Vol. 2, No. 4, 2007

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ISSN: 1559-3959
A linear curved-beam model for the analysis of galloping in suspended cables

Angelo Luongo, Daniele Zulli and Giuseppe Piccardo

Vol. 2 (2007), No. 4, 675–694
Abstract

A linear model of curved, prestressed, no-shear, elastic beam, loaded by wind forces, is formulated. The beam is assumed to be planar in its reference configuration, under its own weight and static wind forces. The incremental equilibrium equations around the prestressed state are derived, in which shear forces are condensed. By using a linear elastic constitutive law and accounting for damping and inertial effects, the complete equations of motion are obtained. They are then greatly simplified by estimating the order of magnitude of all their terms, under the hypotheses of small sag-to-span ratio, order-1 aspect ratio of the (compact) section, characteristic section radius much smaller than length (slender cable), small transversal-to-longitudinal and transversal-to-torsional wave velocity ratios. A system of two integrodifferential equations is drawn in the two transversal displacements only. A simplified model of aerodynamic forces is then developed according to a quasisteady formulation. The nonlinear, nontrivial equilibrium path of the cable subjected to increasing static wind forces is successively evaluated, and the influence of the angle of twist on the equilibrium is discussed. Then stability is studied by discretizing the equations of motion via a Galerkin approach and analyzing the small oscillations around the nontrivial equilibrium. Finally, the role of the angle of twist on the dynamic stability of the cable is discussed for some sample cables.

Keywords
cables, twist, galloping, aeroelasticity, instability, bifurcation
Milestones
Received: 26 July 2006
Accepted: 2 February 2007
Published: 1 June 2007
Authors
Angelo Luongo
DISAT
Università degli Studi di L’Aquila
67040 L’Aquila (AQ)
Italy
Daniele Zulli
DISAT
Università degli Studi di L’Aquila
67040 L’Aquila (AQ)
Italy
Giuseppe Piccardo
DICAT
Università degli Studi di Genova
Via Montallegro, 1
16145 Genova (GE)
Italy