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Kaewunruen S.,RailCorp Track Engineering | Kaewunruen S.,Massachusetts Institute of Technology
Case Studies in Nondestructive Testing and Evaluation | Year: 2014

'Big data' obtained from wayside detection systems and sensors installed on board a train show that actual loading history for a railway track is rather dynamic and transient. The dynamic loadings due to train and track interactions redistribute from the rails to the rail pad, from the rail pad to the railway sleeper, and from the railway sleeper to the underlying ground. Dynamic content redistributed onto each layer of track is also filtered by energy dissipation characteristic of materials and structures. As a critical infrastructure, railway turnout is a structural grillage system used to divert a train to other directions or other tracks. The wheel-rail contact over the crossing transfer zone often causes detrimental impact loads that rapidly deteriorate the turnout and its components. The dynamic responses of wheel-rail interaction depend largely on the non-smooth trajectory or wearing condition of crossing geometry. In reality, a railway line spreads over a large distance and monitoring such rail infrastructure is one of the challenges in rail industry. This paper presents a methodology and application to evaluate and monitor the structural deterioration of railway turnout systems in an Australian urban rail network. The method has integrated numerical train/track simulations, axle box acceleration and ride quality data obtained from the calibrated track inspection vehicle "AK Car". © 2014 Elsevier Ltd.

Kaewunruen S.,RailCorp Track Engineering | Remennikov A.M.,University of Wollongong
Engineering Failure Analysis | Year: 2011

On railway track structures, dynamic impact loads with very high magnitude but short duration are often caused by wheel or rail abnormalities such as flat wheels and dipped rails. The possibility of the large impact loading to cause an extreme failure to an in situ concrete sleeper could be very low about once or twice in the design life cycle. However, to the current knowledge, the behaviour of the in situ prestressed concrete sleepers under the ultimate impact loading has not yet been comprehended, resulting in the design deficiency. A high-capacity drop-weight impact testing machine was thus constructed at the University of Wollongong, in order to evaluate impulsive resistance of in situ prestressed concrete sleepers under impact loads. This paper describes the detail of the high-capacity impact testing machine, as well as the instrumentation, the calibration, and the analysis of failure mode, crack propagation, flexural toughness, and energy absorption mechanisms with respect to railway prestressed concrete sleepers. The impact tests were carried out using the prestressed concrete sleepers manufactured in Australia. An in situ track test bed was simulated in laboratory and calibrated against the frequency response functions obtained from the experimental modal analysis. The experiments using the high-capacity impact testing machine to investigate the impact energy transfer mechanism of the prestressed concrete sleepers are highlighted. © 2011.

Kaewunruen S.,RailCorp Track Engineering | Remennikov A.M.,University of Wollongong | Murray M.H.,Queensland University of Technology
Journal of Transportation Engineering | Year: 2011

New knowledge has raised a concern about the cost-ineffective design methods and the true performance of railroad prestressed concrete ties. Because of previous knowledge deficiencies, railway civil and track engineers have been aware of the conservative design methods for structural components in any railway track that rely on allowable stresses and material strength reductions. In particular, railway sleeper (or railroad tie) is an important component of railway tracks and is commonly made of prestressed concrete. The existing code for designing such components makes use of the permissible stress design concept, whereas the fiber stresses over cross sections at initial and final stages are limited by some empirical values. It is believed that the concrete ties complying with the permissible stress concept possess unduly untapped fracture toughness, based on a number of proven experiments and field data. Collaborative research run by the Australian Cooperative Research Centre for Railway Engineering and Technologies (Rail CRC) was initiated to ascertain the reserved capacity of Australian railway prestressed concrete ties that were designed using the existing design code. The findings have led to the development of a new limit-states design concept. This paper highlights the conventional and the new limit-states design philosophies and their implication to both the railway community and the public. © 2011 American Society of Civil Engineers.

Kaewunruen S.,RailCorp Track Engineering | Remennikov A.M.,University of Wollongong
Australian Journal of Structural Engineering | Year: 2011

The pre-stressed concrete sleepers (or railroad ties), which are installed in railway track systems as the crosstie beam support, are designed to carry and transfer the wheel loads from the rails to the ground. It is well known that railway tracks are subject to impact loading conditions, which are attributable to the train operations with either wheel or rail abnormalities such as f at wheels, dipped rails, etc. These loads are of very high magnitude but short duration. In addition, there exists the potential of repeated load experience during the design life of pre-stressed concrete sleepers. Pre-stressed concrete has played a significant role in maintaining the high endurance of sleepers subjected to low to moderate repeated impact loads. In spite of the common use of pre-stressed concrete sleepers in railway tracks, their impact response and behaviour under repetitions of severe impact loads are not deeply appreciated, nor taken into consideration in design. This experimental investigation was aimed at understanding the residual capacity of pre-stressed concrete sleepers in railway track structures under ultimate impact loading, in order to develop state of the art limit states design concepts for pre-stressed concrete sleepers. A high-capacity drop weight impact testing machine was constructed at the University of Wollongong to achieve this purpose. A series of severe impact tests on in-situ pre-stressed concrete sleepers was carried out, ranging from low to high impact magnitudes. The impact energy was evaluated in relation to the drop heights. The impact-damaged sleepers were re-tested under static conditions in order to evaluate the residual fracture toughness in accordance with the Australian Standard. It was found that a concrete sleeper damaged by an impact load could possess significant reserve capacity sufficient for resisting about 1.05 to 1.10 times the design axle loads. The impact behaviour and residual fracture toughness under different magnitudes of impacts are highlighted in this paper. The effects of track environment, including soft and hard tracks, are also presented together with a discussion related to the ultimate limit states design. © Institution of Engineers Australia, 2011.

Kaewunruen S.,RailCorp Track Engineering | Remennikov A.M.,University of Wollongong | Aikawa A.,Railway Technical Research Institute | Sakai H.,Railway Technical Research Institute
Acoustics Australia | Year: 2014

Statistically, the actual loading conditions for railway tracks are rather dynamic and transient. The dynamic loadings due to train and track interactions redistribute from the rails to the rail pad, from the rail pad to the railway sleeper, and from the railway sleeper to the underlying ground. Commonly, railway sleeper in track systems is modeled as a beam on elastic foundation. This study makes use of a calibrated finite element model of railway sleepers in a track system, in order to investigate the resonant frequencies and associated mode shapes of railway components in interspersed track systems. The numerical model takes into account the tensionless characteristic of the elastic support as well as the more realistic partial support condition. Using a finite element package STRAND7, the dynamic finite element model of the railway concrete sleeper was precisely established. The dynamic model has then been extended to demonstrate free vibration behaviours of the railway tracks. The effect of interspersed patterns (1 in 2; 1 in 3; and 1 in 4) on railway track dynamics has been firstly investigated and presented herein.

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