Research On The Mechanical Performance Of The Four-leg Column Wind Power Tower With Lattice Concrete Filled Steel Tube Ball-slab Joints

The lattice concrete-filled steel tubular wind power tower is worth promoting because of its advantages such as easy installation and construction,less transportation constraints and good stress performance.In recent years,our research group has designed and put forward some assembled joints of wind power tower,and carried out relevant static tests.The mechanical properties have been realized well.But the space tower is closer to the actual project,and the lattice tower has more belly bar,the joint area is complex,and the deformation of the belly bar and joint area has a great influence on the whole tower.Based on this,this paper optimized the ball-plate joint on the basis of the universal wrapping,taking the web member-tower column stiffness ratio as a parameter,designed the sphere-slab joint limb column space tower by changing the web member size.Low-cycle repeated tests were carried out on the space tower,and the influence of the web member-tower column stiffness ratio γ on the failure mode,strength,stiffness,ductility,etc.of the tower was studied,and the stress distribution law of each member and node area was obtained.And carried out numerical simulation and parameter expansion through ABAQUS software,analyzed the influence law of the web member-tower column stiffness ratio on the ultimate bearing capacity and ductility of the space tower model,and obtained a reasonable parameter design range.The experiment results indicated that: the failure mode of the space tower was the strength failure of the diagonal web members,the buckling failure of the top transverse web members,cracking at the weld between the root of loading board and steel pipe,and the slip of the inclusion;the hysteretic curves of the tower are in a "bow" shape,and the plastic performance and energy dissipation capacity are good.By increasing the stiffness ratio of the web member to the tower column,the hysteretic curve of the tower was fuller.When the web column stiffness ratio γ from 0.02 to 0.07,the yield displacement and yield load of the tower were increased by 20% and 35.5% respectively,and the displacement ductility coefficient and ultimate bearing capacity of the tower were increased by 7.1% and 30% respectively.The numerical simulation analysis of the tower model was carried out by ABAQUS software.The results indicated that the high stress zone of the space tower model were the connection between the belly bar and the node plate and the connection between the bottom of the loading plate and the steel tube,which was consistent with the test results.On this basis,the expansion analysis was carried out with the bell-column stiffness ratio as the variation parameter.The results indicated that the ultimate strength and the displacement ductility modulus of the tower model were positively correlated with the bell-column stiffness ratio.When γ ≤0.07 both the displacement ductility modulus and the ultimate strength increased greatly;when γ>0.07 the increase rate was obviously reduced.It is suggested that the stiffness ratio of the bell-column to tower should be 0.05-0.07,and the inclusion parts should be strengthened in the design and construction of such space towers,so as to avoid the slippage phenomenon similar to that in the test,which will affect the actual project.