/SECT/PARAL

Block Format Keyword A parallelogram section is used to output the force and moment of a cross section defined by a parallelogram.

The nodes and elements that define the section are automatically selected by intersecting the groups of elements with a parallelogram.

Format

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/SECT/PARAL/`sect_ID`/`unit_ID`
`sect_title`
`node_ID`₁	`node_ID`₂	`node_ID`₃		`I`_SAVE		$Δ t$		$α$
`file_name`
`grbric_ID`		`grshel_ID`	`grtrus_ID`	`grbeam_ID`	`grsprg_ID`	`grtria_ID`	`Ninter`		`I`_frame

Input read only if Ninter > 0

(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`int_ID`₁	`int_ID`₂	`int_ID`₃	`int_ID`₄	`int_ID`₅	`int_ID`₆	`int_ID`₇	`int_ID`₈	`int_ID`₉	`int_ID`₁₀

(1)	(3)	(5)
`X`_M	`Y`_M	`Z`_M
`X`_M1	`Y`_M1	`Z`_M1
`X`_M2	`Y`_M2	`Z`_M2

Definitions

Field	Contents	SI Unit Example
`sect_ID`	Section identifier. (Integer, maximum 10 digits)
`unit_ID`	Unit Identifier. (Integer, maximum 10 digits)
`sect_title`	Section title. (Character, maximum 100 characters)
`node_ID`₁	Node identifier `N`₁ defining the local output system of the section. (Integer)
`node_ID`₂	Node identifier `N`₂ defining the local output system of the section. (Integer)
`node_ID`₃	Node identifier `N`₃ defining the local output system of the section. (Integer)
`I`_SAVE	Flag for saving or reading the section data from file_name. =0 Do not save any data. =1 Save section displacements in the section cut file. =2 Save section displacements, resultant force, and moment components in the section cut file. =100 Read and apply the section data as loads to the model. =101 Read and apply the section data as loads to the model. Also output in the time history the difference between the applied section resultants (force and moment) and the simulation’s calculated section results. This option requires that the section data was created using the `I`_SAVE =2 option. (Integer)
$Δ t$	Time step for saving the section data used with `I`_SAVE =1 or 2. Default = time step of the simulation (Real)	$[s]$
$α$	Exponential moving average filtering constant (0 < $α$ < 1). Smaller values result in more filtering. Only used when applying the displacements to a section using `I`_SAVE= 100 or 101. Recommended value =0.62832 (Refer to Filter in the User Guide) Default = No filtering (Real)
`file_name`	Root name of the file which contains the flag output. The section file will be named file_nameSC01. Default = Runname (where, Runname is the prefix to the Engine file, Runname_0001.rad) (Character, maximum 100 characters)
`grbric_ID`	Brick group identifier. (Integer)
`grshel_ID`	Shell group identifier. (Integer)
`grtrus_ID`	Truss group identifier. (Integer)
`grbeam_ID`	Beam group identifier. (Integer)
`grsprg_ID`	Spring group identifier. (Integer)
`grtriag_ID`	Triangle group identifier. (Integer)
`Ninter`	Number of interfaces. (Integer)
`I`_frame	Flag defining the center of the local system used in the calculation of the section forces and moments. 3 The section output is in the local system with the center defined as: =0 Origin of the local section system. =1 Geometrical center of the section. =2 CoG of the section. =3 Global system point (0,0,0). The section output is in the global system with the center defined as: =10 Origin of the local section system. =11 Geometrical center of the section. =12 CoG of the section. =13 Global system point (0,0,0). (Integer)
`int_ID`₁, `int_ID`₂, ..., `int_ID`_n	Optional interface identifiers, if `Ninter` > 0. (Integer)
`X`_M	`X` coordinate of `M`. (Real)	$[m]$
`Y`_M	`Y` coordinate of `M`. (Real)	$[m]$
`Z`_M	`Z` coordinate of `M`. (Real)	$[m]$
`X`_M1	`X` coordinate of `M1`. (Real)	$[m]$
`Y`_M1	`Y` coordinate of `M1`. (Real)	$[m]$
`Z`_M1	`Z` coordinate of `M1`. (Real)	$[m]$
`X`_M2	`X` coordinate of `M2`. (Real)	$[m]$
`Y`_M2	`Y` coordinate of `M2`. (Real)	$[m]$
`Z`_M2	`Z` coordinate of `M2`. (Real)	$[m]$

Comments

The elements groups defined will be intersected by the defined parallelogram. The lines M–M1 and M–M2 (Figure 1) define the parallelogram. The section nodes are created from the nodes of those intersected elements, which are on the upside (z > 0) of the plane of the parallelogram.

Figure 1.
The forces and moments from the sections will be stored in the time history file and requested using /TH/SECTIO.
The local force and moment output system of the section is defined using 3 nodes. These three nodes should be nodes on the section plane, so their position is updated when the section moves. When using the Cross-Section Assistant in HyperMesh to create the section, the 3 nodes are automatically selected.
Local system is defined as:
- Nodes node_ID₁ and node_ID₂ define the local x-axis of the section.
- Nodes node_ID₁, node_ID₂, and node_ID₃ define the local plane xy of the section.
- The local y-axis is defined by projecting node_ID₃ perpendicular to the local x-axis.
- The intersection of the local x- and y-axis is then the origin of the system.
- Last, the section normal is the local z-axis which is perpendicular to the xy plane.
- The center of the section can be redefined using the I_frame option. Refer to Force and Moment Computation in the User Guide for further details.
Sections can also be used in a cut modeling method where section forces and displacements are saved from a full model and then applied in a second cut model. In the full model, the section information is saved using the I_SAVE =1 or 2 option. Then in the cut model, the same section nodes and element groups are defined and the section displacements are applied to the cut model using I_SAVE =100 or 101. The cut model is then used to study a detailed area of the full model.
Recommendations:
- Define I_frame =2 or 12, the center is the CoG of the section.
- Time history output GLOBAL and LOCAL in /TH/SECTIO.