The seismic behavior of a novel steel beam-to-concrete-filled steel tubular column connection with external diaphragms was evaluated numerically by using a model based on the finite element method. The model was validated against experimental results performed in previous work, which revealed that this type of connection is suitable for use in special moment frame structures located in areas of high seismic threat. The comparison included the hysteresis curve, plasticization mechanism, and plastic hinge location. Then, the model was used to study the behavior of the connection for a monotonic test. It was observed that the monotonic test can be used for the qualification of the connection, avoiding the excessive time required for the solution of the cyclic load test. In addition, two stages of simplifications were conducted in the model, showing satisfactory results and significant reductions in computational time. For the first stage, the lateral support beam was removed and replaced by a connection with an infinite lateral rigidity. Second, beam-type elements were implemented in the remote areas of the plastic hinge location. Finally, the simplified model was used in a parametric study that examined the behavior of the connection under four different European type I profiles. It was observed that all the profiles meet the requirements for seismic performance.