Izuru Takewaki

The purpose of this paper is to propose an efficient and systematic procedure for finding the optimal damper placement to minimize the sum of amplitudes of the transfer functions evaluated at the undamped fundamental natural frequency of a structural system subject to a constraint on the sum of the damping coefficients of added dampers. Optimality criteria are derived and the optimal damper placement is determined based upon those criteria without any indefinite iterative operation. The present

The resonant behaviour of base-isolated high-rise buildings under long-period ground motions is investigated. The long-period ground motions are known to be induced by surface waves. While the acceleration amplitude of such long-period ground motion is small, the velocity amplitude is fairly large. It is expected that high-rise buildings and base-isolated buildings with long fundamental natural periods are greatly influenced by these long-period ground motions. Especially base-isolated high-rise

Fundamental mechanisms of earthquake response reduction in building structures with inertial mass dampers are investigated. The inertial mass damper is effective with respect to relative acceleration between two nodes. The influence of inertial mass dampers on the ground-motion input can be expressed by the influence coefficient vector to be multiplied on the ground-motion acceleration in the right-hand side of the equations of motion. It is shown that, when an inertial mass damper is taken out

A new general critical excitation method is developed for a damped linear elastic single-degree-of-freedom structure. In contrast to previous studies considering amplitude nonstationarity only, no special constraint of input motions is needed on nonstationarity. The input energy to the structure during an earthquake is introduced as a new measure of criticality. It is shown that the formulation of earthquake input energy in the frequency domain is essential for solving the critical excitation pr

An efficient and systematic procedure is proposed for finding the optimal damper positioning to minimize the dynamic compliance of a 3-D shear building model. The dynamic compliance is expressed in terms of the transfer function amplitudes of the local interstorey drifts evaluated at the undamped fundamental natural frequency. The dynamic compliance is minimized subject to a constraint on the sum of the damping coefficients of added dampers. Optimality criteria are derived and the optimal damper

A critical review of methods for critical excitation (worst-case input) is presented to enhance the robustness of structural design of aerospace, mechanical, and civil engineering structures. These structures are often subjected to disturbances including inherent uncertainties due mainly to their occurrence scarcity and worst-case analysis is expected to play an important role in avoiding difficulties induced by such uncertainties. During the last three decades, various critical excitation metho

An efficient and systematic procedure is proposed for finding the optimal damper positioning to minimize the dynamic compliance of a planar building frame. The dynamic compliance is expressed in terms of the transfer function amplitudes of the interstory drifts evaluated at the undamped fundamental natural frequency. The dynamic compliance is minimized subject to a constraint on the sum of the damping coefficients of added dampers. Optimality criteria are derived and the optimal damper positioni

Abstract Since earthquake ground motions are very uncertain even with the present knowledge, it is desirable to develop a robust structural design method taking into account these uncertainties. Critical excitation approaches are promising and a new non‐stationary random critical excitation method is proposed. In contrast to the conventional critical excitation methods, a stochastic response index is treated as the objective function to be maximized. The power (area of power spectral density (PS