Suspension bridge three-dimensional flutter critical wind speed prediction method and system based on segment model parameter correction

Abstract

The application discloses a kind of based on segment model parameter correction's suspension bridge three-dimensional flutter critical wind speed prediction method and system, and it is related to bridge engineering technical field.First, according to the base order vibration mode, the segment model flutter test of suspension bridge is carried out to obtain the flutter critical wind speed and flutter frequency of suspension bridge;According to the flutter critical wind speed, the flutter derivative is obtained by interpolation calculation;Based on the principle that two-dimensional segment model flutter system damping and three-dimensional full-bridge aeroelastic model flutter system damping are equal, the segment model system mass correction factor is obtained, and then the segment model system mass is corrected.The above steps are repeated until the value of segment model system mass correction factor no longer changes, and the flutter critical wind speed obtained by the current state segment model flutter test is used as the predicted value of suspension bridge three-dimensional flutter critical wind speed.The prediction result of the suspension bridge three-dimensional flutter critical wind speed of the application is significantly improved in accuracy compared with the traditional segment model test method, and the test operation is simple, efficient.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bridge engineering, and more particularly to a suspension bridge three-dimensional flutter critical wind speed prediction method and system based on segment model parameter correction. BACKGROUND

[0002] The bridge wind-resistant design specification points out that the traditional segment model flutter test needs to be carried out according to the base-order vertical bending and torsional modal of the suspension bridge to preliminarily evaluate the flutter stability of the suspension bridge or optimize the main beam section aerodynamic shape. Due to the influence of the multi-modal coupling effect in the three-dimensional aeroelastic effect, the flutter critical wind speed predicted by the traditional two-dimensional segment model test is sometimes even significantly higher than and seriously deviates from the prediction result of the three-dimensional full-bridge aeroelastic model test, which is contrary to the expectation of researchers and bridge design engineers. Therefore, it is necessary to propose a segment model test method capable of more accurately predicting the three-dimensional flutter critical wind speed of the suspension bridge.

[0003] The prior art one is based on the analysis of the two-degree-of-freedom coupled flutter mechanism of the bridge structure, and calculates the improved design parameters of the segment model flutter test according to the least square method. The prior art two proposes an equivalent mass simulation method considering the incomplete similarity of vibration modes and the multi-modal coupling effect in the segment model flutter test. It is worth pointing out that although the prior arts one and two can more accurately predict the three-dimensional flutter critical wind speed of the suspension bridge through the segment model test, they have more modified test parameters or the determination process of the test parameters is more complex, so they have not been widely applied to the design and research of actual engineering.

[0004] In summary, in the method for predicting the flutter critical wind speed of the suspension bridge based on the prior art, the difference between the flutter critical wind speed of the suspension bridge predicted by the traditional segment model flutter test and the prediction result of the full-bridge aeroelastic model test is obvious, and the prediction result of the segment model may significantly overestimate the flutter stability of the suspension bridge, so it is a technical problem urgently to be solved in the field to propose a segment model test method for conveniently and accurately predicting the three-dimensional flutter critical wind speed of the suspension bridge. SUMMARY

[0005] Therefore, starting from the bridge flutter theory, based on the principle that the system damping of the two-dimensional segment model and the three-dimensional full-bridge aeroelastic model is equal, the present application derives the calculation expression of the segment model system mass correction factor, and accordingly proposes a suspension bridge three-dimensional flutter critical wind speed prediction method and system based on segment model system mass correction.

[0006] In order to achieve the above-mentioned purpose, the present application provides the following technical scheme:

[0007] A suspension bridge three-dimensional flutter critical wind speed prediction method based on segment model parameter correction, comprising the following steps:

[0008] Step 1, segment model flutter test of the suspension bridge is carried out according to the fundamental vibration mode, and the flutter critical wind speed and the flutter frequency of the suspension bridge are obtained;

[0009] Step 2, the flutter derivative is obtained by interpolation calculation according to the flutter critical wind speed

[0010] Step 3, the flutter frequency and the flutter derivative are used to calculate the flutter critical wind speed of the suspension bridge Based on the principle that the system damping of the two-dimensional segment model flutter system is equal to the system damping of the three-dimensional full-bridge aeroelastic model flutter system, the segment model system mass correction factor η is obtained;

[0011] Step 4, the segment model system mass is corrected by using the mass correction factor, and the segment model flutter test of the suspension bridge is carried out again;

[0012] Step 5, the steps 1 to 4 are repeated until the value of the segment model system mass correction factor η no longer changes, and the flutter critical wind speed obtained by the current state segment model flutter test is taken as the predicted value of the three-dimensional flutter critical wind speed of the suspension bridge.

[0013] Further, in the step 1, the fundamental vibration mode includes the fundamental symmetric torsional mode and the second-order symmetric vertical bending mode;

[0014] For a single-span simply-supported suspension bridge, the flutter vertical bending participation mode is the fundamental mode and the second-order symmetric vertical bending mode; for a multi-span continuous support suspension bridge, the flutter vertical bending participation mode is the fundamental mode and the third-order symmetric vertical bending mode.

[0015] Further, in the step 2, the flutter derivative is obtained by interpolation calculation The process is as follows:

[0016] Step 2.1, the vertical free vibration decay time history of the segment model under the condition of no wind and under the condition of the flutter critical wind speed is recorded respectively, and the instantaneous amplitude u0(t) of the vertical free vibration decay time history under the condition of no wind and the instantaneous amplitude u1(t) of the vertical free vibration decay time history under the condition of the flutter critical wind speed are obtained;

[0017] Step 2.2, according to the instantaneous amplitudes u0(t) and u1(t), the time-varying system damping ζ v0 (t) of the segment model under the condition of no wind and the time-varying system damping ζ v1 (t) of the segment model under the condition of the flutter critical wind speed are calculated respectively;

[0018] Step 2.3, according to the time-varying system damping ζ v0 (t) of the segment model under the condition of no wind and the time-varying system damping ζ v1 (t) of the segment model under the condition of the flutter critical wind speed, the flutter derivative is calculated

[0019] Further, in the step 2.1, the acquisition method of the instantaneous amplitudes u0(t) and u1(t) is as follows:

[0020] The Hilbert transform HT is performed on the vertical free vibration decay time history of the segment model under the windless condition and the flutter critical wind speed condition to obtain the instantaneous amplitude envelope of the vertical free vibration decay time history. The exponential function fitting is performed on the instantaneous amplitude envelope to obtain the fitting expression of the instantaneous amplitude u i (t) as follows:

[0021]

[0022] In the formula, u i (t) is the instantaneous amplitude of the vertical free vibration decay time history, t is the time, u0, λ1, λ2, κ1 and κ2 are fitting coefficients.

[0023] Further, in the step 2.2, the time-varying system damping ζ vi (t) is calculated as follows:

[0024]

[0025] In the formula, ζ vi (t) is the time-varying system damping of the segment model; f vi is the vibration frequency of the vertical free vibration decay time history, f v0 represents the vibration frequency of the vertical free vibration decay time history under the windless condition, f v1 represents the vibration frequency of the vertical free vibration decay time history under the flutter critical wind speed condition.

[0026] Further, in the step 2.3, the flutter derivative is calculated as follows:

[0027]

[0028] In the formula, ρ is the air density; B is the width of the main beam of the suspension bridge; and m is the equivalent mass of the vertical bending mode.

[0029] Further, in the step 3, the calculation formula of the system mass correction factor η of the segment model is as follows:

[0030]

[0031]

[0032]

[0033] where, p is air density; B is the width of the main girder of the suspension bridge; m is the equivalent mass of the vertical bending mode; ω v1 represents the first-order natural circular frequency of the vertical bending mode, ω v2 represents the second-order natural circular frequency of the vertical bending mode; ω is the flutter circular frequency; D v1,α and D v2,α is the mode shape similarity factor between the vertical bending mode and the base-order torsional mode; L g is the length of the main girder of the suspension bridge; φ vj (s g ) is the vertical bending mode shape of the main girder of the suspension bridge; φ t (s g ) is the torsional mode shape of the main girder of the suspension bridge; s g is the local coordinate of the main girder of the suspension bridge.

[0034] A suspension bridge three-dimensional flutter critical wind speed prediction system based on segment model parameter correction, comprising:

[0035] A flutter test module is configured to perform a segment model flutter test of the suspension bridge according to a base-order vibration mode, and obtain a flutter critical wind speed and a flutter frequency of the suspension bridge.

[0036] A flutter derivative calculation module is configured to obtain a flutter derivative H*1 by interpolation calculation according to the flutter critical wind speed.

[0037] A mass correction factor calculation module is configured to obtain a segment model system mass correction factor η based on the principle that the two-dimensional segment model flutter system damping is equal to the three-dimensional full-bridge aeroelastic model flutter system damping, according to the flutter frequency and the flutter derivative H*1.

[0038] A system mass correction module is configured to correct the segment model system mass by using the mass correction factor, and perform a segment model flutter test of the suspension bridge again.

[0039] A cycle module is configured to repeatedly perform system mass correction and flutter test until the value of the segment model system mass correction factor η no longer changes, and take the flutter critical wind speed obtained by the current state segment model flutter test as a three-dimensional flutter critical wind speed prediction value of the suspension bridge.

[0040] According to the above technical solution, the present application provides a suspension bridge three-dimensional flutter critical wind speed prediction method and system based on segment model parameter correction, which has the following beneficial effects compared with the prior art:

[0041] (1) improve the prediction accuracy: the present application is creatively based on the principle that the damping of the two-dimensional segment model flutter system is equal to the damping of the three-dimensional full-bridge aeroelastic model flutter system, and the calculation expression of the segment model system mass correction factor is proposed, and the system mass of the segment model is corrected through iteration, thereby reducing the difference between the prediction results of the segment model flutter test and the full-bridge aeroelastic model test, and significantly improving the accuracy of the prediction of the flutter critical wind speed of the suspension bridge.

[0042] (2) reduce the test parameter correction: the present application scheme does not need to make complex correction to multiple test parameters, but only corrects the mass of the segment model through the segment model system mass correction factor, simplifies the test process, and reduces the test difficulty.

[0043] In summary, the present application scheme has the beneficial effects of accurate prediction, simple operation, high test efficiency, etc., and engineering and technical personnel can conveniently and accurately master the flutter performance of the suspension bridge according to the present application scheme, and significantly improve the quality and work efficiency of the wind resistance design of the suspension bridge. BRIEF DESCRIPTION OF DRAWINGS

[0044] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0045] Figure 1 is a flow chart of a suspension bridge three-dimensional flutter critical wind speed prediction method based on segment model parameter correction according to the present application;

[0046] Figure 2 is a flutter derivative provided by a specific embodiment of the present application schematic diagram;

[0047] Figure 3 is a three-dimensional flutter characteristic change schematic diagram provided by a specific embodiment of the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0049] The embodiments of the present application disclose a suspension bridge three-dimensional flutter critical wind speed prediction method based on segment model parameter correction, as shown in Figure 1, comprising the following steps:

[0050] Step 1, segment model flutter test of a suspension bridge is carried out according to a fundamental vibration mode, to obtain a flutter critical wind speed and a flutter frequency of the suspension bridge.

[0051] The fundamental vibration mode mainly includes a fundamental symmetric torsional mode and two-order symmetric vertical bending modes; for a single-span simply-supported suspension bridge, a flutter vertical bending participation mode is a fundamental mode and a two-order symmetric vertical bending mode; for a multi-span continuous support suspension bridge, a flutter vertical bending participation mode is a fundamental mode and a three-order symmetric vertical bending mode.

[0052] Step 2, according to the flutter critical wind speed, a flutter derivative is obtained by an interpolation calculation The specific process is as follows:

[0053] Step 2.1, vertical free vibration decay time histories of the segment model under no wind condition and under the flutter critical wind speed condition are recorded respectively, the vertical free vibration decay time histories of the segment model under no wind condition and under the flutter critical wind speed condition are subjected to Hilbert transform HT, to obtain an instantaneous amplitude envelope of the vertical free vibration decay time history, the instantaneous amplitude envelope is subjected to exponential function fitting, to obtain an instantaneous amplitude u0(t) of the vertical free vibration decay time history under no wind condition and an instantaneous amplitude u1(t) of the vertical free vibration decay time history under the flutter critical wind speed condition.

[0054] Wherein, the fitting expression of the instantaneous amplitude u i (t) is as follows:

[0055]

[0056] In the formula, u i (t) is the instantaneous amplitude of the vertical free vibration decay time history, t is time, u0, λ1, λ2, κ1 and κ2 are fitting coefficients.

[0057] Step 2.2, according to the instantaneous amplitudes u0(t) and u1(t), a time-varying system damping ζ v0 (t) of the segment model under no wind condition and a time-varying system damping ζ v1 (t) of the segment model under the flutter critical wind speed condition are calculated respectively.

[0058] The calculation formula of the time-varying system damping ζ vi (t) is as follows:

[0059]

[0060] In the formula, ζvi (t) is the time-varying system damping of the segment model; f vi is the vibration frequency of the vertical free vibration decay time history, f v0the vibration frequency of the vertical free vibration decay time history under the no-wind condition, f v1 the vibration frequency of the vertical free vibration decay time history under the flutter critical wind speed condition.

[0061] Step 2. The aerodynamic damping under the wind condition is obtained by deducting the system damping under the no-wind condition from the system damping under the wind condition. Considering the flutter derivative which is basically independent of the amplitude, the flutter derivative under the flutter critical wind speed condition is :

[0062]

[0063] where ρ is the air density; B is the width of the main girder of the suspension bridge; and m is the equivalent mass of the vertical bending mode.

[0064] Step 3. According to the flutter frequency and the flutter derivative Based on the principle that the system damping of the two-dimensional segment model is equal to the system damping of the three-dimensional full-bridge aeroelastic model, the segment model system mass correction factor η is obtained.

[0065] The calculation formula of the segment model system mass correction factor η is:

[0066]

[0067]

[0068]

[0069] where ρ is the air density; B is the width of the main girder of the suspension bridge; m is the equivalent mass of the vertical bending mode; ω v1 is the first-order natural circular frequency of the vertical bending mode, ω v2 is the second-order natural circular frequency of the vertical bending mode; ω is the flutter circular frequency; D v1,α and D v2,α are the mode shape similarity factors between the vertical bending mode and the base-order torsional mode; L g is the length of the main girder of the suspension bridge; φ vj (s g ) is the vertical bending mode shape of the main girder of the suspension bridge; φ t (s g ) is the torsional mode shape of the main girder of the suspension bridge; s g is the local coordinate of the main girder of the suspension bridge.

[0070] Step 4. The segment model system mass is corrected by using the mass correction factor, and the segment model flutter test of the suspension bridge is re-performed;

[0071] Step 5, repeating the step 1 to step 4 until the value of the segment model system quality correction factor η is no longer changed and tends to be stable, taking the flutter critical wind speed obtained by the flutter test of the segment model in the current state as the predicted value of the three-dimensional flutter critical wind speed of the suspension bridge.

[0072] The embodiment of the present application also provides a three-dimensional flutter critical wind speed prediction system of a suspension bridge based on segment model parameter correction, which is used for implementing the above method and comprises:

[0073] The flutter test module is used for performing the segment model flutter test of the suspension bridge according to the fundamental vibration mode, and obtaining the flutter critical wind speed and the flutter frequency of the suspension bridge.

[0074] The flutter derivative calculation module is used for obtaining the flutter derivative by means of interpolation calculation according to the flutter critical wind speed.

[0075] The quality correction factor calculation module is used for obtaining the quality correction factor according to the flutter frequency and the flutter derivative. The segment model system quality correction factor η is obtained based on the principle that the system damping of the two-dimensional segment model flutter system is equal to the system damping of the three-dimensional full-bridge aeroelastic model flutter system.

[0076] The system quality correction module is used for correcting the segment model system quality by using the quality correction factor, and performing the segment model flutter test of the suspension bridge again.

[0077] The cycle module is used for repeatedly performing the system quality correction and the flutter test until the value of the segment model system quality correction factor η is no longer changed, and taking the flutter critical wind speed obtained by the flutter test of the segment model in the current state as the predicted value of the three-dimensional flutter critical wind speed of the suspension bridge.

[0078] For the system modules disclosed in the embodiment, the description is relatively simple because they correspond to the method disclosed in the embodiment, and the relevant parts can be referred to the method part.

[0079] The application mode and effects of the present application will be described in detail in combination with specific embodiments.

[0080] The Zhangjinggao Yangtze River Bridge North Channel Bridge is selected for embodiment analysis. The Zhangjinggao Yangtze River Bridge North Channel Bridge is a double-tower single-span steel box girder suspension bridge with a span of 1208 m, and the width of the steel box girder is 47.7 m, the width-height ratio is 11.9, and it is a flat streamline box girder section. The main calculation parameters of the Zhangjinggao Yangtze River Bridge North Channel Bridge are shown in Tables 1 and 2.

[0081] Table 1: Modal parameters of the Zhangjinggao Yangtze River Bridge North Channel Bridge

[0082]

[0083] Note: V represents vertical bending mode, S represents symmetric mode, and T represents torsional mode. For example, VS-1 represents the first-order symmetric vertical bending mode.

[0084] Table 2 Modal similarity factors of the North Channel Bridge of Zhangjinggao Yangtze River Bridge

[0085]

[0086] Flutter derivative of the main girder of the north channel bridge of the Zhangjinggao Yangtze River Bridge under an initial wind angle of attack of 0° like Figure 2 As shown.

[0087] Flutter Critical Wind Speed ​​U of Segmental Model Wind Tunnel Test of Zhangjinggao Yangtze River Bridge North Channel Bridge cr Flutter frequency f cr And quality correction factor η, such as Figure 3 As shown. First, a traditional segmental model wind tunnel test (corresponding to the first segmental model test) is conducted based on the dynamic characteristics and equivalent mass of the fundamental mode, and η is calculated accordingly; then, the system mass of the segmental model is modified based on the existing η, and the following steps are performed: Figure 3 The second segmental model experiment is shown, and η is updated; the system quality of the segmental model is modified according to the updated η, and the following steps are performed: Figure 3 The third and fourth segmental model tests are shown. When the second segmental model flutter test was conducted, the flutter critical wind speed and flutter frequency predicted by the segmental model had already stabilized and no longer changed.

[0088] Table 3 shows the flutter critical wind speeds of the entire bridge aeroelastic model, the traditional segmental model, and the prediction method of this invention for the North Channel Bridge of the Zhangjinggao Yangtze River Bridge under the condition of 0° initial wind angle of attack.

[0089] Table 3. Flutter critical wind speed (m·s) for the North Channel Bridge of Zhangjinggao Yangtze River Bridge -1 )

[0090]

[0091] Comparison reveals that, compared to the prediction results of traditional segmental models, the flutter critical wind speed of suspension bridges predicted by the method of this invention is closer to the three-dimensional flutter critical wind speed of the full-bridge aeroelastic model. The only experimental parameter that needs modification in this invention is the mass of the segmental model system, and the prediction experiment process is relatively simple, thus possessing high application value.

[0092] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0093] The foregoing description of the disclosed embodiments enables a person skilled in the art to make or use the application. Modifications of these embodiments will occur to persons of skill in the art, and that the appended claims are intended to cover all such modifications that do not depart from the true spirit and scope of the application. Therefore, the application is not limited to the embodiments shown but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for predicting the critical wind speed of a three-dimensional flutter of a suspension bridge based on segment model parameter correction, characterized in that, The method comprises the following steps: Step 1, segment model flutter test of the suspension bridge is carried out according to the fundamental vibration mode, and the flutter critical wind speed and the flutter frequency of the suspension bridge are obtained; Step 2, according to the flutter critical wind speed, the flutter derivative is obtained by interpolation calculation ; Step 3, determining the flutter frequency and the flutter derivative based on the flutter frequency and the flutter derivative , based on the principle that the flutter system damping of the two-dimensional segment model is equal to the flutter system damping of the three-dimensional full-bridge aeroelastic model, a segment model system mass correction factor is obtained ; Step 4, the system mass of the segment model is corrected by using the mass correction factor, and the segment model flutter test of the suspension bridge is carried out again; Step 5, repeat the step 1 to step 4 until the value of segment model system quality correction factor is no longer changed, and the flutter critical wind speed obtained by the current state segment model flutter test is taken as the predicted value of the three-dimensional flutter critical wind speed of the suspension bridge; In the step 1, the fundamental vibration mode comprises a fundamental symmetric torsional mode and two-order symmetric vertical bending modes; For a single-span simply-supported suspension bridge, the flutter vertical bending participation mode is a fundamental two-order symmetric vertical bending mode; for a multi-span continuous support suspension bridge, the flutter vertical bending participation mode is a fundamental three-order symmetric vertical bending mode; In step 2, the derivative of the flutter is obtained by interpolation The process is as follows: Step 2.1, record the vertical free vibration decay time history of the segment model under no wind condition and under flutter critical wind speed condition respectively, and obtain the instantaneous amplitude of the vertical free vibration decay time history under no wind condition and the instantaneous amplitude of the vertical free vibration decay time history under flutter critical wind speed condition ; Step 2.

2. Calculate the time-varying system damping of the segment model under windless condition and respectively, according to the instantaneous amplitude and the time-varying system damping of the segment model under flutter critical wind speed condition ; Step 2.

3. Calculate the time-varying system damping of the section model under no wind condition and the time-varying system damping of the section model under flutter critical wind speed condition , and the flutter derivative ; In step 3, the segment model system quality correction factor The calculation formula is: wherein is the air density; is the width of the main girder of the suspension bridge; is the equivalent mass of the vertical bending mode; denotes the first order natural circular frequency of the vertical bending mode, denotes the second order natural circular frequency of the vertical bending mode; is the flutter circular frequency; and is the mode shape similarity factor between the vertical bending mode and the base order torsional mode; is the length of the main girder of the suspension bridge; is the vertical bending mode shape of the main girder of the suspension bridge; is the torsional mode shape of the main girder of the suspension bridge; is the local coordinate of the main girder of the suspension bridge.

2. The method according to claim 1, wherein, In step 2.1, the instantaneous amplitude and The acquisition method is: The Hilbert transform (HT) is applied to the vertical free vibration decay time histories of the segment model under the windless condition and the flutter critical wind speed condition to obtain the instantaneous amplitude envelope of the vertical free vibration decay time histories. The exponential function fitting is applied to the instantaneous amplitude envelope to obtain the fitting expression of the instantaneous amplitude ​ wherein is the instantaneous amplitude of the vertical free vibration decay time history, is time, , , , and are fitting coefficients.

3. The method of claim 2, wherein the method is characterized by: In step 2.2, the time-varying system damping The calculation formula is: wherein is the time-varying system damping of the segment model; is the vibration frequency of the vertical free vibration decay time history, represents the vibration frequency of the vertical free vibration decay time history under wind-free conditions, represents the vibration frequency of the vertical free vibration decay time history under flutter critical wind speed conditions.

4. The method of claim 3, wherein the method is characterized by, In step 2.3, the formula for calculating the derivative of the chatter is wherein is the air density; is the width of the main girder of the suspension bridge; is the equivalent mass of the vertical bending mode.

5. A system for predicting the critical wind speed of a suspension bridge in three-dimensional flutter based on segment model parameter correction, characterized in that, The system comprises: a flutter test module, configured to carry out segment model flutter test of the suspension bridge according to the fundamental vibration mode, and obtain the flutter critical wind speed and the flutter frequency of the suspension bridge; a flutter derivative calculation module, configured to obtain a flutter derivative by means of interpolation calculation according to the flutter critical wind speed ; a mass correction factor calculation module configured to calculate a mass correction factor based on the flutter frequency and the flutter derivative , the mass correction factor of the segment model system is obtained based on the principle that the damping of the flutter system of the two-dimensional segment model is equal to the damping of the flutter system of the three-dimensional full-bridge aeroelastic model ​ a system mass correction module, configured to correct the system mass of the segment model by using the mass correction factor, and carry out segment model flutter test of the suspension bridge again; a cycle module for repeating the system mass correction and the flutter test until the value of the segment model system mass correction factor is no longer changed, and taking the flutter critical wind speed obtained by the segment model flutter test in the current state as the predicted value of the three-dimensional flutter critical wind speed of the suspension bridge.

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