Computer aided design method of egg-type curve in road route design

Abstract

The invention provides a computer aided design method of an egg-type curve in road route design and belongs to the technical field of road computer aided design. According to the design method, on the basis of unidirectional curves which cannot directly form a compound curve and have short straight lines or a C-type curve, the design steps that a tangent point D is selected on a small circular curve of the unidirectional curve, a tangent point C is selected on a large circular curve of the unidirectional curve, a middle easement curve is calculated, and middle easement curve data are corrected are conducted, a coordinate drawing is drawn point by point, and the egg-type curve design is finished. According to the egg-type curve formed through the design method, the situations that the unidirectional curves cannot form the compound curve and the short straight lines exist are eliminated, the problem of unfavorable lines such as the C-type curve with a curvature zero point is solved, the traffic safety environment is obviously improved, the method can be widely applied to the unidirectional curve linear design of overpass ramps and various roads, and the design and calculation method is simple and convenient.

Description

Technical field [0001] The invention belongs to the technical field of road computer-aided design, in particular to a method for computer-aided design of oval curves in road route design. Background technique [0002] To form an oval curve, theoretically, it is formed by inserting a transitional curve between two large and small circles, that is, a clothoid curve. There are currently three methods, one is to insert an intercepted section of the clothoid curve; the other is to use a transitional circle curve; the third is to Intercept and insert a cubic function curve that meets the requirements. For the first method, the use of intercepting a section of the clothoid curve to form an oval curve is advocated in the design of road routes, but in practice, due to the difference in curvature radius, distance and relative position between the two circular curves, it is very difficult to use difficulty. The current design calculation method is in A 2 = L S R 2 On the clothoid ...

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Problems solved by technology

However, through a large number of computational studies, it has been shown that connecting to Dayuan R at this time 1 He Xiaoyuan R 2 The clothoid curves of the two circular curves and the initially determined clothoid curves are not the same clothoid curve. In other words, the clothoid curve segment is used as the intermediate transition curve. Otherwise, it is impossible to eliminate the sudden change at the junction of large or small circles; in addition, it is difficult to find a suitable baseline for actual surveying and setting out, and the current route design software cannot handle this problem well. Therefore, the use of intercepting a clothoid curve The design calculation method of forming an oval curve is theoretically possible, but it is almost impossible to use it in the actual route survey and design

In order to eliminate the short straight lines between the same curves, or the C-shaped curves with zero curvature, which is very unfavorable to driving safety, using a transitional curve as an alternative is sometimes used, but the disadvantages It is impossible to eliminate the mutation of the radius of curvature, and it often occurs that the difference in the radius of curvature when multiple circular curves are combined with complex curves is greater than 1.5 times

For the third case, the cubic curve is used as the transition curve, which is more complicated, and it is difficult to determine the parameters for actual use. It is difficult to establish an equation that meets the actual needs, so it is hardly used.

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