Curving Performance of High-Speed Trains Running on Steep Grades

China has been constructing a large high-speed railway network, which covers the high-speed railways including a large number of steep grades and curves in the mountain area. For example, there are 24 steep grades with gradient larger than 1.5% in Xi’an-Chengdu high-speed railway, in which the longest steep grade (2.5%) has a length of 45 km. Therefore, the high-speed trains have to suffer large traction forces or dynamic braking forces for a long period when they pass through these severe grades. This paper presents a study of the effects of traction and braking on the curving performance of high-speed railway vehicles when the train passes through severe grades. A numerical model considering the track grade, the train traction and braking, and the train-track interaction is formulated. The dynamic curving performance of a high-speed train subjected to heavy traction and braking is investigated. The effects of tractive/braking force, the track gradient, and the train speed are reported. This study is shown to enhance the understanding of the combined effects of curving and traction/braking on the dynamics performances of high-speed trains.