Study On Eccentric Collision Of Adjacent Base-isolated Structure And Simulation Of Progressive Collapse Under Near-fault Seismic Motion

In recent years,seismic activity has been frequent.China's fifth-generation?Seismic ground motion parameters zonation map of China?stipulates the value of four-grade ground motion : Excessive,Basic,Rare,Rarely encountered.Compared with the fourth generation zoning map,the concept of extremely shocked ground motion was proposed at first time which makes it difficult for traditional seismic structures to meet seismic requirements.While base-isolation structures can reduce and consume seismic energy through seismic isolation layers and improve the seismic performance of structures.So isolation technology is widely used in the construction and reinforcement of important structures.For some complex isolated structure,we usually divided it into a number of regular structural units.Under the near field ground motion,the isolation layer easily produces larger horizontal displacement and collide with the adjacent structures,Especially to some buildings that have been reinforced by isolation.The isolation structure is generally used in primary and secondary school buildings,hospitals,museums,communication centers,buildings for precision processing,and the nuclear industry.Once a collision occurs that causes structural collapse,it will bring serious casualties,economic losses and social impact.At present,most studys on collision only focus on the collision between the traditional aseismatic structures,the collision between isolation structures and the surrounding retaining walls,but the eccentric collision between adjacent isolated structures is seldom involved.In this paper,according to the characteristics of the structure layout of a complex isolated dormitory building in a university,the spacing between the isolation units is discussed.The following points are mainly discussed.(1)In this paper,the common method of collision analysis is summarized and analyzed.The display dynamic analysis software LS-DYNA is introduced,and the element type and material constitutive model in this paper is briefly introduced.The multi-scale theory is introduced,and the establishment method of multi-scale model is introduced in detail.The rationality of unit type and material constitutive selection is verified by shaking table test,and the validity of multi-scale connection is verified.(2)For a complex earthquake-isolation dormitory building of a university,firstly use the structural design software YJK to calculate reinforcement,and then usethe LS-DYNA to build a multi-scale analysis model which with equal height,and choose the near-field vibration Northridge as the earthquake input.The effects of eccentric impact on structural acceleration,displacement,floor torsion angle,floor displacement angle and corner column torque of the structure under different pitches and different PGA are discussed.The influence of different spacings and different PGA collisions on the contact force between the two isolated structures is then analyzed.(3)The multi-scale analysis model of unequal layer height base-isolated structures is established.The micro mechanism of collision between two isolated structures is studied,and the continuous collapse of key components is simulated in the whole process.The transfer process of the force in the gravity redistribution process after the failure of the key members of unequal layer height base-isolated structures is analyzed.