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Climatic wind tunnel for material and structures investigation
Král, Radomil ; Pospíšil, Stanislav
The paper deals with a description of the new climatic wind tunnel laboratory built in historical city Telcˇ. As a separate unit of the Institute of Theoretical and Applied mechanics of the Academy of Science of the Czech Republic, the tunnel will be used for fundamental research in engineering problems within civil engineering, architecture, heritage care and in other fields where wind effects appear along with further factors. The paper presents essential information about the interior layout of the tunnel together with description of advanced facilities serving for simulation of a strong wind, rain, freeze and solar heat radiation. Fundamental part of the paper is devoted to pressure losses determination. Using two different methods, the principal parts of the tunnel are designed taking into account both the optimal flow characteristics and flow resistance.
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Experimental and numerical verification of vortex-induced vibration of hangers on the footbridge
Urushadze, Shota ; Pirner, Miroš ; Pospíšil, Stanislav ; Král, Radomil
The paper deals with vortex-induced oscillations of footbridge hangers at a very low wind speed. The two-spans (2x50m) reinforced concrete structure with the central pylon (25m height) is designed as the harp system of hangers with circular cross-section. The oscillations were observed at the low wind speed and the high double amplitudes has been measured. The wind-excited deformation shape corresponded to the 6th, 7th and 8th natural modes of a hanger. The individual hanger as well as thein group were analysed to estimate the dynamic response, possible aeroelastic vibration and special interference or coupling effects. It also includes proposal for the elimination of the extensive vibration. The analysis is complemented by numerical investigation using Computational Fluid Dynamics methods.
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Multipurpose experimental rig for aeroelastic tests of bridge girders and slender beams
Pospíšil, Stanislav ; Král, Radomil ; Náprstek, Jiří
The bridges, footbridges and broadcast towers create an important subset of infrastructure subjected to dynamic loading of various origins. Especially, exposed to wind, they are susceptible to vibrations under certain circumstances due to pure load action or aero-elastic effects. This means that once an element or a structure starts to vibrate, a complex interaction between the moving boundary and the airflow takes place. Because of the complexity, the research has been in progress for several decades in both theoretical and experimental way. The article describes an original and multi-purpose experimental frame for the analysis of complex linear and non-linear aspects of aero-elastic behavior of the slender beams. The apparatus meets the rigorous theoretical assumptions and allows very precise and quick adjustment of the stiffness and mass of the structure, which is not always possible with a traditional "parallel spring-supported bridge" approach used by many researchers.
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