# Node Specification dialog

Used to specify rigid links or specialized linkages in the structure. This facility can be used to model special structural elements such as ties or a floor diaphragm which makes the floor rigid for in-plane movements. The process is to select a node to act as the control and then degrees of freedom for which the dependent nodes are linked to the control.

Note: Refer to TR.28 Rigid Diaphragm Modeling for additional details.

Opens when Node is clicked on the Specifications - Whole Structure dialog.

Note: STAAD.Pro is also capable of defining a rigid floor diaphragm without the need to specify a "control" node. This feature is only available by manually editing the STAAD input file. Refer to TR.28.2 Floor Diaphragm for additional details

## Control/Dependent tab

Note: Control / Dependent was formerly referred to as master / slave.
SettingDescription
Control Node

It is called as such because the displacements of the dependent node will be based on the displacement of this "control" node. From the drop-down list, select the node which should serve as the control node.

Dependent Directions
• Rigid - This is a means of defining that the link which connects the control with the dependent has infinite stiffness for all the six degrees of freedom. In other words, if one were to consider an imaginary object that has infinite stiffness axially, for shear, torsion and bending, that would be the type of link which connects the control and the dependent.

Note: By default, STAAD.Pro keeps this box checked. Un-check this box to activate the options described below.
• XY, YZ, and ZX - This is a way of specifying a type of connection where the rigidity is limited to in-plane directions.

The plane of this link is defined in terms of the global planes XY, YZ, or ZX. For example, if you have a concrete slab in a building, and the slab can be assumed to be nearly inflexible for translations along global X and global Z, and the rotation about global Y, that type of link would be called a "diaphragm" in global XZ.

XY is equivalent to a Control-Dependent relationship for the degrees of FX, FY and MZ. Similarly, YZ is equivalent to linking FY, FZ and MX, and, ZX is equivalent to linking FX, FZ and MY.

• FX, FY, FZ, MX, MY, and MZ - This provides a way for linking only the specific degrees of freedom you want.

## Floor Diaphragm tab

SettingDescription
Diaphragm group
SettingDescription
No Select diaphragm number.
Type

Select the diaphragm type from the drop-down list:

Rigid - a diaphragm that translates & rotates as a rigid body.

Floor Level group

Select one of the options as the method to define the floor level of the diaphragm.

SettingDescription
Height Type the global coordinate value (elevation), in Y direction, to specify floor level.
YRange Select this option to define the floor level by upper and lower bounds of Y coordinates.
YRange group

Used when the YRange option is selected.

SettingDescription
Minimum The lower bound of Y coordinates for the Y range.
Maximum

The upper bound of Y coordinates for the Y range.

Control Node Information group

Select the method used to define the Control node of the diaphragm.

SettingDescription
Calculate The diaphragm center of mass is determined and a node is created at that location to use as the Control node.
Select Control Node Select the existing node to use from the drop-down list.
Define Floor Range Set this option to define the floor range as a XZ range of coordinates or by manually selecting coordinates.