Mechanical Behavior Research On Double Angle Bolts Joints Of Concrete Filled Steel Tubular Lattice Wind Turbine Tower

Previous research has shown that: concrete-filled steel tubular lattice wind turbine tower has the advantages of low steel consumption, good low cycle fatigue resistance performance, superior seismic performance, Easy to transport and installation, etc. Its economic and social benefits are higher than traditional cone type wind power tower, however, the node stress is quite complex. This paper takes the mechanical characteristic of a1.5MW wind turbine tower as a reference object which located in Bayan obo area in Inner Mongolia, on the base of the requirements of related standards, designed a lattice tower of Concrete-filled Steel Tubular (CSFT) with four limbs initially by the aid of the SAP2000and load calculations. We selected the most representative node in terms of stress, the nodes in the tenth layer, to carry out experimental research and finite element analysis. Based on the experimental results, the test uses ABAQUS finite element software to further explore the effects of part geometry node capacity and failure modes.The experiment results show that:①Though the stress of the core concrete is small, but it is a key factor that affect the ultimate strength of the concrete-filled tube-plate node, and the grouted steel tube obviously changed the nodes failure modes;②The stress level of the pillar in the node region increases with the Diameter-thick ratio, but the change of the diameter-thick ratio did not have a significant effect on the failure mode of the nodes, under the same load level, the finite element analysis of the diameter to thickness ratio of the steel pipe shows that, when27.38, the curvature of the node ultimate strength decrease with its increasing, the main failure mode of the node is the node plate extreme instability failure, due to the large plate thickness, the ultimate bearing capacity is still high, while27.38, the rate of descent of the ultimate strength slows down, the failure mode of the node was the tube-plate branch point unstable failure, which can take full advantage of node material;③The ultimate strength increase with the ratio of the thickness of the tube wall and the thickness of the node plate γ, the overall trend is rising, and do not show up fall phenomenon. When γ increases to a certain extent, the increase speed of ultimate bearing capacity of the nodes is slowing down, according to the simulation results, it is recommended in the context of the force to meet the requirements of the nodes, try to use a thin gusset plate, γ value should not exceed2.5;④The nodes without the stiffener has a higher requirements for the construction, prone to appear node plate out-of-plane instability, whit a lower carrying capacity, the exists of the stiffener can effectively prevent the node plate out-of-plane buckling, and affects the node failure mode directly, in the meanwhile spreading the stress at the ends of the node plate to a wider range of the tower, making the stress distribution in the node region much more uniform. Since the core concrete supporting role, its contribution to the ultimate bearing capacity is limited.Through the experimental study and finite element parametric analysis, this paper preliminarily obtained the mechanical properties of concrete filled tube-plate node, and puts forward some Suggestions for the node design and processing for reference.