Study On Seismic Response Of Isolated Structures Considering Lead Core Degradation

In order to cope with the impact of earthquake disasters on structure,scholars at home and abroad have put forward isolation technology,shock absorption technology,TMD technology and AMD technology.Because of the advantages of simple structure and strong applicability of isolation bearings,isolation technology has been widely used in isolation structures at home and abroad since the 1980 s.Therefore,the research on isolation technology has been relatively mature,but the research on isolation technology is relatively small in special cases.For example,under the action of long-period and long-duration earthquakes,the isolation bearings are caused by the increase of lead core temperature.The mechanical properties of bearings have changed,so that the displacement of the isolation layer of the isolation structure often exceeds the limits of the code,resulting in a decline in the safety of the isolation structure,and even endangering the safety of people's lives and property.Therefore,it is necessary to study the degradation law of the mechanical properties of isolation bearings under long-period and long-duration earthquakes,and to substitute the law into the simulation model of isolation structure to study the seismic response,so as to more intuitively judge the safety impact of lead core degradation of isolation bearings on isolation structure.The contents of this paper are mainly divided into the following modules:(1)Firstly,the scale lead-rubber isolation bearing is adopted.Through compression-shear test,the degradation of the horizontal mechanical properties of the test bearing is studied under the action of multiple reciprocating loads at a relatively fast level,which illustrates that the degradation of the horizontal mechanical properties of the isolation bearing will occur under the action of rapid load.Then,the full-scale lead rubber isolation bearing is used to study the specific change value and law of the mechanical properties of the test bearing under the action of fast horizontal multiple reciprocating loads through compression-shear test.(2)By consulting the relevant papers at home and abroad,several common mechanical models describing the hysteretic nonlinearity of structures are selected.Then,according to the advantages and disadvantages of each mechanical model,appropriate mechanical models are selected as templates.Then,the applicability and sensitivity of each parameter of the mechanical model are analyzed and studied,and a simplified hysteretic nonlinearity mechanical model is obtained.(3)Combining the selected hysteretic non-linear model with the theoretical formula of lead core temperature,the mechanical model and test curve are fitted and modified by genetic algorithm,and the mechanical performance degradation model of lead rubber isolation bearing is obtained.(4)The mechanical properties degradation model of lead-rubber isolation bearing is substituted into the actual finite element model of engineering structure to study the seismic response of the isolation structure under 7 long-period and longduration natural seismic waves,and the safety of the isolation structure without considering lead-core degradation under long-period and long-duration seismic action is studied quantitatively by specific numerical value.It provides a theoretical basis for the design of the isolation system.