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

Abstract

This invention provides a temperature control system for coordinated wet joints and box girders, as well as a low-temperature construction method, relating to the field of bridge engineering. Addressing the problem of excessive temperature differences and damage to the box girder caused by heating wet joints and adjacent flange areas under low-temperature conditions, this invention utilizes a first heating component to heat the wet joints and adjacent flanges, and a second heating component to heat the web, top plate, and bottom plate of the box girder body. This achieves synchronous heating and dynamic temperature regulation between the box girder and the wet joint, reducing the temperature difference between the wet joint, flanges, and the box girder body. The first and second heating components create a suitable temperature gradient between the wet joint and the box girder, reducing interface cracks and strength imbalances caused by temperature incoordination between the wet joint and the box girder, thus ensuring the integrity and durability of the bridge structure.

Description

Technical Field

[0001] This invention relates to the field of bridges, specifically to a temperature control system for coordinating wet joints and box girders, and a low-temperature construction method. Background Technology

[0002] Bridges often employ precast box girders combined with wet joints. During construction in winter or in frigid regions, the wet joints between the box girders are cast-in-place. If the curing temperature is not high enough, quality problems such as concrete frost heave, cracking, structural loosening, and surface efflorescence can occur. Existing technologies address these issues by providing construction and curing equipment and methods for wet joints. These methods involve placing insulation layers above and below the wet joint to heat and insulate the area, ensuring the cast-in-place wet joint is 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 where the wet joint meets the box girder flange is still difficult to regulate. Only the heating and insulation of the wet joint itself is considered, while the temperature of the precast beam connected to it is ignored. Because precast beams, such as box girders, are inherently cold in low-temperature environments, if the concrete poured at the wet joint is heated by the insulation layers above and below, while the end flanges of the box girder remain cold, a large temperature difference will form between the wet joint and the box girder flanges. This will cause uneven thermal stress at the joint, easily leading to early damage such as cracks, debonding, or interface peeling. Increasing the insulation layers above and below the wet joint to heat both the wet joint and the box girder flanges can make the temperature at the joint more uniform, thereby reducing uneven thermal stress and improving the curing quality of the wet joint. However, even after heating the flanges of the box girder, the main body of the box girder remains cold in low-temperature environments, and a large temperature difference still exists between the flanges and the main body. This can cause uncoordinated deformation of the precast box girder, inducing damage to the internal structure, affecting the structural stability of the box girder, and endangering bridge safety. Summary of the Invention

[0004] The purpose of this invention is to address the deficiencies of existing technologies by providing a temperature control system for coordinated wet joints and box girders, as well as a low-temperature construction method. This aims to solve the problem that heating and insulating only the wet joint body and its vicinity in low-temperature environments leads to a large temperature difference between the box girder flange and the main body of the box girder, causing uncoordinated deformation, resulting in internal damage to the already formed box girder, and exacerbating the risk of cracks in the box girder.

[0005] The primary objective of this invention is to provide a temperature control system for coordinated wet joints and box girders, employing the following approach:

[0006] include:

[0007] The first heating component 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 flange plate of the box girder adjacent to the wet joint.

[0008] The second heating component is arranged on the inner wall of the box girder and is used to heat the web, top plate and bottom plate of the box girder.

[0009] The temperature control component includes a controller and a temperature sensing element. The temperature sensing element is arranged at the box girder and the wet joint to acquire the box girder temperature and the wet joint temperature respectively and send them to the controller. The controller is used to adjust the operating parameters of the first heating component and the second heating component to control the temperature difference between the box girder and the wet joint within a set range.

[0010] Furthermore, it also includes thermal insulation and heating components, which are attached to the outer walls of the box girder web and the box girder bottom plate.

[0011] Furthermore, the heat insulation and heating component includes an electric heating film and an insulation layer. The electric heating film is attached to the box girder, and the insulation layer is arranged on the side of the electric heating film away from the box girder.

[0012] Furthermore, the second heating component includes an electric heating film applied to the inner wall of the box girder, the electric heating film being continuously distributed and covering the top, bottom and sides of the inner cavity of the box girder.

[0013] Furthermore, the first heating assembly is arranged on the upper and lower surfaces of the flange, and also on the top and bottom of the wet joint area.

[0014] A second objective of this invention is to provide a low-temperature construction method for coordinating wet joints and box girders, utilizing a temperature control system for coordinating wet joints and box girders as provided in the first objective, comprising:

[0015] The second heating component is placed inside the box girder, and the box girder is hoisted into place;

[0016] The first heating component is installed on the inner side of the box girder flange plate and the wet joint template, and temperature detection elements are arranged in the box girder and wet joint area.

[0017] Perform grouting of wet joint concrete to ensure full bonding between the newly poured concrete and the ends of the box girder flanges;

[0018] During concrete curing, the first and second heating components are continuously operated to raise the temperature of the box girder and wet joint area simultaneously, and the temperature difference between the box girder and wet joint is controlled within the set range to buffer the thermal stress gradient and raise the temperature of the junction area between the old and new concrete simultaneously.

[0019] After the concrete curing is completed, the joint strength is tested. Once the strength meets the requirements, the wet joint and the temperature control system coordinated with the box girder are removed.

[0020] Furthermore, during the prefabrication of the box girder, 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 waterproofed and sealed, and the temperature control component is connected during the curing of the concrete in the wet joint area.

[0021] Furthermore, after hoisting the box girders, ensure that the adjacent box girders are correctly positioned, clean the wet joint area and the location of the wet joint connecting the box girders, and ensure that the interface between the new and old concrete is clean.

[0022] Furthermore, during concrete curing, the first and second heating components employ a stepped heating method, first preheating and then gradually heating.

[0023] Furthermore, during concrete curing, the temperature of the box girder and wet joint area is periodically collected, and the power of the first and second heating components is adjusted according to the temperature.

[0024] Compared with the prior art, the advantages and positive effects of this invention are:

[0025] To address the problem of excessive temperature differences and damage to the box girder caused by heating the wet joints and adjacent flanges in low-temperature environments, a first heating component is configured to heat the wet joints and adjacent flanges, while a second heating component is configured to heat the web, top plate, and bottom plate of the box girder main body. This achieves synchronous heating and dynamic temperature regulation between the box girder and the wet joints, reducing the temperature difference between the wet joints, flanges, and the main body of the box girder. The first and second heating components can be used to create a suitable temperature gradient between the wet joints and the box girder, reducing interface cracks and strength imbalances caused by temperature inconsistencies between the wet joints and the box girder, and ensuring the integrity and durability of the bridge structure.

[0026] To address the issue of inconsistent deformation between the internal and external layers of a box girder due to heat transfer efficiency problems during heating, a second heating component is installed inside the box girder to heat it from the inside out. An insulation heating component is installed on the outer wall of the box girder to heat it from the outside in and also provides insulation. This ensures that the temperature of the large-volume box girder body is more uniform, reduces internal damage caused by temperature differences, and improves heating efficiency, making it suitable for low-temperature environments.

[0027] Not only does it heat and insulate the concrete in the wet joint area, it also simultaneously controls the temperature of the connected box girder flange plate and the main body of the box girder excluding the flange plate. Since the volume of the wet joint and flange plate is smaller than that of the main body of the box girder, when heating simultaneously, it can utilize the temperature gradient effect naturally formed by the volume difference between the wet joint and the box girder. The flange plate and the main body of the box girder are heated at the same time, with the flange plate area first rising to the first temperature that drives the joint hydration, and the main body of the box girder slowly rising to a second temperature lower than the first temperature to reduce energy consumption. It can also provide short-term heat replenishment by the heat insulation and heating components when the temperature difference is too large or the outer surface cools down, forming a gradient temperature control strategy. This avoids the time-consuming and energy-consuming problem of traditional overall heating, and also avoids the problem of cracks induced by surface heat and internal cold.

[0028] By utilizing multi-point temperature sensing elements to collect temperatures in the box girder and wet joint areas, and through closed-loop control, the temperature difference between the flange plate and the core of the box girder is consistently kept within a safe range, significantly reducing the risk of temperature cracks caused by localized temperature inconsistencies. This ensures the concrete strength in the wet joint area and improves the joint bonding quality and crack resistance. Attached Figure Description

[0029] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0030] Figure 1 This is a schematic diagram of a temperature control system for coordinating wet joints and box girders in one or more embodiments of the present invention.

[0031] Figure 2 This is a schematic diagram showing the distribution of wet joints and box girders in one or more embodiments of the present invention.

[0032] Figure 3 This is a flowchart of a low-temperature construction method for coordinating wet joints and box girders in one or more embodiments of the present invention.

[0033] Figure 4 This is a comparative schematic diagram of the coordinated temperature-controlled curing and natural curing of wet joints and box girders in one or more embodiments of the present invention.

[0034] 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 Implementation

[0035] Example 1

[0036] In a typical embodiment of the present invention, such as Figures 1-2 A temperature control system for coordinating wet joints and box girders is proposed.

[0037] When constructing the wet joint 5 of a bridge in a low-temperature environment, existing technologies only focus on heating and insulating the wet joint 5 itself and the adjacent flange plate 7, neglecting the temperature state of the main structure of the box girder 1. After the wet joint 5 is poured, if heating and insulation are only applied to its upper and lower parts, the temperature of the wet joint 5 will rise, while the flange plate 7 of the box girder 1 connected to it will remain at a low temperature due to the low-temperature environment. This temperature difference between the two will cause uneven thermal stress at the joint, leading to early damage such as cracks and debonding. If the heating range is expanded to the flange plate 7, the temperature of the flange plate 7 will rise, but the main body of the box girder 1 (such as the web plate 8, top plate 9, and bottom plate 10) will remain at a low temperature. This will create a new temperature difference between the flange plate 7 and the main body of the box girder 1, causing uncoordinated deformation of the precast box girder 1, inducing damage to the internal structure of the box girder 1, and endangering the safety of the bridge. Based on this, this embodiment provides a temperature control system for coordinated wet joints and box girders. It uses a first heating component 6 and a second heating component 4 for zoned heating. The first heating component 6 is located 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 their temperatures rise synchronously, reducing the temperature difference between them. The second heating component 4 is located on the inner wall of the box girder 1, heating the web plate 8, top plate 9, and bottom plate 10 of the box girder 1, making the temperature of the main body of the box girder 1 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, flange plate 7, and the main body of the box girder 1, a gradient distribution of temperature within the temperature difference damage range is formed in each part, avoiding uneven thermal stress caused by temperature differences and reducing early damage such as cracks, debonding, and interface peeling.

[0038] like Figures 1-4 As shown, the temperature control system for the wet joint and 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 flange plate 7 and wet joint 5 area, directly heating the wet joint 5 and its adjacent flange plate 7. The second heating component 4 is arranged in the inner wall of the box girder 1, heating the web plate 8, top plate 9, and bottom plate 10. The temperature of various parts of the box girder 1 and the wet joint 5, such as the temperature of the web plate 8, bottom plate 10, and top plate 9, is monitored in real time by temperature detection elements, 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 heating power and duration, according to the temperature data to ensure that the temperature difference between the box girder 1 as a whole and the wet joint 5 is controlled within the set range, forming a uniform temperature field.

[0039] To eliminate excessive temperature differences between the flange plate 7 and the main body of the box girder 1, ensuring the temperature difference remains within a set range, preventing inconsistent deformation of different parts of the precast box girder 1 due to excessive temperature differences, avoiding damage to the internal structure of the box girder 1, and improving the stability and safety of the bridge structure. To create a uniform curing temperature field in the wet joint 5 area, ensuring that the concrete of the wet joint 5 cures at a suitable temperature, improving the connection strength between the wet joint 5 and the box girder 1, and guaranteeing construction quality in low-temperature environments.

[0040] In this embodiment, the box girder 1 is a segmented prefabricated assembly structure, suitable for small and medium span bridges. As a prefabricated structure, it requires a wet joint 5 during construction. For ease of description of the temperature gradient distribution, in this embodiment, box girder 1 refers to the entire beam body. The main body of box girder 1 refers to all parts of box girder 1 except for the two side flanges 7, including the web 8, bottom plate 10, and top plate 9, which together form a box-shaped structure.

[0041] In this embodiment, to address the structural damage caused by temperature differences between the wet joint 5 and various parts of the box girder 1 during low-temperature construction, a strategy of zoned heating and intelligent temperature control is adopted. By synergistically heating the wet joint 5, flange plate 7, and the main body of the box girder 1, a uniform temperature field is constructed, eliminating thermal stress. Simultaneous temperature control of multiple areas avoids creating new temperature differences due to localized heating. Instead, the temperature of the wet joint 5, flange plate 7, and the main body of the box girder 1 is adjusted in a coordinated manner through the first heating component 6 and the second heating component 4. Temperature data is monitored in real time using a temperature control component, and the heating power is controlled in a closed-loop manner by a controller to ensure that the temperature difference remains within a safe range.

[0042] The first heating component 6 covers the upper and lower surfaces of the flange plate 7 and the pouring area of ​​the wet joint 5. The first heating component 6 can be a flexible electric heating film, heating cable, or infrared heating plate, which is attached to the template surface of the flange plate 7 and the wet joint 5 to ensure uniform heat conduction. An insulation layer (such as rock wool or polyurethane foam) can also be wrapped on the outside to reduce heat loss and improve heating efficiency.

[0043] The first heating component 6 directly heats the concrete of the wet joint 5, maintaining it at a suitable curing temperature and preventing frost heave cracking. The first heating component 6 simultaneously heats the flange plate 7, eliminating the temperature difference between the wet joint 5 and the flange plate 7 and reducing thermal stress at the joint.

[0044] The second heating component 4 is the main heating unit for the box girder 1, installed on the inner wall of the box girder 1, corresponding to the inner side of the web plate 8, top plate 9, and bottom plate 10. Heating the web plate 8, top plate 9, and bottom plate 10 causes the temperature of the main body of the box girder 1 to rise synchronously with the temperature of the flange plate 7 and wet joint 5, reducing the temperature difference between the flange plate 7 and the main body of the box girder 1. This prevents uncoordinated deformation of the box girder 1 caused by excessive temperature difference between the flange plate 7 and the main body of the box girder 1, ensuring the internal structural stability of the precast box girder 1.

[0045] The temperature control component is an intelligent monitoring and adjustment unit. It includes temperature detection elements arranged at the center of the wet joint 5, the surface of the flange 7, and the inner cavity of the box girder 1 to collect temperature data in real time. The controller receives the temperature signal, compares it with a preset temperature difference threshold, and dynamically adjusts the power of the first heating component 6 and the second heating component 4.

[0046] Temperature sensing elements transmit data to the controller in real time, forming dynamic temperature field data. When the temperature difference between the wet joint 5 and the flange 7 exceeds the threshold, the controller increases the power of the first heating component 6; when the temperature difference between the flange 7 and the main body of the box girder 1 exceeds the standard, the second heating component 4 is activated or increased. Alternatively, precise control of the heating power can be achieved through algorithms such as PID regulation to ensure that the temperature difference remains stable within a safe range.

[0047] like Figure 1 , Figure 2 As shown, the temperature control system for the wet joint and box girder also includes a thermal insulation and heating component 3. The thermal insulation and heating component 3 consists of an electric heating film and a thermal insulation layer, which are attached to the outer walls of the web plate 8 and the bottom plate 10. The electric heating film is in direct contact with the outer wall of the box girder 1, which can quickly transfer heat to the structure of the box girder 1; the thermal insulation layer is arranged on the outside of the electric heating film, which effectively prevents heat from escaping outward and plays a good role in thermal insulation.

[0048] The thermal insulation heating component 3 primarily heats and insulates the outer walls of the web plate 8 and the bottom plate 10, compensating for the inadequacy of heating from the inner cavity solely by the second heating component 4. The thermal insulation heating component 3 can be used to heat the web plate 8 and bottom plate 10 when the temperature difference between the flange plate 7 and the web plate 8 / bottom plate 10 is about to exceed a safety threshold. In low-temperature environments, the outer wall of the box girder 1 is in direct contact with the cold outside air, resulting in rapid heat loss. The thermal insulation heating component 3 effectively reduces heat loss, increases the overall temperature of the box girder 1, further reduces the temperature difference with the flange plate 7 and the wet joint 5, reduces thermal stress, and ensures the structural stability of the box girder 1. Simultaneously, its thermal insulation properties help maintain the temperature stability of the box girder 1, reducing the energy consumption of the temperature control system.

[0049] like Figure 1 As shown, the second heating component 4 can take the form of an electric heating film, an electric heating cable, an infrared heating plate, etc. In this embodiment, taking the use of an electric heating film as an example, a continuously distributed electric heating film is used to cover the top, bottom, and sides of the inner cavity of the box girder 1. Compared with a discontinuous arrangement, the continuous arrangement can ensure that the main structure of the box girder 1 is heated more evenly, avoiding the occurrence of local excessively high or low temperatures.

[0050] The continuous electric heating film allows heat to be transferred more efficiently to various parts of the web plate 8, top plate 9, and bottom plate 10. Combined with the effect of the heat insulation and heating component 3 on the outer wall of the box girder 1, it achieves all-round heating from the inside to the outside of the box girder 1, accelerates the heating rate of the main body of the box girder 1, and more accurately controls the temperature difference between the main body of the box girder 1 and the flange plate 7 and wet joint 5, thereby effectively reducing the uncoordinated deformation of the box girder 1 caused by temperature difference and improving the overall effect of the temperature control system.

[0051] 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, thus wrapping the wet joint 5 and its adjacent flange plate 7. This ensures that the wet joint 5 can be fully heated and insulated after pouring, ensuring that the concrete is cured at a suitable temperature and preventing problems such as frost heave and cracking.

[0052] The first heating component 6 works in conjunction with the insulation 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 insulation heating component 3 maintain the temperature of the main body of the box girder 1. The three work together to create a temperature field with a stepped temperature difference, effectively reducing the temperature difference between the components, reducing thermal stress and deformation, and improving the bridge construction quality and structural safety.

[0053] The first heating component 6, together with the heat insulation and heating component 3 and the second heating component 4, through different arrangements and functions, heat and insulate multiple parts of the box girder 1, including the interior, exterior, wet joints 5, and flange plates 7, forming a three-dimensional temperature control network. This allows for more precise control of the temperature of various parts of the box girder 1, keeping the temperature difference within a smaller range.

[0054] In this embodiment, the electric heating film, heating cable, and other components are installed in a designated position using fixing plates, fixing frames, and other fasteners. The output terminals of the second heating component 4 and the heating and insulation component can pass through pre-reserved pipes and connect to the controller. The controller can be connected to a power source to supply power to each component and regulate its operating status.

[0055] In this embodiment, when an electric heating cable is used 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 150mm, and after being inserted into a high-temperature resistant HDPE pipe, it is tied to the stirrup to avoid displacement during vibration.

[0056] When fixing the electric heating film, L-shaped fixing frames (made of aluminum alloy) are used for section 1 of the box girder, with the edges of the heating film pressed together at 0.5m intervals, and 3M VHB tape is used to enhance the fixing effect. For the wet joint 5 area, the heating film is embedded in the groove of the joint template, using a sandwich structure of template-heating film-insulation cotton to ensure a tight fit. Temperature sensors 2 can be used as temperature detection elements. For temperature sensors 2 placed on the surfaces of box girder 1 and wet joint 5, Φ5 stainless steel sleeves are inserted through drilled holes, filled with thermally conductive silicone, and then inserted to ensure coupling efficiency. For temperature sensors 2 embedded inside box girder 1 and wet joint 5, pre-embedding is carried out during concrete pouring.

[0057] Temperature sensors 2 are arranged in layers to capture the temperature difference between the inside and outside. The sensitivity of temperature sensors 2 is tested before pouring, and the measurement accuracy is controlled within ±1℃. It is understood that the temperature monitoring signal can also be connected to the control loop of the first heating component 6, the second heating component 4, and the heat preservation heating component 3, and a PID control algorithm can be preset; a wireless communication module interface is reserved to realize remote monitoring and data recording.

[0058] The insulation layer of the heat insulation and heating component 3 can be made of 40mm rigid polyurethane foam insulation board. Alternatively, flame-retardant and waterproof canvas can be covered on the outside of the insulation board and fixed with an aluminum alloy frame, locked at 0.5m intervals. Under normal operating conditions, it is in heat preservation mode, and automatically heats up to replenish the temperature only when the temperature of the web plate 8 or the bottom plate 10 is lower than the threshold.

[0059] In other alternative implementations, modular heating film units can be used for rapid assembly via magnetic attraction.

[0060] The comprehensive heating and insulation design effectively avoids thermal stress and inconsistent 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 internal structural damage, and extends the bridge's service life. In frigid environments, the insulation effect of the insulation and heating components 3 and the synergistic heating function of each component enable the system to better cope with harsh environments, ensuring the smooth progress of bridge construction and reducing the adverse effects of low temperatures on construction quality.

[0061] Example 2

[0062] In another typical embodiment of the present invention, such as Figures 1-4 A low-temperature construction method for coordinating wet joints and box girders is presented, utilizing a temperature control system for coordinating wet joints and box girders as described in Example 1.

[0063] A low-temperature construction method for coordinating wet joints with box girders includes:

[0064] Arrange the second heating component 4 inside the box girder 1, and hoist the box girder 1 into place;

[0065] The first heating component 6 is installed inside the template of the flange plate 7 and the wet joint 5, and temperature detection elements are arranged in the box girder 1 and the wet joint 5 area.

[0066] Perform grouting of the wet joint 5 concrete, ensuring that the newly poured concrete is fully bonded to the end of the flange plate 7;

[0067] During concrete curing, the first heating component 6 and the second heating component 4 are continuously operated to raise the temperature of the box girder 1 and the wet joint 5 area simultaneously, and the temperature difference between the box girder 1 and the wet joint 5 is controlled within the set range to buffer the thermal stress gradient and raise the temperature of the junction area between the new and old concrete simultaneously.

[0068] After the concrete curing is completed, the joint strength is tested. Once the strength meets the requirements, the wet joint and the temperature control system coordinated with the box girder are removed.

[0069] The low-temperature environment referred to in this embodiment refers to construction conditions where the daily average temperature is ≤5℃ or the minimum temperature is ≤0℃. Under this environment, the hydration reaction of concrete is significantly slowed down. If temperature control measures are not taken, problems such as frost heave and insufficient strength are likely to occur.

[0070] Specifically, such as Figures 1-4 As shown, a detailed explanation of the low-temperature construction method for coordinating wet joints with box girders is provided.

[0071] After the reinforcement cage of box girder 1 is tied and before concrete pouring, the second heating component 4 (electric heating film or cable) is fixed to the inside of the reinforcement cage at the designed spacing using nylon cable ties or metal clips. The cable outlet is treated with waterproof tape and sealant for double waterproofing to prevent water seepage during pouring. After pouring, a precast box girder 1 with the second heating component 4 is obtained.

[0072] Hoist the precast box girder 1 to the predetermined position, ensuring that the error of the butt joint between adjacent beams is ≤5mm and that the bottom of the beam is in close contact with the support. Remove debris, water and laitance from the wet joint area 5. If the flatness of the flange plate 7 end face exceeds the tolerance (>3mm), grind it with a grinder and blow it clean with a high-pressure air gun to ensure that the interface between the new and old concrete is clean and free of oil.

[0073] An electric heating film is laid on the upper and lower surfaces of the flange plate 7 and the inside of the template of the wet joint 5 as the first heating component 6. An L-shaped aluminum alloy fixing frame is used for pressing, and the edges are sealed with 3MVHB tape to ensure tight adhesion to the concrete surface.

[0074] An electric heating film is pasted on the outer surface of the web plate 8 and the bottom plate 10, and a 40mm thick polyurethane insulation board is covered on the outside as an insulation layer. It is fixed with an aluminum alloy pressure frame, and an insulation and heating component 3 is built on the outer wall of the box girder 1.

[0075] Temperature sensors 2 are installed in the center of the flange plate 7, the inner cavity of the box girder 1, and the wet joint 5. Fiber optic grating sensors are installed at one measuring point every 30cm along the length of the wet joint 5.

[0076] Pour concrete into the wet joint 5, and vibrate it in layers from one end of the joint to the other to ensure that the newly poured concrete is tightly bonded to the end of the flange plate 7 without voids or honeycomb.

[0077] Step-by-step heating and temperature difference control:

[0078] Preheating stage (0~3h): The first heating component 6 and the second heating component 4 are started simultaneously to preheat at a constant temperature of 20℃ to avoid cracking of concrete due to sudden temperature rise.

[0079] Heating stage (3~9h): The temperature is increased at a rate of 3℃ / h. The flange plate 7 area is raised to 35℃, the box girder 1 interior is raised to 27℃, and the wet joint 5 temperature is 8℃ higher than the beam body to compensate for shrinkage.

[0080] Constant temperature stage (9h to end of curing): Maintain the temperature difference between flange plate 7 and the internal core ≤12℃, and the temperature difference between wet joint 5 and flange plate 7 ≤5℃; when the temperature of the main concrete body is <5℃, the dynamic heat preservation heating component 3 will automatically start to replenish heat and will be turned off after the temperature reaches the standard.

[0081] The controller collects temperature data every 10 minutes. When the temperature difference exceeds the threshold, it adjusts the heating power. For example, when the temperature of the flange 7 exceeds 45°C, the first heating component 6 is cut off.

[0082] After 7 days of curing, the compressive strength of the joints is tested. When the strength reaches 80% of the design value, the 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. Then the first heating component 6 is removed. Avoid damaging the beam during removal.

[0083] In this embodiment, the second heating component 4, which is pre-arranged in the box girder 1, is waterproofed. The output end of the second heating component 4 adopts a three-layer structure of waterproof tape wrapping, silicone rubber sealing, and metal corrugated pipe protection. Concrete can only be poured after a water pressure test.

[0084] By utilizing the natural temperature gradient between the high-temperature zone of flange plate 7 and the medium-temperature zone inside the beam, the overall heating energy consumption is reduced by taking advantage of the volume difference of the beam. Figure 4 As shown, it saves more than 30% energy compared to traditional overall heating.

[0085] When the temperature of the main body of the box girder 1 is below 5℃, the dynamic heat preservation heating component 3 starts to supplement heat at 50% power and stops after the temperature rises to 10℃, so as to avoid the temperature difference between the main body of the girder and the flange plate 7 exceeding 12℃.

[0086] In this embodiment, through the synergistic effect of prefabrication and embedding, zoned 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℃ to 5℃, ensuring that the concrete strength increases synchronously and improving the quality of low temperature construction of the bridge.

[0087] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A temperature control system for coordinated wet joints and box girders, characterized in that, include: The first heating component 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 flange plate of the box girder adjacent to the wet joint. The first heating assembly is arranged on the upper and lower surfaces of the flange plate, and also on the top and bottom of the wet joint area; The second heating component is arranged on the inner wall of the box girder and is used to heat the web, top plate and bottom plate of the box girder. The second heating component includes an electric heating film that is applied to the inner wall of the box girder, and the electric heating film is continuously distributed and covers the top, bottom and sides of the inner cavity of the box girder; The temperature control component includes a controller and a temperature detection element. The temperature detection element is arranged at the box girder and the wet joint to acquire the box girder temperature and the wet joint temperature respectively and send them to the controller. The controller is used to adjust the operating parameters of the first heating component and the second heating component to control the temperature difference between the box girder and the wet joint within the set range, buffer the thermal stress gradient, and make the temperature of the junction area of ​​new and old concrete rise synchronously. It also includes thermal insulation and heating components, which are attached to the outer walls of the box girder web and the box girder bottom plate; During concrete curing, the first and second heating components are continuously operated. The first and second heating components adopt a stepped heating method, first preheating and then gradually heating, so that the box girder and wet joint area are heated synchronously, reducing the temperature difference between the wet joint, flange plate and box girder body, and controlling the temperature difference between the box girder and wet joint within the set range. During the prefabrication of the box girder, 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 waterproofed and sealed, and the temperature control component is connected during the curing of the concrete in the wet joint area.

2. The temperature control system for coordinated wet joints and box girders as described in claim 1, characterized in that, The heat insulation and heating assembly includes an electric heating film and an insulation layer. The electric heating film is attached to the box girder, and the insulation layer is arranged on the side of the electric heating film away from the box girder.

3. A low-temperature construction method for coordinating wet joints and box girders, utilizing the temperature control system for coordinating wet joints and box girders as described in any one of claims 1-2, characterized in that, include: The second heating component is placed inside the box girder, and the box girder is hoisted into place; The first heating component is installed on the inner side of the box girder flange plate and the wet joint template, and temperature detection elements are arranged in the box girder and wet joint area. Perform grouting of wet joint concrete to ensure full bonding between the newly poured concrete and the ends of the box girder flanges; During concrete curing, the first and second heating components are continuously operated to simultaneously raise the temperature of the box girder and the wet joint area, and to control the temperature difference between the box girder and the wet joint within the set range. After the concrete curing is completed, the joint strength is tested. Once the strength meets the requirements, the wet joint and the temperature control system coordinated with the box girder are removed.

4. The low-temperature construction method for coordinating wet joints and box girders as described in claim 3, characterized in that, After hoisting the box girders, ensure that the adjacent box girders are correctly connected, clean the wet joint area and the location of the wet joint connecting the box girders, and ensure that the interface between the new and old concrete is clean.

5. The low-temperature construction method for coordinating wet joints and box girders as described in claim 3, characterized in that, During concrete curing, the first and second heating components use a stepped heating method, first preheating and then gradually heating.

6. The low-temperature construction method for coordinating wet joints and box girders as described in claim 3, characterized in that, During concrete curing, the temperature of the box girder and wet joint area is periodically collected, and the power of the first and second heating components is adjusted according to the temperature.

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