摘要:

AbstractAn active tendon control system for civil engineering cable‐supported structures is proposed. The technique is based on a tendon actuator collocated with a force sensor. A large‐scale mock‐up using industrial components has been built and widely tested. The test‐bed is a model of cable‐stayed bridge during its construction phase, equipped with hydraulic actuators on the two longest stay‐cables. The results of several damping experiences are presented; they clearly demonstrate the efficiency of the active damping system. The proposed technology is directly applicable to real structures by scaling up

ISSN:1122-8385    

DOI:10.1002/stc.4300080201

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractIn the paper the non‐linear nature of the dynamics of a simple structural model including pseudo‐elastic SMA members is dealt with. The purpose is to prove that pseudo‐elastic behaviour, which structural patterns can be provided with by the introduction of SMA devices, is able to neutralise most of the dangerous phenomena produced by theP— Δ effect; this includes a high sensitivity to possible asymmetry in the strength of the structure; a problem that has been rarely treated in the literature. The numerical investigation carried out with relation to the SMA modified structural system and to a simple elastic perfectly plastic model, shows that the adoption of SMA inclusions determines an immediate structural response stabilisation (even in case of asymmetric resistance of the model), while failing the classical system remains prone to

ISSN:1122-8385    

DOI:10.1002/stc.4300080202

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractIn this paper the seismic response of base isolated structures with high damping laminated rubber bearings is evaluated. The analysis is based on a stochastic approach and the seismic acceleration is modelled through a Gaussian zero mean non stationary stochastic process. More precisely, the recent generalized Kanai‐Tajimi model proposed by Fan and Ahmadi for the El Centro 1940 N00W and Mexico City 1985 N90W earthquakes is used to preserve the non stationary amplitude and frequency characteristics of the seismic motion.The non linear constitutive behaviour of the base isolator is represented by the hysteretic differential Bouc‐Wen model. The stochastic linearization method in the time domain is used to evaluate the statistical moments of the system response in the state space. The non linear differential equation of the response covariance matrix is solved by using an iterative procedure which at each step updates the coefficients of the equivalent linear system and searches for the solution of the response covariance matrix equation. To assess the accuracy of the results, these are compared with the non linear response obtained by using seismic accelerations generated with Monte Carlo simulation. Finally, the peaks of the system response variance are estimated and a sensitivity analysis is perfor

ISSN:1122-8385    

DOI:10.1002/stc.4300080203

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractIn this paper different types of rubber bearings are considered and their properties are described. Stiffness‐damping interconnection for each type of bearing is obtained. The investigated relationships are based both on graphs of stiffness and damping versus shear strain and on experimental hysteresis loops. Relationships between stiffness and damping allow understanding of some regular lows mentioned in the conclusion

ISSN:1122-8385    

DOI:10.1002/stc.4300080204

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

ISSN:1122-8385    

DOI:10.1002/stc.4300080205

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractRecurrent formulas are derived to determine stress tensors and displacement vectors for compressible and incompressible plate‐like foundations. A three‐layered plate with an incompressible middle layer is considered as an example of practical significance for seismostable constructions. Nonlinear problems for strip‐seismoisolators from incompressible materials are disc

ISSN:1122-8385    

DOI:10.1002/stc.4300080206

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractVibrations of plate‐like bases, foundations and seismoisolators caused, in particular, by seismic loading are studied. Asymptotic solutions of relevant dynamic equations of elasticity theory are constructed. Resonance conditions are derived, ways to avoid hazardous resonances are discusse

ISSN:1122-8385    

DOI:10.1002/stc.4300080207

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractPrinciples of vibration control based on the use of shape memory alloys (SMAs) are discussed. Control feasibilty is due to high damping properties of these alloys and their ability to produce deformation at heating in the course of the reverse martensitic transformation (shape memory effect). Control is based on the choice of a temperature variation law of the SMA active part introduced into a vibrating system. As an experiment, vibration of a torsional pendulum at a constant temperature and under periodic heat inpulses is studied. In the course of each impulse the active part material made of TiNi is transformed into austenite and then back to martensite after heating stops. Depending on the impulse time position in reference to the vibration phase, three types of control are obtained: high damping, amplification and support of sustained vibrations. Theoretical simulation of these phenomena is based on a microstructural model of the SMAs mechanical behaviour. Temperature regimes resulting in the best vibration damping are determined for a pendulum with a large elastic and small SMA rods.

ISSN:1122-8385    

DOI:10.1002/stc.4300080208

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractThe influence of time delay in linear control systems is often modeled by approximations. Here analytic criteria for determining the stability of linear differential delay systems are described. The characteristic function of such a system is a quasipolynomial, i.e. a polynomialQ(z)multiplied by powers of the exponential function exp(‐τz) plus another polynomialP(z).Using concepts of the theory of functions it has been shown that by evaluating a sequence of path integrals or the integral over the derivative of the logarithm of the characteristic function along the positive part of the imaginary axis it can be determined if the system is stable. As new result it is derived that by estimating the maximal modulus of the zeros of the characteristic function this can be reduced to the calculation of a path integral of this function over a finite conto

ISSN:1122-8385    

DOI:10.1002/stc.4300080209

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY

摘要:

AbstractThe problem of controlling a noisy flexible system so as to prevent it from leaving a pregiven safe region covers a wide range of applications. This work proposes a new approach to the problem and extends risk‐sensitive control theory to nonlinear flexible systems. Risk‐sensitive control investigates the manner in which modification of the cost criteria in stochastic systems affects the associated optimal control and makes it more sensitive to undesirable outcomes. In the problem in question, the control goal is to counteract rare but large deviations from a prescribed mode of operation. The paper develops an approximate procedure allowing construction of near‐optimal control of a relatively simple structure. The leading order near‐optimal control is found as a stationary feedback with parameters dependent on the noise intensity in the small noise limit. Limiting control performance is estimated. Risk‐sensitive control against seismic excitations is considered as an application of t

ISSN:1122-8385    

DOI:10.1002/stc.4300080210

出版商:John Wiley&Sons, Ltd    

年代:2001

数据来源: WILEY