Performance Of Long-span Steel Structure Subjected To Vertical Load Under Uneven Load And Large Load

In order to study the performance of long-span steel structures subjected to non-uniformly arranged large loads under vertical seismic action,this paper,based on the actual project and according to the design scheme of a large-span steel structure industrial factory building under construction,establishes the overall analysis model of the structure by using MIDAS GEN finite element software,respectively,under the non-uniformly distributed large loads on the structure.The internal force performance and the deformation performance under the static action are analyzed numerically.The main contents of this paper are as follows:(1)The whole finite element model is established by using finite element method and finite element analysis software MIADAS GEN,and the modal analysis of the model is carried out.(2)When the large load is symmetrically distributed at both ends of the truss,the axial force transmitted to the upper and lower chords in the middle of the span is small,while when the large load is placed at one end of the truss alone,the large vertical seismic force in the span will be caused by the sudden change of stiffness and mass,which should be avoided as far as possible in structural design.(3)Vertical seismic response of truss under three different large load arrangements(condition 1 is only above one end of the truss,condition 2 is at the middle of the truss span,condition 3 is symmetrical at both ends of the truss)is analyzed.(4)The responses of web members of trusses under two kinds of loads(local large loads and common uniform loads)under vertical earthquake are analyzed.(5)The deformation of roof truss under static load is simulated,and the deformation law of roof truss under different large load positions is compared.Through the study of this project,it is found that:(1)Vertical seismic action should be taken into account when the seismic fortification intensity is 7.(2)When large loads are placed in the middle of the span or symmetrically distributed at both ends of the truss,the axial force transmitted to the upper and lower chords of the span is small in vertical earthquake,while when large loads are arranged at one end of the truss alone,the large vertical seismic force will be caused in the span due to the sudden change of stiffness and mass,which should be avoided as far as possible in structural design..(3)The axial force influence coefficient of web member in truss under vertical seismic action is large in span and small at both ends,and the greater the load the truss bears,the higher the sensitivity of web member to vertical earthquake.It is suggested to increase the stiffness of web member in midspan.(4)By increasing the stiffness of the secondary beam in the large load distribution area,the vertical deformation of the truss in the large load distribution area above the middle or side columns can be effectively controlled within the allowable scope of the code,but the large load in the mid-span area can not be avoided in this design.(5)Under the influence of local heavy load,the truss will appear excessive deformation beyond the allowable deformation value in the middle of the span,forming a weak area.The stiffness of the secondary beam in the middle of the span should be paid more attention in the design.It is suggested that the stifness of the secondary beam in the middle of the span should be raised to the same level as that of the secondary beam in the large load distribution area.