A low-cost, mobile real-time kinematic geolocation service for engineering and research applications

Centimetre accurate geolocation service is beneficial to a wide range of applications, ranging from sports engineering, civil infrastructure, autonomous vehicles, surveying to digitisation of historically significant structures. Previously, these features were confined to prohibitively expensive commercial hardware, requiring technical knowledge and experience to operate. Continued technological advancements have seen the miniaturisation of electronics and antennas, coupled with an increase in the number and performance of global navigation satellite systems (GNSS) by various nations and organisations, providing global signal coverage. This paper demonstrates a low-cost, mobile, real-time kinematic (RTK) geolocation service for engineering and research applications, fabricated from components readily available from commercial suppliers. This solution, consisting of a mobile RTK base station and RTK rover, provides centimetre-accuracy performance up to a distance of 15 km away from the base station. Correction data is transmitted over the internet using free and open software solutions. The small footprint of both the RTK base station and RTK rover, provides versatile applications even in remote locations. The performance of the geolocation service is validated using field experiments, comparing measurements against state-of-the-art photogrammetry, light detection and ranging (LiDAR) and digital level measurement technologies. The authors encourage the adoption of the RTK geolocation solution based on the calibrated results.4Tel Pty is gratefully acknowledged for sponsoring the Chair in Railway Engineering in the Department of Civil Engineering at the University of Pretoria.http://www.elsevier.com/locate/ohxam2022Civil Engineerin

Performance of resilient rail pads used in Tubular Modular Track under South African service conditions

Of the many requirements modern railways must meet, those of safety, speed, efficiency and cost-effectiveness are paramount. These requirements have been the driving force for railway engineers to develop new and innovative track structures. Conventional track structures consisting of a superstructure resting on a ballast bed have over time given way to ballastless track structures. These innovative structures, though often costly to construct, remain feasible due to the decreased maintenance requirements. Lower maintenance requirements lead to fewer interruptions to traffic, and considerable cost savings over the design life of the structure.http://www.civils.org.za

Development and calibration of a wireless, inertial measurement unit (kli-pi) for railway and transportation applications

With the dawn of the fourth industrial revolution characterized by the rapid advancement and development of 3D printing technologies, miniaturization of transducers and the emergence of big data applications, the railway industry stands to benefit from the implementation of these technologies in the immediate future. “Kli-Pi” is a demonstrative prototype instrument, incorporating a number of these recent advancements in the form of a 9 DoF (Degree of Freedom) IMU (tri-axis accelerometer, gyroscope and magnetometer inertial measurement unit) that can be applied as either an intelligent ballast particle embedded in a railway track, or can be fixed to a particular component under study to measure various response parameters (linear acceleration and angular velocity), recording up to 3,000 data samples per second. The development of both the instrument and its accompanying 3D printed exoskeleton (or shell) is discussed, together with a brief overview of preliminary field testing and its results.Papers Presented at the 2018 37th Southern African Transport Conference 9-12 July 2018 Pretoria, South Africa. Theme "Towards a desired transport future: safe, sufficient and affordable"

The development of a simplified track modulus calculation procedure

With the constantly increasing demand for heavy freight transportation, railways have become an extremely important element in the economic wellbeing of any country, and particularly in a developing country like South Africa. It is thus the duty of track engineers to maintain a continued understanding of the rail track infrastructure. Track designs should be as cost-effective as possible and should be sensitive to the costs associated with the planning, development and maintenance of the track structure. Extensive and continuous research is therefore required to determine the influencing parameters and to maximise the track performance and the lifetime of the track structure. Deformation of the track structure is a good measure of the structural capability of a track structure or of the expected track performance. This deformation is vastly dependent on the support of the track structure. The ballast support and the foundation of the track structure are therefore key components. Poor support will lead to large deformations, which in turn will accelerate track deterioration. This will increase the maintenance need and therefore the total cost of operating the asset within an acceptable functional condition.http://www.civils.org.za/am201

Consideration of the elastic strain recovery rates of the formation layers of a railway track

Maintenance makes up a significant portion of the total life cycle costs of a railway track. The condition of the formation layers of a railway track dictates these maintenance costs to a large extent. The purpose of this study (a final-year BEng research project) was to aid the progression towards more cost-effective railway infrastructure by understanding the strain recovery process of the formation layers.http://www.civils.org.zaam201

The effects of fastening strength on the variation in stress-free temperature in continuous welded rail

Continuous welded rail (CWR) is a fundamental component of any modern track structure and has several advantages over former types of rail joining processes. The reduction in maintenance and related costs has become the most attractive property of CWR although careful monitoring and maintenance of CWR is essential to ensure safe train operations. Management of the stress-free temperature (SFT) of any section of CWR in order to prevent rail breaks and lateral buckling that could lead to derailments is a vital duty of the track maintenance team. Variations in the SFT are influenced by a number of external factors. This paper describes experimental field and laboratory tests carried out to investigate to what extent the fastening strength influences the variation in SFT in CWR track on Fist fastenings and two types of pads. The research established a nonlinear relationship between clamping force and rail movement through the fasteners as well as a strongly linear relationship between clamping force and the variation in SFT. It is also demonstrated that although the friction coefficient of the pad has an influence on rail movement through the fastener, the primary factor influencing SFT variations is the clip force. This paper concludes by quantifying the relationship between clamping force and the expected variation in SFT with clear guidelines on the management of the SFT in CWR.http://pif.sagepub.comhb2016Civil Engineerin

Stochastic modelling for the maintenance of life cycle cost of rails using Monte Carlo simulation

The need for decision support systems to guide maintenance and renewal decisions for infrastructure is growing due to tighter budget requirements and the concurrent need to satisfy reliability, availability and safety requirements. The rail of the railway track is one of the most important components of the entire track structure and can significantly influence maintenance costs throughout the life cycle of the track. Estimation of life cycle cost is a popular decision support system. A calculated life cycle cost has inherent uncertainty associated with the reliability of the input data used in such a model. A stochastic life cycle cost model was developed for the rail of the railway track incorporating imperfect inspections. The model was implemented using Monte Carlo simulation in order to allow quantification of the associated uncertainty within the life cycle cost calculated. For a given set of conditions, an optimal renewal tonnage exists at which the rail should be renewed in order to minimise the mean life cycle cost. The optimal renewal tonnage and minimum attainable mean life cycle cost are dependent on the length of inspection interval, weld type used for maintenance as well as the cost of maintenance and inspection activities. It was found that the distribution of life cycle cost for a fixed renewal tonnage followed a log-normal probability distribution. The standard deviation of this distribution can be used as a metric to quantify uncertainty. Uncertainty increases with an increase in the length of inspection interval for a fixed rail renewal tonnage. With all other conditions fixed, it was found that the uncertainty in life cycle cost increases with an increase in the rail renewal tonnage. The relative contribution of uncertainty of the planned and unplanned maintenance costs towards the uncertainty in total life cycle cost was found to be dependent on the length of inspection interval.Transnet Freight Rail and the Railway Safety Regulator.http://journals.sagepub.com/home/pifhj2018Civil Engineerin

Measurement of probabilistic ballast particle dynamics using Kli-Pi

At first glance the operational performance of ballast appears trivial in its simplicity. However, various mechanisms affect the performance of the ballast both on a macroscopic scale and discrete (mesoscale) particle level. The importance of experimental studies to establish the influence of the granular fabric has been highlighted repeatedly by other researchers. This paper describes a method by which quantitative metrics and statistics can describe the probabilistic response of railway ballast. The measurements were obtained with the installation of a set of customised wireless inertial measurement unit (IMU), referred to as Kli-Pi, in the granular layers of a heavy-haul railway line located in South Africa. The results indicate a complex interaction of displacement and rotation, in all three spatial dimensions. The high-frequency measurements provided approximations of the particle’s kinetic and potential energy (mechanical work) in addition to the indirect quantification of changes to the granular fabric. Finally, the descriptive statistics of the mechanical work provided an indirect measure of the confinement and coordination number of the particle, together with supporting evidence of the underlying probabilistic, instead of the expected deterministic response. These results strongly agree with the findings of existing literature that has, to date, been confined to theoretical study.http://www.journals.co.za/ej/ejour_civileng.htmlam2022Civil Engineerin

A new test track at the University of Pretoria

The Department of Civil Engineering at the University of Pretoria recently constructed a 30 m long railway test section on the University's Experimental Farm (better known as the "Proefplaas") in Pretoria. The track will further enhance the university's research capabilities in the railway environment. The project was made possible with the help of civil engineering students and sponsorship from industry. It was constructed as part of the Workshop Practice module presented to the first year students during the December/January 2012/2013 break. All the first year, and a few third and final year, civil engineering students assisted with the track construction which took approximately one month to complete.http://www.civils.org.za/am201

An inside look at the stresses due to lateral forces in Tubular Modular Track

The Tubular Modular Track system is a relatively new innovation in railway technology. This ballastless track structure provides a more stable and reliable track structure, and requires less track maintenance. These improvements in railway track structures are important, as there is a demand for higher capacity, faster, safer and more economical public transport systems. This research project focused on the strains and stresses experienced by the gauge bar, in three different sections along a track structure, namely a transitional curve, a circular curve and a tangent section of track.http://www.civils.org.za