Nonlinear characteristics of suspension bridges with inclined hangers under harmonic excitations and countermeasures for vibration control

Spatially arranged cable systems and inclined hangers are becoming popular in shallow pedestrian suspension bridges to improve the lateral stiffness. However, the vertical motions of bridge decks under vortex shedding or pedestrian loadings may still cause annoying vibrations which may induce primary and internal resonances of the deck-cable systems. This study investigates the primary and internal resonances of the deck-cable systems with inclined hangers when the bridge deck suffers from vertical harmonic motion. A six-degrees-of-freedom (6-DOFs) mathematical model is adopted to simulate the linear and nonlinear dynamics of a cross-section of the bridge deck. Nonlinear behaviors of the structural system are systematically studied for the conditions under which internal resonance between two lower modes of the deck will occur. The analysis is conducted with the incremental harmonic balance method. The deck heaving mode in primary resonance does not exhibit distinct nonlinear property with different force magnitude, but notable nonlinearity is observed in the amplitude–frequency curve of the deck torsional mode. The nonlinear behavior of the structural system during the 1:2 internal resonances of the first two modes is also studied. Knowledge gained from this study may help in the vibration control of this type of bridge structures.