Optimal Damper Placement Research Articles

Optimal damper placement for critical excitation

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 probabilistic critical excitation method is proposed. Different from the conventional critical excitation methods, a stochastic response index is treated as the objective function to be maximized. The energy (area of power spectral density function) and the intensity (magnitude of power spectral density function) are fixed and the critical excitation is found under these restrictions. It is shown that the resonant characteristic of ground motions can be well represented by the proposed critical excitation. An original steepest direction search algorithm due to the present author is applied to the problem of optimal damper placement in structures subjected to the critical excitation. Closed-form expressions of the inverse of the coefficient matrix (tri-diagonal matrix) enable one to compute the transfer function and its derivative with respect to design variables very efficiently. A numerical example of a 6-DOF shear building model is presented to demonstrate the effectiveness and validity of the present method.

Optimal damper placement for building structures including surface ground amplification

A systematic method for optimal added damper placement in building structures is developed, taking into account the response amplification due to the surface ground. Non-linear amplification of the surface ground is described by an equivalent linear model. Hysteretic damping of the surface ground and radiational damping into the semi-infinite visco-elastic ground are included in the model. An original steepest direction search algorithm is applied to the interaction model. Closed-form expressions of the inverse of the coefficient matrix (tri-diagonal matrix) enable one to compute the transfer function and its derivative with respect to design variables very efficiently. It is shown that the ratio of the fundamental natural period of the structure to that of the surface ground is a key parameter for characterizing the optimal damper placement. Several examples for different soil conditions are presented to demonstrate the effectiveness and validity of the present method.

Optimal Use of Viscoelastic Dampers in Building Frames for Seismic Force

Control of the seismic response of multistory building frames using optimally placed viscoelastic dampers (VEDs) is investigated. Responses are obtained in frequency domain using spectral analysis for narrow and broad band stationary random ground motions. Optimal locations of passive VEDs are found with the help of a controllability index, which is obtained with the help of the root-mean-square value of the interstory drift. To highlight the effect of modeling and optimal location of VEDs on the response reduction, three different mathematical models of the VEDs and three alternative schemes of placement of VEDs are considered. The response of the 20-story shear-frame model is controlled by the proposed strategy. It is shown that the scheme of the optimal placement of VEDs provides more reduction in response compared with other schemes of placement of VEDs considered in the study. Furthermore, the optimal placement of dampers is sensitive to the nature of excitation force, total quantity of viscoelastic material used, and the modeling of VEDs.

Effects of support stiffnesses on optimal damper placement for a planar building frame

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 positioning is determined via an original steepest direction search algorithm. This algorithm enables one to find an optimal damper positioning sequentially for gradually increasing damper levels. The influences of support-member stiffnesses on the response suppression level and on the optimal damper positioning are also disclosed numerically. Copyright © 1998 John Wiley & Sons, Ltd.

Effects of support stiffnesses on optimal damper placement for a planar building frame

Effects of support stiffnesses on optimal damper placement for a planar building frame

Optimal damper placement for minimum transfer functions

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 procedure can be applied to any structural system so far as it can be modelled with finite-element systems. The present procedure also enables one to treat structural systems with an arbitrary damping system (for example, proportional or non-proportional) in a unified manner. Due to employment of a general dynamical property, i.e. the amplitude of a transfer function, the results are general and are not influenced by characteristics of input motions. © 1997 John Wiley & Sons, Ltd.