Dynamic analysis of thin‐walled and variable open section beams with shear flexibility

The equations of motion of thin-walled beams with open cross-section, considering the effects of shear flexibility and rotatory inertia in the stress resultants, as well as variable cross-sectional properties are presented using a state variables approach. These equations are based on Vlasov's theory of thin-walled beams, which is modified to include the effects indicated above. The resulting equations are used in the determination of the natural frequencies of an open cross-section prestressed concrete beam. Comparisons with other formulations are also presented employing the waves dispersion equation.