The objective of this PhD is to study the seismic behavior of elastic and inelastic structural systems equipped with viscous and viscoelastic dampers and develop design procedures according to Eurocode 8 for steel buildings.
Both types of dampers belong to the category of passive supplemental damping devices. These devices can be used either for new building or for retrofitting purposes of existing buildings. Dampers act by dissipating seismic energy and can significantly decrease the response of structural frame buildings subjected to earthquakes. Building drifts and member forces are substantially reduced by adding damping to the structure and thus both structural and non-structural components are protected. Viscoelastic dampers also add stiffness to the structure.
Viscous fluid dampers consist of a hollow cylinder filled with fluid, the fluid typically being silicone based. The damper is attached to the structure within chevron or diagonal bracing. As the damper piston rod and piston head are stroked, fluid is forced to flow through orifices either around or through the piston head. The resulting differential in pressure across the piston head very high pressure on the upstream side and very low pressure on the downstream side can produce very large forces that resist the relative motion of the damper.
Viscoelastic solid dampers generally consist of solid elastomeric pads viscoelastic material bonded to steel plates. The steel plates are attached to the structure within chevron or diagonal bracing. As one end of the damper displaces with respect to the other, the viscoelastic material is sheared resulting in the development of heat which is dissipated to the environment.
All the proposed literature covers the theory describing the behavior of the viscous or the viscoelastic dampers. Kasai et Fu (1996) present a design method for viscoelastic damped frames using a static equivalent force to estimate the dynamical force associated with viscoelastic damper response and considers the complex interaction between members and dampers. A 10-story steel moment resisting frame is designed with dampers by using the proposed method and also a nonlinear dynamic analysis is performed to compare the results.
Similarly and more detailed Kasai et al. (1998a) present the aforementioned simplified design method by comparing a viscoelastic damped system and a different type of damped passive system. Closed-form expressions for equivalent period and equivalent damping of these systems are proposed by idealizing them as linear single-degree-of-freedom systems. A 14-story steel moment resisting frame is upgraded by inserting viscoelastic dampers.
A comparative study of systems with viscoelastic and viscous dampers (Kasai and Fu 1998b) describes the mathematical models of these systems and expressions are derived for seismic response prediction. A 10-story steel moment resisting frame incorporated with viscoelastic and viscous dampers is analyzed to validate the...