A measuring device and method for measuring relative slip between cable-stayed bridge cables and towers

Abstract

The present invention proposes a measuring device and method for measuring the relative slip between a cable-stayed bridge cable and a tower, wherein the measuring device includes a displacement sensor, a DTU, a steel clamp, and a flexible steel wire; the displacement sensor is installed on the tower and is located directly above the connection between the cable and the tower, and the displacement sensor is connected to the terminal device of the peripheral device through the DTU; the measuring line of the displacement sensor is fixed to one end of the flexible steel wire, and the other end of the flexible steel wire is connected to the cable, which is close to the displacement sensor; the steel clamp simultaneously clamps the cable and the flexible steel wire to fix the flexible steel wire on the cable, and the measuring line of the flexible steel wire and the displacement sensor are on the same straight line. Based on the above-mentioned measuring device, the present invention also provides a corresponding measuring method to detect the relative slip between the cable-stayed bridge cable and the tower in real time, so that timely measures can be taken when large relative slip is detected to avoid bridge safety problems.

Description

Technical Field

[0001] The present invention belongs to the technical field of inclined bridge monitoring, and in particular relates to a measuring device and method for measuring relative slippage between a cable and a tower of a cable-stayed bridge. Background Art

[0002] Cable-stayed bridges are widely used in transportation construction due to their large spanning capacity, reasonable structural stress, and beautiful appearance. The most important force-transmitting component of a cable-stayed bridge is the cable. Usually, when the tower is relatively short, the cable is often connected to the tower to offset the unbalanced forces on both sides of the tower under its own load and external load. Therefore, the free sliding of the cable body at the contact point with the tower is a necessary condition to ensure the safe and stable operation of this type of bridge. However, due to the characteristics of the cable body being wrapped with a protective sheath on the outside and the complex structure of the cable-tower connection, it is very difficult to monitor the relative slip between the cable and the tower. At present, there is no corresponding technology for monitoring this content at home and abroad. In order to solve this problem, the present invention proposes a measuring device and method for measuring the relative slip between the cable and the tower of a cable-stayed bridge, so as to detect the relative slip between the cable and the tower in real time, so that timely measures can be taken when a large relative slip is detected to avoid bridge safety problems. Summary of the Invention

[0003] In order to achieve the above object, the technical solution adopted by the present invention is:

[0004] A measuring device for measuring the relative slip between a cable-stayed bridge cable and a tower, comprising a displacement sensor, a DTU, a steel clamp, and a flexible steel wire; the displacement sensor is mounted on the tower and located directly above the connection between the cable and the tower; the displacement sensor is connected to a peripheral terminal device via the DTU; a measuring line of the displacement sensor is fixedly connected to one end of the flexible steel wire, the other end of the flexible steel wire is connected to the cable, which is located closest to the displacement sensor; the steel clamp simultaneously clamps the cable and the flexible steel wire to secure the flexible steel wire to the cable, and the flexible steel wire and the measuring line of the displacement sensor are in a straight line.

[0005] Preferably, the installation position of the displacement sensor is 0.5m-1m away from the connection point between the cable and the tower.

[0006] Preferably, the displacement sensor is a linear displacement sensor.

[0007] Preferably, the distance between the connection point between the flexible steel wire and the cable and the connection point between the cable and the tower is 2m-3m.

[0008] Preferably, the length of the flexible steel wire is 0.2m-0.3m.

[0009] Preferably, the flexible steel wire is bundled and connected to the steel bars inside the cable through holes opened on the cable.

[0010] Based on the above-mentioned measuring device, the present invention also provides a method for measuring the relative slip between the cable and the tower of a cable-stayed bridge, comprising the following steps:

[0011] Step 1: Drill holes on the cables, 2m-3m away from the connection between the cables and the tower;

[0012] Step 2: Tie one end of the flexible steel wire to the internal steel bar of the cable at the drilled hole, and then use a steel clamp to reinforce the connection between the flexible steel wire and the cable-stayed bridge cable;

[0013] Step 3: Install the displacement sensor connected to the DTU on the tower, directly above the cable and 0.5m-1m away from the connection between the cable and the tower;

[0014] Step 4: Pull out the measuring line from the displacement sensor, adjust the angle so that the measuring line and the flexible steel wire are always in a straight line, and then connect the measuring line to the other end of the flexible steel wire;

[0015] Step 5: Measure the angle β between the cable connected to the flexible steel wire and the tower;

[0016] Step 6: The displacement sensor and DTU are running. The displacement sensor obtains the initial value of the measurement line stretch and the subsequent real-time stretch data, and transmits it to the cloud through the DTU.

[0017] Step 7: The terminal device obtains data through the cloud and calculates the relative slip b1 between the cable-stayed bridge cable and the tower using the following formula:

[0018]

[0019] Where,

[0020] a is the height of the displacement sensor installation position from the connection between the cable and the tower,

[0021] β is the angle between the cable and the tower of the cable-stayed bridge,

[0022] c is the length of the flexible steel wire,

[0023] S1 is the initial value of the measuring line stretch in the initial state of the displacement sensor,

[0024] S2 is the real-time value of the stretching of the measuring line after the relative displacement between the cable and the tower occurs.

[0025] Preferably, in step 1, the diameter of the drilled hole is slightly larger than the diameter of the flexible steel wire.

[0026] Preferably, in step 2, after the flexible steel wire is connected to the cable, a sealing treatment is performed at the connection between the flexible steel wire and the cable.

[0027] Preferably, in step seven, considering that the displacement sensor is outdoors, temperature changes may cause the length of the displacement sensor's measuring line and the flexible steel wire to change. Therefore, temperature correction is required. After temperature correction, the calculation formula for the relative slip b1 between the cable-stayed bridge cable and the tower is as follows:

[0028]

[0029] Where α1 is the thermal expansion coefficient of the displacement sensor measuring line, α2 is the thermal expansion coefficient of the flexible steel wire, and △t is the temperature change compared to the initial state after relative slip occurs at a certain moment.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The present invention proposes a device and method for measuring the relative slip between the cables and towers of a cable-stayed bridge. The device and method can detect the relative slip between the cables and towers of a cable-stayed bridge in real time, thereby facilitating timely measures when a large relative slip is detected, thereby avoiding safety problems of the cable-stayed bridge.

[0032] 2. The measuring device of the present invention can be applied to cable-stayed bridges of various sizes, has a simple structure, and is easy to construct. The proposed measuring method is also applicable to cable-stayed bridges of various sizes, has simple calculations, is easy to operate, and has high promotion value.

[0033] 3. The measurement method of the present invention also takes into account the influence of temperature change on the test results. Therefore, the data obtained by this method has higher accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic structural diagram of the measuring device of the present invention when installed.

[0035] Figure 2 It is a calculation model diagram of the present invention, wherein Figure (a) is a schematic diagram in the initial state, and Figure (b) is a schematic diagram after relative displacement occurs.

[0036] Description of main component symbols

[0037] In the figure: displacement sensor 1, measuring line 2, flexible steel wire 3, steel clamp 4, cable 5, tower 6.

[0038] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0039] See also Figure 1In a preferred embodiment of the present invention, a measuring device for measuring the relative slippage between a cable-stayed bridge cable and a tower includes a displacement sensor 1, a DTU, a steel clamp 4, and a flexible steel wire 3. The displacement sensor 1 is installed on the tower 6 and is located directly above the connection between the cable 5 and the tower 6. The displacement sensor 1 is connected to the terminal device of the peripheral device through the DTU. The measuring line 2 of the displacement sensor 1 is fixedly connected to one end of the flexible steel wire 3, and the other end of the flexible steel wire 3 is connected to the cable 5. The cable 5 is close to the displacement sensor 1. Preferably, the steel clamp 4 simultaneously clamps the cable 5 and the flexible steel wire 3 to fix the flexible steel wire 3 on the cable 5, and the flexible steel wire 3 and the measuring line 2 of the displacement sensor 1 are on the same straight line.

[0040] The present invention uses a displacement sensor 1 to measure the stretched length of its measuring line 2. The length of the flexible steel wire 3, which remains unchanged throughout the test, the angle between the cable 5 and the tower 6, and the height of the displacement sensor 1 installed on the tower 6 relative to the connection between the cable 5 and the tower 6 are then combined to determine the length of the cable 5 between the fixed point of the steel clamp 4 and the connection between the cable 5 and the tower 6 before and after the relative slip between the cable 5 and the tower 6. By calculating the change in the length of the cable 5 between the fixed point of the steel clamp 4 and the connection between the cable 5 and the tower 6 before and after the change, the relative slip between the cable 5 and the tower 6 can be determined. Based on the above measurement principle, the displacement sensor 1 used in the present invention is a linear displacement sensor 1 that converts linear mechanical displacement into an electrical signal, which can directly determine the value of the change in the measuring line 2. A linear displacement sensor 1 with an accuracy of 0.05% is preferably selected to ensure measurement accuracy.

[0041] Furthermore, in the present invention, the installation height of the displacement sensor 1 should not be too large or too small. If it is installed too high, the initial pull-out size of the subsequent measuring line 2 will change too much relative to the size of the subsequent measuring line 2, which is prone to large errors. If it is installed too low, the angle is not obvious, which is also prone to large errors. Therefore, in order to improve the accuracy of the measurement, this embodiment makes the installation position of the displacement sensor 1 0.5m-1m away from the connection between the cable 5 and the tower 6; similarly, for the accuracy of the measurement, the length of the flexible steel wire 3 should not be too large or too small. If the value is too small, the flexible steel wire 3 is not easy to connect with the cable 5 and the measuring line 2, and the anti-corrosion effect of the cable 5 is not achieved. If the value is too large, it is difficult to control the flexible steel wire 3 to be in a straight line with the line during the movement of the cable, resulting in inaccurate measurement results. Therefore, in this embodiment, the length of the flexible steel wire 3 is 0.2m-0.3m; the distance between the connection between the flexible steel wire 3 and the cable 5 and the connection between the cable 5 and the tower 6 is 2m-3m.

[0042] In addition, it should be noted that the present invention uses one end of the flexible steel wire 3 to connect with the cable 5 of the cable-stayed bridge, and the reason for not allowing the measuring line 2 to be directly connected to the cable 5 is to prevent the internal steel bars of the cable 5 from being directly exposed to the air due to the connection with the measuring line 2, thereby reducing the corrosion of the cable 5. At the same time, allowing the measuring line 2 to be directly connected to one end of the flexible steel wire 3 also facilitates the replacement of the displacement sensor 1 in the future. That is, when the flexible steel wire 3 of the present invention is connected to the cable 5, the flexible steel wire 3 is bundled and connected to the steel bars inside the cable 5 through the hole opened on the cable 5, thereby realizing the connection between the flexible steel wire 3 and the cable 5. Secondly, the size of the steel clip 4 needs to match the size of the measured cable 5, and the durability should be good. In addition, in this measuring device, the data measured by the displacement sensor 1 is transmitted to the cloud through the DTU, and the terminal device obtains the data through the cloud for calculation. In the present invention, the DTU (Data Transfer Unit) is a wireless terminal device specifically used to convert serial port data into IP data or convert IP data into serial port data for transmission through a wireless communication network. The present invention can adopt any DTU device suitable for the displacement sensor 1, and it can be connected to the interface of the displacement sensor 1.

[0043] Based on the above-mentioned measuring device, the present invention also provides a method for measuring the relative slip between the cable and the tower of a cable-stayed bridge, comprising the following steps:

[0044] Step 1: Drill a hole on the cable 5, and the drilling position is 2m-3m away from the connection between the cable 5 and the tower 6; preferably, the diameter of the drilled hole is slightly larger than the diameter of the flexible steel wire 3, that is, the size of the drilled hole should be close to the diameter of the flexible steel wire 3, and cannot be too large or too small, because if the hole diameter is too large, the steel bars inside the cable 5 are directly exposed to the air, which accelerates corrosion, and if the hole diameter is too small, it is difficult to connect the flexible steel wire 3 to the cable 5.

[0045] Step 2: Tie one end of the flexible steel wire 3 to the internal steel bars of the cable 5 at the drilled hole position, and then use the steel clamp 4 to reinforce the connection between the flexible steel wire 3 and the cable-stayed bridge cable; preferably, after the flexible steel wire 3 is connected to the cable 5, the connection between the flexible steel wire 3 and the cable 5 is sealed to avoid the drilled steel bars being exposed to the air and to prevent the steel bars in the cable 5 from corroding too quickly, wherein the sealing method can be concrete sealing or other sealing methods.

[0046] Step 3: Install the DTU-connected displacement sensor 1 on tower 6, directly above the cable 5 and 0.5-1m from the connection between the cable 5 and tower 6. The installation height of the displacement sensor 1 should be neither too high nor too low. If it is installed too high, the initial pull-out dimension of the subsequent measurement line 2 will vary greatly relative to the subsequent measurement line 2, which can easily lead to large errors. If it is installed too low, the angle will not be obvious, which can also easily lead to large errors. It should be noted that the method of installing the displacement sensor 1 on the tower 6 is not limited in the present invention; it only needs to ensure that it is firmly installed and not easily fall off.

[0047] Step 4: Pull out the measuring line 2 in the displacement sensor 1, adjust the angle so that the measuring line 2 and the flexible steel wire 3 are always in a straight line, and then connect the measuring line 2 to the other end of the flexible steel wire 3. The connection method between the measuring line 2 and the flexible steel wire 3 is not limited in the present invention. It can be a binding method or other methods, as long as it is guaranteed to be firm.

[0048] Step 5: Measure the angle β between the cable 5 connected to the flexible steel wire 3 and the tower 6;

[0049] Step 6: Displacement sensor 1 and DTU are running. Displacement sensor 1 obtains the initial value of the stretch of measuring line 2 and the subsequent real-time stretch data, and transmits it to the cloud through DTU.

[0050] Step 7: The terminal device obtains data through the cloud and calculates the relative slip b1 between the cable-stayed bridge cable and the tower 6 using the following formula:

[0051]

[0052] Where,

[0053] a is the height of the installation position of the displacement sensor 1 from the connection between the cable 5 and the tower 6,

[0054] β is the angle between the cable 5 and the tower 6 of the cable-stayed bridge,

[0055] c is the length of the flexible steel wire 3,

[0056] S1 is the initial value of the stretching of the measuring line 2 in the initial state of the displacement sensor 1,

[0057] S2 is the real-time value of the stretching of the measuring line 2 after the relative displacement between the cable 5 and the tower 6 occurs.

[0058] The above calculation formula is based on the measurement principle mentioned above. Figure 2 , giving the specific calculation process of the present invention:

[0059] (1) Reference Figure 2 In Figure (a), first calculate the length b of the cable 5 between the fixed point of the steel clamp 4 and the connection point between the cable 5 and the tower 6 in the initial state. According to the triangle cosine theorem,

[0060] L1=b 2 +a 2 -2abcosβ, (1)

[0061] Wherein, L1 is the distance between the fixed point of the steel clamp 4 and the displacement sensor 1 on the tower 6 in the initial state, L1=c+S1(2)

[0062] a is the height of the installation position of the displacement sensor 1 from the connection between the cable 5 and the tower 6,

[0063] β is the angle between the cable 5 and the tower 6 of the cable-stayed bridge,

[0064] c is the length of the flexible steel wire 3,

[0065] S1 is the initial value of the stretch of the measuring wire 2 in the initial state of the displacement sensor 1.

[0066] Based on formula (1),

[0067]

[0068] Since b>0 always holds, and L1>a, we have

[0069]

[0070] (2) Reference Figure 2 Calculate the length b+b1 (b1 is the relative slip between the cable-stayed bridge cable and the tower 6) of the cable 5 between the fixed point of the steel clamp 4 and the connection point of the cable 5 and the tower 6 after relative slip occurs at a certain moment. The calculation method is the same as (a), and we can get:

[0071]

[0072] Among them, L2 is the distance between the fixed point of the lower steel clamp 4 and the displacement sensor 1 on the tower 6 after relative sliding, L2 = c + S2 (6), S2 is the real-time value of the stretching of the measuring line 2 after the relative displacement between the cable 5 and the tower 6, that is, the value displayed by the displacement sensor 1.

[0073] Based on formula (4) and formula (5), we can get

[0074]

[0075] Substituting equations (2) and (6) into equation (7), we can obtain the relative slip b1 between the cable-stayed bridge and the tower 6:

[0076]

[0077] Furthermore, considering that the displacement sensor 1 is located outdoors, temperature changes will cause the lengths of the displacement sensor 1's measuring wire 2 and flexible steel wire 3 to change, so temperature correction is required. Assume that the thermal expansion coefficient of the displacement sensor 1's measuring wire 2 is α1, the thermal expansion coefficient of the flexible steel wire 3 is α2, and the temperature change after relative slip at a certain moment is △t compared to the initial state, then

[0078] The elongation of the line after displacement is δ1=S2α1△t,

[0079] The elongation of the flexible steel wire 3 after displacement is δ2=α2c△t,

[0080] That is, L2=c+S2+α1cΔt+α2S2Δt(9).

[0081] Substituting equations (2) and (9) into equation (7), we obtain the calculation formula for the relative slip b1 between the cable-stayed bridge and the tower 6 after temperature correction:

[0082]

[0083] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for measuring relative slip between a cable-stayed bridge cable and a tower, characterized by: A measuring device for measuring the relative slip between a cable-stayed bridge cable and a tower is used for measurement. The measuring device includes a displacement sensor, a DTU, a steel clamp, and a flexible steel wire. The displacement sensor is installed on the tower and located directly above the connection between the cable and the tower. The displacement sensor is connected to an external terminal device via the DTU. The measuring line of the displacement sensor is fixedly connected to one end of the flexible steel wire, and the other end of the flexible steel wire is connected to the cable, which is close to the displacement sensor. The steel clamp simultaneously clamps the cable and the flexible steel wire to fix the flexible steel wire to the cable. The flexible steel wire and the measuring line of the displacement sensor are in a straight line. The measuring method comprises the following steps: Step 1: Drill holes on the cables, 2m-3m away from the connection between the cables and the tower; Step 2: Tie one end of the flexible steel wire to the internal steel bar of the cable at the drilled hole, and then use a steel clamp to reinforce the connection between the flexible steel wire and the cable-stayed bridge cable; Step 3: Install the displacement sensor connected to the DTU on the tower, directly above the cable and 0.5m-1m away from the connection between the cable and the tower; Step 4: Pull out the measuring line from the displacement sensor, adjust the angle so that the measuring line and the flexible steel wire are always in a straight line, and then connect the measuring line to the other end of the flexible steel wire; Step 5: Measure the angle β between the cable connected to the flexible steel wire and the tower; Step 6: The displacement sensor and DTU are running. The displacement sensor obtains the initial value of the measurement line stretch and the subsequent real-time stretch data, and transmits it to the cloud through the DTU. Step 7: The terminal device obtains data through the cloud and calculates the relative slip b1 between the cable-stayed bridge cable and the tower using the following formula: Where, a is the height of the displacement sensor installation position from the connection between the cable and the tower, β is the angle between the cable and the tower of the cable-stayed bridge, c is the length of the flexible steel wire, S1 is the initial value of the measuring line stretch in the initial state of the displacement sensor, S2 is the real-time value of the stretching of the measuring line after the relative displacement between the cable and the tower occurs.

2. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: The installation position of the displacement sensor is 0.5m-1m away from the connection point between the cable and the tower.

3. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: The displacement sensor is a linear displacement sensor.

4. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: The distance between the connection point between the flexible steel wire and the cable and the connection point between the cable and the tower is 2m-3m.

5. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: The length of the flexible steel wire is 0.2m-0.3m.

6. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: The flexible steel wire is bound and connected to the steel bars inside the cable through the holes opened on the cable.

7. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: In step 1, the diameter of the drilled hole is slightly larger than the diameter of the flexible steel wire.

8. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: In step 2, after the flexible steel wire is connected to the cable, a sealing process is performed at the connection between the flexible steel wire and the cable.

9. The method for measuring relative slip between a cable-stayed bridge cable and a tower according to claim 1, wherein: In step 7, considering that the displacement sensor is outdoors, temperature changes will cause the length of the displacement sensor's measuring line and flexible steel wire to change. Therefore, temperature correction is required. After temperature correction, the calculation formula for the relative slip b1 between the cable-stayed bridge cable and the tower is as follows: Where α1 is the thermal expansion coefficient of the displacement sensor measuring line, α2 is the thermal expansion coefficient of the flexible steel wire, and Δt is the temperature change compared to the initial state after relative slip occurs at a certain moment.

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