Study On Optimal Design Method Of Section Steel Jointed Assembly Concrete Column

In recent years,the Ministry of Housing and Construction has issued a series of policy documents on building industrialization,among which the prefabricated building is the main form of transformation and upgrading of the construction industry,in line with the concept of green and sustainable development,and has been widely used in industrial and civil buildings.As one of the main structural forms,the connection between the assembled members of the prefabricated concrete frame structure is the key part of the whole frame.The security,construction ease and long-term stability of the assembled concrete frame directly affect the overall mechanical performance of the prefabricated frame.Based on the comprehensive evaluation of the advantages and disadvantages of the common connection methods of prefabricated concrete columns,this paper proposes a new assembly form of section steel connection prefabricated concrete columns,carries out multi-parameter finite element analysis on the seismic performance of the prefabricated concrete columns,and puts forward some suggestions for the optimal design.Compared with the research results and engineering application status of prefabricated concrete column at home and abroad,this paper puts forward the prefabricated concrete column assembly form,structure design idea and parameter selection scheme of section steel connection.Through finite element numerical simulation,the following research work is carried out: the local strength and stability of the section steel connection area are checked,so as to explore the optimization design method of prefabricated concrete column based on the section steel connection form;Furthermore,the feasibility and reliability of the finite element parameter analysis are verified by comparing the finite element values of the orthogonal-double H-beam connection and box-type steel connection assembly column with the relevant experimental data.Further,the finite element simulation analysis of various structural or design parameters of section steel was carried out,and the influence law of section steel connection form,section steel area height,joint setting position,section steel plate thickness,component stress state(axial compression ratio)and so on on the seismic performance of the assembled column was explored.Using hysteretic curve,skeleton curve,energy dissipation,ductility,stiffness and other indicators to evaluate the performance of different assembled concrete column steel joints,by comparing with the results of cast-in-place concrete columns,the design suggestions of assembled column steel joints based on the principle of equal stiffness and equal strength were put forward.Finally,combined with the relevant specifications and theories of concrete structure,steel structure and prefabricated structure,the optimization design formula and suggested value of stiffness,anchorage structure and bearing capacity design of section steel connection are proposed.Specific conclusions are as follows:(1)The results of finite element simulation are in good agreement with the actual test results.The variation trend of hysteresis curves and the distribution of concrete damage and stress and strain are roughly the same.The mechanical and seismic properties of the prefabricated concrete columns connected by orthogonal double H-section steel joints and box steel joints are equal to those of the cast-in-place concrete columns.(2)The variation trend of hysteresis curves of prefabricated concrete columns connected by various types of steel joints(orthogonal double H section joints,box section joints,circular section joints,diagonal double H section joints,and double Σ section joints)is basically the same,and the height of steel joints in the connection area has little influence on the seismic performance of assembled specimens.The larger the section stiffness of the section steel in the connection area is not the better.It is necessary to comprehensively consider the appropriate ratio between the section stiffness and flexural capacity of the precast column body and that of the section steel in the connection area,so as to ensure that the assembled column specimens have the same seismic performance as the cast-in-place column and have good ductility.When the section stiffness of the section steel in the connection area is too thick,The variation trend of the maximum bearing capacity of the assembled column members is small.(3)The section steel connection is set at the anti-bending point in the column,so the overall seismic performance of the assembled column is the easiest to ensure,the rigidity of the section needs to be the minimum and the most economical,and has good ductility.The area near the bottom of the column is not recommended to be used as the assembly location of the section steel connecting the assembly column.Because of the setting of the connection area here,the overall seismic bearing capacity of the assembly column is greatly reduced compared with that of the cast-in-place column,and even the failure of the connection area occurs in advance.For small or medium columns,in order to facilitate assembly construction,it is suggested to set the connection position of section steel 800mm～1200mm away from the bottom of the column.Reasonable section design topic of section steel ensures that the various mechanical properties of the assembled columns under this connection scheme are basically the same as those of cast-in-place columns.(4)Based on the design criterion of equal stiffness and equal strength with cast-in-place concrete column,the paper presents the calculation method of the integral linear stiffness of the prefabricated concrete column with section steel connection.