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Earthquakes have always been a menace to the lives and properties of human beings since the beginning of modern times. Several methods have been proposed since to mitigate the various types of seismic hazards, base isolation being one of them. The base-isolated structures being very effective for general far-fault earthquakes, are, however susceptible to high responses under near-fault ground motions; thus, several inerter-based supplementary damping devices have been proposed in this study to be applied alongside a highly nonlinear and effective unbonded fiber-reinforced elastomeric isolators (UFEI) system. The dampers are optimally designed and comparatively investigated with the isolation system for mitigation of a wide range of ground motions to the benchmark structure. Furthermore, two parametric studies were also carried out, which investigated the effect of the inertance-mass ratio and floor connectivity of the grounded damper on various responses of the isolator-damper-structure system. The parametric results are further used to suggest the best configuration and inertance-mass ratios for various dampers for effective seismic mitigation of the aforementioned base-isolated structure. The results show an effective reduction in seismic responses with the use of optimal inerter-based dampers in UFEI-isolated structures.

Research and development of seismic response control devices has gained prime importance recently, due to an increased number of devastating earthquakes. Passive control systems are now accepted all over the world and hence research in this area is continuing to develop reliable, efficient and cost effective devices along with constitutive modeling. This paper begins with qualitative description and comparison of passive, active and semiactive control systems. Further, it mentions advantages of passive control systems over the others. A detailed literature review of passive devices is then provided which includes the historical development of the devices, their dynamic behavior, testing of these devices incorporated in the structural models and their analytical formulations. The pros and cons of these devices in retrofitting of structures and their first and recent applications in a wide variety of structures are also discussed. The passive response control systems that are discussed include viscoelastic dampers, yielding dampers, viscous dampers, friction dampers, tuned mass dampers, tuned liquid dampers, tuned liquid column dampers, superelastic dampers, like shape memory alloy dampers and base isolators.

Recently, applying damped outriggers in high-rise buildings to reduce vibration due to earthquake and wind has attracted a lot of attention. By placing energy dissipated devices vertically between the end of outriggers and perimeter columns, the damped outrigger systems emphasize the supplementary damping rather than stiffness. This paper investigates the applicability of viscously damped outrigger systems using Timoshenko beam theory. First, the building is modeled as a cantilevered Timoshenko beam, and the damped outriggers are simplified as equivalent complex rotational spring. With the assembly of dynamic stiffness of the damped outrigger system, the Wittrick–Williams algorithm and Newtonian iteration are then combined to calculate the dynamic characteristic of the system. The proposed approach has been verified by finite element method through a case study. The shear deformation and rotatory inertia of the core, later blended as slenderness ratio of the height-radius following Timoshenko beam theory, stiffness ratios of core-column and core-outrigger, and the number of damped outriggers are subsequently evaluated associated with supplementary damping as applicability analysis. This study shows the following: (1) adding damping amplifies twice to triple as the slenderness ratio increases from 5 to 25 for the first mode; (2) configurating more damped outriggers could provide stable damping contribution across modes with diminishing benefit; (3) Timoshenko beam analysis is better suited while Euler–Bernoulli beam analysis is an acceptable approximation only when the slenderness ratio of one-damped outrigger system is bigger than 25 and the first mode is predominant; and finally (4) the stiffness ratios of core-column, core-outrigger and stiffness of dampers have substantial influence on structural damping, particularly within the range smaller than 1, 10 and 4, respectively, but the presence of properly designed negative stiffness of dampers could bring substantial improvement. This study could serve as guidelines to apply damped outrigger systems in high-rise buildings.

Japan has twenty years of experience in designing and constructing base-isolated building structures. Construction has increased significantly since the 1995 Hyogoken-Nanbu (Kobe) earthquake, having reached over 150 annual construction projects. Many new developments and refinements have been made in the material, device, design, and construction of these structures. This paper summarises recent design and construction of base-isolated building structures in Japan, including statistical data with respect to the common usage as well as the number of new projects. It is notable that the size, height, and fundamental natural period of new base-isolated buildings increase steadily with time, indicating that base-isolation in Japan is reaching maturity. Base-isolators and dampers commonly adopted in Japan are also introduced, with emphasis on recent design efforts to enlarge the natural period of base-isolated structures and reduce the lateral forces induced in the superstructure. Basic design procedures are presented, including determination of design earthquake forces, modelling of base-isolation layers, modelling of the superstructure, selection of ground motions, time-history analyses, and performance criteria. A mandated peer-review system, unique for design of base-isolated structures, is also noted. Several characteristic issues in the design of base-isolated structures are discussed: Variation of base-isolation material properties, applications to high-rise buildings, effects of vertical ground motions, and response when subjected to near-fault ground motions.

Cable-stayed bridges exhibit unique responses under a strong motion. It is partly due to the complexity in their damping mechanism. Recently, the benchmark problem of a cable-stayed bridge was developed to clarify the effectiveness of various seismic control strategies. Due to the new development of magnetorheological dampers, the application of variable dampers in bridges becomes possible. In this study, the effectiveness of the nonlinear viscous damping force scheme and the two-step friction damping force scheme are investigated. It is found that the nonlinear viscous damping force scheme is effective to control the response of the cable-stayed bridge with less demand for the damping force capacity of a damper. In addition, the two-step friction damping force scheme shows the improvement over conventional friction damping because the energy dissipation of a damper can be increased.