“…Examples of such devices that have been considered for civil engineering applications include: variable orifice dampers [9,26,29,34,36,38], controllable friction braces [1,10], controllable friction isolators [19], variable stiffness devices [27], and electrorheological (ER) dampers [2,17,18,21,30,32]. The effectiveness of one semi-active control system employing a variable stiffness system has already been proven in a low-rise building in Japan [28].…”