| UHV transmission tower structure is characterized by the large height, wind load,ice load and self weight. Especially for the large crossing tower, which height is oftenreach300meters or more and form of structure is very complex. In the design oftransmission tower, the existing design software usually use the whole space trussmodel to calculate, default the connection belongs to the hinged model, ignore thebending stress generated by rod end bending moment. The current study shows that thetraditional hinged or rigid model may different with the actual situation, thus leaving thehidden safe trouble. So the research on semi rigidity tower structure is imminent.Firstly, in this paper, the angle-node plate joints in common test study was carriedout. Then based on the test study the calculation method on moment-rotation curves ofangle-node plate joints has been proposed. And then a comprehensive study on suchjoint was conducted through the nonlinear finite element analysis. And the designsuggestion formula was given. The contrast shows, experiment, theory and the finiteelement results are in good agreement. Finally, the semi-rigid nodes are introduced intothe transmission tower system, a detailed study on semi-rigidity structure load-bearingperformances was developed. The main research contents are as follows:1) In order to investigate the moment-rotation relation of the UHV angle steeltower K-joints，five full-scale tests were conducted. The results showed that the joints ofthis kind have the typical semi-rigid characteristics. The joints usual reach their ultimatemoment because of the shear break of bolts that connect the main angle and jointplate．The angle specifications, gusset plate thickness, bolt strength grade, diameter ofbolt, bolt spacing, bolt number and the yield strength of steel have effect on themoment-rotation relationship of the joints.2) By employing the component method and principle of virtual work, ananalytical model to predict the initial rotational stiffness of angle steel tower K-joints isset up. It is considered that the connection rotation is mainly induced by the deformationof the main angle in shear, bolts in shear, and the hole-wall in bear; considering theplastic deformation of the material, a theoretical method was derived to calculate thewhole process of joint’s moment rotation curve. This method can make a goodperformance in calculating and analyzing the different component related to rotationaldeformation，including the shear deformation of the main angle-steel，the shear deformation of bolt and the extrusion deformation of bolt hole. The theoretical resultsagree well with the experimental results. The theoretical method has filled the gaps intheory research of semi-rigid joints on transmission tower.3) A refined non-linear finite element model was established. The comparison withexperimental results shows that the FEM model can accurately reflect the force anddeformation characteristics this of such joints. In the practical range, the influence ofangle specifications、gusset plate thickness, bolt strength grade、diameter of bolt、boltspacing、bolt number and the yield strength of steel on initial rotational stiffness andultimate moment capacity was studied. The rigidity coefficient of joints was got bycheck. Fitting formula of each parameter was given by using the least square method.Comparison showed that the Kishi-Chen three-parameter power model can predict themoment-rotation relation accurately, can be used as reference for engineering design.4) A general semi-rigid beam element model with a zero-length rotational spring atboth ends of the thin-walled beam was derived from the Hermite interpolationpolynomial and minimum potential energy principle. The semi-rigid nodes wereintroduced into the transmission tower system, considering the geometric non-linearityand material non-linearity, elastoplastic whole process analysis was conducted. Theeffect of joint stiffness, main diagonal angle, main diagonal line stiffness ratio, theinternodes number, the height of the structure, the initial defect on the load-bearingperformances of semi-rigid tower leg structure was studied. Also the semi-rigidperformance sensitivity of structure under various factors was studied. Guidance wasgiven for structure semi-rigid design. |
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