Simulaciones numéricas de buffeting en puentes arriostrados causado por flujos vorticosos 2-D

WALTER B. CASTELLÓ; SERGIO PREIDIKMAN; JULIO C. MASSA

Revista Internacional de Desastres Naturales, Accidentes e Infraestructura Civil

Universidad de Puerto Rico

Lugar: Mayagüez, PR 00681-9041, Puerto Rico; Año: 2004 vol. 4 p. 27 - 40

1936-1483

The development of new materials and more sophisticated design methods per-mits to design structures in which resistance is maximized while weight is minimized. Under this design condition, a structure may result very flexible and highly susceptible to wind-excited motions. The possibility of buffeting produced by the aerodynamic interaction that occurs for two suspension bridges, set in parallel, is studied in the present work. To simulate this aeroelastic phenomenon in a simple way, the two bridges are modeled as two flat plates. Bridge "2", located downstream, is structurally modeled as a uniform, rigid plate on elastic supports. This bridge is immersed into a high vorticity dominated flow produced by the pre-sence of bridge "1", located upstream of the moving plate. Bridge "2" is structurally modeled as a uniform, rigid plate immerse into an initially uniform air flow. The mobile plate has two degrees of freedom: heave, a vertical motion of the mass center; and pitch, a rotation about the axis through the elastic center. The stiffness of the supporting cables is modeled by two springs that deflect when there is heaving/pitching motion and exert a force on the bridge which tries to return the mass center to its equilibrium position, and a moment which tries to return the deck to the horizontal position. Buffeting is introduced in the simulation through a sudden change of the pitch angle of bridge ?1?. Both bridges are aerodynamically modeled as sheets of vorticity. The unsteady, non-linear vortex lattice method was used to determine the aerodynamic loads. The present analysis is based on a numerical model that treats the bridges and the flowing air as elements of a single dynamical system. All the governing equations are numerically integrated, simultaneously and interactively in the time domain. The influence of the air speed and relative position of the bridges on the amplitude and frequency of the vibra-tions produced by the airflow as well as on the "flutter" speed are studied.