The objective of this study is to identify system parameters from the recorded response of base isolated buildings,such as USC hospital building,during the 1994 Northridge earthquake.Full state measurements are not av...The objective of this study is to identify system parameters from the recorded response of base isolated buildings,such as USC hospital building,during the 1994 Northridge earthquake.Full state measurements are not available for identification.Additionally,the response is nonlinear due to the yielding of the lead-rubber bearings.Two new approaches are presented in this paper to solve the aforementioned problems.First,a reduced order observer is used to estimate the unmeasured states.Second,a least squares technique with time segments is developed to identify the piece-wise linear system properties.The observer is used to estimate the initial conditions needed for the time segmented identification.A series of equivalent linear system parameters are identified in different time segments.It is shown that the change in system parameters,such as frequencies and damping ratios,due to nonlinear behavior of the lead-rubber bearings,are reliably estimated using the presented technique.It is shown that the response was reduced due to yielding of the lead-rubber bearings and period lengthening.展开更多
Hybrid simulation can be a cost effective approach for dynamic testing of structural components at full scale while capturing the system level response through interactions with a numerical model.The dynamic response ...Hybrid simulation can be a cost effective approach for dynamic testing of structural components at full scale while capturing the system level response through interactions with a numerical model.The dynamic response of a seismically isolated structure depends on the combined characteristics of the ground motion,bearings,and superstructure.Therefore,dynamic full-scale system level tests of isolated structures under realistic dynamic loading conditions are desirable towards a holistic validation of this earthquake protection strategy.Moreover,bearing properties and their ultimate behavior have been shown to be highly dependent on rate-of-loading and scale size effects,especially under extreme loading conditions.Few laboratory facilities can test full-scale seismic isolation bearings under prescribed displacement and/or loading protocols.The adaptation of a full-scale bearing test machine for the implementation of real-time hybrid simulation is presented here with a focus on the challenges encountered in attaining reliable simulation results for large scale dynamic tests.These advanced real-time hybrid simulations of large and complex hybrid models with several thousands of degrees of freedom are some of the first to use high performance parallel computing to rapidly execute the numerical analyses.Challenges in the experimental setup included measured forces contaminated by delay and other systematic control errors in applying desired displacements.Friction and inertial forces generated by the large-scale loading apparatus can affect the accuracy of measured force feedbacks.Reliable results from real-time hybrid simulation requires implementation of compensation algorithms and correction of these various sources of errors.Overall,this research program confirms that real-time hybrid simulation is a viable testing method to experimentally assess the behavior of full-scale isolators while capturing interactions with the numerical models of the superstructure to evaluate system level and in-structure response.展开更多
In this paper,a tristable viscoelastic isolation system with stochastic excitation under both displacement and velocity delayed feedback control is considered.Firstly,the theoretical expressions of the mean first-pass...In this paper,a tristable viscoelastic isolation system with stochastic excitation under both displacement and velocity delayed feedback control is considered.Firstly,the theoretical expressions of the mean first-passage time(MFPT)to measure the activated escape between different potential wells are derived.Induced nonlinear transition dynamics due to the noise and time delays are mainly discussed.It is found that the delay-induced behaviours affect the transitions between the equilibrium points of the system,the corresponding phenomenon of the delay-enhanced stability is observed.In this respect,the existence of the maxima of the MFPT1 and the MFPT2 is found in one period.Meanwhile,the MFPT1 and the MFPT2 show the monotonic behaviour with the increase of the noise intensity.Additionally,the stationary probability density of the amplitude and the stationary mean amplitude are derived.The influence regimes of the system parameters on both stationary probability density of the amplitude and the stationary mean amplitude are explored.This paper establishes the relationship between system parameters and dynamical properties of the tristable viscoelastic isolation system.This provides a fundamental guidance for the optimization of the viscoelastic isolation by utilizing the technique of delayed feedback control.展开更多
文摘The objective of this study is to identify system parameters from the recorded response of base isolated buildings,such as USC hospital building,during the 1994 Northridge earthquake.Full state measurements are not available for identification.Additionally,the response is nonlinear due to the yielding of the lead-rubber bearings.Two new approaches are presented in this paper to solve the aforementioned problems.First,a reduced order observer is used to estimate the unmeasured states.Second,a least squares technique with time segments is developed to identify the piece-wise linear system properties.The observer is used to estimate the initial conditions needed for the time segmented identification.A series of equivalent linear system parameters are identified in different time segments.It is shown that the change in system parameters,such as frequencies and damping ratios,due to nonlinear behavior of the lead-rubber bearings,are reliably estimated using the presented technique.It is shown that the response was reduced due to yielding of the lead-rubber bearings and period lengthening.
文摘Hybrid simulation can be a cost effective approach for dynamic testing of structural components at full scale while capturing the system level response through interactions with a numerical model.The dynamic response of a seismically isolated structure depends on the combined characteristics of the ground motion,bearings,and superstructure.Therefore,dynamic full-scale system level tests of isolated structures under realistic dynamic loading conditions are desirable towards a holistic validation of this earthquake protection strategy.Moreover,bearing properties and their ultimate behavior have been shown to be highly dependent on rate-of-loading and scale size effects,especially under extreme loading conditions.Few laboratory facilities can test full-scale seismic isolation bearings under prescribed displacement and/or loading protocols.The adaptation of a full-scale bearing test machine for the implementation of real-time hybrid simulation is presented here with a focus on the challenges encountered in attaining reliable simulation results for large scale dynamic tests.These advanced real-time hybrid simulations of large and complex hybrid models with several thousands of degrees of freedom are some of the first to use high performance parallel computing to rapidly execute the numerical analyses.Challenges in the experimental setup included measured forces contaminated by delay and other systematic control errors in applying desired displacements.Friction and inertial forces generated by the large-scale loading apparatus can affect the accuracy of measured force feedbacks.Reliable results from real-time hybrid simulation requires implementation of compensation algorithms and correction of these various sources of errors.Overall,this research program confirms that real-time hybrid simulation is a viable testing method to experimentally assess the behavior of full-scale isolators while capturing interactions with the numerical models of the superstructure to evaluate system level and in-structure response.
基金supported by the National Natural Science Foundation of China(Grant Nos.11702201,11802237)China Postdoctoral Science Foundation(Grant No.2018M641012)+3 种基金the Fundamental Research Funds for the Central Universities(Grant No.G2018KY0306)the Natural Science Foundation of Shaanxi Province(Grant No.2018JQ1055)supported in the framework of the project Lublin University of Technology-Regional Excellence Initiativefunded by the Polish Ministry of Science and Higher Education(Contract No.030/RID/2018/19)。
文摘In this paper,a tristable viscoelastic isolation system with stochastic excitation under both displacement and velocity delayed feedback control is considered.Firstly,the theoretical expressions of the mean first-passage time(MFPT)to measure the activated escape between different potential wells are derived.Induced nonlinear transition dynamics due to the noise and time delays are mainly discussed.It is found that the delay-induced behaviours affect the transitions between the equilibrium points of the system,the corresponding phenomenon of the delay-enhanced stability is observed.In this respect,the existence of the maxima of the MFPT1 and the MFPT2 is found in one period.Meanwhile,the MFPT1 and the MFPT2 show the monotonic behaviour with the increase of the noise intensity.Additionally,the stationary probability density of the amplitude and the stationary mean amplitude are derived.The influence regimes of the system parameters on both stationary probability density of the amplitude and the stationary mean amplitude are explored.This paper establishes the relationship between system parameters and dynamical properties of the tristable viscoelastic isolation system.This provides a fundamental guidance for the optimization of the viscoelastic isolation by utilizing the technique of delayed feedback control.
