What Does a Distributed Load Do?
A distributed load is a load that is applied over the length of a beam element. A distributed load can be applied in any direction specified by a vector.
For the distributed load to be applied to your model, you must assign a "Pressure" multiplier in the "Multipliers" tab of the "Analysis Parameters" dialog. The product of the "Magnitude" and the "Pressure" multiplier will the magnitude of the distributed load.
Applying a Distributed Load:
If you select one or more beam elements using the "Selection: Select: Lines" command and right click in the display area, you can select the "Add" pull-out menu and select the "Beam Distributed Loads..." command to add a distributed load to each beam element.
If the magnitude and direction of the load will be constant across the length of each selected beam, specify the magnitude of the load per unit of length in the "Magnitude" field and the direction of the load in the "Direction" section. If the magnitude or direction of the load will vary across the length of the each selected beam, deactivate the "Uniform" checkbox and specify the magnitude of the force per unit of length at each end in the "I-Node Magnitude" and "J-Node Magnitude" fields and the direction in the "I-Node Direction" and "J-Node Direction" sections. The magnitude of the load will vary linearly between the nodes. This will be done on a per-beam basis.
If you are applying a non-uniform load to the beam, you can have the load start and end at any point along the beam. This will be done by specifying a ratio of the length of the beam in two "ratio from I-Node" fields. The first field will determine how far from the I-Node the load starts. The second field will determine how far from the I-Node the load ends. For example, if you want a load to be applied only along the third-quarter of a beam, you would specify 0.5 in the first field and 0.75 in the second field.
The axis 1 orientation of the beam elements can be displayed using the "View: Options: Element Orientations: Axis 1" command. If axis 1 needs to be reversed for some elements, this can be done by selecting the elements ("Selection: Select: Lines"), right-clicking, and choosing "Beam Orientations: Invert I and J Nodes".