Study On The Isolation Mechanisms Of Inter-story Isolation Structure Based On Power Flow Method

The inter-story isolation structure ensures the safety of structure,equipment and personnel by setting isolation layer,which meets the requirements of urban seismic toughness.The power flow method considers the phase relationship between force and speed.The power flow method analyzes the structure from the perspective of vibration energy.By analyzing the change of power flow,the energy transfer,transformation and dissipation of the whole structure or a local position can be obtained,so as to study the isolation mechanism of inter-story isolation structure.In this paper,the power flow method is used to study the isolation mechanism of inter-story isolation structure,the specific work is as follows:（1）The dynamic analysis model of the inter-story isolated structure was established by using the finite element theory.The response of the structure motion equation was solved by the state space method and the complex mode method.Based on the above,the power flow balance equation of the inter-story isolation structure was established,and it is proved that the average energy consumption power of the inter-story isolation structure is equal to the average input power in a period.（2）Based on the theory of power flow,the calculation formulas of power flow of different cross sections of inter-story isolation structure under deterministic excitation and random excitation were derived,and the distributions of average power flow of different cross sections of structure under different excitations were analyzed when the position of isolation layer changed.The results show that:under different excitations,the average power flow distributions of the structure have little difference,so the deterministic excitation or random excitation can be selected according to the needs in engineering application;With the location of the isolation layer moving down,the average power flow of the cross section of the isolated structure gradually transits from the upward distribution to the partial or overall downward distribution,which indicates that the isolation mechanism of the isolated structure gradually transits from TMD tuned isolation to energy dissipation isolation;The power flow of the middle story isolation structure flows from the base and the top to the isolation layer respectively,which indicates that the existence of the isolation layer changes the energy transfer path in the structure,and has a good absorption effect on the energy into the superstructure and the substructure.（3）The mean square deviation of the cross-section random power flow of the inter-story isolation structure was solved by using the virtual excitation method,and the time history curves of the crosssection power flow of the structure under different isolation forms were analyzed.The results show that:when the position of isolation layer changes,the overall distribution of power flow mean square deviation along the time direction is basically unchanged,and the inter-story isolation structure can quickly enter the stable state under earthquake excitation.The average variance of the power flow of the structure increases as the seismic structure moves down with the placement of the isolation layer.The power flow time curve of the layer interval seismic structure at different section locations is different.