| A structure tends to be under another earthquake effect after sufferring the effect of an earthquake.At this time,the structure with a certain initial damage has not been timely repaired,subsequent earthquakes on the structure may make the structure more cumulative damaged and even collapse,which will lead to more serious property damage and casualties.Seismologists in our country only consider a single design in structure seismic design without taking into account the effect of main earthquake aftershock sequence type ground motion on the influence of the structure.They have not made specific provision in sequence of the ground motion for structure damage;At the same time,in the seismic simulation test or finite element simulation,a single main earthquake is basically adopted,and the seismic resistance of the structure obtained cannot truly describe the response of the structure under the action of actual earthquakes.At first,this articlehis set up an 8-degree earthquake steel frame structure(6 m * 6 m * 15.9 m)according to the current seismic code.Then,the author made cumulative damage in shaking table test of this steel frame in accordance with the 1/2 scale,and collect data through the traditional data acquisition method and the new data acquisition system for 3d-DIC;Secondly,finite element analysis was carried out on the structure.Comparison between the results of the experimental data and finite element numerical simulation analysis can prove: the fast nonlinear time history analysis of finite element software(FNA)can accurately calculate the steel frame structure under the action of multiple seismic damage cumulative effect;Based on the analysis of structural natural vibration frequency and the node damage status,wo can konw: based on the structural damage index of the displacement delta can accurately reflect the overall damage of steel frame structure under seismic action;Through the selection of the actual earthquake by ondemond synthesis method,this paper constructed 175 main earthquake aftershock sequence types,and then analyzed the simple steel frame(1×1×4)and the general steel frame(3×4×5)by the method of control parameter variables.The author analyzed the influence law of cumulative damage of components respectively in main earthquake PGA of 0.3g,0.4g,0.6g and 0.8g and the the influence law of the main shock on the cumulative damage in the case of the aftershocks PGA of 0.1g,0.2g,0.3g,0.4g,0.5g and 0.6g:(1)the structure of the accumulation of additional damage and aftershocks ground motion characteristics is closely related to the intensity of aftershocks and the natural vibration period of main damaged structure corresponds to the spectrum characteristics of aftershocks,determines the structure of additional cumulative damage increment size;(2)the main effect on the accumulation of additional damage is not consistent with the law,in the main structure of different damage degree,its stiffness of fall and the enlargement of cycle is different,so the corresponding to different aftershocks,the structure with different additional cumulative damage;(3)For general steel frame(3×4×5): for within the scope of the seismic analysis of spectral acceleration is less than 1.0 m/s ^ 2 aftershocks,in the seismic design of structures can be neglected;for within the scope of the seismic analysis of spectral acceleration can reach 1.5 m/s ^ 2 aftershocks,in this earthquake seismic design of structures can be less consideration;for within the scope of the analysis of the spectral acceleration of 2.5 m/s ^ 2 or more aftershocks,in this earthquake seismic design of structures to cause enough attention;(4)in practical application,the designer should combine the local historical earthquake data,speculated that the possibility of intensity and frequency spectrum characteristics of the aftershock sequence,in order to improve the steel frame structure of the corresponding safety factor. |
