In this paper, a new system of semi active structural control with active variable stiffness and damping (AVSD) issuggested. This new system amplifies the structural displacement to dissipate more energy, and in turn, effectively reduces thestructural response in the case of relatively small story drifts, which occur during earthquakes. A predictive instantaneousoptimal control algorithm is established for a SDOF structure equipped with an AVSD system Comparative shaking table testsof a 1/4 scale single story structural model with a full scale control device have been conducted. From the experimental andanalytical results, it is shown that when compared to structures without control or with the active variable stiffness control alone,the suggested system exhibits higher efficiency in controlling the structural response, requires less energy input, operates withhigher reliability, and can be manufactured at a lower cost and used in a wider range of engineering applications.