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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]

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]

The wind–rain-resistant performances of aeroelastic models of simplified suspension bridges and cable-stayed bridges at the erection stage are experimentally investigated. Several typical deck sections, i.e., two bluff decks, two thin flat plates, and a quasi-streamlined deck, are included to cover a wide range of possible alternatives. Under different conditions of wind speed, rainfall intensity, and initial attack angle, the vertical and torsional displacements at the deck end tips and middle sections are measured. The comprehensive measurement results reveal that in the possible and even extreme range of rainfall intensity, the aerostatic and aerodynamic responses are almost independent of the rainfall intensity for all testing cases, which may contradict with the intrinsic conception of most researchers in the wind engineering community. The results suggest that the rainfall loads effect on bridges are trivial, and it might be unnecessary to comprehensively investigate the rainfall loads on bridges similar with the considered cases. [ABSTRACT FROM AUTHOR]

Ice accretion is a major concern that may endanger the operation safety of structures and even cause serious casualties in cold regions. Under freezing rain conditions, the size and shape of the accreted ice on different diameter circular cylinders are investigated in a refrigerated precipitation icing laboratory. The ice size and shape are closely related to cylinder diameter and accretion duration. The engineering geometrical models of the ice accretion on circular cylinders are extracted. The aerodynamic displacement responses of a 1:25 aeroelastic model of a pipeline suspension bridge with and without ice accretions are experimentally recorded using Micro-Epsilon sensors. Analytical expressions to calculate the vertical and lateral displacements are derived, and the differences between the conventional method and the newly derived one are further analyzed to manifest the theoretical significance. For three-degrees-of-freedom motions, the vertical and lateral displacements cannot be separately determined by the signals of vertical and lateral sensors, respectively. Some strategies are recommended to reduce the errors induced by using the conventional formulations. The influences of initial angle of attack, ice shape, pipeline diameter, and turbulence intensity on girder displacement and wind cable tensile force are comprehensively investigated. The aerostatic responses are greatly influenced by the aforementioned parameters. The aerodynamic analyses reveal that the ice accretion can obviously increase wind-induced responses, that is, deteriorate the wind-resistant performance, which should be taken into careful consideration. The present work can provide beneficial references for the wind-resistant design of similar type of bridges, especially under pipeline ice accretion conditions. [ABSTRACT FROM AUTHOR]

• Experimental investigation of aerodynamic performance of pipeline suspension bridge. • Derive the analytical expressions of three-degree-of-freedom motion displacements. • Effects of wind angle of attack, turbulence intensity, pipeline diameter and number. The aerodynamic stability performance of a long-span pipeline suspension bridge is studied based on a 1: 25 full-bridge aeroelastic model using wind tunnel tests. The influences of initial angle of attack, pipeline diameter, pipeline number, and turbulence intensity on the aerostatic and buffeting displacements of the girder, and on the wind cable tensile forces are comprehensively investigated. The aerodynamic displacements of the girder along the span were measured by using a video gauge. Analytical expressions are derived to construct the displacements of three-degree-of-freedom motions from the recorded signals, and the differences between the derived formulas and the conventional ones are demonstrated. Recommendations are offered to reduce or even eliminate the potential errors of the convenient habitual formulas. The testing results show that the aerodynamic displacements and wind cable tensile forces of the bridge may depend remarkably on the initial angle of attack, pipeline diameter, pipeline number, and turbulence intensity. Research results of the present work can provide beneficial references for evaluating the wind-resistant performances of bridges of the similar type. [ABSTRACT FROM AUTHOR]

This paper studies the flutter performances of a streamlined bridge deck sectional model using a recently developed testing device for large-amplitude free vibration test. The reported torsional vibration amplitude of the sectional model exceeds 15°, and higher vibration amplitudes can be achieved if desired. The flutter performances at various initial angles of attack α 0 , the hysteresis behavior, and the energy budget property of the flutter response are analyzed. Experimental results show that the sectional model exhibits divergent vibrations right after the critical flutter velocities for α 0 = 0°, −3°, and −5°, while it performs limit cycle oscillations (LCO) after the critical flutter velocities for α 0 = +3° and +5°. Hysteresis phenomena are observed for all tested angles of attack. Both the critical flutter velocity and the vibration amplitudes around the critical velocity may be affected by the initial impulse excitation exerted on the bridge deck. The vertical-to-torsional amplitude ratio decreases with increasing the vibration amplitude for a coupled LCO, while the opposite rule is observed for a divergent vibration. The energy dissipated by the mechanical damping accumulates continuously while the total mechanical energy varies non-monotonously with increasing time. This study is expected to deepen the understanding of the flutter responses of a bridge deck in the presence of nonlinear aerodynamic effects. The experimental results can also serve as a database for validating computational fluid dynamics procedures and nonlinear self-excited force models. • Flutter performance of a bridge deck were studied using a recently developed device for large-amplitude free vibration test. • Torsional vibration amplitude of the model exceeded 15°, and higher amplitudes can be achieved if desired. • Hysteresis phenomena were observed for all tested angles of attack. • Critical velocity and vibration amplitudes around critical velocity may be affected by the initial excitation. [ABSTRACT FROM AUTHOR]

The aerodynamic characteristics of a circular cylinder (diameter ​= ​600 ​mm) with and without ice accretion (without icicles) were studied via wind tunnel tests (including simultaneous multi-pressure and force measurements) for Reynolds numbers (Re) of 1.29 ​× ​105–1.27 ​× ​106. The influences of wind angle of attack α , turbulence intensity I u , relative surface roughness k , and accreted ice shape on the mean aerodynamic force coefficients (MAFCs), mean pressure coefficients, and pressure correlation coefficients were comprehensively investigated. Experimental results showed that the MAFCs of the ice-accreted cylinders exhibited significant Reynolds number effects, and the effects were closely related to the ice shape. The effects of I u and k on the drag force of the ice-accreted and ice-free cylinders were similar. The remarkable lift force due to the asymmetric ice accretion could be reduced by increasing k and I u. The effect of α on the MAFCs was related to the ice shapes and Re. The flow reattachments in the critical and supercritical regimes were examined to reveal the flow states around the finite ice-free and ice-accreted cylinders. The flow-fields around the finite ice-free and ice-accreted cylinders had significant three-dimensional effects, which could be weakened by introducing the I u and k. The findings of this study could provide further understanding of the effect of ice accretion on the aerodynamic characteristics of circular cylinders. The results could be used as beneficial references in the wind-resistance design of ice-accreted circular cylinders. • Aerodynamic characteristics of a large-diameter ice-accreted circular cylinder were studied for Re ​= ​1.29 ​× ​105–1.27 ​× ​106. • Influences of the wind angle of attack, turbulence intensity, surface roughness, and accreted ice shape were investigated. • Findings of the study provide further understanding of the effect of ice on aerodynamic characteristic of circular cylinder. [ABSTRACT FROM AUTHOR]

The characteristics of vortex-induced vibration (VIV) of a rectangular 4:1 cylinder are comprehensively investigated under different wind yaw angles (β = 0°, 5°, 10°, 15°, 20°, 25°, and 30°) and wind angles of attack (α m = +5°, +3°, and 0°) using wind tunnel tests. For the VIVs of a rectangular 4:1 cylinder, the lock-in regions, amplitudes, frequencies, hysteresis effects, and the applicabilities of independence principle (IP) for various cases are analyzed. Experimental results suggest that the maximum VIV amplitude and the onset wind speed for VIV respectively decreases and increases with increasing β. Hence, it is reasonable to assume that the most unfavorable state of VIV occurs for β = 0° for the rectangular 4:1 cylinder. However, the IP theory is inapplicable for predicting its VIV responses under skew winds. The maximum amplitude increases with the increase of α m , while the lock-in region shrinks with α m. For the rectangular 4:1 cylinder under skew winds, the experimental VIV response may provide a benchmark for checking the prediction accuracies of mathematical models and computational fluid dynamic simulations. • Wind tunnel test is conducted for a 4:1 rectangular cylinder under skew winds. • A new spring-suspended sectional model system is proposed for skew wind test. • The applicability of independence principle (IP) is systematically analyzed. • The experimental study may provide a benchmark for future numerical studies. [ABSTRACT FROM AUTHOR]