Dynamical Effects of the Increase of the Axle Load on European Freight Railway Vehicles

Round 1

Reviewer 1 Report

The article is devoted to a promising topic related to increasing the capabilities of railways and improving the construction of freight cars. For example, the railways of Ukraine introduced an axle load for freight cars of 25 tons as standard across the entire railway network. It is desirable in future studies to pay attention to the dynamic effect on the railway track and on the wear of wheels and rails, because the increase in axle load affects the railway infrastructure. 

As recommendations, the authors should argue for the introduction of a coefficient of friction of 0.4, instead of 0.3, as a standard coefficient of friction for metal-to-metal contact. The term convoy needs interpretation.

Author Response

This document is a rebuttal including a detailed response to the comments of the reviewers after their careful review process.

The authors wish to thank the reviewers for their comments and suggestions which helped to improve the manuscript.

Reviewer #1: "The article is devoted to a promising topic related to increasing the capabilities of railways and improving the construction of freight cars. For example, the railways of Ukraine introduced an axle load for freight cars of 25 tons as standard across the entire railway network. It is desirable in future studies to pay attention to the dynamic effect on the railway track and on the wear of wheels and rails, because the increase in axle load affects the railway infrastructure.

As recommendations, the authors should argue for the introduction of a coefficient of friction of 0.4, instead of 0.3, as a standard coefficient of friction for metal-to-metal contact. The term convoy needs interpretation."

 

The reviewer is totally right, and future studies will focus on other important aspects such wheel and rail wear and the evaluation of loads on turnout sections. The authors adopted a friction coefficient equal to 0.4 since it is the standard value adopted for wheel-rail rolling contact. This value is the typical wheel-rail friction coefficient in dry conditions. The term convoy was replaced with train.

Reviewer 2 Report

The purpose of this paper is to identify the impact of an increased axle load on railway wagons to the dynamical parameters. The authors have used the Italian railway lines to simulate their hypothesis.

This is an interesting subject, written under a structured format.

The information and data is presented in a logical sequence that supports the main question and hypothesis asked and the scope of the paper.

I would suggest to modify the abstract in order to focus more on the main aim/scope of the research and some results.

Author Response

Reviewer #2: "The purpose of this paper is to identify the impact of an increased axle load on railway wagons to the dynamical parameters. The authors have used the Italian railway lines to simulate their hypothesis.

This is an interesting subject, written under a structured format.

The information and data is presented in a logical sequence that supports the main question and hypothesis asked and the scope of the paper.

I would suggest to modify the abstract in order to focus more on the main aim/scope of the research and some results."

Answer:

The abstract has been modified in order to describe the aim of the paper.

Reviewer 3 Report

The idea of increasing rail traffic capacities by allowing higher loads per axle is an oftenly discussed possibility. The article at hand gives theoretical background and simulation research in order to provide a basis for an implementation of higher axle loads.

Here, the approach is scientifically sound described and valuable results are presented. Therefore, the article can be accepted in the present form.

Still, some remarks for polishing the article:

- section 2.4.: it is said, that Kalker's FASTSIM algorithm was used to implement the wheel-rail contact. Maybe a short description could be added why it was chosen and which pro's and con's appear.

- section 2.5.: Simplifications on the traction effort implementation are described. Maybe a short classification description could be added, why these simplifications were applied and why simulations still are representative.

- chapter 5.: Maybe the authors could fine-tune the conclusion answering the following question: Is it possible to give a more distinct assumption on how much a bad track would influence the critical Q loads?

Author Response

Reviewer #3: "The idea of increasing rail traffic capacities by allowing higher loads per axle is an oftenly discussed possibility. The article at hand gives theoretical background and simulation research in order to provide a basis for an implementation of higher axle loads.

Here, the approach is scientifically sound described and valuable results are presented. Therefore, the article can be accepted in the present form.

Still, some remarks for polishing the article:

- section 2.4.: it is said, that Kalker's FASTSIM algorithm was used to implement the wheel-rail contact. Maybe a short description could be added why it was chosen and which pro's and con's appear."

Answer: The authors adopted the FASTSIM algorithm since it is the standard algorithm used to solve the tangential problem within dynamic simulations.

"- section 2.5.: Simplifications on the traction effort implementation are described. Maybe a short classification description could be added, why these simplifications were applied and why simulations still are representative."

Answer: The authors propose a simplified traction force since the aim of the work is to evaluate the impact of heavier vehicles on track by considering the limit proposed by EN14363. The standard does not take into account wear phenomenon, which are strongly related with the performance of the traction control. A sentence was added to clarify this aspect.

"- chapter 5.: Maybe the authors could fine-tune the conclusion answering the following question: Is it possible to give a more distinct assumption on how much a bad track would influence the critical Q loads?"

Answer: High track irregularities have not been considered since the axle-load increase it is possible only on high quality tracks, where maintenance operations allow to maintain low irregularity levels. It is evident that the increase of the axle load on low quality track is not feasibility due to the increase of dynamic track loads.