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Inspection of RCF rail defects – Review of NDT methods
No full textRail inspection research is a substantive topic for the railway industry. Management of rolling contact fatigue rail defects is crucial for transport safety worldwide because uncontrolled development of these defects could cause railway accidents, including derailments. This paper presents the review of non-destructive inspection methods for surface and subsurface rolling contact fatigue defects, with particular emphasis on squat and head checking rail defects. Main types of standard and novel non-destructive inspection methods are presented and described from the aspect of basic characteristics, advantages and disadvantages for its practical application for rails in the track, and possible improvements of equipment and software. The presented review is based on the relevant international researches and review papers. In addition, a combination of inspection methods are presented, which can improve the reliability of defect detection
Assessment of water resources system resilience under hazardous events using system dynamic approach and artificial neural networks
Get PDFThe objective of this research is to propose a novel framework for assessing the consequences of hazardous events on a water resources system using dynamic resilience. Two types of hazardous events were considered: a severe flood event and an earthquake. Given that one or both hazards have occurred and considering the intensity of those events, the main characteristics of flood
dynamic resilience were evaluated. The framework utilizes an artificial neural network (ANN) to estimate dynamic resilience. The ANN was trained using a large, generated dataset that included a wide range of situations, from relatively mild hazards to severe ones. A case study was performed on the Pirot water system (Serbia). Dynamic resilience was derived from the developed system dynamics model alongside the hazardous models implemented. The most extreme hazard combination results in the robustness of 0.04, indicating a combination of an earthquake with a significant magnitude and a flood hydrograph with a low frequency of occurrence. In the case of moderate hazards, the system robustness has a median value of 0.2 and the rapidity median value of 162 h. The ANN’s efficacy was quantified using the average relative error metric which equals 2.14% and 1.77% for robustness and rapidity, respectively
Novel computational tool for coupling water and heat transport models – application on green roofs
Get PDFIntroduction: Green roofs are one of the most common multifunctional types of Nature Based Systems
(NBS) serving primarily for mitigation of the urban runoff (Stovin et al. 2012, Versini et al. 2020). Since
relying on the soil water interaction, green roofs also have a significant impact on reduction of the local
temperature, which has not been so deterministically investigated in the past. To simulate the change of
substrate temperature and water content accurately and continuously, it is necessary to couple models
for water and heat transport through (un)saturated porous media which has been done in many studies
(Campbell 1985, Bittelli et al. 2008). The core of these models are the partial differential equations that
are strongly nonlinear, especially Richards (1931) equation describing the unsaturated water flow, and
hence their numerical solving is still challenging from the perspective of the computational time, numerical
stability, and accuracy. Linearization of Richards equation has first been proposed by Ross (2003) who
developed a stable explicit numerical scheme for solving it by using Taylor series and Kirchhoff potential
to express unsaturated water fluxes, while similar approach has not been applied yet to Heat equation.
The main deficiency of this approach as far as Richards equation is concerned is the necessity to use finer
time discretization to avoid greater water balance errors, as well as the complex and often inaccurate
transition from the unsaturated to saturated state and vice versa.
To develop a robust and accurate numerical tool for consecutive solving of Richards and Heat equations,
several improvements compared to the existing approaches have been made. Firstly, Taylor series has also
been applied on soil heat fluxes creating rather simple and mathematically elegant explicit numerical
scheme for solving Heat equation. Secondly, unlike in Ross’s method where only the first term of Taylor
series is used, here are used the first and the second term to create more accurate approximation of water
fluxes. Also, unlike in Ross (2003), here Richards equation is solved strictly with respect to Kirchhoff
potential to smooth the transition between unsaturated and saturated water flow. Finally, the
evapotranspiration rate at the top surface is not predefined but determined from the latent heat flux
computed through the iterative solving of Richards and Heat equations. Here are presented preliminary
simulation results of the proposed coupled model obtained by using approximately six days long timeseries
of the measured meteorological data taken from Bittelli et al. (2008)
Headed studs in profiled steel sheeting: Overview and comments
Get PDFHeaded studs are the most commonly used mechanical shear connectors in composite steel-concrete beams. The behaviour of headed studs differs whether they are applied in solid concrete slabs or composite steel-concrete slabs with profiled steel sheeting. Although design codes provide calculation models for shear resistance of headed studs in profiled steel sheeting, certain weaknesses are attributed to design procedures given in EN 1994-1-1. Alternative design models have been proposed by several researchers. In this paper, novel models are presented and compared through the example of headed studs in different types of profiled steel sheeting.Moždanici sa glavom su najčešće primenjivana mehanička spojna sredstava u spregnutim gredama od čelika i betona. Ponašanje moždanika razlikuje se u zavisnosti od toga da li se primenjuju u punim betonskim pločama ili u spregnutim pločama na profilisanom limu. Iako su proračunski modeli za nosivost moždanika u profilisanom limu dati u standardima za projektovanje, važećim proračunskim procedurama datim u EN 1994-1-1 pripisuju se izvesni nedostaci. Iz tog razloga nekoliko istraživača je predložilo alternativne proračunske modele. U radu su prikazani predloženi modeli proračuna i data je uporedna analiza nosivosti moždanika sa glavom u različitim tipovima profilisanog lima.ASES International Congress, Aranđelovac, 28-30th September 202
3D Cadastral Data in The Process of Urban Planning
Get PDFCadastral data are very important in the process of urban planning. Moreover, cadastral data present a spatial base for urban planning decisions. Over the last few decades, research on 3D cadastres have been performed raising worldwide awareness of the need for 3D cadastral systems. This was driven by the development of new technologies for the acquisition, storage, maintenance, and visualization of 3D data as well as by complex situations in urban areas that cannot be unequivocally registered in 2D based cadastral systems. This paper examines the 3D cadastral data and emphasizes the differences between traditional cadastral data and 3D cadastral data. An overview of 3D cadastral systems was provided, the basic description of 3D cadastre data, and examples of the real situations that traditional cadastral systems cannot handle and unequivocally register. The paper further presents what would be clear benefits for urban planning once the 3D cadastre system is implemented. It is emphasized how important is 3D geometry and data on ownership for underground constructions and utility networks. Conclusions were provided and what needs to be fulfilled to effectively use 3D cadastral data in the process of urban planning
Advance design methods of steel structurs based on Eurocode 3
No full textEurocode introduces innovations in the design of steel structures that create new opportunities for
designers and contractors to construct more attractive and cost-effective structures. The paper present a new approach to designing steel structures based on advanced methods defined in Eurocode. These methods were not recognised by the old ex Yugoslav steel structures codes. Advanced numerical simulations are a powerful tool that helps engineers understand the deformation and stresses of the structure in detail. Possibilities of high-end design software in the application of GMNIA (Geometrically and Materially Nonlinear Analysis with Imperfections) in the design of complex elements of steel structures will be demonstrated. The authors will illustrate the application of finite element methods of analysis based on Eurocode on practical examples. Buckling limit state and calculation of design resistance of the cylindrical shell with the opening will be shown. On the example of a pedestrian bridge, the stability of plated structural members with web opening will be analysed. The examples of steel girder frames will illustrate the application of global and local imperfections in calculating the design resistance of the structural steel members. The comparison between methods for the design of frame structure is done on the example of the two-storey frame structure. The paper briefly reviews the most important novelties brought about by Eurocode 3 for steel structures. A review of the new advanced design methods in the next edition of the Eurocode for steel structures will be given
Environment Protection – International Regulation
Get PDFIn this article, the authors analyze phases of the development of international environmental law, stating the main features of each, and the relevant international instruments adopted in this area. Special emphasis is put on the importance of the United Nations Conference on the Human Environment (Stockholm 1972), and its formulated principles which serve as the foundation of regulative of this area in the national legislatures of the states that supported the Declaration. The Stockholm Declaration prompted the establishment of special institutions for environmental protection and the constitution of the Regional Environmental Systems. The authors also analyze The Rio Declaration on Environment and Development, which took place in Rio De Janeiro in June 1992. The principles of the Declaration emphasize the idea of establishing a balance between environmental protection and the right to the development. The development and use of resources for the purpose of development have gained the same significance as the protection of the environment. The paper presents an overview of fragmentary and sectoral legal rules concerning the following areas: conservation of living nature and cultural heritage; ozone layer atmospheres and climate; marine and ocean environments; hazardous waste. A series of acts passed under the auspices of the UN achieved political agreement on the need to protect the environment, but the construction of a corpus of binding legal rules is still in its initial phase
Recycled Aggregate Mortar Made with the Recycled Concrete Aggregate and Fly Ash
Get PDFWith the aim of sustainable development of the construction industry, a large number of theoretical and practical research is currently being carried out on the possibilities of using various recycled materials in cement composites. The paper presents one possibility of designing the composition of a mortar-type composite made with recycled aggregate and fly ash. In order to improve the properties of the recycled aggregate, sodium silicate was used. The investigated properties included in the fresh state: density and consistency, measured by the flow-table method, and in the hardened state: density, flexural strength and compressive strength. The mixture made with sodium silicate and with recycled aggregate showed the lowest bulk density in the fresh state, and the stiffest consistency. In the hardened state, the mentioned mixture had the highest values of flexural strength and compressive strength, with the lowest value of density
Мобилно ласерско скенирање за детаљно дигитално топографско картирање
Get PDFMobile Laser Scanning (MLS) is a technique characterized by high data acquisition efficiency and
level of detail. However, a lot of information contained in the LiDAR point cloud is only implicitly
available. Therefore, in order to create a digital topographic map from a large quantity of MLS survey data, it is necessary to define a methodology that requires a combination of various software tools. In general, the applied methodology mainly depends on the final product specifications (data model, accuracy, level of detail, etc.). This paper describes the standard methodology of creating a detailed digital topographic map using data collected by MLS, which proved to be two times faster than the conventional methods (total station or GNSS survey)
Uniaxial compressive strength test before and after standard fire test on rock mass
No full textThe paper presents uniaxial compressive strength test according to SRPS EN 1926. Uniaxial
compressive strength test was performed on 12 identical cube-shaped specimen’s dimensions 70 mm x
70 mm x 70 mm, which are made of sandstone. Samples were brought form Laz tunnel and were
divided into two groups of six samples. First group of samples consists of 6 samples tested for uniaxial
compressive strength. Second group of samples consists of 6 samples exposed to standard fire test
according to SRPS EN 1363-1, with the intention to test uniaxial compressive strength after standard
fire test. The aim of this study was to examine the uniaxial compressive strength of the rock, before
and after standard fire test on the rock mass. The paper presents the strengths of the specimens tested
before and after standard fire test