Parallel steel strand stay cable multi-stage equivalent tension cable force control method

Abstract

The invention discloses a parallel steel strand stay cable multistage equivalent tension cable force control method which comprises the following steps: S1, acquiring temperature data of a whole cable-stayed bridge through a temperature acquisition system; s2, collecting elevation data of the cable-stayed bridge through an elevation automatic measurement system; s3, a temperature acquisition system and an automatic elevation measurement system are used for conducting 24-hour measurement once, an elevation and temperature change relation curve is obtained and serves as a correction data reference, and then the stay cable is tensioned for the first time; s4, after the stay cable is tensioned for the first time, the bridge deck crane looses a hook and moves forwards in place, measurement is conducted again through the temperature collecting system and the automatic elevation measuring system, and correction data needed by the beam section temperature and the tension force loss after the crane moves forwards are obtained; and S5, taking the temperature of the beam section after the crane moves forwards and correction data required by the loss of one cable tension force as references, and then carrying out secondary tensioning on the stay cable. According to the invention, the influence of temperature on the tensioning of the cable-stayed bridge is solved.

Description

Technical Field

[0001] The invention relates to the technical field of equal-value tensioning construction of a cable-stayed cable, and in particular to a multi-stage equal-value tensioning cable force control method for parallel steel stranded cable-stayed cables. Background Art

[0002] As a type of bridge with a large span, the cable-stayed bridge can reduce the use of piers. Compared with traditional bridges, it has more economic advantages in crossing wide waters. The larger span can make the appearance of the cable-stayed bridge have more unique designs. Many cable-stayed bridges are also widely sought after in bridge selection for their unique image. However, the construction of large-span cable-stayed bridges also brings more construction challenges. Among them, the linear control problem of large-span cable-stayed bridges under the influence of temperature is particularly prominent. Whether it is the temperature difference between day and night or the temperature difference under sunlight, the influence on the tension value of the cable is more significant. Based on this, the present invention proposes a multi-stage equivalent tensioning cable force control method for parallel steel strand cable-stayed cables based on the equivalent tensioning method. Summary of the invention

[0003] The purpose of the present invention is to overcome the existing defects and provide a parallel steel strand cable multi-level equivalent tensioning cable force control method to solve the influence of temperature on the tensioning of cable-stayed bridges.

[0004] The technical solution to achieve the above purpose is:

[0005] A method for controlling multi-level equal-value tensioning cable forces of parallel steel stranded cable stays, comprising:

[0006] Step S1, collecting temperature data of the entire cable-stayed bridge through a temperature collection system;

[0007] Step S2, collecting elevation data of the cable-stayed bridge through an elevation automation measurement system;

[0008] Step S3, before the first tensioning of the cable, a 24-hour measurement is performed using the temperature acquisition system and the elevation automatic measurement system to obtain a curve of elevation and temperature change as a reference for correction data, and then the first tensioning of the cable is performed;

[0009] Step S4, after the first tensioning of the cable, the bridge crane is unhooked and moved forward to its position, and the temperature acquisition system and the height automatic measurement system are used to perform another measurement to obtain the beam section temperature after the crane moves forward and the correction data required for the loss of cable force;

[0010] Step S5, the beam section temperature after the crane moves forward and the correction data required for the loss of a cable force are used as a reference, and then the second tensioning of the cable is performed;

[0011] Step S6, after the tensioning is completed, the elevation change of the current beam section after the tensioning is completed is obtained, and then the tensioning of the cable-stayed bridge is corrected accordingly.

[0012] Preferably, in step S1, the temperature acquisition system includes temperature sensors arranged at the tower, beams and cables, wherein the tower is arranged around the tower wall, the beam ends are arranged on the surface and bottom of the beam body, and the temperature sensor at the cable is fixedly arranged inside the PE sleeve because the cable is protected by a PE sleeve.

[0013] Preferably, in step S2, the automated elevation measurement system is mainly composed of an automated measurement robot, a total station intelligent monitoring unit, and an automated monitoring platform. The total station intelligent monitoring unit controls the measurement robot to automatically complete periodic deformation monitoring, and uploads data to the automated monitoring platform through the 4G network. The platform calculates deformation monitoring results and displays deformation trends in real time.

[0014] Preferably, in step S3, the calculation formula for the tensioning force value T1 of the first steel strand tensioned for the first time is as follows:

[0015]

[0016] In the formula, E c is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, δ1 is the displacement of the beam end after the tensioning of this stage is completed, δ2 is the displacement of the tower end after the tensioning of this stage is completed, α is the elevation angle of the inclined cable, ε is the retraction of the clip after the tensioning of this stage is completed, N is the force of the entire cable after the tensioning of this stage is completed, n is the number of steel strands in the cable, and l is the length of the inclined cable.

[0017] Preferably, in step S5, the cable length, elongation and stress-free length considering the sag effect are respectively:

[0018]

[0019] S0 = S - ΔS;

[0020] In the formula, the coordinates of the anchor point at the beam end are (x, h), q is the linear density of the cable guide, and the intermediate calculation parameters are H is the horizontal component of the cable;

[0021] The number of strands in the cable is n. When the cable is tensioned twice, the length of the cable changed by the tensioning of the first strand is

[0022] The pull-out amount of the first cable is:

[0023]

[0024] Then the tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is as follows:

[0025]

[0026] Where, E is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, S 01 is the stress-free length of the cable after the first tensioning, S 02 is the stress-free length of the cable after the second tensioning, S1 is the cable length after the first tensioning, and S2 is the cable length after the second tensioning;

[0027] In order to avoid the impact of temperature and the loss of cable force during the first tensioning, the second cable tensioning should be carried out during the night when the temperature is stable.

[0028] And T is calculated by the following formula 21 To make corrections:

[0029]

[0030] In the formula, ΔT t is the temperature correction value, ΔT1 is the correction for the first tensioning error, N ls is the actual cable force, N lL is the theoretical cable force value;

[0031] Finally, the corrected tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is:

[0032]

[0033] The beneficial effects of the present invention are as follows: the present invention is based on the basic equivalent tensioning method, and on this basis utilizes a temperature monitoring system and an elevation automation measurement system to obtain necessary measured data, and corrects the calculation formula of the equivalent tensioning method according to the measured data, and uses the corrected formula to calculate the tensioning force value, so that the beam body can be lifted to a specified elevation, thereby solving the influence of temperature on the tensioning of a cable-stayed bridge. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a flow chart of a method for controlling multi-level equal-value tensioning cable forces of parallel steel stranded cable stays of the present invention;

[0035] Figure 2 It is a schematic diagram of the medium value tensioning in the present invention;

[0036] Figure 3 It is the 24h elevation and temperature relationship diagram of the 3# beam section in the present invention;

[0037] Figure 4 It is the 24h elevation and temperature relationship diagram of the 4# beam section in the present invention;

[0038] Figure 5 It is the 24h elevation and temperature relationship diagram of the 5# beam section in the present invention;

[0039] Figure 6 It is a 24h elevation and temperature relationship diagram of the 6# beam section in the present invention. DETAILED DESCRIPTION

[0040] The technical solution of the present invention will be described clearly and completely below in conjunction with the accompanying drawings. In the description of the present invention, it should be noted that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside" and the like indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, which are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", and "third" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0041] The present invention will be further described below in conjunction with the accompanying drawings.

[0042] First, the beam section is cantilevered and assembled. The beam section is slowly lifted by the bridge crane. When the beam section is hoisted near the bridge deck, the horizontal jack on the hoist is used to adjust the longitudinal slope of the hoisted steel box beam to be consistent with the longitudinal slope of the installed beam section, so that the gap width of the upper and lower interfaces at the corresponding position of the installed beam section is roughly equal. Continue to lift the beam section and adjust the elevation to make it roughly flush with the surface of the installed beam section. Then use the longitudinal adjustment jack at the front end of the bridge crane to drive the steel box beam to move longitudinally, so that the beam section slowly moves closer to the installed beam section. Repeated fine-tuning is performed to align the top stop plate at the longitudinal partition of the hoisted beam section with the installed beam section. Weld the code plate, and then weld the web plate and the upper and lower bottom plate annular seams.

[0043] After the cantilever assembly of the beam section is completed, proceed to the following steps.

[0044] like Figure 1 As shown, a method for controlling multi-level equal-value tensioning cable forces of parallel steel stranded cable stays comprises:

[0045] Step S1, collecting temperature data of the entire cable-stayed bridge through a temperature collection system.

[0046] In the embodiment, the temperature acquisition system includes temperature sensors arranged at the tower, beams and cables, wherein the tower is arranged around the tower wall, the beam ends are arranged on the surface and bottom of the beam body, and the temperature sensor at the inclined cable is fixed inside the PE sleeve because the inclined cable is protected by a PE sleeve.

[0047] Step S2, collecting elevation data of the cable-stayed bridge through an automated elevation measurement system.

[0048] In the embodiment, the automated elevation measurement system is mainly composed of an automated measurement robot, a total station intelligent monitoring unit, and an automated monitoring platform. The total station intelligent monitoring unit controls the measurement robot to automatically complete periodic deformation monitoring, and uploads data to the automated monitoring platform through the 4G network. The platform calculates the deformation monitoring results and displays the deformation trend in real time.

[0049] Step S3, before the first tensioning of the inclined cable, a 24-hour measurement is performed using the temperature acquisition system and the elevation automation measurement system to obtain a curve of the relationship between elevation and temperature change as a reference for correction data, and then the first tensioning of the inclined cable is performed.

[0050] In the embodiment, the cable tensioning is equal value tensioning, and the tension value of a single steel strand varies as follows: Figure 2 As shown in the figure, the influence of the elevation change of the main beam on the cable force reduction during the tensioning of the inclined cable is considered. At the same time, the influence of the tower deviation of the main tower on the cable force reduction is very obvious. If the influence of the tower deviation is not considered, it will cause a large error. Through analysis, the calculation formula of the tension value T1 of the first steel strand tensioned for the first time is as follows:

[0051]

[0052] In the formula, E c is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, δ1 is the displacement of the beam end after the tensioning of this stage is completed, δ2 is the displacement of the tower end after the tensioning of this stage is completed, α is the elevation angle of the inclined cable, ε is the retraction of the clip after the tensioning of this stage is completed, N is the force of the entire cable after the tensioning of this stage is completed, n is the number of steel strands in the cable, and l is the length of the inclined cable.

[0053] Step S4, after the first tensioning of the cable, the bridge crane is unhooked and moved forward to its position, and another measurement is performed through the temperature acquisition system and the elevation automation measurement system to obtain the beam section temperature after the crane moves forward and the correction data required for the loss of cable force.

[0054] Step S5, the temperature of the beam section after the crane moves forward and the correction data required for the loss of a cable force are used as a reference, and then the second tensioning of the inclined cable is performed.

[0055] In the embodiment, affected by its own weight, the cable presents a certain sag; after the first and second inclined cables are completed, their states are determined, and the stress-free length is also determined. By calculating the difference in the stress-free lengths under the two states, the pull-out amount of the anchor head of each cable when the cable is in the second state can be calculated, and the pull-out amount is a constant value; the force required for the elongation value of the pull-out of the first cable of the second cable is the tensioning force of the first cable of the second cable. The cable length, elongation, and stress-free length considering the sag effect are:

[0056]

[0057] S0 = S - ΔS;

[0058] Where, the coordinates of the anchor point at the beam end are (x, h), which can be calculated based on the finite element model, q is the linear density of the cable guide, and the intermediate calculation parameters are H is the horizontal component of the cable;

[0059] The number of strands in the cable is n. When the cable is tensioned twice, the length of the cable changed by the tensioning of the first strand is

[0060] The pull-out amount of the first cable is:

[0061]

[0062] Then the tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is as follows:

[0063]

[0064] Where, E is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, S 01 S is the stress-free cable length after the first cable tensioning. 02 is the stress-free cable length after the second tensioning of the inclined cable, S1 is the cable length after the first tensioning, and S2 is the cable length after the second tensioning;

[0065] In order to avoid the impact of temperature and the loss of cable force during the first tensioning, the second cable tensioning should be carried out during the night when the temperature is stable.

[0066] And T is calculated by the following formula 21 To make corrections:

[0067] like Figure 3-6 The figure shows the monitoring results of different beam segments after assembling for 24 hours. The dashed line segment in the figure shows the temperature change within 24 hours. It can be seen that the higher the temperature, the greater the change of the beam segment. As the length of the beam segment assembly increases, the temperature has a greater impact on the beam segment. The temperature is highest in the afternoon, and the beam segment elevation decreases the most.

[0068] According to the process arrangement, the second cable tensioning usually starts after 7 pm, when the structural temperature is still unstable and the main beam elevation is still changing; therefore, the second cable tensioning should also consider the impact of structural temperature changes;

[0069] The temperature correction method is:

[0070] When the height difference between the cantilever end elevation measured at the tensioning moment and the beam section elevation at the same working condition when the temperature is stable is ΔH, the temperature correction is:

[0071]

[0072] The first tensioning construction involves hanging cable operations, and the cable tensioning cycle is relatively long, generally 2 days. Since it involves high-altitude operations, it can only be carried out during the day. During the day, affected by the external construction environment, a cable force often has a large deviation. Therefore, the first tensioning correction amount is:

[0073]

[0074] In the formula, ΔT t is the temperature correction value, ΔT1 is the correction for the first tensioning error, N ls is the actual cable force, N lL is the theoretical cable force value;

[0075] Among them, the first tensioning construction involves cable hanging operations, and the cable tensioning period is relatively long, generally 2 days. Since it involves high-altitude operations, it can only be carried out during the day. During the day, affected by the external construction environment, the cable tension often has a large deviation.

[0076] Finally, the corrected tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is:

[0077]

[0078] Step S6, after the tensioning is completed, the elevation change of the current beam section after the tensioning is completed is obtained, and then the tensioning of the cable-stayed bridge is corrected accordingly.

[0079] As shown in Table 1, the measured elevation after correction is basically close to the theoretical elevation.

[0080]

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that the technical solutions described in the above embodiments may still be modified, or some or all of the technical features may be replaced by equivalents. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling the multi-level equal-value tensioning cable force of parallel steel stranded cable stays, characterized in that: include: Step S1, collecting temperature data of the entire cable-stayed bridge through a temperature collection system; Step S2, collecting elevation data of the cable-stayed bridge through an elevation automation measurement system; Step S3, before the first tensioning of the cable, a 24-hour measurement is performed using the temperature acquisition system and the elevation automation measurement system to obtain a curve of elevation and temperature change as a reference for correction data, and then the first tensioning of the cable is performed; Step S4, after the first tensioning of the cable, the bridge crane is unhooked and moved forward to its position, and the temperature acquisition system and the height automatic measurement system are used to perform another measurement to obtain the beam section temperature after the crane moves forward and the correction data required for the loss of cable force; Step S5, the beam section temperature after the crane moves forward and the correction data required for the loss of a cable force are used as a reference, and then the second tensioning of the cable is performed; Step S6, after the tensioning is completed, the elevation change of the current beam section after the tensioning is completed is obtained, and then the tensioning of the cable-stayed bridge is corrected accordingly.

2. A method for controlling the multi-level equal-value tensioning cable force of parallel steel stranded cables according to claim 1, characterized in that: In step S1, the temperature acquisition system includes temperature sensors arranged at the tower, beams and cables, wherein the tower is arranged around the tower wall, the beam ends are arranged on the surface and bottom of the beam body, and the temperature sensor at the inclined cable is fixed inside the PE sleeve because the inclined cable is protected by a PE sleeve.

3. The method for controlling the multi-level equal-value tensioning cable force of parallel steel stranded cable according to claim 1 is characterized in that: In step S2, the elevation automated measurement system is mainly composed of an automated measurement robot, a total station intelligent monitoring unit, and an automated monitoring platform. The total station intelligent monitoring unit controls the measurement robot to automatically complete periodic deformation monitoring, and uploads data to the automated monitoring platform through the 4G network. The platform calculates deformation monitoring results and displays deformation trends in real time.

4. The method for controlling the multi-level equal-value tensioning cable force of parallel steel stranded cable according to claim 1 is characterized in that: In step S3, the calculation formula of the tensioning force value T1 of the first steel strand tensioned for the first time is as follows: In the formula, E c is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, δ1 is the displacement of the beam end after the tensioning of this stage is completed, δ2 is the displacement of the tower end after the tensioning of this stage is completed, α is the elevation angle of the inclined cable, ε is the retraction of the clip after the tensioning of this stage is completed, N is the force of the entire cable after the tensioning of this stage is completed, n is the number of steel strands in the cable, and l is the length of the inclined cable.

5. The method for controlling the multi-level equal-value tensioning cable force of parallel steel stranded cable according to claim 1, characterized in that: In step S5, the cable length, elongation and stress-free length considering the sag effect are: S0 = S - ΔS; In the formula, the coordinates of the anchor point at the beam end are (x, h), q is the linear density of the cable guide, and the intermediate calculation parameters are H is the horizontal component of the cable; The number of strands in the cable is n. When the cable is tensioned twice, the length of the cable changed by the tensioning of the first strand is The pull-out amount of the first cable is: Then the tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is as follows: Where, E is the elastic modulus of the steel strand, A is the cross-sectional area of ​​the steel strand, S 01 is the stress-free length of the cable after the first tensioning, S 02 is the stress-free length of the cable after the second tensioning, S1 is the length of the cable after the first tensioning, and S2 is the length of the cable after the second tensioning; In order to avoid the impact of temperature and the loss of cable force during the first tensioning, the second cable tensioning should be carried out during the night when the temperature is stable. And T is calculated by the following formula 21 To make corrections: In the formula, ΔT t is the temperature correction value, ΔT1 is the correction for the first tensioning error, N ls is the actual cable force, N lL is the theoretical cable force value; Finally, the corrected tension value T of the second tensioned steel strand is obtained. 21 The calculation formula is:

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