Research On The Eccentricity Of The Isolated Structure

Our country is located in the Eurasia plate adjacent to the Pacific plate,be cause the plate movement is very active,the surrounding earthquake fault zone development,long suffering from the earthquake.Since the 80 s of last century,the international advanced base isolation system has been paid much attention i n China.Domestic experts and scholars have been committed to related researc h and made a series of progress.The basic isolation technique has been used in the world.It is an effective seismic control technology,which can significantly reduce the seismic effects of the structure.When the base isolation is used,the attention of the reverse effect for structure is also needed.For this purpose,the requirement of the eccentricity was not greater than 3% in the relevant regulations of Japan,Taiwan and the mainland’s mainland.In some cases,however,the forced adjustment of the eccentricity to less than 3% will result in a huge reversal of the structure.At present,the research in this field is not sufficient.Therefore,we need to further study this problem.According to seismic code and isolation scientific research achievements in the field of architecture,three typical framework model is established,using structural design analysis software ETABS program to model the nonlinear elastic or elastoplastic analysis.Through the comparison and verification of the model,the input fitting of the ground vibration and the seismic analysis of fortification are analyzed,and the displacement analysis of the model is carried out in the case of rare earthquake in the premise that all the data meets the requirements of the specification.Through the two schemes of gradually decreasing the eccentricity of the isolation layer,the endpoint displacement of the isolation layer under different eccentricity conditions is analyzed.An abnormal phenomenon occurred according to the control requirements of the current partial heart rate:Within a certain range isolation layer eccentricity reduction will make the torsional response of the seismicisolation layer decreases,but continue to reduce the eccentricity torsional response rise sharply rising even tend to appear abnormal phenomenon.The eccentricity of the seismic isolation layer has little effect on the torsion of the isolated seismic isolation layer under the rare earthquake.In general,the isolation layer can be maintained at a small torsion level and not simply increase or decrease with the eccentricity.And then analyzes the reasons,It is found that there is a lack of understanding in the calculation formula of the eccentricity of the isolation layer.It is lack of pertinence to try to control the torsional response of isolated buildings by the eccentricity of the isolation layer,and the regulation that the eccentricity of the isolation layer is less than 3% is more lack of accuracy.At the same time,on the basis of the typical model analysis data,this paper proposes to give up the thought and practice of using the eccentricity of the seismic isolation layer to control the torsion of the isolated building,and puts forward a more reasonable eccentricity control method,use the idea and method of limiting the torsion angle or endpoint displacement ratio at the end of the rare earthquake to control it.