CN207672430U - Half parallel steel wire suspension cable double helix structure of diameter 120mm hot extruded polyethylenes - Google Patents

Abstract

The utility model discloses a double-helix structure of a hot-extruded polyethylene semi-parallel steel wire cable-stayed cable with a diameter of 120 mm, which belongs to the field of cable-stayed bridges. A raised double helix is wound on the outer surface of the stay cable. When the helix diameter d=1.2mm, the maximum winding distance of the same helix is S=6D; when the helix diameter d=1.6mm, the same helix The maximum winding distance is S=12D; when the diameter of the helix is d=2.0mm, the maximum winding distance of the same helix is S=12D; D is the diameter of the stay cable. The utility model can not only suppress wind and rain vibration, but also have the best aerodynamic resistance.

Description

Diameter 120mm heat-extruded polyethylene semi-parallel steel wire stay cable double helix structure

technical field

The utility model belongs to the engineering technical field of cable-stayed bridges, in particular to a double-helix structure of hot-extruded polyethylene semi-parallel steel wire cable-stayed cables with a diameter of 120 mm, which can suppress wind and rain vibration and has the best aerodynamic resistance effect.

Background technique

Cable-stayed cables are one of the main stress-bearing components of cable-stayed bridges. Currently, hot-extruded PE semi-parallel steel wire cable-stayed cables are the most commonly used cable-stayed cables. A large number of studies have shown that: in a specific wind and rain environment, stay cables often vibrate greatly, which is named wind and rain vibration or wind and rain induced vibration. When wind and rain vibration occurs, the vibration of the stay cable can cause damage to the anchorage area of the cable beam and the anchorage area of the cable tower, cause fatigue damage to the joints at the end of the cable, and damage the anti-corrosion system of the stay cable. The cable fails. At the same time, the vibration will cause the friction and misalignment between the steel wires inside the cable stay, damage the anti-corrosion material on the surface of the steel wires, and reduce the fatigue strength of the corroded steel wires. In addition, the damping devices used for wind and rain vibration damping are often damaged by the large vibrations of the stay cables.

In order to suppress the occurrence of this vibration, the commonly used methods are mechanical measures (setting dampers, etc.), structural measures (setting auxiliary cables, etc.) and pneumatic measures. With the increase of the span of the cable-stayed bridge, the length of the cable-stayed cables also increases, and the effect of installing dampers at the ends of the cables is limited; using auxiliary cables to connect the cable-stayed cables will destroy the overall appearance, so This measure is used less frequently; pneumatic measures are considered to be the practicable method.

Since the wind load on the cables of long-span cable-stayed bridges accounts for the main part of the wind load on the whole bridge, the change of the aerodynamic resistance on the cables after adopting aerodynamic measures is also an important consideration in bridge design. Reducing the aerodynamic resistance on the stay cables can maximize the stress safety of the bridge while saving costs. However, the existing aerodynamic measures only consider the vibration suppression effect, and do not consider the change of aerodynamic resistance after the measures are taken.

Utility model content

The technical problem to be solved by the utility model is to provide a double-helix anti-wind and rain vibration-resistant cable with a diameter of 120mm hot-extruded polyethylene semi-parallel steel wire cable, which can not only suppress the wind and rain vibration, but also have the best aerodynamic resistance.

In order to solve the above-mentioned technical problems, the technical solution adopted by the utility model is: a double-helix structure of a hot-extruded polyethylene semi-parallel steel wire stay cable with a diameter of 120mm, and a raised double helix is wound on the outer surface of the stay cable , when the diameter of the helix is d=1.2mm, the maximum winding distance of the same helix is S=6D; when the diameter of the helix is d=1.6mm, the maximum winding distance of the same helix is S=12D; the diameter of the helix is d=2.0mm , the maximum winding pitch of the same helix is S=12D; D is the diameter of the stay cable.

Further technical solutions that can be adopted, when d=1.6mm, S=6D.

In a further technical solution, the double helix is helically wound in the same direction.

The beneficial effects produced by adopting the above technical scheme are: the utility model is an aerodynamic measure for the hot-extruded PE semi-parallel steel wire cable with a diameter of 120mm, which has a good vibration suppression effect and aerodynamic resistance characteristics. is the effect of the helix spacing S and diameter d on the aerodynamic resistance of the 120mm cable, so that the cable with a diameter of 120mm can achieve the minimum aerodynamic resistance on the premise of a good vibration suppression effect.

Description of drawings

Fig. 1 is the structural representation of the utility model embodiment;

Fig. 2 is the structural representation of the cross-section of the utility model;

In the figure: 1. Stay cable; 2. Spiral wire; 3. PE wrapped sheath; 4. Steel wire anti-corrosion protection layer; 5. Steel wire grease protection layer.

Detailed ways

Below in conjunction with accompanying drawing and specific embodiment, the utility model is described in further detail.

Referring to the accompanying drawing 1 of the utility model, a raised double helix is wound on the outer surface of the stay cable 1. When the diameter of the helix 2 is d=0.8mm, the maximum winding distance of the same helix 2 is S=12D; the helix 2 When the diameter d=1.2mm, the maximum winding distance of the same helix 2 is S=14D, and D is the diameter of the stay cable 1.

In addition, when d=0.8mm, S=10D can suppress wind and rain vibration; when d=1.2mm, S=12D can also suppress wind and rain vibration.

In a further technical solution, the double helix is helically wound in the same direction, as shown in FIG. 1 . Fig. 2 is a cross-sectional view of the utility model, the stay cable 1 is a multi-strand steel wire, each steel wire is wrapped with a steel wire grease protective layer 5, the core is wrapped with a steel wire anti-corrosion protective layer 4, and the outermost layer is a hot-extruded PE wrapped sheath 3. The helical wire is wrapped outside the PE wrapping sheath.

In order to study the influence of the helix spacing S and diameter d on the aerodynamic drag on the cable with a diameter of 120 mm, a wind tunnel test simulating a real scene was carried out. The wind tunnel tests are carried out in the wind laboratory's atmospheric boundary layer wind tunnel. The wind tunnel is a back/direct boundary layer wind tunnel with double test sections in series. The low-speed test section is 4.4 meters wide, 3 meters high, and 24 meters long, with a maximum wind speed of over 30 m/s; the high-speed test section is 2.2 meters wide, 2 meters high, and 5 meters long, with a maximum wind speed of over 80 m/s. good. The rainfall equipment is completed by a specially customized rainfall simulation system, which consists of a control system (open-loop or closed-loop control can be realized), a water supply system, and a sprinkler system. The sprinkler system consists of 4 groups of 12 different calibers in different spatial positions The sprinkler head composition, through the control system to adjust the pressure, can accurately simulate the rainfall of all levels of rainfall intensity from 10mm/h to 240mm/h, and at the same time keep consistent with the natural rainfall in terms of raindrop spectrum and other characteristics. The accuracy of rainfall intensity is 2%, and the rainfall range is 4m wide and 4m long downwind.

In order to compare the vibration suppression results of the helix, the influence of wind speed, rainfall, inclination angle, wind direction angle and other factors in the test was firstly studied, and the parameter setting when the amplitude of the cable without helix was the largest was found. Based on these test parameters, helixes with different diameters and different spacings were wound on the stay cables successively, and the influence of helix spacing S and diameter d on the vibration suppression effect was investigated, and a parameter combination with good vibration suppression effect was found. Furthermore, the effects of the helix spacing S and diameter d on the aerodynamic drag were studied through dynamometric tests, and the parameter combination with the smallest aerodynamic drag was found on the premise of satisfying the vibration suppression effect.

The utility model considers two key factors: first, the wind and rain vibration can be suppressed; second, among all the parameters that can achieve the vibration suppression effect, the parameter with the smallest aerodynamic resistance is selected as the aerodynamic measure of the utility model.

The principle of the utility model: in a specific wind and rain environment, a waterline will be formed on the surface of the stay cable, and the formation of the waterline changes the circular section of the stay cable, making the section of the stay cable with the waterline become aerodynamically unstable section, resulting in vibration. The purpose of the winding helix is to prevent the formation of a continuous waterline.

Specific parameters: For a stay cable with a diameter of 120mm, a double helix is wound on the outer surface of the stay cable. The diameter of the helix is 1.2mm. mm, the maximum winding spacing that can suppress wind and rain vibration is 12 times the diameter of the stay cable; when the diameter of the helix is 2.0 mm, the maximum winding spacing that can suppress wind and rain vibration is 12 times the diameter of the stay cable.

Table 1 is a list of different helix parameter combinations that can suppress the vibration of the stay cable (diameter 120mm)

What needs to be emphasized is that the occurrence of wind and rain vibration can only be suppressed under the appropriate parameter combination, and the inappropriate parameter combination not only cannot suppress the occurrence of vibration, but stimulates the occurrence of vibration. A large number of studies have shown that with the helix spacing S and the helix diameter d as parameters, there are many combinations that can satisfy the vibration suppression effect. Which helix parameter is selected as a vibration suppression measure in actual engineering must consider the influence of the helix parameter on the aerodynamic resistance of the stay cable, and try to minimize the aerodynamic resistance on the stay cable.

Research shows that under the same parameters, increasing the diameter of the helix alone can also have the effect of suppressing vibration; reducing the winding distance alone can also have the effect of suppressing vibration. For example, in Table 1, d=1.6mm, S=12D can suppress vibration; d=2.0mm, S=12D can also suppress vibration; d=1.6mm, S=6D can also suppress vibration.

According to the "Code for Wind Resistance Design of Highway Bridges", the wind load on bridge components other than the main girder generally only considers the resistance in the direction of wind action. Calculate the aerodynamic resistance on the helical cables wound with different parameters according to the method specified in the code, and select the helical parameters that minimize the aerodynamic resistance for winding.

In the calculation of aerodynamic drag, the Reynolds number effect needs to be considered for stay cables with circular cross-sections. In the region of subcritical Reynolds number, the drag coefficient basically does not change with the change of Reynolds number; in the region of critical Reynolds number, the drag coefficient decreases with the increase of Reynolds number. For the same stay cable and the same air conditions, the Reynolds number is proportional to the wind speed, so in the critical Reynolds number region, the drag coefficient decreases with the increase of the wind speed, because the aerodynamic drag is proportional to the square of the wind speed and the drag coefficient , the drag coefficient decreases as the wind speed increases, so that the aerodynamic drag corresponding to the maximum wind speed is not necessarily the maximum aerodynamic drag in the entire wind speed range. The calculation method of the maximum aerodynamic drag is described below.

First, according to the basic wind speed V ₁₀ or the design wind speed V _s10 at the bridge site, and the reference height of the stay cables of the cable-stayed bridge, determine the wind speed V _z and the static gust speed V _g at the reference height Z.

Second, calculate the Reynolds number of the stay cable according to the static gust wind speed V _g and the annual average temperature, humidity and air pressure, , where U is the incoming wind speed, in m/s, D is the diameter of the stay cable model, in m, is the air kinematic viscosity coefficient; ,in is the density of air, unit kg/m ³ , is the aerodynamic drag viscosity coefficient.

Third, according to the diameter of the stay cable and the parameters of the helix with vibration suppression effect, as well as the value of the calculated Reynolds number, through Table 2, determine the area where the Reynolds number is located.

Table 2 Reynolds number partitions of helical stay cables (with a diameter of 120mm) wound with different parameters (Reynolds number unit: 10 ⁴ )

Note: "/" is a combination of parameters without vibration suppression effect

Fourth, if the Reynolds number corresponding to the static gust wind speed V _g is in the subcritical region, look up Table 3 to obtain the drag coefficient corresponding to the stay cable, and calculate the aerodynamic resistance corresponding to the static gust wind speed V _g according to formula (1), and calculate the Aerodynamic drag is taken as the maximum aerodynamic drag over the entire range of wind speeds from low to _Vg .

Table 3 Statistical table of resistance coefficients of helical stay cables (diameter 120 mm) wound with different parameters

Note: "/" is a combination of parameters without vibration suppression effect

(1)

In the formula: —Air density (kg/m ³ )

V _g — static gust wind speed

C _D —the resistance coefficient of the cable-stayed bridge

A _n —the downwind projected area of the bridge stay cable (m ² ); its diameter multiplied by its projected height

Or in the supercritical region, look up Table 3 to obtain the resistance coefficient corresponding to the stay cable.

Fifth, if the Reynolds number corresponding to the static gust wind speed V _g is in the critical region, the drag coefficient is calculated by fitting the quartic function formula (2), and the parameters a, b, c, d, and e in the formula can be obtained through the lookup table 4 get.

(2)

Table 4 Calculation parameter table of resistance coefficient of helical cable with different parameters (diameter 120mm)

According to Table 2, Table 3 and formula (2), respectively determine the C _D corresponding to the subcritical and critical Reynolds numbers, draw the change curve of _CD with Reynolds number, and calculate and draw the aerodynamic Drag curve with wind speed from low to V _g , find the maximum aerodynamic drag in this curve, as the maximum aerodynamic drag in the whole range of wind speed from low to V _g .

Sixth, if the Reynolds number corresponding to the static gust wind speed V _g is in the supercritical region, determine the C _D corresponding to the subcritical, critical and supercritical Reynolds numbers respectively through Table 3 and the fifth step above, and draw the relationship between C _D and Reynolds number Change curve, according to this curve and formula (1), calculate and draw the change curve of aerodynamic resistance with wind speed from low to V _g , find the maximum aerodynamic resistance in this curve, as the whole wind speed range from low to V _g the maximum aerodynamic drag.

Re-select other helical parameter combinations that can suppress vibration, repeat the third to fifth steps above, and obtain the maximum aerodynamic resistance of the stay cable for each set of helical parameters, and select a set of helical parameters with the smallest maximum aerodynamic resistance value, and That is, the combination of helix parameters when the aerodynamic resistance is the smallest is used as the optimized helix parameters.

Compared with the prior art, the utility model has the following remarkable points:

After winding the helical wire on the surface of the stay cable, it can prevent the formation of continuous water line and achieve the effect of damping wind and rain vibration. After winding the selected optimal helix, compared with the case of winding other helixes, the aerodynamic resistance of the stay cable is the smallest.

Claims (1)

1. a kind of half parallel steel wire suspension cable double helix structure of diameter 120mm hot extruded polyethylenes, which is characterized in that in suspension cable (1) bifilar helix of protrusion, the bifilar helix spiral winding in the same direction, helix (2) diameter d=are wound on outer surface When 1.2mm, the maximum winding spacing of same helix (2) is S=6D；When helix (2) diameter d=1.6mm, same helix (2) maximum winding spacing is S=12D；When helix (2) diameter d=2.0mm, the maximum winding spacing of same helix (2) For S=12D；D is the diameter of suspension cable (1), D=120mm；

Design parameter：For the suspension cable of diameter 120mm, bifilar helix is wound in suspension cable outer surface, helix is a diameter of 1.2mm, it is 6 times of suspension cable diameters, i.e. S=720mm that can inhibit the maximum winding spacing that wind and rain shakes；Helix is a diameter of 1.6mm, it is 12 times of suspension cable diameters, i.e. S=1440mm that can inhibit the maximum winding spacing that wind and rain shakes；Helix is a diameter of It is 12 times of suspension cable diameters, i.e. S=1440mm that can inhibit the maximum winding spacing that wind and rain shakes in the case of 2.0mm；

The suspension cable (1) is steel wire strand, per share steel wire outer wrapping steel wire grease protective layer (5), core outer wrapping steel wire anti-corrosion Protective layer (4), outermost layer are hot extrusion PE wrap jackets (3), and helix (2) is wrapped in PE wrap jackets (3) outside.