Research On Site Effect Based On KIK-NET Strong-motion Network

In order to alleviate the contradiction between the shortage of available land and the increasing congestion of urban land traffic,most cities in our country have started to develop the comprehensive utilization of underground space and the construction of underground transportation network in recent ten years.With the increasing number of underground engineering structures,many new scientific and technical problems have arisen in seismic design and analysis of such structures.From the input of the ground motion,for most of the conventional structure,according to China's current seismic code to the surface of the design response spectrum or seismic ground motion as input,and for underground engineering structure(including the basic depth of the super high-rise buildings),China's seismic code is not the underground ground motion input to do a clear and meticulous provisions,if still the surface of the design response spectrum or seismic ground motion as input,it will obviously lead to the calculation of the results of the rationality of the reduction.In order to solve this problem,we need to conduct a comprehensive study of the seismic field effect,in order to reveal the difference between surface and underground ground vibration and contact.At present,the study of site effect is mainly limited to some special cases of statistical and simulation analysis,comprehensive,systematic research has not yet started,the research results can not meet the requirements for seismic design.In this paper,the strong earthquake records recorded by the KiK-net seismic network in Japan since 1997 were collected and screened.The three factors and non-stationary characteristics of ground motion were studied.The three factors of ground conditions were studied.Non-stationary characteristics of the law and design recommendations for the underground structure of the seismic input to provide the basis for the determination.The main contents of this paper include:1)Effect of site condition on amplitude characteristics of ground motion.In this paper,the downhole record of Seismic record of KiK-net seismic network is recorded as bedrock ground motion while the Inoue record is the surface ground motion.Then the attenuation law of PGA(peak ground acceleration)of bedrock and surface ground motion is given respectively.In this paper,the PGA amplification factor ?,Arias intensity amplification factor A,spectral intensity amplification factor S,their influencing factors and laws are discussed,and then the attenuation formula under the above factors is returned to the formula.Finally,the design suggestions of each factor are given.2)Effect of site conditions on spectrum characteristics of ground motion.In this paper,the ratio of ground motion response spectrum to bedrock ground motion response spectrum is taken as the object of study.Two kinds of spectral ratios model corresponding to the law of spectral variation are proposed.And then compare the fitting effect between the two models.Finally fitting effect of the model II is determined as the spectral ratio model.The paper discusses the multidimensional correlation and attenuation law of the spectral ratio model parameters,and compares the shape change rule of the spectral ratio model under different conditions.Then,the paper takes a model as an example.the model is in condition of 8 degree seismic fortification,the underground site conditions for the class ? and the design of the earthquake group for the first group.Finally,the design response spectrum is designed at different depths.3)Effect of site conditions on non-stationary characteristics of ground motions.Two kinds of strength envelope models were used to study on the non-stationary characteristics of surface and bedrock ground motion.The paper analyzes the multidimensional relationship between the ratio of surface and bedrock strength envelope parameters,and gives the corresponding attenuation law.Two kinds of instantaneous frequency models are used to study the non-stationary characteristics of the surface and bedrock ground motion.Then,multidimensional interrelation of parametric ratio of instantaneous fequency model of surface and bedrock is analyzed,and finally give the corresponding attenuation law.