Element Library¶
In FrontISTR, the element groups shows in Table 4.1.1 can be used for analysis. Since HEC-MW is used to input the mesh data into FrontISTR, the following descriptions of the element library is based on the description of HEC-MW. The element library is shown in Figure 4.1.1, and element connectivity and the definitions of the surface number are shown in Figure 4.1.2.
Table 4.1.1: Element Library List
| Element Types | Element No. | Description |
|---|---|---|
| Line element | 111 | Two node link element |
| 112 | Three node link element | |
| Plane element | 231 | Three node triangular element |
| 232 | Six node triangular quadratic element | |
| 241 | Four node quadrilateral element | |
| 242 | Eight node quadrilateral quadratic element | |
| Solid element | 301 | Two node truss element |
| 341 | Four node tetrahedral element | |
| 342 | Ten node tetrahedral quadratic element | |
| 351 | Six node pentahedral element | |
| 352 | Fifteen node pentahedral quadratic element | |
| 361 | Eight node hexahedral element | |
| 362 | Twenty node hexahedral quadratic element | |
| Connector element | 511 | Two node connector element (spring, dashpot) |
| Interface element | 541 | Quadrilateral cross section linear element |
| 542 | Quadrilateral cross section quadratic element | |
| Beam element | 611 | Two node beam element |
| 641 | Two node beam element (with four 3-dof nodes) | |
| Shell element | 731 | Three node three-dimensional linear element |
| 732 | Six node three-dimensional quadratic element | |
| 741 | Four node three-dimensional linear element | |
| 743 | Nine node three-dimensional quadratic element | |
| 761 | Three node three-dimensional linear element (with six 3-dof nodes) | |
| 781 | Four node three-dimensional linear element (with eight 3-dof nodes) |
Figure 4.1.1: Element Library
(Line Element)¶
(Triangular Plane Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 | 1 - 6 - 2 |
| 2 | 2 - 3 | 2 - 4 - 3 |
| 3 | 3 - 1 | 3 - 5 - 1 |
(Quadrilateral Plane Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 | 1 - 5 - 2 |
| 2 | 2 - 3 | 2 - 6 - 3 |
| 3 | 3 - 4 | 3 - 7 - 4 |
| 4 | 4 - 1 | 4 - 8 - 1 |
(Tetrahedral Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 - 3 | 1 - 7 - 2 - 5 - 3 - 6 |
| 2 | 1 - 2 - 4 | 1 - 7 - 2 - 9 - 4 - 8 |
| 3 | 2 - 3 - 4 | 2 - 5 - 3 - 10 - 4 - 9 |
| 4 | 3 - 1 - 4 | 3 - 6 - 1 - 10 - 4 - 8 |
(Pentahedral Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 - 3 | 1 - 9 - 2 - 7 - 3 - 8 |
| 2 | 4 - 5 - 6 | 4 - 12 - 5 - 10 - 6 - 11 |
| 3 | 1 - 2 - 5 - 4 | 1 - 9 - 2 - 14 - 5 - 12 - 4 - 13 |
| 4 | 2 - 3 - 6 - 5 | 2 - 7 - 3 - 15 - 6 - 10 - 5 - 14 |
| 5 | 3 - 1 - 4 - 6 | 3 - 8 - 1 - 13 - 4 - 11 - 6 - 15 |
(Hexahedral Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 - 3 - 4 | 1 - 9 - 2 - 10 - 3 - 11 - 4 - 12 |
| 2 | 5 - 6 - 7 - 8 | 5 - 13 - 6 - 14 - 7 - 15 - 8 - 16 |
| 3 | 1 - 2 - 6 - 5 | 1 - 9 - 2 - 18 - 6 - 13 - 5 - 17 |
| 4 | 2 - 3 - 7 - 6 | 2 - 10 - 3 - 19 - 7 - 14 - 6 - 18 |
| 5 | 3 - 4 - 8 - 7 | 3 - 11 - 4 - 20 - 8 - 15 - 7 - 19 |
| 6 | 4 - 1 - 5 - 8 | 4 - 12 - 1 - 17 - 5 - 16 - 8 - 20 |
(Connector Element)¶
To connect two nodes by a discrete spring or dashpot, the 2-node connector element (element type 511) is used. A connector element gives only stiffness or damping between the two nodes it connects; it has no shape, no cross section and no mass.
A connector element can represent four kinds of characteristics, which are determined by the material assigned to the element.
- Axial spring — a spring acting along the axis connecting the two nodes. Its direction follows the deformation of the model. It is given by
!SPRING_A. - Spring with specified degrees of freedom — a spring connecting a specified degree of freedom of one node with a specified degree of freedom of the other node. Its direction is determined by the degree-of-freedom numbers and does not follow the deformation. A different spring constant can be given for each direction. It is given by
!SPRING_D. - Axial dashpot — damping acting along the axis. It is given by
!DASHPOT_A. - Dashpot with specified degrees of freedom — damping connecting specified degrees of freedom. It is given by
!DASHPOT_D.
A spring contributes to the stiffness matrix and a dashpot to the damping matrix. Therefore a spring is effective in static, dynamic and eigenvalue analysis, whereas a dashpot is effective only in implicit dynamic analysis, in which the damping matrix is assembled, and has no effect in static analysis.
To place a spring between a node and the ground instead of between two nodes, use the spring boundary condition (!SPRING) rather than a connector element. It requires no element and elastically supports a degree of freedom of a node.
A connector element is defined in the mesh data as an element of type 511, and a section of section type INTERFACE is given to its element group. The spring constant and the damping coefficient are given as a material in the analysis control data. See !SPRING_A for details.
(Beam Element)¶
(Beam Element with 3-dof nodes)¶
Nodes 1 and 2 for translational DOF, nodes 3 and 4 for rotational DOF.
(Triangular Shell Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 - 3 [front] | 1 - 6 - 2 - 4 - 3 - 5 [front] |
| 2 | 3 - 2 - 1 [back] | 3 - 4 - 2 - 6 - 1 - 5 [back] |
(Triangular Shell Element with 3-dof nodes)¶
Node 1, 2 and 3 for translational DOF, nodes 4, 5 and 6 for rotational DOF.
| Surface No. | Linear |
|---|---|
| 1 | 1 - 2 - 3 [front] |
| 2 | 3 - 2 - 1 [back] |
(Quadrilateral Shell Element)¶
| Surface No. | Linear | Quadratic |
|---|---|---|
| 1 | 1 - 2 - 3 - 4 [front] | 1 - 5 - 2 - 6 - 3 - 7 - 4 - 8 [front] |
| 2 | 4 - 3 - 2 - 1 [back] | 4 - 7 - 3 - 6 - 2 - 5 - 1 - 8 [back] |
(Quadrilateral shell Element with 3-dof nodes)¶
Nodes 1, 2, 3 and 4 for translational DOF, nodes 5, 6, 7 and 8 for rotational DOF.
| Surface No. | Linear |
|---|---|
| 1 | 1 - 2 - 3 - 4 [front] |
| 2 | 4 - 3 - 2 - 1 [back] |
Figure 4.1.2: Connectivity and Surface Number