Influence Of Structures On Ground Motion Records

China is preparing the "National Seismic Intensity Rapid Reporting and Earthquake Early Warning Project" construction,and a large number of seismic observation stations for seismic intensity rapid reporting and earthquake early warning will be built,among which the number of seismic intensity meters will be more than 10,000 units.Due to the low price of the seismic intensity meter(SIM),the background noise of the instrument itself is relatively high,and most SIMs are located in densely populated area.The location requirement is low,and most of SIMs will be placed on the first and second masonry structures or near the communication tower of the communication company to meet the power supply and communication conditions.The structure near the site has a certain influence on the ground motion record.In order to analyze the influence of the structure on the ground motionrecords,this thesis takes the communication tower and the low masonry structure as an example.With the establishment of soil communication tower coupling single degree of freedom system,influence of dynamic soil and structure parameters on the ground motion records is analyzed.With masonry structure SDOF calculation model and motion equation,the effect of structural dynamic parameters on the ground motion records is also analyzed.With the establishment of three-dimensional finite element model of free field soil and communication tower and one or two story masonry structure using the finite element software ABAQUS,analysis of soil communication tower interaction effect on the foundation's intensity,peak acceleration and spectrum under different conditions are conducted,and the influence of low intensity on masonry structure instrument record calculation are also investigated.The main contents of this thesis include:(1)The principle and characteristics of soil-structure interaction are systematically studied.By analyzing the motion equation of the flexible foundation,the nature of the interaction between soil and structure is explained.Taking the communication tower as an example,the calculation model and the motion equation of the soil-communication tower are established,and the variation law of the horizontal displacement in the frequency domain is deduced.Through the parameter analysis of soil structure interaction characteristics,the principle and steps of the three-dimensional viscoelastic artificial boundary and the equivalent ground motion input are introduced.The accuracy of the method in the finite element analysis of the three-dimensional time domain is verified by an example.(2)The ABAQUS three-dimensional finite element model of communication tower-pile-foundation is established,and its geometric parameters,material properties and related parameters of soil medium and artificial boundary are introduced in detail,and the grid size and analysis step size are determined.Three sets of time-history results obtained by inversion of four different ground motion records are input into the finite element model of soil-communication tower by using ProShake software respectively.The ground motions with different acceleration peaks are studied.Study the effect of the seismic intensity of the instrument,the peak of the acceleration and the spectrum of the ground motion and the effect of peak acceleration and spectrum of the ground motion at different distances from the base center with and without influence of pile tower function inputting different peak acceleration of ground motion are analyzed.(3)The calculation model of the single particle system of the masonry structure and its motion equation are established.The function relationship between the absolute displacement of the particle point and the absolute displacement ratio of the single particle system is analyzed.The modeling method of the masonry structure is studied,the material parameters of the masonry structure are determined,and the ABAQUS finite element software is used to establish the finite element model of the first and second floor masonry structure.The modal analysis of the structure of the first and second floor masonry structure is carried out to verify the rationality of the model.Finally,four different ground motion records are input to the base of the one or two story masonry structure in X direction,and the influence of the peak and the spectrum on the ground motion of the tectonic column is studied.