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This paper introduces a new accelerating algorithm, efficient match slimmer (EMS), specifically designed to lighten computational loads of sophisticated template matching algorithms, enabling these algorithms to be effectively run on single‐board computers. Utilizing EMS in conjunction with a robust template matching algorithm, we have developed Raspberry Vision—a compact, cost‐effective, and real‐time vision‐based system. Its compactness and portability facilitate a practical measurement strategy that not only minimizes the camera‐to‐target distance but also simplifies the camera calibration process in bridge displacement monitoring, thereby enhancing measurement accuracy. The performance of the system is estimated on two operational suspension bridges. The results demonstrate that Raspberry Vision, equipped with the measurement strategy, can significantly improve the measurement accuracy in the long‐span bridge test and is also suitable for cross‐sea bridge measurements. [ABSTRACT FROM AUTHOR]

This paper proposes a novel emergency aerodynamic measure, i.e. suspended flexible sheets (SFSs) with high strength, to suppress the vortex-induced vibrations (VIV) of bridge decks. The cost of the SFSs is very low, and the SFSs can be readily installed for an operational bridge in a short time. The control effectiveness of the SFSs is tested for a bluff box girder using wind tunnel experiments (the model scaling ratio is 1:36 and the range of Reynolds number is 1. 7 1 × 1 0 3 to 1. 1 2 × 1 0 5). The relevant parameters of the SFSs (installation location, height, counterweight form, and arrangement form) are systematically optimized. The experimental results show that the in-wind postures of the SFSs are critical for the control performance. The random waving of SFSs can disturb the airflow around the bridge deck at the lower surface, weaken the interaction between the vortex shedding from the upper and lower surfaces, and hence reduce the VIV response. The control performance of the aerodynamic measure can be significantly increased by using appropriate arrangements of the SFSs and counterweights. For the tested cases, the maximum reduction ratio of the VIV amplitude approximately reached 2/3. [ABSTRACT FROM AUTHOR]

Existing studies optimized the tuned mass damper (TMD) for vortex-induced vibration (VIV) control of bridges based on an empirical linear model or Scanlan's nonlinear model, which cannot accurately simulate the effect of the vortex-induced force and hence results in a TMD design that lacks effectiveness or robustness. Four vortex-induced force models are considered to systematically analyze the influence of force models on TMD design for VIV control. The design results based on various vortex-induced force models, as well as three design formulas, are compared in terms of effectiveness and robustness. Numerical results suggest that the empirical linear model and Scanlan's nonlinear model significantly underestimate the TMD mass ratio required to suppress the VIV amplitude to be lower than a threshold. The empirical linear model may overestimate the robustness of the TMD to changing the frequency ratio, while Scanlan's nonlinear model may overestimate or underestimate the robustness depending on the threshold VIV amplitude. The TMD design based on the polynomial model is considered more accurate since it can accurately predict VIV responses at various effective damping levels. The aerodynamic envelope model can be used as a convenient model for TMD optimization. The results generated using the free vibration formula are the closest to that of the polynomial model. An appropriate safety factor should be considered to convert the TMD design based on sectional model experiments to real bridges. [ABSTRACT FROM AUTHOR]

The empirical envelope (EE) method based on the amplitude-modulation and frequency-modulation (AMFM) decomposition is effective for identifying the modal parameters of time-varying and weakly nonlinear systems. However, the identification accuracy of the EE method is sensitive to noises which often exist in vibration measurements of real structures. In this study, an improved empirical envelope (IEE) method is proposed to achieve robust modal parameter identification from noisy measurements. Specifically, the idea of sliding window threshold denoising is introduced to reduce the error in the instantaneous envelope induced by abnormal extreme points, and a moving average filter is utilized to reduce the error in the instantaneous frequency induced by high-frequency noises. Two numerical examples and an experimental example of a full-bridge aeroelastic model are analyzed to validate the accuracy of the IEE method and highlight the superiority of the IEE method relative to the original EE method. It is concluded that the IEE method is robust to measurement noises (the considered signal-to-noise ratios include 5–90 dB) and that the IEE method is more accurate than the EE method. Hence, the IEE method serves as a promising alternative for modal parameter identification of time-varying and weakly nonlinear systems. [ABSTRACT FROM AUTHOR]

Applying a subpixel refinement technique in vision‐based displacement sensing can significantly improve the measurement accuracy. However, digital image signals from the camera are highly sensitive to drastically varying lighting conditions in the field measurements of structural displacement, causing pixels expressing a tracking target to have nonuniform grayscale intensity changes in different recording video frames. Traditional feature points‐based subpixel refinement techniques are neither robust nor accurate enough in this case, presenting challenges for accurate measurement. This paper proposes a robust subpixel refinement technique—self‐adaptive edge points matching (SEPM)—to obtain accurate subpixel‐level displacements under drastic illumination change conditions. Different from traditional feature points‐based methods, the gradient and shape information of the target edge contour are used in the SEPM calculation. Three tests under different illumination conditions were conducted to evaluate the performance of the SEPM. The results show that the SEPM is capable of producing accurate subpixel‐level displacement data with less 1/16‐pixel root mean‐square error. [ABSTRACT FROM AUTHOR]

Wind-resistant performance is a major concern in the design and operation of pipeline suspension bridges. The mean aerodynamic force coefficients (MAFCs) are essential parameters for quantifying the wind loads on a bridge. However, a systematic investigation of the MAFCs of typical pipeline suspension bridge girders is unavailable. Specifically, the effects of design parameters (perforation rate of grate plates, horizontal spacing between pipelines, vertical spacing between pipelines, pipeline number, pipeline diameter, and pipeline surface roughness) and Reynolds number on MAFCs remain to be investigated. This study systematically investigated the MAFCs of three typical pipeline suspension bridge girders in wind tunnel experiments. The galloping stabilities of these girders were examined based on the quasi-steady galloping theory. The experimental results show that the effect of pipeline surface roughness on the Reynolds number effect of drag force coefficient is similar to that on the Reynolds number effect of a circular cylinder. Closing the grate plates may deteriorate the galloping performance of a bridge girder, whereas increasing the pipeline surface roughness may strengthen the galloping performance of a bridge girder. Unlike parallel circular cylinders, the horizontal spacing between pipelines slightly affects the MAFCs. Optimizing the vertical spacing between the pipelines can significantly reduce the MAFCs. In addition, optimizing the shape and roughness of the pipeline can reduce the lift force and pitching moment, and optimizing the shape of guardrails and truss stiffening girder can reduce the drag force. These research results can provide a basis for quantifying the aerodynamic loads and a reference for the wind-resistant design of pipeline suspension bridges with similar bridge girders. [ABSTRACT FROM AUTHOR]

Under strong wind actions, some long-span flexible deck bridges have been observed to exhibit significant lateral vibrations. Accurate quantification of the self-excited forces induced by lateral vibration is of great significance for the evaluation of the wind-resistant performance of bridges. Three typical deck sections, including a 5:1 rectangular section, a streamlined section, and a central-slotted section, are used to comprehensively address this issue using the unsteady Reynolds-averaged Navier–Stokes simulations. The applicability of the linear analysis method for quantifying the self-excited forces is reexamined for different lateral vibration amplitudes and reduced wind speeds. The results show that the self-excited drag force induced by lateral vibration agrees well with the linear theory for the three sections. However, the self-excited lift force and torsional moment induced by lateral vibration cannot be quantified by the linear formulations. For the rectangular section, the self-excited lift force and torsional moments are much smaller than the vortex-induced counterparts. For the streamlined and central-slotted sections, the ratios of the self-excited components to the vortex-induced components are closely related to the reduced wind speed and vibration amplitude. The ratios increase with an increase in vibration amplitude and a decrease in reduced wind speed. Thus, particular attention should be paid to the self-excited lift force and torsional moment induced by lateral motions for bridge decks. [ABSTRACT FROM AUTHOR]