An experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges

Abstract

This invention discloses an experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges, belonging to the field of marine civil engineering safety technology. It includes a bridge segment model, a frame with crossbeams on both sides, three different types of clamping devices, a wind-wave coupling field generation device, an aerodynamic load measurement device, an accelerometer, and a wind speed measurement device. This invention is used for wind-wave combined tests. With the help of three sets of clamping devices, it can separately realize the measurement of the aerodynamic three-component force coefficients of the bridge segment model, and conduct forced vertical bending vibration and forced torsional vibration tests. A pressure scanning valve system is used to collect the pressure distribution on the bridge segment model. This invention can efficiently obtain the aerodynamic three-component force coefficients and flutter derivatives of the bridge segment model in wind-wave combined tests, and analyze the influence of wave boundaries on the aerodynamic performance of the segment model. Compared with traditional experimental methods, this invention can achieve forced vibration of the model using a relatively small experimental device, and also has the function of static and dynamic testing of the bridge segment model. This invention has the dual advantages of high efficiency and economy.

Description

Technical Field

[0001] This invention belongs to the field of marine civil engineering safety technology, specifically involving an experimental system for studying the influence of wind and wave coupling on the aerodynamic characteristics of bridges. Background Technology

[0002] Compared to traditional land-based bridges, cross-sea bridges face more complex environments at their sites, often encountering the combined effects of strong winds, giant waves, currents, tsunamis, and earthquakes. Research indicates that the coupling effects of multiple natural disasters often place marine structures in a more precarious state. Wind and waves are the most significant external loads on cross-sea bridges during their service life. During typhoons, rising sea levels and reduced bridge clearance enhance the coupling effect between extreme waves and the wind field surrounding the bridge, significantly impacting its aerodynamic loads. Therefore, studying the aerodynamic load characteristics of cross-sea bridges under the combined effects of wind and waves is crucial. Investigating the influence mechanism of the bottom wave boundary on the aerodynamic force coefficients and flutter derivatives of bridge segment models is fundamental to analyzing bridge aerodynamic loads.

[0003] Because the environment in which cross-sea bridges operate involves significant multi-field coupling, the coupling effect between wind and wave fields needs to be considered when analyzing their aerodynamic loads. Traditional methods often neglect the influence of the bottom wave boundary on the wind field. Whether using wind tunnel tests with bridge segment models or CFD numerical simulations, the wave boundary is usually simplified to a plane, which limits the application of existing research conclusions to cross-sea bridges. Summary of the Invention

[0004] Based on the above shortcomings, this invention provides an experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges. This system addresses the problem that traditional analyses of the aerodynamic load characteristics of cross-sea bridges often directly ignore the influence of the bottom wave boundary on the wind field, resulting in limitations when applying existing research conclusions to cross-sea bridges.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: an experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges, comprising a bridge segment model, a frame with crossbeams on both sides, three different types of clamping devices, a wind-wave coupling field generation device, an aerodynamic load measurement device, an acceleration sensor, and a wind speed measurement device.

[0006] The wind-wave coupling field generation device includes a recirculating or direct-flow wind tunnel, a rocking or pushing wave generator, and a water tank. This device generates wind-driven and wave fields. The wind speed in the test section is adjusted by controlling the fan speed using the recirculating or direct-flow wind tunnel, and the turbulence intensity of the generated wind field is adjusted by adding rough elements and wedges. The rocking or pushing wave generator generates the required regular and irregular waves by controlling its input hydrodynamic parameters. In the experiment, the fan is started first, and after the wind field in the test section stabilizes, the wave generator is activated to generate regular or irregular waves. The wave field generated by the wave generator is superimposed with the wind-generated wave field before the experiment begins. During the experiment, the wave-damping section at the tail of the water tank and the active wave-damping method of the wave generator reduce the influence of reflected waves on the test results. Three different types of clamping devices are used to clamp the bridge segment model onto the frame for three-component force coefficient tests, torsional forced vibration tests, and vertical bending forced vibration tests, thereby completing the measurement of the aerodynamic three-component force coefficients and flutter derivatives of the bridge segment model.

[0007] Accelerometers are installed on the bridge segment model to acquire forced vibration data. A wind speed measuring device is positioned in front of the bridge segment model to acquire incoming wind speed data. The aerodynamic load measuring device uses a pressure scanning valve to acquire pressure distribution on the bridge segment model under different wave phases. The bridge segment model is hollow and has ribs installed inside. Multiple pressure measuring holes are opened along the spanwise centerline on the upper and lower surfaces of the bridge segment model to set the measuring points of the pressure scanning valve. End plates are provided on the left and right sides of the bridge segment model to ensure the stability of the wind field where the bridge segment model is located.

[0008] Furthermore, the clamping device used in the aerodynamic force coefficient test includes a high-precision rotary slide, two sets of vertical connectors, two sets of U-shaped conversion joints, and a locking device. The two ends of the spanwise direction of the bridge segment model are connected to the high-precision rotary slide through U-shaped conversion joints. The two sides of the high-precision rotary slide are fixedly connected to the two side beams of the frame through vertical connectors. The wind attack angle of the bridge segment model is precisely controlled by adjusting the angle of the high-precision rotary slide. After positioning, the high-precision rotary slide is fixed by the locking device.

[0009] Furthermore, the clamping device used in the torsional forced vibration test includes two sets of crank-rocker mechanisms, two sets of vertical connectors, and two sets of U-shaped conversion joints with extended tail sections. The two ends of the spanwise direction of the bridge segment model are connected to the U-shaped conversion joints with extended tail sections. Each set of U-shaped conversion joints with extended tail sections is rotatably connected to a set of vertical connectors. The two sets of vertical connectors are fixedly connected to the two side beams of the frame. The extended tail section of each set of U-shaped conversion joints with extended tail sections is rotatably connected to the actuating end of a set of crank-rocker mechanisms. The fixed sections of the two sets of crank-rocker mechanisms are fixedly connected to the two side beams of the frame and located behind the vertical connectors. The two sets of crank-rocker mechanisms need to operate synchronously to avoid torsion of the bridge segment model.

[0010] Furthermore, the clamping device used in the vertical bending forced vibration test includes two sets of crank-rocker mechanisms and two sets of U-shaped adapter joints. The two ends of the spanwise direction of the bridge segment model are fixedly connected to the moving ends of the two sets of crank-rocker mechanisms through U-shaped adapter joints. The outer shells of the two sets of crank-rocker mechanisms are fixedly connected to the crossbeams on both sides of the frame. The vertical bending forced vibration of the bridge segment model is realized through the crank-rocker mechanism. The two sets of crank-rocker mechanisms need to operate synchronously to avoid the torsion of the bridge segment model.

[0011] This invention also provides an experimental method for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges, based on the experimental system described above, as follows: a pressure scanning valve collects pressure data acting on a bridge segment model in real time; the collected pressure data is integrated to obtain the aerodynamic force acting on the bridge segment model, calculated using the following formula:

[0012]

[0013]

[0014]

[0015] In the formula: F L (α),F D M(α) and M(α) represent the lift, drag, and lift moment experienced by the bridge segment model, respectively; P i Let be the pressure at the i-th measuring point; Δl be the distance between adjacent measuring points; α be the wind attack angle of the bridge segment model; and L be the spanwise length of the bridge segment model.

[0016] After obtaining the lift, drag, and lift moment data of the model through integration, the three force coefficients of the bridge segment model are calculated using the following formula:

[0017]

[0018]

[0019]

[0020] In the formula: C L (α),C D (α),C M (α) represents the lift coefficient, drag coefficient, and lift moment coefficient of the bridge segment model, respectively; U is the incoming wind speed directly in front of the bridge segment model; B is the width of the bridge segment model; and D is the height of the bridge segment model. Based on aerodynamic forces, forced vibration data of the bridge segment model, and incoming wind speed data, the flutter derivative of the bridge segment model can be obtained.

[0021] Further, as described above, wave height meters are placed at the front, middle, and rear of the bridge segment model to monitor the wave surface time history at the bridge segment model. By studying the relationship between wave elements and aerodynamic three-component force coefficients and flutter derivatives, the influence mode of the bottom wave boundary on aerodynamic load characteristics is obtained. Based on the pressure distribution characteristics under different wave phases, the mechanism of the wave boundary on aerodynamic load characteristics under the combined action of wind and waves is further derived.

[0022] This invention offers the following advantages and benefits: First, by utilizing three different clamping devices, it enables the measurement of aerodynamic force coefficients and flutter derivatives of bridge segment models in combined wind and wave tests. It also considers the influence of the bottom wave boundary on the aerodynamic load characteristics of the bridge segment model, effectively solving this problem. Second, by acquiring the pressure distribution of the bridge segment model through a pressure scanning valve, and based on the phase relationship between aerodynamic loads and waves, it obtains pressure distribution patterns under the influence of different wave elements, more intuitively revealing the mechanism by which wave boundaries affect the aerodynamic force coefficients and flutter derivatives. Third, this invention meets the requirements for use in small combined wind and wave tanks, significantly reducing the equipment requirements for related tests. Fourth, the design of this invention focuses on the blocking effect on wind and wave fields, minimizing the windward and wave-facing areas of the components in the device. The load measurement method also selects a pressure measurement method that causes less interference with the wind field. These features of the device are particularly advantageous when used in small-scale laboratories. Fifth, this invention can accommodate both combined wind and wave tests and traditional wind tunnel tests, greatly expanding the application scenarios and improving the applicability of the device. Attached Figure Description

[0023] Figure 1 This is a front view of an experimental system according to the present invention for studying the influence of wind-wave coupling on the aerodynamic load characteristics of a bridge segment model;

[0024] Figure 2 Front view of the aerodynamic force coefficient measuring device for a bridge segment model;

[0025] Figure 3 A cross-sectional view of the aerodynamic force coefficient measuring device for a bridge segment model (AA plane).

[0026] Figure 4 A cross-sectional view of the BB plane of the aerodynamic force coefficient measuring device for a bridge segment model;

[0027] Figure 5 This is a front view of the torsional forced vibration device for a bridge segment model.

[0028] Figure 6 A cross-sectional view of the torsional forced vibration device on the bridge segment model (AA plane).

[0029] Figure 7 This is a sectional view of the BB plane of the torsional forced vibration device for a bridge segment model.

[0030] Figure 8 This is a front view of the vertical bending forced vibration device for a bridge segment model.

[0031] Figure 9 A sectional view of the vertical bending forced vibration device for a bridge segment model (AA plane).

[0032] Figure 10 A BB section view of the vertical bending forced vibration device for a bridge segment model;

[0033] Figure 11 Detailed drawings of the aerodynamic force coefficients of the bridge segment model and the conversion joint of the vertical bending forced vibration device;

[0034] Figure 12 This is a top view of a bridge segment model;

[0035] Figure 13 This is a side view of a bridge segment model;

[0036] Figure 14 This is an example image showing the results of data processing.

[0037] In the diagram: 1-Frame vertical rod; 2-Frame horizontal rod; 3-Horizontal beam; 4-Vertical connector; 5-High-precision rotary slide; 6-U-shaped adapter; 7-Bearing; 8-Forced vibration module, composed of a stepper motor and crank rocker mechanism; 9-Bridge segment model; 10-Model end plate; 11-Bridge segment model fixing shaft; 12-Pressure measuring hole; 13-Fan; 14-Wave generator; 15-Anemometer; 16-Wave height meter; 17-Wave damping section. Detailed Implementation

[0038] The present invention will now be clearly and completely described with reference to the accompanying drawings. Example 1

[0039] An experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges includes a bridge segment model, a frame with crossbeams on both sides, three different types of clamping devices, a wind-wave coupling field generation device, an aerodynamic load measurement device, an acceleration sensor, and a wind speed measurement device, as detailed below:

[0040] 1. Experimental apparatus for generating wind-wave coupled field:

[0041] The wind-wave coupling field generation device includes a recirculating or direct-flow wind tunnel, a rocking or pushing wave generator, and a water tank. The generation of the wind-wave coupling field involves the generation of wind and wave fields. In the experiment, the wind speed of the model test section is adjusted by controlling the fan speed in the recirculating or direct-flow wind tunnel, and the turbulence intensity of the generated wind field is adjusted by adding rough elements and wedges. The rocking or pushing wave generator generates the required regular and irregular waves by controlling its input hydrodynamic parameters. Taking a small-scale wind-wave combined test device with a direct-flow wind tunnel installed on the top of the wave tank as an example, the fan is started first. After the wind field in the test section stabilizes, the wave generator is turned on to generate regular or irregular waves. The wave field generated by the wave generator is superimposed with the wind-generated wave field before the experiment begins. In the experiment, the wave-damping section at the tail of the water tank and the active wave-damping method of the wave generator are used to reduce the influence of reflected waves on the test results.

[0042] 2. Frame with crossbeams on both sides

[0043] The frame is a cube-shaped structure welded from twelve rectangular steel pipes. To reduce the impact of the frame on the test wind and wave fields, the steel pipes on the windward and wave-facing sides of the frame are designed with narrow sides. Long holes are opened in the top steel pipes of the frame, and the frame is securely connected to the top plate of the DC wind tunnel by bolts. Circular through holes are opened at different locations on the vertical steel pipes of the frame. The main function of these through holes is to fix the frame to the crossbeams via bolts. The crossbeams are made of the same material as the frame, and only the wide side of the rectangular cross-section is retained at the ends, with circular bolt holes on the wide side. These bolt holes are used to connect to the vertical members of the frame. This end treatment effectively reduces the windward and wave-facing area of ​​the frame, thereby reducing its impact on the wind and wave fields. Circular bolt holes are evenly distributed on the crossbeams, mainly for connecting vertical connectors and forced vibration modules. Multiple circular bolt holes are arranged on the upper part of the vertical connectors for connecting to the crossbeams. The clearance height of the bridge segment model can be easily adjusted by adjusting the position of these fixing holes. In addition, a thin steel plate with bolt holes is welded to the lower part of the vertical connectors.

[0044] 3. Three sets of clamping devices:

[0045] The U-shaped adapter is mainly used to connect the clamping device and the bridge segment model. It is made of U-shaped aluminum channel. The bottom of the U-shaped adapter has two pairs of bolt holes. One set of bolt holes is used for clamping device, and the other set of bolt holes is used to connect the fixed shaft of the bridge segment model. The form of the U-shaped adapter is slightly different for three sets of clamping devices.

[0046] The clamping device used in the aerodynamic force coefficient test includes a high-precision rotary slide, two sets of vertical connectors, two sets of U-shaped adapters, and a locking device. The high-precision rotary slide provides precise and controllable angular positioning for the model. The two ends of the spanwise direction of the bridge segment model are connected to the high-precision rotary slide through U-shaped adapters. The two sides of the high-precision rotary slide are fixedly connected to the two side beams of the frame through vertical connectors. The wind attack angle of the bridge segment model is precisely controlled by adjusting the angle of the high-precision rotary slide. After positioning, the high-precision rotary slide is fixed by the locking device to ensure the stability of the high-precision rotary slide during the test.

[0047] The clamping device used in the torsional forced vibration test includes two sets of crank-rocker mechanisms, two sets of vertical connectors, and two sets of U-shaped transition joints with extended tail sections. The two ends of the spanwise direction of the bridge segment model are connected to the U-shaped transition joints with extended tail sections. Each set of U-shaped transition joints with extended tail sections is rotatably connected to a set of vertical connectors via bearings. The two sets of vertical connectors are fixedly connected to the crossbeams on both sides of the frame. The extended tail section of each set of U-shaped transition joints with extended tail sections is rotatably connected to the moving end of a set of crank-rocker mechanisms via bearings. The fixed sections of the two sets of crank-rocker mechanisms are fixedly connected to the crossbeams on both sides of the frame and located behind the vertical connectors. The two sets of crank-rocker mechanisms need to operate synchronously to prevent the bridge segment model from twisting. The two sets of crank-rocker mechanisms are driven by two stepper motors respectively. The rotation of the stepper motors is converted into the vertical motion of the connecting rods through the crank-rocker mechanisms. The main advantage of choosing stepper motors is that once the initial position of the bridge segment model is determined, the two motors can run synchronously thereafter, thereby avoiding the lateral torsion of the model caused by the phase difference between the two motors. The cranks of the stepper motors have four different threaded holes with different center distances, which are used to adjust the position of the rocker to achieve different vibration amplitudes. The vibration frequency of the forced vibration module is achieved by controlling the speed of the stepper motors.

[0048] The clamping device used in the vertical bending forced vibration test includes two sets of crank-rocker mechanisms and two sets of U-shaped adapter joints. The two ends of the spanwise direction of the bridge segment model are fixedly connected to the moving ends of the two sets of crank-rocker mechanisms via U-shaped adapter joints. The outer shells of the two sets of crank-rocker mechanisms are fixedly connected to the crossbeams on both sides of the frame. The vertical bending forced vibration of the bridge segment model is achieved through the crank-rocker mechanisms. The two sets of crank-rocker mechanisms need to operate synchronously to avoid torsion of the bridge segment model.

[0049] 4. Pneumatic load measuring device:

[0050] To obtain the aerodynamic load characteristics of the bridge segment model, a pressure scanning valve device was selected for the aerodynamic load measurement in the experiment. The advantage of choosing this device is its ability to obtain the pressure distribution on the bridge segment model under different wave phases, allowing for in-depth analysis of the influence mechanism of the bottom wave boundary on the flutter derivative of the bridge segment model. To accommodate the requirements of the pressure scanning valve, the bridge segment model was processed as follows:

[0051] In the experiment, the bridge segment model was fabricated using 3D printing technology. The model is divided into three parts: left, middle, and right. The left and right parts are symmetrical, and their interiors are hollowed out during the 3D printing process. To ensure the stability and rigidity of the segment model, a number of ribs were added inside. This approach effectively reduces the model's weight, alleviating the load on the high-precision rotary slide connected to the model's ends. Furthermore, this internal space facilitates the placement of the pressure measuring hose for the pressure scanning valve. The middle part of the model is solidly printed using 3D printing technology, but pressure measuring holes with a spacing of 1 cm and a diameter of 1 mm are pre-drilled around its centerline. To facilitate the placement of the pressure scanning valve's measuring points, the pressure measuring hose transmits pressure through the pre-drilled holes in the left and right parts of the model. This design is primarily to allow for the successful placement of the pressure measuring holes in the middle of the bridge segment model. Secondly, end plates are added to both sides of the bridge segment model. These end plates are made of plexiglass, ensuring that their length is at least 1.5 times the width of the bridge segment model and their height is at least 3 times the height of the bridge segment model. The main function of the end plates is to provide a clear boundary, ensuring that wind cannot enter or leave from the sides of the model, thus better guaranteeing the stability of the wind field in which the bridge segment model is located. Finally, during the 3D printing process, through holes are made at 1 / 3 and 2 / 3 of the width on both sides of the entire bridge segment model to allow long threaded rods made of stainless steel to pass through. On the one hand, the threaded rods connect and fix the three parts of the bridge segment model, providing them with a certain degree of rigidity support; on the other hand, the part of the threaded rod extending out of the bridge segment model will connect to the threaded holes reserved on the U-shaped adapter, connecting the bridge segment model to the clamping device.

[0052] Meanwhile, accelerometers were installed on the bridge segment model to acquire forced vibration data; wind speed measuring equipment was placed in front of the model to acquire incoming wind speed data; based on aerodynamic forces, forced vibration data, and incoming wind speed data, the flutter derivative of the bridge segment model can be obtained. Wave height meters were placed at the front, middle, and rear of the bridge segment model to monitor the wave surface time history at the model. By studying the relationship between wave elements, aerodynamic force coefficients, and flutter derivative, the influence mode of the bottom wave boundary on aerodynamic load characteristics can be explored in depth; based on the pressure distribution characteristics under different wave phases, the mechanism of wave boundary action on aerodynamic load characteristics under the combined action of wind and waves is further revealed.

[0053] Example 2

[0054] Measurement test of aerodynamic force coefficients of bridge segment model under combined wind and wave action:

[0055] refer to Figure 1 Before the formal test begins, the wind and wave fields required for the test need to be calibrated. The wind-wave coupled field generation experimental device consists of a wind field generated by a programmable fan located at the front of the flume and input into the test system. The wind environment characteristics at the target bridge site are realized by adjusting the fan speed. The wave field is generated by a programmable pusher wave generator at the front of the flume and input into the test system. The complex wave conditions of the target bridge site area are realized by adjusting the wave input parameters. During the calibration test, micro-pressure sensors and wave height meters are used in the wind-wave coupled flume to collect parameters such as wind speed and wave height at the installation location of the bridge segment model. After the wave field calibration is completed, the assembled bridge segment model adjustment device is installed in the combined wave flume. Wave height meters are placed at the front, middle, and rear of the bridge segment model to monitor the elevation changes of the liquid level during the test. A micro-pressure sensor is placed directly in front of the bridge segment model to monitor the wind speed in the direction of the incoming flow, and to analyze the influence of the bottom wave boundary on the upper wind field. At the start of the test, the programmable fan is activated. After the wind field of the target test section stabilizes, the programmable pusher wave generator is activated to generate regular or irregular waves. The wave-damping section at the tail of the flume and the active wave-damping method of the wave generator reduce the influence of reflected waves on the test results. Pressure time history data of the middle part of the bridge segment model is collected using a pressure scanning valve device. The aerodynamic force acting on the bridge segment model is obtained by integrating the obtained pressure time history data. The calculation formula is as follows:

[0056]

[0057]

[0058]

[0059] In the formula: F L (α),FD M(α) and M(α) represent the lift, drag, and lift moment experienced by the bridge segment model, respectively; P i Let be the pressure at the i-th measuring point; Δl be the distance between adjacent measuring points; α be the wind attack angle of the bridge segment model; and L be the spanwise length of the bridge segment model.

[0060] After obtaining the lift, drag, and lift moment data of the model through integration, the three force coefficients of the bridge segment model are calculated using the following formula:

[0061]

[0062]

[0063]

[0064] In the formula: C L (α),C D (α),C M (α) represents the lift coefficient, drag coefficient, and lift moment coefficient of the bridge segment model, respectively; U is the incoming wind speed directly in front of the bridge segment model; B is the width of the bridge segment model; and D is the height of the bridge segment model.

[0065] In this embodiment, the wind attack angle of the bridge segment model is adjusted by coarse adjustment of the high-precision rotary slide coarse adjustment clamp, fine adjustment of the high-precision rotary slide micrometer knob, and finally fixing of the opposing clamp to ensure the stability of the bridge segment model during the test.

[0066] In this embodiment, by analyzing the phase relationship between the wave surface time history measured by the wave height meter and the time history of the integral three-component force coefficients, the influence of wind-wave coupling on the aerodynamic three-component force coefficients of the bridge segment model can be obtained. Simultaneously, by analyzing the pressure distribution of the bridge segment model at different wave phases, the influence mechanism of the bottom wave boundary on its aerodynamic three-component force coefficients can be further analyzed. Figure 14 The figure shows the pressure distribution of the thin plate model under wind and wave coupling when the aerodynamic lift coefficient is at its minimum, average and maximum. The test results are given under two different wind attack angles.

[0067] Example 3

[0068] Torsional forced vibration test of bridge segment model under combined wind and wave action:

[0069] Clamping device reference Figure 5 , Figure 6 and Figure 7The main difference between the vertical bending forced vibration test and the aerodynamic three-part force coefficient measurement test in this embodiment lies in the clamping device. The installation of the main frame of the device and the bridge segment model will not be described in detail in this embodiment. Bolts are used to connect the bolt holes on the upper half of the vertical connecting piece 4 to the bolt holes at the center of the crossbeam 3. The thin steel plate welded to the lower half of the vertical connecting piece 4 is bolted to the bolt holes on the outer ring of the bearing 7. A small shim is added between the thin steel plate and the outer ring of the bearing to prevent friction between the inner ring of the bearing and the thin steel plate, which would affect the smoothness of the forced vibration during the test. The inner ring of the bearing 7 is bolted to the bolt holes on the U-shaped adapter 6. A small shim is added between the U-shaped adapter 6 and the inner ring of the bearing to prevent friction between the outer ring of the bearing and the U-shaped adapter 6. The forced vibration module 8 is bolted to the bolt holes at one end of the crossbeam 3. It should be noted that after the connecting rod of the forced vibration device is installed, it should be parallel to the vertical connecting piece 4. The tail of the connecting rod passes through the bolt holes on the U-shaped adapter 6 and is fixed with anti-slip nuts. At this point, the main frame and clamping device of the torsional forced vibration device are assembled.

[0070] Connect the assembled bridge segment model to the clamping device via U-shaped adapter 6. When installing the bridge segment model, ensure that the model is within the target clearance when the crank rocker mechanism is in the centerline position. Connect and fix the assembled bridge segment model torsion forced vibration device to the wind and wave combined water tank.

[0071] After the wind and wave field calibration was completed, a torsional forced vibration device and a bridge segment model were installed. Accelerometers were installed on the bridge segment model to acquire forced vibration data. A wind speed measuring device was placed in front of the model to acquire incoming wind speed data. Wave height meters were placed at the front, middle, and rear of the bridge segment model to monitor wave surface time histories. At the start of the experiment, the wind turbine was started, and after the wind field in the test section stabilized, the wave generator was activated to generate the calibrated waves. During the experiment, a pressure scanning valve was used to collect pressure time history data from the middle of the bridge segment model, and aerodynamic time history data was obtained through pressure integration. Based on the aerodynamic time history, motion time history, and incoming wind speed data of the bridge segment model, the flutter derivative of the bridge segment model can be calculated. Simultaneously, analyzing the relationship between wave elements and the flutter derivative allows for a deeper exploration of the influence mode of the bottom wave boundary on the flutter derivative. Based on the pressure distribution characteristics under different wave phases, the mechanism of the wave boundary's effect on the flutter derivative under the combined action of wind and waves is further revealed.

[0072] In this embodiment, torsional motion with different rotation angle amplitudes is achieved by adjusting the fixed positions of the crank and rocker in the forced vibration module. This module provides four rotation angle amplitudes to choose from. Different vibration frequencies are achieved by adjusting the speed of the stepper motor.

[0073] Example 4

[0074] Forced vertical bending vibration test of bridge segment model under combined wind and wave action:

[0075] Clamping device reference Figure 8 , Figure 9 and Figure 10 The installation process differs between the clamping devices used for vertical bending forced vibration tests and torsional forced vibration tests. In this embodiment, the installation of the main frame of the device and the bridge segment model will not be described in detail. The clamping device for vertical bending forced vibration does not require bearings, therefore no vertical connecting parts are installed in the device. The forced vibration module is bolted to the bolt holes at the center of the crossbeam 3. The tail of the connecting rod of the forced vibration module 8 passes through the bolt holes on the U-shaped adapter 6 and is secured with anti-slip nuts. It is important to note that when installing the bridge segment model, the model should be within the target clearance when the crank-rocker mechanism is in the centerline position.

[0076] After the vertical bending forced vibration device for the bridge segment model is installed, the subsequent test operations are basically the same as those for the torsional forced vibration test.

[0077] In this embodiment, different vertical vibration amplitudes are achieved by adjusting the fixed positions of the crank and rocker in the forced vibration module, and different vibration frequencies are achieved by adjusting the speed of the stepper motor.

Claims

1. An experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges, comprising a bridge segment model, a frame with crossbeams on both sides, three different types of clamping devices, a wind-wave coupling field generation device, an aerodynamic load measurement device, an acceleration sensor, and a wind speed measurement device, characterized in that: The wind-wave coupling field generation device includes a recirculating or direct-flow wind tunnel, a rocking or pushing wave generator, and a water tank. This device generates wind-driven and wave fields. The wind speed in the test section is adjusted by controlling the fan speed using the recirculating or direct-flow wind tunnel, and the turbulence intensity of the generated wind field is adjusted by adding rough elements and wedges. The rocking or pushing wave generator generates the required regular and irregular waves by controlling its input hydrodynamic parameters. In the experiment, the fan is started first, and after the wind field in the test section stabilizes, the wave generator is activated to generate regular or irregular waves. The wave field generated by the wave generator is superimposed with the wind-generated wave field before the experiment begins. During the experiment, the wave-damping section at the tail of the water tank and the active wave-damping method of the wave generator reduce the influence of reflected waves on the test results. Three different types of clamping devices are used to clamp the bridge segment model onto the frame for three-component force coefficient tests, torsional forced vibration tests, and vertical bending forced vibration tests, thereby completing the measurement of the aerodynamic three-component force coefficients and flutter derivatives of the bridge segment model. Accelerometers are installed on the bridge segment model to acquire forced vibration data. A wind speed measuring device is positioned in front of the bridge segment model to acquire incoming wind speed data. The aerodynamic load measuring device uses a pressure scanning valve to acquire pressure distribution on the bridge segment model under different wave phases. The bridge segment model is hollow and has ribs installed inside. Multiple pressure measuring holes are opened along the spanwise centerline on the upper and lower surfaces of the bridge segment model to set the measuring points of the pressure scanning valve. End plates are provided on the left and right sides of the bridge segment model to ensure the stability of the wind field where the bridge segment model is located.

2. The experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges according to claim 1, characterized in that: The clamping device used in the aerodynamic force coefficient test includes a high-precision rotary slide, two sets of vertical connectors, two sets of U-shaped conversion joints, and a locking device. The two ends of the bridge segment model in the spanwise direction are connected to the high-precision rotary slide through U-shaped conversion joints. The two sides of the high-precision rotary slide are fixedly connected to the two side beams of the frame through vertical connectors. The wind attack angle of the bridge segment model is precisely controlled by adjusting the angle of the high-precision rotary slide. After positioning, the high-precision rotary slide is fixed by the locking device.

3. The experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges according to claim 1, characterized in that: The clamping device used in the torsional forced vibration test includes two sets of crank-rocker mechanisms, two sets of vertical connectors, and two sets of U-shaped adapters with extended tail sections. The two ends of the spanwise direction of the bridge segment model are connected to the U-shaped adapters with extended tail sections. Each set of U-shaped adapters with extended tail sections is rotatably connected to a set of vertical connectors. The two sets of vertical connectors are fixedly connected to the two side beams of the frame. The extended tail section of each set of U-shaped adapters with extended tail sections is rotatably connected to the actuating end of a set of crank-rocker mechanisms. The fixed sections of the two sets of crank-rocker mechanisms are fixedly connected to the two side beams of the frame and located behind the vertical connectors. The two sets of crank-rocker mechanisms need to operate synchronously to prevent the bridge segment model from twisting.

4. The experimental system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges according to claim 1, characterized in that: The clamping device used in the vertical bending forced vibration test includes two sets of crank-rocker mechanisms and two sets of U-shaped adapter joints. The two ends of the spanwise direction of the bridge segment model are fixedly connected to the moving ends of the two sets of crank-rocker mechanisms through U-shaped adapter joints. The outer shells of the two sets of crank-rocker mechanisms are fixedly connected to the crossbeams on both sides of the frame. The vertical bending forced vibration of the bridge segment model is achieved through the crank-rocker mechanism. The two sets of crank-rocker mechanisms need to operate synchronously to avoid the torsion of the bridge segment model.

5. A test method for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges, derived from the test system for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges according to any one of claims 1-4, is characterized in that: The pressure scanning valve collects pressure data acting on the bridge segment model in real time. The collected pressure data is integrated to obtain the aerodynamic force acting on the bridge segment model. The calculation formula is as follows: where F L (α), F D (α), M(α) are the lift, drag, and moment on the bridge deck model, respectively; P i is the pressure at the ith measurement point; Δl is the distance between adjacent measurement points; α is the angle of attack of the bridge deck model; and L is the spanwise length of the bridge deck model. After obtaining the lift, drag, and lift moment data of the model through integration, the three force coefficients of the bridge segment model are calculated using the following formula: wherein: C L (α), C D (α), C M (α) are the lift coefficient, the drag coefficient and the moment coefficient of the bridge section model, respectively; U is the wind speed of the incoming flow in front of the bridge section model; B is the width of the bridge section model; and D is the height of the bridge section model. The flutter derivatives of the bridge section model can be obtained based on the aerodynamic force, the forced vibration data of the bridge section model and the incoming flow wind speed data.

6. The experimental method for studying the influence of wind-wave coupling on the aerodynamic characteristics of bridges according to claim 5, characterized in that: Wave height meters were placed at the front, middle and rear of the bridge segment model to monitor the wave surface time history at the bridge segment model. By studying the relationship between wave elements and aerodynamic three-component force coefficients and flutter derivatives, the influence mode of the bottom wave boundary on aerodynamic load characteristics was obtained. Based on the pressure distribution characteristics under different wave phases, the mechanism of the wave boundary on aerodynamic load characteristics under the combined action of wind and waves was further derived.

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