Deflection early warning control and deviation correction method for large-span continuous beam hanging basket cast-in-cantilever bridge

Abstract

The invention relates to the technical field of bridge deflection early warning, in particular to a large-span continuous beam hanging basket cantilever pouring bridge deflection early warning control and deviation correction method which comprises the steps that a hanging basket is hung to a bridge cantilever through a hanging belt and assembled and fixed, and beam section formwork installation, steel bar binding, prestressed pipeline installation and concrete pouring are conducted in sequence. Installing a deflection sensor and giving an alarm when the deflection exceeds a set threshold value; the control stability of bridge deflection early warning is determined on the basis of the sling elongation difference quantity during concrete pouring and during concrete non-pouring; if the control stability does not meet the requirement, the pouring speed of the concrete is adjusted; after pouring is completed, concrete is cured, a prestress anchoring bundle penetrates into the concrete, prestress bundle tensioning and pipeline grouting operation are conducted in sequence, and the hanging basket is dismantled after bridge cantilevers at the two ends are subjected to closure construction; and the tensioning duration of the prestress is adjusted based on the grouting plumpness in the pipeline. According to the invention, the control stability of bridge deflection early warning is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge deflection early warning, and in particular to a deflection early warning control and deviation correction method for a cantilever-cast bridge with a hanging basket for a large-span continuous beam. Background Art

[0002] In existing technologies, the stress state of bridge structures during cantilever casting using a hanging basket is complex and constantly changing. From the installation of the hanging basket and the gradual casting of beam segments to the application of prestress and the closure of the bridge cantilever, each step has a crucial impact on the final quality and performance of the bridge. As a key indicator of the structural stress and deformation state, precise control and early warning of bridge deflection are of great significance for ensuring bridge construction safety and the quality of the completed bridge.

[0003] In recent years, rapid advances in sensor technology, computer technology, and structural analysis theory have provided more advanced means for early warning, control, and correction of deflection in cantilever-cast bridges with large-span continuous beams. By installing various sensors, such as deflection and strain sensors, at key locations on the bridge structure, real-time data on bridge deformation and stress can be acquired. Using this data, advanced data analysis methods and structural mechanics models enable accurate prediction and early warning of bridge deflection, enabling timely and effective corrective measures. However, despite these advances, these technologies still face numerous challenges in actual construction.

[0004] Chinese patent application publication number: CN111521356A discloses a bridge deflection warning method and system, the method includes the following steps: obtaining deflection monitoring data, environmental temperature monitoring data, and vehicle crossing time information of a target bridge, wherein the vehicle crossing time information includes a vehicle crossing period and / or a non-vehicle crossing period; dividing the deflection monitoring data into non-vehicle passing deflection data in a non-vehicle passing period and vehicle passing deflection data in a vehicle passing period based on the vehicle crossing time information, calculating the mean of the non-vehicle passing deflection data and the corresponding environmental temperature monitoring data in a preset period and the maximum value of the vehicle passing deflection change amplitude in the vehicle passing period, wherein the preset period is not less than 10 minutes and not more than 1 hour; performing correlation analysis on the mean of the non-vehicle passing deflection data and the mean of the corresponding environmental temperature monitoring data in a preset period; generating a real-time deflection warning threshold value of the target bridge based on the correlation analysis results and the maximum value of the vehicle passing deflection change amplitude. It can be seen from this that the problem exists that the slings are installed too tightly when assembling the hanging basket, causing the bottom formwork frame to be in a tension state when not bearing load. When pouring concrete, the deformation of the slings affects the deformation control of the hanging basket, thereby causing the control stability of the bridge deflection warning to decrease. Summary of the Invention

[0005] To this end, the present invention provides a deflection warning control and correction method for a cantilevered bridge cast by a hanging basket of a large-span continuous beam, so as to overcome the problem in the prior art that, due to the excessive tight installation of the slings during the assembly of the hanging basket, the bottom formwork is in a tension state when not bearing load. When pouring concrete, the deformation of the slings affects the deformation control of the hanging basket, thereby causing a decrease in the control stability of the bridge deflection warning.

[0006] To achieve the above objectives, the present invention provides a method for early warning, control, and correction of deflection of a long-span continuous beam cantilever-casting bridge using a hanging basket, comprising: using a sling to hoist the hanging basket to the bridge cantilever and assemble and secure it, sequentially performing beam section formwork installation, steel bar binding, prestressed pipe installation, and concrete pouring, installing a deflection sensor and issuing an alarm when the deflection exceeds a set threshold; obtaining the sling elongation when concrete pouring is completed and before pouring; determining the control stability of the bridge deflection early warning based on the difference in sling elongation when concrete pouring is completed and before pouring; if the control stability does not meet the requirements, adjusting the concrete pouring speed, or determining the reliability of the cantilever construction based on the relative displacement of the beams at both ends of the bridge cantilever; if the reliability of the cantilever construction does not meet the requirements, adjusting the vertical height of the hanging basket; after pouring is completed, curing the concrete and inserting the prestressed anchor bundle, sequentially performing prestressed bundle tensioning and pipe grouting operations, and removing the hanging basket after the bridge cantilever at both ends is connected; and adjusting the prestressing tensioning duration based on the grouting fullness in the pipe.

[0007] Furthermore, determining the control stability of the bridge deflection early warning includes: Comparing the difference in sling elongation between when concrete is poured and when concrete is not poured with a preset first difference; If the difference in the sling elongation between when the concrete is poured and when the concrete is not poured is greater than the preset first difference, it is determined that the control stability of the bridge deflection warning does not meet the requirements.

[0008] Furthermore, determining the reliability of the cantilever construction includes: Comparing the difference in the sling elongation between when the concrete is poured and when the concrete is not poured with the preset first difference and the preset second difference respectively; If the difference in the elongation of the sling during concrete pouring and before concrete pouring is greater than the preset first difference and less than or equal to the preset second difference, it is preliminarily determined that the reliability of the cantilever construction does not meet the requirements, and whether the reliability of the cantilever construction meets the requirements is determined based on the relative displacement of the beams at both ends of the bridge cantilever.

[0009] Furthermore, the pouring speed of the concrete is adjusted, including: Comparing the difference in sling elongation between when the concrete is poured and when the concrete is not poured with the preset second difference; If the difference in the length of the sling between when the concrete is poured and when the concrete is not poured is greater than the preset second difference, the pouring speed of the concrete is reduced.

[0010] Furthermore, the reduction range of the concrete pouring speed is determined by the difference between the sling elongation difference when the concrete is poured and when the concrete is not poured and the preset second difference.

[0011] Furthermore, the vertical height of the hanging basket is adjusted, including: Comparing the relative displacement of the beams at both ends of the bridge cantilever with the preset first displacement and the preset second displacement respectively; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement, it is determined that the reliability of the cantilever construction does not meet the requirements, wherein, If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement and less than or equal to the preset second displacement, increasing the vertical height of the hanging basket; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset second displacement, it is preliminarily determined that the accuracy of the prestressed construction does not meet the requirements, and whether the accuracy of the prestressed construction meets the requirements is determined based on the fullness of the grouting in the pipeline.

[0012] Furthermore, the increase in the vertical height of the hanging basket is determined by the difference between the relative displacement of the beams at both ends of the bridge cantilever and a preset first displacement.

[0013] Furthermore, the tensioning time of the prestress is adjusted, including: Compare the grouting fullness in the pipe with the preset fullness; If the grouting fullness in the pipeline is less than or equal to the preset fullness, it is determined that the accuracy of the prestressing construction does not meet the requirements, and the prestressing tensioning time is increased.

[0014] Furthermore, the grouting fullness in the pipeline is the ratio of the actual grouting volume in the pipeline to the target grouting volume.

[0015] Furthermore, the increase in the prestressing time is determined by the difference between the preset fullness and the grouting fullness in the pipeline.

[0016] Compared with the prior art, the beneficial effect of the present invention is that the method of the present invention adjusts the pouring speed of concrete according to the difference in the elongation of the slings during concrete pouring and not pouring. Since the slings are installed too tightly when the hanging basket is assembled, the bottom formwork frame will be in a tensile state when it is not bearing the load. When pouring concrete, the deformation of the slings will further increase, affecting the deformation control of the hanging basket. By reducing the pouring speed of concrete, the increase in the load applied to the hanging basket per unit time can be reduced, and the load borne by the hanging basket changes more slowly, so that the hanging basket structure has more time to adapt to the gradually increasing load, so that the deformation of the slings develops in a relatively slow process, and the vertical height of the hanging basket is adjusted according to the relative displacement of the beams at both ends of the bridge cantilever. Since the beams need to be temporarily locked before closure, if the temporary locking device is not firmly connected, the beams will be deformed during the closure process. After the joint is closed, the beam may undergo relative displacement, which will affect the stress state of the concrete in the joint section and cause dimensional deviation of the joint section. By increasing the vertical height of the hanging basket, an upward pulling force can be provided to the deflected beam, reducing the vertical relative displacement difference of the beams at both ends. The prestressing time is adjusted according to the fullness of the grouting in the pipeline. The wear of the chain of the grouting pump reduces the power transmission efficiency, resulting in a drop in pressure, which in turn leads to incomplete grouting, so that there is a gap between the prestressed tendons and the pipe wall. The prestressed tendons are susceptible to corrosion, resulting in prestress loss. By increasing the prestressing time, the prestressed tendons can be more fully tensioned to a certain extent, which helps to compensate for the prestress loss that has already occurred, so that the prestressed tendons reach a stress state closer to the design, improve the crack resistance and bearing capacity of the structure, and improve the control stability of the bridge deflection warning.

[0017] Furthermore, the method of the present invention adjusts the pouring speed of concrete by setting a preset first difference and a preset second difference. Since the sling is installed too tightly when the hanging basket is assembled, the bottom formwork frame will be in a tension state when it is not bearing load. When pouring concrete, the deformation of the sling will further increase, affecting the deformation control of the hanging basket. By reducing the pouring speed of concrete, the increase in load applied to the hanging basket per unit time can be reduced, and the load borne by the hanging basket changes more slowly, so that the hanging basket structure has more time to adapt to the gradually increasing load, so that the deformation of the sling develops in a relatively slow process, further improving the control stability of the bridge deflection warning.

[0018] Furthermore, the method of the present invention adjusts the vertical height of the hanging basket by setting a preset first displacement and a preset second displacement. Since the beam needs to be temporarily locked before the joint is closed, if the temporary locking device is not firmly connected, the beam may undergo relative displacement during and after the joint, affecting the stress state of the concrete in the joint section and causing dimensional deviation of the joint section. By increasing the vertical height of the hanging basket, an upward pulling force can be provided to the deflected beam, reducing the vertical relative displacement difference of the beams at both ends, and further improving the control stability of the bridge deflection warning.

[0019] Furthermore, the method of the present invention adjusts the tensioning time of the prestress by setting a preset fullness. Since the chain of the grouting pump is worn, the power transmission efficiency is reduced, resulting in a pressure drop, which in turn leads to incomplete grouting, resulting in gaps between the prestressed tendons and the pipe wall. The prestressed tendons are easily corroded, resulting in prestress loss. By increasing the tensioning time of the prestress, the prestressed tendons can be more fully tensioned to a certain extent, which helps to compensate for the prestress loss that has already occurred, so that the prestressed tendons reach a stress state closer to the design, improve the crack resistance and bearing capacity of the structure, and further improve the control stability of the bridge deflection warning. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is an overall flow chart of the deflection early warning control and deviation correction method for cantilever casting of a large-span continuous beam with a hanging basket according to an embodiment of the present invention; Figure 2 This is a logic flow chart for adjusting the concrete pouring speed of a deflection early warning control and deviation correction method for cantilever casting a large-span continuous beam using a hanging basket according to an embodiment of the present invention; Figure 3 This is a logic flow chart for adjusting the vertical height of a hanging basket in a method for early warning control and correction of deflection of a cantilevered bridge cast using a hanging basket of a large-span continuous beam according to an embodiment of the present invention; Figure 4 The present invention provides a logic flow chart for adjusting the prestressing time in a method for early warning control and correction of deflection of a cantilever cast bridge with a hanging basket of a large-span continuous beam according to an embodiment of the present invention. DETAILED DESCRIPTION

[0021] In order to make the objects and advantages of the present invention more clearly understood, the present invention is further described below in conjunction with embodiments; it should be understood that the specific embodiments described herein are merely used to explain the present invention and are not intended to limit the present invention.

[0022] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0023] It should be noted that, in the description of the present invention, terms such as "up", "down", "left", "right", "inside", and "outside" indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and does not indicate or imply that the device or element must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation on the present invention.

[0024] Furthermore, it should be noted that, in the description of the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; mechanical connections or electrical connections; direct connections or indirect connections through an intermediate medium; and internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0025] See also Figure 1 、 Figure 2 、 Figure 3 as well as Figure 4 As shown in the figure, they are respectively an overall flow chart of the deflection early warning control and deviation correction method for a cantilever cast bridge with a large-span continuous beam hanging basket according to an embodiment of the present invention, a logic flow chart for adjusting the concrete pouring speed, a logic flow chart for adjusting the vertical height of the hanging basket, and a logic flow chart for adjusting the prestressing time. A method for early warning control and deviation correction for a cantilever cast bridge with a large-span continuous beam hanging basket according to the present invention comprises: Step S1: Use a sling to lift the hanging basket to the bridge cantilever and assemble and fix it. Then, install the beam formwork, tie the steel bars, install the prestressed pipes, and pour the concrete. Install a deflection sensor and issue an alarm when the deflection exceeds the set threshold. Step S2, respectively obtaining the sling elongation when concrete pouring is completed and before pouring; Step S3, determining the control stability of the bridge deflection warning based on the difference in the sling elongation when the concrete is poured and when the concrete is not poured; Step S4: If the control stability does not meet the requirements, the concrete pouring speed is adjusted, or the reliability of the cantilever construction is determined based on the relative displacement of the beams at both ends of the bridge cantilever. If the reliability of the cantilever construction does not meet the requirements, the vertical height of the hanging basket is adjusted; Step S5: After pouring, the concrete is cured and prestressed anchor bundles are inserted. Prestressed bundle tensioning and pipe grouting operations are performed in sequence. The hanging basket is removed after the cantilever closure of the bridge at both ends. Step S6: adjusting the prestressing time based on the grouting fullness in the pipeline.

[0026] Specifically, the installation process of the hanging basket includes: (1) installing the hanging basket rail; (2) installing the hanging basket main girder; (3) installing the hanging basket main girder parallel joint and the main girder connecting channel steel; (4) installing the front crossbeam and steel sling; (5) installing the front and rear crossbeams of the bottom basket; (6) installing the bottom basket longitudinal beam; (7) installing the bottom crossbeam of the hanging basket; (8) installing the guide beam of the inner top plate of the hanging basket; (9) installing the inner top plate of the hanging basket; (10) installing the outer guide beam of the wing plate; (11) installing the side formwork.

[0027] Specifically, the prestressed pipe installation process involves the following: the prestressed steel strands are bundled and pulled through the pipe using a winch. The strands must be parallel and not cross-linked. Burrs must be removed to smooth the puller head. A mild soap solution can also be applied to some areas. Long strands are pulled through the pipe using a winch. After the wire rope is connected to the puller head, the strand is slowly threaded through the pipe using the winch and a diverting pulley.

[0028] Specifically, the prestressing and anchoring process includes: (1) Prestressing can only be carried out after the concrete strength of the beam body is not less than 90% of the design value, the elastic modulus is not less than 90% of the 28d elastic modulus of the concrete, and the curing age is not less than 7 days. The prestressing equipment uses a jack and oil pump that match the anchor. It should be calibrated according to the specifications before use to ensure the tensioning quality.

[0029] (2) The tensioning sequence of the prestressed steel strands shall be strictly in accordance with the sequence required by the construction drawings. When the prestressed steel strands are tensioned at both ends, the tensioning shall be symmetrical and synchronized, starting with the web strands and ending with the top plate strands, and proceeding symmetrically from the outside to the inside. The tensioning sequence of the steel bars in each beam section shall be: first the longitudinal prestressed steel strands of the beam section, then the transverse prestressed steel strands of the top plate, and finally the vertical prestressed steel strands of the web plate. The prestressing shall be controlled by dual means, with tensioning force being the primary control and elongation being the verification.

[0030] (3) Before tensioning, observe the elevation and make a record, then proceed with tensioning. Tensioning should be carried out strictly according to the design requirements. After tensioning is completed, measure the beam elevation again, make a record, and compare it with the elevation before tensioning to analyze the arching of the beam before and after tensioning.

[0031] (4) The longitudinal prestressing is tensioned simultaneously at both ends by jacks. The tensioning order is web bundle first, then top bundle, and the left and right symmetrical ends are tensioned simultaneously. The top plate horizontal and vertical prestressing steel bundles are tensioned at one end. The vertical prestressing adopts single bundle overall tensioning and secondary tensioning. The tensioning elongation calculation must be reviewed and signed by the project chief engineer before implementation. The tensioning elongation is controlled within ±6% of the design elongation. In the case of insufficient or excessive elongation, the cause must be identified and countermeasures must be taken to ensure effective stress. During the tensioning process, it is necessary to observe whether there is slippage or breakage of wires, and keep tensioning records.

[0032] (5) After the tensioning is completed, the excess part of the tensioning end shall be cut off with a handheld grinding wheel saw. At least 3 cm of the exposed end should be left during cutting. The grouting work shall be completed within 48 hours after the tensioning is completed.

[0033] Specifically, the grouting pipe layout process is as follows: In addition to grouting holes and discharge holes at both ends of the longitudinal prestressed pipe, a relay grouting hole must be installed in the middle according to the specifications. Each transverse and vertical prestressed pipe must have a separate grouting hole and exhaust hole, and a series connection is not allowed.

[0034] Specifically, the grouting process includes: (1) After tensioning is completed, pipeline grouting should be carried out within 48 hours. Pipeline grouting adopts vacuum grouting technology. The position of grouting nozzle and exhaust hole can be adjusted according to the actual needs of construction. Before grouting, compressed air should be used to remove impurities in the pipeline and remove accumulated water. Grouting should be carried out from the lowest grouting hole. The grouting should be full and dense.

[0035] (2) The grouting material shall be a finished bagged grouting material with the water-cement ratio determined through testing. The strength of the grouting material shall not be lower than the design strength of the beam concrete.

[0036] (3) Precautions for grouting: Before grouting, clean the prestressed pipe with clean water, and then use an air compressor to blow away the accumulated water in the pipe.

[0037] (4) Vacuum grouting process: Before grouting the hole, vacuum must be drawn. The vacuum machine must have sufficient power to ensure that the vacuum degree can be maintained at -0.06 to -0.1 MPa. After the vacuum degree stabilizes, the valve at the grouting end should be opened immediately, and the grouting pump should be turned on at the same time to carry out continuous grouting. During grouting, pay attention to whether there are any holes or leakages, and keep a record of the grouting. If there are any holes, immediately check the cause and deal with it in a timely manner.

[0038] Specifically, the process of dismantling the hanging basket includes: (1) Fixing the side formwork: Use the anchor holes reserved in the box beam flange plate to lock the side formwork of the hanging basket on both sides of the beam body; (2) Dismantle the bottom formwork platform: Use the four fall chains hanging on both sides of the front crossbeam and the hanging basket to lift the bottom formwork platform. At the same time, each lifting point is attached with a Φ18.5mm steel wire rope as a safety device; a dedicated person directs the four fall chains to rise and fall at the same time. After the fall chains have set the falling stroke, tighten the safety steel wire ropes, and the bottom formwork platform is temporarily suspended by the four steel wire ropes; loosen the fall chains, reset the new stroke and connect them firmly; loosen the safety steel wire ropes and use the fall chains to continue to lower the bottom formwork platform; repeat the above process until the bottom formwork platform falls steadily on the ground below; (3) Dismantling the side formwork: Use a crane to lift the side formwork. After confirming that it is stable, remove the side formwork fixing hanger. The outer sliding beam falls on the side formwork frame and is temporarily locked. Arrange a special person to command the crane to lift the two side formworks to the ground in turn. (4) Remove the cross-connection: First, temporarily tighten the main trusses on both sides with wire ropes or fall chains to prevent the main trusses from falling sideways; then remove the cross-connection between the two main trusses; (5) Dismantle the main truss: dismantle the main truss in the reverse order of installation; hoist the dismantled portal cross-connections and main trusses to the ground in the order of dismantling; (6) Dismantle the traveling device: dismantle the hanging basket sliding device, traveling track, and sleeper beam in turn; use a truck crane to lift them in batches onto a flatbed truck parked on the ground to ensure stability and firmness, and drive them to the designated location under the command of the commander; (7) Cleaning the site: Cut off the high-quality rolled threaded steel bars used for fixing, and fill and seal the reserved anchor holes with grouting material.

[0039] During implementation, the method of the present invention adjusts the pouring speed of concrete according to the difference in the elongation of the slings during concrete pouring and not pouring. Since when the hanging basket is assembled, if the slings are installed too tightly, the bottom formwork frame will be in a tensile state when it is not bearing load. When pouring concrete, the deformation of the slings will further increase, affecting the deformation control of the hanging basket. By reducing the pouring speed of concrete, the increase in load applied to the hanging basket per unit time can be reduced, and the load borne by the hanging basket changes more slowly, so that the hanging basket structure has more time to adapt to the gradually increasing load, and the deformation of the slings develops in a relatively slow process. The vertical height of the hanging basket is adjusted according to the relative displacement of the beams at both ends of the bridge cantilever. Since the beams need to be temporarily locked before the joint is closed, if the temporary locking device is not firmly connected, the beams may be deformed during and after the joint is closed. Relative displacement may occur, affecting the stress state of the concrete in the joint section and causing dimensional deviation of the joint section. By increasing the vertical height of the hanging basket, an upward pulling force can be provided to the deflected beam, reducing the vertical relative displacement difference of the beams at both ends, and adjusting the prestressing time according to the fullness of the grouting in the pipeline. The wear of the chain of the grouting pump reduces the power transmission efficiency, resulting in a pressure drop, which in turn leads to incomplete grouting, so that there is a gap between the prestressed tendons and the pipe wall. The prestressed tendons are susceptible to corrosion, resulting in prestress loss. By increasing the prestressing time, the prestressed tendons can be more fully tensioned to a certain extent, which helps to compensate for the prestress loss that has already occurred, so that the prestressed tendons reach a stress state closer to the design, improve the crack resistance and bearing capacity of the structure, and improve the control stability of the bridge deflection warning.

[0040] Specifically, determining the control stability of the bridge deflection early warning includes: Obtain the sling elongation during concrete pouring and the sling elongation before concrete pouring respectively, and calculate the difference between the sling elongation during concrete pouring and before concrete pouring; Comparing the difference in the sling elongation between when the concrete is poured and when the concrete is not poured with a preset first difference; If the difference in the sling elongation between when the concrete is poured and when the concrete is not poured is greater than the preset first difference, it is determined that the control stability of the bridge deflection warning does not meet the requirements.

[0041] Specifically, determining the reliability of the cantilever construction includes: Comparing the difference in the sling elongation between when the concrete is poured and when the concrete is not poured with the preset first difference and the preset second difference respectively; If the difference in the elongation of the sling during concrete pouring and before concrete pouring is greater than the preset first difference and less than or equal to the preset second difference, it is preliminarily determined that the reliability of the cantilever construction does not meet the requirements, and whether the reliability of the cantilever construction meets the requirements is determined based on the relative displacement of the beams at both ends of the bridge cantilever.

[0042] It can be understood that the three intervals divided by the preset first difference amount and the preset second difference amount correspond to three situations respectively: The first interval is when the difference in the suspender elongation between the concrete pouring and the concrete not pouring is less than or equal to the preset first difference, corresponding to the situation that: it is determined that the control stability of the bridge deflection warning meets the requirements; The second interval is when the difference in sling elongation between the concrete pouring and the unpoured state is greater than the preset first difference and less than or equal to the preset second difference. This corresponds to the situation where the beam needs to be temporarily locked before closure. If the temporary locking device is not securely connected, the beam may undergo relative displacement during and after closure, affecting the stress state of the concrete in the closure section and causing dimensional deviation in the closure section. The third interval is when the difference in sling elongation between when concrete is poured and when not poured is greater than the preset second difference. The corresponding situation is: when assembling the hanging basket, the sling is installed too tightly, causing the bottom formwork frame to be in a tension state when it is not bearing load. When pouring concrete, the deformation of the sling will further increase, affecting the deformation control of the hanging basket.

[0043] In practice, the preset first difference amount is generally selected in the range of [13 mm, 17 mm], and the preset second difference amount is generally selected in the range of [18 mm, 22 mm].

[0044] Preferably, the first preset difference amount is 15 mm, and the second preset difference amount is 20 mm.

[0045] Specifically, the difference in sling elongation between when concrete is poured and when concrete is not poured is the difference between the sling elongation when concrete is poured and the sling elongation when concrete is not poured.

[0046] In implementation, the method of the present invention determines the control stability of the bridge deflection warning by setting a preset first difference amount and a preset second difference amount, thereby reducing the impact of the reduction in the control accuracy of the bridge deflection warning due to inaccurate determination of the control stability of the bridge deflection warning, and further improving the control stability of the bridge deflection warning.

[0047] Specifically, adjusting the pouring speed of the concrete includes: Comparing the difference in sling elongation between when the concrete is poured and when the concrete is not poured with the preset second difference; If the difference in the length of the sling between when the concrete is poured and when the concrete is not poured is greater than the preset second difference, the pouring speed of the concrete is reduced.

[0048] Specifically, the reduction range of the concrete pouring speed is determined by the difference between the sling elongation difference when the concrete is poured and when the concrete is not poured and the preset second difference.

[0049] Specifically, when the difference between the sling elongation when pouring concrete and when not pouring concrete and the preset second difference is within 3mm, the concrete pouring speed is reduced to 0.9 times the original speed; when the difference between the sling elongation when pouring concrete and when not pouring concrete and the preset second difference exceeds 3mm, on the basis of being reduced to 0.9 times the original speed, the concrete pouring speed is reduced by 0.5m for every 1mm exceeding the preset second difference. 3 / h, for example, the difference between the sling elongation difference between the concrete pouring and the non-concrete pouring and the preset second difference is 5mm, and the current concrete pouring speed is 30m 3 / h, the reduced concrete pouring speed is 30×0.9-0.5×2=26m 3 / h.

[0050] During implementation, the method of the present invention adjusts the concrete pouring speed by setting a preset first difference and a preset second difference. Since the sling is installed too tightly when the hanging basket is assembled, the bottom formwork frame will be in a tension state when it is not bearing load. When pouring concrete, the deformation of the sling will further increase, affecting the deformation control of the hanging basket. By reducing the concrete pouring speed, the increase in load applied to the hanging basket per unit time can be reduced, and the load borne by the hanging basket changes more slowly, so that the hanging basket structure has more time to adapt to the gradually increasing load, so that the deformation of the sling develops in a relatively slow process, further improving the control stability of the bridge deflection warning.

[0051] Specifically, adjusting the vertical height of the hanging basket includes: Comparing the relative displacement of the beams at both ends of the bridge cantilever with the preset first displacement and the preset second displacement respectively; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement, it is determined that the reliability of the cantilever construction does not meet the requirements, wherein, If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement and less than or equal to the preset second displacement, increasing the vertical height of the hanging basket; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset second displacement, it is preliminarily determined that the accuracy of the prestressed construction does not meet the requirements, and whether the accuracy of the prestressed construction meets the requirements is determined based on the fullness of the grouting in the pipeline.

[0052] It can be understood that the three intervals divided by the preset first displacement amount and the preset second displacement amount correspond to three situations respectively: The first interval is when the relative displacement of the beams at both ends of the bridge cantilever is less than or equal to the preset first displacement, and the corresponding situation is: it is determined that the reliability of the cantilever construction meets the requirements; The second interval is when the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement and less than or equal to the preset second displacement. This corresponds to the situation where the beams need to be temporarily locked before closure. If the temporary locking device is not securely connected, the beams may undergo relative displacement during and after closure, affecting the stress state of the concrete at the closure section and causing dimensional deviations in the closure section. The third interval is when the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset second displacement. The corresponding situation is: due to the wear of the grouting pump chain, the power transmission efficiency is reduced, resulting in a pressure drop, which in turn leads to incomplete grouting, leaving gaps between the prestressed tendons and the pipe wall. The prestressed tendons are easily corroded, resulting in prestress loss.

[0053] In practice, the preset first displacement amount is generally selected from the range of [11 mm, 13 mm], and the preset second displacement amount is generally selected from the range of [14 mm, 16 mm].

[0054] Preferably, the preferred embodiment of the preset first displacement amount is 12 mm, and the preferred embodiment of the preset second displacement amount is 15 mm.

[0055] Specifically, the relative displacement of the beams at both ends of the bridge cantilever is the position change in the horizontal direction between the beams at both ends of the cantilever structure.

[0056] In implementation, the method of the present invention determines the reliability of cantilever construction by setting a preset first displacement and a preset second displacement, thereby reducing the impact of the decline in control stability of the bridge deflection warning due to inaccurate determination of the reliability of cantilever construction, and further improving the control stability of the bridge deflection warning.

[0057] Specifically, the increase in the vertical height of the hanging basket is determined by the difference between the relative displacement of the beams at both ends of the bridge cantilever and a preset first displacement.

[0058] Specifically, when the difference between the relative displacement of the beams at both ends of the bridge cantilever and the preset first displacement is within 2mm, the vertical height of the hanging basket is increased to 1.1 times the original value; when the difference between the relative displacement of the beams at both ends of the bridge cantilever and the preset first displacement exceeds 2mm, on the basis of increasing to 1.1 times the original value, the vertical height of the hanging basket is increased by 0.05m for every 1mm exceeding. For example, the difference between the relative displacement of the beams at both ends of the bridge cantilever and the preset first displacement is 4mm, the current vertical height of the hanging basket is 4m, and the increased vertical height of the hanging basket is 4×1.1+0.05×2=4.5m.

[0059] During implementation, the method of the present invention adjusts the vertical height of the hanging basket by setting a preset first displacement and a preset second displacement. Since the beam needs to be temporarily locked before the joint is closed, if the temporary locking device is not firmly connected, the beam may undergo relative displacement during and after the joint, affecting the stress state of the concrete in the joint section and causing dimensional deviation of the joint section. By increasing the vertical height of the hanging basket, an upward pulling force can be provided to the deflected beam, reducing the vertical relative displacement difference of the beams at both ends, and further improving the control stability of the bridge deflection warning.

[0060] Specifically, adjusting the tensioning time of the prestress includes: Obtain the actual grouting volume and target grouting volume in the pipeline respectively, and calculate the grouting fullness in the pipeline; Comparing the grouting fullness in the pipeline with a preset fullness; If the grouting fullness in the pipeline is less than or equal to the preset fullness, it is determined that the accuracy of the prestressing construction does not meet the requirements, and the prestressing tensioning time is increased.

[0061] It is understandable that the two intervals of preset fullness correspond to two situations: The first interval is when the grouting fullness in the pipeline is less than or equal to the preset fullness. This corresponds to the following situation: due to the wear of the grouting pump chain, the power transmission efficiency is reduced, resulting in a pressure drop, which in turn leads to incomplete grouting, leaving gaps between the prestressed tendons and the pipeline wall. The prestressed tendons are susceptible to corrosion, resulting in prestress loss. The second interval is that the grouting fullness in the pipeline is greater than the preset fullness, and the corresponding situation is: determining that the accuracy of the prestressed construction meets the requirements.

[0062] In practice, the preset fullness is generally selected in the range of [88%, 92%].

[0063] Preferably, the preferred embodiment of the preset fullness is 90%.

[0064] In implementation, the method of the present invention determines the accuracy of prestressed construction by setting a preset fullness, thereby reducing the impact of the decline in control stability of bridge deflection warning due to inaccurate determination of the accuracy of prestressed construction, and further improving the control stability of bridge deflection warning.

[0065] Specifically, the grouting fullness in the pipeline is the ratio of the actual grouting volume in the pipeline to the target grouting volume.

[0066] Specifically, the increase in the prestressing time is determined by the difference between the preset fullness and the grouting fullness in the pipeline.

[0067] Specifically, when the difference between the preset fullness and the grouting fullness in the pipeline is within 5%, the prestressing tensioning time is increased to 1.2 times of the original; when the difference between the preset fullness and the grouting fullness in the pipeline exceeds 5%, on the basis of being increased to 1.2 times of the original, the prestressing tensioning time is increased by 1 minute for every 1% exceeding it. For example, the difference between the preset fullness and the grouting fullness in the pipeline is 7%, the current prestressing tensioning time is 5 minutes, and the increased tensioning time is 5×1.2+1×2=8 minutes.

[0068] During implementation, the method of the present invention adjusts the tensioning time of prestress by setting a preset fullness. Since the chain of the grouting pump is worn, the power transmission efficiency is reduced, resulting in a pressure drop, which in turn leads to incomplete grouting, so that there is a gap between the prestressed tendons and the pipe wall. The prestressed tendons are easily corroded, resulting in prestress loss. By increasing the tensioning time of the prestress, the prestressed tendons can be more fully tensioned to a certain extent, which helps to compensate for the prestress loss that has already occurred, so that the prestressed tendons reach a stress state closer to the design, improve the crack resistance and bearing capacity of the structure, and further improve the control stability of the bridge deflection warning.

[0069] Thus far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art may make equivalent changes or substitutions to the relevant technical features, and the technical solutions after such changes or substitutions will fall within the scope of protection of the present invention.

Claims

1. A method for early warning control and deviation correction of deflection of a cantilever cast bridge with a large-span continuous beam hanging basket, characterized in that: include: Use slings to lift the hanging basket to the bridge cantilever and assemble and fix it. Then install the beam formwork, tie the steel bars, install the prestressed pipes, and pour the concrete. Install the deflection sensor and issue an alarm when the deflection exceeds the set threshold. Obtain the sling elongation when concrete pouring is completed and before pouring respectively; Determine the control stability of bridge deflection warning based on the difference in suspender elongation between concrete pouring and unconcrete pouring; If the control stability does not meet the requirements, the concrete pouring speed is adjusted, or the reliability of the cantilever construction is determined based on the relative displacement of the beams at both ends of the bridge cantilever. If the reliability of the cantilever construction does not meet the requirements, the vertical height of the hanging basket is adjusted; After pouring, the concrete is cured and prestressed anchor bundles are inserted. Prestressed bundle tensioning and pipe grouting operations are carried out in sequence. The hanging basket is removed after the cantilever closure of the bridge at both ends. The prestressing time is adjusted based on the grouting fullness in the pipe.

2. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams using a hanging basket according to claim 1 is characterized in that: Determining the control stability of the bridge deflection warning includes: Comparing the difference in sling elongation between when concrete is poured and when concrete is not poured with a preset first difference; If the difference in the sling elongation between when the concrete is poured and when the concrete is not poured is greater than the preset first difference, it is determined that the control stability of the bridge deflection warning does not meet the requirements.

3. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 2 is characterized in that: Determine the reliability of the cantilever construction, including: Comparing the difference in the sling elongation between when the concrete is poured and when the concrete is not poured with the preset first difference and the preset second difference respectively; If the difference in the elongation of the sling during concrete pouring and before concrete pouring is greater than the preset first difference and less than or equal to the preset second difference, it is preliminarily determined that the reliability of the cantilever construction does not meet the requirements, and whether the reliability of the cantilever construction meets the requirements is determined based on the relative displacement of the beams at both ends of the bridge cantilever.

4. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 3 is characterized in that: Adjusting the pouring speed of the concrete includes: Comparing the difference in sling elongation between when the concrete is poured and when the concrete is not poured with the preset second difference; If the difference in the length of the sling between when the concrete is poured and when the concrete is not poured is greater than the preset second difference, the pouring speed of the concrete is reduced.

5. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 4 is characterized in that: The reduction range of the concrete pouring speed is determined by the difference between the sling elongation difference when the concrete is poured and when the concrete is not poured and the preset second difference.

6. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 5 is characterized in that: Adjusting the vertical height of the hanging basket includes: Comparing the relative displacement of the beams at both ends of the bridge cantilever with the preset first displacement and the preset second displacement respectively; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement, it is determined that the reliability of the cantilever construction does not meet the requirements, wherein, If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset first displacement and less than or equal to the preset second displacement, increasing the vertical height of the hanging basket; If the relative displacement of the beams at both ends of the bridge cantilever is greater than the preset second displacement, it is preliminarily determined that the accuracy of the prestressed construction does not meet the requirements, and whether the accuracy of the prestressed construction meets the requirements is determined based on the fullness of the grouting in the pipeline.

7. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 6 is characterized in that: The increase in the vertical height of the hanging basket is determined by the difference between the relative displacement of the beams at both ends of the bridge cantilever and a preset first displacement.

8. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 7 is characterized in that: Adjusting the tensioning time of the prestressing force includes: Compare the grouting fullness in the pipe with the preset fullness; If the grouting fullness in the pipeline is less than or equal to the preset fullness, it is determined that the accuracy of the prestressing construction does not meet the requirements, and the prestressing tensioning time is increased.

9. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams according to claim 8 is characterized in that: The grouting fullness in the pipeline is the ratio of the actual grouting volume in the pipeline to the target grouting volume.

10. The deflection early warning control and deviation correction method for cantilever casting bridges with large-span continuous beams using a hanging basket according to claim 9 is characterized in that: The increase in the prestressing time is determined by the difference between the preset fullness and the grouting fullness in the pipeline.

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