A Novel Hybrid Simulation Method Considering Incomplete Boundary Conditions

Hybrid simulation is a simulation method that integrates the advantages of numerical computation and physical testing in an online fashion.In the field of civil engineering,it originated from pseudodynamic test.Typically,the whole structure is divided into two substructures: the part with complex nonlinearities which are difficult to be accurately modeled is taken as physical substructure and loaded in the laboratory;the remainder is taken as numerical substructure and simulated by a computer program.Thus,the demand for testing facilities is reduced,the large-scale even full-scale hybrid simulations are made possible for large and complex structures.However,restrainted by the facility,test site and research funding,the boundary conditions cannot be fully achieved due to huge numbers of degrees of freedom on the boundary of physical substructure.And hence,the stress states deviate from the actual response due to the absence of boundary conditions.It is a challenge to obtain a high quality of hybrid simulation results based on the incomplete boundary conditions.In this thesis,the boundary conditions that cannot be fully achieved on the physical substructure are called incomplete boundary conditions.A novel hybrid simulation method is proposed to deal with the problem of incomplete boundary conditions in a hybrid simulation.The main work and conclusions are as follows:1.A gradient based parameter estimation method is proposed.Based on Lyapunov stability theory,the convergence of Kalman filter(KF)used for parameter estimation is proved and the convergence condition is achieved for extend Kalman filter by introducing a nonlinear parameter.To make a better unstanding of unscented Kalman filter(UKF),the relation between KF and recursive least square is presented explicitly,and the proposal of parameter selection for KF is given.The UKF is essentially a stochastic least square.Based on a scalar nonlinear function,the presion of scaled unscented transformation employing symmetric sampling method is analyzed,the influence of sampling parameters are discussed and the values of sampling parameters making mean and variance to reach fourth order presion are given.Results of numerical simlations reveal that the UKF converges fast and has a strong robustness.2.A novel hybrid simulation method is proposed based on model updating,which is called online numerical simulation(ONS).In the proposed method,the boundary conditions are naturally satisfied because the response is calculated from the overall structure,and the accuracy is improved for the material constitutive parameters are updated;the measured forces from physical specimen are no longer returned to the time integration module,but to the constitutive parameter estimation module for online estimation.The proposed method is extensible.Based on TCP/IP network transmission protocol,the communication between the calculation software MATLAB and the finited element software Open Sees is realized without changing the framework of Open Sees.The results reveal that,the accuracy of hybrid simulation employing the poroposed method is improved significantly and the ONS behaviours high robustness.Model updating alone does not necessarily improve the results of hybrid simulation.3.Hybrid simulation framework employing finite element is established based on Open Sees,MATLAB,Hy Test Connector and MTS.And taking the reinforced concrete frame structure as an example,the proposed ONS method is validated through actual hybrid simulation.The results show that compared to the other two hybrid simulation methods,the response of the proposed method matches the reference solution best and exhibits strong robustness.The evolutions of estimated parameters in actual hybrid simulation are similar to that in numerical simulation.Due to the inaccurate of concrete material model in Open Sees,the estimated parameters exhibit peak ground accelerate dependent.And additional numerical simulation reveals that the slight fluctuations in axial force have little influence on the estimated converged value.4.Taking short-pier shear wall structure and BRB-RCF as examples,the applicability of ONS in seismic testing of large building structures is discussed.The applicable conditions for the simulation of shear wall using Eulerian beams are studied,and a three-stage method for modeling BRB is proposed.A parameter estimation method of multi-constitutive model of composite structures is proposed,and the influence of the number of observations on parameter estimation is discussed.Results show that,ONS method is suitable for seismic testing and it is feasible to estimate parameters of different materials together and estimate parameters of high dimension by emplying UKF.For civil engineering structure,the single measurement mode is sufficient to ensure the accuracy of parameter estimation.