The joint is an idealization of the real connection, but the joint measured the peak force (three components) that went through the joint during the earthquake. Probe the joint to obtain those measurements.

Build a Static Structural detailed model of the real connection around that point in the structure. Apply the force components measured at the joint to the same location in the detailed model.  You can eliminate the stress concentration in the detailed model by using frictional contact to spread the load over an area.