CN110029572A - Loads of Long-span Bridges flowing control wind resistance method based on breathing unit - Google Patents

Abstract

The invention discloses a wind resistance method for flow control of a large-span bridge based on a breathing unit. The method includes the following steps: Step 1: Install breathing unit pipes at the bottom of the main beam near the sharp corners on both sides of the leading edge and the trailing edge. The breathing units are arranged at equal intervals in the breathing unit pipeline, and the two ends of the breathing unit are respectively provided with an inhalation air outlet and an air blowing air outlet, a frequency conversion axial flow fan is arranged inside, and a rectifier honeycomb is arranged at the air outlet; step 2, use the frequency conversion axial flow fan to breathe The suction tuyere and blowing tuyere of the unit pipeline produce two different effects of inhalation and blowing. The breathing unit is used as the disturbance source of the flow field around the main beam to suppress the development of the large-scale spanwise vortex of the wake and stimulate the downstream vortex. , and then stimulate the secondary wake instability and realize the control of the wind-induced vibration of the main beam. The invention uses the breathing unit as a disturbance device to improve the structure of the disturbance flow field of the main girder of the bridge, so as to achieve the purpose of suppressing the wind vibration of the main girder, and has the advantages of high efficiency, simplicity, wide application range and the like.

Description

Wind resistance method for flow control of large-span bridges based on breathing unit

technical field

The invention belongs to the technical field of civil engineering, and relates to a flow control wind resistance method for a large-span bridge.

Background technique

With the advancement of materials and the improvement of construction methods, modern bridges are developing in the direction of large span, light weight and flexibility. The structural stiffness and damping are continuously reduced. The problem of wind-induced vibration of bridges is becoming more and more prominent. Typical examples of flutter, buffeting, and vortex-induced vibration are Wind-induced effects have gradually become a key factor to be considered in the design of long-span bridges. In the wind-induced vibration of the main girder of long-span bridges, flutter is a kind of divergent vibration, that is, once it occurs, it will cause the overall collapse of the main girder of the bridge. . Therefore, suppressing flutter and vortex-induced vibration of long-span bridges has always been an important issue for scholars in the field of structural wind engineering.

Generally, the aerodynamic measures for wind vibration control of long-span bridges include active control and passive control. The passive method is to improve the wind resistance of long-span bridges by changing the aerodynamic shape of the main beam section of the bridge or adding auxiliary structures. Due to the simplicity and economy of this method, it has been widely used in practical projects, including fairings, deflectors, spoilers, central stabilizers, central slots, flaps, and air nozzles. However, it is usually only possible to improve the aerodynamic shape of the main beam within a certain range, and a lot of experiments and simulations are needed to verify the effectiveness before use. The control method proposed by analyzing the flow field of the dimensional bridge section is not only limited in application conditions, but also requires a control device to be installed along the spanwise direction of the main girder, which undoubtedly greatly increases the cost. Active control is a research that uses active energy supply to directly improve the boundary layer around the bridge and thus improve the bridge's wind resistance. At present, the commonly used measures for active control of aerodynamic shape include aerodynamic flaps and constant suction methods. Aerofoils are a way to improve the flutter stability of the system by effectively dissipating the energy from the main beam into the system. Steady inhalation is an effective technical means to actively suppress the separation of the boundary layer around the object, which can effectively improve the stability of bridge flutter. Vibration stability is reduced. The above methods all have the problems of low control efficiency, small control range and large limitations.

SUMMARY OF THE INVENTION

In order to improve the efficiency of controlling wind-induced vibration, the present invention provides a wind-resisting method for large-span bridge flow control based on the breathing unit based on the instability of the bluff body wake spanwise vortex and using the breathing unit as a disturbance device. The method of the invention is a novel three-dimensional spanwise turbulence active control method. The breathing unit is used as a disturbance device to improve the turbulence field structure of the main beam of the bridge, so as to achieve the purpose of suppressing the wind vibration of the main beam. The control method has high efficiency, simplicity and application range. Wide and other advantages.

The purpose of this invention is to realize through the following technical solutions:

A wind resistance method for flow control of a long-span bridge based on a breathing unit, comprising the following steps:

Step 1: Install breathing unit pipes at the bottom of the main beam near the sharp corners on both sides of the leading edge and the trailing edge. The breathing unit pipes are provided with breathing units at equal intervals, and the two ends of the breathing unit are respectively provided with inhalation air outlets and blowing air outlets. A variable frequency axial flow fan is set inside to provide suction and blowing air flow, and a rectifier honeycomb is set at the tuyere to form a uniform flow;

Step 2. Use the variable frequency axial flow fan to produce two different effects of inhalation and air blowing at the inhalation air outlet and air blowing air outlet of the breathing unit pipeline, and use the breathing unit as the disturbance source of the flow field around the main beam to suppress the large-scale wake flow. The development of the spanwise vortex stimulates the downstream vortex, which in turn stimulates the instability of the secondary wake and realizes the control of the wind-induced vibration of the main girder.

Compared with the prior art, the present invention has the following advantages:

1. The present invention can suppress the wind-induced vibration in a larger wind speed range by adjusting the breathing flow.

2. The present invention utilizes the spanwise vortex instability of the bluff body wake, which can improve the stability of the main beam flutter and vortex vibration.

3. The breathing unit is a disturbance device of the breathing mode. The fan is used to produce two different effects of inhalation and blowing at the two air outlets of the pipeline. The breathing unit is used as a disturbance source to suppress the development of the large-scale spanwise vortex of the wake. The downstream vortex is excited to control the wind-induced vibration of the main beam.

Description of drawings

Fig. 1 is the schematic diagram of the pipeline arrangement of the breathing unit;

Figure 2 is a schematic diagram of the three-dimensional spanwise disturbance flow control of the breathing unit;

In the figure: 1- Bottom surface of main beam, 2- Breathing unit pipeline, 3- Inhalation air outlet, 4- Air blow air outlet, 5- Spanwise vortex structure, 6- Optimal spacing of three-dimensional spanwise disturbance, 7- incoming wind.

Detailed ways

The technical solutions of the present invention will be further described below in conjunction with the accompanying drawings, but are not limited thereto. Any modification or equivalent replacement of the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention shall be included in the present invention. within the scope of protection.

The present invention provides a wind resistance method for flow control of a large-span bridge based on a breathing unit, as shown in Figures 1-2, the method utilizes three-dimensional spanwise disturbance to excite the instability of the spanwise vortex of the bluff body wake, suppressing the The development of the large-scale spanwise vortices in the wake stimulates the downstream vortices, thereby realizing the control of the wind-induced vibration of the main girder.

Because the bridge section is different, its wind field characteristics under the action of the incoming flow are also different, so the breathing unit should be determined according to the specific situation, but the following principles should be followed:

(1) According to the local wind conditions combined with the bridge section form, according to the results obtained from the wind tunnel test, select the optimal spacing of spanwise disturbances . And the length of the breathing unit pipe 2 should be 0.5 times . The optimal value is between 2 and 3 times the beam height of the main beam.

(2) The breathing unit pipeline 2 is installed at the bottom of the main girder near the sharp corners on both sides of the leading edge and trailing edge, which can not only slow down the flow separation in the upstream area, but also stimulate the downstream vortex to suppress the wind-induced vibration.

(3) The section of the breathing unit duct 2 and the shape of the tuyere are square, and the side length should be determined based on the wind tunnel test combined with the actual results, taking the required maximum air flow and wind speed, and the side length should not be greater than 0.125 times the height of the main beam.

(4) The height of the breathing unit pipe 2 is not more than 0.125 times the height of the main beam, and the flow rate should be based on the local wind conditions and wind tunnel test results to obtain the optimal result.

Claims (7)

1. a kind of Loads of Long-span Bridges flowing control wind resistance method based on breathing unit, it is characterised in that the method includes walking as follows It is rapid:

Step 1: breathing unit pipeline, the breathing unit pipe are installed close to leading edge and rear two sides sharp corner in girder bottom Air-breathing air port and air blowing air port, inside setting frequency conversion is respectively set in spaced set breathing unit in road, the both ends of breathing unit Axial flow blower inhales air blowing flow for providing, and setting rectification honeycomb forms uniform flow at air port；

Step 2: generating air-breathing and air blowing two in the air-breathing air port of breathing unit pipeline and air blowing air port using frequency conversion axial flow fan The different effect of kind inhibits the development of wake flow large scale prospect spape, excitation using breathing unit as the disturbing source of girder Flow Field Fair current excites secondary wake flow unstability to whirlpool, realizes the control to girder wind-induced vibration.

2. the Loads of Long-span Bridges flowing control wind resistance method according to claim 1 based on breathing unit, it is characterised in that institute The length for stating breathing unit pipeline takes 0.5,For the optimal spacing of disturbance along span.

3. the Loads of Long-span Bridges flowing control wind resistance method according to claim 2 based on breathing unit, it is characterised in that institute It statesBest value be between 2 to 3 times of girder deck-moldings.

4. the Loads of Long-span Bridges flowing control wind resistance method according to claim 1 based on breathing unit, it is characterised in that institute Breathing unit pipeline section is stated to be square with inlet shape.

5. the Loads of Long-span Bridges flowing control wind resistance method according to claim 4 based on breathing unit, it is characterised in that institute Square side length is stated no more than 0.125 times of girder deck-molding.

6. the Loads of Long-span Bridges flowing control wind resistance method according to claim 1 or 4 based on breathing unit, it is characterised in that The breathing unit duct height is not more than 0.125 times of girder height.

7. the Loads of Long-span Bridges flowing control wind resistance method according to claim 1 based on breathing unit, it is characterised in that institute It is identical as breathing unit pipeline inside dimension to state frequency conversion axial flow fan full-size.