Abstract
Introduction: Natural bending frequencies of externally prestressed steel beam have certain sensitivity to prestress force, so they can be used to find the magnitude of prestress force. Methods: To answer the question if the existence of externally prestressed tendons increases or decreases the natural bending frequencies of a simply supported steel beam, the calculating formula for natural frequencies is deduced by using the energy method from the view point of prestress mechanism and further verified by the finite element method. Using this formula of universal property, the influence of prestress force, eccentricity and cross-sectional area of tendons on natural bending frequencies of prestressed steel beam is clearly revealed. Results and Conclusion: For external prestressed steel beams with straight tendons, their natural frequencies increase with the eccentricity and cross-sectional area of the prestressed tendon, and the eccentricity has a much larger effect on natural frequencies than the cross-sectional area does. The prestress force has no influence on the oven-order frequencies but decreases the odd-order frequencies. With the increasing order number, the prestress effect is much weaker than the effects caused by the eccentricity and cross-sectional area of the tendon.
Highlights
Natural bending frequencies of externally prestressed steel beam have certain sensitivity to prestress force, so they can be used to find the magnitude of prestress force
With the increase of i, the prestress effect is much weaker than the effects caused by the eccentricity and the cross-sectional area of the tendons
The formula for natural bending frequencies (NBFs) of a supported externally prestressed steel beams (EPSBs) with straight tendons has been developed based on the mechanism of the prestressed system and can accurately reflect the variation of frequency with prestress parameters
Summary
Natural bending frequencies of externally prestressed steel beam have certain sensitivity to prestress force, so they can be used to find the magnitude of prestress force. Compared with ordinary steel beams, prestressed steel beams have been widely applied for a better economic benefit. Prediction of the change in natural vibration frequencies with varying magnitude of prestress force for externally prestressed steel beams (EPSBs) is the one of particular importance, especially when prestressed steel beams are subjected to dynamic excitation, such as earthquake and wind [1]. For an existed EPSB, it is hard to gauge its prestress force and to acquire its stress and deformation. The natural frequency of an in-service EPSB will change when the prestress force changes over
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