Active TLCGD control of plane asymmetric buildings under earthquake excitation

The sealed,tuned liquid column gas damper （TLCGD） with gas-spring effect extends the frequency range of application and efficiently increases the modal structural damping.Active tuned liquid column gas damper （ATLCGD） is developed for the vibration control of plane asymmetric buildings subjected to earthquake excitation,improving the performance of the passive control scheme.The active behaviour is obtained by adjusting the pressure at the end of the liquid column using a pressurised reservoir.The classical linear quadratic regulator （LQR） design is presented as a straightforward approach to optimal control.Numerical simulations indicate a significant vibration reduction of plane asymmetric buildings by active control within the strong motion of the dynamic response.

Karhunen-loéve expansion for random earthquake excitations

This paper develops a trigonometric-basis-fimction based Karhunen-Loeve （KL） expansion for simulating random earthquake excitations with known covariance functions. The methods for determining the number of the KL terms and defining the involved random variables are described in detail. The simplified form of the KL expansion is given, whereby the relationship between the KL expansion and the spectral representation method is investigated and revealed. The KL expansion is of high efficiency for simulating long-term earthquake excitations in the sense that it needs a minimum number of random variables, as compared with the spectral representation method. Numerical examples demonstrate the convergence and accuracy of the KL expansion for simulating two commonly-used random earthquake excitation models and estimating linear and nonlinear random responses to the random excitations.

Bending vibration analysis of rotating machineries using multibody dynamics technology — development of computer program RotB

This paper examines a computer program developed to analyze the vibration of rotating machineries based on theories of vibration and multibody dynamics （MBD）. Bending vibration problems of rotating machineries have generally been categorized as either linear or nonlinear. Linear problems can be formulated by standard methods and nonlinear problems can be formulated by MBD methods. In our study, nonlinear problems are treated by the use of a general-purpose computer program, RecurDyn （RD）. In the program we developed, rotor bending vibration analysis （RotB） structural properties such as shafts, rotating rotary disks, unbalanced masses and foundation structures are modeled as multibody elements. Also, nonlinearities such as contact, non-symmetrical shaft effects, bearing characteristics, nonlinear restoring and damping characteristics in the bearings are taken into account. The computational results demonstrate the validity of RotB.

Parametric control of structural responses using an optimal passive tuned mass damper under stationary Gaussian white noise excitations

In this study,the structural control strategy utilizing a passive tuned mass damper(TMD)system as a seismic damping device is outlined,highlighting the parametric optimization approach for displacement and acceleration control.The theory of stationary random processes and complex frequency response functions are explained and adopted.For the vibration control of an undamped structure,the optimal parameters of a TMD,such as the optimal tuning frequency and optimal damping ratio,to stationary Gaussian white noise acceleration are investigated by using a parametric optimization procedure.For damped structures,a numerical searching technique is used to obtain the optimal parameters of the TMD,and then the explicit formulae for these optimal parameters are derived through a sequence of curve-fitting schemes.Using these specified optimal parameters,several different controlled responses are examined,and then the displacement and acceleration based control effectiveness indices of the TMD are examined from the view point of RMS values.From the viewpoint of the RMS values of displacement and acceleration,the optimal TMDs adopted in this study shows clear performance improvements for the simplified model examined,and this means that the effective optimization of the TMD has a good potential as a customized target response-based structural strategy.