Seismic Performance Analysis Of PC Base-isolated Multi-tower Structural With A Large Floor Under Extremely Rare Earthquake And Site Settlement

With the advancement of building industrialization,the precast concrete structure is developing rapidly.Compared with the traditional cast-in-place structure,it has significant advantages such as standardization,high quality,fast construction,low energy consumption,and less labor.However,the precast concrete structure still has some problems,such as poor integrity and low seismic performance currently.The isolated structure with laminated rubber bearings,as a mature structural damping technology,has been applied in a large number of projects,experienced the test of earthquake and is generally recognized.The emergence of precast concrete isolation structure not only meets the needs of industrialization of buildings,but also meets the expectations of the owners on the seismic safety of buildings.It is an important direction for future development of buildings.The concept of extremely rare earthquake has higher requirements for the seismic fortification goal of the structure.The ability of the precast concrete isolation structure to resist the extremely rare earthquake is a new problem that needs to be discussed urgently.Site settlement is one of the main causes of civil engineering accidents.In the northwest region,the uneven settlement of foundation caused by it will lead to structural inclination and cracking,which seriously threatens the stability and safety of the overall structure.When uneven settlement is coupled with extremely rare earthquake,few scholars have explored the seismic performance of assembled isolation structure.In this paper,the base-isolated multi-tower structure with a large floor is taken as the research object to discuss the seismic performance under the action of extremely rare earthquakes and the coupling action of uneven settlement.The main research and conclusions are as follows:(1)The mechanical characteristics of the beam-column joints of the precast concrete structure are systematically elaborated,and the refined modeling of the joints of the precast concrete structure is carried out;the ETABS software is used for the seismic isolation design of the base-isolated multi-tower structure with a large floor,and the layout of the seismic isolation bearings is determined.The finite element model of the base-isolated multi-tower structure with a large floor and PC base-isolated multitower structure with a large floor are respectively established in ANSYS under symmetric and asymmetric layout.(2)By inputting bidirectional seismic waves to the RC structure and the PC structure,the differences in seismic performances such as dynamic characteristics,floor response,energy dissipation,and stress of the large base plate under the action of rare earthquakes and extremely rare earthquakes are compared and analyzed.(3)The settlement of the symmetrical RC structure and the symmetrical PC structure foundation was analyzed and calculated,which affected the seismic performance of the structure only under the effect of self-weight load and coupling with the extremely rare earthquake,and the variation rule of the seismic performance index of the structure under different working conditions was obtained.(4)The symmetrical RC structure and symmetrical PC structure are discussed as the foundation settlement continues to occur,the mechanical properties of the seismic isolation layer under different settlements and the seismic behavior of the superstructure;The influence of uneven settlement and extremely rare earthquake on the overall safety of the structure is summarized.The results show that the seismic performance of PC structure was weaker than that of RC structure but the difference was not large;Under the extremely rare earthquake,the displacement of the isolation bearing increased significantly,and the damage of the upper structure was more serious.Therefore,in the isolation design,the larger diameter isolation bearing should be selected,and the seismic structural measures of the upper structure should be carefully reduced.After the uneven settlement,the seismic performance of the structure was significantly reduced,and under the local settlement,the isolation bearing was prone to tensile stress;The early stage of uneven settlement had the greatest impact on the structure.The foundation settlement shall be paid attention to in time during the construction process and later stage monitoring,and it shall be found and handled as soon as possible to prevent the isolation bearing from failure due to excessive tensile stress.