Supplemental Energy Dissipation and Structural Control
An alternative and often more cost efficient retrofitting strategy compared to base isolation is installation of supplemental energy dissipation devices in structures as a means for passive or active structural control. The objective of structural control is to reduce structural vibrations for improved safety and/or serviceability under wind and earthquake loadings. Passive control systems reduce structural vibration and associated forces through energy dissipation devices that do not require external power. These devices utilize the motion of the structure to develop counteracting control forces and absorb a portion of the input seismic energy. Active control systems, however, enhance structural response through control forces developed by force delivery devices that relyon external power to operate. The actuator forces are controlled by real time controllers that process the information obtained from sensors within the structure. Semi-active control systems combine passive and active control devices and are sometimes used to optimize the structural performance with minimal external power requirements. Fig. 7 shows the basic principles of various control systems commonly used to control wind and seismic forces acting on building structures.An alternative and often more cost efficient retrofitting strategy compared to base isolation is installation of supplemental energy dissipation devices in structures as a means for passive or active structural control. The objective of structural control is to reduce structural vibrations for improved safety and/or serviceability under wind and earthquake loadings. Passive control systems reduce structural vibration and associated forces through energy dissipation devices that do not require external power. These devices utilize the motion of the structure to develop counteracting control forces and absorb a portion of the input seismic energy. Active control systems, however, enhance structural response through control forces developed by force delivery devices that relyon external power to operate. The actuator forces are controlled by real time controllers that process the information obtained from sensors within the structure. Semi-active control systems combine passive and active control devices and are sometimes used to optimize the structural performance with minimal external power requirements. Fig. 7 shows the basic principles of various control systems commonly used to control wind and seismic forces acting on building structures. The severity of seismic demand on a structure is proportional to its stiffness and inversely proportional to its damping or energy dissipation capacity. Thus, installing supplemental energy dissipating devices in the structure reduces the seismic demand and results in increased safety of the structure and its contents from the damaging effects of earthquakes.
In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on improving wind and seismic response of buildings and bridges. In both areas, efforts have been made to develop the structural control concept into a workable technology, and as a result, such devices have been installed in a variety of structures around the world. The most challenging aspect of vibration control research in civil engineering is the fact that this is a field that requires integration of a number of diverse disciplines, some of which are not within the domain of traditional civil engineering. These include computer science, data processing, control theory, material science, sensing technology, as well as stochastic processes, structural dynamics, and wind and earthquake engineering. These coordinated efforts have facilitated collaborative research among researchers from a diverse background and have accelerated the research to the implementation process. Continued research is essential in this area to develop effective and affordable retrofitting solutions for structures with insufficient seismic resistance. A special concern regarding the use of energy dissipation devices in structures with high characteristic variability is the fact that the effectiveness of such devices is dependent on the deformation capacity of the structure. For structures that suffer from inadequate seismic detailing, which translates into insufficient deformation capacity, great caution must be exercised in use of these devices for seismic retrofitting. A feasible solution may be to combine this technique with deformation enhancement measures to ensure their effectiveness. This constitutes an important research area with valuable potential contribution and high potential benefits.
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SEISMIC RETROFITTING
SEISMIC RETROFITTING TECHNIQUES
BASE ISOLATION
EFFECTS OF SEISMIC RETROFITTING ON STRUCTURAL PERFORMANCE
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