TR.3 Unit Specification

This command allows you to specify or change length and force units for input and output.

Description

The magnitude of numerical data that is entered in a STAAD model is determined by the unit of that data. STAAD.Pro supports numerical data based on both English and Metric unit systems.

The method used by STAAD.Pro to determine the unit of any value is by the previous UNIT command.

The UNIT command can set or change the unit of LENGTH, FORCE, or both. This can be set any number of times in a STAAD input file to specify data or generate output in the desired length or force units, subject to the conditions noted below. All data is assumed to be in the most recent unit specification preceding that data.

General Format

UNIT *{ length-unit  | force-unit }

where:

length-unit  = { INCHES | FT or FEET | METER | CM | DME | MMS | KM }

force-unit  = { KIP | POUND | KNS | | DNS | NEWTON | MNS | MTON | KG }

The following tables illustrate the unit and the relative factor against the primary base unit:

Table 1. Units of length in STAAD.Pro
Required Length Unit		Base Unit	Factor	`UNIT` command parameter
English	Inch	Inch	1	IN
English	Foot	Inch	12	FT (or FE)
Metric	Meter	Meter	1	ME
	Decimeter	Meter	0.1	DM
	Centimeter	Meter	0.01	CM
	Millimeter	Meter	0.001	MM
	Kilometer	Meter	1,000	KM

Table 2. Units of force in STAAD.Pro
Required Force Unit		Base Unit	Factor	`UNIT` command parameter
English	Kip (kilopound)	Kip	1	KI
English	Pound	Kip	0.001	PO
Metric	Kilonewton	Kilonewton	1	KN
	Decanewton	Kilonewton	0.1	DN
	Newton	Kilonewton	0.001	NE
	Meganewton	Kilonewton	1,000	MN
	Metric Ton	Kilonewton	9.80665	MT
	Kilogram	Kilonewton	9.80665 (10)^-3	KG

Example

UNIT KIP FT
UNIT INCH
UNIT METER KNS
UNIT CM MTON

Notes

A UNIT command may be inserted before any primary level command (e.g., JOINT COORD, MEMBER INCIDENCE, etc.).
If no UNIT command is specified, then the default units are taken as:
- Length: feet
- Force: kips
Units can be mixed between systems of units, such as length of feet and force of kilonewtons.
Units that include both length and force components (e.g., stress = force/length²) will be constructed from the current length and force units.
Thus, if the current length unit is feet and force unit is kilonewtons, then when defining Young's modulus, the value for a stress unit is kN/ft². While this may be an odd definition, it is fully supported by STAAD.Pro.
Kilograms and metric tons are mass units which are converted to units of force assuming an acceleration due to gravity of 32.174 ft/s².
Temperature units are not explicitly defined in STAAD.Pro. The value of temperature loading and coefficient of thermal expansion are taken to be consistent units.
A UNIT command should be avoided immediately prior to the analysis command. Warnings will be presented in the output if one is included. Instead, to change the units of the output, the UNIT command should be included after the analysis command and prior to any post-analysis print commands.