Wet joint and box girder coordinated temperature control system and low-temperature construction method

Abstract

The invention provides a wet joint and box girder coordinated temperature control system and a low-temperature construction method, relates to the field of bridges, and aims to solve the problem of damage caused by overlarge temperature difference in a box girder due to the fact that a wet joint and an adjacent flange plate area are heated in a low-temperature environment at present. The second heating assembly is configured to heat a web, a top plate and a bottom plate of the box girder body, synchronous temperature rise and dynamic temperature adjustment of the box girder and the wet joint are achieved, the temperature difference among the wet joint, a flange plate and the box girder body is reduced, and a proper temperature gradient can be formed between the wet joint and the box girder through the first heating assembly and the second heating assembly; the problems of interface cracks and strength imbalance caused by uncoordinated temperature difference between the wet joint and the box girder are reduced, and the integrity and durability of a bridge structure are guaranteed.

Description

Technical Field

[0001] The present invention relates to the field of bridges, and in particular to a wet joint and box girder coordinated temperature control system and a low-temperature construction method. Background Art

[0002] Most bridges utilize prefabricated box girders with wet joints. During construction in winter or in extremely cold regions, the wet joints between the box girders are cast in-situ. Without a sufficiently high curing temperature, these joints can suffer from quality issues such as concrete frost heave, cracks, structural delamination, and surface frost. To address these issues, existing technologies provide construction and curing equipment and methods for wet joints. These devices, by placing insulation layers above and below the wet joints, heat and insulate the wet joint area, ensuring that the cast wet joints remain within the required curing temperature and improving curing effectiveness during construction in low-temperature environments.

[0003] Even after installing heating and insulation facilities above and below the wet joint, the temperature at the joint between the side of the wet joint and the box girder flange plate is still difficult to adjust. Only the heating and insulation of the wet joint body is focused on, while the temperature status of the prefabricated beam connected to it is ignored. Since the temperature of precast beams such as box beams is relatively low in low temperature environments, if the concrete poured at the wet joint position heats up under the heating effect of the upper and lower insulation layers, while the flange plates at the end of the box beam remain low, a large temperature difference will be formed between the wet joint and the box beam flange plates, resulting in uneven thermal stress at the joint position of the flange plates and the wet joint, which can easily cause early damage such as cracks, debonding or interface peeling. By increasing the insulation layers above and below the wet joint and heating the wet joint and the box beam flange plates at the same time, the temperatures at the joint position of the wet joint and the flange plates can be made consistent, thereby reducing uneven thermal stress and improving the maintenance quality of the wet joint. However, after heating the flange plates of the box beam, the main part of the box beam still remains low in the low temperature environment, and there is still a large temperature difference between the flange plates and the main body of the box beam, which causes uncoordinated deformation of the precast box beam, induces damage to the internal structure of the box beam, affects the stability of the box beam structure, and endangers the safety of the bridge. Summary of the invention

[0004] The purpose of the present invention is to address the defects of the existing technology and provide a wet joint and box girder coordinated temperature control system and a low-temperature construction method, aiming to solve the problem that only the wet joint body and the vicinity are heated and insulated in a low-temperature environment, resulting in a large temperature difference between the box girder flange plate and the box girder body, causing uncoordinated deformation, leading to internal damage of the already formed box girder, and exacerbating the risk of box girder cracks.

[0005] The first object of the present invention is to provide a coordinated temperature control system for wet joints and box beams, which adopts the following scheme: include: A first heating assembly is arranged in the flange plate of the box girder and the wet joint area of the adjacent box girder, and is used to heat the wet joint and the box girder flange plate adjacent to the wet joint; A second heating assembly is arranged on the inner wall of the box girder and is used to heat the box girder web, box girder top plate and box girder bottom plate; The temperature control component includes a controller and a temperature detection element. The temperature detection element is arranged on the box girder and the wet joint, and obtains the box girder temperature and the wet joint temperature respectively and sends them to the controller. The controller is used to adjust the operating parameters of the first heating component and the second heating component so that the temperature difference between the box girder and the wet joint is controlled within a set range.

[0006] Furthermore, it also includes a thermal insulation and heating component, which is attached to the outer walls of the box beam web and the box beam bottom plate.

[0007] Furthermore, the thermal insulation and heating assembly includes an electric heating film and a thermal insulation layer. The electric heating film is attached to the box beam, and the thermal insulation layer is arranged on a side of the electric heating film away from the box beam.

[0008] Furthermore, the second heating assembly includes an electric heating film attached to the inner wall of the box beam, and the electric heating film is continuously distributed and covers the top, bottom and sides of the inner wall of the box beam.

[0009] Furthermore, the first heating assembly is arranged on the upper surface and the bottom surface of the flange plate, and is also arranged on the top and the bottom of the wet joint area.

[0010] A second object of the present invention is to provide a low-temperature construction method for coordinating wet joints and box girders, using the wet joint and box girder coordinated temperature control system provided by the first object, comprising: Arrange the second heating assembly in the box girder and hoist the box girder into place; Install a first heating assembly on the inner side of the box girder flange plate and the wet joint formwork, and arrange temperature detection elements in the box girder and wet joint areas; Carry out the grouting construction of wet joint concrete, and fully combine the newly poured concrete with the end of the box beam flange plate; During the concrete curing period, the first and second heating components are continuously operated to synchronously heat the box girder and wet joint area, and the temperature difference between the box girder and the wet joint is controlled within the set range, buffering the thermal stress gradient and synchronously raising the temperature of the junction area between new and old concrete; After the concrete curing is completed, the joint strength is tested. When the strength reaches the required level, the wet joints and the box girder coordinated temperature control system are removed.

[0011] Furthermore, when the box girder is prefabricated, after the box girder reinforcement cage is tied and before the box girder concrete is poured, the second heating system is fixed on the box girder reinforcement cage, the outlet end of the second heating system is waterproof sealed, and the temperature control component is connected during the concrete curing period of the wet joint area.

[0012] Furthermore, after hoisting the box girder, ensure that the adjacent box girders are correctly connected, clean the wet joint area and the wet joints where the box girders are connected, and ensure that the interface between the new and old concrete is clean.

[0013] Furthermore, during the concrete curing period, the first heating component and the second heating component adopt a step-by-step temperature increase, first preheating and then gradually heating.

[0014] Furthermore, during the concrete curing period, the temperatures of the box girder and the wet joint area are periodically collected, and the power of the first heating assembly and the second heating assembly are adjusted according to the temperatures.

[0015] Compared with the prior art, the present invention has the following advantages and positive effects: In response to the problem that heating the wet joints and adjacent flange areas in low-temperature environments causes excessive temperature differences inside the box girder and causes damage, a first heating component is configured to heat the wet joints and adjacent flanges, and a second heating component is configured to heat the web, top plate and bottom plate of the box girder body, so as to achieve synchronous heating and dynamic temperature adjustment of the box girder and the wet joints, reduce the temperature difference between the wet joints, flanges and box girder body, and utilize the first heating component and the second heating component to form a suitable temperature gradient between the wet joints and the box girder, reduce the interface cracks and strength imbalance caused by the inconsistent temperature difference between the wet joints and the box girder, and ensure the integrity and durability of the bridge structure.

[0016] In order to solve the problem of uncoordinated deformation between the interior and surface of the box girder due to heat transfer efficiency problems when heating the box girder, a second heating component is set inside the box girder to heat from the inside to the outside, and an insulation heating component is set on the outer wall of the box girder to heat from the outside to the inside. It can also provide insulation, so that the temperature of the large-volume box girder body tends to be consistent, reducing the internal damage of the box girder body caused by temperature difference, and can improve the heating efficiency, which is suitable for low-temperature environments.

[0017] Not only is the concrete in the wet joint area heated and insulated, but the temperature of the box girder flange plate connected thereto and the temperature of the box girder body excluding the flange plate are also controlled synchronously. Since the volume of the wet joint and the flange plate is smaller than that of the box girder body, when heating is carried out at the same time, the temperature gradient effect naturally formed by the volume difference between the wet joint and the box girder can be utilized. The flange plate and the box girder body are heated at the same time, and the flange plate area is first raised to the first temperature that drives the hydration of the joint, and the box girder body is slowly raised to a second temperature lower than the first temperature to reduce energy consumption. When the temperature difference is too large or the outer surface cools down, the insulation and heating components can also provide short-term heat supplementation to form a gradient temperature control strategy, avoiding the time-consuming and energy-consuming problem of traditional overall heating, and also avoiding the problem of cracks induced by surface heat and internal cold.

[0018] Multi-point temperature sensing elements are used to collect temperatures in the box girder and wet joint areas. A closed-loop controller regulates the temperature difference between the flange plate and the inner core of the box girder to a safe range, significantly reducing the risk of temperature cracks caused by local temperature discrepancies. This ensures concrete strength in the wet joint area, improving joint bonding quality and crack resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 Schematic diagram of a coordinated temperature control system for wet joints and box girders in one or more embodiments of the present invention.

[0021] Figure 2 Schematic diagram of the distribution positions of wet joints and box girders in one or more embodiments of the present invention.

[0022] Figure 3 The present invention is a flowchart of a low-temperature construction method for coordinating wet joints with box girders in one or more embodiments of the present invention.

[0023] Figure 4 Schematic diagram comparing coordinated temperature-controlled curing and natural curing of wet joints and box girders in one or more embodiments of the present invention.

[0024] Among them, 1. box girder; 2. temperature sensor; 3. thermal insulation and heating assembly; 4. second heating assembly; 5. wet joint; 6. first heating assembly; 7. flange plate; 8. web plate; 9. top plate; 10. bottom plate. DETAILED DESCRIPTION

[0025] Example 1 In a typical embodiment of the present invention, Figure 1 - Figure 2 , a coordinated temperature control system of wet joints and box girders is proposed.

[0026] When the wet joint 5 of the bridge is constructed in a low-temperature environment, the existing technology only focuses on the heating and heat preservation of the wet joint 5 itself and the adjacent flange plate 7, but ignores the temperature state of the main structure of the box girder 1. After the wet joint 5 is poured, if only the upper and lower parts of it are heated and heat-preserved, the temperature of the wet joint 5 rises, while the flange plate 7 of the box girder 1 connected to it remains at a low temperature due to the low-temperature environment. A temperature difference is formed between the two, resulting in uneven thermal stress at the butt joint position, causing early damages such as cracks and debonding. If the heating range is extended to the flange plate 7, at this time, the temperature of the flange plate 7 rises, but the main body of the box girder 1 (such as the web 8, the top plate 9, and the bottom plate 10) is still in a low-temperature state. A new temperature difference will be formed between the flange plate 7 and the main body of the box girder 1, resulting in inconsistent deformation of the precast box girder 1 and inducing damage to the internal structure of the box girder 1, endangering the safety of the bridge. Based on this, this embodiment provides a coordinated temperature control system for the wet joint and the box girder. Through the first heating component 6 and the second heating component 4 for zone heating, the first heating component 6 is arranged in the area of the flange plate 7 and the wet joint 5, directly heating the wet joint 5 and its adjacent flange plate 7 to ensure that the temperatures of the two rise synchronously and reduce the temperature difference between the two; the second heating component 4 is arranged on the inner cavity wall of the box girder 1 to heat the web 8, the top plate 9, and the bottom plate 10 of the box girder 1, so that the temperature of the main body of the box girder 1 is consistent with the temperatures of the flange plate 7 and the wet joint 5, eliminating the temperature difference between the flange plate 7 and the main body of the box girder 1. By synchronously heating the wet joint 5, the flange plate 7, and the main body of the box girder 1, a gradient distribution within the temperature difference damage range is formed for the temperatures of each part, avoiding uneven thermal stress caused by the temperature difference and reducing early damages such as cracks, debonding, and interface peeling.

[0027] As Figure 1 - Figure 4 shown, the coordinated temperature control system for the wet joint and the box girder includes a first heating component 6, a second heating component 4, and a temperature control component. The first heating component 6 is arranged in the area of the flange plate 7 and the wet joint 5, directly heating the wet joint 5 and its adjacent flange plate 7. The second heating component 4 is arranged on the inner cavity wall of the box girder 1 to heat the web 8, the top plate 9, and the bottom plate 10. The temperatures of each part of the box girder 1 and the wet joint 5 are monitored in real time through temperature detection elements, such as the temperatures of the web 8, the bottom plate 10, and the top plate 9, and the data is transmitted to the controller. The controller dynamically adjusts the operating parameters of the first heating component 6 and the second heating component 4, such as the heating power and duration, to ensure that the temperature difference between the whole box girder 1 and the wet joint 5 is controlled within the set range, forming a uniform temperature field.

[0028] Eliminate the excessive temperature difference between the flange plate 7 and the main body of the box girder 1, control the temperature difference within the set range, prevent inconsistent deformation of each part of the precast box girder 1 due to excessive temperature difference, avoid damage to the internal structure of the box girder 1, and improve the stability and safety of the bridge structure. Form an overall uniform curing temperature field for the wet joint 5 area to ensure that the wet joint 5 concrete cures at an appropriate temperature, improve the connection strength between the wet joint 5 and the box girder 1, and ensure the construction quality in a low-temperature environment.

[0029] Among them, the box girder 1 involved in this embodiment is a prefabricated and assembled structure in sections, that is, the box girder 1 applicable to medium and small span bridges is a prefabricated structure. Therefore, there is a need for construction wet joints 5. For the convenience of describing the temperature gradient distribution, in this embodiment, the box girder 1 refers to the entire beam body, and the main body of the box girder 1 refers to the general name of other parts of the box girder 1 except the flange plates 7 on both sides of the box girder 1, including the web 8, the bottom plate 10 and the top plate 9, which together enclose a box-shaped structure.

[0030] In this embodiment, for the structural damage problem caused by the temperature difference between the wet joint 5 and each part of the box girder 1 during low-temperature construction, a strategy of zoning heating and intelligent temperature control is adopted. By synergistically heating the wet joint 5, the flange plate 7 and the main body of the box girder 1, a uniform temperature field is constructed, the temperature difference stress is eliminated, the temperature of multiple regions is synchronously controlled, and new temperature differences caused by only heating a local area are avoided. Instead, the temperature linkage adjustment of the wet joint 5, the flange plate 7 and the main body of the box girder 1 is realized through the first heating component 6 and the second heating component 4. The temperature control component is used to monitor the temperature data in real time, and the heating power is closed-loop controlled by the controller to ensure that the temperature difference is within a safe range.

[0031] The first heating component 6 covers the upper surface, the lower surface of the flange plate 7 and the pouring area of the wet joint 5. The first heating component 6 can adopt a flexible electric heating film, a heating cable or an infrared heating plate, and is attached to the template surface of the flange plate 7 and the wet joint 5 to ensure uniform heat conduction. It can also be wrapped with a heat insulation layer (such as rock wool, polyurethane foam) on the outer layer to reduce heat loss and improve the heating efficiency.

[0032] The wet joint 5 concrete is directly heated by the first heating component 6 to keep it at a suitable curing temperature and avoid frost heaving and cracking. The first heating component 6 synchronously heats the flange plate 7 to eliminate the temperature difference between the wet joint 5 and the flange plate 7 and reduce the thermal stress at the butt joint position.

[0033] The second heating component 4 is a heating unit for the main body of the box girder 1, which is installed on the inner cavity wall of the box girder 1, corresponding to the inner sides of the web 8, the top plate 9 and the bottom plate 10. The web 8, the top plate 9 and the bottom plate 10 are heated to make the temperature of the main body of the box girder 1 rise synchronously with the temperature of the flange plate 7 and the wet joint 5, reduce the temperature difference between the flange plate 7 and the main body of the box girder 1, avoid the inconsistent deformation of the box girder 1 caused by too large temperature difference between the flange plate 7 and the main body of the box girder 1, and ensure the internal structural stability of the precast box girder 1.

[0034] The temperature control component is an intelligent monitoring and adjustment unit. The temperature control component includes temperature detection elements, which are arranged at the center of the wet joint 5, the surface of the flange plate 7 and the inner cavity of the box girder 1 to collect temperature data in real time. The controller receives the temperature signal, compares the preset temperature difference threshold, and dynamically adjusts the power of the first heating component 6 and the second heating component 4.

[0035] The temperature detection element transmits data to the controller in real time to form dynamic temperature field data. When the temperature difference between the wet joint 5 and the flange plate 7 exceeds the threshold value, the controller increases the power of the first heating component 6; when the temperature difference between the flange plate 7 and the main body of the box girder 1 exceeds the standard, the second heating component 4 is started or its power is increased. It is also possible to achieve precise control of the heating power through algorithms such as PID regulation to ensure that the temperature difference is stable within a safe range.

[0036] As Figure 1 , Figure 2 shown, the coordinated temperature control system for the wet joint and the box girder further includes a heat preservation and heating component 3, which is composed of an electric heating film and a heat preservation layer and is attached to the outer walls of the web 8 and the bottom plate 10. The electric heating film is in direct contact with the outer wall of the box girder 1 and can quickly transfer heat to the structure of the box girder 1; the heat preservation layer is arranged outside the electric heating film, effectively preventing heat from dissipating outward and playing a good heat preservation role.

[0037] The heat preservation and heating component 3 mainly heats and insulates the outer walls of the web 8 and the bottom plate 10, making up for the deficiency of only heating from the inner cavity by the second heating component 4. The heat preservation and heating component 3 can be used to heat the web 8 and the bottom plate 10 when the temperature difference between the flange plate 7 and the web 8 and the bottom plate 10 is about to exceed the safety threshold. In a low-temperature environment, the outer wall of the box girder 1 is in direct contact with the low-temperature air outside, and the heat loss is fast. The heat preservation and heating component 3 can effectively reduce the heat loss, increase the overall temperature of the box girder 1, further reduce the temperature difference with the flange plate 7 and the wet joint 5, reduce the generation of thermal stress, and ensure the stability of the structure of the box girder 1. At the same time, its heat preservation characteristics help to maintain the stability of the temperature of the box girder 1 and reduce the energy consumption of the temperature control system.

[0038] As Figure 1 shown, the second heating component 4 can be in the form of an electric heating film, an electric heating cable, an infrared heating plate, etc. In this embodiment, taking the electric heating film as an example, a continuously distributed electric heating film covers the top, bottom and sides of the inner cavity of the box girder 1. The continuous arrangement method can ensure that the main structure of the box girder 1 is heated more evenly compared with the non-continuous arrangement, avoiding the situation of local overheating or overcooling.

[0039] The continuously covered electric heating film enables heat to be transferred to all parts of the web 8, the top plate 9 and the bottom plate 10 more efficiently. Combining with the effect of the heat preservation and heating component 3 on the outer wall of the box girder 1, it realizes all-round heating from the inside to the outside of the box girder 1, speeds up the heating rate of the main body of the box girder 1, and more precisely controls the temperature difference between the main body of the box girder 1 and the flange plate 7 and the wet joint 5, thereby effectively reducing the inconsistent deformation of the box girder 1 caused by the temperature difference and improving the overall effect of the temperature control system.

[0040] The first heating component 6 is not only arranged on the upper and lower surfaces of the flange plate 7, but also extends to the top and bottom of the wet joint 5 area, realizing the wrapping of the wet joint 5 and its adjacent flange plate 7, ensuring that the wet joint 5 can be fully heated and insulated after pouring, guaranteeing the curing of concrete at an appropriate temperature, and preventing problems such as frost heaving and cracking.

[0041] The first heating component 6 cooperates with the heat preservation and heating component 3 and the second heating component 4 to heat and insulate the box girder 1 and the wet joint 5 from different directions. The first heating component 6 ensures the temperature stability of the wet joint 5 and the flange plate 7, while the second heating component 4 and the heat preservation and heating component 3 maintain the temperature of the main body of the box girder 1. The three work together to jointly construct a temperature field with a decreasing temperature gradient, effectively reducing the temperature difference between components, reducing thermal stress and deformation, and improving the construction quality and structural safety of the bridge.

[0042] The first heating component 6, the heat preservation and heating component 3, and the second heating component 4 carry out heating and insulation from multiple parts such as the inside and outside of the box girder 1, the wet joint 5, and the flange plate 7 through different arrangements and functions, forming a three-dimensional temperature control network, which can more accurately control the temperature of each part of the box girder 1 and control the temperature difference within a smaller range.

[0043] In this embodiment, the electric heating film, heating cable, electric heating cable, etc. are installed at the set positions through fixing parts such as fixing plates and fixing frames. The outgoing ends of the second heating component 4 and the heat preservation and heating component can pass through the reserved pipes and be connected to the controller. The controller can be connected to the power supply, supplying energy to each component while regulating its working state.

[0044] In this embodiment, when using an electric heating cable as the first heating component 6 or the second heating component 4, an S-shaped wiring method is adopted, the cable spacing is controlled within 150 mm, and after passing through a high-temperature resistant HDPE pipe, it is tied to the stirrups to avoid displacement during vibration.

[0045] When fixing the electric heating film, for the part of the box girder 1, an L-shaped fixing frame (made of aluminum alloy) is used to press the edge of the heating film at an interval of every 0.5 m, and 3MVHB tape is used for pasting to enhance the fixing effect. For the wet joint 5 area, the heating film is embedded in the groove of the joint formwork, and a sandwich structure of formwork - heating film - heat preservation cotton is adopted to ensure tight fitting. The temperature detection element can adopt the temperature sensor 2. For the temperature sensors 2 arranged on the surfaces of the box girder 1 and the wet joint 5, Φ5 stainless steel sleeves are implanted through drilling, and after filling with thermal conductive silica gel, the temperature sensors 2 are inserted to ensure the coupling efficiency. For the temperature sensors 2 buried inside the box girder 1 and the wet joint 5, they are pre-embedded during the concrete pouring.

[0046] Temperature sensors 2 are arranged in layers to capture the temperature difference between inside and outside. Before pouring, the sensitivity of the temperature sensors 2 is tested, and the measurement accuracy is controlled within ±1°C. It is understood that the temperature monitoring signals and the control loops of the first heating component 6, the second heating component 4, and the insulation heating component 3 can also be connected to the controller, with a pre-set PID control algorithm. A wireless communication module interface is reserved to enable remote monitoring and data recording.

[0047] The insulation layer of the heat preservation and heating assembly 3 can be made of 40mm polyurethane rigid foam insulation board. Alternatively, the insulation board can be covered with flame-retardant waterproof canvas and fixed with aluminum alloy press frames, locked every 0.5m. Under normal operating conditions, it is in insulation mode, and automatic heating is only performed when the temperature of the web 8 or bottom plate 10 falls below the threshold.

[0048] In other optional embodiments, modular heating film units can also be used to quickly splice them by magnetic attraction.

[0049] The comprehensive heating and insulation design effectively avoids thermal stress and uncoordinated deformation caused by temperature differences. This not only protects the connection between the wet joint 5 and the flange plate 7, but also enhances the stability of the main structure of the box girder 1, reduces the risk of damage to the internal structure of the box girder 1, and extends the service life of the bridge. In severe cold environments, the thermal insulation effect of the insulation and heating assembly 3 and the coordinated heating function of each component enable the system to better cope with harsh environments, ensure smooth bridge construction, and reduce the adverse effects of low temperatures on construction quality.

[0050] Example 2 In another typical embodiment of the present invention, Figure 1 - Figure 4 , a low-temperature construction method for coordinating wet joints and box girders is provided, using the wet joint and box girder coordinated temperature control system as in Example 1.

[0051] A low-temperature construction method for coordinating wet joints with box beams, comprising: Arrange the second heating assembly 4 in the box beam 1 and hoist the box beam 1 into place; Install a first heating assembly 6 on the inner side of the flange plate 7 and the wet joint 5 template, and arrange a temperature detection element in the box girder 1 and the wet joint 5 area; Carry out the grouting construction of wet joint 5 concrete, and fully combine the newly poured concrete with the end of the flange plate 7; During the concrete curing period, the first heating assembly 6 and the second heating assembly 4 are continuously operated to synchronously heat the box girder 1 and the wet joint 5, and the temperature difference between the box girder 1 and the wet joint 5 is controlled within a set range to buffer the thermal stress gradient and synchronously heat the interface area between the new and old concrete. After the concrete curing is completed, the joint strength is tested. When the strength reaches the required level, the wet joints and the box girder coordinated temperature control system are removed.

[0052] In this embodiment, the low-temperature environment refers to the construction conditions where the daily average temperature ≤ 5°C or the minimum temperature ≤ 0°C. In this environment, the hydration reaction of concrete significantly slows down. If temperature control measures are not taken, problems such as frost heaving and insufficient strength are likely to occur.

[0053] Specifically, as Figure 1 - Figure 4 shown, the low-temperature construction method for the coordination of wet joints and box girders will be described in detail.

[0054] After the steel cage of the box girder 1 is tied and before the concrete is poured, the second heating component 4 (electric heating film or cable) is fixed inside the steel cage at the designed spacing and fixed with nylon ties or metal buckles. The outlet end is double waterproofed with waterproof tape and sealant to prevent water seepage during pouring. After pouring, a precast box girder 1 with the second heating component 4 is obtained.

[0055] Lift the precast box girder 1 to the predetermined position, ensure that the docking joint error between adjacent girders ≤ 5mm, and the bottom of the girder is in close contact with the bearing. Remove the sundries, accumulated water and floating slurry in the wet joint 5 area. When the flatness of the end face of the flange 7 is out of tolerance (> 3mm), use a grinding machine to grind it and blow it clean with a high-pressure air gun to ensure that the bonding surface of the new and old concrete is clean and free of oil stains.

[0056] Lay an electric heating film on the upper and lower surfaces of the flange 7 and the inner side of the wet joint 5 formwork as the first heating component 6, press and connect it with an L-shaped aluminum alloy fixing frame, and seal the edge with 3MVHB tape to ensure close fitting with the concrete surface.

[0057] Paste an electric heating film on the outer surfaces of the web 8 and the bottom plate 10, and cover the outside with a 40mm thick polyurethane insulation board as the insulation layer, fix it with an aluminum alloy pressing frame, and establish an insulation heating component 3 on the outer wall of the box girder 1.

[0058] Arrange temperature sensors 2 on the upper and lower surfaces of the flange 7, inside the box girder 1 and at the center of the wet joint 5. Fiber Bragg grating sensors are arranged at 1 measurement point every 30cm along the length direction of the wet joint 5.

[0059] Pour concrete into the wet joint 5. During pouring, vibrate layer by layer from one end of the joint to the other end to ensure that the newly poured concrete is closely combined with the end of the flange 7 without cavities and honeycombs.

[0060] Stepwise temperature rise curing and temperature difference control: Preheating stage (0 - 3h): Start the first heating component 6 and the second heating component 4 simultaneously, preheat at a constant temperature of 20°C to avoid concrete cracking caused by sudden temperature rise.

[0061] Temperature rise stage (3 - 9h): Raise the temperature at a rate of 3°C / h. The temperature in the flange 7 area rises to 35°C, the temperature inside the box girder 1 rises to 27°C, and the temperature of the wet joint 5 is 8°C higher than that of the girder body for compensated shrinkage.

[0062] Constant temperature stage (9h to the end of curing): Maintain the temperature difference between the flange plate 7 and the internal core ≤ 12°C, and the temperature difference between the wet joint 5 and the flange plate 7 ≤ 5°C; when the main body temperature of the concrete < 5°C, the dynamic thermal insulation heating component 3 automatically starts to supplement heat and shuts down after the temperature reaches the standard.

[0063] The controller collects temperature data every 10 minutes. When the temperature difference exceeds the threshold, the heating power is adjusted. For example, when the temperature of the flange plate 7 exceeds 45°C, the first heating component 6 is cut off.

[0064] After 7 days of curing, the compressive strength of the joint is detected. When the strength reaches 80% of the design value, the thermal insulation layer, the electric heating film on the outer surface of the box girder 1 and the second heating component 4 inside are removed in sequence, and then the first heating component 6 is removed, and damage to the beam body should be avoided during the removal.

[0065] In this embodiment, waterproof treatment is carried out on the second heating component 4 pre-arranged in the box girder 1. The outlet end of the second heating component 4 adopts a three-layer structure of winding with waterproof tape, combined with silicone rubber sealing and metal bellows protection, and concrete can be poured only after passing the water pressure test.

[0066] Through the natural temperature gradient between the high-temperature area of the flange plate 7 and the medium-temperature area inside the beam body, the overall heating energy consumption is reduced by using the volume difference of the beam body. As Figure 4 shown, it is more than 30% energy-saving compared with traditional overall heating.

[0067] When the main body temperature of the box girder 1 is lower than 5°C, the dynamic thermal insulation heating component 3 starts to supplement heat with 50% power and stops after the temperature rises to 10°C, to avoid the temperature difference between the main body of the beam and the flange plate 7 exceeding 12°C.

[0068] In this embodiment, through the synergistic effect of prefabrication and embedding, zone heating, and intelligent temperature control, the temperature difference between the wet joint 5 and the box girder 1 can be controlled within a safe range in a low-temperature environment of -15°C to 5°C, ensuring the synchronous growth of concrete strength and improving the quality of bridge construction at low temperatures.

[0069] The above are only the preferred embodiments of the present invention and are not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coordinated temperature control system for wet joints and box girders, characterized in that, include: A first heating assembly is arranged in the flange plate of the box girder and the wet joint area of the adjacent box girder, and is used to heat the wet joint and the box girder flange plate adjacent to the wet joint; A second heating assembly is arranged on the inner wall of the box girder and is used to heat the box girder web, box girder top plate and box girder bottom plate; The temperature control component includes a controller and a temperature detection element. The temperature detection element is arranged on the box girder and the wet joint, and obtains the box girder temperature and the wet joint temperature respectively and sends them to the controller. The controller is used to adjust the operating parameters of the first heating component and the second heating component so that the temperature difference between the box girder and the wet joint is controlled within a set range.

2. The wet joint and box girder coordinated temperature control system according to claim 1, wherein It also includes a heat preservation and heating component, which is attached to the outer wall of the box beam web and the box beam bottom plate.

3. The wet joint and box girder coordinated temperature control system according to claim 2, characterized in that, The thermal insulation and heating assembly includes an electric heating film and a thermal insulation layer. The electric heating film is attached to the box beam, and the thermal insulation layer is arranged on a side of the electric heating film away from the box beam.

4. The wet joint and box girder coordinated temperature control system according to claim 1, wherein The second heating assembly includes an electric heating film attached to the inner wall of the box beam. The electric heating film is continuously distributed and covers the top, bottom and sides of the inner wall of the box beam.

5. The wet joint and box girder coordinated temperature control system according to claim 1, characterized in that, The first heating assembly is arranged on the upper surface and the bottom surface of the flange panel, and is also arranged on the top and the bottom of the wet joint area.

6. A low-temperature construction method for coordinating wet joints and box girders, which utilizes the wet joint and box girder coordinated temperature control system described in any one of claims 1-5, and is characterized in that, include: Arrange the second heating assembly in the box girder and hoist the box girder into place; Install a first heating assembly on the inner side of the box girder flange plate and the wet joint formwork, and arrange temperature detection elements in the box girder and wet joint areas; Carry out the grouting construction of wet joint concrete, and fully combine the newly poured concrete with the end of the box beam flange plate; During the concrete curing period, the first and second heating components are continuously operated to synchronously heat the box girder and wet joint area, and the temperature difference between the box girder and the wet joint is controlled within the set range, buffering the thermal stress gradient and synchronously raising the temperature of the junction area between new and old concrete; After the concrete curing is completed, the joint strength is tested. When the strength reaches the required level, the wet joints and the box girder coordinated temperature control system are removed.

7. The low-temperature construction method for coordinating the wet joint and the box girder according to claim 6, characterized in that During box girder prefabrication, after the box girder reinforcement cage is tied and before the box girder concrete is poured, the second heating system is fixed to the box girder reinforcement cage. The outlet end of the second heating system is waterproof and sealed, and the temperature control component is connected during the concrete curing period in the wet joint area.

8. The low-temperature construction method for the coordination of wet joints and box girders according to claim 6, characterized in that After hoisting the box girder, ensure that the adjacent box girders are correctly connected, clean the wet joint area and the wet joints where the box girders are connected, and ensure that the interface between the new and old concrete is clean.

9. The low-temperature construction method for the coordination of wet joints and box girders according to claim 6, characterized in that, During the concrete curing period, the first heating component and the second heating component adopt a step-by-step temperature increase, first preheating and then gradually heating.

10. The low-temperature construction method for the coordination of wet joints and box girders according to claim 6, characterized in that, During the concrete curing period, the temperatures of the box girder and the wet joint area are periodically collected, and the power of the first heating assembly and the second heating assembly are adjusted according to the temperatures.

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