Loads

A practically unlimited number of loads can be applied on the beam.

Note: Although the app does not impose a strict limit on the number of loads and supports, there are practical limits due to the device screen size, memory, and CPU capacity.

Three types of loads are supported:

Adding loads

To add a load:

  1. Go to the home screen.
  2. If necessary, unselect everything by tapping on an empty area.
  3. Press down on a load icon from the load toolbar.
  4. Drag and place the load on the beam.

Specifying load values

Forces, moments, and distributed forces are defined by two types of values:

  1. Location along the beam
    • Location can be quickly set by dragging the load along the beam. To do this, simply touch a load and drag your finger along the screen. AND
    • Location can also be set by selecting an editable label and modifying the value using the numpad.
  2. Magnitude
    • A magnitude value can only be set by selecting an editable label and modifying value using the numpad.
    • A magnitude sign can be set in two different ways: You can quickly change the sign of a force by dragging the force vertically across the beam. You can also specify the sign of a force using the ± button in the numpad.

Sign conventions

To simplify the representation of direction for forces and moments, instead of defining positive and negative sign conventions, the app displays direction visually using icons and other graphics.

In the screenshots, notice that the direction of loads is displayed in two ways:

  1. The load icon itself illustrates the direction of the applied load. For example, upward applied forces are represented by arrows that point up, and counter-clockwise applied moments are represented by circular arrows that point in a counter-clockwise rotation.
  1. The direction of the load is also displayed in the magnitude value label for each load. For example, next to the "1 kN-m" value for a moment magnitude, there is a circular arrow that can point clockwise or counter-clockwise, depending on the direction of the applied moment.

Force loads

Forces (point loads) are represented by a vertical arrow.

Forces are defined by two values:

  1. Location along the beam (with units of length, such as meters, inches, etc.)
  2. Force magnitude (with units of force, such as Newtons, kilograms, pound-force, etc.)

Note: Normally, kilograms are considered to be units of mass rather than units of force. The app, however, assumes that kilograms and pounds are units of force by multiplying internally by the gravitational constant. We use the conversion factor of 9.80665 N/kg to convert between force and mass.

Moment loads

Moments are represented by a pair of circular arrows.

Moments, like forces, are defined by two values:

  1. Location along the beam (with units of length, such as meters, inches, etc.)
  2. Moment magnitude (with units of force-distance, such as Newton-meter, lb-ft, etc)

Distributed force

Distributed forces (distributed loads) are represented by a an array of vertical arrows.

Distributed forces are slightly more complex than point forces and moments because they are defined by four values:

  1. Two independent positions along the beam (with units of length, such as meters, inches, etc.)
  2. Two independent force magnitudes (with units of force, such as Newtons, kilograms, pound-force, etc.)

Since all of these four values are independent of each other, there is a lot of flexibility when they are being specified and modified. For example, the left position and the right positions can be swapped without a problem. Also, the force magnitudes can have opposite or equal signs. It's also possible to set one magnitude to be zero and the other one to be non-zero.

Tip: Although distributed loads are defined by two positions, when using the numpad editor, it is possible to select one of 3 labels to edit.

  1. You can edit the distance from the left end of the beam to the first position of the load.
  2. You can edit the distance between both of the load's end-points, OR
  3. You can edit the distance from the right-most load end-point to the right end of the beam.

Tip: When you drag a distributed load using the graphic editor, it matters where you press on the load:

  1. If you select the left side of the load, you will only drag that left-most end-point of the load.
  2. If you select the center of the load, you will drag both end-points of the load.
  3. If you select the right side of the load, you will only drag that right-most end-point of the load.
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