Railway track support condition assessment—Initial developments on a vehicle-based monitoring solution through modal analysis

Nowadays, there are multiple initiatives showing a renewed interest on railway transport of goods and passengers around the world. Thus, an efficient management of railway infrastructures, both at the operational level and in terms of economic profitability, is not only desirable but also corresponds to an area of ongoing research. In order to contribute to these efforts, an alternative and novel methodology to evaluate railway track support conditions is presented here, based on modal analysis of the characteristic frequencies of the multi-element system composed by a railway infrastructure and an instrumented vehicle moving over it. This methodology belongs to the group of vibration-based structural damage identification methods, and is focused on observing the characteristic frequencies of this multi-element system, which can be correlated with changes in the physical properties of the railway infrastructure under analysis. An important feature of the proposed methodology is that it should enable the collection of information regarding the conditions of the substructure of a railway infrastructure. By performing this assessment of a railway infrastructure over its length, and over time by comparing different rides over the same railway stretch, important information can be gathered regarding the support conditions of the track. This paper presents a complete description on the current stage of development of the proposed methodology, along with the theoretical model that serves as the basis to interpret the collected data. Preliminary verification of this methodology is performed through the analysis of two case studies regarding the passage of an instrumented vehicle over two underpasses. The results obtained so far show that the proposed methodology can provide relevant information regarding the support conditions of railway tracks.

Active Control of Stiffness of Tensegrity Plate-like Structures Built with Simplex Modules

The aim of this study is to prove that it is possible to control the static behavior of tensegrity plate-like structures. This possibility is very important, particularly in the case of deployable structures. Here, we analyze the impact the support conditions of the structure have on the existence of specific characteristics, such as self-stress states and infinitesimal mechanisms, and, consequently, on the active control. Plates built with Simplex modules are considered. Firstly, the presence of the specific characteristics is examined, and a classification is carried out. Next, the influence of the level of self-stress state on the behavior of structures is analyzed. A geometrically non-linear model, implemented in an original program, written in the Mathematica environment, is used. The results confirm the feasibility of the active control of stiffness of tensegrity plate-like structures characterized by the presence of infinitesimal mechanisms. In the case when mechanisms do not exist, structures are insensitive to the initial prestress level. It is possible to control the occurrence of mechanisms by changing the support conditions of the structure. Based on the obtained results, tensegrity is very promising structural concept, applicable in many areas, when conventional solutions are insufficient.

Mobile home fragility curves

Seismic fragility of mobile (manufactured) homes is investigated. Compiled is a catalog of home performance in past earthquakes. Intensity measures causing damage are characterized by peak ground acceleration and velocity. Damage is defined as when the home is knocked out of position necessitating repairs and re-installation. Four categories of support conditions are identified: unanchored, tie-downs, proprietary systems, and perimeter wall foundations. Suggested fragility curves for unanchored homes and homes with tie-downs are derived from computer simulations. As a benchmark, a fragility curve for proprietary and perimeter wall systems is taken as the same as that for conventional wood homes. Shortcomings of using tie-down and proprietary systems in high seismic zones are discussed. The suggested fragility curves account for the different categories of support conditions thereby representing advancement to those in the Hazus national standardized risk modeling methodology.

A Method to Calculate the Support Length of Beams Resting on Masonry Walls

Rehabilitation, strengthening, and retrofitting of existing masonry buildings represent an important challenge for the construction engineering field. Often, slab strengthening/retrofitting is performed by replacing existing timber and steel beams or by adding new beams to improve the slab load-carrying capacity. The computation of the stresses at the beam–masonry interface (i.e., the contact pressure) is crucial to properly design the beam support length, preventing local failure of masonry and beam. This paper presents a simple analytical procedure to compute the contact pressure at the beam–masonry interface. The analytical procedure is validated by comparison between analytical and corresponding numerical results obtained by finite element modeling. Different types of beam (solid and laminated timber beams and steel beams) were considered, as well as different support conditions (simply resting on the wall considering different support lengths or fully embedded). The results obtained show that the method proposed is simple and reliable, which makes it suitable for professional practice.

Stability of nanobeams and nanoplates with defects

The sensitivity of critical buckling load and critical stress concerning different geometrical and physical parameters of Euler-Bernoulli nanobeams with defects is studied. Eringen’s nonlocal theory of elasticity is used for the determination of critical buckling load for stepped nanobeams subjected to axial loads for different support conditions. An analytical approach to study the impact of discontinuities and boundary conditions on the critical buckling load and critical stress of nanobeams has been developed. Critical buckling loads of stepped nanobeams are defined under the condition that the nanoelements are weakened with stable crack-like defects. Simply supported, clamped and cantilever nanobeams with steps and cracks are investigated in this article. The presented results are compared with the other available results and are found to be in a close agreement.

Data-Driven Railway Crosstie Support Condition Prediction Using Deep Residual Neural Network: Algorithm and Application

Ballasted track substructure is designed and constructed to provide uniform crosstie support and serve the functions of drainage and load distribution over trackbed. Poor and nonuniform support conditions can cause excessive crosstie vibration which will negatively affect the crosstie flexural bending behavior. Furthermore, ballast–tie gaps and large contact forces at the crosstie–ballast interface will result in accelerated ballast layer degradation and settlement accumulation. Inspection of crosstie support condition is therefore necessary while very challenging to implement using current methods and technologies. Based on deep learning artificial intelligence techniques and a developed residual neural network (ResNet), this paper introduces an innovative data-driven prediction approach for crosstie support conditions as demonstrated from a full-scale ballasted track laboratory experiment. The discrete element method (DEM) is leveraged to provide training and testing data sets for the proposed prediction model. K-means clustering is applied to establish ballast layer subsections with representative ballast particles and provide additional insights on layer zoning for dynamic behavior trends. When provided with DEM simulated particle vertical accelerations, the proposed deep learning ResNet could achieve 100% training and 95.8% testing accuracy. Fed with vertical acceleration measurements captured by advanced “SmartRock” sensors from a full-scale ballasted track laboratory experiment, the trained model could successfully reach a high accuracy of 92.0%. Based on the developed deep learning approach and the research findings presented in this paper, the innovative crosstie support condition prediction system is envisioned to provide railroaders accurate, timely, and repeatable inspection and monitoring opportunities without disrupting railway network operations.

Variability of support conditions and effects on the non-linear flexural response of concrete sleepers

Current structural models used for the flexural design of prestressed concrete sleepers assume that ballast bearing support is static and located within a fixed region. This assumption implies a linear relationship between wheel load and bending moment. However, field data gathered from instrumented sleepers shows that this trend is non-linear, and the difference in flexural behavior between model predictions and field-measured demand is significant. Using back-calculation techniques and the development of a sleeper support analysis tool, this paper investigates the load-dependency of sleeper support condition. It is hypothesized that a given support condition redistributes ballast reaction forces due to the mechanical interaction of ballast particles with the sleeper’s deflected shape. It was found that redistribution of support conditions can reduce the expected flexural bending moment up to 45% when compared with moments calculated using traditional design guidelines. This effect (non-linearity) is greater as wheel loads increase. Results from revenue service field experimentation provided insight into the interaction between sleeper and ballast and serve as a foundation for the development of more complex analytical models. This will facilitate revisions to the future flexural design procedures for concrete sleepers, to ensure they are optimized for their expected service loading conditions.

Psychosocial support conditions in the orphanage: case study of Wolisso project

This study was conducted to assess the psychosocial and material services provision of Wolisso Kalehiwot Church project/center. Qualitative research design employing phenomenological approach was conducted as to reach on identifying the strengths and challenges practiced in the center. Purposive sampling techniques was used to draw ten respondents from the center (8 from orphans, 2 from staff) to respond to interview questions. The result of this study indicated that the effort made by the project is so effective in addressing the immediate need of the orphans including survival and wellbeing of these children. Consequently, the weakness in the project observed was initial recruitment problem of the orphans and unskilled staffs involving in the project and the inability to be proactive for the sustainability request for the project were seen as major. The challenges faced were identified as characteristics of the staff to handle the growing needs of the orphans, emotional instability of the children, limited access to social integration, negative attitude of the community towards institutionalization and segregation were observed as critical. Hence, institutional capacity building from both external and internal funders to maintain the projects sustainability with clear goal and policy direction is mandatory.

Working and Student Youth: Values of Everyday Life, Time Budget

The article analyzes the values of everyday life and the time budget of the younger generation (working youth) Pskov against the background of the older generation of workers, as well as students of the universities of Pskov, Omsk and Moscow. Empirical base: data from a study conducted in March 2019-January 2020. Life values are considered in three groups. The time budget is presented with information about the use of time in the average working day, in the average non-working day, and in the average week. It is shown that there are no intergenerational differences in the values of life support conditions (6) between the younger and older generations of workers, neither in men nor in women. Intergenerational differences in the values of daily activities between the younger and older generations of workers were found only in 6 of the 13 groups (mainly in men). Among students in the capital and in two regional centers of the Russian Federation, statistically significant differences were found in 9 out of 19 values (mainly among girls). As a result of a comparative analysis of the ratio of time spent on labor, restoring and developing groups of daily activities in three generations, it was found that the labor component is minimal among students. It is significantly higher among the working youth and even higher among the older generation of workers. This trend is typical for both men and women. The time spent on the restoring group, on the contrary, decreases from the student youth to the working youth and the older generation of workers. The share of time resources for developing activities in both generations of workers is the same for both men and women. This time resource is almost twice less than that of students.