CN102286919A - Cable-stayed bridge cable capable of inhibiting dry-cable galloping and rain-wind induced vibration - Google Patents

Abstract

The invention relates to a stay cable of a cable-stayed bridge capable of suppressing galloping vibration of dry cables and vibration induced by wind and rain. It is composed of a central wire rope and a surface sheath, and is characterized in that the outer surface of the surface sheath has a helical groove, and the helical groove is a bidirectional helical groove helical in two opposite directions; the bidirectional helical groove Shaped grooves can change the separation point of the boundary layer on the surface of the cable, destroying the occurrence of regular Karman vortex shedding; two grooves rotating in opposite directions can destroy the formation of axial flow and axial vortex along the axial direction of the cable, changing The three-dimensional structure around the cable reduces the aerodynamic force intensity and its correlation along the axial direction of the cable, destroys the conditions for the galloping of the cable dry cable, and suppresses the occurrence of the dry cable phenomenon; The flow path on the surface of the cable prevents the formation of rain lines on the upper surface of the cable, hinders the oscillation of the rain line on the surface of the cable, and avoids wind and rain-induced vibration of the cable.

Description

Cables of cable-stayed bridges capable of suppressing galloping vibrations of dry cables and vibrations induced by wind and rain

technical field

The invention relates to a stay cable of a cable-stayed bridge, in particular to a stay cable of a cable-stayed bridge capable of suppressing galloping vibrations of dry cables and vibrations induced by wind and rain.

Background technique

As the main load-bearing components of cable-stayed bridges, cable-stayed cables have the characteristics of small deadweight, high flexibility, and low damping, so they are prone to vibrations under wind loads. The wind-induced vibration of stay cables has many influencing factors, complex mechanisms, and multiple vibration forms. The common types of wind-induced vibration of stay cables include vortex-induced vibration, wake galloping, wind and rain-induced vibration, and dry cable galloping. Among them, wind-rain-induced vibration occurs under the combined action of wind and rain. Researchers from various countries have conducted extensive research on the phenomenon of wind-rain-induced vibration in the past 20 years. The galloping vibration of dry cables is a large wind-induced vibration that occurs in windy and rainy weather, and is a new form of wind-induced vibration of cables that has only recently been discovered on cable-stayed bridges. The mechanism of galloping vibration of dry cables is different from that of vortex-induced vibration, wake galloping and wind-rain-induced vibration. In order to avoid galloping of dry cables, a new vibration control method is needed.

The large vibration of the cable-stayed cables will cause the fatigue of the cables, fatigue cracks will be generated at the cable-anchor joints, and the damage to the anti-corrosion system of the cables will be caused, which will seriously endanger the safety of the cable-stayed bridge and cause psychological panic for pedestrians. Currently, the commonly used cable vibration control methods are: mechanical control measures, structural control measures and aerodynamic control measures.

Mechanical control measures are a vibration reduction method that increases the damping of the cable structure by installing dampers at both ends of the cable. However, since the galloping vibration of the cable dry cable and the wind and rain excitation vibration are large and low frequency vibrations, ordinary dampers have little effect on their vibration reduction. And as the length of the cable increases, the relative efficiency of the traditional damper will also become lower and lower.

The structural control measure is to use auxiliary cables to connect different cables. The auxiliary cable can increase the vibration frequency of the cable and reduce the amplitude of the cable, but it cannot avoid wind and rain-induced vibration of the cable and galloping of the dry cable, so accidents of fatigue damage of the auxiliary cable often occur.

Aerodynamic control measures mainly improve the aerodynamic performance of the cable by performing special treatment on the surface of the cable, which is considered to be a cost-effective vibration reduction measure. At present, the commonly used aerodynamic damping measures for cables on actual cable-stayed bridges include: setting axial protrusions on the surface of the cables, winding the raised helix on the surface of the cables in one direction, and setting pits on the surface of the cables (respectively see Figure 1, Figure 2 and Figure 3).

The main purpose of the above-mentioned aerodynamic damping measures is to restrain the wind and rain-induced vibration of the cable. However, although the aerodynamic measures of setting axial protrusions on the surface can suppress the occurrence of wind and rain-induced vibration, new aerodynamic instability of the cable will occur under high wind speed. The unidirectional winding of the raised helix on the surface of the cable can destroy the formation of the rain line on the upper surface of the cable, interfere with the oscillation of the rain line on the upper surface of the cable, and reduce the possibility of wind and rain-induced vibration of the cable; The helix increases the windward area of the cable, thereby increasing the drag coefficient of the cable. The aerodynamic measures of setting dimples on the cable surface can increase the roughness of the cable surface, change the fluid separation in the boundary layer of the cable surface; destroy the formation of rain lines on the cable surface, and reduce the possibility of wind and rain-induced vibration of the cable . Nevertheless, it has been found in both wind tunnel tests and actual cable-stayed bridges that wind-rain-induced vibrations sometimes occur on the cables with dimples on the surface. Moreover, recent studies have shown that such a stay cable with dimples on the surface will have a large dry cable gallop in windy and rainy weather; in some cases, the dimples on the surface of the cable will increase the tension Possibility of dry cable galloping.

Therefore, in order to avoid the phenomenon of dry cable galloping and wind and rain-induced vibration of the cables, reduce the possibility of wind-induced vibration of the cables, and improve the safety of cable-stayed cables and cable-stayed bridges, it is necessary to develop new anti-dry cable galloping and wind-induced vibrations. The aerodynamic vibration reduction measures that can suppress wind and rain excitation vibration.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies of the existing cable aerodynamic damping measures, to provide a cable-stayed bridge cable that can suppress the galloping vibration of the dry cable and the wind and rain excitation, and it has a new aerodynamic damping measure. The aerodynamic measures can effectively suppress the dry cable galloping and wind and rain-induced vibration of the cable stays, and at the same time avoid the increase of the drag coefficient of the cables.

In order to solve the above-mentioned technical problems, the concept of the present invention is: on the surface sheath of the stay cable, set up two-way helical grooves along two opposite rotation directions, and set them respectively along the two opposite rotation directions according to actual needs. 1, 2 or more grooves. The pitch of the helical groove can be adjusted, and the pitch is between 1D and 6D (D is the outer diameter of the sheath on the surface of the cable). The shape of the groove can be but not limited to arc shape, rectangle or trapezoid, the width of the groove is 2-5mm, and the depth of the groove is 2-5mm.

The aerodynamic measure of the two-way helical groove can be used alone, and can also be used together with the aerodynamic measure with pits on the surface, that is, pits are set on the surface of the cable with the two-way helical groove.

According to above-mentioned inventive concept, the present invention adopts following technical scheme:

A cable-stayed bridge cable capable of suppressing galloping vibrations of dry cables and wind- and rain-induced vibrations. The groove is a bidirectional helical groove that spirals in two opposite directions; the bidirectional helical groove can change the boundary layer separation point on the surface of the cable and destroy the occurrence of regular Karman vortex shedding; two grooves that rotate in opposite directions , can destroy the axial flow and axial vortex formed along the cable axis, change the three-dimensional structure around the cable, reduce the aerodynamic force intensity and its correlation along the cable axis, and destroy the galloping occurrence of the cable dry cable Conditions to suppress the occurrence of dry cable phenomenon; the two-way spiral groove forms the flow path of rainwater on the surface of the cable, prevents the formation of rain lines on the upper surface of the cable, hinders the oscillation of rain lines on the surface of the cable, and avoids wind and rain on the cable Excitation.

The bidirectional helical grooves have one or more helical grooves in two opposite rotation directions.

The pitch of the spiral groove is 1D~6D, D is the outer diameter of the surface sheath of the cable, the cross-sectional shape of the groove is arc-shaped, rectangular or trapezoidal, the groove width is 2~5mm, and the depth 2~5mm.

Dimples are distributed on the surface of the surface sheath; the dimples increase the surface roughness of the cable, further destroy the formation and oscillation of rain lines on the surface of the cable, and reduce the occurrence probability of galloping and wind-rain-induced vibration of the cable .

Compared with the prior art, the present invention has the following obvious outstanding substantive features and significant advantages:

1) Bidirectional helical grooves can change the separation point of the boundary layer on the surface of the cable, destroying the occurrence of regular Karman vortex shedding; grooves rotating in opposite directions can destroy the formation of axial flow and axial vortex along the axis of the cable. , change the three-dimensional fluid structure around the cable, reduce the aerodynamic force intensity and its correlation along the axial direction of the cable, destroy the occurrence conditions of the galloping vibration of the cable dry cable, and suppress the galloping phenomenon of the dry cable.

2) The two-way helical groove can be used as a flow path for rainwater on the surface of the cable, preventing the formation of rain lines on the upper surface of the cable and hindering the oscillation of rain lines on the surface of the cable. Therefore, in rainy weather, the circular shape of the cable is not changed by the rain line, so as to avoid wind and rain-induced vibration of the cable.

3) Setting pits on the surface of the cable with two-way helical grooves can further destroy the formation and oscillation of the rain line on the upper surface of the cable, improve the surface roughness of the cable, and further reduce the dryness of the cable. Probability of galloping vibration and wind-rain-induced vibration.

4) The aerodynamic measure of setting grooves on the surface of the cable will not increase the windward area of the cable, which can avoid increasing the aerodynamic resistance of the cable.

Description of drawings

Figure 1 is a photo of the cable with axial protrusions on the surface in the past.

Figure 2 is a photo of the conventional one-way winding convex helix cable.

Figure 3 is a photo of the cable with pits set on the surface in the past.

Figure 4 is a schematic diagram of a cable with a bidirectional helical groove in the present invention.

Figure 5 is a schematic diagram of the present invention with two-way helical groove cable.

Figure 6 is a schematic diagram of the three-dimensional structure of the cable with bidirectional spiral grooves and surface pits of the present invention.

Detailed ways

The preferred embodiment of the present invention structural drawings are as follows:

Embodiment one:

Referring to Figure 4, the cables of cable-stayed bridges that can suppress galloping vibrations of dry cables and wind- and rain-induced vibrations are cable-stayed cables with bidirectional helical grooves. Groove, and then open a helical groove on the surface of the cable along the other direction of rotation. One, two or more grooves can be respectively set in the two rotation directions according to actual needs.

The stay cable 1 shown in FIG. 4 is composed of a high-strength galvanized steel wire 2 , a surface sheath 3 and a helical groove 4 from the inside to the outside.

Embodiment two:

This embodiment is basically the same as Embodiment 1, and the special features are:

Referring to Figure 6, the stay cables of the cable-stayed bridge that can suppress the galloping vibration of the dry cables and the wind and rain-induced vibration are stay cables with two-way spiral grooves and surface pits. A helical groove 4 is provided on the surface of the cable along one rotation direction, and finally a helical groove 4 is provided on the surface of the cable along the other rotation direction. One, two or more grooves can be respectively set in the two rotation directions according to actual needs. The pitch of the helical groove 4 is 1D~6D, D is the outer diameter of the surface sheath 2 of the cable 1, the cross-sectional shape of the groove is arc-shaped, rectangular or trapezoidal, and the groove width is 2~6D. 5mm, the depth is 2~5mm.

Embodiment three:

This embodiment is basically the same as embodiment two, and the special features are:

Referring to Fig. 6, the stay cable 1 is composed of a high-strength galvanized steel wire 2 and a surface sheath 3 from the inside to the outside, and the surface sheath 3 has a spiral groove 4 and a pit 5.

Claims (4)

1. cable-stayed bridge cable that can suppress to do Suo Chizhen and rain wind induced vibration, constitute by core wire rope (2) and surperficial sheath (3), the external surface that it is characterized in that described surperficial sheath (3) has helical groove (4), and this helical groove (4) is the bidirectional screw shape groove along two rightabout spirals; This bidirectional screw shape groove can change the boundary layer separation point on drag-line surface, destroys the generation that karman vortex clocklike takes off; The groove of two rightabout rotations, can destroy along drag-line and axially form axial flow and axial whirlpool, change the three-dimensional structure around the drag-line, reduce the pneumatic action force intensity and along the axial correlation of drag-line, destroy drag-line and do the occurrence condition of Suo Chizhen, suppress to do the generation of Suo Xianxiang; Bidirectional screw shape groove constitutes rainwater in the trickling path on drag-line surface, prevents the formation of rain line at the drag-line upper surface, hinders the vibration of rain line on the drag-line surface, avoids drag-line generation rain wind induced vibration.

2. the cable-stayed bridge cable that can suppress to do Suo Chizhen and rain wind induced vibration according to claim 1 is characterized in that described bidirectional screw shape groove is on two opposite direction of rotation one or more helical groove to be arranged respectively.

3. according to the described cable-stayed bridge cable that can suppress to do Suo Chizhen and rain wind induced vibration of claim 1, its feature is 1D ~ 6D in the pitch of described helical groove (4), D is the external diameter of the surperficial sheath (2) of drag-line (1), the shape of cross section of groove is circular arc, rectangle or trapezoidal, this recess width is 2 ~ 5mm, and the degree of depth is 2 ~ 5mm.

4. the cable-stayed bridge cable that can suppress to do Suo Chizhen and rain wind induced vibration according to claim 1 is characterized in that the surface distributed of described surperficial sheath (3) pit (5); This pit (5) has improved the drag-line surface roughness, further destroys formation and the vibration of rain line on the drag-line surface, reduces the probability of happening that drag-line is done Suo Chizhen and rain wind induced vibration.

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