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The effective way of allocation of viscous oil dampers (capacity or size) is believed to place dampers to the stories which exhibit large interstory drifts. It is shown here that, while this understanding is almost true in rather low or medium-rise buildings, the distribution of the maximum interstory velocities plays a critical role in super high-rise buildings. It is further demonstrated that a large distribution of the maximum interstory velocities can be observed in lower stories in super high-rise buildings and this leads to a large demand of the maximum damping force in lower stories. It is concluded that the demand of relief forces of oil dampers is expressed in terms of (a) the maximum story shear forces of a frame without oil dampers which can be evaluated by the response spectrum method or other conventional methods, (b) the damper damping ratio, (c) the damping correction factor and (d) the higher-mode correction factor.

The purpose of this paper is to propose a practical method for optimum design of non-linear oil dampers with relief mechanism installed in multi-story framed building structures. The optimum design problem is formulated so as to minimize the maximum interstory drift or maximum acceleration of top-story under design earthquakes in terms of a set of relief forces subject to an inequality constraint on the maximum ratio of the damping force to the relief force and an equality constraint on the sum of relief forces of oil dampers. The proposed method to solve the optimum design problem is a successive procedure which consists of two steps. The first step is a sensitivity analysis by using nonlinear time-history response analyses, and the second step is a modification of the set of relief forces based upon the sensitivity analysis. An advanced reduction method based on static condensation of the frame and energy equivalence transformation of oil dampers is proposed and introduced into the optimum procedure to reduce the computational load. Numerical examples are conducted to demonstrate the effectiveness and validity of the proposed design method.

A new vibration control system including viscoelastic or viscoplastic rubber dampers is proposed for residential houses. This system consists of braces and a damper unit including a high-hardness rubber damper or a linear rubber damper. The high-hardness rubber damper possesses many unprecedented properties such as large stiffness, small temperature and frequency dependencies compared to most of usual viscoelastic dampers. Post tensioning forces are introduced into the braces to reduce small gap in joint parts and this system has high damping performance for micro-vibration. The control system can absorb sufficient energy through the high-rubber damper and post tensioning braces. A concept is introduced called an effective deformation ratio, i.e. the ratio of the actual damper deformation to the interstory drift of the frame, as a criterion to measure the damping performance and effectiveness of this system. To find out principal parameters that affect greatly the effective deformation ratio of the proposed new vibration control system, an incremental analysis method taking into account the geometrical and material nonlinearities is developed to simulate the main characteristics of this vibration control system. The accuracy of the analysis method is investigated through the comparison with the results by two simple analysis methods. The comparison with the experimental result is also conducted for further investigation.

An enhanced reduced model is proposed for elastic earthquake response analysis of a class of mono-symmetric shear building structures with constant eccentricity. The proposed reduction method consists of two parts. The first stage is the construction of a reduced structural model with the degrees of freedom at representative floor levels only. In this stage, an inverse eigenmode-problem formulation is used to guarantee the limited equivalence between the original model and the reduced model. The reduced model is constructed so as to have the same fundamental natural frequency and the same lowest-mode component ratios at the representative floor levels as those of the original model. The second stage is the transformation of earthquake input forces into a set of reduced input forces. This transformation utilizes the static equivalence of lateral-torsional stiffness between these two models and is introduced to enhance the accuracy level of the reduced model. Several examples of a three-dimensional mono-symmetric ten-story shear building model with constant eccentricity are presented to demonstrate the validity and accuracy of the proposed reduction method for earthquake response analysis.

High-hardness viscoelastic rubber dampers are used to upgrade both the habitability environment and the structural safety in high-rise buildings subjected to wind disturbances. While most of usual viscoelastic dampers have limitation on temperature and frequency dependencies, etc., the proposed high-hardness viscoelastic rubber dampers possess many unprecedented properties. High hardness, large stiffness, small temperature and frequency dependencies are examples of such properties. Mechanical modelling of the proposed high-hardness viscoelastic rubber dampers is introduced first, and the wind-induced response of high-rise buildings with and without the proposed high-hardness viscoelastic rubber dampers is computed under dynamic horizontal loads derived from wind tunnel tests. It is shown that high-rise buildings with the proposed high-hardness viscoelastic rubber dampers exhibit extremely smaller wind-induced responses (both along-wind and cross-wind responses) than those without such dampers. In particular, a remarkable reduction of acceleration has been achieved owing to sufficient hysteresis even in the small strain range. It is concluded that the proposed high-hardness viscoelastic rubber dampers can upgrade the habitability environment of building structures dramatically.

The purpose of this paper is to propose a simple analysis method of axial deformation of base-isolation rubber bearings in a building subjected to earthquake loading and present its applicability to the analysis of the bound of the aspect ratio of base-isolated buildings. The base shear coefficient is introduced as a key parameter for the bound analysis. The bound of the aspect ratio of base-isolated buildings is analyzed based on the relationship of the following four quantities; (i) ultimate state of the tensile stress of rubber bearings based on a proposed simple recursive analysis for seismic loading, (ii) ultimate state of drift of the base-isolation story for seismic loading, (iii) ultimate state of the axial compressive stress of rubber bearings under dead loads, (iv) prediction of the overturning moment at the base for seismic loading. In particular, a new recursive analysis method of axial deformation of rubber bearings is presented taking into account the nonlinear tensile behavior of rubber bearings and it is shown that the relaxation of the constraint on the ultimate state of the tensile stress of rubber bearings increases the limiting aspect ratio.