Study On Floor Slippage Design Response Spectrum For Seismic Isolation Structures

With the large-scale construction of seismic isolation buildings in China,new requirements have been proposed for the safety of non-structural components in seismic isolation buildings.The results of several earthquakes in recent years have shown that if effective measures are not taken,the damage to non-structural components in seismic isolation buildings is still difficult to avoid,especially for floating equipment placed only on the structure and not fixed to it.The slip response of such equipment may even exceed that of the seismic-resistant structure.However,the current seismic isolation design only guarantees the safety of the structure and personnel,and equipment is generally not subjected to seismic calculations.Moreover,the existing floor response spectra of seismic isolation structures are only based on the fixed situation between the equipment and the floor,without considering the floating equipment.Therefore,this paper focuses on floating equipment in seismic isolation structures,assuming that the floating equipment only experiences slip and selecting typical foundation isolation structural forms.Based on the dynamic characteristics of the floating equipment and considering the main factors affecting the floor slip response spectra of the seismic isolation structure,the floor response spectra of the seismic isolation structure with different parameters are statistically analyzed to establish a standardized design response spectrum for seismic isolation structures that has universal significance.The main research content is as follows:(1)A dynamic analysis model of the seismic isolation structure-floating equipment system is given,considering the interaction between the two,and a Simulink dynamic simulation model of the seismic isolation structure-floating equipment system is established.The dynamic time-history analysis of the system is carried out to obtain the maximum slip response of the equipment.(2)The floor slip response spectra of typical seismic isolation structures are drawn,and the main influencing factors of the floor slip response spectra of the seismic isolation structure are analyzed and determined.(3)Through regression analysis,orthogonal experimental methods,and statistical analysis,the spectrum shape,characteristic parameters,and mathematical expressions of each characteristic parameter of the floor slip design response spectra of the seismic isolation structure are determined.Three engineering examples are selected,and the proposed floor slip design response spectra of the seismic isolation structure are used to obtain the displacement response of the floating equipment,which is then compared with the results of the timehistory analysis method to verify the reliability of the proposed floor slip design response spectra of the seismic isolation structure.(4)Based on the real-time hybrid test method,the dynamic response of the seismic isolation structure-floating equipment system under multiple working conditions is measured,and the average floor slip response spectra of the seismic isolation structure are determined based on the maximum measured slip of the equipment,to evaluate the rationality and reliability of the established floor slip design response spectra of the seismic isolation structure.Through the above research,the following main conclusions are obtained:(1)Using a Simulink dynamic simulation model to simulate the interaction between the sliding equipment and the structure,the results of dynamic analysis show that the period error of the established seismic isolation structure-sliding equipment system dynamic model is not more than 2.5% compared with the Open Sees finite element model calculation results,and the maximum displacement response error of the equipment is not more than 10%.This indicates that the dynamic model of the seismic isolation structure-floating equipment system established in this paper is accurate,and the analysis results can be used for the research of the floor slip response spectra of the seismic isolation structure.(2)The floor slip design response spectra of the seismic isolation structure have a similar shape,with the friction coefficient as the horizontal axis and the maximum displacement response of the equipment as the vertical axis.The greater the mass of the equipment,the more obvious the coupling effect between the seismic isolation structure and the sliding equipment.Especially when the mass ratio of the equipment to the floor exceeds 0.1,the coupling effect between the sliding equipment and the structure cannot be ignored.The mass of the equipment,the type of site,the intensity of the earthquake motion,and the horizontal damping coefficient will all affect the spectral values and shapes of the floor slip response spectra,especially the intensity of the earthquake motion has a significant impact on the floor slip response spectra.The influence of equipment placement on the design response spectrum for floor slip is negligible and can be disregarded.(3)The standardized floor slip design response spectra established in this paper can faithfully reflect the frequency spectrum characteristics of the floor slip response spectra,reproduce the curve changes of the floor slip response spectra,and the spectral values of each segment can basically envelop the floor slip response spectra.Compared with the results of the time-history analysis method,the maximum displacement responses of the equipment obtained using this floor slip design response spectra are within 12% of the error,indicating that this floor slip design response spectra have high accuracy and good engineering practicability.(4)The real-time hybrid test system of the seismic isolation structure-floating equipment system established in this paper can consider the interaction between the seismic isolation structure and the sliding equipment,and the peak value errors of the command displacement and control displacement are within 2mm,indicating that the established real-time hybrid test system has small test errors and the test results are reliable.The spectral shape of the proposed floor slip design response spectra of the seismic isolation structure is basically consistent with the average floor slip response spectra obtained from the test,with an error in spectral values within 7%.This indicates that the spectral value estimation of the proposed floor slip design response spectra of the seismic isolation structure is more conservative and accurate.