Simulation of the mechanical behavior of railway ballast by intelligent computing

Ballast is one of the main components of railway track foundations, thus, an accurate prediction of its mechanical behavior is crucial for stability of railway tracks. In this paper, one of the most commonly used intelligent computing techniques, i.e. Artificial Neural Networks (ANNs), is utilized to model the mechanical behavior of ballast under static loading conditions. Experimental results from a series of large-scale consolidated drained triaxial compression tests collected from the literature are used for ANN model calibration and validation. The results indicate that predictions from the ANN model compare well with those obtained from the large-scale experiments. In particular, ANN predictions demonstrate a high degree of accuracy in simulating the stress-strain and volume change characteristics of ballast. The plastic dilation and contraction of ballast at various confining pressures, and the strain-hardening and post-peak strain-softening are also well simulated

Intelligent computing for modeling axial capacity of pile foundations

In the last few decades, numerous methods have been developed for predicting the axial capacity of pile foundations. Among the available methods, the cone penetration test (CPT)-based models have been shown to give better predictions in many situations. This can be attributed to the fact that CPT-based methods have been developed in accordance with the CPT results, which have been found to yield more reliable soil properties; hence, more accurate axial pile capacity predictions. In this paper, one of the most commonly used artificial intelligence techniques, i.e., artificial neural networks (ANNs), is utilized in an attempt to develop artificial neural network (ANN) models that provide more accurate axial capacity predictions for driven piles and drilled shafts. The ANN models are developed using data collected from the literature and comprise 80 driven pile and 94 drilled-shaft load tests, as well as CPT results. The predictions from the ANN models are compared with those obtained from the most commonly used available CPT-based methods, and statistical analyses are carried out to rank and evaluate the performance of the ANN models and CPT methods. To facilitate the use of the developed ANN models, they are translated into simple design equations suitable for hand calculations

A review of artificial intelligence applications in shallow foundations

Geotechnical engineering deals with materials (e.g. soil and rock) that, by their very nature, exhibit varied and uncertain behavior because of the imprecise physical processes associated with the formation of these materials. Modeling the behavior of such materials in geotechnical engineering applications is complex and sometimes beyond the ability of most traditional forms of physically based engineering methods. Artificial intelligence (AI) is becoming more popular and particularly amenable to modeling the complex behavior of most geotechnical engineering applications, including foundations, because it has demonstrated superior predictive ability compared to traditional methods. The main aim of this paper is to review the AI applications in shallow foundations and present the salient features associated with the AI modeling development. The paper also discusses the strengths and limitations of AI techniques compared to other modeling approaches

Shear Behaviour of Misurata Wet Sand

The foundation design of buildings depends on the bearing capacity of soil and foundation shaft resistance, upon this reason, for buildings safety, the study of shear behaviour of soil is very important to analyse and evaluate the foundation settlement and friction between soil and foundation surface. especially in the case of deep foundation. The paper is to study and evaluate the shear behaviour of Misurata wet sand around foundation surface under the effect of different axial loads by using direct shear box test. This study contains nine laboratory tests were done to measure the Sand-Aluminum interface of smooth surfaces, and other nine tests for Sand-Aluminum interface of rough surfaces, to simulate foundation surface in the site. Also, another nine tests were done to measure Sand-Sand interface shear behaviour resulting from friction between wet sand grains under different normal loads, soil type and initial sand density in three cases of soil, loose, medium  and dense wet sand. The test results showed that the value of soil displacement and interface friction angle (d) are very important for foundation design, especially for deep foundations. Also, from the evaluation of experimental test results we found that the interface friction angle (d) depends on roughness of the foundation, initial compactness, water content and porosity of sand

Incidence and prevalence of pressure ulcers in intensive care patients

Dissertation AnlagenZusammenfassung Dekubitalgeschwüre stellen eine potentielle Komplikation für Intensivpflegepatienten dar und ihre Prävention ist somit ein wichtiges Thema der Pflege. Daher ist das Ziel dieser Studie, Erkenntnisse über die Prävalenz und Inzidenz von Dekubitus auf Intensivstationen zu gewinnen. Die Studie gliedert sich in drei Teile: Der erste Teil ist ein Literaturreview. Hier wurden Studien innerhalb einer Zeitspanne von 2000 bis 2005 auf ihre Ergebnisse hinsichtlich der Prävalenz und Inzidenz von Dekubitus sowie damit zusammenhängender Faktoren unter-sucht. Außerdem wurde die methodische Qualität der Studien überprüft. Die Ergebnisse zeigten Variationen in der Prävalenz von Dekubitus auf Intensivstationen zwischen 4% bis 38% und in der Inzidenz zwischen 3,8% bis 12,3%. Alter, Inkontinenz, medizinische Diagnosen und Immobilität wiesen signifikante Zusammenhänge mit der Entwicklung eines Dekubitus auf. Mehrere Faktoren beeinträchtigten die methodische Genauigkeit der untersuchten Studien. In einem zweiten Schritt wurde eine Literaturstudie vorgenommen, um die prognostische Validität von Instrumenten zur Einschätzung des Dekubitusrisikos bei Intensivpflegepatienten zu untersuchen. Die Ergebnisse zeigten, dass nur ein Instrument, die Cubbin und Jackson-Skala , speziell für die Einschätzung des Dekubitusrisikos von Intensivpflegepatienten entwickelt wurde. Sensitivitäts- und Spezifitätstests zeigten sich als unzureichend, um die prognostische Validität von Risikoeinschätzungsinstrumenten zu demonstrieren. Den dritten Teil bildet die von der Abteilung Pflegewissenschaft, Charité Universitätsmedizin Berlin durchgeführte Prävalenzerhebung. Ihre Ziele waren die Ein-schätzung der Prävalenz von Dekubitus bei Intensivpflegepatienten und der damit verbun-denen Faktoren sowie die Ermittlung der Körperregionen, die am häufigsten betroffen sind. Die Querschnittsstudie wurde an 1760 Patienten von chirurgischen (N=402), internistischen (N=629) und interdisziplinären (N=729) Intensivstationen durchgeführt. Die Ergebnisse zeigten eine mittlere Prävalenzrate von ±30% zwischen 2002 bis 2005, während die Prävalenz in 2006 16,2% betrug.Abstract Pressure ulcers are a potential complication for intensive care patients and their prevention is a major issue in nursing care. Therefore, this study aims to give an insight into pressure ulcer prevalence and incidence in intensive care settings. This study consists of three parts: The first part is a literature review and aims to assess pressure ulcer prevalence and incidence in intensive care patients in the period from 2000 to 2005, the related factors, and the methodological rigour of these studies. The results revealed variations in the prevalence rate ranging from 4% to 38%, while the incidence rate ranged from 3.8% to 12.3% in intensive care settings. Age, incontinence, medical diagnoses and immobility were also significantly related to pressure ulcer development. In addition, more than one factor threatens the methodological rigour of the assessed studies. The second part reviews literature and aims to assess the predictive validity of pressure ulcer risk assessment tools in intensive care patients. The results revealed that only one pressure ulcer risk assessment scale was developed specially for intensive care patients called Cubbin and Jackson s scale . Sensitivity and specificity tests were not suitable for establishing the predictive validity of the risk assessment scales. The third part is a prevalence study conducted by the Department of Nursing Science, Charité-Universitätsmedizin Berlin in Germany. It aims to assess pressure ulcer prevalence in intensive care patients, the factors related to pressure ulcer prevalence in intensive care patients and the most common body sites of pressure ulcers. The results obtained from this study are based on a cross-sectional design carried out on 1760 patients from surgical (402), medical (629), and interdisciplinary intensive care (729). They revealed that the mean prevalence rate was ± 30% from 2002 to 2005 while it was 16.2% in 2006

Three-dimensional numerical modelling of ballasted railway track foundations for high-speed trains with special reference to critical speed

Due to recent congestion of highways in many countries around the world, railways have become the most popular means of public transportation, which has increased the demand for heavier and faster trains. High speeds and heavy loads of trains are usually accompanied with large vibrations in the train-track-ground system, especially when train speed reaches its critical value, leading to possible train derailment and track damages. This unwanted scenario makes it important for railway geotechnical engineers to investigate the behaviour of ballasted railway track foundations for high-speed trains, with special reference to critical speed. In the current paper, a sophisticated three-dimensional (3D) finite element (FE) modelling was developed to simulate the dynamic response of ballasted railway tracks subjected to train moving loads, and the critical speed was investigated for various train-track-ground system conditions. The results were presented in terms of the evolution of the coefficient of dynamic amplification of sleeper deflection versus train speed, which have been synthesized into simple sensitivity charts that can be used to determine the critical speed corresponding to the conditions of a particular train-track-ground system

A new model based on evolutionary computing for predicting ultimate pure bending of steel circular tubes

In this study, the feasibility of using evolutionary computing for modelling ultimate pure bending of steel circular tubes was investigated. The behaviour of steel circular tubes under pure bending is complex and highly non-linear, and the literature has a number of solutions, most of which are difficult to use in routine design practice as they do not provide a closed-form solution. This work presents a new approach, based on evolutionary polynomial regression (EPR), for developing a simple and easy-to-use formula for prediction of ultimate pure bending of steel circular tubes. The EPR model was calibrated and verified using a large database that was obtained from the literature and comprises a series of 104 pure bending tests conducted on fabricated and cold-formed tubes. The predicted ultimate pure bending of steel circular tubes using this model can be obtained from a number of inputs including the tube thickness, tube diameter, steel yield strength and modulus of elasticity of steel. A sensitivity analysis was carried out on the developed EPR model to investigate the model generalisation ability (or robustness) and relative importance of model inputs to its output. Predictions from the EPR model were compared with those obtained from artificial neural network (ANN) models previously developed by the authors, as well as most available codes and standards.The results indicate that the EPR model is capable of predicting the ultimate pure bending of steel circular tubes with a high degree of accuracy and outperforms most available codes and standards. The results also indicate that the performance of the EPR model agrees well with that of the previously developed ANN models. It was also shown that the EPR model was able to learn the complex relationship between the ultimate pure bending and most influencing factors, and render this knowledge in the form of a simple and transparent function that can be readily used by practising engineers. The advantages of the proposed EPR technique over the ANN approach were also addressed

Use of slag (with cement) for improving the performance of expansive soil of road pavement subgrade

The study presented in this paper evaluates the suitability of using slag (with cement) as a stabilizer, for improving the performance of expansive subgrade soil in road pavement. Several laboratory tests were conducted to determine the geotechnical engineering characteristics of the expansive soil and associated mechanical engineering performance. The tests conducted include the particle size distribution, standard Proctor compaction, Atterberg’s limits, free swelling, permeability, California bearing ratio (CBR), unconfined compressive strength (UCS), and repeated load triaxial (RLT). In this study, the use of slag (with cement) as a stabilizer followed three proportion schemes, and the selection of a specific stabilizer proportion was determined based on UCS value that satisfies the required standard as a subgrade for road pavement. The results recommended a stabilizer proportion for the soil studied to be 13.5% slag + 1.5% cement at 28 days curing time. This mixture resulted in a remarkable increase in the UCS value of eight times higher than the UCS value of the non-stabilized soil. The CBR value of the mixture was four times higher than the minimum required value for design of road pavement. The study presented herein confirmed that the exploitation of the by-product material of slag can indeed be useful, both in terms of improving the performance of the subgrade soil for road pavement and sparing the environment a spread of significant potential pollutant

Use of digital imaging for gradation and breakage of railway ballast

The foundation of ballasted railway is usually consisted of a graded layer of granular media of ballast placed above naturally deposited subgrade. The ballast layer is responsible for limiting the vertical stress magnitudes applied to the weaker subgrade and also prevents the vertical and lateral train-induced sleeper movements. In recent years, the progressive use of faster and heavier trains has compromised the ability of ballast to resist such movements due to the increased magnitude of ballast breakage (degradation). Therefore, accurate determination of ballast breakage is important. The amount of ballast breakage can be estimated by comparing the gradation (particle size distribution) curves of fresh and degraded ballast, using a ballast breakage index. However, the Australian railway authorities currently rely on the visual inspection for estimating ballast breakage. Despite the fact that the visual inspection is convenient, as it does not require transport of ballast samples or testing, it is subjective and can lead to uneconomical maintenance cycles. In this paper, an attempt is made to utilise the digital imaging technique for gradation analysis and breakage estimation of ballast. The technique is fast and convenient, and can be applied to both the laboratory and field conditions, hence, can be used successfully to replace the visual inspection of ballast breakage