Forces

Forces#

The Forces class in the mento package allows users to define and manipulate the primary forces acting on a structural element, such as axial force, shear force, and bending moment. This class is designed for flexibility in defining forces, with the ability to adjust and retrieve them in different stages of a structural analysis or design workflow.

Key Concepts#

  • Axial Force (`N_x`): Force applied along the axis of the element, along the x-x axis.

  • Shear Force (`V_z`): Force acting perpendicular to the axis of the element, along the z-z local axis.

  • Bending Moment (`M_y`): The moment caused by forces that induce bending about the y-y axis.

  • Unit System: You can define the unit system to display the forces for a Force object, metric or imperial.

These are the main forces considered to analyze a beam along it’s main axis. For Columns analysis in future releases, the Forces object will have to have shear and bending moment in both axis.

These forces are defined using compatible units from the Pint library, like kN or kip for forces and kN*m or ft*kip for moments.

Usage#

Below is a step-by-step guide on how to use the Forces class in your structural analysis workflows.

1. Creating a Forces Object#

To define the forces acting on a structural element, instantiate a Forces object. You can provide initial values for axial force (N_x), shear force (V_z), and bending moment (M_y). If no values are provided, the forces default to zero. The default unit_system for units display is metric.

from mento import Forces, kN, kNm

# Define a forces object with specific values
force = Forces(N_x=2*kN, V_z=10*kN, M_y=5*kNm)
print(force)

2. Accessing Forces#

Once a Forces object is created, you can access individual forces using the respective properties N_x, V_z, and M_y. These properties will return the forces in metric system by default, making it easy to inspect the current state of forces in your structure.

print(force.N_x)  # Output: 2.00 kN
print(force.V_z)  # Output: 10.00 kN
print(force.M_y)  # Output: 5.00 kN*m

If you want to display the Forces in imperial system just pass the input to the Force object when creating it.

force = Forces(N_x=2*kN, V_z=10*kN, M_y=5*kNm, unit_system="imperial")
print(force.N_x)  # Output: 0.45 kip
print(force.V_z)  # Output: 2.25 kip
print(force.M_y)  # Output: 3.69 ft*kip

3. Modifying Forces#

Forces can be modified at any point by calling the set_forces() method. This method allows you to update the values of N_x, V_z, and M_y.

# Update the axial and moment forces
force.set_forces(N_x=3*kN, M_y=7*kNm)
force.unit_system = "metric"
print(force)

4. Retrieving Forces as a Dictionary#

You can retrieve the forces in the form of a dictionary for easy manipulation, storage, or reporting. The get_forces() method returns a dictionary where the keys are N_x, V_z, and M_y, with values corresponding to the respective forces in the unit system.

force_dict = force.get_forces()
print(force_dict)
# Output: {'N_x': 3.00 kN, 'V_z': 10.00 kN, 'M_y': 7.00 kN*m}

5. Assigning a Label to a Force#

Optionally, you can assign a label to a force object to describe the specific load condition or scenario (e.g., “Crane load”, “Wind load”). This is useful in complex models where multiple forces are acting on different elements.

force.label = "Crane load"
print(force.label)  # Output: Crane load

6. Force Object ID#

Each Forces object is automatically assigned a unique ID, which can be accessed through the id property. This is helpful when tracking multiple force objects in more complex analyses.

print(force.id)  # Output: Unique ID (e.g., 1, 2, etc.)