Modes and natural frequencies of suspension bridge oscillations

Abstract The natural frequencies of potential modes of suspension bridge oscillations constitute basic data required in studies for aerodynamic stability. The formulas presented herein were derived by the author in 1941–1943 and have since been tested, for simplicity and practical usefulness, by fifteen or more years of application in the author's office practice. They have also been independently checked, for validity and accuracy, by others using more difficult formulas involving transcendental (complex or hyperbolic) functions. The author's formulas appear to be the simplest and most practical thus far developed for the calculation of the natural frequencies of all possible modes of suspension bridge oscillations. For convenience of reference and application, these formulas are here assembled, derived and presented in definitive form, together with numerical examples to illustrate their practical application. The numerical examples are based on computations for the Mackinac Bridge.