A pylon concrete anti-cracking beam structure and a construction method thereof

Abstract

The application provides a bridge tower concrete anti-cracking beam structure and a construction method thereof, and relates to the field of bridge engineering.The bridge tower concrete anti-cracking beam structure comprises a bridge tower concrete beam body and a post-pouring belt.A post-pouring belt is arranged at the middle position of the bridge tower concrete beam body, and the post-pouring belt is constructed after the shrinkage rate of the concrete on both sides of the bridge tower concrete beam body reaches a preset proportion of the corresponding final shrinkage rate;in the internal steel bar structure of the bridge tower concrete beam body, the outer longitudinal steel bars are wrapped with a steel wire mesh; and the bridge tower concrete beam body is supported by a steel structure type steel support which does not need to be removed, and the steel structure type steel support comprises a beam bottom support and a beam internal support.The concrete anti-cracking beam structure is integrated by material innovation, construction mode optimization and surface protection measures, thereby improving the anti-cracking effect and stress performance, and significantly prolonging the service life of the structure.

Description

Technical Field

[0001] This invention relates to the field of bridge engineering technology, specifically to a concrete crack-resistant crossbeam structure for bridge towers and its construction method. Background Technology

[0002] As a core force-transmitting component of long-span bridges such as cable-stayed bridges and suspension bridges, the structural performance of bridge tower crossbeams directly determines the overall stability and durability of the bridge. Under complex stress environments and temperature changes, the crack resistance of the tower crossbeams is directly related to whether the structure will suffer cascading damage due to cracking. Only by ensuring excellent crack resistance can fatigue failure and corrosion processes be effectively delayed, ensuring the safety and reliability of the bridge throughout its entire life cycle.

[0003] Existing bridge tower crossbeams (such as the bridge tower crossbeams constructed using a construction method disclosed in CN104109999B) typically have the following specific problems: The beams are supported by removable temporary supports. When the supports are removed, the beams are prone to large deflection deformation under their own weight and subsequent loads, causing the tensile stress in the cross section to exceed the tensile strength of the concrete, thereby inducing new bending cracks and further weakening the crack resistance of the structure. Without a post-pouring strip, the shrinkage stress of the concrete during the hardening process cannot be effectively released, which can easily lead to through cracks in stress concentration areas such as the middle of the beam, seriously affecting the safety of the structural force transmission path. Summary of the Invention

[0004] The present invention provides a concrete crack-resistant crossbeam structure for bridge towers to solve at least one of the technical problems mentioned in the background art.

[0005] To solve the above-mentioned technical problems, the present invention discloses a concrete crack-resistant crossbeam structure for bridge towers, comprising: This includes the main body of the bridge tower concrete beam and the post-pouring strip. A post-pouring strip is left in the middle of the main body of the bridge tower concrete beam. The post-pouring strip will be constructed after the shrinkage rate of the concrete on both sides of the main body of the bridge tower concrete beam reaches the preset ratio of the corresponding final shrinkage rate. In the internal steel reinforcement structure of the main concrete beam of the bridge tower, the outer longitudinal steel bars are wrapped with wire mesh. The main body of the concrete beam of the bridge tower is supported by a steel structure frame that does not need to be dismantled. The steel structure frame includes bottom support and internal support of the beam.

[0006] Preferably, the main cross section of the concrete beam of the bridge tower adopts a thin-walled box section or a thin-walled multi-cell box section.

[0007] Preferably, the main body of the bridge tower concrete beam is made of low-heat micro-expansion cement, and admixtures are used to replace part of the cement. The admixtures include fly ash and silica fume, and an expansion agent is added to the concrete.

[0008] Preferably, fly ash accounts for 20% of the total mass of the cementitious materials in the concrete, silica fume accounts for 10% of the total mass of the cementitious materials in the concrete, and the expanding agent includes expanded calcium sulfate or aluminum powder.

[0009] Preferably, the post-cast strip is made of ultra-high performance concrete.

[0010] Preferably, the surface of the concrete beam of the bridge tower is coated with a waterproof membrane; and a shock-absorbing damper is installed inside the concrete beam of the bridge tower.

[0011] Preferably, the steel structure support frame includes: Bottom support of the crossbeam: including support structure one, which is supported at the bottom of the concrete crossbeam body of the bridge tower. The support structure one is connected to a pull-out resistant but not shear resistant connector, and a part of the support structure is embedded in the concrete crossbeam body of the bridge tower. Internal support of the crossbeam: including support structure two, which is supported inside the main body of the concrete crossbeam of the bridge tower, and the support structure two is connected to a pull-out resistant but not shear resistant connector.

[0012] Preferably, step 1: erect a steel structure support frame, which includes bottom support for the crossbeam and internal support for the crossbeam, serving as a permanent support structure for the main body of the concrete crossbeam of the bridge tower; Step 2: The internal steel reinforcement structure of the main concrete beam of the outer bridge tower is supported inside the crossbeam of the steel structure bracket, and the outer longitudinal steel reinforcement is covered with wire mesh. At the same time, a shock absorber is installed inside the crossbeam structure. Step 3: Pour concrete for both sides of the main concrete beam of the bridge tower, and leave a post-pouring strip in the middle between the two sides; Step 4: After the concrete has initially set, perform early curing by steam curing or wet curtain curing. Step 5: Apply a waterproof membrane to the surface of the beam; Step 6: After the shrinkage rate of the concrete on both sides of the main body of the bridge tower concrete beam reaches the preset ratio of the corresponding final shrinkage rate, the post-pouring strip is constructed to form the bridge tower concrete crack-resistant beam structure.

[0013] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 1. The structure of this invention has significant advantages in crack resistance. By using micro-expansion concrete, a small amount of expansion occurs in the early stage of concrete hardening, offsetting the shrinkage effect and effectively preventing the formation of shrinkage cracks. In addition, the central post-cast strip uses UHPC material, which has excellent toughness and low shrinkage rate, further reducing the risk of crack formation, and is especially suitable for critical stress areas, ensuring the overall crack resistance of the beam; 2. Regarding the structural stress of this invention, the integral molding construction avoids the age differences in different areas caused by traditional grid casting, ensuring the uniformity of the structure and effectively reducing stress concentration. Furthermore, the use of a temporary support system during the construction phase ensures that the beams can stably bear loads before the post-cast strip is completed, guaranteeing the safety of the structure during construction and operation. 3. The structure of this invention also has significant advantages in operation and maintenance. The durability and low permeability of the UHPC post-cast strip material reduce the risk of later crack propagation and water infiltration, greatly reducing the maintenance frequency. The application of the surface waterproof membrane further extends the service life of the beams, resists the erosion of concrete by moisture, temperature and acid / alkali environments, thereby reducing the damage caused by freeze-thaw cycles and effectively reducing maintenance costs; 4. In summary, this structural form is particularly suitable for the bridge tower crossbeam structure of long-span bridges. This bridge tower concrete crack-resistant crossbeam structure, through the integration of material innovation, construction method optimization and surface protection measures, not only improves crack resistance and stress performance, but also significantly extends the service life of the structure and reduces maintenance requirements. It has significant economy and durability, and is an innovative structural design with high safety and high performance. Attached Figure Description

[0015] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used in conjunction with embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings: Figure 1 This is a schematic diagram of the overall structure of the present invention; Figure 2 The cross section of the beam structure of the present invention Figure 1 ; Figure 3 The cross section of the beam structure of the present invention Figure 2 ; Figure 4 This is a schematic diagram of the wire mesh and outer diaphragm of the present invention; Figure 5 This is a schematic diagram of the structural support of the present invention. Figure 1 ; Figure 6 This is a schematic diagram of the structural support of the present invention. Figure 2 .

[0016] In the diagram: 1. Main body of the bridge tower concrete beam; 11. Concrete; 12. Longitudinal reinforcement; 13. Stirrups; 14. Wire mesh; 15. Epoxy resin coating; 2. Post-cast strip; 3. Bottom support of the beam; 4. Internal support of the beam; 5. Pull-out but not shear-resistant connector; 6. Support structure one; 7. Support structure two. Detailed Implementation

[0017] The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. It should be understood that the preferred embodiments described herein are for illustration and explanation only and are not intended to limit the present invention.

[0018] Furthermore, in this invention, the use of terms such as "first" and "second" is for descriptive purposes only and does not specifically refer to any order or sequence, nor is it intended to limit the invention. They are merely used to distinguish components or operations described using the same technical terms and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of those features. Additionally, the technical solutions and features of the various embodiments can be combined with each other, but this must be based on the ability of those skilled in the art to implement them. If a combination of technical solutions is contradictory or impossible to implement, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection claimed by this invention.

[0019] The present invention provides the following embodiments: Example 1: This embodiment of the invention provides a concrete crack-resistant crossbeam structure for bridge towers, such as... Figures 1-6 As shown, it includes: The structure includes the main body 1 of the concrete crossbeam of the bridge tower and the post-pouring strip 2. A post-pouring strip 2 is left in the middle of the main body 1 of the concrete crossbeam of the bridge tower. The post-pouring strip 2 is constructed after the shrinkage rate of the concrete on both sides of the main body 1 of the concrete crossbeam of the bridge tower reaches the preset ratio of the corresponding final shrinkage rate (greater than or equal to 90%). This can reduce the risk of cracks caused by shrinkage differences. In the internal steel reinforcement structure of the main concrete beam 1 of the bridge tower, the outer longitudinal steel bars 12 are wrapped with steel wire mesh 14. After pouring, the uneven constraint of the internal steel reinforcement structure on the shrinkage of the concrete can be reduced, and the shrinkage cracking of the external concrete can be controlled. The main body 1 of the bridge tower's concrete crossbeam is supported by a steel structure frame that does not require dismantling. This steel structure frame includes a bottom support 3 and an internal support 4. Neither the bottom support 3 nor the internal support 4 needs to be removed after construction; they can be considered part of the permanent structure. The crossbeam support is connected to the concrete section using pull-out but not shear-resistant studs. Among them, such as Figure 2 , Figure 3As shown, the main section of the concrete crossbeam of the bridge tower adopts a thin-walled box section or a thin-walled multi-cell box section, avoiding the use of a solid web section.

[0020] The main body 1 of the concrete beam of the bridge tower uses low-heat micro-expansion cement and uses admixtures to replace part of the cement to reduce the heat of hydration. The admixtures include fly ash and silica fume, and an expansion agent is added to the concrete 11 to achieve a micro-expansion effect, compensate for early shrinkage, and reduce the risk of crack formation.

[0021] In this concrete 11, fly ash accounts for 20% of the total mass of the cementitious materials, silica fume accounts for 10% of the total mass of the cementitious materials, and the expanding agent includes expanded calcium sulfate or aluminum powder.

[0022] The post-cast strip 2 is made of ultra-high performance concrete (UHPC), which has high strength, high toughness and good shrinkage control, thus effectively preventing later cracks.

[0023] The surface of the concrete beam body 1 of the bridge tower is coated with a waterproof membrane to prevent moisture loss. Specifically, an epoxy resin coating 15 is used to avoid significant drying shrinkage of the concrete surface under the action of air convection; a shock-absorbing damper is installed inside the concrete beam body 1 of the bridge tower to effectively alleviate the stress caused by earthquakes and other vibrations, and improve the overall crack resistance. Figure 4 As shown, the steel reinforcement structure of the main concrete beam 1 of the bridge tower includes longitudinal steel bars 12 and stirrups 13. The longitudinal steel bars 12 are arranged along the length of the beam and are the main tensile reinforcement bars. The stirrups 13 are set perpendicular to the longitudinal steel bars 12, which play a role in restraining and positioning the longitudinal steel bars 12, and at the same time enhance the shear resistance of the concrete 1. The longitudinal steel bars 12 and the stirrups 13 together form a steel reinforcement skeleton, and the longitudinal steel bars 12 are covered with wire mesh. The wire mesh is embedded in the concrete 11 along with the steel reinforcement skeleton, and works together with the concrete to bear the structural load. Among them, the steel structure steel support includes: The bottom support of the crossbeam 3 includes a support structure 6, which is supported at the bottom of the concrete crossbeam body 1 of the bridge tower. The support structure 6 is connected to a pull-out but not shear-resistant connector 5, and the support structure 6 is partially embedded in the concrete crossbeam body 1 of the bridge tower. Internal support 4 of the crossbeam: includes a second support structure 7, which is supported inside the main body 1 of the concrete crossbeam of the bridge tower. The second support structure 7 is connected to a pull-out but not shear-resistant connector 5.

[0024] This invention also discloses a construction method for a bridge tower concrete crack-resistant beam structure, comprising: Step 1: Erect a steel structure support frame, which includes a bottom support 3 for the crossbeam and an internal support 4 for the crossbeam, serving as a permanent support structure for the main body 1 of the concrete crossbeam of the bridge tower. Step 2: Construct the internal steel reinforcement structure of the main body 1 of the concrete beam of the bridge tower inside the crossbeam of the steel structure support 4, and wrap the outer longitudinal steel bars 12 with wire mesh 14, and install shock absorbers inside the beam structure. Step 3: Pour concrete for both sides of the main body 1 of the bridge tower concrete beam, and reserve a post-pouring strip 2 in the middle between the two sides; Step 4: After the concrete has initially set, perform early curing by steam curing or wet curtain curing. Step 5: Apply a waterproof membrane to the surface of the beam; Step 6: After the shrinkage rate of the concrete on both sides of the main concrete beam 1 of the bridge tower reaches the preset ratio of the corresponding final shrinkage rate, the post-pouring strip 2 is constructed to form the crack-resistant concrete beam structure of the bridge tower.

[0025] During the pouring process, a one-time integral pouring method is adopted to avoid age differences between different areas that may be caused by grid pouring, reduce the accumulation of internal stress, and prevent the formation of cracks.

[0026] After the initial setting of concrete, early curing is carried out by means of steam curing or wet curtain moisturizing to control moisture evaporation and reduce the formation of shrinkage cracks. The beneficial effects of the above technical solution are as follows: 1. The structure of this invention has significant advantages in crack resistance. By using micro-expansion concrete, a small amount of expansion occurs in the early stage of concrete hardening, offsetting the shrinkage effect and effectively preventing the formation of shrinkage cracks. In addition, the central post-cast strip uses UHPC material, which has excellent toughness and low shrinkage rate, further reducing the risk of crack formation, and is especially suitable for critical stress areas, ensuring the overall crack resistance of the beam; 2. Regarding the structural stress of this invention, the integral molding construction avoids the age differences in different areas caused by traditional grid casting, ensuring the uniformity of the structure and effectively reducing stress concentration. Furthermore, the use of a temporary support system during the construction phase ensures that the beams can stably bear loads before the post-cast strip is completed, guaranteeing the safety of the structure during construction and operation. 3. The structure of this invention also has significant advantages in operation and maintenance. The durability and low permeability of the UHPC post-cast strip material reduce the risk of later crack propagation and water infiltration, greatly reducing the maintenance frequency. The application of the surface waterproof membrane further extends the service life of the beams, resists the erosion of concrete by moisture, temperature and acid / alkali environments, thereby reducing the damage caused by freeze-thaw cycles and effectively reducing maintenance costs; 4. In summary, this structural form is particularly suitable for the bridge tower crossbeam structure of long-span bridges. This bridge tower concrete crack-resistant crossbeam structure, through the integration of material innovation, construction method optimization and surface protection measures, not only improves crack resistance and stress performance, but also significantly extends the service life of the structure and reduces maintenance requirements. It has significant economy and durability, and is an innovative structural design with high safety and high performance.

[0027] Example 2, based on Example 1, involves early curing of concrete 11 after initial setting using steam curing in a sealed curing shed, including: Step 41: Obtain the water-cement ratio determined before pouring the current concrete 11, and obtain the standard curing parameters for each curing stage of the current concrete 11 based on experimental determination. Step 42: Perform the first curing stage based on the standard steam supply parameters for the first curing stage of the current concrete 11; during the curing process, periodically monitor the ambient temperature and humidity in the sealed curing shed and the temperature and humidity of the curing surface of the concrete 11. Step 43: When the ambient humidity reaches the preset value, determine the temperature gradient coefficient and humidity gradient coefficient based on the test results, and determine the crack resistance characteristic coefficient by combining the temperature gradient coefficient, humidity gradient coefficient and water-cement ratio determined before the current concrete 11 is poured. Step 44: When the crack resistance characteristic coefficient does not meet the preset tensile characteristic coefficient requirement, determine multiple sets of temperature gradient change rates and multiple sets of humidity gradient change rates based on the latest historical test results (which can be taken as 10 min to 20 min), and determine the temperature gradient change rate change coefficient and humidity gradient change rate change coefficient. The rate ratio of the temperature gradient change rate and the humidity gradient change rate for each group is determined. When the rate ratio does not meet the corresponding rate ratio requirements (0.8 to 1.2 for heating curing; 0.7 to 1.3 for constant temperature curing; 0.9 to 1.1 for cooling curing), the curing parameters are adjusted based on the rate ratio. Step 45: Continue to perform maintenance based on the adjusted maintenance parameters, and periodically determine the crack resistance characteristic coefficient based on the test. If the crack resistance characteristic coefficient does not meet the preset tensile characteristic coefficient requirements, repeat step 44 until the maintenance is completed.

[0028] Specifically: When the rate ratio R < 0.7 (the rate of change of the humidity gradient is too fast): the rate of moisture loss from the concrete surface is much faster than the temperature change, which can easily lead to drying shrinkage cracking.

[0029] Adjustment measures: Increase the frequency and amount of steam supply to directly increase the humidity inside the curing shed and inhibit moisture loss.

[0030] Adjusted steam supply frequency = original steam supply frequency × (1 + humidity gradient change rate coefficient × rate ratio × frequency adjustment coefficient). Adjusted gas supply = original gas supply × (1 + humidity gradient change rate coefficient × rate ratio × gas supply adjustment coefficient). When the rate ratio R > 1.3 (temperature gradient change rate is too fast): the temperature difference between the inside and outside of the concrete expands rapidly, thermal stress accumulates more quickly, and temperature cracking is easily triggered. Adjustment measures: Lowering the steam supply temperature or slowing down the heating rate can reduce the temperature gradient within the concrete surface.

[0031] If the temperature is in the cooling phase, the cooling rate needs to be further reduced to avoid sudden temperature changes.

[0032] Adjusted steam supply temperature = Original steam supply temperature × (1 - Temperature gradient change rate coefficient × Rate ratio × Frequency adjustment coefficient) When the rate ratio returns to 0.7 ≤ R ≤ 1.3 (restoring equilibrium): Key action: Gradually adjust the maintenance parameters back to the standard values ​​for this maintenance stage to maintain a dynamic balance of temperature and humidity.

[0033] The frequency adjustment coefficient, gas supply adjustment coefficient, and steam supply temperature adjustment coefficient are fixed empirical coefficients determined through indoor mix proportion tests, on-site curing simulation tests, and engineering experience corrections, taking into account the characteristics of the large-volume concrete of the bridge tower beams and the complex high-altitude environment. Among them, the frequency adjustment coefficient and gas supply adjustment coefficient are generally taken as 0.15 to 0.25, and the steam supply temperature adjustment coefficient is generally taken as 0.08 to 0.15.

[0034] (1) The water-cement ratio determined before pouring concrete 11: refers to the ratio of the total mass of water to the total mass of cementitious materials (cement, fly ash, mineral powder, etc.) during concrete mixing. This is the core mix proportion parameter that determines the early strength development, hydration heat release rate, and shrinkage cracking risk of concrete. The higher the water-cement ratio, the more pores there are inside the concrete, the greater the early shrinkage, and the higher the risk of cracking. Bridge tower beams are large-volume, high-stress components, and even small changes in the water-cement ratio will significantly affect their crack resistance. Locking in this value in advance is the basis for subsequent precise curing.

[0035] Standard curing parameters for each curing stage: These refer to a set of benchmark / standard parameters (such as standard temperature gradient and standard humidity gradient for each curing stage) established through indoor or field tests for specific working conditions of this batch of concrete and bridge tower beams, for different curing stages (such as heating period, constant temperature period, cooling period). The water-cement ratio corresponding to the above tests is the standard water-cement ratio.

[0036] Specifically, it includes: The range of concrete heating rate, cooling rate, ambient temperature, and ambient humidity at each curing stage.

[0037] Steam supply parameters: steam pressure (range), steam supply frequency, zoned steam supply volume (range).

[0038] Duration parameter: the shortest / longest duration of each maintenance step.

[0039] (2) The “preset value” in step 43 is the environmental humidity trigger threshold (usually 85% to 95% RH) determined by experiments or engineering experience before the curing plan is started, taking into account the characteristics of the large volume concrete of the bridge tower beam. It is a key node for dividing the curing stage. Only when the environmental humidity in the sealed curing shed reaches this value can it be said that the curing environment has entered a stable and controllable state. At this time, the temperature and humidity gradient coefficient and crack resistance characteristic coefficient calculated based on the detection data can truly reflect the cracking risk of the concrete, and then start the subsequent refined crack resistance control to avoid misjudgment caused by humidity fluctuations caused by environmental factors such as high-altitude wind fields.

[0040] Temperature gradient coefficient = (ambient temperature in the sealed curing shed - temperature of the curing surface of concrete 11) ÷ standard temperature gradient of the corresponding curing stage; Humidity gradient coefficient = (ambient humidity in the sealed curing shed - humidity of the curing surface of concrete 11) ÷ standard humidity gradient of the corresponding curing stage; The above is based on the average detection values ​​of each parameter determined by synchronous detection or within the same shorter detection cycle; Crack resistance characteristic coefficient = temperature gradient coefficient × humidity gradient coefficient × ; Crack resistance characteristic coefficient: This is a direct quantitative characterization of the risk of early cracking in concrete under the combined effects of temperature and humidity gradient and the water-cement ratio characteristics of concrete. It normalizes the correlation between environmental temperature and humidity imbalance and the crack resistance potential of the material; the larger the coefficient value, the higher the risk of early cracking.

[0041] Temperature gradients are the direct cause of temperature stress in concrete. The greater the temperature difference between the curing shed environment and the concrete surface, the higher the surface temperature stress and the greater the risk of cracking.

[0042] Humidity gradients can cause moisture migration from the concrete surface, leading to surface shrinkage. The greater the humidity difference between the ambient humidity and the concrete surface humidity, the more significant the surface shrinkage and the higher the risk of cracking.

[0043] The water-cement ratio is a key material parameter that determines the early crack resistance potential of concrete. The higher the water-cement ratio, the worse the water retention of the paste, the greater the drying shrinkage, the lower the early tensile strength, and the weaker the crack resistance.

[0044] The crack resistance characteristic coefficient requirement here is a preset safety threshold for large-volume, high-stress concrete components such as bridge tower beams, after adjustments based on indoor tests and on-site conditions. It is the core basis for determining the risk of early cracking in concrete. The values ​​are: 0.35–0.38 for heating curing; 0.38–0.42 for constant temperature curing; and 0.37–0.4 for cooling curing. Rate of change of temperature gradient = (current temperature gradient - previous temperature gradient) / time interval; Humidity gradient change rate = (current humidity gradient - previous humidity gradient) / time interval; Rate ratio = Rate of change of temperature gradient ÷ Rate of change of humidity gradient; When the rate ratio is greater than 1, the dynamic response of thermal migration inside the slurry is faster than that of wet migration. When the temperature field fluctuates rapidly, moisture migration cannot keep up in time. When the rate ratio is less than 1, the dynamic response of wet migration inside the slurry is much faster than that of thermal migration. When the humidity field fluctuates rapidly, heat conduction cannot be adjusted in time. Temperature gradient is the driving force for heat migration inside the slurry: the larger the temperature gradient, the faster the heat conduction / heat convection rate, and the more uneven the temperature field distribution inside the slurry, which in turn affects the hydration reaction rate (hydration is an exothermic reaction, and heat migration will reverse the temperature gradient, forming a coupling). Humidity gradient: It is the driving force for the migration of water inside the slurry. The larger the humidity gradient, the faster the capillary water absorption / water vapor diffusion rate, and the more uneven the distribution of the humidity field inside the slurry, which directly affects the material transport of the hydration reaction (hydration requires free water, and water migration determines the degree of hydration in different areas of the slurry). Temperature gradient rate of change coefficient = (current temperature gradient rate of change - previous temperature gradient rate of change) ÷ unit temperature gradient rate of change. Humidity gradient change rate coefficient = (current humidity gradient change rate - previous humidity gradient change rate) ÷ unit humidity gradient change rate. After each regulation / adjustment, the "regulation response delay time" (the time from triggering to the return of the anti-cracking characteristic coefficient to the safe range) and the "regulation redundancy" (the deviation between the actual adjustment amount and the theoretical optimal adjustment amount) are calculated. Based on these two indicators, the values ​​of the adjustment coefficients (such as the frequency adjustment coefficient and the gas supply adjustment coefficient) are dynamically corrected to form a closed-loop iteration.

[0045] This invention can also determine regional risks by combining the crack resistance characteristic coefficients and rate ratio distributions of each region, and construct a zone-specific precise control mechanism based on the spatial distribution characteristics of the risks. Specifically, by comparing the crack resistance characteristic coefficients and rate ratios of different regions such as the web and flanges, high-risk areas of local stress concentration can be identified, thereby allocating differentiated steam supply parameters and insulation strategies to each region.

[0046] The beneficial effects of the above technical solution are as follows: By coupling the calculation of temperature and humidity gradient coefficient, water-cement ratio and crack resistance characteristic coefficient, a quantitative assessment of the risk of early cracking in concrete is achieved, rather than relying on experience judgment, thus avoiding the problems of over-curing or under-curing in traditional curing.

[0047] When the crack resistance characteristic coefficient does not meet the requirements, the system triggers regulation and combines the change coefficient to predict the dynamic trend of temperature and humidity gradient, thereby achieving proactive prevention and control of cracking risk, significantly reducing the probability of early cracks in bridge tower beams, and thus improving the long-term durability of the structure.

[0048] Based on the graded adjustment logic of rate ratio and change coefficient, maintenance parameters are adjusted only when the risk is clear, reducing unnecessary consumption of resources such as steam supply and insulation, and realizing refined resource allocation.

[0049] Precise dynamic control allows for more stable concrete strength development, which can appropriately shorten the curing cycle and accelerate the overall progress of bridge tower construction while meeting crack resistance requirements.

[0050] Quantitative control formulas and clear threshold standards reduce the reliance on experience-based judgment by on-site personnel, making maintenance operations more standardized and reducing the probability of human error.

[0051] The control mechanism, designed to address the characteristics of strong winds and significant temperature differences at high altitudes, enhances the maintenance system's adaptability to complex environments and ensures the quality and safety of maintenance during high-altitude construction.

[0052] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A concrete crack-resistant crossbeam structure for bridge towers, characterized in that: The bridge tower concrete beam body (1) and the post-cast strip (2) are included. A post-cast strip (2) is left in the middle of the bridge tower concrete beam body (1). The post-cast strip (2) is constructed after the shrinkage rate of the concrete on both sides of the bridge tower concrete beam body (1) reaches the preset ratio of the corresponding final shrinkage rate. In the internal steel reinforcement structure of the main concrete beam of the bridge tower (1), the outer longitudinal steel bars (12) are covered with steel wire mesh (14); The main body of the concrete crossbeam of the bridge tower (1) is supported by a steel structure frame that does not need to be dismantled. The steel structure frame includes the bottom support (3) of the crossbeam and the internal support (4) of the crossbeam.

2. The anti-crack concrete crossbeam structure for bridge towers according to claim 1, characterized in that: The main body of the concrete beam of the bridge tower (1) adopts a thin-walled box section or a thin-walled multi-chamber box section.

3. The bridge tower concrete crack-resistant crossbeam structure according to claim 1, characterized in that: The main body (1) of the concrete beam of the bridge tower is made of low-heat micro-expansion cement, and admixtures are used to replace part of the cement. The admixtures include fly ash and silica fume, and an expansion agent is added to the concrete (11).

4. The bridge tower concrete crack-resistant beam structure according to claim 3, characterized in that: Fly ash accounts for 20% of the total mass of cementitious materials in concrete (11), silica fume accounts for 10% of the total mass of cementitious materials in concrete (11), and the expanding agent includes expanded calcium sulfate or aluminum powder.

5. The anti-cracking concrete crossbeam structure for bridge towers according to claim 1, characterized in that: The post-cast strip (2) is made of ultra-high performance concrete.

6. The anti-cracking concrete crossbeam structure for bridge towers according to claim 1, characterized in that: The surface of the concrete beam body (1) of the bridge tower is coated with a waterproof membrane; a shock absorber is installed inside the concrete beam body (1) of the bridge tower.

7. The bridge tower concrete crack-resistant crossbeam structure according to claim 1, characterized in that: Steel structure steel brackets include: The bottom support of the crossbeam (3) includes a support structure (6), which is supported on the bottom of the concrete crossbeam body (1) of the bridge tower. The support structure (6) is connected to a pull-out but not shear-resistant connector (5), and the support structure (6) is partially embedded in the concrete crossbeam body (1) of the bridge tower. Internal support of the crossbeam (4): includes a second support structure (7), which is supported inside the main body (1) of the concrete crossbeam of the bridge tower. The second support structure (7) is connected to a pull-out but not shear-resistant connector (5).

8. A construction method for a bridge tower concrete crack-resistant beam structure according to any one of claims 1-7, characterized in that: include: Step 1: Erect a steel structure support frame, which includes a bottom support (3) for the crossbeam and an internal support (4) for the crossbeam, as a permanent support structure for the main body (1) of the concrete crossbeam of the bridge tower; Step 2: Construct the internal steel reinforcement structure of the main body (1) of the concrete beam of the bridge tower outside the crossbeam of the steel structure bracket (4), and cover the outer longitudinal steel bars (12) with wire mesh (14), and at the same time set up a shock damper inside the beam structure. Step 3: Pour concrete on both sides of the main body of the bridge tower concrete beam (1), and reserve a post-pouring strip (2) in the middle between the two sides; Step 4: After the concrete (11) has initially set, early curing is carried out by steam curing or wet curtain moisturizing. Step 5: Apply a waterproof membrane to the surface of the beam; Step 6: After the shrinkage rate of the concrete on both sides of the main body of the bridge tower concrete beam (1) reaches the preset ratio of the corresponding final shrinkage rate, the post-pouring strip (2) is constructed to form the bridge tower concrete crack-resistant beam structure.

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