Free Lateral Vibrations of Suspension Bridges

by Ahmed M. Abdel-Ghaffar, (A.M.ASCE), Research Fellow; Civ. Engrg. Dept., California Inst. of Tech., Pasadena, Calif.,

Serial Information: Journal of the Structural Division, 1978, Vol. 104, Issue 3, Pg. 503-525

Document Type: Journal Paper

Abstract: A method is developed based on a linearized theory and the finite-element method. The method involves two distinct steps: (1)Specification of the potential and kinetic energies of the bridge, (2)use of finite element technique to: (a)discretize the structure into equivalent systems of finite elements; (b)select the displacement model most closely approximating the real case; (c)derive the element and assemblage stiffness and inertia properties; and finally (d)form the matrix equations of motion and the resulting eigenproblems. A numerical example is presented to illustrate the applicability of the analysis and to investigate the dynamic characteristics of laterally vibrating suspension bridges. This method eliminates the need to solve transcendental frequency equations, simplifies the determination of the energy stored in different members of the bridge, and represents a simple, fast, and accurate tool for calculating the natural frequencies and modes of lateral vibration by means of a digital computer.

Subject Headings: Finite element method | Suspension bridges | Vibration | Equations of motion | Natural frequency | Linear functions |

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