Study On Lemniscate Curve In Design Of Alignment Of Interchange

The present interchange horizontal alignment is combined with liner,circle and maneuver curve. But this design method has some limits.Being directed these limits, this paper puts forward the conception of integral small central road of interchange. That is , taking advantage of the similarity in the overall shape between Lemniscate curve and small central road, applying the whole Lemniscate curve to small central road, which is studied in the paper.According to the analyses of geometry characters and road usage performance of the Lemniscate curve, this paper testifies the feasibility of the usage of the Lemniscate curve. Based on the practical constitution , the common formula to oblique interchange is derivated. Just for a convenient design and construction, the author has chosen a design parameter of Lemniscate curve, and programmed with Visual Basic language to solve the problem of curve location. Meanwhile , the paper has made objective comparison between the two types of small central roads. At last, a suggestion is put forward that the design program of Lemniscate curve should be added into the related design software as a subprogram.Through deep study, major conclusions are as follows:â‘ The Lemniscate curve could meet the road usage performance of the small central road, so it is feasible to apply Lemniscate curve as a whole.â‘¡The Lemniscate curve, as an integral small central road, has its advantages as well as disadvantages.â‘¢The Lemniscate curve is recommended when the maneuver curve is long enough in a small central road of interchange.â‘£This design method ,which has jumped out the traditional three elements combination method, is a supplement to the present design method.