In SAP2000, when you use the SetMultiLinearPlastic command, DJ2 and DJ3 refer to the displacement limits in the multi-linear plasticity material model, specifically related to the plastic hinge behavior. These values are used to define the transition from elastic to plastic behavior.

Here's a breakdown of these parameters:

DJ2: This refers to the displacement at which the material behavior transitions from the elastic region to the start of the plastic region.

DJ3: This represents the displacement at which the material reaches its ultimate plastic capacity, after which the material will not exhibit further plastic deformation beyond this point.

These parameters help define the shape of the load-displacement curve for the material. The multi-linear plasticity model in SAP2000 allows for more complex and realistic modeling of non-linear material behavior, and DJ2 and DJ3 are key in defining the limits of this behavior.

To control SAP2000 via MATLAB, you'd typically use the SAP2000 API, which allows you to send commands and retrieve information. You can access and set these values using the API, but the exact syntax might vary based on your setup.