Stability Of A Two Fixed-ends Bar With Middle Elastic Support

The steel tower structure has the characteristics of broad application and good development prospect so that it occupies an important position in the field of steel structure.The structure system of large tower is complex and difficult to design,and it has a long service life after completion.As the most important stressed member,the tower column bears the constant load,live load and wind load of the structure.In recent years,the plane form of the new tower structure is close to the circle.The tower column is supported by the horizontal bar,but its radial constraint is insufficient.Therefore,the stability is directly related to the overall safety of the structure.Sufficient attention must be paid to the stability of structures and components in design.In the process of design simplification,both ends of the column are regarded as hinge,and the length coefficient method is used for calculation.However,under the interaction of the ends and the adjacent members,it is inaccurate to take the distance between the two ends of the bar as the calculation length.At present,a detailed study has been made on the constraint of hinged ends,but there is a lack of theoretical basis for a two fixed-ends bars.This paper studies the stability of a two fixed-ends bar with elastic support under axial compression.The main contents are as follows:Firstly,the relation curve between the buckling bearing capacity of the bar and the stiffness of the spring support is derived by solving the differential equation for the model of a two fixed-ends axial compression bar with spring support in the middle,and the relation curve is modified by combining structural mechanics analysis and finite element calculation.Secondly,the axial compression experiment about a two fixed-ends round steel bar with spring support is designed.Springs that meet the requirements are selected and the number of springs is adjusted to change the support stiffness.Observe the experimental phenomena and analyze the characteristic forms of instability under different supporting stiffness.According to the test results,the theory curve and approximate calculation formula are verified.Thirdly,simplify the polygonal steel tower structure in the project,select the local model with the support web as 180°.In the instability experiment of the axial compression round steel pipe with structural support,adjust the wall thickness of the supporting column and use space matrix displacement to calculate its equivalent support stiffness is calculated.The purpose is to explore the similarities and differences of the instability state between the structural support and the spring support.Finally,the characteristic value buckling analysis method is used to calculate the buckling bearing capacity of a two fixed-ends bar under the structural support.By comparing the test results,it is found that the torsional stiffness of the structural support beam can improve the stability bearing capacity of the axial compression bar,which is the basis of safety reserve in engineering design.