Post-tensioned prestressed seamless concrete floor construction method

Abstract

The application relates to the field of building technology, in particular to a post-tensioned prestressed seamless concrete floor construction method. In the construction preparation step, a strain sensing sensor is arranged, and a steel strand with a protective sleeve is arranged; in the concrete pouring step, concrete with good early strength is adopted; in the prestressed tensioning step, the stress and tension are monitored through a preset sensor, the strain value when the floor first cracks is determined, the initial value for starting the tensioning device is determined, and the tensioning device is controlled to start tensioning operation. Subsequent control is realized through a control system according to the information monitored by the sensor and the instruction control, and the preset threshold value is preferably less than the initial value for starting the tensioning device, so that the tensioning is started before the internal stress of the concrete is insufficient to cause cracks, and the tensioning process is effectively controlled before the cracks are generated, so that the floor is ensured not to generate cracks.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building technology, in particular to a post-tensioned prestressed seamless concrete floor construction method. BACKGROUND

[0002] The concrete floor refers to the ground which is processed by using specific materials and processes and has certain functionality. The concrete floor is the part of the bottom room which contacts with the soil layer, and it bears the load of the bottom room, and is required to have certain strength and rigidity, and has the properties of moisture-proof, waterproof, warm-keeping and wear-resistant.

[0003] The longer and larger the concrete structure is, the greater the structural constraint stress caused by the early hydration heat, shrinkage and temperature change of the concrete is, and cracks are easily generated. In the traditional method, the concrete construction joints are set at intervals in the construction of the concrete floor. Generally, after the overall structure concrete is poured, the micro-expansion concrete with a higher grade than the original structure is used to construct the post-pouring belt. The stress is released by leaving the post-pouring belt, but the construction period is too long, and the process of cleaning and chiseling the structure surface on both sides of the post-pouring belt is complicated and has leakage risks. In the prior art, the expansion reinforcing belt is set to solve the problem of concrete cracks in the construction process without leaving the post-pouring belt, and the expansion stress of the expansion reinforcing belt is used to resist the tensile stress of the concrete. At present, there are also some large-volume concrete floors. The prestressed reinforcement is arranged in the concrete, and after the strength of the concrete reaches the design requirement, the prestressed reinforcement is tensioned to apply a prestressed pressure to the concrete, so as to solve the shrinkage stress of the concrete itself and resist the external load during the normal use of the floor, thereby effectively solving the problem of easy cracking of the floor.

[0004] For large workshops such as aircraft maintenance hangar halls and large-area concrete floors, seamless concrete floors are needed. The ground of the hangar hall is deep in depth, and the length of a single hall is long, and the length of multiple halls combined is longer. The thickness of the floor concrete is generally about 200-300 mm. The post-tensioned prestressed reinforcement is arranged in the concrete, and the concrete itself has shrinkage stress, which is prone to cracking.

[0005] In the construction, the difficulty is that the prestressed reinforcement needs to be tensioned after the concrete reaches a certain strength, but after the concrete reaches the tensioning strength, the shrinkage deformation has been generated and cracks have been generated. Therefore, the inventor believes that how to improve the stress state in the concrete before the cracks are generated and eliminate the shrinkage stress is one of the keys to solve the cracks of the prestressed concrete floor. SUMMARY

[0006] In order to implement the early post-tensioned prestressed construction of the large concrete seamless floor, the present application provides a post-tensioned prestressed seamless concrete floor construction method.

[0007] The application provides a post-tensioned prestressed seamless concrete floor construction method, which adopts the following technical scheme:

[0008] The application provides a post-tensioned prestressed seamless concrete floor construction method, which comprises the following steps:

[0009] In the construction preparation step, a strain sensing sensor is arranged, a steel strand with a protective sleeve is arranged, and a plurality of shrinkage bars are arranged at intervals in the floor range, the shrinkage bar is a sealed air bag structure, the structure of the shrinkage bar is an olive ball shape arranged vertically, the distance from the top surface of the floor and the bottom surface of the floor is 2-5 mm in the vertical direction, and the diameter of the middle part is 50 mm; the shrinkage bar is vertically inserted into the concrete, one shrinkage bar is arranged every 2 square meters to form a 2 square meter matrix structure.

[0010] In the concrete pouring step, the concrete is prepared by using early strength concrete, such as ordinary Portland cement, and the cement parameter is 290-310 kg per cubic meter, and an additive is added to improve the early strength without obviously damaging the late strength; the strain sensing sensor is poured into the concrete.

[0011] In the concrete curing step, a prestressed tensioning device is installed, and a tensioning force sensor is installed; the strain sensing sensor and the tensioning force sensor are connected with a control box, the strain sensing sensor is connected with the control box through a wireless communication module of a sensor with a wireless module, so that the strain signal collected by the strain sensing sensor and the tensioning force signal collected by the tensioning force sensor are fed back to the control system of the control box, the control box is a PCL control box with a built-in control program, and the control system is provided with a timer; the control system is also provided with an alarm, when the tension value is equal to or greater than a preset tension threshold, the alarm sends an alarm signal, the alarm signal can be sent to a local alarm device or an external display control system; and the concrete is saturated and cured at the end of the curing time.

[0012] In the prestressed tensioning step,

[0013] When the floor first cracks, the strain sensing sensor collects the strain value in real time, and the strain value is set as the initial value of the starting tensioning device in the control system; a plurality of strain sensing sensors are arranged, the strain values collected by the plurality of strain sensing sensors are read, the minimum value in the effective values is taken as the initial value of the starting tensioning device in the control system, and if the detection value of an individual strain sensing sensor deviates obviously and exceeds the allowed range of deviation, the value is discarded.

[0014] According to the initial value of starting the tensioning device, a first threshold value at which the tensioning device stops tensioning is set, and a second threshold value at which the tensioning device is started again is set; the first threshold value is set to be 40% to 100% of the initial value of starting the tensioning device; the second threshold value is set to be 80% to 100% of the initial value of starting the tensioning device; and the first threshold value is less than the second threshold value;

[0015] The counter of the control program also sets a period of adjacent monitoring, and the period from the last time the tensioning stops to the time when the strain value rises to the second threshold value again;

[0016] After the strain sensing sensor collects the strain value for the first time to reach the initial value of starting the tensioning device, the related parameters are set, the tensioning device is started to tension the steel strand, and in the tensioning process, the tension force sensor collects the tension value in real time, and the strain sensing sensor collects the strain value in real time;

[0017] When the tension value is less than the preset tension threshold value, and the strain value drops to the first threshold value, the tensioning is stopped; the strain value is continuously collected in real time, until the strain value rises to the second threshold value again within the time length set by the timer, the tensioning device is started again to tension the steel strand, and in the tensioning process, the tension value and the strain value are collected; when the strain value drops to the first threshold value, the tensioning is stopped, and the cycle is repeated;

[0018] When the strain value cannot rise to the second threshold value again within the time length set by the timer, that is, when the strain value changes little, the tensioning force is less than the designed prestress value, the tensioning device is started multiple times to tension the steel strand, until the tension value reaches the preset tension threshold value, and the tensioning process ends;

[0019] The gap formed by tensioning the steel strand in the concrete is grouted, the grouting concrete has a strength higher than that of the original cast concrete, and the tensioning device and the control box are removed.

[0020] By adopting the above technical scheme, in the post-tensioned prestressed seamless concrete floor construction process, the concrete uses a concrete with good early strength, so that the concrete has good early strength and can perform tensioning operation in advance. By monitoring the stress and tension through the preset sensor, after the strain value at which the floor first cracks is determined, the initial value of starting the tensioning device is determined, and the tensioning device is controlled to perform tensioning operation. The subsequent control is controlled by the control system according to the information monitored by the sensor and the instruction, and the preset threshold value is preferably less than the initial value of starting the tensioning device, that is, the tensioning is started before the stress in the concrete is not enough to cause cracks, so that the tensioning process is effectively controlled before the cracks are generated, to ensure that the floor does not crack.

[0021] By adopting the technical scheme, the first threshold value is used as a stop threshold value after tensioning, that is, when the tensioning device tension the steel strand each time, over-tensioning is avoided, and the internal stress of the concrete reaches a reasonable degree. The second threshold value is used as a start threshold value of tensioning, and is set before cracks occur or just after cracks occur, preferably before cracks occur, so that the internal stress of the concrete is not enough to cause cracks during subsequent tensioning, thereby effectively avoiding the generation of cracks.

[0022] By adopting the technical scheme, the design value provided by the design party of the preset tension threshold value is usually a value that meets the conditions after strict calculation. If the value is exceeded, it is possible that there is a problem in design or construction, and the construction personnel are reminded to report to the design party through the alarm to make a control plan and related inspection. The alarm is set to alarm when the tension value is equal to or greater than the preset tension threshold value, so as to remind the construction personnel to make a control warning.

[0023] By adopting the technical scheme, the alarm device can be an on-site sound and light alarm device, or can be transmitted to a remote monitoring or control system through signal transmission to timely remind relevant personnel.

[0024] By adopting the technical scheme, the shrinkage bar is placed in the concrete to set a virtual warehouse for the concrete member, improve the internal stress state of the large plate concrete, and eliminate or partially offset the shrinkage stress of the large plate concrete.

[0025] By adopting the technical scheme, a structure of the shrinkage bar is disclosed. The air bag type structure can eliminate internal stress to some extent, improve the possible stress concentration in the concrete, and prevent cracks from occurring.

[0026] By adopting the technical scheme, the final setting time of the concrete pouring is about 8-12 hours, and the water curing is performed to prevent the evaporation of water on the surface of the concrete from causing the inconsistency of the hardening speed inside and outside the member, thereby causing cracks.

[0027] By adopting the technical scheme, the gap formed by tensioning the steel strand is grouted, and the grouting concrete has a higher strength than the original pouring concrete, so as to reduce the carbonization in the concrete, reduce the corrosion of the steel strand, and improve the strength and service life of the floor.

[0028] The present application includes at least one of the following beneficial technical effects:

[0029] 1. The application monitors stress and tension through preset sensors, and controls tension operation through control program after determining the strain value when the floor first cracks. It has high automation degree, less human factor influence, and can start tension before the concrete internal stress is not enough to produce cracks, so as to effectively control the tension process before cracks occur, thereby effectively ensuring that the floor does not produce cracks.

[0030] 2. The application uses concrete with good early strength to make the concrete have good early strength, so that the tension operation can be performed in advance.

[0031] 3. The application places a shrinkage bar in the concrete to set a virtual warehouse for the concrete member, improve the internal stress state of the large slab concrete, and eliminate or partially offset the shrinkage stress of the large slab concrete.

[0032] 4. The application performs water curing at the final setting time after the concrete pouring is completed, prevents the evaporation of water on the surface of the concrete, and prevents cracks caused by the inconsistent hardening speed inside and outside the member. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a schematic flow chart of an embodiment of the construction method of the application.

[0034] Figure 2 is a schematic flow chart of an embodiment of the prestressed tensioning step of the application.

[0035] Figure 3 is a structural schematic view of an embodiment of the shrinkage bar of the application.

[0036] BRIEF DESCRIPTION OF DRAWINGS DETAILED DESCRIPTION

[0037] The application will be further described in detail below with reference to the accompanying drawings.

[0038] Generally, the depth of the hangar hall floor is about 50-90 meters, the length of a single hall is about 60-90 meters, the combined length is about 150-200 meters, and the thickness of the floor is 200-300 mm. The application controls the hydration speed of the concrete, improves the early strength of the concrete, applies prestress before the stress in the concrete breaks through the standard tensile stress Ftk of the concrete, eliminates tension, improves the internal stress state, and avoids the generation of cracks in the concrete floor. Due to the small thickness of the floor, the concrete has relatively good heat dissipation, and the temperature has relatively small influence on the concrete during the solidification process, which is not considered in the following embodiments of the application.

[0039] An embodiment of the application discloses a post-tensioned prestressed seamless concrete floor construction method. Referring to Figure 1The post-tensioned prestressed seamless concrete floor construction method comprises a construction preparation step, a concrete pouring step, a concrete curing step, a prestressed tensioning step, etc.

[0040] The preparation work mainly includes the arrangement of the floor construction site and the erection of the formwork, which is the initial preparation work of the floor construction. In the specific construction process, the foundation treatment of the floor is usually performed, and the gravel and sand cushion layer of the foundation treatment floor is laid to make the foundation surface of the floor flat and have a certain supporting capacity. The constructional reinforcement is arranged. Then, the formwork is made and installed, the periphery of the floor to be poured is surrounded, and the formwork is reinforced and supported.

[0041] In the construction preparation step, the steel strand is arranged in the formwork range as the implementation object of the post-tensioned prestress, and of course, the carbon fiber and other materials can also be arranged as the implementation object of the post-tensioned prestress. The steel strand can be arranged in a single layer and multiple parallel layers, or in multiple layers and parallel layers, or in a cross arrangement. The specific arrangement quantity and layer number can be comprehensively considered in combination with the thickness, length and width of the poured concrete, and the possible stress condition of the concrete in the subsequent use. In this embodiment, the steel strand can be arranged in a multi-layer cross distribution mode, and a protective tube is sleeved outside the steel strand to avoid the adhesion of the steel strand to the concrete after pouring and the inability to be tensioned. The two ends of the steel strand can be in contact with the formwork and protect the end of the steel strand, which is convenient for the installation of the tensioning device after solidification.

[0042] In addition, in order to more accurately infer the internal stress of the concrete through the strain gauge value, the prestress is applied before the breakthrough of Ftk to eliminate the stretching. In the construction preparation step, the strain sensing sensor is arranged in the space of the formwork for pouring the floor, and the sensor is connected with the connecting line. During pouring, the strain sensing sensor is poured into the concrete, and the connecting line is stretched out of the concrete and can be connected with the control box arranged outside. Of course, the sensor with a wireless module can also be connected with the control box through the wireless communication module. In this embodiment, a plurality of strain sensing sensors are arranged, and the control box adopts a PCL control box with a built-in control program for monitoring the monitored data and receiving and sending instructions. The built-in control program of the PCL control box also has a counter, an alarm and a timer. The timer can form a countdown through the setting of the time interval, and of course, it can also record the time point and time period. The alarm can send an alarm instruction to the corresponding alarm device.

[0043] In the construction preparation step, a plurality of shrinkage bars are arranged in the floor area, so that the interior of the concrete floor after pouring is distributed in a matrix shape. The arrangement of the shrinkage bar can eliminate stress concentration in the process of solidification and shrinkage of the large concrete slab, thereby generating cracks, etc. In the present embodiment, the shrinkage bar is a closed air bag structure, and a shrinkage bar is placed at a certain interval in the interior of the concrete, and the shrinkage bar is placed vertically. For example, one shrinkage bar is placed every 2 square meters to form a 2 square meter matrix structure. Reference Figure 3 The structure of the shrinkage bar 3 is an olive ball shape placed vertically, and the distance from the top surface of the floor 1 and the bottom surface of the floor 2 is about 2-5 mm in the vertical direction, and the diameter of the middle part is about 50 mm in the horizontal direction. The structure of the shrinkage bar can also be a concave-convex air bag structure. Of course, it can also be other structures or other sizes. Of course, it is known that this technology is applied to floors of different thicknesses, and because the internal stress generated during the solidification process is different, the arrangement interval of the shrinkage bar can be adjusted accordingly. For relatively thick floors, the shrinkage bar can be arranged in multiple layers or staggered to change the internal stress situation.

[0044] In the concrete pouring step, the strain sensing sensor is poured into the concrete, and the steel strand is poured into the concrete. During the pouring process, vibration, compaction, leveling, and light collection are performed. In order to improve the early strength of the concrete, a concrete with good early strength can be used, such as ordinary Portland cement concrete, to improve the initial compressive strength, and the cement content is about 290-310 kg per cubic meter. Additives can also be added to improve the early strength without significantly affecting the later strength.

[0045] In the concrete pouring step, laser leveling equipment can be used for laser leveling construction. The laser leveling equipment integrates scraping, vibration, and leveling into one, and the leveling coverage rate can reach more than 95%. The areas that cannot be covered are fully vibrated using a vibrating rod and leveled using a straightedge. A laser leveling system must be used to check and recheck the elevation at any time during the leveling process. The leveling efficiency is relatively high.

[0046] In the concrete curing step, saturated water curing is performed at the end of the concrete setting time. The concrete is poured and completed about 8-12 hours to reach the final setting time, and saturated water curing is performed to prevent the evaporation of water on the surface of the concrete, which can cause the hardening speed inside and outside the member to be inconsistent, resulting in cracks.

[0047] In the concrete curing process, the pre-stressed tensioning device can be installed at the steel strand, and the tension sensor can be installed. The strain sensing sensor, the tension sensor, and the control box are connected to enable the strain signal collected by the strain sensing sensor and the tension signal collected by the tension sensor to be fed back to the control system of the control box, etc. The equipment assembly and connection preparation work for pre-stressed tensioning is completed.

[0048] After preparation, in the control system of the PLC control box, the pre-tension threshold value of the steel strand is set according to the design tension given in the design file, and the proportional relationship between the first threshold value, the second threshold value and the initial value of the starting tension device, the timer cycle value and other parameters can also be set. Reference Figure 2 .

[0049] Through observation, the strain value is collected in real time when the floor first cracks. The strain value is set as the initial value of the starting tension device in the control system. In this embodiment, multiple strain sensors are provided, and when the floor first cracks, the real-time strain values collected by the multiple strain sensors are read, and the minimum value in the effective values is taken as the initial value of the starting tension device. In the subsequent monitoring, the stress value will not exceed the minimum value, that is, no cracks will occur. If the individual strain sensor detection value deviates obviously and exceeds the allowed range of deviation, the value is discarded. Of course, the effective value of the monitoring can also be used as the initial value of the starting tension device after other processing, such as the average value, the median value, the maximum value, etc.

[0050] And according to the initial value of the starting tension device, the first threshold value of the tension device stopping tension is set, and the second threshold value of the tension device starting again is set. When the system is set, the proportional relationship can be set in advance. Preferably, the first threshold value is set to 40%~100% of the initial value of the starting tension device, and the second threshold value is set to 80%~100% of the initial value of the starting tension device; and the first threshold value is less than the second threshold value. For example, in some implementation test processes of this embodiment, the first threshold value is set to 50% of the initial value of the starting tension device, and the second threshold value is set to 90% of the initial value of the starting tension device. The setting of the first threshold value avoids over-tensioning when the tension device tensioning the steel strand each time, so that the internal stress of the concrete reaches a reasonable degree. The second threshold value is set before the crack occurs, so that the internal stress of the concrete is not enough to cause a crack during subsequent tensioning, thereby effectively avoiding the generation of cracks.

[0051] The counter of the control program can also set the cycle of adjacent monitoring. For example, the cycle from the last time the tensioning stops to the time when the strain value rises to the second threshold value again.

[0052] After the strain sensor collects the strain value for the first time to reach the initial value of the starting tension device, the related parameters are set, the tension device is started to tension the steel strand, and the tension sensor collects the tension value in real time during the tensioning process, and the strain sensor collects the strain value in real time.

[0053] When the tension value is less than the preset tension threshold value, and the strain value drops to the first threshold value, the tensioning is stopped. The strain value is continuously collected in real time until the strain value rises to the second threshold value again within the time length set by the timer. The tensioning device is started again to tension the steel strand. During the tensioning process, the tension value and the strain value are collected. When the strain value drops to the first threshold value, the tensioning is stopped, and the cycle is repeated. During this process, the tension value is always less than the preset tension threshold value.

[0054] Generally, the tension value is always less than the preset tension threshold value, and the strain value cannot rise to the second threshold value again within the time length set by the timer, i.e., when the strain value changes little, the tensioning force is less than the designed prestress value. At this time, the tensioning device is started multiple times to tension the steel strand until the tension value reaches the preset tension threshold value, and the tensioning process ends. After the initial value of the tensioning device is determined, the subsequent control is controlled by the control system according to the information monitored by the sensor and the instruction. The judgment is accurate, and the human factor is less. Before the internal stress of the concrete is not enough to produce cracks, the tensioning process is effectively controlled before the cracks are produced, so as to ensure that the floor does not produce cracks. Then, grouting is carried out in the gap formed by the tensioning of the steel strand in the concrete base. The grouting concrete has a higher strength than the original poured concrete, so as to reduce the carbonization of the concrete, reduce the corrosion of the steel strand, and improve the strength and service life of the floor. Then, the tensioning device and the control box are removed, and the tensioning work is completed.

[0055] Of course, other conditions may also occur during the tensioning process.

[0056] For example, during the process of tensioning the steel strand by using the tensioning device, the internal stress of the concrete has not dropped to the first threshold value, and it is monitored that the tensioning force has reached the set tension threshold value, i.e., during the tensioning process, the tension value reaches the design value. At this time, the tensioning is stopped, and an alarm signal is issued. If the tensioning continues, the tension value will exceed the design value. For the actual tensioning tension value, it is usually possible that the design or construction deviates, and the construction process needs to be determined and communicated with the design party.

[0057] When the tension value is equal to the preset tension threshold value, the tensioning is stopped, and the timer is timed, and the strain value is continuously collected in real time.

[0058] If the strain value cannot rise to the second threshold value again within the time length set by the timer, the monitoring is stopped, i.e., the design value is consistent with the value when the tensioning is stopped.

[0059] If the strain value rises to the second threshold value again within the time length set by the timer, the tension value will certainly change from equal to the preset tension threshold value to greater than the preset tension threshold value. Therefore, in the subsequent cycle process, the tensioning is not stopped when the tension value is equal to the preset tension threshold value. Instead, the tensioning device is continuously started to tension the steel strand, the tension value is collected, the strain value is collected, and the alarm signal can be continuously sent out. In this tensioning, the tension value is greater than the preset tension threshold value, and the tensioning is stopped when the strain value drops to the first threshold value.

[0060] In the case where the tension value is greater than the preset tension threshold value, if the strain value cannot rise to the second threshold value again within the time length set by the timer, the monitoring is stopped. If the strain value rises to the second threshold value again within the time length set by the timer, the cycle is continued until the strain value cannot rise to the second threshold value again within the time length set by the timer, and the monitoring is stopped. Then, the gap formed by the tensioning of the steel strand in the concrete base is grouted. Subsequently, the tensioning device, the control box and the like are removed, and the tensioning work is completed.

[0061] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application. Therefore, equivalent changes made on the basis of the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A method for construction of a post-tensioned, pre-stressed, seamless concrete floor slab, comprising: Construction preparation step; Concrete pouring step; concrete curing step; prestressed tensioning step; characterized in that, In the construction preparation step, a strain sensing sensor is arranged; a steel strand with a protective sleeve is arranged; and a plurality of shrinkage bars are arranged at intervals within the floor area, the shrinkage bar is a sealed air bag structure, the structure of the shrinkage bar is an olive ball shape placed vertically, the distance from the top surface of the floor and the bottom surface of the floor in the vertical direction is 2-5mm, and the diameter of the middle part is 50mm; the shrinkage bar is vertically inserted into the concrete, one shrinkage bar is placed every 2 square meters to form a 2 square meter matrix structure distribution; In the concrete pouring step, the concrete uses early strength concrete, such as ordinary Portland cement concrete, with a cement content of 290-310 kg per cubic meter, and an additive is added to improve the early strength without significantly affecting the later strength; the strain sensing sensor is poured into the concrete; In the concrete curing step, a prestressed tensioning device is installed, and a tensioning force sensor is installed; the strain sensing sensor and the tensioning force sensor are connected to the control box, the strain sensing sensor uses a sensor with a wireless module to connect to the control box through a wireless communication module, so that the strain signal collected by the strain sensing sensor and the tension force signal collected by the tension force sensor are fed back to the control system of the control box, the control box is a PCL control box with a built-in control program; and the control system has a timer; the control system is also provided with an alarm, when the tension value is equal to or greater than the preset tension threshold, the alarm sends an alarm signal, which can be sent to the local alarm device or the external display control system; and the concrete is saturated and cured at the end of the curing time; In the prestressed tensioning step, When the floor first cracks, the strain sensing sensor real-time collects the strain value, and the strain value is set as the initial value of the starting tensioning device in the control system; a plurality of strain sensing sensors are arranged, the real-time collected strain values of the plurality of strain sensing sensors are read, the minimum value of the effective values is taken as the initial value of the starting tensioning device in the control system, and if there is an individual strain sensing sensor with a detection value deviating obviously and exceeding the allowed range, the value is discarded; According to the initial value of the starting tensioning device, a first threshold value for stopping tensioning of the tensioning device is set, and a second threshold value for restarting the tensioning device is set; the first threshold value is set to 40%-100% of the initial value of the starting tensioning device; the second threshold value is set to 80%-100% of the initial value of the starting tensioning device; and the first threshold value is less than the second threshold value; The counter of the control program also sets the cycle of adjacent monitoring, from the last time the tensioning is stopped to the next time the strain value rises to the second threshold value; After the strain sensing sensor real-time collects the strain value for the first time to reach the initial value of the starting tensioning device, the related parameters are set, the tensioning device is started to tension the steel strand, and the tension force sensor real-time collects the tension value, and the strain sensing sensor real-time collects the strain value. When the tension value is less than the preset tension threshold value, and the strain value drops to the first threshold value, the tensioning is stopped; the strain value is continuously collected in real time, until the strain value rises to the second threshold value again within the time length set by the timer, the tensioning device is started again to tension the steel strand, and the tension value and the strain value are collected during the tensioning process; when the strain value drops to the first threshold value, the tensioning is stopped, and the cycle is repeated; When the strain value cannot rise to the second threshold value again within the time length set by the timer, that is, when the strain value changes little, the tensioning force is less than the designed prestress value, the tensioning device is started multiple times to tension the steel strand, until the tension value reaches the preset tension threshold value, and the tensioning process is completed; And grouting is performed in the gap formed by tensioning the steel strand in the concrete, the grouting concrete has a strength higher than that of the original cast concrete; the tensioning device and the control box are removed.

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