Analysis Of Seismic Response & Input Energy Based On Wavelet Decomposition Of Base-isolated Eccentric Structure

It is of great practical significance to study the seismic response of eccentric isolation structure under the background of structural torsional earthquake damage and complex and irregular development of buildings.Although many scholars have done a lot of research on eccentric isolation structure,most of them focus on the eccentricity of the supperstructure and the eccentricity and stiffness of the isolation syetem.In this paper,the "L" type eccentric structure and the corresponding base-isolated structure are taken as the object of study.According to the double period method,the Shaping NS and EW seismic waves and the Zhuoni NS and EW seismic waves from the Wenchuan seismic wave database are selected.Then we decompose the waves into eight adjacent frequency components by using B-spine wavelet,in which we choose bidirectional primary seismic wave and bidirectional wavelet frequency components as the input waves.The translational and torsional responses of two kinds of structures under rare and multiple earthquake are analyzed.The changes of the frequency components of the near-Earthquakes are also studied.Finally,the distribution of the input energy of the eccentric seismic isolation structure in each frequency band and each mode is discussed.Some conclusions are as follows:1.whether it's non-isolated structure or eccentric isolation structure,The contribution of the high frequency wavelet component between 12.5 and 100 Hz to response of translationa and torsion is small and can be negligibled.While the low frequency wavelet component plays a role in controlling the structure;The contribution of the high frequency component to the equivalent static force is greater than the displacement;the frequency band containing the fundamental frequency of the structure contributes the most to the response of the structure and is close to the response peak under the action of the original wave;the isolation system acts as the low frequency filter Role,the high frequency of the earthquake is almost filtered out,low-frequency component of the earthquake is more obvious than before the isolation.2.The isolation effect in the two translational direction of the eccentric isolation structure is basically the same,and isolating affection of the torsional effect is greater than the translational effect,the equivalent static force isolating affection is greater than the displacement;The long-period seismic waves are more detrimental to the isolated structure,and the change of the frequency components of the near and far earthquakes has more influence on the structural torsional response than that of the translational motion.It is disadvantageous to the isolation of the translational response from the far earthquake,while it is beneficial to the seismic isolation of the torsional response.3.No matter what kind of structure,the seismic input energy of the frequency band in the above 6.25 Hz is more than 96% of the total energy,and the distribution of the input energy of the isolated structure in this band is more uniform than that of the non-isolated structure,The frequency band of the fundamental mode frequency contributes the most to the total energy.The energy of top two group modes(i.e.the top six modes)of the non-isolated occupy more than 96% of the total energy,and the first group modes(i.e.the top three modes)of the eccentric isolation structure occupies more than 98.5% of the total energy,it can be approximated that the seismic input energy of the isolated structure is almost entirely absorbed by the vibration of the isolation layer.After isolation,the contribution of the high-order vibration mode to the total input energy is smaller.4.The contribution coefficient of the high-order vibration modes of the non-isolated structurestructure to the X-direction base shear,energy and X-side top floor lateral displacement is decreased for the specific X unidirectional seismic action.The contribution coefficien of the high-order vibration modes of eccentric isolated structures in the above-mentioned three reactions is very small,which is to say higher mode effects are less after the isolation.When the total vibration response is kept within 5% of the error,the number of demand for the X-direction base shear,energy,and X-side top floor lateral displacement is reduced in turn;the eccentric isolated structures is only the first group can meet the error 5% requirements.5.In the same type of structure,the input energy under the action of unidirectional seismic waves,energy distribution in the X-translational mode mainly,Y-translational mainly and torsion mainly is basically the same;The input energy under the unidirectional earthquake action is mainly formed by the vibration of the structure in the direction of seismic excitation.The level of energy horizontal "coupling" on the non-isolated is small under unidirectional seismic action,while the energy of the torsional vibration is larger.After the isolation,the ratio of the torsional vibration energy produced by the Y uniaxial earthquake.And the "coupling" in the horizontal direction of the energy and the torsional vibration energy are both large under the X unidirectional seismic action,and this "coupling" level of the two structures in the X direction is greater than that of the Y direction..