SECTION

Bulk Data Entry Defines a specific face of a cross-section of the model.

The section is determined through a set of Grid points and the face is specified by a set of elements. The face is interpreted as the side of the Grid point set not containing the specified elements.

Format

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
SECTION	`SID`	`LABEL`	`GSID`	`ESID`	`RSID`	`CID`	`GID`	`STYPE`

Definitions

Field	Contents	SI Unit Example
`SID`	Set identification number of the section. No default (Integer)
`LABEL`	The section name associated with the defined section. No default (Character string)
`GSID`	Set identification number of a `SET` of `GRID` points that defines the geometry of the section. 2 No default (Integer > 0)
`ESID`	Set identification number of a `SET` of elements (`TYPE`=ELEM) that defines the face of the section. 2 No default (Integer > 0)
`RSID`	Set identification number of a `SET` of rigid elements (`TYPE`=RIGID) that defines the face of the section. 2 No default (Integer > 0)
`CID`	Coordinate system identification number of the coordinate system into which the forces and moments are resolved. 7 LOCAL (Default) Indicates that a LOCAL coordinate system will be established automatically for the section chosen and use it for the output. The X-axis is normal to the section and the Y-axis comes from the projection of the basic Y-axis onto the section (for special case handling, see Comment 9). (LOCAL or Integer ≥ 0)
`GID`	Grid point identification number of the grid about which the moments are calculated. CENT Indicates that the coordinate system is shifted to the centroid of the section. PRIN Indicates that the coordinate system should also be rotated to the principal axes. ORIGIN Indicates that the reference point is the original of coordinate system of section (`CID`). Integer > 0 Grid point identification number about which the moments are calculated. Default = <Geometric Centroid of the Section>
`STYPE`	Identifies the type of section that is generated using this entry. RESULT Defines a face of the cross-section on which the forces/moments are calculated as a response in analysis and optimization runs (RESFORCE response). 1 FLOW Defines a face of the cross-section which is used for Power flow and Mechanical intensity calculations. 1 PROP Indicates that this section is only to be used for Section property analysis and optimization via `RTYPE`=`SECTION` on DRESP1. blank (Default)

Comments

The SECTION entry can be used to define a face of the cross-section on which the forces/moments are calculated as a response in analysis and optimization runs via RTYPE=RESFORCE (on the DRESP1 entry). In such cases, Grid Point Forces or Moments are added at each GRID specified within the grid set (GSID). The effect of all elements on the grid points (GSID) is considered in the calculation of the response except the elements specified via ESID. The SECTION entry can also be used for Power flow and Mechanical intensity calculations. For more information regarding Power flow calculations, refer to the POWERFLOW I/O Options Entry. For the Power flow and mechanical intensity calculations, only the GSID, ESID, and STYPE fields are required. The other fields are ignored if input.
The section is determined through a set of grid points and the particular face is specified by a set of elements. The face is interpreted as the side of the grid point set NOT containing the specified elements (Figure 1 through Figure 3). This is similarly applicable to RSID (rigid element set).

Figure 1. Defining the SECTION for the RESFORCE Response

Figure 2. Selecting the GSID Set

Figure 3. Selecting the Corresponding ESID
The default GID is the geometric center of the cross-section. For example, in a shell model, if the cross-section is tapered (Figure 4), the geometric center is automatically updated (if the GID field is blank).

Figure 4. Geometric Center via GID=Default
For Section property, if coordinate system is defined, then the properties are calculated in the defined system. If no coordinate system is defined, the basic system is used.
For Section property, currently only beam, bar, shells and solid elements are supported. Offsets are taken into account, and Shear center is currently not calculated.
SECTION is automatically created for both 1D and 3D pretension bolt section. For this case, CID is LOCAL and GID is CENT.
In cases when the local coordinate system from LOCAL cannot be uniquely determined, a warning will be printed. In such cases, it is recommended to use a user-defined coordinate system. The X-axis of this user-defined coordinate system must be normal to the cross-section.
This feature is supported for analysis, as well as optimization.
For a special case in which the SECTION only contains one grid and one beam/rod element, then its local X-axis is aligned with that element. This applies to both internally created sections (like 1D bolt pretention sections) or a user-defined SECTION with the same characteristics. Additionally, for this special case, the Y-axis is determined by projecting the global Y-axis on to the plane orthogonal to the local X-axis.
Information about both the user-defined SECTIONs and internally generated sections are output to the OPTI format .secres file and the .out file by default. The output to the .secres file can be controlled via the RESULTANT I/O Option.