The book begins with an introduction to active damping. It introduces active vibration control through the use of smart materials and structures (such as MR/ER fluids, shape memory alloys and piezoelectric materials), semi-active control devices, and a variety of feedback options. Examples employed include telescope vibration control and bridge cable damping. Vibration control methods and devices in civil structures are then discussed. An examination of active, passive and semi-active devices currently employed in vibration control and damping of civil structures is included. Modal analysis and the reduced-order physical modelling method for structural control are next presented. The authors then explore the spill over problem, a problem associated with reduced-order modelling of a structure in active control. The active control of buildings and bridge towers is examined, reporting on recent trends in active vibration control mainly as developed in Japan for civil structures. In the penultimate chapter, active tendon control of cable structures is addressed and the active damping of vibrations of the cable-stayed structures is investigated. The concluding chapter discusses the active and semi-active isolation in mechanical structures, including an exploration of active isolation and the increasing use of semi-active devices in responses to pressures to reduce weight and cost.