Experimental investigation and analytically modeling of hysteretic behavior of rigid bus-flexible connectors of 220 kV electrical substations

This paper describes the quasi-static testing and analytical modelling of the hysteretic behavior of aluminum alloy rigid bus-flexible connectors of 220 kV electrical substations.The main objective of the study is to experimentally investigate the hysteretic behavior of six different types of rigid bus-flexible connectors 220 kV electrical substations when subjected to cyclic loading.Another objective is to theoretically study the flexibility and effectiveness of a previously proposed analytical model in fitting the experimental hysteresis loops of the tested rigid bus-flexible connectors.The experimental investigation indicates that the tested rigid bus-flexible connectors exhibit highly asymmetric hysteresis behavior along with tension stiffening effect.The theoretical study demonstrates that the generalized Bouc-Wen model has high flexibility and is effective in fitting the experimental hysteresis resisting force-displacement curves of the six tested rigid bus-flexible connectors.

The Effect of Pore Solution on the Hysteretic Curve of Expansive Soil under Cyclic Loading

A dynamic triaxial instrument was used to study the effects of different concentrations of sodium chloride and stress amplitudes on the dynamic properties of an expansive soil under cyclic loading.In particular,four parameters were considered in such a parametric investigation,namely,hysteresis curve morphology characteristic non-closure degreeεp,the ratio of the short and long axisα,the slope of the long axis k and the enclosed area S.The results show that with an increase in the sodium chloride concentration,the soil particle double electric layer becomes thinner,the distance between soil particles decreases,and the whole sample becomes denser.Theεp-N,α-N and S–N relation curves all show a decreasing trend.The ratio of plastic deformation to total deformation grows with increasing the dynamic stress amplitude,and the curves show an upwards trend.The k-N relationship curve displays an increasing trend with the concentration and a general downwards trend as the dynamic stress amplitude is made higher.This also indicates that sodium chloride solutions can improve the engineering properties of expansive soil to a certain extent.With an increase in the vibration times N,the shape of the hysteretic curve becomes narrower,and the whole soil exhibits a cyclic strain hardening.With the help of an exponential function,a model is introduced to predict the relationship between the concentration and the hysteretic curve.

Parameter identification of hysteretic model of rubber-bearing based on sequential nonlinear least-square estimation

In order to evaluate the nonlinear performance and the possible damage to rubber-bearings （RBs） during their normal operation or under strong earthquakes, a simplified Bouc-Wen model is used to describe the nonlinear hysteretic behavior of RBs in this paper, which has the advantages of being smooth-varying and physically motivated. Further, based on the results from experimental tests performed by using a particular type of RB （GZN 110） under different excitation scenarios, including white noise and several earthquakes, a new system identification method, referred to as the sequential nonlinear least- square estimation （SNLSE）, is introduced to identify the model parameters. It is shown that the proposed simplified Bouc- Wen model is capable of describing the nonlinear hysteretic behavior of RBs, and that the SNLSE approach is very effective in identifying the model parameters of RBs.

Experimental study on hysteretic behavior of prestressed truss concrete composite beams

This paper describes an experimental study of the hysteretic behavior of prestressed truss concrete composite beams （PTCCBs） under cyclic loading. Five beam models were designed and tested, in which the testing parameters include the global reinforcement index β0, the prestress level 2 and the ratio of stirrup ρsv in the potential plastic hinge zones. Based on the test results, the failure mode and hysteretic behavior of the tested models are obtained. In addition, the P-△ and sectional M-φ hysteretic models for the PTCCBs at the midspan are established. The P-△ hysteretic model shows good agreement with the test results.

A NEW STOCHASTIC OPTIMAL CONTROL STRATEGY FOR HYSTERETIC MR DAMPERS

A new stochastic optimal control strategy for randomly excited quasi-integrable Hamiltonian systems using magneto-rheological (MR) dampers is proposed. The dynamic be- havior of an MR damper is characterized by the Bouc-Wen hysteretic model. The control force produced by the MR damper is separated into a passive part incorporated in the uncontrolled system and a semi-active part to be determined. The system combining the Bouc-Wen hysteretic force is converted into an equivalent non-hysteretic nonlinear stochastic control system. Then It?o stochastic di?erential equations are derived from the equivalent system by using the stochastic averaging method. A dynamical programming equation for the controlled di?usion processes is established based on the stochastic dynamical programming principle. The non-clipping nonlin- ear optimal control law is obtained for a certain performance index by minimizing the dynamical programming equation. Finally, an example is given to illustrate the application and e?ectiveness of the proposed control strategy.

Calibration of a hysteretic model for glass fiber reinforced gypsum wall panels

Glass fi ber reinforced gypsum(GFRG) wall panels are prefabricated panels with hollow cores, originally developed in Australia and subsequently adopted by India and China for use in buildings. This paper discusses identifi cation and calibration of a suitable hysteretic model for GFRG wall panels fi lled with reinforced concrete. As considerable pinching was observed in the experimental results, a suitable hysteretic model with pinched hysteretic rule is used to conduct a series of quasi-static as inelastic hysteretic response analyses of GFRG panels with two different widths. The calibration of the pinching model parameters was carried out to approximately match the simulated and experimental responses up to 80% of the peak load in the post peak region. Interestingly, the same values of various parameters(energy dissipation and pinching related parameters) were obtained for all fi ve test specimens.

Comparison of adaptive structural damage identification techniques in nonlinear hysteretic vibration isolation systems

Early structural damage identification to obtain an accurate condition assessment can assist in the reprioritization of structural retrofitting schedules in order to guarantee structural safety. Nowadays, seismic isolation technology has been applied in a wide variety of infrastructure, such as buildings, bridges, etc., and the health conditions of these nonlinear hysteretic vibration isolation systems have received considerable attention. To effectively detect structural damage in vibration isolation systems based on vibration data, three time-domain analysis techniques, referred to as the adaptive extended Kalman filter （AEKF）, adaptive sequential nonlinear least-square estimation （ASNLSE） and adaptive quadratic sum-sqnares error （AQSSE）, have been investigated. In this research, these analysis techniques are compared in terms of accuracy, convergence and efficiency, for structural damage detection using experimental data obtained through a series of laboratory tests based on a base-isolated structural model subjected to E1 Centro and Kobe earthquake excitations. The capability of the AEKF, ASNLSE and AQSSE approaches in tracking structural damage is demonstrated and compared.

STOCHASTIC OPTIMAL CONTROL OF HYSTERETIC SYSTEMS UNDER EXTERNALLY AND PARAMETRICALLY RANDOM EXCITATIONS

A stochastic optimal control method for nonlinear hysteretic systems under externally and/or parametrically random excitations is presented and illustrated with an example of hysteretic column system. A hysteretic system subject to random excitation is first replaced by a nonlinear non-hysteretic stochastic system. An It$\hat {\rm o}$ stochastic differential equation for the total energy of the system as a one-dimensional controlled diffusion process is derived by using the stochastic averaging method of energy envelope. A dynamical programming equation is then established based on the stochastic dynamical programming principle and solved to yield the optimal control force. Finally, the responses of uncontrolled and controlled systems are evaluated to determine the control efficacy. It is shown by numerical results that the proposed stochastic optimal control method is more effective and efficient than other optimal control methods.

Correlation failure analysis of an uncertain hysteretic vibration system

In this paper, a numerical method for correlation sensitivity analysis of a nonlinear random vibration system is presented. Based on the first passage failure model, the probability perturbation method is employed to determine the statistical characteristics of failure modes and the correlation between them. The sensitivity of correlation between failure modes with respect to random parameters characterizing the uncertainty of the hysteretic loop is discussed. In a numerical example, a two-DOF shear structure with uncertain hysteretic restoring force is considered. The statistical characteristics of response, failure modes and the sensitivity of random hysteretic loop parameters are provided, and also compared with a Monte Carlo simulation.

Experimental and numerical study on hysteretic performance of SMA spring-friction bearings

This paper presents an experimental and numerical study to investigate the hysteretic performance of a new type of isolator consisting of shape memory alloy springs and friction bearing called an SMA spring-friction bearing （SFB）. The SFB is a sliding-type isolator with SMA devices used for the seismic protection of engineering structures. The principle of operation of the isolation bearing is introduced. In order to explore the possibility of applying SMA elements in passive seismic control devices, large diameter superelastic tension/compression NiTi SMA helical springs used in the SFB isolator were developed. Mechanical experiments of the SMA helical spring were carried out to understand its superelastic characteristics. After that, a series of quasi-static tests on a single SFB isolator prototype were conducted to measure its force-displacement relationships for different loading conditions and study the corresponding variation law of its mechanical performance. The experimental results demonstrate that the SFB exhibits full hysteretic curves, excellent energy dissipation capacity, and moderate recentering ability. Finally, a theoretical model capable of emulating the hysteretic behavior of the SMA-based isolator was then established and implemented in MATLAB software. The comparison of the numerical results with the experimental results shows the efficacy of the proposed model for simulating the response of the SFB.

Hysteretic energy prediction method for mainshock-aftershock sequences

Structures located in seismically active regions may be subjected to mainshock-aftershock（MSAS）sequences.present study selected two kinds of MSAS sequences,with one aftershock and two aftershocks,respectively.The aftershocksThe MSAS sequence with one aftershock exhibited a 10%to 30%hysteretic energy increase,whereas the MSAS sequence with two aftershocks presented a 20%to 40%hysteretic energy increase.Finally,a hysteretic energy prediction equation is proposed as a function of the vibration period,ductility value,and damping ratio to estimate hysteretic energy for mainshockaftershock sequences.

SEISMIC RANDOM RESPONSE ANALYSIS OF HYSTERETIC SYSTEMS WITH PSEUDO EXCITATION METHOD

The stationary random responses of nonlinear shear-typeMulti-Degrees-of-Freedom (MDOF) hysteretic system are analyzed byusing the Pseudo Excitation Method (PEM) combined with the EquivalentLinerization Method (ELM). The solution of the equivalent linearsystem is obtained by iteratively solving complex algebraic equationsinstead of the Lyapunov equations. The efficiency of this method ismuch higher For practical engineering systems with manydegrees-of-freedom.

Vortex-Induced Vibrations of A Free-Spanning Pipe Based on A Nonlinear Hysteretic Soil Model at the Shoulders

The pipe-soil interactions at shoulders can significantly affect the vortex-induced vibrations (VIV) of free-spanning pipes in the subsea. In this paper, the seabed soil reacting force on the pipe is directly calculated with a nonlinear hysteretic soil model. For the VIV in the middle span, a classic van der Pol wake oscillator is adopted. Based on the Euler-Bernoulli beam theory, the vibration equations of the pipe are obtained which are different in the middle span and at the two end shoulders. The static configuration of the pipe is firstly calculated and then the VIV is simulated.The present model is validated with the comparisons of VIV experiment, pipe-soil interaction experiment and the simulation results of VIV of free-spanning pipes in which the seabed soil is modelled with spring-dashpots. With the present model, the influence of seabed soil on the VIV of a free-spanning pipe is analyzed. The parametric studies show that when the seabed soil has a larger suction area, the pipe vibrates with smaller bending stresses and is safer.While with the increase of the shear strength of the seabed soil, the bending stresses increase and the pipe faces more danger.

Derivation of energy-based base shear force coefficient considering hysteretic behavior and P-delta effects

A modified energy-balance equation accounting for P-delta effects and hysteretic behavior of reinforced concrete members is derived. Reduced hysteretic properties of structural components due to combined stiffness and strength degradation and pinching effects, and hysteretic damping are taken into account in a simple manner by utilizing plastic energy and seismic input energy modification factors. Having a pre-selected yield mechanism, energy balance of structure in inelastic range is considered. P-delta effects are included in derived equation by adding the external work of gravity loads to the work of equivalent inertia forces and equating the total external work to the modified plastic energy. Earthquake energy input to multi degree of freedom（MDOF） system is approximated by using the modal energy-decomposition. Energybased base shear coefficients are verified by means of both pushover analysis and nonlinear time history（NLTH） analysis of several RC frames having different number of stories. NLTH analyses of frames are performed by using the time histories of ten scaled ground motions compatible with elastic design acceleration spectrum and fulfilling duration/amplitude related requirements of Turkish Seismic Design Code. The observed correlation between energy-based base shear force coefficients and the average base shear force coefficients of NLTH analyses provides a reasonable confidence in estimation of nonlinear base shear force capacity of frames by using the derived equation.

ESTIMATION OF LOCAL HYSTERETIC PROPERTIES FOR SHAPE MEMORY ALLOYS

The applicability of shape memory alloys (SMAs) in structural dynamics,particularly as hysteretic damping elements, is limited by the difficulties in modelling theirdeformation characteristics. At typical engineering design levels of loading SMAs exhibitpseudo-elastic properties. A combined experimental and simulation approach suitable for thecharacterisation of novel smart devices based on the pseudo-elastic effect is described.

Optimal bounded control for maximizing reliability of Duhem hysteretic systems

The optimal bounded control of stochastic-excited systems with Duhem hysteretic components for maximizing system reliability is investigated. The Duhem hysteretic force is transformed to energy-depending damping and stiffness by the energy dissipation balance technique. The controlled system is transformed to the equivalent non- hysteretic system. Stochastic averaging is then implemented to obtain the It5 stochastic equation associated with the total energy of the vibrating system, appropriate for eval- uating system responses. Dynamical programming equations for maximizing system re- liability are formulated by the dynamical programming principle. The optimal bounded control is derived from the maximization condition in the dynamical programming equation. Finally, the conditional reliability function and mean time of first-passage failure of the optimal Duhem systems are numerically solved from the Kolmogorov equations. The proposed procedure is illustrated with a representative example.

Influence of Hysteretic Behaviour in Reactive Magnetron Sputtering on the Crystal Structure and Characteristics of Aluminium Oxide Films

The influence of the hysteretic behaviour in reactive sputtering with a pure aluminium target in the presence of argon and oxygen plasma on transmittance and surface free energy of aluminium oxide films was investigated by plasma optical emission spectroscopy technology. The evolutions of aluminium, and aluminium oxide emission lines as functions of oxygen flow rate at constant power and pressure were studied. A steep transition from the metallic sputtering to the compound sputtering was observed upon increasing the oxygen flow rate from 0.0 SCCM to above 2.0 SCCM. Then an optimal deposition zone was obtained through analyzing the hysteretic curves of aluminium and aluminium oxide emission lines. The evolution of crystal structures of samples was discerned by X-ray diffraction spectra data. Energy dispersive X-ray spectroscopy data also demonstrate the relationship between the chemical compositions of aluminium oxide films and the hysteretic behaviour. The film deposited between 1.5 SCCM and 2.0 SCCM oxygen flow rate displays an optimal and stoichiometic atomic ratio of O to Al and mass ratio of O to Al. The changes in the transmittance of samples were discovered to depend on the oxygen flow rate by UV-VIS transmittance spectra, and the changes in surface free energy were studied by contact angle measurement.

Effects of residual stress and viscous and hysteretic dampings on the stability of a spinning micro-shaft

This study examines the effects of the residual stress and viscous and hysteretic dampings on the vibrational behavior and stability of a spinning Timoshenko micro-shaft.A modified couple stress theory(MCST)is used to elucidate the sizedependency of the micro-shaft spinning stability,and the equations of motion are derived by employing Hamilton’s principle and a spatial beam for spinning micro-shafts.Moreover,a differential quadrature method(DQM)is presented,along with the exact solution for the forward and backward(FW-BW)complex frequencies and normal modes.The effects of the material length scale parameter(MLSP),the spinning speed,the viscous damping coefficient,the hysteretic damping,and the residual stress on the stability of the spinning micro-shafts are investigated.The results indicate that the MLSP,the internal dampings(viscous and hysteretic),and the residual stress have significant effects on the complex frequency and stability of the spinning micro-shafts.Therefore,it is crucial to take these factors into account while these systems are designed and analyzed.The results show that an increase in the MLSP leads to stiffening of the spinning micro-shaft,increases the FW-BW dimensionless complex frequencies of the system,and enhances the stability of the system.Additionally,a rise in the tensile residual stresses causes an increase in the FW-BW dimensionless complex frequencies and stability of the micro-shafts,while the opposite is true for the compressive residual stresses.The results of this research can be employed for designing spinning structures and controlling their vibrations,thus forestalling resonance.

Nonlinear stochastic optimal bounded control of hysteretic systems with actuator saturation

A modified nonlinear stochastic optimal bounded control strategy for random excited hysteretic systems with actuator saturation is proposed. First, a controlled hysteretic system is converted into an equivalent nonlinear nonhysteretic stochastic system. Then, the partially averaged It? stochastic differential equation and dynamical programming equation are established, respectively, by using the stochastic averaging method for quasi non-integrable Hamiltonian systems and stochastic dynamical programming principle, from which the optimal control law consisting of optimal unbounded control and bang-bang control is derived. Finally, the response of optimally controlled system is predicted by solving the Fokker-Planck-Kolmogorov (FPK) equation associated with the fully averaged It? equation. Numerical results show that the proposed control strategy has high control effectiveness and efficiency.

Study on optimum arrangement of hysteretic dampers in frame structure

The earthquake mitigation effect of hysteretic dampers is not only related to the number, stiffness, strength, deformation ability of dampers but also to the strength and stiffness of the structure. This paper studied the condition that structures should be in when the hysteretic dampers mitigated seismic action most effectively and made appropriate numerical analysis to verify the effectiveness of theory derivation. The inelastic seismic responses were analyzed for the SDOF system that the shear strength ratio of the damper system was taken differently and the result showed that when the ratio was in the vicinity of the optimum strength ratio of the damper system, the displacement of the structure was minimum and the energy dissipation of dampers was maximum, which indicated that the dampers mitigated seismic action most effectively. The result also indicated that the hysteretic dampers had significant earthquake mitigation effect when the strength ratio β changed in a relatively wide range.