Study On Seismic Collapse And Progressive Collapse Performance Of Modular Buildings Based On Mega Structures

Modular buildings can effectively solve various problems of high energy consumption and environmental pollution in the construction of traditional cast-in-place structures.At present,there are few high-rise and super-high-rise buildings using modular building technology at home and abroad.It is the trend of future development and research to apply modular building technology to high-rise and super-high-rise buildings because of the dense population and the shortage of land in China.This paper combines the advantages of modular construction such as high quality,short construction period,environmental protection and low energy consumpt io n with the advantages of huge lateral stiffness of mega-frame structure.The substructure of megaframe structure is in the form of modular steel frame box structure,and modular constructio n technology is applied to super-high-rise buildings.The main contents and conclusions of this paper are as follows:(1)Seismic performance analysis of modular substructures based on mega-structures.The elastic-plastic time-history analysis of the whole structure is carried out after selecting seven long-period main and aftershock motions.The seismic performance of modular substructures based on mega-structures under long-period main aftershocks is evaluated from two aspects: the maximum inter-story displacement angle and the damage distribution at the joints.The results show that when the floor meets the assumption of rigid floor,the maximum interstory displacement angle of the modular substructures based on mega-structure meets the specification limit under the action of long-period main aftershocks of 7 degree 220 gal.The connection at elevation of the first floor of modular substructure is damaged.Under the action of 8 degree 400 gal long period main aftershocks,there is a 28.57% probability that the maximum inter-story displacement angle exceeds the specification limit.In addition to the damage of the connection at the elevation of the first floor floor of the modular substructure,there is a 28.57% probability of damage along the whole floor of the connection between the main and sub-structures in the lower mega-range.(2)Seismic collapse resistance analysis of modular substructures based on mega-structures.Under the condition that the floor does not satisfy the assumption of rigid floor and that the main structure and the substructure have no restraint action,taking modular substructures as the research object,the seismic collapse resistance of modular substructures under long-period main aftershocks is evaluated from the aspects of maximum inter-story displacement angle,joint damage,distribution of effective plastic strain of structural members and buckling of steel columns.The results show that the substructure will not collapse under the action of long-period main aftershocks of 7 degree 220 gal.Under the action of 8 degree 400 gal long period main aftershocks,The maximum inter-story displacement angle has a probability of 57.14% exceeding the specification limit.There is a 28.57% probability that the maximum inter-story displacement angle will not only exceed the specification limit,but also 25% of the steel columns on the first floor will buckling and instability,and the substructure will collapse.The ratio of maximum inter-story displacement angle between aftershocks and main shocks is less than 67% in most cases,which is relatively smal,reaching more than 80% in some cases.Effective plastic strain of components under earthquake action concentrates at both ends of beam of outer box structure.The effective plastic strain of the structure can be increased by up to 8.34% under the action of long-period main aftershocks of 8 degree 400 gal.The connection at elevation of the first floor of modular substructure is damaged.(3)Progressive collapse resistance analysis of modular substructures based on mega-structures.The progressive collapse of modular substructure is analyzed when single column,single cluster column failures occur in different floors and double column and double cluster column failures occur in the first floor.The two results of failure and non-failure of connection of modular substructure in the process of progressive collapse are compared.It is discussed whether the failure of the connection can be prevented by increasing the shear strength of the bolts at the connection,so as to prevent the progressive collapse.The results show that when the connection fails due to insufficient shear strength of bolts in the process of progressive collapse,The higher the failure floor of single column or single cluster column is,the greater the vertical failure displacement is,and the more likely the progressive collapse will occur.When the connection does not fail and single column or cluster column failures occur on the first floor and the fifth floor,there is little difference in the ability of resisting progressive collapse between the first floor and the fifth floor when single column or single cluster column fails,and the failure displacement is obviously lower than the limit value.The ratio of failure displacement to limit value is in the range of 41.2%-58.0%,and there will be no progressive collapse.The first floor and the fifth floor cases can increase the shear strength of bolts at the joint more easily and economically than the ninth floor case when the single column or cluster column fails,so as to avoid the failure of the joint and consequently avoid the progressive collapse.When the outermost double-column or double-cluster column of the first floor fails,the failure box structure will collapse to the side of the failed double-column,and progressive collapse will occur.When the internal double-column or double-cluster column fails,the modular substructure approaches the state of progressive collapse.Therefore,it is suggested to add support at the first floor of the module substructure to improve the ability of the structure to resist progressive collapse.