Models can be built from several type of finite elements. All element types can be used for static, first order vibration or buckling analysis. Static and second oder vibration analysis with geometric nonlinearity is available only for beam structures.
The truss and the cubic beam element are the most widely used finite elements for bar, beam, or column modeling. The rib element is a 3-node isoparametric element with quadratic displacement interpolation that can be used similar to the beam element (but takes account for the shear deformations) or in conjunction with surface elements for eccentric rib modeling.
The surface elements are isoparametric flat quadrilateral (8/9-node) or triangular (6-node) elements. All use quadratic shape functions to interpolate displacements, and pass the patch test for arbitrary shape. The plate end shell elements use Mindlin's plate assumptions in a Heterosis formulation.
Using diaphragms means simplifying the model. Diaphragms are special rigid bodies where the relative position of the element nodes remain constant in a global plane. It can be an advantage running vibration analysis of big models. Diaphragms can represent plates totally rigid in their planes. The running time is reduced if the model contains only columns and slabs. If structural walls are included, the number of equations will be reduced but the band-width will be increased. The resultant running time may be greater than without diaphragms.
Edge hinges can be defined between domain edges or between a rib and an edge. Both the edge and the domain have to be selected. Stiffness values must be defined in the local coordinate system of the edge.
The rigid elements can model rigid parts of your structures without assigning large stiffness values to an element. The element can have any number of nodes.
The spring elements can account for linear or nonlinear elastic support or connection behavior.
The gap elements can model point-to-point contact conditions. The elements have a large stiffness when active and a small (but non-zero) stiffness when in an inactive state. The active state can be for compression or for tension. An initial opening can be specified for the elements.
Link elements connect two nodes (N-N) or two lines (L-L) and have six stiffness components (defined in their coordinate system) that are con¬cetrated on an interface (located between the connected nodes/lines). Its position can be entered relative to one node/line that is considered as reference. Link elements can have a nonlinear parameter called limit resistance that limits the force they are able to transfer.
These support elements can have a specified stiffness, and the resulting internal forces are the support reactions. Nonlinear characteristics (tension only, compression only, or limit resistance).
These elements can model elastic foundation support conditions of line elements. Nonlinear characteristics (tension only, compression only, or limit resistance).
These elements can model elastic foundation support conditions of surface elements. Nonlinear characteristics (tension only, compression only, or limit resistance).