| Concrete-filled steel tubular lattice wind tower has smaller displacement and lower stress level than cone-tube tower when it subjected to wind load,and it have superior mechanical properties.At present,the research on the joints of CFST lattice wind tower mainly focuses on the intersecting joints and tubesheet joints.However,the construction process of the above two joint forms is complicated,the welding defects are easy to occur and the construction quality is difficult to control.In view of the above situation,a new type of universal wrapped Y-joints is proposed in this paper.The mechanical behavior test and finite element non-linear analysis of Y-joints are carried out.The main research contents and results are as follows:(1)Taking a 1.5MW conical tube wind tower in Baiyun Obo mining area as a design reference model,a three-limb concrete-filled steel tube lattice wind tower is designed.The internal force of the tower is calculated by SAP2000 general structure analysis software,and the distribution law of the internal force of the tower and the most disadvantageous position of the tower joints are obtained,which provides a theoretical basis for the design and manufacture of the test joints.The results show that the overall force of the tower is uniform and continuous,and the internal force ratio of the compression and tension diagonal webs is controlled between 1.04 and 1.09;The joints between the 8th and 9th floors of the tower are the disadvantageous locations of the tower joints.(2)Based on the most disadvantageous position of the joints calculated by the internal force of the tower,four Y-joint model specimens were designed and manufactured,and the static load test was completed.The influence of the wall thickness of the cone platform and the height of the cone platform on the mechanical behaviors of the joints was studied.The analysis of the experimental phenomena and the force characteristics shows that the failure modes of Y-joints are classified into two types,buckling failure mode and shear-buckling failure mode.(3)Combined with the experimental phenomena and the mechanical characteristics of the joints,the load-deformation curve of the web member,the stress distribution law in the core area of the connector and the equivalent stress distribution law in the cone platform area are analyzed.The results show that the load-deformation curve of the web member is complete,the elastic-plastic stage is long,and the web member has good deformation and load-bearing capacity;the core area of the connector is the action point of tension and compression force,the overall stress level is high,and the lower shear end is the high stress area of the component;the equivalent stress on the extruded side of the cone platform is about two times of the equivalent stress on the non-extruded side.The stress distribution on the cone platform is more uniform.(4)The finite element model of Y-joints is established by using ABAQUS finite element analysis software.The reliability of the finite element model is verified by comparing the experimental data with the results of the finite element model analysis.On this basis,the finite element parameter expansion analysis is carried out,and the reasonable range of the wall thickness of the cone platform,the height of the cone platform and the thickness of the web member wall is obtained.The analysis results show that the concrete with strength grade C30 is recommended as the core concrete of the tower column in the design and use of the joints;the optimum height of the cone platform is 65 mm in the design of the ball table,and it is advisable to take the wall thickness of the cone platform less than 10mm;it is reasonable that the thickness of the web member wall should be taken less than 7mm in the selection of the web member. |
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