Theoretical And Experimental Research On Natural Frequency Of Prestressed Concrete Simply Supported Beam

Damage detection according to vibrate test has been successfully used in common concrete structure, This method is based on the changes of dynamic characteristic fore and after damage. Compared with common reinforced concrete beams, force of prestressed tendons directly influences dynamic characteristic of structure members. In order to carry out damage detection of prestressed concrete simply supported beam, the dependency relation between force of prestressed tendons and dynamic characteristic is needed to be established. On this foundation, the relation between force of prestressed tendons and dynamic characteristic is discussed through theoretical analysis and experimental research. Dynamic test of five prestressed concrete simply supported beam are carried, according to the analysis of natural frequency in various condition, the main factors which influences dynamic characteristic (especially lower-order frequency) of prestressed concrete beams are discussed. In this paper, model of prestressed concrete simply supported beams is built. Present research state of dynamic characteristic of this aspect is summarized. Also influence of force of prestressed tendons to flexural vibration is discussed. The vibrate differential equation is established according to DËŠAlember principle, considered that prestressed concrete simple supported beams is subjected to both axial compressive force and fixing moment. The formula which is used to calculate natural frequency of simple supported beams under prestressing force is derived, the main factors of which influences natural frequency is researched. In addition, testing beam with unbonded straight-line tendons is established model by ANSYS (finite-element analysis). In the end, the comparison of theoretical calculation result and experimental data is carried and aberration is calculated. The comparison of theoretical calculation result and experimental data indicates that frequency of prestressed concrete simple supported beams is not only influenced by force of prestressed tendons, also the influence of position of prestressed tendons (eccentricity) can not be neglected. Although, there is some deviation between theoretical calculation result and experimental data, the formula can also accurately predict the change of natural frequency which is influenced by arrangement of prestressed tendons, and it has good reference value on project. Finally, reasons of deviation between theoretical calculation result and experimental data is discussed, the research of dynamic characteristic of prestressed concrete simple supported beams is hoped.