Vibration control has emerged as a significant concern in civil engineering, aiming to minimize the displacement and stress exerted on structures during seismic events. The accelerated oscillator damper (AOD), which is a damping device that depends on acceleration, has been demonstrated to be highly effective. However, in the case of traditional bridges, it is difficult to accurately place the secondary mass, spring, and damping components at the piers. Additionally, it has been found that as a general single-degree-of-freedom (SDOF) damping device, a significant limitation of the AOD system is its insufficient damping effect in the near-resonance region. This study presents a strengthened AOD with a liner spring (SAOD-LS), in which the secondary spring and damper are linked to the primary structure rather than being attached to the piers. This design not only provides enough space for the secondary system but also has a higher amplification factor of secondary spring and damping components compared with the original layout. In addition, we suggest a nonlinear spring device (NSD) that includes connecting rods and inclined linear springs arranged in a diamond configuration. This innovative design is intended to introduce nonlinear stiffness characteristics into the equivalent stiffness, thereby improving the device’s performance and providing effective anti-resonance features in the near-resonance region. We have confirmed the motion equations for the SAOD-LS and used finite element (FE) analysis to validate the formulation of the equivalent external force and deformation of the NSD. We have thoroughly investigated both the SAOD-LS and the strengthened AOD equipped with NSD as the secondary spring (SAOD-NSD) for their potential implementation in a bridge project. These damping systems demonstrate exceptional performance and robustness, making them highly suitable for enhancing structural resistance to seismic activity.

To investigate the large-amplitude flutter response of the Old Tacoma Narrows Bridge (OTNB), this study employed a 1:8.53 scaled full-bridge aeroelastic model with a main span of 100 m. In natural wind, the aeroelastic model test reproduced the first antisymmetric torsional mode (A-T-1) flutter reported for the OTNB. Numerous flutter events of the aeroelastic model were recorded, including time-histories of girder vibrations, forces of the hangers and main cables, wind speeds, and wind directions. Three representative flutter cases with distinct flutter responses under different wind conditions were selected for detailed analysis. In Cases 1 and 2, the torsional displacement of the girder shows distinct developing and steady stages, similar to the limit cycle oscillations observed in wind tunnel tests. In Case 3, the torsional displacement amplitude of the girder exhibits alternating growth and decay. This behavior is seldom observed in conventional wind tunnel tests. In the three cases, the wind speed at the girder height is nearly uniform, and the wind direction remains consistent across the span. The girder’s torsional displacement at the three-quarter span section reaches a maximum of 14°, and the maximum fluctuating forces of the hangers and main cables reach 37.8% and 10.8% of the static equilibrium forces, respectively. These results demonstrate that the large-scale full-bridge aeroelastic model in natural wind not only reproduces the A-T-1 flutter of the OTNB but also provides new insights into large-amplitude flutter responses under nonstationary wind fields.