Analysis Of Dynamic Characteristics Of Modular Fabricated Steel Frame Structure

Under the background of the vigorous development of prefabricated buildings in our country,modular building has become the focus of industrialization of architecture in China with its unique advantages such as short production cycle,high degree of mechanization,controllable quality and green environmental protection.However,in view of the late start of domestic research on modular building,and the relevant research results are not rich enough,so this paper will focus on the overall structural performance of modular building.(1)In this paper,combined with the current research status of modular connection joints and structure at home and abroad,the modular plate-inner sleeve connection node is applied to the modular steel frame.In order to facilitate the subsequent analysis and design,according to the structural characteristics and force transmission path of the modular connection node,following the principle of force transmission consistency before and after the simplification,a simplified model of plate-inner sleeve connection node is proposed.ABAQUS finite element software is used to verify the rationality of the simplified method from the two levels of the node and the frame,which proves that the simplification of the joint is reasonable and safe.(2)Using MIDAS/gen 2020 to establish a 4-story modular assembled student apartment calculation model.By comparing the period and vibration mode of the steel frame structure with or without brace,the basic structural form of the student apartment is determined as the modular steel frame structure system with brace on both sides of the model.Performing response spectrum analysis and elasticity time history analysis of the selected calculation model under frequent earthquake,the relevant mechanical performance indexes such as vertex displacement,story drift ratio and stress ratio meet the requirements of the current specification.Through the elastic-plastic analysis,it is found that the module beam yields before the module column under rare earthquake,which indicates that the modular structure belongs to the system of"strong column and weak beam",and has good seismic performance under rare earthquake.(3)Carry out parametric modeling analysis for the 4-story modular prefabricated steel frame structure,and the calculation models of different module layers and length width ratio combination coefficient are established respectively to discuss the influence of length-to-width ratio and floor-number on the seismic performance of the structure and propose the applicable floor numbers and reasonable length width ratio range of modules meeting the requirements of the codes.The response spectrum analysis of 4-10 story modular prefabricated buildings with aspect ratios of 1.0、1.5、2.0、2.25、2.5、2.75 and 3.0were carried out,and the self-array characteristic and displacement response of the models under different plane aspect ratios and floor numbers are obtained,which shows that:(1)the basic natural vibration period of a modular structure is related to the plane aspect ratio and the number of floors.When the number of floors is low(less than 6 floors),the basic vibration period increases with the increase of plane aspect ratio.When the number of floors is more than 6 floors,the basic vibration period decreases with the increase of plane aspect ratio.However,if the aspect ratio is too large,it is easy to cause the module beam to move up and down along the longitudinal edge span of the structure.It is suggested that the ratio of length to width should not be greater than 2.5 for the module building with less than 6 floors,and the ratio of plane length to width for the modular buildings above 6storeys should not be exceed 2.25;(2)The plane aspect ratio has a greater influence on the displacement response of the structure in the Y direction,but it has less influence on the x-direction vertex displacement and story drift angle,and the increase of the number of stories further intensifies the x-direction and Y-direction displacement response of the structure.Under the condition of steel consumption of 80kg/m~2～85kg/m~2,the maximum number of floors of the modular building should not exceed 10.(4)The dynamic time-history analysis of the 4-story model with aspect ratios of 1.0、1.5、2.0、2.25、2.5、2.75 and 3.0,and models with aspect ratio of 2.25 for 4-10 floors under frequent and rare earthquake is conducted by Midas/gen 2020.Analyze the yield mechanism,failure sequence and seismic performance of each model,the results show that:(1)The inter-story drift ratio of the X-direction of models with different aspect ratios are basically the same.Except for the 10-story model,the elastic inter-story drift ratio and elastic-plastic inter-story drift ratio of the other 4-9 story models meet the requirement of the specification.(2)Under the rare earthquake,with the increase of the number of module layers,the plastic hinge position gradually expands from the bottom of the structure to the upper module.The plastic hinge of each model appears first in the bottom module beam,then in the bottom of the module column on the first floor,and finally develops to the module roof beam.Except for the module column on the first floor,most of the module columns are still in the elastic stage,and the module floor beam yields before the roof beam,which avoids the instability of the foundation caused by the failure of the lower module before the upper module,and conforms to the failure mode of traditional steel structure buildings,satisfying the design concept of"strong column and weak beam".