Research On Offline Model Updating Hybrid Simulation Method For Frame Model

Hybrid simulations can accurately obtain the seismic response of the structure by combining physical experimentation on part of the structural system with strong nonlinear and numerical simulation of the remaining structural components.The benefit of the hybrid simulations diminishes when there are multiple numerical substructures with similar structural configuration and material properties of physical substructure.In order to improve the accuracy and efficiency of the hybrid test method,this paper proposes a new structural hybrid test method based on offline model parameter updating.In order to obtain seismic responses at the structural system level,the method first extracts key parts from the structure as physical substructures to perform a quasi-static test of the preset loading path,and then identifies hysteresis model parameters based on the measured force-displacement curves of the physical substructures,finally use the identified model parameters for the numerical simulation of the seismic response of the structure.The main research contents are as follows:(1)The unscented Kalman filter(UKF)is used to identify the parameters of the Bouc-Wen model of the nonlinear single degree of freedom(SDOF)system.The result of numerical simulation shows that the parameters of model can converge to the true value quickly,and the final recognition value has high accuracy.A parametric study of the UKF system model parameters is carried out first to determine the optimum values to be used in the verification experiments.The Adaptive unscented Kalman filter(AUKF)add the variance adaptive module based on the UKF.The result of numerical simulation through three different noise levels show that when the noise level of the measurement system changes,the AUKF algorithm is more stable than the UKF algorithm The accuracy of the identification value is also relatively higher.(2)The AUKF algorithm is used to identify the restoring force model parameters of BRB.Firstly,the effect of each parameter of Bouc-Wen on the shape of the hysteresis curve is discussed,which provides a reference for the selection of the restoring force model parameters for BRB.Then quasi-static tests of experimental substructure are performed under different loading path.From the result of identifed parameters can improve the identified parameters are relatively stable when the behavior of experimental substructure is not affected by loading path.Virtual hybrid tests of an 8-story,4-bay steel frame equipped with BRBs were conducted by Open SEES,which shows that the the hybrid test method of the frame structure based on the offline model update greatly improves the accuracy of the test.(3)The efficiency and test error of traditional hybrid test,online model update hybrid test and offline model update hybrid test are studied through three examples of frame equipped with BRBs.The results show with the complexity of the structral,the accuracy of the traditional hybrid test will decrease.Both structural hybrid test based on model parameter updating can achieve higher accuracy,and the offline model updating hybrid test has higher accuracy.At the same time,this method simplifies the test process,the test efficiency is higher than the online model update hybrid test method.