This paper describes the development of a numerical model to predict the behaviour of a semi-active resettable tendon during seismic testing. Two resettable tendons were installed as lateral bracings in a four-storey one-fifth scale structure to reduce its seismic response. The test structure was subjected to different simulated earthquake ground motions at various peak ground accelerations. Different control configurations for the resettable tendon were used to test the one-fifth scale structure on the shaking table. The analytical model has three primary components: a resettable device, a steel tendon and a steel restraint. Assumptions adopted for the analytical modelling of the semi-active resettable tendon are described. Nonlinear dynamic analyses were performed to assess the accuracy of the mathematical model. Displacement time-histories at the third floor of the test structure are used to compare the analytical and experimental results. It is shown that the analytical simulations can closely reproduce the experimentally observed behaviour of the structure.