Self-adaptive self-anchored suspension bridge cable strand rapid adjusting method

Abstract

The invention provides a self-adaptive self-anchored suspension bridge cable strand rapid adjustment method, which comprises the following steps of calibrating a cable strand linear expansion coefficient alpha, establishing a function relationship between temperature change and reference strand sag and cable strand tension change, measuring a mean value of temperature fields of a reference strand and a general cable strand along a longitudinal bridge direction, and calculating a cable strand tension coefficient alpha; the theoretical sag of the designed line shape of the reference strand and the theoretical sag of the designed line shape of the general cable strand are obtained according to the relation between the length of the cable strand and the sag of the cable strand, the actual line shape is measured through a total station and compared with the theoretical line shape in S2, and the reference strand is adjusted; and the difference value between the adjusted sag of the reference strand and the adjusted sag of the general cable strand is used as a control parameter, and the general cable strand is adjusted. The method has the beneficial effects that based on detailed field actual measurement data, the temperature limitation of cable strand adjustment is broken through, even under the condition that the temperature difference change is large, linear adjustment of the cable strand can be conducted, and the strict requirement for temperature stability is lowered.

Description

Technical Field

[0001] The invention relates to the technical field of suspension bridges, and in particular to a method for quickly adjusting cables of an adaptive self-anchored suspension bridge. Background Art

[0002] A suspension bridge is a bridge with cables as the main load-bearing components. There are various types of suspension bridges. According to the main cable anchoring method, it can be divided into ground-anchored suspension bridges and self-anchored suspension bridges. Ground-anchored suspension bridges transmit the tension of the main cable to the foundation through anchors, which is suitable for large-span bridges, while self-anchored suspension bridges directly anchor the main cable to the main beam, which is suitable for areas with poor geological conditions, but the span is usually not too large. Self-anchored suspension bridges are generally built in the "beam first, cable later" manner, and their base strands directly affect the line shape of the main cable and the stress of the bridge structure.

[0003] The cable strands of a suspension bridge are composed of reference strands and general strands. The reference strands are positioned by absolute elevation, while the general strands are determined by their relative position to the reference strands. Due to the effect of heat conduction, the temperature field of the main cable changes unevenly, affecting the linear shape and internal force of the strands. When the reference strands and the general strands are in different temperature fields, the reference strands will not be able to provide positioning, which will seriously affect the installation accuracy of the general strands. Therefore, in order to reduce the influence of the temperature field, the current linear shape adjustment of the strands is generally carried out at night when the temperature is stable. However, there are still the following problems: under the action of solar radiation during the day, the temperature of the general strands above is higher than that of the strands below; at night, as the atmospheric temperature decreases, due to the insulation effect of the outer strands, the temperature of the inner strands is higher than that of the outer strands. Therefore, under the action of atmospheric temperature, the temperature field of the cross section of the main cable changes greatly, resulting in a significant change in the linear shape and internal force of the strands, and it is impossible to determine whether the strands are adjusted in place. At the same time, the conditions for cable strand adjustment temperature stability are generally that the temperature difference of the cable strand cross section is less than 1°C, and the temperature difference of the cable strand in the longitudinal direction of the bridge is less than 2°C. With the construction of more and more long-span suspension bridges, the temperature difference of the cable strand in the longitudinal direction of the bridge may be greater than 2°C, so it is necessary to make adjustments when the temperature field stability condition is not met. From the above analysis, it can be seen that the reason why the temperature field effect causes the cable strand adjustment error is that the cable strand design line shape is based on the reference temperature. In the actual environment, the uneven temperature field of the cable strand causes the difference in the installation temperature of the reference strand and the general cable strand, and the greater the difference, the greater the deviation of the cable strand line shape. Therefore, the influence of the temperature field must be considered when adjusting the cable strand line shape in practice. Summary of the invention

[0004] In order to solve the problem that the uneven temperature field of the cable strands causes the difference in the temperature of the reference strands and the general cable strands, which makes it impossible to determine whether the cable strands are adjusted in place; the purpose of the present invention is to provide a method for quickly adjusting the cable strands of an adaptive self-anchored suspension bridge, comprising the following steps: S1: Calibrate the cable linear expansion coefficient α, establish the functional relationship between temperature change and reference cable sag and cable tension change. The cable sag change or cable tension change caused by temperature change can be calculated by the following formula: , .

[0005] in are the sag, horizontal projection length and curve length of the cable strand respectively; is the height difference between the two sections of the cable; are the elastic model and cross section of the cable, respectively.

[0006] S2: Determine the mean value of the temperature field of the reference strand and the general strand along the longitudinal bridge direction. The theoretical sag of the design line shape of the reference strand and the theoretical sag of the design line shape of the general strand are obtained based on the relationship between the strand length and the strand sag, as follows: The strand length expression is The cable strand sag expression is: .

[0007] in, ; are the starting points of the stock respectively; S3: Use a total station to measure the actual line type, compare it with the theoretical line type of S2, check the relative verticality of the control section of the benchmark strand and the general cable strand, convert the verticality into an absolute elevation control parameter, and adjust the benchmark strand; use the difference between the adjusted verticality of the benchmark strand and the adjusted verticality of the general cable strand as the control parameter to adjust the general cable strand.

[0008] Furthermore, the cable strand linear expression is: .

[0009] As a preferred solution, the method of calibrating the linear expansion coefficient of the cable strand in step S1 is to obtain the linear expansion coefficient of the cable strands of the same batch by field testing. The linear expansion coefficient is calculated as follows: are the elongation of the cable strand caused by temperature change and the length of the cable strand at the reference temperature, respectively.

[0010] As a preferred solution, the average value of the temperature field of the reference strand and the general cable strand along the longitudinal bridge direction in step S2 can be determined by disposing temperature sensors on the surfaces of the reference strand and the general cable strand; the sensors are disposed along the longitudinal bridge direction of the reference strand and the general cable strand, and are appropriately adjusted according to the geographical environment of the bridge site; and the average temperature of the reference strand and the general cable strand is obtained based on the temperature measured by the temperature sensors.

[0011] As a preferred solution, the cable strands are adjusted by jack traction, the cable strands are connected to temporary cable clamps, the temporary cable clamps are connected to steel strands and anchors, and the other end of the steel strands is connected to a jack on the bridge deck to achieve traction.

[0012] The beneficial effects of the present invention are: (1) Based on detailed field measurement data, the temperature linear expansion coefficient of the cable strands was calibrated. The accurate determination of this coefficient is crucial to understanding the behavior of the cable strands under different temperature conditions. On this basis, a set of programs specifically used to calculate the sag or tension changes of the cable strands caused by temperature changes can be further compiled, providing a powerful technical means and theoretical support for achieving fast and accurate cable strand adjustment.

[0013] (2) By deploying temperature monitoring points and collecting real-time data from these monitoring points, a temperature field model of the cable strands is constructed. This allows more subtle temperature differences and changes to be taken into account when adjusting the cable strands, thereby achieving more refined adjustments to the cable strands.

[0014] (3) Traditional cable shape adjustment methods often need to be performed when the temperature is relatively stable at night, which undoubtedly limits the flexibility and efficiency of the adjustment work. This application breaks through this limitation and can adjust the cable shape even when the temperature difference changes greatly, reducing the strict requirements for temperature stability. DETAILED DESCRIPTION

[0015] To illustrate the features of the present invention, the present invention will be further described below in conjunction with embodiments.

[0016] Example: This embodiment provides a method for quickly adjusting cables of an adaptive self-anchored suspension bridge, including the following steps: S1: Calibrate the cable linear expansion coefficient α, establish the functional relationship between temperature change and reference cable sag and cable tension change. The cable sag change or cable tension change caused by temperature change can be calculated by the following formula: , The cable strand linear expression is: .

[0017] in are the sag, horizontal projection length and curve length of the cable strand respectively; is the height difference between the two sections of the cable; are the elastic model and cross section of the cable, respectively.

[0018] S2: Determine the mean value of the temperature field of the reference strand and the general strand along the longitudinal bridge direction. The theoretical sag of the design line shape of the reference strand and the theoretical sag of the design line shape of the general strand are obtained based on the relationship between the strand length and the strand sag, as follows: The strand length expression is The cable strand sag expression is: .

[0019] in, ; are the starting points of the stock respectively; S3: Use a total station to measure the actual line type, compare it with the theoretical line type of S2, check the relative verticality of the control section of the benchmark strand and the general cable strand, convert the verticality into an absolute elevation control parameter, and adjust the benchmark strand; use the difference between the adjusted verticality of the benchmark strand and the adjusted verticality of the general cable strand as the control parameter to adjust the general cable strand.

[0020] Preferably, the method of calibrating the linear expansion coefficient of the cable strand in step S1 of this embodiment is to obtain the linear expansion coefficient of the cable strands of the same batch by field testing. The linear expansion coefficient is calculated as follows: are the elongation of the cable strand caused by temperature change and the length of the cable strand at the reference temperature, respectively.

[0021] Preferably, in step S2 of this embodiment, the average value of the temperature field of the reference strand and the general cable strand along the longitudinal bridge direction can be determined by disposing temperature sensors on the surfaces of the reference strand and the general cable strand; the sensors are disposed along the longitudinal bridge direction of the reference strand and the general cable strand, and are appropriately adjusted according to the geographical environment of the bridge site; and the average temperature of the reference strand and the general cable strand is obtained based on the temperature measured by the temperature sensors.

[0022] Preferably, the cable strands of this embodiment are adjusted by jack traction, the cable strands are connected to temporary cable clamps, the temporary cable clamps are connected to steel strands and anchors, and the other end of the steel strands is connected to a jack on the bridge deck to achieve traction.

[0023] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit the present invention. The present invention is described in detail with reference to the preferred embodiments. It should be understood by those skilled in the art that any changes, modifications, additions or substitutions made by those skilled in the art within the essential scope of the present invention do not deviate from the purpose of the present invention and should also fall within the scope of the claims of the present invention. Other related technical structures not fully disclosed in the present invention are prior art in the art.

Claims

1. A method for rapid adjustment of cables of an adaptive self-anchored suspension bridge, characterized in that: The following steps are involved: S1: Calibrate the cable linear expansion coefficient α, establish the functional relationship between temperature change and reference cable sag and cable tension change. The cable sag change or cable tension change caused by temperature change can be calculated by the following formula: , ; in are the sag, horizontal projection length and curve length of the cable strand respectively; is the height difference between the two sections of the cable; are the elastic model and cross section of the cable, respectively; S2: Determine the mean value of the temperature field of the reference strand and the general strand along the longitudinal bridge direction. The theoretical sag of the design line shape of the reference strand and the theoretical sag of the design line shape of the general strand are obtained based on the relationship between the strand length and the strand sag, as follows: The strand length expression is ; The expression of cable sag is: ; in, ; are the starting points of the stock respectively; S3: Use a total station to measure the actual line type, compare it with the theoretical line type of S2, check the relative verticality of the control section of the benchmark strand and the general cable strand, convert the verticality into an absolute elevation control parameter, and adjust the benchmark strand; use the difference between the adjusted verticality of the benchmark strand and the adjusted verticality of the general cable strand as the control parameter to adjust the general cable strand.

2. The method for rapid adjustment of cable strands of an adaptive self-anchored suspension bridge according to claim 1, characterized in that: The cable strand shape expression is: 。 3. The method for rapid adjustment of cable strands of an adaptive self-anchored suspension bridge according to claim 1, characterized in that: The method of calibrating the linear expansion coefficient of the cable strand in step S1 is to obtain the linear expansion coefficient of the cable strands of the same batch by field testing. The linear expansion coefficient is calculated as follows: are the elongation of the cable strand caused by temperature change and the length of the cable strand at the reference temperature, respectively.

4. The method for rapid adjustment of cable strands of an adaptive self-anchored suspension bridge according to claim 1, characterized in that: In step S2, the average value of the temperature field of the reference strand and the general cable strand along the longitudinal bridge direction can be determined by arranging temperature sensors on the surfaces of the reference strand and the general cable strand; the sensors are arranged along the longitudinal bridge direction of the reference strand and the general cable strand, and are appropriately adjusted according to the geographical environment of the bridge site; The average temperature of the reference strand and the general strand is obtained according to the temperature measured by the temperature sensor.

5. The method for rapid adjustment of cable strands of an adaptive self-anchored suspension bridge according to claim 1, characterized in that: The cable strands are adjusted by jack traction, the cable strands are connected to temporary cable clamps, the temporary cable clamps are connected to steel strands and anchors, and the other end of the steel strands is connected to a jack on the bridge deck to achieve traction.

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