Definition and Examples of Functionally Upgraded Passive Devices

The research field of structural control has evolved from the development of passive devices since 1970s, through the intensive investigation on active systems in 1980s, to the recent studies of semi-active and hybrid control systems in 1990s. Currently semi-active control is considered most promising in civil engineering applications. However, actual implementation of semi-active devices is still limited due mainly to their system maintenance and associated long-term reliability as a result of power requirements. In this paper, the concept of functionally upgraded passive devices is introduced and clearly defined. They can mimic the function of their corresponding semi-active control devices for various applications. They have clearly-defined counterparts, conventional passive devices, but with superior performance in certain functions. They require virtually no maintenance in applications and expect to gain wide acceptance in engineering practices