Designing roads for heavy vehicles may seem like a straightforward task. But there is more at stake, especially with regard to heavy duty vehicles. Taking the heavy vehicle research into consideration, Ms. K. Kavinmathi and Dr. S. P. Atul Narayan, from the Department of Civil Engineering, Indian Institute of Technology Madras, and Dr. Shankar C. Subramanian, from the Department of Engineering Design, Indian Institute of Technology Madras, study the asphalt pavement common on highways, where the truck or any other heavy vehicle has to make a horizontal curve. This may seem like an ordinary problem, but the authors of this paper have done extensive research on this subject to show that it is not such an easy task and efforts must be taken to rethink the design of asphalt pavements.
Till now, in various other researches, lateral forces on the tyres and the vertical load have been considered. But the suspension on the load transfer and the cornering bahviour of the vehicle at the turn has not been considered. Also, the quality of the road and dynamic load transfer has not been taken into account while carrying out these experiments. Thus there is a necessity to study the dynamics of lateral load transfer in horizontal curves using a more advanced vehicle dynamics model and evaluate the effect of such load transfer on the response of pavements.
To address the lacunae in the existing research in this area, in this study, a software called IPG TruckMaker® was used to simulate a heavy load vehicle at the horizontal curve of a pavement. This software has been used in other studies as well. It can be used to simulate the movement of trucks on a generated road profile. In the background, the software solves the governing equations of motion for a full truck model. Using this, the dynamic load transferred at the tyre or road can be collected.
The following factors were studied in detail:
1. Speed of the truck.
2. Gross vehicle weight of the truck.
3. Radius of horizontal curve.
4. Surface roughness of pavement.
After the study, the following conclusions were made:
1. The relative damage was found to be same on both axles of the wheels of the vehicle. This is because the dynamics of the suspensions play a considerable role in determining the extent of increase in damage with the axle being on a horizontal curve.
2. According to IPG TruckMaker®, the damage in the curved section was relatively higher as compared to most cases.
3. The speed of the vehicle and the radius of the horizontal curve played an important role in the relative damage in the curved section. Also, it was found that the higher the laden weight, the higher was the load transferred to the outer tyres of the truck and thus the relative damage was more.
4. The damage in the curved section relative to a straight section could be 6 times higher in some cases. Even for relatively larger radii and low vehicle speeds, the relative damage in the curved section was up to 40 percent higher.
5. The roughness of the pavement also played a major factor in contributing to the relative damage. The damage in the curved section would be approximately 170 to 300 percent if the roughness of the pavement was taken into account.
It is to be noted, that in this study too not every factor is taken into account. Many factors such as the tread of the tyre, dynamics of the tyre, and its mechanical characteristics have not been considered. Also, an analysis using a viscoelastic continuum damage model may provide a more accurate estimate of the effect of the increased vertical load and the lateral load at the horizontal curve. The pavement structure is also to be studied in more detail.
The conclusion declares that the pavements for horizontal curves need to be designed separately. The dynamics of the vehicle and the load transfer should also be taken into account. The restructuring of pavements needs further study and can be considered as a future work.
Article by Akshay Anantharaman
Here is the original link to the paper:
https://www.tandfonline.com/doi/full/10.1080/14680629.2021.1977683
