Design of seismic energy dissipation systems for reinforced concrete and steel structures

It is now well known that there is a relationship between inelastic deformation and energy dissipation in structures that are subjected to earthquake ground motions. Thus, if seismic energy dissipation can be achieved by means of separate non-load bearing supplementary damping devices, the load bearing structure can remain elastic for the design and with continuing serviceability for the maximum credible earthquake ground motions. With this objective in mind, the study reported in this dissertation presents experimental and analytical investigations of seismic response of reinforced concrete and steel structures with nonlinear supplementary damping devices. Various supplemental system configurations are conceived, analytically studied and verified through shaking table experiments.; Two experimental studies to investigate the seismic behavior of model structures under the simulated ground motions are described. It is argued that damper distribution should be based on: (i) either the interstory deformations or story shears, and (ii) the overturning moments generated by the lateral inertia loads. The former method was implemented in a non-ductile reinforced concrete frame, while for the latter method an innovative prestressed load-balancing tendon system was introduced and approximate alternatives were experimentally explored on a model steel structure. This load-balancing supplemental system consists of prestressed-draped tendons in the shape of the overturning moment diagram. The tendons are connected in series with the nonlinear dampers and sacrificial fuse-bars.; Based on the notion of a normalized damper capacity, a simplified design methodology based on the capacity-demand spectral approach is advanced. The approach transforms non-linear damper and fuse-bar systems into equivalent viscous damping using an equivalent power consumption formulation. The simplified design philosophy is verified through a retrofit case study on a nine-story steel moment frame building.; It is concluded that the load-balancing tendon-fuse+damper system is an appropriate cost-effective method of mitigating the earthquake induced demands on a steel frame. By careful detailing, it is possible to ensure that under design earthquake loads the structure should remain elastic, while under maximum credible motions fracture of the steel frame welded connections can be avoided.