How can ELBOW elements be defined in Ansys Mechanical™ structural finite element analysis software?
Yes, though the following procedure -
First, create the beam model and define the beam's model type to "Pipe". Then, in the boundary conditions, add a "Pipe Idealization" condition. This will transform the mesh of selected edges from PIPE elements to ELBOW elements.
More information on Pipe Idealization can be found in the Ansys Help: Mechanical Applications / Mechanical User's Guide / Setting up boundary conditions / Types of boundary conditions / Conditions Type Boundary Conditions / Pipe Idealization.