A model for vortex-shedding induced oscillations of long-span bridges

摘要

The paper describes the extension to bridge decks of a model for the vortex-shedding induced loads, recently proposed by some of the writers, and already successfully applied to chimneys. The model, which operates in the time domain, schematically reproduces the load effect on the structure, due to the vortex-shedding, as an alternating force per unit length, with variable direction, frequency and phase, as a function of the relative wind velocity. The lock-in phenomenon is simulated by imposing the instantaneous correspondence of the excitation frequency with the oscillation frequency of the structure in a pre-selected range. Outside this interval, the frequency of the pulsating force is calculated through the Strouhal's Law. The limited number of aerodynamic parameters that are required, can be obtained from the usual section model tests. The results of a numerical investigation are compared with experimental results from section-model tests and full-scale measurements reported in the scientific literature.