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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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Experimental and theoretical stability analysis of damped auto-parametric pendulum
Pospíšil, Stanislav ; Fischer, Cyril ; Náprstek, Jiří
The article describes an experimental and theoretical treatment of the auto-parametric pendulum damper modelled as a double-degree-of-freedom (DDOF) system. It is strongly non-linear, with the harmonic excitation being applied in the suspension point and interpreted for instance as an excitation by wind. The stability of the motion in a vertical plane is analysed in the meaning of semi-trivial vibration. This effect of stability loss and possible stability regain is very important from practical point of view, because the motion of an damper beyond the stability limits may act negatively and thus endanger the structure itself. Special experimental frame was developed.The stability of the system is analysed experimentally and compared with theoretical results.
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