scholarly journals Thermo – mechanical model of concrete pavement in hardening phasis

2021 ◽  
Author(s):  
Jakub Veselý ◽  
Petr Pánek ◽  
Ludvík Vébr
Keyword(s):  
Mechanical Model ◽  
Concrete Slab ◽  
Climatic Conditions ◽  
Concrete Pavement ◽  
Point Of View ◽  
Transfer Model ◽  
Layer System ◽  
Weak Formulation ◽  
Base Functions ◽  
Maximum Temperatures

This paper is focused on the analysis of concrete pavements using finite element method (FEM). Specifically, it deals with the analysis of temperatures in the initial phasis of hardening and their influence on mechanical behavior of concrete pavement. High temperatures from hydration and climatic conditions in the early phase of concrete hardening co-operate and may initiate the formation of a network of micro-cracks on the surface of the concrete slab. The resulting temperatures (from hydration and climate) can theoretically be positively influenced by determining the start of concreting, so that the maximum temperatures do not meet at the same time. However, from a practical point of view the use of retarders is more realistic. Another possibility is to reduce the hydration heat by changing the composition of the concrete mixture (amount of cement, type of cement, use of alternative binders). Based on the knowledge of the material composition of the concrete and the specific temperature behavior during the concrete laying, it will be possible to predict the durability of concrete pavement in the future. Using weak formulation FEM model with quadratic base functions, the 2D heat transfer model was created. Boundary conditions were determined from experimental measurement on highway D1 in the Czech Republic. When this model was fitted to experimental data, the 3D coupled thermo - mechanical model was created. Soil and concrete elastic material characteristics had been taken over from Czech technical norms. Soil was modelled as Winkler-Pasternak 2D plate. Parameters c1 a c2 were assessed from comparison with 3D model with soil modelled as multiple layer system.

scholarly journals THERMO-MECHANICAL MODEL FOR CONCRETE PAVEMENT

2021 ◽  
Vol 30 ◽  
pp. 121-125
Author(s):  
Jakub Veselý ◽  
Vít Šmilauer
Keyword(s):  
Mechanical Model ◽  
Static Load ◽  
Transfer Problem ◽  
Concrete Slab ◽  
Concrete Pavement ◽  
Load Test ◽  
Static Load Test ◽  
Interface Elements ◽  
The Difference ◽  
Field Static

This paper describes a numerical thermo-mechanical model for concrete pavement, implemented in OOFEM software. The thermal part is a heat transfer problem with appropriate initial and boundary conditions (sun irradiation, radiation and convection), calibrated from experimental data. Heat release from cement hydration is also included, calibrated for commonly used cements to demonstrate the difference that can be achieved with the binder selection. The mechanical part of the problem is composed of a 3D elastic concrete slab, subsoil Winkler-Pasternak elements and 1D interface elements, allowing separation in tension. The Winkler-Pasternak constants C1 and C2 were firstly determined from TP170 document and refined later from static load tests on the highway. The model validates well temperature field, static load test and provide several useful insight such as feasible time for summer casting, stress/strain fields and slab separation from the base.

scholarly journals Analysis of temperature gradient in concrete pavement

2018 ◽  
Vol 67 (4) ◽  
pp. 59-70
Author(s):  
Grzegorz Rogojsz
Keyword(s):  
Thermal Stress ◽  
Temperature Distribution ◽  
Temperature Gradient ◽  
Air Temperature ◽  
Experimental Research ◽  
Analytical Methods ◽  
Concrete Slab ◽  
Climatic Conditions ◽  
Concrete Pavement

The paper presents the results of experimental research that is the continuation of the research conducted as a part of a Ph.D. dissertation. The experimental research consisted in measuring the temperature at various depths inside a concrete slab, including its surface, and measuring the air temperature. The temperature distribution was measured on a concrete slab with dimensions similar to real road slab dimensions. The aim of the research was to determine the temperature gradient in the concrete slab in Polish climatic conditions and to verify the available analytical methods. Keywords: temperature gradient, concrete pavement, thermal stress in concrete pavement.

scholarly journals New Deterministic Mathematical Model for Estimating the Useful Energy Output of a Medium-Sized Solar Domestic Hot Water System

Energies ◽  
2021 ◽  
Vol 14 (10) ◽  
pp. 2753
Author(s):  
Miroslaw Zukowski ◽  
Walery Jezierski
Keyword(s):  
Thermal Power ◽  
Optimization Procedure ◽  
Climatic Conditions ◽  
Point Of View ◽  
Hot Water ◽  
Energy Output ◽  
Daily Consumption ◽  
Software Environment ◽  
Optical Efficiency ◽  
Domestic Hot Water

According to the authors of this paper, the mathematical point of view allows us to see what sometimes cannot be seen from the designer’s point of view. The aim of this study was to estimate the influence of the most important parameters (volume of heat storage tanks, daily consumption of domestic hot water, optical efficiency, heat loss coefficient, and total area of a solar collector) on the thermal power output of solar domestic hot water (SDHW) system in European climatic conditions. Three deterministic mathematical models of these relationships for Madrid, Budapest, and Helsinki were created. The database for the development of these models was carried out using computer simulations made in the TRNSYS software environment. The SDHW system located at the Bialystok University of Technology (Poland) was the source of the measurement results used to validate the simulation model. The mathematical optimization procedure showed that the maximum annual useful energy output that can be obtained from 1 m2 of gross collector area is 1303 kWh in the case of Madrid, 918.5 kWh for Budapest, and 768 kWh for Helsinki weather conditions.

scholarly journals Variation in Ectosymbiont Assemblages Associated with Rock Pigeons (Columba livia) from Coast to Coast in Canada

Diversity ◽  
2020 ◽  
Vol 13 (1) ◽  
pp. 9
Author(s):  
Alexandra Grossi ◽  
Heather Proctor
Keyword(s):  
Columba Livia ◽  
The United States ◽  
Climatic Conditions ◽  
Assemblage Structure ◽  
Meteorological Variables ◽  
Urban Center ◽  
Sampling Locations ◽  
Maximum Temperatures ◽  
Symbiont Species ◽  
Maximum Humidity

When a species colonizes a new area, it has the potential to bring with it an array of smaller-bodied symbionts. Rock Pigeons (Columba livia Gmelin) have colonized most of Canada and are found in almost every urban center. In its native range, C. livia hosts more than a dozen species of ectosymbiotic arthropods, and some of these lice and mites have been reported from Rock Pigeons in the United States. Despite being so abundant and widely distributed, there are only scattered host-symbiont records for rock pigeons in Canada. Here we sample Rock Pigeons from seven locations across Canada from the west to east (a distance of > 4000 km) to increase our knowledge of the distribution of their ectosymbionts. Additionally, because ectosymbiont abundance can be affected by temperature and humidity, we looked at meteorological variables for each location to assess whether they were correlated with ectosymbiont assemblage structure. We found eight species of mites associated with different parts of the host’s integument: the feather dwelling mites Falculifer rostratus (Buchholz), Pterophagus columbae (Sugimoto) and Diplaegidia columbae (Buchholz); the skin mites: Harpyrhynchoides gallowayi Bochkov, OConnor and Klompen, H. columbae (Fain), and Ornithocheyletia hallae Smiley; and the nasal mites Tinaminyssus melloi (Castro) and T. columbae (Crossley). We also found five species of lice: Columbicola columbae (Linnaeus), Campanulotes compar (Burmeister), Coloceras tovornikae Tendeiro, Hohorstiella lata Piaget, and Bonomiella columbae Emerson. All 13 ectosymbiont species were found in the two coastal locations of Vancouver (British Columbia) and Halifax (Nova Scotia). The symbiont species found in all sampling locations were the mites O. hallae, H. gallowayi, T. melloi and T. columbae, and the lice Colu. columbae and Camp. compar. Three local meteorological variables were significantly correlated with mite assemblage structure: annual minimum and maximum temperatures and maximum humidity in the month the pigeon was collected. Two local meteorological variables, annual maximum and average temperatures, were significantly correlated with louse assemblages. Our results suggest that milder climatic conditions may affect richness and assemblage structure of ectosymbiont assemblages associated with Rock Pigeons in Canada.

scholarly journals Non-destructive ultrasonic tomography for concrete pavement evaluation: signal processing and image analysis of crucial parameters

2017 ◽  
Vol 10 (6) ◽  
pp. 1182-1191
Author(s):  
L. S. SALLES ◽  
J. T. BALBO ◽  
L. KHAZANOVICH
Keyword(s):  
Signal Processing ◽  
Concrete Slab ◽  
Low Frequency ◽  
Concrete Pavement ◽  
Ultrasonic Tomography ◽  
Transverse Cracks ◽  
Pavement Maintenance ◽  
Use Of Technology ◽  
Pavement Evaluation ◽  
Non Destructive

Abstract In recent years, due to the destructive and unproductive character of pavement specimen extraction, pavement maintenance technology intensified the use of non-destructive techniques for pavement evaluation which resulted in the development of several devices and evaluation methods. This paper describes the use of technology based on low frequency ultrasonic tomography for evaluation of concrete pavement parameters. The equipment was applied in three experimental sections with different concrete pavements built at the University of Sao Paulo campus. The ultrasonic signal processing is given. The results analysis enables the efficient and reliable identification of thickness and reinforcement position within the concrete slab. Construction problems were evidenced in one of experimental sections with thickness deficiencies and reinforcement in a position below projected. Furthermore, the use of a novel concrete quality indicator was correlated with the presence of transverse cracks and alkali-silica reaction within the sections.

scholarly journals Thin-film-induced morphological instabilities over calcite surfaces

2015 ◽  
Vol 471 (2176) ◽  
pp. 20150031 ◽  
Author(s):  
R. Vesipa ◽  
C. Camporeale ◽  
L. Ridolfi
Keyword(s):  
Morphological Evolution ◽  
Water Film ◽  
Environmental Parameters ◽  
Climatic Conditions ◽  
Point Of View ◽  
Theoretical Point ◽  
Carbon Dioxide Transport ◽  
Physical Mechanisms ◽  
Water Films ◽  
Dissolved Ions

Precipitation of calcium carbonate from water films generates fascinating calcite morphologies that have attracted scientific interest over past centuries. Nowadays, speleothems are no longer known only for their beauty but they are also recognized to be precious records of past climatic conditions, and research aims to unveil and understand the mechanisms responsible for their morphological evolution. In this paper, we focus on crenulations, a widely observed ripple-like instability of the the calcite–water interface that develops orthogonally to the film flow. We expand a previous work providing new insights about the chemical and physical mechanisms that drive the formation of crenulations. In particular, we demonstrate the marginal role played by carbon dioxide transport in generating crenulation patterns, which are indeed induced by the hydrodynamic response of the free surface of the water film. Furthermore, we investigate the role of different environmental parameters, such as temperature, concentration of dissolved ions and wall slope. We also assess the convective/absolute nature of the crenulation instability. Finally, the possibility of using crenulation wavelength as a proxy of past flows is briefly discussed from a theoretical point of view.

The speciation continuum and species relations between populations: in search of agreement between the theory and practice of systematics

2021 ◽  
pp. 173-179
Author(s):  
Oleksandr Zinenko
Keyword(s):  
Reproductive Isolation ◽  
Species Concept ◽  
Climatic Conditions ◽  
Point Of View ◽  
Theory And Practice ◽  
Hybrid Origin ◽  
Isolated Populations ◽  
As Species ◽  
Mitochondrial Cytochrome B ◽  
Traditional Taxonomy

From an evolutionary point of view, the achievement of species status by a group of populations is an ongoing process (except for rare cases of instantaneous speciation), during which isolated populations acquire traits and adaptations that minimize gene flow between them. However, depending on the group, the ways and timing of the gaining of reproductive isolation may be different. In such a complex group for systematics as small vipers (genus Vipera, subgenus Pelias), there are a number of problematic situations for species delimitation: the ability to form hybrids and hybrid populations between species, adaptive hybridization and hybrid speciation, and possible traces of reversed speciation, which indicate that complete and irreversible reproductive isolation may not be achieved at all. The effectiveness of reproductive isolation largely depends on external factors, mostly related to the range spatial structure, ecology of species in areas of sympatry, as well as climatic conditions and their changes, landscape dynamics, etc. The only species concept that allows to describe new species in the absence of reproductive isolation, recognizes the possibility of hybrid and reverse speciation — de Queiroz unified species concept — is practically unsuitable due to the need to consider as species a large number of isolated populations. Therefore, the solution is a conservative approach in practical taxonomy, which takes into account as a species criterion the ecological divergence of species, the possibility of their sympatric existence, which is usually achieved at 5% divergence of the mitochondrial cytochrome b gene. Stabilized hybrid populations occupying distinct ecological niche different from those of parental species also deserve recognition as species of hybrid origin. Not only species deserves to be protected, but also a distinguishable and diverged group of populations — Evolutionary Significant Unit (ESU) or subspecies in traditional taxonomy.

Digital monitoring system of equipment for the analysis of fuel and lubricants quality

2021 ◽  
Vol 04 (1) ◽  
pp. 54-54
Author(s):  
V. R. Nigmatullin ◽  
◽  
I. R. Nigmatullin ◽  
R. G. Nigmatullin ◽  
A.M. Migranov ◽  
...  
Keyword(s):  
Monitoring System ◽  
High Performance ◽  
Chemical Elements ◽  
Large Data ◽  
Climatic Conditions ◽  
Point Of View ◽  
Friction Units ◽  
Digital Monitoring ◽  
Wear Products ◽  
The Cost

Currently, to increase the efficiency of industrial production, high-performance and expensive technological equipment is increasingly used, in which the weakest link, from the point of view of efficiency and reliability, is the components and parts of heavily loaded tribo – couplings operating both at significantly different temperatures (conditionally under lighter conditions, the temperature difference can be 100-120 degrees) and climatic conditions (high humidity, the presence of abrasives and other chemical elements in the atmosphere). As the results of the analysis of the frequency of failures of friction units and, accordingly, the cost of their restoration reach 9-20 percent of the cost of all equipment, without taking into account significant losses of income (profit) of the enterprise from downtime. The solution of this problem is based on the study of the wear rate of friction units by the wear products accumulated in working oils, cooling lubricants, and greases. A digital equipment monitoring system (DSMT) has been developed and implemented, which includes dynamic recording of the number of wear products and oil temperature by original modern recording devices, followed by the technology of their processing and use. The system also includes methods for finding the necessary information in large data sets useful and necessary in theoretical and practical terms with a similar technique controlled by a digital monitoring system. The advantages of SMT are the ability to predict the reliability of the equipment; reduce production risks and significantly reduce inefficient costs.

Master curves for the response of layered systems to compressional seismic waves

1967 ◽  
Vol 57 (3) ◽  
pp. 515-543 ◽  
Author(s):  
Luis M. Fernandez
Keyword(s):  
Seismic Waves ◽  
Transfer Functions ◽  
Point Of View ◽  
Time Lags ◽  
Master Curves ◽  
Layer System ◽  
Crust And Upper Mantle ◽  
Response Characteristics ◽  
Families Of Curves ◽  
Short Time

abstract The layers of the earth's crust act as a filter with respect to seimic energy arriving at a given station. Consequently the motion recorded at the surface depends not only on the frequency content of the source and on the response characteristics of the recording instrument, but also on the elastic parameters and thicknesses of the transmitting layers. This latter dependence is the basis for a method of investigating the structure of the crust and upper mantle. To facilitate this investigation a set of master curves for the transfer functions of the vertical and horizontal component of longitudinal waves and their ratios is presented. The calculation of these curves is in terms of a dimensionless parameter. This calculation allows one to group the curves corresponding to different crustal models into families of curves. The characteristics of these curves are discussed from the point of view of their “periodicity” in the frequency domain and of their amplitude in order to investigate the influence of the layer parameters. Considerations, either of constructive interference or of Fourier analysis of a pulse multiply reflected within the layer system, reveal that the amplitudes of the transfer curves depend on the velocity contrasts at the interfaces of the system. The “periodicity” or spacing of the peaks depends on the time lags between the first arrivals and the arrivals of the different reverberations. Closely spaced fluctuations correspond to large-time lags, and widely spaced fluctuations to short-time lags.

scholarly journals Performance Analyses of Temporary Membrane Structures: Energy Saving and CO2 Reduction through Dynamic Simulations of Textile Envelopes

2018 ◽  
Vol 10 (7) ◽  
pp. 2548 ◽  
Author(s):  
Mariangela De Vita ◽  
Paolo Beccarelli ◽  
Eleonora Laurini ◽  
Pierluigi De Berardinis
Keyword(s):  
Energy Saving ◽  
Environmental Sustainability ◽  
Co2 Reduction ◽  
Energy Performance ◽  
Climatic Conditions ◽  
Point Of View ◽  
Thermal Mass ◽  
Membrane Structures ◽  
Dynamic Simulations ◽  
Carbon Reduction

The aim of this research, carried out in collaboration with Maco Technology Inc., was to analyse the energy performance of temporary textile structures that are often used to host itinerant events. This paper illustrates the dynamic simulations carried on the Ducati Pavilion, designed by Maco Technology, which hosted Ducati staff during the different stages of the Superbike World Championship. Specific aspects relating to the structural/constructive system of the project were also analysed. The theme of energy saving and carbon reduction is of great importance in temporary and itinerant structures and environmental sustainability in relation to the materials used, storage, re-use, mode of transport and ability to respond efficiently to the climatic conditions of the installation sites is an important aspect. The Ducati Pavilion was modelled and analysed from an energy point of view using Design Builder software. Ways of improving performance were analysed under summer conditions. The paper focuses on the importance of optimizing the performance of textile envelopes: the methodology proposed allows visible savings in terms of energy consumption and achieves good levels of environmental comfort in temporary buildings with low thermal mass structure.

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