Method for quickly constructing pre-stress system of post-tensioned pre-stress bent cap in winter

Abstract

The invention discloses a method for quickly constructing a pre-stressed system of a post-tensioned pre-stressed cover beam in winter, and belongs to the technical field of cover beam construction. Comprising the steps that S1, a steel reinforcement framework, prestressed pipes, prestressed steel bars and the like are fixed according to a cover beam design drawing; s2, a plurality of wireless temperature sensors are arranged on the bent cap steel bars for temperature monitoring; s3, determining raw materials and dosage of capping beam concrete, and mixing the concrete; s4, the cover beam concrete is transported; s5, cover beam concrete is poured; s6, the whole process from pouring to hardening of the bent cap concrete is subjected to heat preservation and maintenance; s7, setting a temperature matching maintenance test piece, and determining a tensioning opportunity according to the compressive strength and the elastic modulus of the test piece; s8, selecting a grouting opportunity according to the temperature monitored by the wireless temperature sensor; and S9, quick-hardening phosphate mortar is selected, heating and heat preservation measures are applied, and anchor sealing concrete construction is conducted. According to the method, the winter construction speed of the post-tensioned prestressed cover beam can be increased, and the construction quality is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of bent cap construction, in particular to a method for winter period rapid construction of prestressed system of post-tensioned prestressed bent cap. BACKGROUND

[0002] In urban viaduct construction, in order to reduce the land area occupied by the bridge, improve the construction efficiency, and reduce the influence on the surrounding traffic, the large cantilever prestressed bent cap structure is more and more common in urban viaduct engineering. The construction speed of the large cantilever prestressed bent cap is restricted by the prestressed system construction such as prestressed tensioning, grouting, and anchor sealing. Especially in the winter period construction in the northern region, the concrete strength grows slowly, the prestressed tensioning age is long, the grouting material strength grows slowly or is prone to freezing in the early stage, which significantly reduces the construction efficiency of the prestressed bent cap. Moreover, if the grouting material freezes in the early stage, the bent cap will appear cracks along the duct, and if the anchor sealing concrete freezes in the early stage, it will also lose the protection function of the prestressed anchor, which seriously affects the service safety and durability of the bridge. Therefore, it is urgent to develop a method for winter period rapid construction of prestressed system of post-tensioned prestressed bent cap. SUMMARY

[0003] To solve the above technical problems, the present application provides a method for winter period rapid construction of prestressed system of post-tensioned prestressed bent cap, which improves the winter period construction speed of post-tensioned prestressed bent cap and ensures the construction quality.

[0004] The technical scheme adopted by the present application is: A method for winter period rapid construction of prestressed system of post-tensioned prestressed bent cap, comprising the steps of: S1, installing a bent cap framework According to the bent cap design drawing, fix the reinforcement framework, prestressed pipe and prestressed reinforcement, and combine the side mold, end mold and bottom mold; S2, installing temperature sensors for temperature monitoring After combining the molds, arrange a plurality of wireless temperature sensors on the bent cap reinforcement framework for temperature monitoring, and wirelessly connect the wireless temperature sensors with the temperature display instrument to obtain the real-time temperature; S3, mixing bent cap concrete Determine the bent cap concrete raw materials and the amount, and mix the concrete, ensure that the concrete mixture is evenly stirred, and the out-machine temperature of the concrete mixture is not less than 15℃; S4, transporting bent cap concrete After the concrete for the cap beam is mixed, it is transported by concrete mixer truck or transport pump. When using mixer truck to transport concrete, the inlet of the mixer truck is covered with cotton quilt for insulation, the outside of the tank is wrapped with insulation tarpaulin, and the distance between the mixing plant and the construction site is controlled within 30 minutes. The tank is rotated at low speed during transportation. When using transport pump to transport concrete, the transport pump is wrapped with rain and snowproof cotton quilt or rock wool for insulation. S5. Pouring concrete for the cap beam. After the concrete is transported to the construction site, slump and temperature are tested. The slump is not less than 180mm and the temperature of the concrete entering the formwork is not less than 10℃. Sufficient concrete mixer trucks or transport pumps are provided to ensure a continuous supply of concrete and to ensure that the cap beam is poured in one go. This ensures the hydration heat release of the concrete in the overall structure and the pouring is carried out during the hottest part of the day. S6. Curing the cap beam concrete The concrete cap beam is kept insulated and cured throughout the entire process from before pouring to after hardening, and the concrete is cured with the formwork in place for 3 days after pouring. The insulation measures for the sides and ends of the cap beam are completed before the concrete is poured, and the insulation measures for the top surface of the cap beam are constructed after the concrete is poured. S7. Determine the timing of prestressing tensioning of the cap beam. The timing of prestressing tensioning of the cap beam is determined by setting up temperature-matched curing specimens, and using the compressive strength and elastic modulus of the temperature-matched curing specimens as the basis for judgment. S8. Determine the timing of grouting. After the prestressing of the cap beam is completed, the timing of grouting is selected based on the temperature monitored by the wireless temperature sensor in step S2. S9, Anchor Sealing Concrete Construction After the grout has fully hardened, the anchoring template is laid. Quick-hardening phosphate mortar with 20-30 wt% crushed stone is used to anchor the cap beam. Electric heating tape is laid on the surface of the anchoring template with a spacing of 20-40 cm. Then, 6-8 cm of polyurethane foam insulation material is sprayed on. The electric heating tape is continuously energized and heated throughout the entire process of anchoring concrete pouring and hardening until the end concrete is fully hardened.

[0005] Furthermore, the wireless temperature sensor placement points in step S2 include: the geometric center of the cap beam, 5cm from the bottom surface of the cap beam, 5cm from the top surface of the cap beam, 5cm from the side surface of the cap beam, at the prestressed duct, and 5cm directly behind the end prestressed anchor plate.

[0006] The positions 5cm from the bottom surface, top surface, and side surface of the cap beam are the positions 5cm away from the bottom surface, top surface, and side surface of the cap beam, respectively.

[0007] The aforementioned wireless temperature sensor was removed after the prestressed system of the cap beam was completed.

[0008] Further, in step S3, the raw materials for the cap beam concrete include cementitious materials, aggregates, mixing water, and admixtures; the cementitious materials include cement and fly ash, the cement is silicate cement, the cement strength grade is ≥52.5, the cement temperature is ≤55℃, and the cement dosage is ≥360 kg / m³. 3 The fly ash is Class F, Grade I fly ash, with a fly ash content ≤ 15 wt% of the cement content; the aggregate includes coarse aggregate and fine aggregate, with the coarse aggregate content being 1050~1100 kg / m³. 3 The fine aggregate dosage is 690~740 kg / m³. 3 The coarse aggregate has a moisture content of ≤1%, the fine aggregate has a moisture content of ≤3%, and the aggregate temperature is ≥5℃; the mixing water dosage is 32~34wt% of the cementitious material, and the mixing water temperature is 50~60℃; the admixtures include antifreeze and water-reducing agent, the antifreeze is a chloride-free antifreeze, the antifreeze dosage is 2~5wt% of the cementitious material, and the water-reducing agent is a polycarboxylate water-reducing agent, the water-reducing agent dosage is 1~1.5wt% of the cementitious material.

[0009] Furthermore, the concrete mixing sequence in step S3 is as follows: first, add aggregate and 3 / 4 of the mixing water and mix for 20-40 seconds; then add cement and fly ash and mix for 20-40 seconds; finally, add antifreeze, water-reducing agent and the remaining 1 / 4 of the mixing water and mix for 100-150 seconds to mix the concrete evenly.

[0010] Further, the insulation measures for the sides and ends of the cap beam in step S6 are as follows: the sides of the cap beam are insulated using a heat storage method, that is, a 6-8cm layer of polyurethane foam insulation material is evenly sprayed onto the outer surface of the side formwork of the cap beam; the ends of the cap beam are insulated using a combination of heat storage and heating methods, that is, electric heating strips are laid on the outer surface of the end formwork of the cap beam, with a spacing of 20-40cm between the electric heating strips, and a template temperature sensor is placed between two adjacent electric heating strips. Then, a 6-8cm layer of polyurethane foam insulation material is evenly sprayed onto the outer surface of the end formwork, and the prestressing duct openings of the end face of the cap beam are sealed with cotton quilts; the template temperature sensor is electrically connected to the electric heating strip controller, and the temperature threshold is set to 30℃. When the template temperature sensor temperature is below 30℃, the electric heating strip automatically turns on to heat the end formwork and concrete of the cap beam. When the temperature is above 30℃, the electric heating strip automatically turns off. The insulation measures for the top surface of the cap beam are as follows: after the concrete is poured, the top surface of the cap beam is insulated with three layers of plastic sheeting, waterproof cotton quilt, and waterproof tarpaulin.

[0011] Furthermore, the thermal conductivity of the polyurethane foam insulation material is no greater than 0.03 W / (m·K), and the closed-cell rate is greater than 92%. The electric heating band consists of a copper core wire, a PTC conductive plastic layer, a flame-retardant polyolefin insulation layer, and a tin-plated copper braided mesh shielding layer. Its maximum surface operating temperature is greater than 50°C, its rated power is greater than 20W / m, and its dielectric strength is greater than 2000V / min.

[0012] Further, step S7 specifically includes: During the pouring of the cap beam concrete, concrete specimens are made. After molding, the concrete specimens are immediately placed in a temperature matching curing chamber. The curing temperature of the temperature matching curing chamber is set according to the temperature monitored by the wireless temperature sensor located 5cm behind the prestressed anchor plate at the end of the cap beam in step S2. The test age for the compressive strength and elastic modulus of the concrete specimens is set, and the concrete strength of the concrete specimens in the temperature matching curing chamber is tested. When the compressive strength and elastic modulus of the concrete specimens at a certain age meet the design requirements, the prestressing of the cap beam is tensioned.

[0013] Further, step S8 specifically includes: After the prestressing of the cap beam is completed, the timing of grouting is selected based on the temperature monitored by the wireless temperature sensor at the prestressing duct in step S2. When the temperature at the prestressing duct is ≥10℃, grouting is carried out during a time when the temperature is higher in the day. When the temperature at the prestressing duct is <10℃, the prestressing duct needs to be heated to above 10℃ using a hot air blower before grouting. After grouting is completed, the temperature monitored by the wireless temperature sensor at the prestressing duct is monitored in real time. If the temperature drops sharply to below zero, the cap beam needs to be re-wrapped and heated. Specifically, it can be wrapped with cotton quilts and rainproof tarpaulins and heated to above 10℃ using a hot air blower.

[0014] Furthermore, in step S8, when grouting, the grouting material is selected as a fast-setting, early-strength type, with a final setting time of less than 120 minutes and a 3-hour compressive strength greater than 30 MPa. Further, in step S9, the fast-setting phosphate cement mortar used for anchor sealing has a final setting time of less than 60 minutes, a 3-hour compressive strength greater than 25 MPa, a 1-day compressive strength greater than 40 MPa, a 1-day flexural strength greater than 5 MPa, a 28-day compressive strength greater than 50 MPa, a 28-day flexural strength greater than 9 MPa, and no shrinkage; the crushed stone is clean crushed stone with a particle size of 10-20 mm, a mud content of less than 0.5%, and a water absorption rate of less than 1.0%.

[0015] The beneficial effects of this invention are as follows: (1) This invention provides a method for rapid construction of a post-tensioned prestressed cap beam in winter. By using antifreeze to prepare antifreeze concrete and implementing different heat preservation measures on the side and end face of the cap beam, the cap beam concrete can make full use of its own heat of hydration during the pouring and curing stage, which not only avoids early freezing, but also enables the concrete strength to develop rapidly. At the same time, it also ensures the normal setting and hardening of the concrete near the prestressed duct at the end of the cap beam and the rapid development of its strength. (2) The present invention adopts a temperature matching curing method that matches the solid temperature to evaluate the development law of the compressive strength and elastic modulus of the solid structure concrete. It can simulate the temperature environment of the solid concrete, more accurately characterize the performance development of the solid structure concrete, thereby accurately judging the timing of the prestressed tendon tensioning construction, and can also shorten the tensioning age and improve the construction efficiency of the prestressed system. (3) By monitoring the temperature of the cap beam concrete from pouring to curing, this invention can grasp the temperature of the weak parts of the cap beam, guide winter construction, and avoid early freezing. In addition, by using the duct temperature monitoring in conjunction with the early-strength grouting material, the early freezing of the prestressed duct grouting material can be avoided, and cracks along the prestressed duct can be avoided in the cap beam. (3) In the construction of the anchoring concrete, the present invention uses fast-hardening mortar as concrete material and uses electric heating tape and polyurethane foam insulation material for heating and insulation, which can significantly improve the sealing efficiency, avoid early freezing of the anchoring concrete, improve the bonding performance between the anchoring concrete and the cap beam concrete, avoid the erosion of the prestressed system by external water, corrosive ions and oxygen, and improve the service safety and durability of the prestressed system. Attached Figure Description

[0016] To clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a flowchart illustrating the construction process of the present invention. Detailed Implementation

[0018] This invention provides a method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] The present invention will now be described in detail with reference to the accompanying drawings.

[0020] Example 1 Reference Figure 1 This embodiment provides a method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system, including the following steps. S1. Install the cap beam frame Fix the steel reinforcement cage, prestressed pipe and prestressed steel bars according to the design drawings of the cap beam, and then combine the side formwork, end formwork and bottom formwork.

[0021] S2. Install a temperature sensor for temperature monitoring. After the formwork is closed, several wireless temperature sensors are arranged on the steel reinforcement cage of the cap beam for temperature monitoring. The wireless temperature sensors are wirelessly connected to the temperature display. The wireless temperature sensors automatically transmit the temperature data of the monitoring points at regular intervals, such as once per hour. The temperature display receives the temperature data sent by each wireless temperature sensor, stores it, and transmits it to the display terminal, such as a mobile phone or computer. Construction personnel can view it in real time through their mobile phones or computers.

[0022] Specifically, the wireless temperature sensor placement points include: the geometric center of the cap beam, 5cm from the bottom surface of the cap beam, 5cm from the top surface of the cap beam, 5cm from the side surface of the cap beam, at the prestressed duct, and 5cm directly behind the end prestressed anchor plate.

[0023] S3, Mixing concrete for the cap beam Determine the raw materials and quantities of concrete for the cap beam, and carry out concrete mixing. Mix the concrete evenly and ensure that the discharge temperature of the concrete mixture is not lower than 15℃.

[0024] Specifically, the concrete strength grade of the cap beam is designed to be C50. The raw materials for the cap beam concrete include cement, fly ash, aggregate, mixing water, and admixtures. The cement is silicate cement with a strength grade ≥52.5, a cement temperature ≤55℃, and a cement dosage of 400 kg / m³. 3 The fly ash is Class F, Grade I fly ash, and the fly ash dosage is 70 kg / m³. 3 The aggregate includes coarse aggregate and fine aggregate, with the coarse aggregate dosage being 1100 kg / m³. 3 The fine aggregate dosage is 700 kg / m³. 3 The coarse aggregate has a moisture content of ≤1%, the fine aggregate has a moisture content of ≤3%, and the aggregate bins should be equipped with hot air blowers to ensure that the aggregate temperature is not lower than 5℃; the mixing water dosage is 158 kg / m³. 3The mixing water temperature is 50℃; the admixtures include antifreeze and water-reducing agent, the antifreeze is a chloride-free antifreeze, the dosage of antifreeze is 3wt% of cement dosage, it can be used when the daily temperature is not lower than -15℃, its water reduction rate is ≥10%, the bleeding rate is ≤80%, the air content is ≥2.5%, and the alkali content is less than 1.0kg / m³. 3 The strength loss rate after 50 freeze-thaw cycles is ≤100%, and it does not cause corrosion to steel bars; the water-reducing agent is a polycarboxylate water-reducing agent, and the amount of water-reducing agent is 1.2wt% of the cement content.

[0025] The mixing sequence for the above-mentioned cap beam concrete is as follows: The ambient temperature of the concrete mixer is 10℃. During mixing, first add the aggregate and 3 / 4 of the mixing water and mix for 20-40 seconds. Then add the cement and fly ash and mix for another 20-40 seconds. Finally, add the antifreeze agent, water-reducing agent, and the remaining 1 / 4 of the mixing water and mix for 100-150 seconds to ensure the concrete is thoroughly mixed. After the concrete mixing is complete, the outlet temperature is 16-19℃.

[0026] S4, Transporting concrete for the cap beam After the concrete for the cap beam is mixed, it is transported by concrete mixer truck. When using mixer trucks to transport concrete, the inlet of the mixer truck is covered with cotton quilts for insulation, and the outside of the tank is wrapped with a 5cm thick insulation tarpaulin. The distance between the mixing plant and the on-site construction site is controlled within 30 minutes, and the tank is rotated at a low speed during transportation.

[0027] S5. Pouring concrete for the cap beam. After the concrete is transported to the construction site, the ambient temperature is -5~10℃. Slump and temperature tests are conducted first. The slump is 190mm, and the placement temperature is 13~16℃. The cap beam is poured in one go, ensuring a continuous supply of concrete to guarantee the heat release during hydration of the overall structure. Pouring is carried out during the warmest part of the day. The pouring sequence is from one side of the cap beam to the other, layer by layer, pouring the perimeter first and then the center. An immersion vibrator is used to compact the concrete, inserting it 10cm into the lower layer. The vibration spacing is matched to the radius of action to ensure uniform and dense compaction. After pouring, the surface is promptly finished and covered with plastic sheeting, blankets, and waterproof tarpaulins for insulation and moisture retention.

[0028] S6. Curing the cap beam concrete The concrete cap beam is kept insulated and cured throughout the entire process from before pouring to after hardening, and is cured with the formwork in place for 3 days after the concrete is poured. The insulation measures for the sides and ends of the cap beam are completed before the concrete is poured, and the insulation measures for the top surface of the cap beam are constructed after the concrete is poured.

[0029] Specifically, the sides of the cap beam are insulated using a heat storage method, which involves uniformly spraying a 6-8cm layer of polyurethane foam insulation material onto the outer surface of the side formwork. The end face of the cap beam is insulated using a combination of heat storage and heating methods. This involves laying electric heating strips on the outer surface of the end formwork, with a spacing of 30cm between the strips, and placing formwork temperature sensors between adjacent strips. Then, a 6-8cm layer of polyurethane foam insulation material is uniformly sprayed onto the outer surface of the end formwork, and the prestressing ducts at the end face of the cap beam are sealed with cotton blankets. The formwork temperature sensors are electrically connected to the electric heating strip controller, with a set temperature threshold of 30℃. When the temperature sensor temperature is below 30℃, the electric heating strips automatically turn on to heat the end formwork and concrete. When the temperature exceeds 30℃, the electric heating strips automatically turn off. After the concrete is poured, the top surface of the cap beam is insulated with three layers of plastic sheeting, waterproof cotton blankets, and waterproof tarpaulins. Furthermore, the cap beam and formwork are cured for 3 days after pouring.

[0030] In addition, the thermal conductivity of the above-mentioned polyurethane foam insulation material is no greater than 0.03 W / (m·K), and the closed-cell rate is greater than 92%; the above-mentioned electric heating belt is composed of copper core wire, PTC conductive plastic layer, flame-retardant polyolefin insulation layer, and tin-plated copper braided mesh shielding layer, with a maximum surface operating temperature greater than 50℃, rated power greater than 20W / m, and dielectric strength greater than 2000V / min.

[0031] S7. Determine the timing of prestressing tensioning of the cap beam. The timing of prestressing tensioning of the cap beam is determined by setting up temperature-matched curing specimens, using the compressive strength and elastic modulus of the temperature-matched curing specimens as the basis for judgment.

[0032] Specifically, during the pouring of the cap beam concrete, six sets of concrete specimens were prepared for compressive strength and modulus of elasticity testing at ages of 3d, 4d, 5d, 6d, 7d, and 28d. After molding, the concrete specimens were immediately placed in a temperature matching curing chamber. The curing temperature of the temperature matching curing chamber was set according to the temperature monitored by the wireless temperature sensor located 5cm behind the prestressed anchor plate at the end of the cap beam in step S2. When the test age was reached, the concrete strength of the concrete specimens in the temperature matching curing chamber was tested. When the compressive strength and modulus of elasticity of the concrete specimens at a certain age met the design requirements, the prestressing of the cap beam was tensioned.

[0033] S8. Determine the timing of grouting. After the prestressing of the cap beam is completed, the timing of grouting is selected based on the temperature monitored by the wireless temperature sensor at the prestressing duct in step S2. When the temperature at the prestressing duct is ≥10℃, grouting is carried out during the day when the temperature is higher. When the temperature at the prestressing duct is <10℃, the prestressing duct needs to be heated to above 10℃ using a hot air blower before grouting. After grouting is completed, the temperature monitored by the wireless temperature sensor at the prestressing duct is monitored in real time. If the temperature drops sharply to below zero, the cap beam needs to be re-wrapped and heated. Specifically, it can be wrapped with cotton quilts and rainproof tarpaulins and heated to above 10℃ using a hot air blower to prevent the grout material in the duct from freezing prematurely.

[0034] In addition, when performing grouting, the grouting material should be fast-hardening and early-strength type, with a final setting time of less than 120 minutes and a compressive strength of more than 30 MPa after 3 hours.

[0035] S9, Anchor Sealing Concrete Construction After the grout has fully hardened, the anchoring template is laid. Quick-hardening phosphate mortar with 20-30 wt% crushed stone is used to anchor the cap beam. Electric heating tape is laid on the surface of the anchoring template with a spacing of 30 cm. Then, 6-8 cm of polyurethane foam insulation material is sprayed on. The electric heating tape is continuously energized and heated throughout the entire process of anchoring concrete pouring and hardening until the end concrete is fully hardened.

[0036] In step S9, the fast-setting phosphate cement mortar used for anchor sealing has a final setting time of less than 60 minutes, a compressive strength of greater than 25 MPa at 3 hours, a compressive strength of greater than 40 MPa at 1 day, a flexural strength of greater than 5 MPa at 1 day, a compressive strength of greater than 50 MPa at 28 days, a flexural strength of greater than 9 MPa at 28 days, and no shrinkage. The crushed stone is clean crushed stone with a particle size of 10-20 mm, a mud content of less than 0.5%, and a water absorption rate of less than 1.0%.

[0037] The thermal conductivity of the aforementioned polyurethane foam insulation material is no greater than 0.03 W / (m·K), and the closed-cell rate is greater than 92%. The aforementioned electric heating belt is composed of a copper core wire, a PTC conductive plastic layer, a flame-retardant polyolefin insulation layer, and a tin-plated copper braided mesh shielding layer. Its maximum surface operating temperature is greater than 50℃, its rated power is greater than 20W / m, and its dielectric strength is greater than 2000V / min.

[0038] Comparative Example 1 This comparative example provides a method for winter construction of a post-tensioned prestressed cap beam prestressed system. The difference between this method and Example 1 is that: in step S6, cotton quilts are used instead of polyurethane foam for insulation, and electric heating tape is not used; in step S7, specimens cured under the same conditions are used instead of those cured under temperature matching conditions to determine the prestressing tensioning age.

[0039] The compressive strength and static modulus of elasticity of concrete in Example 1 and Comparative Example 1 were tested according to GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", as shown in Table 1. Table 1 shows that the compressive strength and modulus of elasticity of concrete in Comparative Example 1 at all ages are lower than those in Example 1, and at 7 days, the compressive strength does not meet the requirements for C50 concrete, failing to meet the tensioning design requirements. In contrast, the compressive strength and modulus of elasticity in Example 1 meet the requirements for tensioning construction at 5 days, significantly improving the construction efficiency of the prestressed system.

[0040] Table 1. Test results of compressive strength and static compressive modulus of elasticity of concrete. It should be noted that any parts not mentioned in this invention can be achieved by using or referencing existing technologies.

[0041] Of course, the above description is not intended to limit the present invention, and the present invention is not limited to the examples given above. Any changes, modifications, additions or substitutions made by those skilled in the art within the scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system, characterized in that, Including the following steps: S1. Install the cap beam frame Fix the steel reinforcement cage, prestressed pipe and prestressed steel bars according to the design drawings of the cap beam, and then combine the side formwork, end formwork and bottom formwork. S2. Install a temperature sensor for temperature monitoring. After the mold is closed, several wireless temperature sensors are arranged on the steel reinforcement cage of the cap beam for temperature monitoring, and the wireless temperature sensors are wirelessly connected to the temperature display to obtain the real-time temperature. S3, Mixing concrete for the cap beam Determine the raw materials and quantities of concrete for the cap beam, and carry out concrete mixing. Mix the concrete evenly and ensure that the discharge temperature of the concrete mixture is not lower than 15℃. S4, Transporting concrete for the cap beam After the concrete for the cap beam is mixed, it is transported by concrete mixer truck or transport pump. When using mixer truck to transport concrete, the inlet of the mixer truck is covered with cotton quilt for insulation, the outside of the tank is wrapped with insulation tarpaulin, and the distance between the mixing plant and the construction site is controlled within 30 minutes. The tank is rotated at low speed during transportation. When using transport pump to transport concrete, the transport pump is wrapped with rain and snowproof cotton quilt or rock wool for insulation. S5. Pouring concrete for the cap beam. After the concrete is transported to the construction site, slump and temperature are tested. The slump is not less than 180mm and the temperature when it is poured into the formwork is not less than 10℃. Sufficient concrete mixer trucks or transport pumps are provided to ensure a continuous supply of concrete and to ensure that the cap beam is poured in one go. The pouring is carried out during the time of day when the temperature is higher. S6. Curing the cap beam concrete The concrete cap beam is kept insulated and cured throughout the entire process from before pouring to after hardening, and the concrete is cured with the formwork in place for 3 days after pouring. The insulation measures for the sides and ends of the cap beam are completed before the concrete is poured, and the insulation measures for the top surface of the cap beam are constructed after the concrete is poured. S7. Determine the timing of prestressing tensioning of the cap beam. The timing of prestressing tensioning of the cap beam is determined by setting up temperature-matched curing specimens, and using the compressive strength and elastic modulus of the temperature-matched curing specimens as the basis for judgment. S8. Determine the timing of grouting. After the prestressing of the cap beam is completed, the timing of grouting is selected based on the temperature monitored by the wireless temperature sensor in step S2. S9, Anchor Sealing Concrete Construction After the grout has fully hardened, the anchoring template is laid. Quick-hardening phosphate mortar with 20-30 wt% crushed stone is used to anchor the cap beam. Electric heating tape is laid on the surface of the anchoring template with a spacing of 20-40 cm. Then, 6-8 cm of polyurethane foam insulation material is sprayed on. The electric heating tape is continuously energized and heated throughout the entire process of anchoring concrete pouring and hardening until the end concrete is fully hardened.

2. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 1, characterized in that, The wireless temperature sensor placement points in step S2 include: the geometric center of the cap beam, 5cm from the bottom surface of the cap beam, 5cm from the top surface of the cap beam, 5cm from the side surface of the cap beam, at the prestressed duct, and 5cm directly behind the end prestressed anchor plate.

3. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 1, characterized in that, In step S3, the raw materials for the cap beam concrete include cementitious materials, aggregates, mixing water, and admixtures. The cementitious materials include cement and fly ash; the cement is silicate cement with a strength grade ≥52.5, a cement temperature ≤55℃, and a cement dosage ≥360kg / m³. 3 The fly ash content is ≤15wt% of the cement content; the aggregate includes coarse aggregate and fine aggregate, and the coarse aggregate content is 1050~1100 kg / m³. 3 The fine aggregate dosage is 690~740 kg / m³. 3 The coarse aggregate has a moisture content of ≤1%, the fine aggregate has a moisture content of ≤3%, and the aggregate temperature is ≥5℃; the mixing water dosage is 32~34wt% of the total cement and fly ash dosage, and the mixing water temperature is 50~60℃; the admixtures include antifreeze and water-reducing agent, the antifreeze is a chloride-free antifreeze, the antifreeze dosage is 2~5wt% of the cementitious material dosage, and the water-reducing agent is a polycarboxylate water-reducing agent, the water-reducing agent dosage is 1~1.5wt% of the cementitious material dosage.

4. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 3, characterized in that, The concrete mixing sequence in step S3 is as follows: first, add aggregate and 3 / 4 of the mixing water and mix for 20-40 seconds; then add cement and fly ash and mix for 20-40 seconds; finally, add antifreeze, water-reducing agent and the remaining 1 / 4 of the mixing water and mix for 100-150 seconds to make the concrete uniform.

5. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 1, characterized in that, The insulation measures for the sides and ends of the cap beam in step S6 are as follows: The sides of the cap beam are insulated using a heat storage method, i.e., a 6-8cm layer of polyurethane foam insulation material is evenly sprayed onto the outer surface of the side formwork; the ends of the cap beam are insulated using a combination of heat storage and heating methods, i.e., electric heating strips are laid on the outer surface of the end formwork, with a spacing of 20-40cm between the electric heating strips, and a template temperature sensor is placed between adjacent electric heating strips. Then, a 6-8cm layer of polyurethane foam insulation material is evenly sprayed onto the outer surface of the end formwork, and the prestressing duct openings on the end face of the cap beam are sealed with cotton quilts; the template temperature sensor is electrically connected to the electric heating strip controller, and a temperature threshold of 30℃ is set. When the template temperature sensor temperature is below 30℃, the electric heating strip automatically turns on to heat the end formwork and concrete of the cap beam; when the temperature is above 30℃, the electric heating strip automatically turns off. The insulation measures for the top surface of the cap beam are as follows: after the concrete is poured, the top surface of the cap beam is insulated with three layers of plastic sheeting, waterproof cotton quilt, and waterproof tarpaulin.

6. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 5, characterized in that, The thermal conductivity of the polyurethane foam insulation material is no greater than 0.03 W / (m·K), and the closed-cell rate is greater than 92%. The electric heating band consists of a copper core wire, a PTC conductive plastic layer, a flame-retardant polyolefin insulation layer, and a tin-plated copper braided mesh shielding layer. Its maximum surface operating temperature is greater than 50°C, its rated power is greater than 20W / m, and its dielectric strength is greater than 2000V / min.

7. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 2, characterized in that, Step S7 specifically involves: During the pouring of the cap beam concrete, concrete specimens are made. After molding, the concrete specimens are immediately placed in a temperature matching curing chamber. The curing temperature of the temperature matching curing chamber is set according to the temperature monitored by the wireless temperature sensor located 5cm behind the prestressed anchor plate at the end of the cap beam in step S2. The test age for the compressive strength and elastic modulus of the concrete specimens is set, and the concrete strength of the concrete specimens in the temperature matching curing chamber is tested. When the compressive strength and elastic modulus of the concrete specimens at a certain age meet the design requirements, the prestressing of the cap beam is tensioned.

8. The method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 2, characterized in that, Step S8 specifically involves: After the prestressing of the cap beam is completed, the timing of grouting is selected based on the temperature monitored by the wireless temperature sensor at the prestressing duct in step S2. When the temperature at the prestressing duct is ≥10℃, grouting is carried out during the day when the temperature is higher. When the temperature at the prestressing duct is <10℃, a hot air blower is needed to heat the prestressing duct before grouting. After grouting is completed, the temperature monitored by the wireless temperature sensor at the prestressing duct is monitored in real time. If the temperature drops sharply, the cap beam needs to be re-wrapped and heating measures need to be taken.

9. A method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 1, characterized in that, When performing grouting in step S8, the grouting material should be a fast-hardening, early-strength type with a final setting time of less than 120 minutes and a compressive strength of more than 30 MPa after 3 hours.

10. A method for rapid winter construction of a post-tensioned prestressed cap beam prestressed system according to claim 1, characterized in that, In step S9, the fast-setting phosphate cement mortar used for anchor sealing has a final setting time of less than 60 minutes, a compressive strength of greater than 25 MPa at 3 hours, a compressive strength of greater than 40 MPa at 1 day, a flexural strength of greater than 5 MPa at 1 day, a compressive strength of greater than 50 MPa at 28 days, a flexural strength of greater than 9 MPa at 28 days, and no shrinkage. The crushed stone is clean crushed stone with a particle size of 10-20 mm, a mud content of less than 0.5%, and a water absorption rate of less than 1.0%.

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