Modeling and simulation of catenary based on negative sag method

The model configuration of simple stitched catenary was studied by negative sag method.The initial calculation under the action of tension and gravity was performed to obtain the vertical displacement of the catenary, and the initial model was restructured.Based on the obtained vertical displacement, the negative sag was reserved in advance to ensure the horizon of contact wire under the initial equilibrium state after a series of the calculations of negative sags.Thus, the dropper length, being satisfied with the initial equilibrium equation, was obtained.Furthermore, the model configuration of the catenary was determined, such as the geometry property and stress distribution.Negative sag method was compared with conventional method.It is pointed that the obtained dropper length by negative sag method is slightly longer than that by conventional method, and the maximum relative deviation of the dropper length is 0.75%.For negative sag method, there is small change of the element stress with the various locations of the element.However, for conventional method, the element stress is constant, and the maximum relative deviation of the element stress is 0.55%.The results show excellent agreement with the comparison data.Moreover, it is indicated that with negative sag method, it is easier to implement the subsequent analysis of pantograph-catenary system, and the method is also effective for complicated catenary including multiple spans.