Research On Off-line Hybrid Iterative Test Method Of Isolation Structure

Recently,seismic isolation technology has been one of the most effective means to improve the seismic ability of structures.Seismic isolation technology has been applied to large complicated structures,but its seismic ability assessment needs to be further studied.The existing test methods cannot meet the requirements of seismic capacity assessment:(1)The traditional compression-shear test mainly is difficult to reflect the dynamic interaction between the seismic isolation device and the main structure in a large complicated structure,and cannot evaluate the seismic capacity of a large complicated isolation structure;(2)Shaking table test can directly simulate the seismic response of the structure,but the large complicated structure can only be tested by a small-scaled model.The material similarity relationship error and the simplification of structural details will be brought by the small scale-down,which makes the test results only used for qualitative evaluation of the seismic capacity of the structure.Realtime hybrid test can simulate the dynamic interaction between the seismic isolation device and the structure to accurately assess its seismic capacity.Real-time hybrid test requires not only a real-time calculation of large complicated structure regarded as numerical substructure,but also real-time communication between numerical calculation and real-time test loading,which has high requirements for communication platform and loading equipment.To solve above problems,this study develops an off-line hybrid iterative test method for seismic isolation structures(OHII),which is applied to the seismic performance test of large complicated isolation structures.In this method,the typical isolation bearing is taken as the experimental substructure and the remain of the isolation structure is considered as the numerical substructure.Without simplifying the numerical substructure model in this method,the test loading and numerical calculation are carried out independently in the whole time of seismic load.The displacement calculation results of the entire period are transferred between substructure,and the boundary coordination between the numerical substructure and the test substructure is ensured through offline iterative correction,which can avoid real-time communication between the numerical and experimental substructure and make the requirement for communication platform and loading equipment lower.This study does the following works:(1)The principle of the OHII is presented.The OHII uses the model recognition algorithm to identify the system transfer function and iteratively corrects the driving displacement signals time history of the experimental substructure in the frequency domain based on the transfer function.The model recognition algorithm uses a frequency response function(FRF)to identify the relationship between the system input and output,and then obtains the relationship between the system output and the system input signal through inversing the FRF.The inversion of FRF is used to convert the response error between the experimental and numerical substructures into a correction of the system input,which is used to correct the driving displacement signal of the experimental substructure.This driving displacement time history signal is loaded to the experimental substructure,then its restoring force time history signal is fed back to the numerical substructure to calculate the displacement response time history signal,then the next iteration is conducted.This process is repeated until the boundary displacement response between the experimental substructure and the numerical substructure converges to an acceptable level of error.(2)The numerical simulation of the OHII was carried out.Taking a large complicated seismic isolation structure as an example,an off-line hybrid iterative test system for seismic isolation structure was built,and the substructure division of the seismic isolation structure was carried out: an isolation bearing was selected as the experimental substructure,and the remain of the seismic isolation structure was taken as the numerical substructure.The boundary between the numerical and the experimental substructures was simplified.In the numerical simulation,the Simulink model of the experimental substructure and the compression-shear testing machine was established to simulate the actual loading situation,the numerical substructure was simulated and analyzed by Midas software,and the numerical simulation of the OHII was carried out at three different seismic wave conditions.The feasibility of the OHII is preliminarily verified.(3)The off-line hybrid iterative test and parameter analysis test of seismic isolation structures were carried out(with the 10 times slowing speed).Three seismic waves were input for off-line hybrid iterative tests of seismic isolation structures,respectively.The simulation results were used to analyze the effect of the OHII on the correction of displacement signal error between isolation bearing and structure based on different seismic input,which further verifies the feasibility of the test method.In order to achieve better effect of the OHII,the parameter analysis test of seismic isolation structures with different lower frequency parameters were conducted under two different seismic conditions,and the experimental iterative effect of different lower frequency parameters were analyzed.(4)The off-line hybrid iterative test and parameter analysis test of seismic isolation structures were carried out(with the 5 times slowing speed).Three different seismic waves were input for off-line hybrid iterative tests of seismic isolation structures with relative fast speed,respectively.The simulation results were used to analyze the effect of the OHII on the correction of displacement signal error between isolation bearing and structure based on different seismic input,which further verifies the feasibility of the test method with relative fast loading.The parameter analysis test of seismic isolation structures with different lower frequency parameters were conducted under three different seismic conditions,and the experimental iterative effect of different lower frequency parameters under relatively fast loading condition were analyzed to achieve better effect of the OHII.