GS. Units in STAAD.Pro

Most values used by STAAD.Pro can be derived from two units, that of length and force. STAAD.Pro employs a system that the gives the flexibility of defining different parts of the model using different unit settings.

The units are controlled by the settings in the Options dialog which allow tables to dynamically change various values dynamically without changing the model or re-running the analysis. Note however, that this is built on top of a platform setting called base units which determines how the data is handled internally by STAAD.Pro.

Tip: There are several some instances in the program where the Current Units cannot be changed, such as when an input dialog is open. In this case, you can use the <F2> key to input different units.

When directly editing the input file, this is achieved by using the UNIT command (see TR.3 Unit Specification) as required in the input file.

STAAD.Pro also includes an extensive unit conversion utility.

Notes:

Mass / weight are determined from loading and are calculated assuming acceleration due to gravity of 9.81 m/s² or 32.2 ft/s².
Temperature and units that derive from temperature are taken to be specified in consistent units and are not converted by STAAD.Pro.

Base Unit System

As the name suggests, this is the core unit system that STAAD.Pro uses in a session and specified before any model can be loaded. The base units is specified in the Application Configuration dialog.

This can be set to either English or Metric. All the units are derived from the length unit and force unit (e.g., stress = force/length²). Thus the length and force unit is determined by the base unit such that when it is set to:

English - the data is handled by the program using the length unit as inches and the force unit of kips ("kilopounds," or 1,000 lbs).
Metric - the data is handled by the program using the length unit as meter and the force unit as kilonewton.

Notes:

This setting determines the first UNIT command that is created in any new model.
When using OpenSTAAD, the data accessed through its functions is determined by this setting.

Display Units

The Options dialog includes three sheets that allow for the setting of the units to be displayed in tables depending on the unit type. They fall into the categories of:

Structure Units, this sets the displays of the columns in tables where units such as dimension and displacement are set.
Section Units, this sets the displays of columns in tables of section profiles and material data
Force Units, this sets the displays of columns of data typically associated with loading and results.

Note: Although the general control of the display of results is defined by the Options dialog, a number of tables in the Post Processing support a method to quickly set a unit type by right-clicking on a column and then selecting the Change Unit for this column item from the pop-up menu to change the unit.

Current Input Units

As mentioned above, when a model is being created, it is possible to add data to the model with different unit settings in different locations of the input. The current can be set by using the Input Units tool on the Geometry ribbon. In the input file, this can be done by including additional UNIT commands.

When a model is first created, the current units are set to the unit defined by the Base Unit.

The current input units are displayed in the lower right corner of the application.

Notes:

When a file is opened, the Current Units are set to the options set in the last UNIT command that is included in the input file.
It is possible to mix and match the input units if required from the different systems. For example, length as CM from the metric system and force as KIP from the English system.