Development of FWD based hybrid back-analysis technique for railway track condition assessment

Track substructure is a key component of the railway transportation system. Similar to the built environment of other surface transportation systems, track substructures are subjected to aging and deterioration. This, frequently leads to the failure and collapse of the transportation systems, resulting in the imposition of costly repairs and maintenance. At the same time, the emergence of high-speed trains and heavier axle loads, together with a need for sustainable designs, has put additional pressure on asset owners. It has been shown that frequent condition assessments of railway substructures can considerably reduce the overall annual maintenance costs. Furthermore, limited knowledge of the substructure condition leads to the employment of inefficient, time-consuming, and expensive maintenance actions. Therefore, development of time- and cost-efficient techniques to frequently monitor existing railway track substructures is vital. The falling weight deflectometer (FWD) is recognised as an effective non-destructive test used to survey ballasted railway substructures through a back-analysis process. This paper presents a novel hybrid back-analysis technique that includes an artificial neural network (ANN) and genetic algorithm (GA) to estimate the substructure layer moduli of railway tracks using FWD testing data. To this aim, firstly a dynamic finite element (FE) model was developed and validated against experimental data from the literature. This FE model then were employed to generate a reliable dataset to train the ANN. In the next step, GA was employed as an optimisation tool within the back-analysis technique/framework to optimise the layer moduli (the ANN's input). A comparison study was performed to evaluate the performance of the developed technique. The results of this comparison revealed excellent performance and robustness of the developed technique

Neural network modeling of SBS modified bitumen produced with different methods

Various types of polymers are added to bitumen in order to improve its properties under low and high temperatures. It is important to determine accurately the complex modulus of polymer-modified bitumen samples (PMBs) in order to make a suitable mix design. Moreover the determination of the complex modulus is important in order to evaluate the efficiency of the additives. However the manufacture processes of PMBs involve many factors. This study aims to model the complex modulus of styrene–butadiene–styrene (SBS) modified bitumen samples that were produced by different methods using artificial neural networks (ANNs). PMB samples were produced by mixing a 160/220 penetration grade base bitumen with 4% SBS Kraton D1101 copolymer at 18 different combinations of three mixing temperatures, three mixing times and two mixing rates. The complex modulus of PMBs was determined at five different test temperatures and at ten different frequencies. Therefore a total of 900 combinations were evaluated. Various different results were obtained for the same PMB produced at different conditions. In the ANN model, the mixing temperature, rate and time as well as the test temperature and frequency were the parameters for the input layer whereas the complex modulus was the parameter for the output layer. The most suitable algorithm and the number of neurons in the hidden layer were determined as Levenberg–Marguardt with 3 neurons. It was concluded that, ANNs could be used as an accurate method for the prediction of the complex modulus of PMBs, which were produced using different methods

Manyetik Aktif Karbon Modifiyeli Bitümün Kompleks Modül Değerlerinin Yapay Sinir Ağlarıyla Tahmini

Bu çalışmada Manyetik Aktif Karbon (MAK) ile modifiye edilmiş bitümlü bağlayıcının reolojik özellikleri araştırılmış ve sonuçlar yapar sinir ağları ile tahmin edilmiştir. Çalışma kapsamında B160/220 penetrasyon sınıfı bitümlü bağlayıcıya %5, %10 ve %15 oranlarında MAK ilave edilerek modifiye bitümler elde edilmiş, ardından bitümler üzerinde Dinamik Kayma Reometresi (DSR) cihazı ile on farklı frekansta (0.01-10Hz) ve dört farklı sıcaklıkta (40°,50°,60°,70°C) frekans taraması testi gerçekleştirilmiştir. Sonuçlar, MAK ilavesinin kompleks modül değerlerini artırıp, faz açısı değerlerini azaltarak bitümlü bağlayıcının elastik özelliklerini geliştirdiğini göstermiştir. Daha sonra frekans, katkı oranı ve sıcaklık değerlerine bağlı olarak değişen kompleks modül ve faz açısı değerleri yapay sinir ağları yöntemi ile tahmin edilmiştir. Sonuçlar, kompleks modül ve faz açısı değerlerinin oldukça yüksek doğrulukta düşük hata ile elde edilebileceğini göstermiştir

Optimización del diseño estructural de pavimentos asfálticos para calles y carreteras

gráficos, tablasThe construction of asphalt pavements in streets and highways is an activity that requires optimizing the consumption of significant economic and natural resources. Pavement design optimization meets contradictory objectives according to the availability of resources and users’ needs. This dissertation explores the application of metaheuristics to optimize the design of asphalt pavements using an incremental design based on the prediction of damage and vehicle operating costs (VOC). The costs are proportional to energy and resource consumption and polluting emissions. The evolution of asphalt pavement design and metaheuristic optimization techniques on this topic were reviewed. Four computer programs were developed: (1) UNLEA, a program for the structural analysis of multilayer systems. (2) PSO-UNLEA, a program that uses particle swarm optimization metaheuristic (PSO) for the backcalculation of pavement moduli. (3) UNPAVE, an incremental pavement design program based on the equations of the North American MEPDG and includes the computation of vehicle operating costs based on IRI. (4) PSO-PAVE, a PSO program to search for thicknesses that optimize the design considering construction and vehicle operating costs. The case studies show that the backcalculation and structural design of pavements can be optimized by PSO considering restrictions in the thickness and the selection of materials. Future developments should reduce the computational cost and calibrate the pavement performance and VOC models. (Texto tomado de la fuente)La construcción de pavimentos asfálticos en calles y carreteras es una actividad que requiere la optimización del consumo de cuantiosos recursos económicos y naturales. La optimización del diseño de pavimentos atiende objetivos contradictorios de acuerdo con la disponibilidad de recursos y las necesidades de los usuarios. Este trabajo explora el empleo de metaheurísticas para optimizar el diseño de pavimentos asfálticos empleando el diseño incremental basado en la predicción del deterioro y los costos de operación vehicular (COV). Los costos son proporcionales al consumo energético y de recursos y las emisiones contaminantes. Se revisó la evolución del diseño de pavimentos asfálticos y el desarrollo de técnicas metaheurísticas de optimización en este tema. Se desarrollaron cuatro programas de computador: (1) UNLEA, programa para el análisis estructural de sistemas multicapa. (2) PSO-UNLEA, programa que emplea la metaheurística de optimización con enjambre de partículas (PSO) para el cálculo inverso de módulos de pavimentos. (3) UNPAVE, programa de diseño incremental de pavimentos basado en las ecuaciones de la MEPDG norteamericana, y el cálculo de costos de construcción y operación vehicular basados en el IRI. (4) PSO-PAVE, programa que emplea la PSO en la búsqueda de espesores que permitan optimizar el diseño considerando los costos de construcción y de operación vehicular. Los estudios de caso muestran que el cálculo inverso y el diseño estructural de pavimentos pueden optimizarse mediante PSO considerando restricciones en los espesores y la selección de materiales. Los desarrollos futuros deben enfocarse en reducir el costo computacional y calibrar los modelos de deterioro y COV.DoctoradoDoctor en Ingeniería - Ingeniería AutomáticaDiseño incremental de pavimentosEléctrica, Electrónica, Automatización Y Telecomunicacione

Development and Validation of Characterization Method Using Finite Element Numerical Modeling and Advance Laboratory Methods for Western Australia Asphalt Mixes

A quantitative understanding of materials characterization of asphalt mixtures is required to determine the appropriate asphalt mixtures so that pavement distress and deformation can be reduced. Various numerical modeling and laboratory tools are used to assess the asphalt mixtures of flexible pavement and provided a significant and novel contribution to understanding of characterization of asphalt mixtures and design of flexible pavement. The contribution to understanding from this thesis shall be integrated in future body of knowledge

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 1 comprises the first part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

Eleventh International Conference on the Bearing Capacity of Roads, Railways and Airfields

Innovations in Road, Railway and Airfield Bearing Capacity – Volume 2 comprises the second part of contributions to the 11th International Conference on Bearing Capacity of Roads, Railways and Airfields (2022). In anticipation of the event, it unveils state-of-the-art information and research on the latest policies, traffic loading measurements, in-situ measurements and condition surveys, functional testing, deflection measurement evaluation, structural performance prediction for pavements and tracks, new construction and rehabilitation design systems, frost affected areas, drainage and environmental effects, reinforcement, traditional and recycled materials, full scale testing and on case histories of road, railways and airfields. This edited work is intended for a global audience of road, railway and airfield engineers, researchers and consultants, as well as building and maintenance companies looking to further upgrade their practices in the field

Sustainable pavement applications utilizing quarry by-products and recycled/nontraditional aggregate materials

Quarry By-products (QB), usually less than 0.25 in. (6 mm) in size, are the residual deposits from the production of required grades of aggregates and are often stockpiled in excess quantities at the quarries. More than 175 million US tons of QB are produced every year from the 3,000 operating quarries around the US. QB pose environmental and economic challenges as they accumulate in large quantities in landfills or interfere with quarry operations. With recent focus on sustainable construction practices and the scarcity of natural resources, more common and sustainable uses of by-product materials such as QB are becoming imperative. This dissertation focuses on the introduction and evaluation of new sustainable applications of QB and/or QB mixed with other marginal, virgin or recycled aggregate materials in pavements. The selected QB applications were evaluated through the construction of full-scale pavement test sections utilizing QB in targeted sustainable applications, and testing them with heavy wheel loads through Accelerated Pavement Testing (APT). The QB applications studied included both unbound and bound (chemically stabilized) pavement subsurface/foundation layers. The studied QB pavement applications were in five categories: (1) Using QB for filling voids between large stones as aggregate subgrade on soft subgrades; (2) increased fines content (e.g. 15% QB fines passing No. 200 sieve) in dense-graded aggregate subbase over soft subgrade soils; (3) using QB as a cement or fly ash-treated subbase (e.g., in inverted pavements); (4) using QB as a cement-treated base material; and (5) for base course applications, blending QB with coarse aggregate fractions of recycled materials and stabilizing the blends with 3% cement or 10% class C fly ash. In preparation for the field evaluations, several laboratory studies were conducted to finalize the designs of intended QB applications. The main laboratory studies were: (1) A packing study of QB with recycled coarse aggregates to determine the optimum blending ratio; (2) a packing study to aid the construction of large aggregate subgrade with QB materials filling the inherent voids; and, (3) Unconfined Compressive Strength (UCS) tests for chemically stabilized QB samples. Fifteen full-scale pavement test sections utilizing QB applications and one conventional flexible section were constructed in three ‘Test Cells.’ Cell 1 had four paved and four unpaved test sections to study construction platforms and low volume road applications of QB. Cells 2 and 3 studied chemically stabilized QB applications for base and subbase layers. Construction activities included engineering the top 305 mm (12 in.) of existing subgrade to a California Bearing Ratio (CBR) = 1% for Cell 1 test sections and to a CBR = 6% for all the pavement test sections in Cells 2 and 3. Subgrade modification was achieved through moisture adjustment and compaction. The construction of the QB layers were successfully achieved and extensively monitored. The data for nuclear density measurements and moisture contents indicated that nearly all the test sections were constructed at or near the targeted optimum moisture contents and achieved proper densities. A Lightweight Deflectometer (LWD) was used to assess the stiffness of the constructed layers after the construction of each lift. It was also used to monitor the increase in stiffness of the chemically stabilized layers. The increase in stiffness of the chemically stabilized layers was the highest for cement-stabilized test sections and usually lower for fly ash-stabilized sections. Following the paving of test sections with Hot Mix Asphalt (HMA), Falling Weight Deflectometer (FWD) tests were conducted on all finished surfaces. Significantly low deflection values were measured for the sections with cement-stabilized QB and QB blends with recycled aggregates. APT was conducted using the Advanced Transportation Loading Assembly (ATLAS). A constant unidirectional wheel load of 10 kips (44.5 kN), a tire pressure of 110 psi (760 kPa), and a constant speed of 5 mph (8 km/h) were assigned. The exceptionally good performance of some of the stabilized QB applications in Cells 2 and 3 necessitated trafficking in excess of 100,000 passes; an increased wheel load/tire pressure combination of 14 kip (62.3 kN)/ 125 psi (862 kPa) was adopted for the additional 35,000 passes. Four of the test sections in Cells 2 and 3 were instrumented with soil pressure cells on top of the engineered CBR = 6% subgrade. Data collected from these pressure cells showed that significantly low vertical pressures were transmitted to the subgrade for sections with stabilized bases/subbases. Measurements for rutting progression for the construction platform and HMA-paved test sections in Cell 1 showed good performance for the sections constructed with 15% nonplastic fines and with blends of large aggregate subgrade rocks with QB. Measurements of rutting progression in Cells 2 and 3 indicated exceptionally good performance of sections with blends of QB and recycled coarse aggregates stabilized with cement. Generally, sections stabilized with cement accumulated lower rutting than those stabilized with fly ash. No significant differences in rutting performance were detected for sections with QB from two different aggregate sources. For the inverted section with a cement-stabilized QB subbase, measured rut amounts were significantly lower than those in the test section with the fly ash-stabilized QB subbase. None of the stabilized sections showed any signs of cracks. Additional testing and forensic analyses were conducted after the APT study to better assess the performance of the constructed sections. These tests included: (1) FWD testing before and after APT; (2) HMA coring; (3) Dynamic Cone Penetrometer (DCP) testing for the aggregate subbase/base layers; (4) flooded tests for the aggregate subgrade/QB test sections; and (5) trenching to assess uniformity of construction and determine as-constructed layer thicknesses. Results from these forensic tests further supported the conclusions from the APT study indicating the overall quite satisfactory performance for the studied sustainable QB applications. Mechanistic analysis was conducted using GT-PAVE axisymmetric finite-element program to analyze the FWD results, and to calculate response benefits based on resilient FWD deflection for various design thicknesses and material properties. Life Cycle Assessment (LCA) and Life Cycle Cost Analysis (LCCA) studies were conducted to assess the environmental impacts and cost benefits for the studied QB applications. LCA and LCCA results for three scenarios, i.e. as-constructed and as-designed pavement thicknesses studied though APT and newly proposed pavement sections for low volume pavement alternatives, indicated that chemically stabilized QB and QB blended with recycled coarse aggregates could be successfully used to construct sustainable, resilient, and low cost pavements. Particularly, pavement structures with a low 3% cement-stabilized QB applications created high stiffness base/subbase layers in this study; they exhibited significant response benefits due to low FWD measured and predicted surface deflections and can withstand higher traffic volumes over pavement life

Advanced Testing and Characterization of Bituminous Materials, Two Volume Set

Bituminous materials are used to build durable roads that sustain diverse environmental conditions. However, due to their complexity and a global shortage of these materials, their design and technical development present several challenges. Advanced Testing and Characterisation of Bituminous Materials focuses on fundamental and performance testin