Setting Units in ETABS

1. Unit Options for the Model File

When creating a new model or changing units during modeling, it's important to select the appropriate unit system. ETABS provides a set of predefined unit options.

Unit Options Table:

Unit	Value	Description
lb_in_F	1	Pounds (lb) and inches (in), Imperial units
lb_ft_F	2	Pounds (lb) and feet (ft), Imperial units
kip_in_F	3	Kips (kip) and inches (in), 1 kip = 1000 lb
kip_ft_F	4	Kips (kip) and feet (ft), 1 kip = 1000 lb
kN_mm_C	5	Kilonewtons (kN) and millimeters (mm), SI units
kN_m_C	6	Kilonewtons (kN) and meters (m), SI units
kgf_mm_C	7	Kilogram-force (kgf) and millimeters (mm)
kgf_m_C	8	Kilogram-force (kgf) and meters (m)
N_mm_C	9	Newtons (N) and millimeters (mm), SI units
N_m_C	10	Newtons (N) and meters (m), SI units
Ton_mm_C	11	Metric tons (Ton) and millimeters (mm)
Ton_m_C	12	Metric tons (Ton) and meters (m)
kN_cm_C	13	Kilonewtons (kN) and centimeters (cm)
kgf_cm_C	14	Kilogram-force (kgf) and centimeters (cm)
N_cm_C	15	Newtons (N) and centimeters (cm)
Ton_cm_C	16	Metric tons (Ton) and centimeters (cm)

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2. Initialize Model with a Specific Unit System

To start a new model with a specific unit system, use the InitializeNewModel() function. This function sets up the model with the desired units.

Syntax:

EtabsModel.InitializeNewModel(units)

Parameters:

• units: (Optional) The unit system to be used for the new model. The unit system is specified using the predefined unit values from the table above. The default value is kip_in_F (1).

Example:

# Initialize a new model with the unit system 'kN_m_C' (option 6 from the table)
kN_m_C = 6
init = EtabsModel.InitializeNewModel(kN_m_C)
if init != 0:
    print("Failed to initialize the model.")

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3. Change Units During Modeling

You can also change the units of an existing model during modeling using the SetPresentUnits() function. This allows you to switch between different unit systems as needed for different parts of the modeling process.

Syntax:

EtabsModel.SetPresentUnits(units)

Parameters:

• units: The unit system to be used for the current model. It is chosen from the predefined list of unit options in the table above.

Example:

# Change the current units to 'kN_m_C' (option 6 from the table)
set_unit = EtabsModel.SetPresentUnits(6)
if set_unit != 0:
    print("Failed to change the units.")

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Summary of Functions:

Function	Description
InitializeNewModel(units)	Initializes a new model with the specified unit system.
SetPresentUnits(units)	Changes the units of the current model during modeling.