Method for testing effective prestress under steel strand anchor after grouting

Abstract

The present invention discloses a method for detecting effective prestress under a steel strand anchor after grouting, and the method is applied to the grouting of a grouting channel where a prestressed steel strand (2) is located; it comprises the following steps: S1. Detecting the length dimension L of the free section of the prestressed steel strand (2) exposed outside the grouting body (10); S2. Extracting the target deformation variable △L and its corresponding back-pulling driving force F after the deformation variable undergoes the first jump; S3. Calculating the elastic deformation correction force Fx according to the length dimension L and the target deformation variable △L, Fx=△L / L*E*A, and calculating the effective prestress Fy under the steel strand anchor after grouting according to the elastic deformation correction force Fx and the back-pulling driving force F, Fy=F-Fx, A is the cross-sectional area of ​​the stress steel strand (2), and E is the elastic modulus of the prestressed steel strand (2). The method for detecting the effective prestress under the steel strand anchor is performed after grouting to achieve the technical problem of avoiding cross-interference between the detection construction and the engineering construction.

Description

Technical Field

[0001] The invention relates to the technical field of prestress detection, and in particular to a method for detecting effective prestress under a steel strand anchor after grouting. Background Art

[0002] Prestressed concrete is a concrete component that is mainly used in construction projects and bridge projects. Prestress is used to reduce or offset the tensile stress of concrete caused by load, thereby controlling the tensile stress of structural components within a smaller range, or even in a compressive state, to delay the appearance and development of concrete cracks, thereby improving the crack resistance and stiffness of the components.

[0003] Prestressed concrete is divided into pre-tensioned prestressed concrete and post-tensioned prestressed concrete. Figure 1 , Figure 2 The prestressed concrete 1 of the post-tensioned prestressed concrete includes a concrete body, a grouting channel located in the concrete body, a prestressed steel strand 2 located in the grouting channel, anchors 3 fixed on both sides of the concrete body, and both ends of the prestressed steel strand 2 are clamped by anchor clips 4 in the anchors 3.

[0004] The construction sequence of post-tensioned prestressed concrete is: pouring to form a concrete body, inserting prestressed steel strand 2 into the grouting hole reserved in the concrete body, fixing the two ends of the prestressed steel strand 2 with anchors 3, applying tension to the prestressed steel strand 2 with jacks on both sides at the same time, so that the prestressed steel strand 2 is prestressed, and then grouting is performed in the grouting hole, and the grouting body formed by the grouting locks the prestressed steel strand.

[0005] In order to detect whether qualified prestressing force is applied during the construction process, it is generally carried out before grouting when the prestressed steel strand 2 is in a free state as a whole. The method adopted is the reverse pulling method. For example, patent application 201811646344.4 discloses that before grouting, when the prestressed steel strand 2 is not locked by the grouting body 10, the length of the free section of the prestressed steel strand 2 is 10m. Under the reverse pulling method, the pull-out displacement of the prestressed steel strand 2 is △L. According to the formula Fs=△L / L*E*A, △L=0.5mm-2.5mm, L is 10m=10000mm, and E is 195000N / mm 2 , take A as 140mm 2 At this time, Fs is 1.365KN-6.825KN, and Fs is the influence of displacement on prestress. Therefore, it can be concluded that when the free section is long, that is, when L is long, Fs can be ignored, and the counter-tension force can be directly taken as the effective prestress under the strand anchor. Refer to the patent, which proposes that the counter-tension force F when the displacement S is stabilized at a constant value is directly taken as the effective prestress value Fy under the anchor head.

[0006] That is to say, patent application 201811646344.4 proposes a method for detecting the effective prestress under the steel strand anchor before grouting.

[0007] Generally speaking, in the art, since the prestressed steel strand 2 is locked by the grouting body 10 after grouting, it is impossible to use the reverse pulling method to detect the prestress. Figure 2 Generally, the grouting holes are filled with full grouting materials according to the specifications. Therefore, theoretically, the prestressed steel strands 2 inside are completely locked by the grouting body 10. At this time, it is impossible to detect the effective prestress under the anchor. Therefore, the existing prestress detection methods are required to be completed before grouting. In addition, the existing prestress detection methods are relatively cumbersome. Therefore, in many projects, most of them use supervision management during prestressing to ensure the quality of the project, and often no prestress detection is carried out or grouting is carried out after partial sampling and passing.

[0008] That is to say, the existing method of prestressing detection before grouting is very unfriendly to engineering construction and requires a lot of construction time.

[0009] Therefore, there is an urgent need for a method to detect the effective prestress under the steel strand anchor by moving the detection timing to after the grouting construction is completed, so as to achieve better time efficiency of the engineering construction while realizing quality inspection, so as to achieve the technical problem of avoiding cross interference between the inspection construction and the engineering construction. Summary of the invention

[0010] The purpose of the present invention is to provide a method for detecting the effective prestress under the steel strand anchor after grouting, so as to achieve the technical problem of avoiding cross interference between detection construction and engineering construction.

[0011] In order to detect the effective prestress under the steel strand anchor after grouting, the present invention proposes: using the size of the inherent grouting defects in the post-tensioning prestressed concrete process to calibrate as the free section size of the prestressed steel strand, using the back-tension method to detect the equilibrium state to obtain the back-tension driving force, using the free section size to calculate the elastic deformation correction force of the free section and correct the back-tension driving force, and finally obtaining the effective prestress under the steel strand anchor.

[0012] In order to solve the above technical problems, the present invention adopts the following solutions:

[0013] A method for detecting effective prestress under a steel strand anchor after grouting, the method acts on prestressed concrete, the prestressed concrete comprises a concrete body, a grouting hole located in the concrete body, a prestressed steel strand located in the grouting hole, anchors fixed on both sides of the concrete body, and both ends of the prestressed steel strand are clamped by anchor clips in the anchor; the method is applied after grouting of the grouting hole where the prestressed steel strand is located; and comprises the following steps:

[0014] S1. After the grouting hole where the prestressed steel strand is located is grouted to form a grouting body, the length L of the free section of the prestressed steel strand exposed outside the grouting body is detected;

[0015] S2. After the grouting hole where the prestressed steel strand is located is grouted to form a grouting body, a gradually increasing reverse tensile driving force is applied to the prestressed steel strand from the inside of the prestressed concrete to the outside, and the deformation of the prestressed steel strand and its corresponding reverse tensile driving force are recorded. The target deformation variable △L and its corresponding reverse tensile driving force F after the first jump of the deformation variable are extracted. The first jump of the deformation variable is qualitatively defined as a controllable elastic deformation jump of the free section of the prestressed steel strand exposed outside the grouting body;

[0016] S3. Calculate the elastic deformation correction force Fx according to the length dimension L and the target deformation variable △L, Fx = △L / L*E*A; calculate the effective prestress Fy under the steel strand anchor after grouting according to the elastic deformation correction force Fx and the anti-tension driving force F, Fy = F-Fx, A is the cross-sectional area of ​​the stressed steel strand, and E is the elastic modulus of the prestressed steel strand.

[0017] The design principle of the present invention is:

[0018] See attached Figure 2 In theoretical engineering, the grouting holes are generally filled with grouting materials in accordance with the specifications. Therefore, theoretically, the prestressed steel strands inside are completely locked by the grouting body. Therefore, in this field, it is generally believed that after grouting, it is impossible to detect the effective prestress under the anchor.

[0019] See also Figure 3 Since prestressed concrete has an arched characteristic, after grouting, the areas at both ends of the prestressed steel strands will form defects due to gravity. This defect is difficult to avoid. In the present invention, this defect is characterized as an inherent grouting defect in the post-tensioning prestressed concrete process. Therefore, in actual engineering, there are some sections at both ends of the prestressed steel strands that are not locked by the grouting body. Therefore, there is a possibility that the sections can be reverse-pulled to obtain prestress. The prestressed steel strand sections that are not locked by the grouting body are defined in the present invention as: the free sections of the prestressed steel strands exposed outside the grouting body.

[0020] See attached Figure 1 and patent application 201811646344.4, which is a test before grouting, and its free section is the entire prestressed steel strand. Therefore, under its system, it is observed that Fs = △L / L*E*A, and it can be seen that: since L is much larger than △L, Fs is small and does not affect the counter-tension.

[0021] See attached Figure 4 , Figure 5In the system of the present invention, the present invention is carried out after grouting. Most areas of the prestressed steel strands in the system are locked by the grouting body, and only the prestressed steel strands within the inherent grouting defects of the post-tensioning prestressed concrete process are in a free state. Therefore, L in Fs=△L / L*E*A is sharply reduced from a larger value in the prior art to a smaller value. Therefore, the reverse pulling driving force F applied to the system by the present invention needs to be corrected by adding Fs at this time, and the corrected result can be characterized as the effective prestress under the steel strand anchor.

[0022] Therefore, the technical principle of the present invention is: to apply a counter-tension to the free section of the prestressed steel strand exposed outside the grouting body due to defects in the grouting process, so as to obtain a counter-tension when the free section is deformed (the anchor clip is loose at this time) and the deformation is stabilized at a constant value. At this time, the whole system is in a state of equilibrium, and the counter-tension driving force F at this time is inversely equal to the sum of the effective prestress F under the steel strand anchor and the elongation load force of the free section exposed outside the grouting body (elastic deformation correction force Fx=Fs). In the present invention, considering that the free section outside the grouting body is small, the elongation load force of the free section exposed outside the grouting body is large at this time, and the influence on the counter-tension is large. Therefore, it is necessary to rely on the elongation load force of the free section exposed outside the grouting body as the elastic deformation correction force Fx, and use the elastic deformation correction force Fx to correct the counter-tension driving force F, and finally obtain the effective prestress Fy under the steel strand anchor after grouting.

[0023] It should be noted that:

[0024] In S2, the anti-pull driving force is directed from the inside of the prestressed concrete to the outside and gradually increases. In the process of gradual increase, the deformation of the prestressed steel strand will not change significantly or remain unchanged at the beginning. When F is greater than the sum of the effective prestress Fy under the steel strand anchor after grouting, the friction Fj between the anchor clip and the anchor, and the elongation load force Fx (elastic deformation correction force Fx) of the free section exposed outside the grouting body, the deformation of the prestressed steel strand will change significantly, which is regarded as the first jump of the deformation; this deformation can be monitored by displacement monitoring technology. After the first jump, the friction Fj disappears, so in order to maintain the deformation from increasing, it is necessary to control the anti-pull driving force to fall back. Therefore, the control system of the anti-pull driving force used in the present invention is a dynamic balance control system for maintaining the deformation. F in this equilibrium state is the required anti-pull driving force F, and the deformation in the equilibrium state is the required target deformation △L.

[0025] Therefore, the present invention uses the "defect", which is regarded as an unfavorable element in engineering, to reversely pull the prestressed steel strands in the defect, and uses the echo method to measure the defect and calibrate the free section to obtain the correction value, and then uses the reverse pulling balance system force to be corrected to obtain an effective prestress under the steel strand anchor that is closest to the actual value.

[0026] The method can provide an effective method for detecting the effective prestress under the steel strand anchor after grouting, and the method can avoid the problem of cross-interference with engineering construction.

[0027] Furthermore,

[0028] The specific process of detecting the length L of the free section of the prestressed steel strand exposed outside the grouting body is as follows:

[0029] After the grouting holes where the prestressed steel strands are located are grouted to form a grouting body, the grouting defect detection equipment is used to detect the grouting defects of the grouting holes where the prestressed steel strands are located, and the grouting defects adjacent to the anchors are selected from the grouting defects as the inherent grouting defects of the post-tensioned prestressed concrete process, and the length dimension L1 of the inherent grouting defects of the post-tensioned prestressed concrete process is obtained, and the length dimension L1 is regarded as the first free section of the prestressed steel strands;

[0030] Measure the length dimension L2 of the anchor clip located in the anchor, and regard the length dimension L2 as the second free section of the prestressed steel strand;

[0031] Measure the length dimension L3 of the prestressed steel strand located outside the anchor clip, and regard the length dimension L3 as the third free segment of the prestressed steel strand;

[0032] The length dimension L of the free section of the prestressed steel strand exposed outside the grouting body is: L1 or L1+L2 or L1+L2+L3.

[0033] Furthermore,

[0034] The specific process of applying a gradually increasing reverse pulling force from the inside of the prestressed concrete to the outside to the prestressed steel strand is as follows:

[0035] The anti-tension equipment is used to connect the part of the prestressed steel strand exposed outside the anchor clip, and a gradually increasing anti-tension driving force is applied to the prestressed steel strand from the inside of the prestressed concrete to the outside.

[0036] Furthermore,

[0037] The back-pull device is a back-pull device for controlling the back-pull driving force to stop increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0038] Furthermore,

[0039] The back-pull equipment includes: displacement measurement tooling, bridge pressure sensor, driving jack, displacement recorder, back-pull driving force recorder, and back-pull driving force controller;

[0040] The displacement measuring tool comprises a displacement measuring sleeve body, a displacement transmission mechanism arranged at an eccentric position of the displacement measuring sleeve body, and a displacement sensor sensing the displacement transmission mechanism;

[0041] The driving jack includes a jack static part and a jack action part;

[0042] The prestressed steel strand located outside the anchor clamp passes through the displacement measuring sleeve body, the bridge pressure sensor, the static part of the jack, and the action part of the jack;

[0043] One end of the displacement measuring sleeve body is pressed against the outer side of the anchor, and initially, the displacement transmission mechanism is in contact with the anchor clip; the other end of the displacement measuring sleeve body, the bridge pressure sensor, the static part of the jack, and the jack action part are coaxially connected in sequence, the jack action part clamps the prestressed steel strand, and the jack action part, driven by the static part of the jack, applies a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside;

[0044] The displacement recorder is connected to the displacement sensor and records the displacement value, which is regarded as the deformation of the prestressed steel strand;

[0045] The back-pulling driving force recorder is connected to the bridge pressure sensor and records the pressure value, which is regarded as the back-pulling driving force corresponding to the deformation of the prestressed steel strand;

[0046] The anti-pull driving force controller controls the static part of the jack to apply a gradually increasing anti-pull driving force from the inside of the prestressed concrete to the outside to the action part of the jack;

[0047] The reverse pulling driving force controller stops increasing the reverse pulling driving force when the reverse pulling driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0048] Furthermore,

[0049] The back-pull equipment includes: extended steel strand, connector, displacement measuring tool, bridge pressure sensor, driving jack, displacement recorder, back-pull driving force recorder, and back-pull driving force controller;

[0050] The displacement measuring tool comprises a displacement measuring sleeve body, a displacement transmission mechanism arranged at an eccentric position of the displacement measuring sleeve body, and a displacement sensor sensing the displacement transmission mechanism;

[0051] The driving jack includes a jack static part and a jack action part;

[0052] The connector includes a connector outer sealing body and a connection block. The prestressed steel strand located outside the anchor clip is inserted into the connection block, and one end of the extended steel strand is inserted into the connection block. One end of the connector outer sealing body is pressed against the outer side surface of the anchor. The connection block is movably arranged inside the connector outer sealing body. The other end of the connector outer sealing body is pressed against by the displacement measuring sleeve body. Initially, the displacement transmission mechanism is in contact with the connection block.

[0053] The other end of the displacement measuring sleeve body, the bridge pressure sensor, the static part of the jack, and the jack action part are coaxially connected in sequence, and the extended steel strand passes through the displacement measuring sleeve body, the bridge pressure sensor, the static part of the jack, and the jack action part in sequence. The jack action part clamps the extended steel strand, and the jack action part, driven by the static part of the jack, applies a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside;

[0054] The displacement recorder is connected to the displacement sensor and records the displacement value, which is regarded as the deformation of the prestressed steel strand;

[0055] The back-pulling driving force recorder is connected to the bridge pressure sensor and records the pressure value, which is regarded as the back-pulling driving force corresponding to the deformation of the prestressed steel strand;

[0056] The anti-pull driving force controller controls the static part of the jack to apply a gradually increasing anti-pull driving force from the inside of the prestressed concrete to the outside to the action part of the jack;

[0057] The reverse pulling driving force controller stops increasing the reverse pulling driving force when the reverse pulling driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0058] Furthermore,

[0059] The connecting block includes: a stud bolt, a left sleeve, a left clip, a right sleeve, and a right clip. The left clip is arranged in the left sleeve, and the right clip is arranged in the right sleeve. The prestressed steel strand located outside the anchor clip is inserted into the left clip, and one end of the extended steel strand is inserted into the right clip. Both ends of the stud bolt are respectively inserted into the left sleeve and the right sleeve.

[0060] Furthermore,

[0061] The specific process of using grouting defect detection equipment to detect grouting defects in the grouting holes where the prestressed steel strands are located is as follows: points are arranged along the survey line on the top plate or bottom plate corresponding to the grouting holes where the prestressed steel strands are located, and the impact echo method is used to collect data on the survey line and analyze the grouting defects of the grouting holes.

[0062] Furthermore,

[0063] The target deformation variable △L is set to increase as the length dimension L of the free section of the stress steel strand exposed outside the grouting body increases.

[0064] Furthermore,

[0065] The target deformation variable △L is set to 1mm-2mm.

[0066] The invention has the beneficial effects that the invention provides a method for effectively detecting the effective prestress under the steel strand anchor after grouting, and the method can avoid the problem of cross-interference with engineering construction. BRIEF DESCRIPTION OF THE DRAWINGS

[0067] Figure 1 This is a schematic diagram of the effective prestressing test using the reverse tension method before grouting.

[0068] Figure 2 Schematic diagram of prestressed concrete structure in theoretical state.

[0069] Figure 3 Schematic diagram of the actual prestressed concrete structure.

[0070] Figure 4 It is a schematic diagram of the initial state of the effective prestress detection by the reverse tension method after grouting according to the present invention.

[0071] Figure 5 It is a schematic diagram of the equilibrium state of the effective prestress detection by the reverse tension method after grouting of the present invention.

[0072] Figure 6 Schematic diagram of the control system of the present invention.

[0073] Figure 7 It is a schematic diagram of the process of the present invention.

[0074] Figure 8 It is a schematic diagram of the relationship between the anti-tension driving force and the deformation variable after the deformation variable reaches the target deformation variable and is in a balanced state.

[0075] The description of the accompanying drawings is as follows: 1. prestressed concrete, 2. prestressed steel strand, 3. anchor, 4. anchor clip, 5. displacement measuring tool, 6. displacement transmission mechanism, 7. displacement sensor, 8. static part of jack, 9. operating part of jack, 10. grouting body, 11. extended steel strand, 12. connector outer sealing body, 13. stud bolt, 14. left sleeve, 15. left clip, 16. right sleeve, 17. right clip, 18. Inherent grouting defects of post-tensioned prestressed concrete process. DETAILED DESCRIPTION

[0076] The present invention will be further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0077] Example 1

[0078] See also Figures 1 to 8 :

[0079] The method for detecting the effective prestress under the steel strand anchor after grouting of the present invention acts on the prestressed concrete 1, see the attached Figure 4 The prestressed concrete 1 comprises a concrete body, a grouting hole in the concrete body, a prestressed steel strand 2 in the grouting hole, anchors 3 fixed on both sides of the concrete body, and both ends of the prestressed steel strand 2 are clamped by anchor clips 4 in the anchors 3; the method is applied after the grouting hole where the prestressed steel strand 2 is located is grouted; see Figure 7 , including the following steps:

[0080] S1. After the grouting duct where the prestressed steel strand 2 is located is grouted to form a grouting body 10, the length dimension L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is detected;

[0081] S2. After the grouting hole where the prestressed steel strand 2 is located is grouted to form a grouting body 10, a gradually increasing reverse tensile driving force is applied to the prestressed steel strand 2 from the inside of the prestressed concrete to the outside, and the deformation of the prestressed steel strand 2 and its corresponding reverse tensile driving force are recorded, and the target deformation △L and its corresponding reverse tensile driving force F after the deformation occurs for the first time jump are extracted. The first jump in the deformation is qualitatively determined as a controllable elastic deformation jump of the free section of the prestressed steel strand 2 exposed outside the grouting body 10;

[0082] S3. Calculate the elastic deformation correction force Fx according to the length dimension L and the target deformation variable △L, Fx = △L / L*E*A; calculate the effective prestress Fy under the steel strand anchor after grouting according to the elastic deformation correction force Fx and the anti-tension driving force F, Fy = F-Fx, A is the cross-sectional area of ​​the stressed steel strand 2, and E is the elastic modulus of the prestressed steel strand 2.

[0083] See also Figure 8 The present invention adopts the back-pull method to pull the prestressed steel strand 2 outward. In order to avoid damage to the prestressed steel strand 2, when the back-pull driving force is applied to the prestressed steel strand 2, the back-pull driving force is gradually increased. Since there is an anchor clip 4 in this system, if the anchor clip 4 is pulled, it indicates that the back-pull driving force is greater than the effective prestress under the steel strand anchor. At this time, the deformation of the prestressed steel strand 2 will undergo the first jump phenomenon. If the back-pull driving force continues to increase, it is easy to damage the prestressed steel strand. Therefore, it is necessary to set a target deformation variable △L. After the target deformation variable △L is detected, the back-pull driving force stops increasing or starts self-feedback balance, that is, a back-pull driving force is output with the target deformation variable △L as the goal. The back-pull driving force at this time is the back-pull driving force F sought by the present invention, see the attached Figure 8The figure shows that the deformation variable maintains a stable value after the first jump, that is, the target deformation variable △L in the figure. The figure also shows that the anti-tension driving force falls from a high position and then remains at a stable value. This stable value is the anti-tension driving force F. The present invention uses the anti-tension balance method to find an anti-tension driving force F, which is corrected and then used as the effective prestress Fy under the steel strand anchor after grouting.

[0084] The design principle of the present invention is:

[0085] See attached Figure 2 In theoretical engineering, the grouting holes are generally filled with grouting materials according to the specifications. Therefore, theoretically, the prestressed steel strands 2 inside are completely locked by the grouting body 10. Therefore, in this field, it is generally believed that after grouting, it is impossible to detect the effective prestress under the anchor.

[0086] See also Figure 3 Since prestressed concrete has an arched characteristic, after grouting, the areas at both ends of the prestressed steel strand 2 will form defects due to gravity. This defect is difficult to avoid. In the present invention, this defect is characterized as: the inherent grouting defect 18 of the post-tensioning prestressed concrete process. Therefore, in actual engineering, there are some sections at both ends of the prestressed steel strand 2 that are not locked by the grouting body 10. Therefore, this section may be tested by back-pulling to obtain prestress. The section of the prestressed steel strand 2 that is not locked by the grouting body 10 is defined in the present invention as: the free section of the prestressed steel strand 2 exposed outside the grouting body 10.

[0087] See attached Figure 1 and patent application 201811646344.4, which is a detection before grouting, and its free section is the entire prestressed steel strand 2. Therefore, under its system, it is observed that Fs=△L / L*E*A. It can be seen that: since L is much larger than △L, Fs is small and does not affect the counter-tension. Therefore, this prior art does not use Fs, but directly uses the count of the bridge pressure sensor as the effective prestress Fy under the anchor.

[0088] See attached Figure 3 , Figure 4 , Figure 5 In the system of the present invention, the present invention is carried out after grouting. Most areas of the prestressed steel strands 2 in the system are locked by the grouting body 10, and only the prestressed steel strands 2 within the inherent grouting defects 18 of the post-tensioning prestressed concrete process are in a free state. Therefore, L in Fs=△L / L*E*A is sharply reduced from a larger value in the prior art to a smaller value. Therefore, the reverse pulling driving force F applied to the system by the present invention needs to be corrected by adding Fs at this time, and the corrected result can be characterized as the effective prestress under the steel strand anchor.

[0089] Therefore, the technical principle of the present invention is: to apply a back-pull force to the free section of the prestressed steel strand 2 exposed outside the grouting body 10 due to defects in the grouting process, so as to obtain a back-pull force when the free section is deformed (the anchor clip 4 is loose at this time) and the deformation is stabilized at a constant value. At this time, the whole system is in a state of equilibrium, and the back-pull driving force F at this time is inversely equal to the sum of the effective prestress F under the steel strand anchor and the elongation load force of the free section exposed outside the grouting body 10 (elastic deformation correction force Fx=Fs). In the present invention, considering that the free section outside the grouting body 10 is small, the elongation load force of the free section exposed outside the grouting body 10 at this time is large, and the influence on the back-pull force is large. Therefore, it is necessary to rely on the elongation load force of the free section exposed outside the grouting body 10 as the elastic deformation correction force Fx, and use the elastic deformation correction force Fx to correct the back-pull driving force F, and finally obtain the effective prestress Fy under the steel strand anchor after grouting.

[0090] It should be noted that:

[0091] In S2, the anti-pull driving force is directed from the inside of the prestressed concrete to the outside and gradually increases. In the process of gradual increase, the deformation of the prestressed steel strand 2 will not change significantly or remain unchanged at the beginning. When F is greater than the sum of the effective prestress Fy under the steel strand anchor after grouting, the friction Fj between the anchor clip 4 and the anchor, and the elongation load force Fx (elastic deformation correction force Fx) of the free section exposed outside the grouting body 10, the deformation of the prestressed steel strand 2 will change significantly, which is regarded as the first jump of the deformation; this deformation can be monitored by displacement monitoring technology. After the first jump, the friction Fj disappears, so in order to maintain the deformation from increasing, it is necessary to control the anti-pull driving force to fall back. Therefore, the control system of the anti-pull driving force used in the present invention is a dynamic balance control system for maintaining the deformation. F in this equilibrium state is the required anti-pull driving force F, and the deformation in the equilibrium state is the required target deformation △L.

[0092] Therefore, the present invention uses the "defect", which is regarded as an unfavorable element in engineering, to reversely pull the prestressed steel strand 2 in the defect, and uses the echo method to measure the defect and calibrate the free section to obtain the correction value, and then uses the reverse pulling balance system force to be corrected to obtain an effective prestress under the steel strand anchor that is closest to the actual value.

[0093] The method can provide an effective method for detecting the effective prestress under the steel strand anchor after grouting, and the method can avoid the problem of cross-interference with engineering construction.

[0094] Example 2

[0095] On the basis of the above-mentioned embodiment 1, the specific process of detecting the length dimension L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is as follows:

[0096] After the grouting hole where the prestressed steel strand 2 is located is grouted to form a grouting body 10, a grouting defect detection device is used to perform grouting defect detection on the grouting hole where the prestressed steel strand 2 is located, and the grouting defect adjacent to the anchor 3 is selected from the grouting defects as an inherent grouting defect 18 of the post-tensioned prestressed concrete process, and the length dimension L1 of the inherent grouting defect 18 of the post-tensioned prestressed concrete process is obtained, and the length dimension L1 is regarded as the first free section of the prestressed steel strand 2;

[0097] Measure the length dimension L2 of the anchor clip 4 in the anchor, and regard the length dimension L2 as the second free section of the prestressed steel strand 2;

[0098] Measure the length dimension L3 of the prestressed steel strand 2 located outside the anchor clip 4, and regard the length dimension L3 as the third free segment of the prestressed steel strand 2;

[0099] The length L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is: L1 or L1+L2 or L1+L2+L3.

[0100] It should be noted that:

[0101] See the attached Figure 4 , in the attached Figure 4 In the system of the attached figure, the prestressed steel strand 2 in the inherent grouting defect 18 of the post-tensioning prestressed concrete process has prestress, the prestressed steel strand 2 clamped by the anchor clip 4 has prestress, and the prestressed steel strand 2 outside the anchor clip 4 has no prestress. At the same time, in this system, since the prestressed steel strand 2 outside the anchor clip 4 is cut off and is shorter at this time, in order to facilitate the application of the reverse tension, it is necessary to design a connector to connect an extended steel strand to facilitate the reverse tension equipment to load the reverse tension, see the attached figure. Figure 4 , this figure shows a prestressed steel strand 2 with an extended steel strand and its matching anti-pull equipment. At this time, the prestressed steel strand 2 outside the anchor clip 4 is clamped and has no deformation characteristics. Therefore, in this figure, L1 and L2 are marked. The length L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is L1+L2; that is, due to the attachment Figure 4 A connector is used to connect the exposed sections of the prestressed steel strand 2 outside the anchor clip 4, so the section L3 does not participate in L.

[0102] In addition, when the anchor clip 4 is shorter, that is, in some small prestressed concretes, the anchor clip 4 is smaller and can be ignored, so the length dimension L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is L1.

[0103] In addition, when a connector is not used to clamp the prestressed steel strand 2 outside the anchor clip 4, but an extended steel strand is connected by welding, or the extended steel strand itself is not cut off and is sufficient to apply the reverse tension, L3 needs to be considered in the calculation. At this time, the length L of the free section of the prestressed steel strand 2 exposed outside the grouting body 10 is L1+L2+L3.

[0104] Example 3

[0105] Based on the above embodiments, see the attached Figure 4 , 5 The specific process of applying a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside to the prestressed steel strand 2 is as follows:

[0106] The back-pulling equipment is used to connect the part of the prestressed steel strand 2 exposed outside the anchor clip 4, and a gradually increasing back-pulling driving force is applied to the prestressed steel strand 2 from the inside of the prestressed concrete to the outside.

[0107] Furthermore,

[0108] The back-pull device is a back-pull device for controlling the back-pull driving force to stop increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0109] Furthermore,

[0110] The back-pull equipment includes: displacement measuring tool 5, bridge pressure sensor, driving jack, displacement recorder, back-pull driving force recorder, and back-pull driving force controller;

[0111] The displacement measuring tool 5 comprises a displacement measuring sleeve body, a displacement transmission mechanism 6 arranged at an eccentric position of the displacement measuring sleeve body, and a displacement sensor 7 sensing the displacement transmission mechanism 6;

[0112] The driving jack includes a jack static part 8 and a jack action part 9;

[0113] The prestressed steel strand 2 located outside the anchor clip 4 passes through the displacement measuring sleeve body, the bridge pressure sensor, the jack static part 8, and the jack action part 9;

[0114] One end of the displacement measuring sleeve body is pressed against the outer side of the anchor, and initially, the displacement transmission mechanism 6 is in contact with the anchor clip 4; the other end of the displacement measuring sleeve body, the bridge pressure sensor, the jack static part 8, and the jack action part 9 are coaxially connected in sequence, and the jack action part 9 clamps the prestressed steel strand 2. Under the drive of the jack static part 8, the jack action part 9 applies a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside;

[0115] like Figure 6 As shown,

[0116] The displacement recorder is connected to the displacement sensor 7 and records the displacement value, which is regarded as the deformation amount of the prestressed steel strand 2;

[0117] The anti-pull driving force recorder is connected to the bridge pressure sensor and records the pressure value, and the pressure value is regarded as the anti-pull driving force corresponding to the deformation amount of the prestressed steel strand 2;

[0118] The anti-pull driving force controller controls the static part 8 of the jack to apply a gradually increasing anti-pull driving force from the inside of the prestressed concrete to the outside to the action part 9 of the jack;

[0119] The back-pull driving force controller stops increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0120] Example 4

[0121] Based on the above embodiments, see the attached Figure 4 , 5 The specific process of applying a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside to the prestressed steel strand 2 is as follows:

[0122] The back-pulling equipment is used to connect the part of the prestressed steel strand 2 exposed outside the anchor clip 4, and a gradually increasing back-pulling driving force is applied to the prestressed steel strand 2 from the inside of the prestressed concrete to the outside.

[0123] Furthermore,

[0124] The back-pull device is a back-pull device for controlling the back-pull driving force to stop increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0125] The back-pull equipment includes: extended steel strand 11, connector, displacement measuring tool 5, bridge pressure sensor, driving jack, displacement recorder, back-pull driving force recorder, and back-pull driving force controller;

[0126] The displacement measuring tool 5 comprises a displacement measuring sleeve body, a displacement transmission mechanism 6 arranged at an eccentric position of the displacement measuring sleeve body, and a displacement sensor 7 sensing the displacement transmission mechanism 6;

[0127] The driving jack includes a jack static part 8 and a jack action part 9;

[0128] The connector includes a connector outer sealing body 12 and a connecting block. The prestressed steel strand 2 located outside the anchor clip 4 is inserted into the connecting block, and one end of the extended steel strand 11 is inserted into the connecting block. One end of the connector outer sealing body 12 is pressed against the outer side surface of the anchor. The connecting block is movably arranged inside the connector outer sealing body 12. The other end of the connector outer sealing body 12 is pressed against by the displacement measuring sleeve body. Initially, the displacement transmission mechanism 6 is in contact with the connecting block.

[0129] The other end of the displacement measuring sleeve body, the bridge pressure sensor, the jack static part 8, and the jack action part 9 are coaxially connected in sequence, and the extended steel strand 11 passes through the displacement measuring sleeve body, the bridge pressure sensor, the jack static part 8, and the jack action part 9 in sequence. The jack action part 9 clamps the extended steel strand 11, and the jack action part 9, driven by the jack static part 8, applies a gradually increasing reverse pulling driving force from the inside of the prestressed concrete to the outside;

[0130] like Figure 6 As shown,

[0131] The displacement recorder is connected to the displacement sensor 7 and records the displacement value, which is regarded as the deformation amount of the prestressed steel strand 2;

[0132] The anti-pull driving force recorder is connected to the bridge pressure sensor and records the pressure value, and the pressure value is regarded as the anti-pull driving force corresponding to the deformation amount of the prestressed steel strand 2;

[0133] The anti-pull driving force controller controls the static part 8 of the jack to apply a gradually increasing anti-pull driving force from the inside of the prestressed concrete to the outside to the action part 9 of the jack;

[0134] The reverse pulling driving force controller stops increasing the reverse pulling driving force when the reverse pulling driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

[0135] The static part 8 of the jack includes an oil pump and a jack pressure body.

[0136] Among them, the back-pull driving force controller, the back-pull driving force recorder, and the displacement recorder can be the same execution subject or different execution subjects.

[0137] Furthermore,

[0138] The connecting block includes: a stud bolt 13, a left sleeve 14, a left clip 15, a right sleeve 16, and a right clip 17. The left clip 15 is arranged in the left sleeve 14, and the right clip 17 is arranged in the right sleeve 16. The prestressed steel strand 2 located outside the anchor clip 4 is inserted into the left clip 15, and one end of the extended steel strand 11 is inserted into the right clip 17. Both ends of the stud bolt 13 are respectively inserted into the left sleeve 14 and the right sleeve 16.

[0139] Some factors to consider in the above embodiment are:

[0140] The specific process of using grouting defect detection equipment to detect grouting defects in the grouting hole where the prestressed steel strand 2 is located is as follows: points are arranged along the survey line on the top plate or bottom plate corresponding to the grouting hole where the prestressed steel strand 2 is located, and the impact echo method is used to collect data on the survey line and analyze the grouting defects of the grouting hole.

[0141] The target deformation amount ΔL is set to increase as the length dimension L of the free section of the stress steel strand 2 exposed outside the grouting body 10 increases.

[0142] The target deformation variable △L is set to 1mm-2mm.

[0143] In addition, the purpose of the effective prestress under the anchor of the steel strand obtained by the present invention after grouting is to compare it with the design value of the effective prestress under the anchor under the current detection working condition, so as to evaluate whether the prestress of the prestressed steel strand meets the standard. The design value of the effective prestress under the anchor can be calculated according to the specification documents such as JTG 3362.

[0144] The present invention connects the cut prestressed steel strands to the extended steel strands through a connector into a whole, completely covers the connecting part (connector) of the steel strands through a connector outer sealing body, and provides a reverse pulling device to apply reverse pulling force.

[0145] The connector has a diameter of 49mm and a length of 194mm. It is made of stainless steel with an annealing hardness not greater than 235HB and can withstand a tensile force of not less than 200KN.

[0146] The displacement measuring fixture is longer than 200mm, with a diameter greater than 49mm, and is made of stainless steel with an annealing hardness no greater than 235HB. The overall tooling can withstand a pressure of no less than 250KN.

[0147] The oil pump and jack in the anti-tension equipment can exert a maximum tension of 250KN.

[0148] The method described in the present invention requires the cooperation of two sets of equipment. The first set of equipment is grouting defect detection equipment. Grouting defect detection equipment is a kind of equipment that uses the echo method to detect defects. This equipment is a prior art and will not be described in detail here. The defects inside the prestressed concrete can be obtained through this equipment. After the target defects are screened out, the length of the corresponding prestressed steel strand segment is calibrated according to the length of the target defect. The second set of equipment is the reverse pulling equipment, which has been described in detail in the present invention. It can adopt the existing reverse pulling equipment as cited in the background technology, or it can be formed by adding a connector on the basis of the prior art.

[0149] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. According to the technical essence of the present invention, within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement made to the above embodiment still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for detecting effective prestress under a steel strand anchor after grouting, characterized in that: The method acts on prestressed concrete (1), the prestressed concrete (1) comprising a concrete body, a grouting hole located in the concrete body, a prestressed steel strand (2) located in the grouting hole, anchors (3) fixed on both sides of the concrete body, and both ends of the prestressed steel strand (2) being clamped by anchor clips (4) in the anchors (3); the method is applied after grouting of the grouting hole where the prestressed steel strand (2) is located; and comprises the following steps: S1. After the grouting hole where the prestressed steel strand (2) is located is grouted to form a grouting body (10), the length dimension L of the free section of the prestressed steel strand (2) exposed outside the grouting body (10) is detected, and the free section of the prestressed steel strand (2) exposed outside the grouting body (10) includes the prestressed steel strand portion at the grouting defect; S2. After grouting the grouting hole where the prestressed steel strand (2) is located to form a grouting body (10), a gradually increasing reverse tensile driving force is applied to the prestressed steel strand (2) from the inside of the prestressed concrete to the outside, and the deformation of the prestressed steel strand (2) and its corresponding reverse tensile driving force are recorded. The target deformation △L and its corresponding reverse tensile driving force F after the deformation occurs for the first time jump are extracted. The first jump in the deformation is qualitatively determined as a controllable elastic deformation jump of the free section of the prestressed steel strand (2) exposed outside the grouting body (10); S3. Calculate the elastic deformation correction force Fx according to the length dimension L and the target deformation variable △L, Fx=△L / L*E*A. Calculate the effective prestress Fy under the steel strand anchor after grouting according to the elastic deformation correction force Fx and the anti-tension driving force F, Fy=F-Fx, A is the cross-sectional area of ​​the stress steel strand (2), and E is the elastic modulus of the prestressed steel strand (2).

2. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 1, characterized in that: The specific process of detecting the length dimension L of the free section of the prestressed steel strand (2) exposed outside the grouting body (10) is as follows: After grouting the grouting hole where the prestressed steel strand (2) is located to form a grouting body (10), a grouting defect detection device is used to perform grouting defect detection on the grouting hole where the prestressed steel strand (2) is located, and the grouting defect adjacent to the anchor (3) is selected from the grouting defects as an inherent grouting defect (18) of the post-tensioned prestressed concrete process, and the length dimension L1 of the inherent grouting defect (18) of the post-tensioned prestressed concrete process is obtained, and the length dimension L1 is regarded as the first free section of the prestressed steel strand (2); Measuring a length dimension L2 of the anchor clip (4) located in the anchor, and regarding the length dimension L2 as the second free section of the prestressed steel strand (2); Measuring the length dimension L3 of the prestressed steel strand (2) located outside the anchor clamp (4), and regarding the length dimension L3 as the third free section of the prestressed steel strand (2); The length dimension L of the free section of the prestressed steel strand (2) exposed outside the grouting body (10) is: L1 or L1+L2 or L1+L2+L3.

3. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 1, characterized in that: The specific process of applying a gradually increasing reverse tensile driving force directed from the inside of the prestressed concrete to the outside to the prestressed steel strand (2) is as follows: A reverse pulling device is used to connect the portion of the prestressed steel strand (2) exposed outside the anchor clamp (4), and a gradually increasing reverse pulling driving force directed from the inside of the prestressed concrete toward the outside is applied to the prestressed steel strand (2).

4. The method for detecting effective prestress under the anchor of a steel strand after grouting according to claim 3, characterized in that: The back-pull device is a back-pull device for controlling the back-pull driving force to stop increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

5. The method for detecting effective prestress under the anchor of a steel strand after grouting according to claim 3, characterized in that: The back-pull equipment includes: a displacement measuring tool (5), a bridge pressure sensor, a driving jack, a displacement recorder, a back-pull driving force recorder, and a back-pull driving force controller; The displacement measuring tool (5) comprises a displacement measuring sleeve body, a displacement transmission mechanism (6) disposed at an eccentric position of the displacement measuring sleeve body, and a displacement sensor (7) sensing the displacement transmission mechanism (6); The driving jack comprises a jack static part (8) and a jack action part (9); The prestressed steel strand (2) located outside the anchor clip (4) passes through the displacement measuring sleeve body, the bridge pressure sensor, the jack static part (8), and the jack action part (9); One end of the displacement measuring sleeve body is pressed against the outer side surface of the anchor, and initially, the displacement transmission mechanism (6) is in contact with the anchor clamp (4); the other end of the displacement measuring sleeve body, the bridge pressure sensor, the jack static part (8), and the jack action part (9) are coaxially connected in sequence, the jack action part (9) clamps the prestressed steel strand (2), and the jack action part (9) is driven by the jack static part (8) to apply a gradually increasing reverse pulling driving force directed from the inside of the prestressed concrete to the outside; The displacement recorder is connected to the displacement sensor (7) and records the displacement value, and the displacement value is regarded as the deformation amount of the prestressed steel strand (2); The anti-tension driving force recorder is connected to the bridge pressure sensor and records the pressure value, and the pressure value is regarded as the anti-tension driving force corresponding to the deformation amount of the prestressed steel strand (2); The anti-pull driving force controller controls the static part (8) of the jack to apply a gradually increasing anti-pull driving force directed from the inside of the prestressed concrete to the outside to the action part (9) of the jack; The back-pull driving force controller stops increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

6. The method for detecting effective prestress under the anchor of a steel strand after grouting according to claim 3, characterized in that: The back-pull equipment includes: an extended steel strand (11), a connector, a displacement measuring tool (5), a bridge pressure sensor, a driving jack, a displacement recorder, a back-pull driving force recorder, and a back-pull driving force controller; The displacement measuring tool (5) comprises a displacement measuring sleeve body, a displacement transmission mechanism (6) disposed at an eccentric position of the displacement measuring sleeve body, and a displacement sensor (7) sensing the displacement transmission mechanism (6); The driving jack comprises a jack static part (8) and a jack action part (9); The connector comprises a connector outer sealing body (12) and a connection block, wherein the prestressed steel strand (2) located outside the anchor clamp (4) is inserted into the connection block, and one end of the extended steel strand (11) is inserted into the connection block, one end of the connector outer sealing body (12) is pressed against the outer side surface of the anchor, the connection block is movably arranged inside the connector outer sealing body (12), and the other end of the connector outer sealing body (12) is pressed against by the displacement measuring sleeve body, and initially, the displacement transmission mechanism (6) is in contact with the connection block; The other end of the displacement measuring sleeve body, the bridge pressure sensor, the jack static part (8), and the jack action part (9) are coaxially connected in sequence, the extended steel strand (11) passes through the displacement measuring sleeve body, the bridge pressure sensor, the jack static part (8), and the jack action part (9) in sequence, the jack action part (9) clamps the extended steel strand (11), and the jack action part (9) applies a gradually increasing reverse pulling driving force directed from the inside of the prestressed concrete to the outside under the drive of the jack static part (8); The displacement recorder is connected to the displacement sensor (7) and records the displacement value, and the displacement value is regarded as the deformation amount of the prestressed steel strand (2); The anti-tension driving force recorder is connected to the bridge pressure sensor and records the pressure value, and the pressure value is regarded as the anti-tension driving force corresponding to the deformation amount of the prestressed steel strand (2); The anti-pull driving force controller controls the static part (8) of the jack to apply a gradually increasing anti-pull driving force directed from the inside of the prestressed concrete to the outside to the action part (9) of the jack; The back-pull driving force controller stops increasing the back-pull driving force when the back-pull driving force exceeds the set driving force safety limit value or the displacement exceeds the set displacement safety limit value.

7. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 6, characterized in that: The connecting block comprises: a stud bolt (13), a left sleeve (14), a left clip (15), a right sleeve (16), and a right clip (17); the left clip (15) is arranged inside the left sleeve (14), and the right clip (17) is arranged inside the right sleeve (16); the prestressed steel strand (2) located outside the anchor clip (4) is inserted into the left clip (15), and one end of the extended steel strand (11) is inserted into the right clip (17); and both ends of the stud bolt (13) are respectively inserted into the left sleeve (14) and the right sleeve (16).

8. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 2, characterized in that: The specific process of using grouting defect detection equipment to detect grouting defects in the grouting hole where the prestressed steel strand (2) is located is as follows: points are arranged along the measuring line on the top plate or bottom plate corresponding to the grouting hole where the prestressed steel strand (2) is located, and the impact echo method is used to collect data on the measuring line and analyze the grouting defects of the grouting hole.

9. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 1, characterized in that: The target deformation variable ΔL is adjusted to increase as the length dimension L of the free section of the stress steel strand (2) exposed outside the grouting body (10) increases.

10. The method for detecting effective prestress under the steel strand anchor after grouting according to claim 1, characterized in that: The target deformation variable △L is set to 1mm-2mm.

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