Research On The Seismic Hybrid Simulation Testing Method For Large Complex Structures

Hybrid simulation testing method,formerly also known as hybrid simulation,which combines the advantages of structural seismic experiments with numerical simulation,has become as one of the advanced structural seismic testing methods to obtain the overall structure response under earthquakes.At present,the current research on hybrid simulation testing method mainly focuses on the feasibility and effectiveness of the method itself,and its application to the simple structure.However,as implementing hybrid simulation testing method for large complex engineering structures,the computation time is too long due to the large and complex substructure,how to choose the critical experimental elements,the boundary conditions are too complicated and so on,such problems make the implementation of hybrid simulation testing method for large complex structures difficult.Based on the above problems,experimental investigations and theoretical study were conducted in this thesis,aiming to investigate the seismic hybrid simulation testing method for large complex structures.The main work is presented as follows.(1)The basic architecture of the hybrid simulation testing system with finite element analysis was studied to develop FOM(the Finite element analysis software-Open Fresco-MTS)HSTS(Hybrid Simulation Testing System).The developed HSTS employed embedded system architecture.After data interface was established,finite element analysis software,testing platform and MTS loading system were connected.Hybrid simulation tests of a multi-span continuous girder bridge were conducted to verify the proposed Open Sees-Open Fresco-MTS HSTS.The performance and stability of the FOM HSTS were evaluated through comparison of hybrid simulation testing results and finite element analysis counterpart.(2)Because of limitation of the existing equipment s,how to select the experimental element from the whole structure in hybrid simulation tests is difficult,empirical method and numerical analysis method were studied to solve this problem.A steel reinforced concrete frame with different cross-section columns was selected as the target structure,and two hybrid analysis models with different experimental elements were developed.The contrasting results of hybrid simulation tests showed that the response of the entire frame was almost identical.This observation proved that,in hybrid simulation tests,the seismic response of the whole structure could be obtained via physical tests of the local key part.(3)A hybrid analysis model simplification method based on the separation and equivalence of the dynamic and static DOFs was proposed to overcome the enormous time consumption introduced by the huge amounts of numerical elements when carrying out hybrid simulation tests for large and complex engineering structures.The dynamic model was separated from the static model and the number of the dynamic DOFs could be reduced by modal reduction of the substructure sections,and the equivalent restraining force model of the whole structure was obtained by establishing the coupling constraint between the reference point and the corresponding substructure boundary in finite element model of the numerical substructure.In addition,a series of hybrid simulation tests of a base isolated high-rise building STT(the Shaking Table Test)model were performed.The STT results were being perceived as the reference and compared with the hybrid simulation results,the proposed hybrid analysis model simplification method was verified to be able to ensure the accuracy of the restraining force model and reduce the calculation time-consuming effectively,accordingly,making it possible to conduct the hybrid simulation tests of large complex structures.(4)Considering the difficulty in the boundary condition simulation of hybrid simulation tests,a complex boundary condition configuration considering overturning effect in hybrid simulation test was put forward.By reducing the experimental element boundary freedom and extending the loading boundary,the combined control method which contained the horizontal-direction closed-loop displacement control and vertical force open-loop control was utilized to coordinate the uniform cooperative deformation of multiple experimental elements and simulate the overturning moment due to the superstructure.By reducing the degree of freedom of the boundary of the test unit and expanding the loading boundary conditions,the combined control method of horizontal-direction closed-loop displacement control and vertical force open-loop control is used to realize the uniform cooperative deformation and overturnin g moment of multiple test units with finite actuator effect.A sequential hybrid simulation tests,wherein a base isolated high-rise building was tested by consistently accounting for overturning effect due to the rocking of the superstructure were carried out.The contrast analysis of the test results verified that the proposed complex boundary condition simulation method in hybrid simulation test considering the overturning effect could be used to analyze the seismic response of the whole structure under the influence of the overturning effect.Moreover,the testing results showed that overturning effect make the response of the entire base-isolated building drastic,such as compared with the usual ones without considering overturning effect,stiffness of the base-isolation system was smaller,and the displacement was larger,the collapse risk was more significate,a narrower hysteresis occurred and the maximum storey displacement was significantly increased.