The cables of the long-span bridge are usually featured as ultra-low frequency, hence making the acceleration unable to accurately capture the information, e.g. damping ratios, for assessing the cable state assessment and mitigating the excessive structural vibration. The displacement was approved to be more sensitive to the low-frequency vibration than the acceleration. However, there is still a lack of effective method to accurately monitor the long-term displacements of bridge cables using reference-free methods. To address this issue, this paper develops a novel acceleration-based approach for monitoring the long-term displacements of the cables of long-span bridges. In the monitoring scheme, recursive least squares method is utilized to conduct baseline correction in the time domain integration of acceleration. An adaptive band-pass filtering method considering cable vibration characteristics is used to eliminate noise, thus avoiding the difficulty of selecting the cut-off frequency by experience in traditional methods. A numerical test of an analytical cable model and a field experiment of the hanger of a full-scale suspension bridge are applied to the applicability and robustness of the developed method. Result shows that adaptive band-pass filter considering the vibration characteristics is suitable for estimating the displacements of the cables. The estimated displacements using the developed method agree well with the background truth in both time and frequency domains. 

A novel acceleration-based approach for monitoring the long-term displacement of bridge cables

In order to study the flutter of long-span pedestrian suspension bridge and its aerodynamic control, a 420m-span pedestrian suspension bridge is used as an engineering example, the wind-induced vibration of seven particular aerodynamic sections is studied by wind tunnel tests, and the soft flutter phenomenon of two kinds of aerodynamic sections is identified. The results show that the wind fairing and the wind-retaining plate measures are not necessarily effective measures to improve the wind-induced stability of long-span pedestrian suspension bridge, as these two measures may reduce the flutter stability: the wind fairing section in the positive angle of attack is prone to torsion-based soft flutter phenomenon, in which the vertical vibration spectrum contains multiple vibration frequencies, so the conventional formulation of the linearized self-excited forces is no longer satisfied; the wind-retaining plate section in the negative angle of attack is prone to soft flutter dominated by vertical vibration, and the beat vibration phenomenon is found in the torsional vibration time history of the wind-retaining section. Slotting in the center of the girder section can significantly change the flow state of the section, which is an effective measure to improve the flutter stability of the pedestrian suspension bridge.

https://www.mdpi.com/2075-5309/12/8/1173/pdf?version=1659942115

Research on Soft Flutter of 420m-Span Pedestrian Suspension Bridge and Its Aerodynamic Measures

Abstract Bridge construction is one of the cores of traffic infrastructure construction. To better develop relevant bridge science, this paper introduces the main research progress in China and abroad in 2021 from 12 aspects. The content consists of four parts in 12 aspects. The first part is about the bridge structure and analysis theories, including concrete bridge and high-performance materials, steel bridges, composite girders and cable-supported bridge analysis theories. The second part is about the bridge disaster prevention and mitigation, including bridge seismic resistance, vibration and noise reduction of rail transit bridges, monitoring and detection of steel bridge, hydrodynamics of coastal bridges, and durability of the concrete bridge under the complex environmental conditions. The last part is concerning the bridge emerging technologies, including bridge assessment and reinforcement, the technology in bridge structure test and intelligent construction and safe operation and maintenance of bridges. 

/pdf/state-of-the-art-and-annual-progress-of-bridge-engineering-v638sboe.pdf

Dongchun Qi

Papers

A new type of wind-resistance cable net for narrow suspension bridges and wind-resistance cable element for its calculation