TR.28.1 Control/Dependent Specification

This set of commands may be used to model specialized linkages (displacement tying, rigid links) through the specification of "control" and "dependent" joints. Please read the notes for restrictions.

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

General Format

Dependent *{ XY | YZ | ZX | RIGID | FX | FY | FZ | MX | MY | MZ } CONTROL j JOINT joint-spec

where:

joint-spec = { joint-list  | *{ XRANGE | YRANGE | ZRANGE } f1 f2 }

Description

The control/dependent option provided in STAAD.Pro allows you to model specialized linkages (displacement tying, rigid links) in the system. For example, DEPENDENT FY … connects the two joints such that the Y displacement at the dependent will be the sum of Y displacement at the control plus the rigid rotation,

R sin θ

Note that instead of providing a joint list for the dependent joints, a range of coordinate values (in global system) may be used. All joints whose coordinates are within the range are assumed to be dependent joints. For convenience, the coordinate range specified for dependent joints in this entry may include the control joint for this entry. However, control and dependent joints of other entries must not be included in the coordinate range. All 2 or 3 ranges can be entered to form a "tube" or "box" for selecting joints in the tube or box region.

Fx, Fy etc. are the directions in which they are dependent (any combination may be entered).

If two or more entries have the same control, the dependent lists will be merged. Please ensure that the same direction specs are used.

The direction specifiers (XY, YZ, ZX) are combinations of the basic directions, XY is the same as entering FX, FY, MZ; etc. Any combination of direction specifiers may be entered. An example of the use of this format is: a rigid diaphragm floor that still retains bending flexibility entered as SLA ZX … .

If RIGID or if all directions are provided, the joints are assumed to be rigidly connected as if SLA DIA RIG were entered, even if DIA is omitted.

Note: Due to the mechanisms used to include control/dependent systems, if the reactions on control nodes are not included in a statics check then an out of balance report may result. This can be avoided by adding a short stiff member from a control node to the support.

Restrictions

Solid elements may not be connected to dependent joints.
Control joints may not be control or dependent in another entry.
Dependent joints may not be control or dependent in another entry.
Dependent directions at joints may not be supported directions or have displacements imposed.
Control and/or dependent joints may not be inclined supports.
The control/dependent specification is only intended for linear static and dynamic analysis.
Multilinear springs are not permitted.
Control/dependent joints may not be specified when rigid floor diaphragms are used (refer to TR.28.2 Floor Diaphragm).
If a CHANGE command is specified, then any control/dependent joints must be re-specified if they are intended to be used after the change. Further, any support commands must also be re-specified after the CHANGE command and immediately prior to the control/dependent command.

The internal processing of any control/dependent command includes an automatic bandwidth reduction.

Example

Fully Rigid and Rigid Floor Diaphragm

DEPENDENT RIGID CONTROL 22 JOINT 10 TO 45
DEPENDENT RIGID CONTROL 70 JOINT YRANGE 25.5 27.5
DEP ZX CON 80 JOINT YR 34.5 35.5