Bridge sling length adjustment device and method of use

Abstract

This invention discloses a bridge cable length adjustment device and its application method, belonging to the field of bridge maintenance technology. The adjustment device includes a shape memory alloy sleeve, which comprises an adjustment section and connecting sections respectively disposed at the upper and lower ends of the adjustment section. The connecting sections have a threaded structure to achieve rotatable connection between the connecting section and the fork plate and anchor cup. A resistance wire is disposed within the adjustment section, with an insulating layer between the resistance wire and the inner wall of the adjustment section. An activation interface is disposed on the side of the adjustment section, with one end of the resistance wire connected to an activation wire, and the other end of the activation wire extending into the activation interface. This invention can accurately achieve automatic adjustment of the cable length, effectively avoiding engineering risks such as cable force deviation or main beam alignment exceeding limits caused by the cumbersome original cable length measurement process.

Description

Technical Field

[0001] This invention relates to a bridge cable length adjustment device and its application method, belonging to the field of bridge maintenance technology. Background Technology

[0002] After decades of development, long-span cable-stayed bridges have gradually entered a critical stage of maintenance, repair, and performance improvement. As the core load-bearing component of such bridges, the durability of the suspenders directly affects the safety and service life of the overall structure. Although the "General Specifications for Design of Highway Bridges and Culverts" (JTG D60-2015) clearly stipulates that the design service life of suspenders should not be less than 20 years, due to long-term exposure to complex natural environments such as acid rain, salt spray, and humidity, coupled with insufficient maintenance and accidental damage, the actual service life of suspenders often fails to meet the design requirements. Therefore, suspender replacement has become an inevitable and necessary engineering measure throughout the entire life cycle of the bridge.

[0003] Unlike constructing new bridges, a core task of cable replacement projects is determining the length of the new cables based on the actual usage condition of the original cables. If the new cable length does not match the original bridge structure, the cable tension or main girder alignment after replacement will exceed the allowable range specified in the standards, potentially leading to the failure of the cable replacement project. However, due to complex traffic loads and the uncertainty of the actual stress state of the cables, accurately measuring the true length of the original cables is extremely difficult, potentially leading to engineering risks such as cable tension deviations or main girder alignment exceeding limits after replacement due to measurement errors. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide a bridge cable length adjustment device and its application method, which can accurately realize the automatic adjustment of cable length and effectively avoid engineering risks such as cable force deviation or main beam alignment exceeding limits caused by the cumbersome original cable length measurement process.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, this invention discloses a bridge cable length adjustment device, comprising a shape memory alloy sleeve. The shape memory alloy sleeve is made of shape memory alloy and can automatically adjust its length upon heating and activation, with the length adjustment amount being positively correlated with temperature. The shape memory alloy sleeve includes an adjustment section and connecting sections respectively disposed at the upper and lower ends of the adjustment section. The connecting sections have a threaded structure to achieve rotatable connection between the connecting sections and the fork plate and anchor cup. A resistance wire is disposed within the adjustment section, and an insulating layer is disposed between the resistance wire and the inner wall of the adjustment section. An activation interface is disposed on the side of the adjustment section, and one end of the resistance wire is connected to an activation wire, the other end of which extends into the activation interface. The bridge cable length adjustment device can adjust the cable length through two methods: rotating the sleeve (coarse adjustment) and energizing for precise adjustment.

[0007] The resistance wire is made of nickel-chromium alloy.

[0008] There are two bridge cable length adjustment devices, and the total adjustment range of the two devices is the length adjustment range that the new cable can achieve. They are divided into an upper cable length automatic adjustment device and a lower cable length automatic adjustment device according to their location. The upper cable length automatic adjustment device is connected to the upper fork lug plate and the upper anchor cup, respectively, and the lower cable length automatic adjustment device is connected to the lower fork lug plate and the lower anchor cup, respectively.

[0009] The shape memory alloy sleeve is hexagonal.

[0010] Secondly, this invention discloses an application method for a bridge suspension cable length adjustment device, comprising the following steps:

[0011] S1, Install a bridge sling length adjustment device on the new sling;

[0012] S2, the original slings are removed using temporary tools and new slings are installed. The adjustment amount of the sling length is calculated based on the actual length of the sling after construction and the design length of the sling in the drawings.

[0013] S3, rotate the shape memory alloy sleeve to roughly adjust the length of the sling, obtain the rough adjustment amount of the sling, and remove the temporary fixture after the rough adjustment is completed so that the new sling can participate in the stress of the bridge structure;

[0014] S4. First, calculate the difference between the sling length adjustment amount and the coarse adjustment amount to obtain the sling precise adjustment amount. Then, determine the heating current and heating time of the resistance wire based on the sling precise adjustment amount to achieve precise adjustment of the sling length. Finally, wait for the shape memory alloy sleeve in the new sling to cool naturally to the ambient temperature.

[0015] The calculation method for the sling length adjustment is as follows:

[0016] (1);

[0017] in, This is the adjustment amount for the sling length. This refers to the actual length of the sling after initial installation. The design length of the slings in the drawing.

[0018] The calculation method for the rough adjustment amount of the sling is as follows:

[0019] (2);

[0020] in, For rough adjustment of the sling, The adjustment coefficient is a rough estimate, specifically the amount of cable length adjustment achieved per 1° rotation of the sleeve, determined through experimentation. The rotation angle of the sleeve.

[0021] The calculation method for the precise adjustment amount of the sling is as follows:

[0022] (3);

[0023] in, For precise adjustment of the slings.

[0024] Precise adjustment of slings Current intensity through external power supply and power-on time Control, its relation is:

[0025] (4);

[0026] in, This refers to the efficiency of heat transfer from the resistance wire to the sleeve. For the pre-tension strain of shape memory alloys, The resistance of the resistance wire. The length of the adjusting section in the shape memory alloy sleeve, For the quality of shape memory alloy sleeves, The specific heat capacity of shape memory alloys, The austenite initiation temperature. This is the austenite termination temperature.

[0027] The beneficial effects of this invention are:

[0028] 1. The cable length automatic adjustment device proposed in this invention has dual adjustment paths. It can achieve coarse adjustment of cable length through the connecting section, and fine adjustment through the combination of the adjustment section and the resistance wire, thereby achieving precise and automatic control of cable length. This method can not only save the tedious original cable length precise measurement process, but also improve engineering efficiency and accuracy.

[0029] 2. During service, when cable force loss or main beam deformation occurs due to reasons such as wire slack or concrete creep, the automatic cable length adjustment device proposed in this invention can use a secondary activation method of heating the resistance wire to accurately compensate for the cable force and quickly adjust the main beam alignment.

[0030] 3. The present invention uses a shape memory alloy sleeve, which can shrink when heated in a high-temperature environment of fire, thereby actively improving the cable force to compensate for the loss of cable force caused by high temperature. This effectively avoids the collapse of the bridge structure caused by the softening or breakage of the suspension cable, and significantly enhances the safety performance of the bridge under extreme working conditions. Attached Figure Description

[0031] Figure 1 This is a longitudinal half-sectional view of the bridge cable length adjustment device of the present invention;

[0032] Figure 2 This is a schematic diagram of the bridge cable length adjustment device applied to the cable in this invention;

[0033] Figure 3 yes Figure 2 Cross-sectional schematic diagram of the lower and middle anchor head section;

[0034] The attached diagram is labeled as follows: 1-Shape memory alloy sleeve; 2-Adjustment section; 3-Connecting section; 4-Resistance wire; 5-Activation wire; 6-Activation interface. Detailed Implementation

[0035] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to illustrate the technical solution of the present invention more clearly, and should not be used to limit the scope of protection of the present invention.

[0036] Example 1

[0037] Shape memory alloys are a class of metallic materials with excellent properties, including high strength, high elastic modulus, good corrosion resistance and fatigue resistance, excellent machinability, stable shape memory effect, and low activation temperature. In recent years, they have been increasingly introduced into the field of bridge engineering. One of their core characteristics is the shape memory effect, which means that after undergoing plastic deformation under external force at room temperature, they can be regenerated to their initial shape through heating or electrical activation. For example... Figure 1As shown, this invention discloses a bridge cable length adjustment device based on the properties of shape memory alloys. The device includes a shape memory alloy sleeve 1, which comprises an adjustment section 2 and connecting sections 3 respectively disposed at the upper and lower ends of the adjustment section 2. The connecting sections 3 have a threaded structure to achieve rotatable connection between the connecting sections 3 and the fork plate and the anchor cup. This invention allows adjustment of the distance between the fork plate and the anchor cup by rotating the shape memory alloy sleeve 1, thereby adjusting the cable length. The shape memory alloy sleeve 1 has a hexagonal exterior, allowing for coarse adjustment of the cable length by rotating the sleeve with a wrench.

[0038] The adjusting section 2 has a vertically continuous channel inside for embedding a heating resistance wire 4. The resistance wire 4 is made of nickel-chromium alloy and generates a large amount of heat when energized, which is used to heat the shape memory alloy sleeve 1. An insulating layer is provided between the resistance wire 4 and the inner wall of the adjusting section 2 to avoid the risk of short circuits. An activation interface 6 is provided on the side of the adjusting section 2. One end of the resistance wire 4 is connected to an activation wire 5, and the other end of the activation wire 5 extends into the activation interface 6. The activation wire 5 and the activation interface 6 are used to connect the resistance wire 4 to an external power source, thus forming a conductive path. After the external power source is connected, the resistance wire 4 is heated, providing the necessary heat for activating the shape memory alloy sleeve 1. When the shape memory alloy sleeve 1 is heated, it automatically retracts to achieve precise adjustment of the sling length. After activation, the activation interface 6 is sealed with a rubber sealing cap.

[0039] like Figure 2 and Figure 3 As shown, there are two bridge cable length adjustment devices, which are divided into an upper cable length automatic adjustment device 7 and a lower cable length automatic adjustment device 8 according to their positions. The upper cable length automatic adjustment device 7 is connected to the upper fork lug 9 and the upper anchor cup 10 respectively, and the lower cable length automatic adjustment device 8 is connected to the lower fork lug 11 and the lower anchor cup 12 respectively.

[0040] Example 2

[0041] This embodiment discloses an application method of a bridge suspension cable length adjustment device based on Embodiment 1, including the following steps:

[0042] Step 1: Install bridge cable length adjustment devices on the new cable. Two bridge cable length adjustment devices are configured. Install an upper automatic cable length adjustment device and a lower automatic cable length adjustment device on the new cable. Note that the shape memory alloy sleeve needs to be pre-deformed during manufacturing; the pre-tensile strain of the shape memory alloy can be determined according to actual requirements.

[0043] Step two involves dismantling the original suspension cables using temporary fixtures and installing new ones. The cable length adjustment is calculated based on the actual cable length after construction and the design length in the drawings. The total adjustment of the two bridge cable length adjustment devices equals the cable length adjustment.

[0044] The calculation method for the sling length adjustment is as follows:

[0045] (1);

[0046] in, This is the adjustment amount for the sling length. This refers to the actual length of the sling after initial installation. The design length of the slings in the drawing.

[0047] Step 3: Rotate the shape memory alloy sleeve to roughly adjust the cable length, obtaining the approximate adjustment amount. Use a wrench to rotate the sleeve to roughly adjust the cable length. After the approximate adjustment is completed, remove the temporary fixture, and the new cable will participate in the load-bearing of the bridge structure.

[0048] The calculation method for the rough adjustment amount of the sling is as follows:

[0049] (2);

[0050] in, For rough adjustment of the sling, The adjustment coefficient is a rough estimate, specifically the amount of cable length adjustment achieved per 1° rotation of the sleeve, determined through experimentation. The rotation angle of the sleeve.

[0051] Step 4: First calculate the adjustment amount of the sling length. Rough adjustment of the completed sling The difference is used to obtain the precise adjustment amount of the sling. Based on this precise adjustment, the heating current and heating time of the resistance wire are determined. An external power supply is then connected to activate the new sling and adjust its length. After activation, the external power supply is disconnected, and the activation interface is sealed. Once the shape memory alloy sleeve in the sling has naturally cooled to ambient temperature, the sling length adjustment is complete.

[0052] Sling length adjustment It consists of two parts: a coarse adjustment achieved by rotating the sleeve and a precise adjustment achieved by heating the sleeve. The precise adjustment of the sling is calculated as follows:

[0053] (3);

[0054] in, For precise adjustment of the slings.

[0055] Precise adjustment of slings Current intensity through external power supply and power-on time Control, its relation is:

[0056] (4);

[0057] in, This refers to the efficiency of heat transfer from the resistance wire to the sleeve. For the pre-tension strain of shape memory alloys, The resistance of the resistance wire. The length of the adjusting section in the shape memory alloy sleeve, For the quality of shape memory alloy sleeves, The specific heat capacity of shape memory alloys, The austenite initiation temperature. This is the austenite termination temperature.

[0058] Formula (4) is the core calculation formula of this invention, and its derivation process is as follows:

[0059] According to Joule's law, during the current-carrying time Heat generated by the internal resistance wire for:

[0060] (5)

[0061] Heat generated by the resistance wire Temperature rise of shape memory alloy bundles for:

[0062] (6)

[0063] The driving force behind the recovery deformation of shape memory alloys is the temperature-induced reverse martensitic transformation, i.e., the process of transforming from martensite to austenite. The driving temperature range is the austenite initiation temperature. austenite termination temperature When the temperature exceeds the austenite termination temperature Afterwards, the phase transition is complete. Assume the ambient temperature... Activation temperature of shape memory alloy sleeve All are within the austenite initiation temperature austenite termination temperature Between. After the sling is installed, its two ends are not fully constrained. To simplify the model, this invention introduces an approximate relationship to calculate the recovery strain of the shape memory alloy bundle. :

[0064] (7)

[0065] In the formula, The strain empirical coefficient represents the recoverable strain that can be produced for every degree Celsius increase in temperature. It is related to the maximum recoverable strain of the material. (Pre-tension strain of shape memory alloy wire) The relationship is related to ( ), and its formula is:

[0066] (8)

[0067] In this invention, the shape memory alloy sleeve primarily activates the adjusting section; the connecting section, constrained by the thread, cannot retract, and the sling length adjustment is limited. for:

[0068] (9)

[0069] In summary, substituting formulas (6), (7), and (8) into formula (9) yields the precise adjustment amount of the sling. Current intensity of external power supply Power-on time The relationship between them is expressed as formula (4).

[0070] In addition, during the service of the slings, if sling loss or excessive deformation of the main beam occurs, the automatic sling length adjustment device can be reactivated by powering on, thereby achieving rapid adjustment of sling force and main beam alignment, and achieving the effect of secondary activation to compensate for sling force.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A bridge suspension cable length adjustment device, characterized in that: The device includes a shape memory alloy sleeve (1), which includes an adjustment section (2) and connecting sections (3) respectively disposed at the upper and lower ends of the adjustment section (2). The connecting section (3) is provided with a threaded structure to realize the rotatable connection between the connecting section (3) and the fork lug plate and the anchor cup. The adjustment section (2) is provided with a resistance wire (4), and an insulating layer is provided between the resistance wire (4) and the inner wall of the adjustment section (2). The side of the adjustment section (2) is provided with an activation interface (6). The resistance wire (4) is connected to one end of an activation wire (5), and the other end of the activation wire (5) extends into the activation interface (6).

2. The bridge cable length adjustment device according to claim 1, characterized in that: The resistance wire (4) is made of nickel-chromium alloy.

3. The bridge cable length adjustment device according to claim 1, characterized in that: The bridge cable length adjustment device consists of two parts, which are divided into an upper cable length automatic adjustment device (7) and a lower cable length automatic adjustment device (8) according to their positions. The upper cable length automatic adjustment device (7) is connected to the upper fork lug plate (9) and the upper anchor cup (10) respectively, and the lower cable length automatic adjustment device (8) is connected to the lower fork lug plate (11) and the lower anchor cup (12) respectively.

4. The bridge cable length adjustment device according to claim 1, characterized in that: The shape memory alloy sleeve (1) is externally hexagonal.

5. A method for applying the bridge cable length adjustment device according to any one of claims 1 to 4, characterized in that: Includes the following steps: S1, Install a bridge sling length adjustment device on the new sling; S2, the original slings are removed using temporary tools and new slings are installed. The adjustment amount of the sling length is calculated based on the actual length of the sling after construction and the design length of the sling in the drawings. S3, rotate the shape memory alloy sleeve to roughly adjust the length of the sling, obtain the rough adjustment amount of the sling, and remove the temporary fixture after the rough adjustment is completed so that the new sling can participate in the stress of the bridge structure; S4. First, calculate the difference between the sling length adjustment amount and the coarse adjustment amount to obtain the sling precise adjustment amount. Then, determine the heating current and heating time of the resistance wire based on the sling precise adjustment amount to achieve precise adjustment of the sling length. Finally, wait for the shape memory alloy sleeve in the new sling to cool naturally to the ambient temperature.

6. The application method of the bridge cable length adjustment device according to claim 5, characterized in that: The calculation method for the sling length adjustment is as follows: （1）； in, This is the adjustment amount for the sling length. This refers to the actual length of the sling after initial installation. The design length of the slings in the drawing.

7. The application method of the bridge cable length adjustment device according to claim 5, characterized in that: The calculation method for the rough adjustment amount of the sling is as follows: （2）； in, For rough adjustment of the sling, The adjustment coefficient is a rough estimate, specifically the amount of cable length adjustment achieved per 1° rotation of the sleeve, determined through experimentation. The rotation angle of the sleeve.

8. The application method of the bridge cable length adjustment device according to claim 7, characterized in that: The calculation method for the precise adjustment amount of the sling is as follows: （3）； in, For precise adjustment of the slings.

9. The application method of the bridge cable length adjustment device according to claim 8, characterized in that: Precise adjustment of slings Current intensity through external power supply and power-on time Control, its relation is: （4）； in, This refers to the efficiency of heat transfer from the resistance wire to the sleeve. For the pre-tension strain of shape memory alloys, The resistance of the resistance wire. The length of the adjusting section in the shape memory alloy sleeve, For the quality of shape memory alloy sleeves, The specific heat capacity of shape memory alloys, The austenite initiation temperature. This is the austenite termination temperature.

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