Effective Force Testing (EFT) is a method which enables real-time earthquake simulation studies of large-scale test structures under load control. Other testing methods have limitations including specimen size, power requirements, or complex control algorithms to achieve real-time response. As opposed to the pseudodynamic test method (a displacement-based control procedure), there is no computational time required for the EFT method in determining the input command signal; it is known prior to the test, once the structural mass and ground acceleration record to be simulated are determined. Research has been conducted on a single-degree-of-freedom system to investigate the potential and limitations of the EFT method. A direct application of the EFT method was found ineffective because the actuator was unable to apply force at the natural frequency of the structure due to actuator/control/structure interaction. However, numerical simulations indicated that an additional velocity feedback loop incorporated in the control system can overcome this problem.