Compressive forces influence on the vibrations of double beams

Abstract

Abstract The influence of compressive forces on the lower and upper natural frequencies of the double beams has been studied in this article. Euler–Bernoulli’s hypotheses have been used to derive the natural frequency equations. Two asymmetric beams were assumed in this work, and four different boundary conditions were applied in these equations: Pinned–Pinned, Clamped–Clamped, Clamped–Free, and Clamped–Pinned. When the axial compressive force is increased about 18 times, it is observed that the lower natural frequencies decreased by 19% for PP beam, 8% for CC beam, 81% for CF beam, and 12% for CP beam. However, the greatest effect of the axial force on the higher frequencies is by reducing it in the CC beam by a ratio that does not exceed 2%. A rise in the values of axial compressive force causes a reduction in the lower natural frequencies, mostly for the CF beam, while it has a little effect on the higher natural frequencies. Similarly, when the compressive forces on the upper and lower beams fluctuate simultaneously, their effect is doubled on the frequencies when the axial compressive force on one of the two beams changes only.