Truck Brake Hub Temperature Rising Model Based Slope Design for Long Longitudinal Downgrade Section in Expressways

The brake hub temperature of the truck at the toe of the slope, and the distances of the truck to the top of the slope at a brake hub temperature of 200°C and 260°C were studied separately using the brake hub temperature rising model proposed by PIARC. We used two profile design schemes of long and longitudinal downgrade section in expressways: a gradient slope scheme and a unique slope scheme. Also, the heating rate of brake hub, the correlation between the temperature rising and the truck weight, and the temperature rising characteristics at different velocities were analyzed under the two different schemes. Results obtained are as follows: the brake hub temperature of the truck on the slope with a unique slope is lower than that with gradient slopes, and the heating rate is linearly dependent on the travel distance; the temperature difference of the brake hub temperatures at two different downgrade sections decreases with increasing truck weight at a same velocity; and the temperature difference under two different sections changes little with the variation of velocity at a same truck weight. Both the distances of the truck to the top of the slope at a brake hub temperature of 200°C and 260°C change with different slope length, and two threshold lengths are obtained for the two temperatures: 15km and 20km. The distance of the truck to the top of the slope at unique slope scheme is greater than that at gradient slope scheme when the slope length is less than threshold length. When the slope length is greater than the threshold length, the gradient slope scheme is superior to the unique slope scheme.