Form: Frame Distributed Loads
Distributed (Uniform and Trapezoidal) forces and moments can be assigned along the length of frame objects. The loads may be as simple or as complicated as required.
Loads are specified in force-per-length or moment-per-length units.
Select one or more frame objects to be assigned loads.
Use the Assign menu > Frame Loads > Distributed command to access the Frame Distributed Loads form.
Load Pattern Name. Choose the load pattern to which the load(s) is being added. Alternatively, click the + (plus symbol) beside the drop-down list to access the Define Load Patterns form; use the form to define a load pattern that will then be available in the drop-down list.
Units. Choose the units to be used on this form.
Load Type and Direction. Specify the load type (Forces or Moments) and coordinate system and the load direction.
Note: The Gravity direction is taken to be in the negative Global Z direction. To enter a load in the gravity direction, enter a positive number if the direction is set to Gravity and a negative number if the direction is set to Global Z.
Options Specify how the load will be applied.
Add to Existing Loads: Adds the specified distributed load to the frame object. If one or more distributed load assignments have already been made, this option increases the existing load, assuming a positive load is being specified.
Replace Existing Loads: Replaces the currently specified distributed load, if any, with the new load. If no assignment exists, the new assignment is still made. This is the default option.
Delete Existing Loads: Deletes any and all distributed load assignments made to the selected object(s). When this option is selected, the items in the Load Type and Direction, Trapezoidal Loads, and Uniform Load areas of the form are ignored when the OK button is clicked.
Note that the default option is Replace and that the program defaults to this every time the form is opened.
Trapezoidal Loads. For trapezoidal loads, enter up to four locations and the corresponding load values in the appropriate units. The load will change abruptly at the first and fourth locations, and vary smoothly at the second and third locations. If more than four locations are needed, perform more assignment operations, using the Add to Existing Loads option.
Relative Distance from End-I or Absolute Distance from End-I. Specify that the distance from End I is relative or absolute for the location(s) specified in the Trapezoidal Loads area of the form.
Uniform Loads. For uniform loads (i.e., constant over the full length of the selected object), enter the load value in the Load edit box.
If uniform and trapezoidal loads are specified at the same time, they are additive.
Example: Assignment of a distributed frame load is demonstrated in Problem A, Problem H, Problem I, Problem K and Problem W.
See Also