Static And Dynamic Stability Analysis Of UHP Single Column Cable Tower

Uh-pressure single-pillar cable tower is mainly composed of the main column and cable of the zhang pull structure system,with simple structure,reasonable layout advantages.In the actual engineering,due to the soft structural characteristics of the cable tower,its stability is susceptible to wind load,there is the possibility of collapse in severe cases.Therefore,how to ensure the stable and reliable operation of the cable tower has become an important issue.At present,scholars at home and abroad mainly stand in the perspective of wind response to the cable tower research,but the stability of the research is relatively few.In this paper,the ultra-high voltage single-pillar cable tower as the research object,its static dynamic stability analysis,the main research content is as follows:(1)According to the strain energy equivalency to determine the equivalent cross-sectional properties of the main column,and the use of multi-segment linear rod unit method to simplify the pull line,to draw string deformation and string stress between the nonlinear relationship,and finally,according to the state equation of the pull line derived its equivalent elastic modulus calculation formula;(2)According to the force characteristics of the cable tower to simplify the treatment of its main column,get the bottom end for the hinged,the top for the elastic support of the isometric pressure rod,derived the calculation of elastic support K,and then according to the pressure rod stability theory to determine the main column calculation length coefficient,and on this basis to study the initial pre-stress of the cable and wind speed on its impact;(3)Through the Hamilton principle and the simplified model of the main column derive the partial differential motion equation of the main column,and then use the Galerkin method to discrete the other side equation,to obtain a simpler and more intuitive normal differential equation;(4)Using four-leaf transformation to represent the power load of the pull-line tower,it is replaced by the normal differential motion equation of the main column,to ensure that the resulting linear equation system has periodic T and 2T cycle solution to establish the critical frequency equation of the main column,and then get the power instability and power stability domain of the main column.Finally,the analysis of the main column is used to determine whether the main column has power instability,and to study the wind angle and the initial pre-stress of the pull line on the power stability of the main column.The results show that in the static stability study of the cable tower,the expression of the calculation length coefficient of the main column is determined according to the theory of pressure rod stability.The effect of the initial prestress and wind load on the calculation of length coefficient is also analyzed.To ensure that when the initial prestress of the cable remains unchanged,the calculated length coefficient of the main column on the vertical line is proportional to the wind load;When the wind load is guaranteed to remain unchanged,the calculated length coefficient of the main column in the direction of the vertical line is inversely proportional to the initial prestress,and when the prestress exceeds a certain value,the calculation length coefficient is constant to 1.In the study of the power stability of the pull-line tower,the power instability domain and the power stability domain of the main column are obtained,and the calculation shows that the main column will not have power instability.The influence of wind angle and cable initial prestress on the power stability of the main column of the cable tower is also studied,and when the initial pre-stress of the cable remains unchanged,the wind angle is the most unfavourable condition at 90 degrees,at which time it is most prone to power instability;When the wind angle remains the same,the greater the initial pre-stress of the cable,the more favorable it is to the stability of the power,within the range allowed by the limit carrying capacity of the cable.