials used
• Shell description
• Shell quantities by material
• Shell surface quantities by material
• Loads on shells
• Forces in integration strips by loadcase
• Forces in integration strips by combinations
• Forces in integration strips by envelopes