Passive dampers are used recently in many mid and high-rise buildings. This trend is accelerated by the increased demand and desire for safer, more reliable and more comfortable buildings under uncertain external loading and environment. Viscous, visco-elastic, hysteretic and friction dampers are representatives of passive dampers. Such passive dampers also play a key role in the implementation of structural rehabilitation which is essential for the realization and promotion of sustainable buildings. The technique of structural health monitoring is inevitable for the reliable and effective installation of passive dampers during the structural rehabilitation or retrofit. The design earthquake ground motions change from time to time when a new class of ground motions (e.g. long-period ground motions due to surface waves) is observed or a new type of damage appears during severe earthquakes. The concept of critical excitation is useful in responding to this change together with the usage of passive dampers from the viewpoint of sustainable buildings and cities. In this paper, a historical review is made on the development of smart or optimal building structural control with passive dampers and some possibilities of structural rehabilitation by use of passive dampers are discussed.

SUMMARYThe paper under discussion presents a detailed study on the reduction of pounding force on buildings due to expansion joints being filled with rubber. From shake table experiments and numerical simulations, the authors of the paper concluded that the rubber can reduce the maximum pounding force and hence the pounding damage to buildings. However, the writers of this short communication observed some significant issues in the experimental results as well as the numerical simulations. These observations are presented and raise questions about the validity of the results and the subsequent conclusions.

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This paper discusses the exactness of a simplified analytical method proposed by Takabatake et al. (1993) to use in preliminary stages of the design to doubly symmetric single and double frame-tubes in high-rise structures. The simplified method is formulated by replacing the tube with an equivalent rod, including the effect of the bending, transverse shear deformation, shear-lag and torsion. The discontinuous variation of sectional stiffness of tube structures, due to the variation of frame members and attached braces, is expressed as a continuous function by means of the extended Dirac function. The exactness of the closedform solutions proposed here for the deflection, shear-lag, and torsional angle of variable tube structures with braces is established from static and dynamic numerical results for doubly symmetric single and double frame-tubes with braces, in which the results obtained from the proposed solutions are compared with results obtained from three-dimensional frame analysis using the FEM codes NASTRAN and DEMOS.