  Real-time hybrid testing is a method in which a substructure of the system is
realised experimentally and the rest numerically. The two parts interact in
real time to emulate the dynamics of the full system. Such experiments however
are often difficult to realise as the actuators and sensors, needed to ensure
compatibility and force-equilibrium conditions at the interface, can seriously
affect the predicted dynamics of the system and result in stability and
fidelity issues. The traditional approach of using feedback control to overcome
the additional unwanted dynamics is challenging due to the presence of an outer
feedback loop, passing interface displacements or forces to the numerical
substructure. We, therefore, advocate for an alternative approach, removing the
problematic interface dynamics with an iterative scheme to minimise interface
errors, thus, capturing the response of the true assembly. The technique is
examined by hybrid testing of a bench-top four-storey building with different
interface configurations, where using conventional hybrid measurement
techniques is very challenging. A case where the physical part exhibits
nonlinear restoring force characteristics is also considered. These tests show
that the iterative approach is capable of handling even scenarios which are
theoretically infeasible with feedback control.
