T.T. Soong

Supplemental energy dissipation: State-of-the-art and state-of-the-practice

In recent years, considerable attention has been paid to research and development of structural control devices, with particular emphasis on alleviation of wind and seismic response of buildings and bridges. In both areas, serious efforts have been undertaken to develop the structural control concept into a workable technology, and today we have many such devices installed in a wide variety of structures. The focus of this state-of-the-art paper is on passive and active structural control systems. Passive systems encompass a range of materials and devices for enhancing structural damping, stiffness and strength. Active systems, which include active, hybrid and semi-active systems, employ controllable force devices integrated with sensors, controllers and real-time information processing. This paper includes a brief historical outline of their development and an assessment of the state-of-the-art and state-of-the-practice of this exciting, and still evolving, technology. Also included in the discussion are their advantages and limitations in the context of seismic design and retrofit of civil engineering structures.

State-of-the-art review: Active structural control in civil engineering

Abstract The objective of this paper is to provide a state-of-the-art assessment of active control research as applied to civil engineering structures. An attempt is made to present in with less specialized research content suitable for a more general readership. Recent activities in control algorithm development and control system design and practical aspects of their applications are summarized, followed by a discussion on possible future directions.

Parametric study and simplified design of tuned mass dampers

Abstract This paper summarizes the results of a parametric study performed to enhance the understanding of some important characteristics of tuned mass dampers (TMD). The effect of detuning on some of the TMD parameters on the performance is studied using steady-state harmonic excitation analysis and time-history analysis. The El Centro and Mexico excitations are used for time-history analysis. The effects of tuning criteria and significance of numerical tuning are also studied. The correspondence between the design of a TMD for a SDOF structure and a certain mode of a MDOF structure is drawn to simplify TMD design to control a single mode of a multimodal structure. An example is given to illustrate the design procedure. Investigations are made regarding controlling multiple structural modes using multi-tuned mass dampers (MTMD).

An Optimal Nonlinear Feedback Control Strategy for Randomly Excited Structural Systems

A strategy for optimal nonlinear feedback control of randomlyexcited structural systems is proposed based on the stochastic averagingmethod for quasi-Hamiltonian systems and the stochastic dynamicprogramming principle. A randomly excited structural system isformulated as a quasi-Hamiltonian system and the control forces aredivided into conservative and dissipative parts. The conservative partsare designed to change the integrability and resonance of the associatedHamiltonian system and the energy distribution among the controlledsystem. After the conservative parts are determined, the system responseis reduced to a controlled diffusion process by using the stochasticaveraging method. The dissipative parts of control forces are thenobtained from solving the stochastic dynamic programming equation. Boththe responses of uncontrolled and controlled structural systems can bepredicted analytically. Numerical results for a controlled andstochastically excited Duffing oscillator and a two-degree-of-freedomsystem with linear springs and linear and nonlinear dampings, show thatthe proposed control strategy is very effective and efficient.

Recent advances in active control of civil engineering structures

Abstract Active control systems for civil engineering structures have attracted considerable attention in recent years, because they may become effective protective systems. This paper reviews briefly the current state-of-the-art and summarizes some recent advances in active control of civil engineering structures both theoretically and experimentally.

State-of-the-art review. Active structural control in civil engineering

Abstract The objective of this paper is to provide a state-of-the-art assessment of active control research as applied to civil engineering structures. An attempt is made to present in with less specialized research content suitable for a more general readership. Recent activities in control algorithm development and control system design and practical aspects of their applications are summarized, followed by a discussion on possible future directions.

Optimal placement of energy dissipation devices for three-dimensional structures

In recent years, serious efforts have been undertaken to develop the concept of energy dissipation or supplemental damping into a workable technology, and a number of these devices have been implemented to structures in the US and elsewhere. As applications of this technology accelerate, an increasingly important issue is one of positioning these devices in a structure to maximize their effectiveness at minimum cost. This paper addresses this optimal placement problem when applied to structures where both translational and torsional responses are of major concern. Optimization procedures due to translation-torsion coupling effects or due to unsymmetrically placed devices are developed and verified through numerical examples. The effect of ground motion characteristics on the positioning of energy dissipation devices is also examined.

Seismic response of secondary systems

Abstract The purpose of this paper is to provide a comprehensive review and assessment of the state-of-the-art in the area of research on seismic response of secondary systems (structural and non-structural), which are anchored or attached to primary structural systems. Included are an appraisal of current engineering practice and design, an update of recent advances, and a discussion of possible future research direction.

Design of an active mass damper for a tall TV tower in Nanjing, China

The design of an active mass damper to reduce the effects of wind vibrations on a tall (340 m) communication tower in Nanjing, China is presented herein. The existing tower has excessive vibrations under the design wind loads, beyond the comfort level. The design of a mass damper needs to meet several constraints resulting from space, strength and power limitations. The selection of an active alternative for the mass damper is the result of economical and performance considerations within the specified constraints. The paper emphasizes the use of a single mode approach for the design evaluations vs the multi-modal approach. Nonlinear control strategies combined with the design constraints produce a feasible solution for the damper design. The paper emphasizes the system approach to the design in which the performance, the physical constraints and the implementation issues, such as power-force relations and frictional effects, are simultaneously considered. Neglecting any of the above issues may result in an inadequate solution.

Seismic behaviour of reinforced concrete frame with added viscoelastic dampers

Abstract This paper summarizes an experimental and analytical study on the seismic retrofit of a 1 3 - scale reinforced concrete frame using viscoelastic dampers. After the frame had been damaged in the laboratory under simulated strong earthquake ground motions, two sets of viscoelastic dampers were designed and implemented to the structure, and the frame was subjected to further simulated seismic excitations. Test results show that viscoelastic dampers are very effective in reducing the seismic response of reinforced concrete structures. In addition, the equivalent structural damping ratio can easily be predicted by the modal strain energy method with some modification. Therefore, seismic design of reinforced concrete structures with added viscoelastic dampers can be carried out similarly to conventional structural design procedures.