Technical Transactions iss. 12. Civil Engineering iss. 2-B

Technical Transactions iss. 12. Civil Engineering iss. 2-B

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Collection items (30)


The features of snow loads on building roofs

Pichugin, S. F., Dryzhyruk, Yu. V., Popovich, N. M., Chernetska, I.V.
Article
2015
In this paper the probabilistic model of the snow accumulation on the roofs with height discontinuity was worked out, the decreasing coefficient for the snow load weight was received and the ways of their application in the designing were elaborated. The probabilistic model for impulse stochastic process of snowfall sequence was developed. Data from meteorological stations in Ukraine allow determination of statistical characteristics: average annual snowfall amount and exponential distribution of values of one snowfall. The law of intensity distribution of snow melting has been determined experimentally. The territorial zoning map of Ukraine by characteristic values of the snow load on the roofs that emanate heat was developed.

Dynamics of snow melting on tents during possibly threatening precipitation

Kimbar, Grzegorz
Article
2015
Lightweight tent structures are allowed under European codes to be designed for reduced snow load if the interior of a tent is appropriately heated. The dependence of the resultant snow load on snowfall rate is considered in this paper for such cases. A simple thermodynamic model of the heat flux is derived. Numerical simulation reveals the occurrence of a precipitation rate threshold value above which safety measure provided by heating becomes ineffective.

Investigations of Strouhal numbers of iced cable models of cable-supported bridges with respect to angle of wind attack

Górski, Piotr, Tatara, Marcin, Pospišil, Stanislav, Kuznetsov, Sergej, Marušić, Ante
Article
2015
The influence of the ice accretion, angle of attack and Reynolds number on the flow field around iced cables of cablesupported bridges is not clearly understood. The Strouhal number is one of the most important parameters which is necessary for an analysis of the vortex excitation response of slender structures. This paper presents the method and results of wind tunnel investigations of the Strouhal number of stationary iced cable models of cable-supported bridges. The investigations were conducted in a climatic wind tunnel laboratory of the Czech Academy of Sciences in Telč. The methodology leading to the experimental icing of the inclined cable model in the climatic section of the laboratory was prepared. The shape of the ice on the cable was registered by photogrammetry and numerical evaluation. For the aerodynamic investigations, the iced cable model in a smaller scale was reproduced using a 3D printing procedure. The Strouhal number was determined within the range of the Reynolds number between 2.4·104 and 16.4·104, based on the dominant vortex shedding frequency measured in the flow behind the model. The model was orientated at three principal angles of wind attack for each of the Reynolds number values. In order to recognize the tunnel blockage effect, the Strouhal number of a smooth circular cylinder was tested. Strong agreement with the generally reported value in the subcritical Reynolds number range for a circular cylinder was obtained.

Assessing environmental actions from modern meteorology

Fikke, Svein M., Nygaard, Bjørn Egil K.
Article
2015
This paper gives an overview of current achievements where modern weather forecasting techniques are implemented for the assessment of especially ice and wind loadings on electrical overhead lines, TV towers, masts and similar infrastructure. Modern numerical weather prediction models (NWP) incorporate far more details on e.g. cloud physics and dynamics than those generally necessary for regular weather forecasts. Such models describe in principle all physical and dynamical processes in the atmosphere in 3-D. In combination with detailed data on the physical properties of land and water surfaces, it is now possible to obtain realistic values of weather parameters related to wind, turbulence, precipitation and atmospheric icing down to a horizontal scale of a few hundred meters. Such models are therefore powerful tools for the planning and final design for various infrastructures in remote terrain where little or no weather data can provide sufficient bases for the establishment of extreme weather loads necessary for their design.

Applications of “snowind” engineering – climatic wind tunnel methods

Delpech, Philippe, Thiis, Thomas
Article
2015
Transport and deviation of snow by wind induce many constraints on buildings, vehicles and industrial systems. A selection of questions from snow-wind engineering are presented in the paper. The experimental method that was undertaken to investigate these questions makes use of a large climatic wind tunnel, partly designed to address snow engineering problems at full scale: snow penetration in buildings, into ventilation systems of buildings and vehicles and snow or ice accretions on structures.

Simulation of concrete corrosion and interaction surfaces using cellular automata

Zaborski, Adam
Article
2015
This paper presents a new approach to determining the synergetic effects of environmental conditions and mechanical loading on the load bearing capacity of structural members. Cellular automata are used to estimate the residual strength of a RC section subjected to concrete corrosion. The evolution of interaction surfaces resulting from bending moments and axial force caused by a continuous degradation process is presented.

Characterization of shear stress distribution on a flat roof with solar collectors

Thiis, Thomas, Ferreira, Almerindo D., Molnar, Markus, Erichsen, Arnold V.
Article
2015
In the search for new renewable energy sources, photovoltaic systems and solar thermal collectors have become more common in buildings. With increased efficiency and demand for energy, solar power has also become exploitable at higher latitudes where snow is a major load on buildings. For flat roofs, one usually expects approximately 80% of the snow to be eroded off the roof surface. Installing solar panels would change this since the flow pattern and wind conditions on the roof are affected by their presence. This study shows the erosion of sand particles from underneath solar panels of various configurations associated with different wind velocities. The pattern of erosion is used to determine the relative friction velocity, u*REL, of the wind on the roof. This value is the friction velocity on the roof relative to the friction velocity on a flat roof without solar panels. The experiments, conducted in a wind tunnel, show that the area where u*REL is 0 and where it is expected that sand and snow will accumulate in case of an upwind particle source and decrease with increasing distances between roof and solar panel. It is also shown that a larger gap between the solar panel and roof surface creates larger erosion zones, where u*REL > 1 for both wind directions. Since the erosion is closely linked to the air flow under the solar panels, and that higher air velocity increases the erosion, it is likely that a larger solar panel, extending higher into the free air flow would be desirable to avoid snow accumulation on a flat roof with solar panels. If the solar panel has large enough dimensions, the solar panels can be used as a deflector to decrease snow accumulation on flat roofs. With solar panels of the size in the current experiments, a building with a length smaller than the equivalent of x/L = 0.3 would have u*REL > 1 on most of the roof surface and would thus likely have a lower snow load than an equivalent float roof without solar panels.

An acoustic study of the auditorium hall to be located in the proposed building of the Applied Acoustics Laboratory of Cracow University of Technology

Szeląg, Agata, Flaga, Andrzej
Article
2015
This paper presents an acoustic study of the auditorium hall located in the proposed building of the Applied Acoustics Laboratory of Cracow University of Technology. The study shows a comparative analysis of two solutions to the acoustic adaptation of this room. The aim of this study was to demonstrate that with a given room shape and finishing materials, it is possible to optimize the sound quality of the interior through changes to some architectural details, for example, by the adequate formation and arrangement of finishing elements.

The effect of wall thickness and window position on efficient daylight utilisation in building interiors

Szczepańska-Rosiak, Eliza, Heim, Dariusz
Article
2015
This paper presents a numerical analysis of the daylighting of exemplary office interiors. Simulation results were obtained using a radiance model. The following indexes: UDI, DF, DA, DSP were calculated and analysed for different solutions of building façade. The construction differs in the total thickness of the wall. Two cases were considered: 25 cm and 50 cm opaque sections. Additionally, window magnitude changes from 0.36 m2 to 1.44 m2, with different shapes and locations relative to the centre of the wall. The idea of the work was to find out the architectural solution of the transparent element (geometry and magnitude) taking into account two criteria: decreasing solar heat gains; increasing the daylight utilisation factor. The results are presented in the form of a diagram of daylight distribution as well as average values of visual comfort indexes. The highest values of each indicator (DF, DA and DSP) were obtained for a centrally placed window 1.44 m2. However, the results of useful daylight index UDI depend on the assumed range and it is not easy to identify a relationship between window size and daylight efficiency.

Relationship between surface roughness and turbulence of natural winds near the ground surface

Sasaki, Ryoji, Akahoshi, Akinori, Uematsu, Yasushi
Article
2015
The design of low-rise buildings such that they can handle wind loads makes it necessary to accurately evaluate those wind loads, both on the structural framework and on the cladding/components. To this end, it is necessary to fully understand the characteristics of the wind near the ground around a building. This study sets out to develop a quantitative means of estimating the turbulence of the wind near the surface of the ground, based on field measurements obtained at different points across Japan. The surface roughness is evaluated based on several factors taken from a building information database. The relationship between these factors and the turbulence of the wind is discussed. The effect of the observation height, relative to the surface of the ground, on the turbulence is also investigated.