CN115478569A - Prestressed non-destructive testing method based on natural frequency of precision-rolled rebar anti-floating anchor rod - Google Patents

Abstract

The invention belongs to the technical field of prestress detection of an anti-floating anchor rod, discloses a prestress nondestructive detection method based on the natural frequency of a finish-rolled deformed steel bar anti-floating anchor rod, and aims to solve the problem that the anti-floating anchor rod lacks a prestress detection method which is simple in operation and reliable in performance. The invention comprises the following steps: (1) The method comprises the steps of obtaining a first-order natural frequency of an exposed section steel bar of a finish-rolled deformed steel bar anti-floating anchor rod under the action of prestress in advance, and accordingly establishing a relation curve of a prestress value and the first-order natural frequency of the exposed section steel bar of the finish-rolled deformed steel bar anti-floating anchor rod; (2) Acquiring a first-order natural frequency of a steel bar of an exposed section of the finish-rolled deformed steel bar anti-floating anchor rod, which is subjected to prestressing force on site, by a detection system; (3) And (3) obtaining the prestress value of the steel bar at the exposed section of the finish-rolled deformed steel bar anti-floating anchor rod according to the relation curve between the prestress value and the first-order fixed frequency established in the step (1) and the first-order fixed frequency obtained in the step (2).

Description

Prestressed non-destructive testing method based on natural frequency of precision-rolled rebar anti-floating anchor rod

technical field

The invention belongs to the technical field of prestress detection of anti-floating anchor rods, and in particular relates to a prestress non-destructive detection method based on the natural frequency of fine-rolled threaded steel anti-floating anchor rods, which is used for prestressing the prestress of fine-rolled threaded steel anti-floating anchor rods. detection.

Background technique

With the development and utilization of underground space, the problem of anti-floating of underground space will follow. Anti-floating anchors are widely used in anti-floating in underground spaces, but the anti-floating anchors have poor durability and reduced reliability due to cracking of the grouting body in the anchorage section during service. In addition, with the implementation of the "Anti-floating Technical Standards for Construction Engineering" (JGJ476-2019) on March 1, 2020, more stringent requirements have been put forward for the durability of anti-floating anchors: projects with an anti-floating design grade of Class A, Tensile stress should not be generated in the anchoring slurry; for projects whose anti-floating design level is Class B, the tensile stress in the anchoring slurry should not exceed the axial tensile strength of the anchoring slurry; for projects with anti-floating design level of Class C, the anchorage The crack width of the slurry should not be greater than the maximum crack limit.

In order to control the cracks of the anti-floating anchor and solve the problem of poor durability of the anti-floating anchor, engineers and technicians apply prestress by tensioning the anchor reinforcement in the anti-floating anchor, that is, by applying prestress to the anti-floating anchor to To achieve the purpose of controlling the cracks of the anti-floating anchor rod and improving the durability.

Although applying prestress to the anti-floating anchor can control the cracks of the anti-floating anchor and improve durability, due to problems such as worker operation level, oil meter error, and installation of prestressed anchor pads, etc. The stress cannot reach the design value and the prestress loss; even after the tension is completed for a short period of time, the prestressed steel bars produce a large prestress loss; thus the applied prestress cannot meet the design requirements and affect the durability of the anti-floating anchor.

Therefore, applying prestress accurately according to the design requirements has become a key link in the crack control of anti-floating anchor rods. However, there is currently a lack of detection methods for the prestress of anti-floating anchors, and it is impossible to evaluate the prestressing effect and prestress loss of anti-floating anchors.

At present, the prestress detection methods for other prestressed structures such as prestressed concrete continuous (steel structure) box girder bridge webs include oil meter conversion method, pressure sensor method, strain gauge test method, magnetic flux detection method, and shrinkage detection method , Ultrasonic stress detection method. However, these methods have deficiencies. For example, the oil pressure gauge conversion method is only suitable for the construction unit to control its stress during tension, and is not suitable for subsequent detection and spot checks; the pressure sensor test method is expensive to purchase and is not suitable for engineering practice; The test method has a long test cycle, and the strain gauge is easy to peel off and fail; the current technology of the magnetic flux detection method is not yet mature, so the reliability of the test results of this method has yet to be verified; There is still a certain safety risk in the measurement; the energy loss of the ultrasonic stress detection method is fast and the error is large. Therefore, it is difficult to apply to prestressed anti-floating anchor structures by modifying the prestress detection methods of other existing prestressed structures.

Contents of the invention

In order to solve the problem that the anti-floating anchor lacks a prestressed detection method with simple operation and reliable performance, the present invention provides a prestressed non-destructive detection method based on the natural frequency of the precision-rolled rebar anti-floating anchor, which can quickly and reliably The prestress detection of the anti-floating anchor rod is completed, which fills the gap in the prestress detection of the anti-floating anchor rod.

For solving technical problems, the technical solution adopted in the present invention is:

A prestressed non-destructive testing method based on the natural frequency of a precision-rolled rebar anti-floating anchor rod, characterized in that it includes:

(1) Pre-acquire the first-order natural frequency (referred to as the fundamental frequency) of the exposed section steel bar of the finished rolled rebar anti-floating anchor under the prestressing effect, so as to establish the prestress of the exposed section steel bar of the finished rolled rebar anti-floating anchor The relationship between the value and the first-order natural frequency;

(2) Obtain the first-order natural frequency of the steel bars in the exposed section of the anti-floating anchor rod of the finished rolled rebar that has been prestressed on site through the detection system;

(3) According to the relationship curve between the prestress value and the first-order fixed frequency established in step (1) and the first-order fixed frequency obtained in step (2), the prestress of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod is obtained value.

In some embodiments, in the step (1), the detection system is used to obtain the first-order fixed frequency of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod under the action of prestress.

In some embodiments, the detection system includes a first acceleration sensor and a second acceleration sensor, the first acceleration sensor is installed on the upper end of the steel bar of the exposed section of the finished rolled rebar anti-floating anchor rod, and the second acceleration sensor is installed In the lower section of the steel bar of the exposed section of the finished-rolled rebar anti-floating anchor rod, the upper end of the first acceleration sensor is flush with the upper end surface of the steel bar of the exposed section of the finished-rolled rebar anti-floating anchor rod, and the lower end surface of the second acceleration sensor The first acceleration sensor and the second acceleration sensor are both electrically connected to the signal collector.

In some embodiments, the first acceleration sensor is used for monitoring the acceleration time-history curve of the steel bar input in the exposed section of the finished-rolled rebar anti-floating anchor rod, and the second acceleration sensor is used for monitoring the finished-rolled rebar anti-floating anchor rod The acceleration time-history curve of the steel bar response in the exposed section; the signal collector is used to perform time-frequency analysis on the received signal so as to obtain the acceleration excellent frequency f1 corresponding to the first acceleration sensor and the acceleration excellent frequency f2 corresponding to the second acceleration sensor, the acceleration Divide the excellent frequency f2 by the acceleration excellent frequency f1 to obtain the first-order natural frequency of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod.

In some embodiments, the prestress value P of the exposed steel bar of the finished rolled rebar anti-floating anchor rod is obtained by the following formula:

Among them, f is the first-order natural frequency of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod, R is the average value of the diameter of the anchor head and the diameter of the finished-rolled rebar, M is the mass of the anchor head, and L is the anti-floating rebar of the finished-rolled rebar. The length of the steel bar in the exposed section of the floating anchor, ρ is the linear density of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor, and a and b are the experimental parameters.

In some embodiments, experimental parameters a and b are obtained as follows:

When the finished-rolled rebar is stretched in stages, the first acceleration sensor, the second acceleration sensor and the signal collector are used to obtain a part of the steel bar of the exposed section of the anti-floating anchor rod of the finished-rolled rebar under the load. The first-order natural frequency f, and then the prestress value P applied to the anti-floating anchor rod of fine-rolled rebar steel is obtained through the through-hole pressure sensor; f and P values; finally, curve fitting is performed on multiple pairs of f and P values to obtain the values of a and b.

In some embodiments, when the finish-rolled rebar is stretched step by step, it should stand still for a certain period of time under each level of load.

Compared with the prior art, the present invention has the following beneficial effects:

The prestressed non-destructive detection method based on the natural frequency of the finished-rolled threaded steel anti-floating anchor rod of the present invention obtains in advance (acquired in the indoor laboratory) the first-order natural frequency and The relationship curve of prestress value. When the on-site construction is based on the fine-rolled rebar anti-floating anchor rod, the first-order rebar of the exposed section of the fine-rolled rebar anti-floating anchor rod can be obtained through the detection system (the first acceleration sensor, the second acceleration sensor and the signal collector). The natural frequency means that the prestress value of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod can be obtained through the pre-acquired relationship curve between the first-order natural frequency and the prestress value.

The present invention can obtain the prestress value of the steel bar in the exposed section of the finished-rolled threaded steel anti-floating anchor rod by obtaining the first-order natural frequency of the steel bar in the exposed section of the finished-rolled threaded steel anti-floating anchor rod, filling the gap of the prestressed anti-floating anchor rod Blank for prestress testing. Compared with the prior art using the strain gauge test method, it has the characteristics of short acquisition time of the prestress value, and avoids troublesome installation of the strain gauge, easy falling off, and failure problems. Compared with the prior art using the retraction amount detection method, it has the advantages of high precision and high operation safety. Compared with the prior art, the ultrasonic stress detection method has the characteristics of high precision.

When the present invention detects on site, it only needs to obtain the first-order natural frequency of the exposed section steel bar of the finished-rolled rebar anti-floating anchor rod through the detection system (i.e. the first acceleration sensor, the second acceleration sensor and the signal collector). It has the characteristics of fast detection speed, convenient on-site operation, stability and reliability, which greatly saves the time of anti-floating anchor prestress detection, so that the construction progress will not be affected by the prestress detection, and finally achieves the purpose of saving construction costs.

Moreover, the detection system of the present invention can be reused, greatly reducing the cost of prestress detection.

The present invention pre-acquires the relationship curve between the first-order natural frequency and the prestress value of the exposed steel bar of the finish-rolled rebar anti-floating anchor rod in the indoor laboratory, and only needs to calibrate one anti-floating anchor rod to obtain the whole batch. The relationship curve between the second first-order natural frequency and the prestress value further improves the detection speed of the anti-floating anchor bolt prestress. And the present invention can be carried out indoors (as the relationship curve between the first-order natural frequency and the size of the prestress value of the exposed section steel bar of the finish-rolled rebar anti-floating anchor bar obtained in the laboratory) and the on-site detection can be carried out simultaneously, without affecting the on-site prestress resistance. The detection progress of the floating anchor rod, and then achieve the purpose of improving the detection speed.

Description of drawings

Fig. 1 is the structural representation of an embodiment of finish-rolled rebar anti-floating anchor rod;

Fig. 2 is a schematic diagram of the local structure of the anti-floating anchor rod of finished rolled rebar before applying prestress;

Fig. 3 is the structural representation of the detection system of the present invention when detecting the anti-floating anchor rod of finish-rolled rebar that has been applied with prestress;

Fig. 4 is the structural representation when detection system of the present invention obtains the relation curve of the prestressed value and the first-order natural frequency of the exposed section steel bar of finish-rolled rebar anti-floating anchor in the room (or laboratory);

Fig. 5 is a schematic diagram of the relationship curve between the prestress value and the first-order natural frequency of the exposed section steel bar of the finish-rolled rebar anti-floating anchor rod obtained in advance by an embodiment of the present invention;

Marks in the figure: 1. Anchor hole, 2. Finished rebar, 3. Carrier, 4. Sleeve, 5. Cushion, 6. Prestressed backing plate, 7. Prestressed anchor head, 8. Supporting anchor plate , 9. Supporting anchor head, 10. Foundation or anti-water board, 11. First acceleration sensor, 12. Second acceleration sensor, 13. Signal collector, 14. Rubber hammer, 15. Jack and reaction force device, 16. Force transmission component, 17, through the heart type pressure sensor.

detailed description

The present invention will be further described below in conjunction with the embodiments, and the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other used embodiments obtained by persons of ordinary skill in the art without creative efforts all belong to the protection scope of the present invention.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer" etc. The indicated orientation or positional relationship is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, or in a specific orientation. construction and operation, and therefore cannot be construed as limiting the present invention; the terms "first", "second", and "third" are used for descriptive purposes only, and cannot be construed as indicating or implying relative importance; in addition, unless otherwise Clearly stipulated and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be a direct connection. connected, or indirectly through an intermediary. Those of ordinary skill in the art can understand the specific meanings of the above terms in the present invention in combination with specific situations.

In conjunction with accompanying drawing 1 and accompanying drawing 2, it is the structure schematic diagram of an embodiment of the finish-rolled threaded steel anti-floating anchor rod that the present invention tells about, and the finish-rolled threaded steel anti-floating anchor rod includes anchor hole 1, the precision anchor rod that is placed in anchor hole 1 Rolled rebar 2, the space between the anchor hole 1 and the finish-rolled rebar 2 is used to fill concrete, and the anchor body is formed after the concrete is solidified. The upper end of the upper end passes through the cushion layer 5 and is equipped with a prestressed anchor plate 6 and a prestressed anchor head 7, wherein the lower section of the finish-rolled rebar 2 is provided with a plurality of bearing bodies 3 at intervals, and the finish-rolled thread in the free section of the anchor hole A casing 4 is sheathed around the steel 2 . When the concrete of the finished-rolled rebar anti-floating anchor reaches a certain strength, it is necessary to apply prestress to the finish-rolled rebar 2. 2 for locking. After the prestressing of the finish-rolled rebar 2 is completed, the prestress value needs to be detected. If the prestress value meets the design requirements, the upper section of the finish-rolled rebar 2 is provided with a supporting anchor plate 8 and a supporting anchor head 9, and finally The supporting anchor plate 8 and the supporting anchor head 9 are pre-embedded in the pouring foundation or the water-resistant plate 10 .

Among them, the construction, prestressing and locking of the anti-floating anchor rod of the finished-rolled rebar all belong to the prior art, and those skilled in the art can understand and understand, and will not repeat them here.

In conjunction with accompanying drawing 1 to accompanying drawing 4, the prestressed non-destructive testing method based on the natural frequency of the finish-rolled rebar anti-floating anchor rod of the present invention includes:

(1) Pre-acquire the first-order natural frequency (referred to as the fundamental frequency) of the exposed section steel bar of the finished rolled rebar anti-floating anchor under the prestressing effect, so as to establish the prestress of the exposed section steel bar of the finished rolled rebar anti-floating anchor The relationship curve between the value and the first-order natural frequency; wherein, the exposed section steel bar described in the present invention refers to: the finish-rolled screw steel 2 above the prestressed anchor head 7.

(2) Obtain the first-order natural frequency of the steel bars in the exposed section of the anti-floating anchor rod of the finished rolled rebar that has been prestressed on site through the detection system;

(3) According to the relationship curve between the prestress value and the first-order fixed frequency established in step (1) and the first-order fixed frequency obtained in step (2), the prestress of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod is obtained value. Therefore, the prestress value of the anti-floating anchor rod of the finished-rolled screw steel can be quickly obtained.

The prestressed non-destructive detection method based on the natural frequency of the finished-rolled threaded steel anti-floating anchor rod of the present invention obtains in advance (acquired in the indoor laboratory) the first-order natural frequency and The relationship curve of prestress value. When the on-site construction is based on the fine-rolled rebar anti-floating anchor rod, the first-order rebar of the exposed section of the fine-rolled rebar anti-floating anchor rod can be obtained through the detection system (the first acceleration sensor, the second acceleration sensor and the signal collector). The natural frequency means that the prestress value of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod can be obtained through the pre-acquired relationship curve between the first-order natural frequency and the prestress value.

The present invention can obtain the prestress value of the steel bar in the exposed section of the finished-rolled threaded steel anti-floating anchor rod by obtaining the first-order natural frequency of the steel bar in the exposed section of the finished-rolled threaded steel anti-floating anchor rod, filling the gap of the prestressed anti-floating anchor rod Blank for prestress testing. Compared with the prior art using the strain gauge test method, it has the characteristics of short acquisition time of the prestress value, and avoids the problems of troublesome installation of the strain gauge, easy falling off and failure. Compared with the prior art using the retraction amount detection method, it has the advantages of high precision and high operation safety. Compared with the prior art, the ultrasonic stress detection method has the characteristics of high precision.

In some embodiments, in the step (1), the detection system is used to obtain the first-order fixed frequency of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod under the action of prestress.

In some embodiments, the detection system includes a first acceleration sensor 11 and a second acceleration sensor 12, the first acceleration sensor 11 is installed on the upper end of the steel bar of the exposed section of the finished rolled rebar anti-floating anchor rod, and the second Acceleration sensor 12 is installed on the lower section of steel bar in the exposed section of finished-rolled rebar anti-floating anchor rod, the upper end of the first acceleration sensor 11 is flush with the upper end surface of the steel bar in the exposed section of finished-rolled rebar anti-floating anchor rod, and the second The lower end surface of the acceleration sensor 12 is attached to the upper end surface of the prestressed anchor head 7 at the lower end of the steel bar of the exposed section of the finish-rolled rebar anti-floating anchor rod. The first acceleration sensor 11 and the second acceleration sensor 12 are all connected to the signal collector 13 electrical connection.

In some embodiments, the first acceleration sensor 11 is used to monitor the acceleration time-history curve of the steel bar input in the exposed section of the anti-floating anchor rod of the finished-rolled rebar, and the second acceleration sensor 12 is used to monitor the anti-floating of the finished-rolled rebar. The acceleration time-history curve of the steel bar response in the exposed section of the anchor rod; the signal collector 13 is used to perform time-frequency analysis on the received signal so as to obtain the acceleration excellent frequency f1 corresponding to the first acceleration sensor 11 and the corresponding acceleration of the second acceleration sensor The excellent frequency f2, the acceleration excellent frequency f2 is divided by the acceleration excellent frequency f1 to obtain the first-order natural frequency of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod. Referring to Figure 3 and the accompanying drawings, when testing the detection system, it is necessary to use a rubber hammer 14 to knock the top of the finish-rolled rebar 2, so that the first acceleration sensor and the second acceleration sensor are used for monitoring.

In some embodiments, the prestress value P of the exposed steel bar of the finished rolled rebar anti-floating anchor rod is obtained by the following formula:

Among them, f is the first-order natural frequency of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod, R is the average value of the diameter of the anchor head and the diameter of the finished-rolled rebar, M is the mass of the anchor head, and L is the anti-floating rebar of the finished-rolled rebar. The length of the steel bar in the exposed section of the floating anchor, ρ is the linear density of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor, and a and b are the experimental parameters.

In some embodiments, experimental parameters a and b are obtained as follows:

In conjunction with accompanying drawing 4, when the finish-rolled rebar 2 is stretched in stages, the anti-floating anchor rod of the finish-rolled rebar is obtained by the first acceleration sensor 11, the second acceleration sensor 12 and the signal collector 13 during each stage of load tension The first-order natural frequency f of the exposed steel bar under this load is then obtained through the through-hole pressure sensor 17 to the prestress value P applied to the anti-floating anchor rod of the finished-rolled rebar; After multi-stage load loading, multiple pairs of f and P values are obtained (that is, a first-order natural frequency corresponds to a P value); finally, curve fitting is performed on multiple pairs of f and P values to obtain the values of a and b .

In some embodiments, when the finish-rolled rebar is stretched in stages, it should stand still for a certain period of time (for example, 5min, 10min) under each level of load, that is, the pre-stress applied to the finish-rolled rebar 2 should not be changed within this time. stress size.

Because when applying prestress to the anti-floating anchor rod of finished-rolled screw steel (that is, stretching the finished-rolled rebar), the prestress is not increased to the set value at one time, but the tension is increased by tensioning equipment (such as jacks). and reaction device) to apply prestress step by step. After applying a large prestress value, it needs to be maintained for a period of time under the premise of the prestress value; then increase the applied prestress value, and so on. The prestress value meets the design requirements. Those skilled in the art can understand and understand, and will not repeat them here.

In conjunction with accompanying drawing 3 and accompanying drawing 4, when utilizing detection system of the present invention to obtain the relationship curve between the prestress value and the first-order natural frequency of the exposed section steel bar of finish-rolled rebar anti-floating anchor rod, detection system also includes ( Or be equipped with) a jack and a reaction force device 15, a force transmission component 16 (such as a steel cylinder), and a through-hole pressure sensor 17. That is, when calibration is performed indoors (such as a laboratory) or other places, the cushion layer 5, the finished rebar 2, the prestressed anchor head 7, the prestressed backing plate 6, the force transmission component 16, and the through-hole pressure sensor 17 come together model precision rolled rebar anti-floating anchor rod. Please refer to the attached drawing 4, the upper end of the finish-rolled rebar 2 passes through the cushion layer 5 and is equipped with a prestressed backing plate 6 and a prestressed anchor head 7, the prestressed backing plate 6 and the cushion layer 5 are in contact with each other, and the A force transmission part 16 is arranged below, and the lower section of the finished rolled rebar 2 passes through the force transmission part 16 and is equipped with a prestressed backing plate 6 and a prestressed anchor head 7. The prestressed backing plate 6 under the cushion layer 5 and the force transmission part The components 16 are in contact with each other, and the lower end surface of the prestressed anchor head 7 under the cushion layer 5 is equipped with a through-hole pressure sensor 17 sleeved on the finished-rolled rebar 2 . When the detection system is in use, prestress is applied to the finish-rolled rebar 2 through the jack and the counter force device 15, and the prestress value P applied to the finish-rolled rebar 2 is obtained through the through-hole pressure sensor 17, and passed through the first The acceleration sensor 11, the second acceleration sensor 12 and the signal collector 13 obtain the first-order natural frequency of the exposed section steel bars of the finish-rolled rebar 2, and after carrying out multi-stage load loading to the finish-rolled rebar, obtain many pairs of f and P value (that is to say, a first-order natural frequency corresponds to a P value); finally, the values of a and b can be obtained by performing curve fitting on multiple pairs of f and P values. That is to say, the values of f and P are brought into the following formula for reverse deduction to obtain the values of a and b:

The formula is:

Due to the high cost of the piercing type pressure sensor 17 during the on-site construction of the anti-floating anchor rod of fine-rolled rebar, it is not suitable for detection on the construction site.

The detection system of the present invention has a simple structure at the construction site of the anti-floating bolt, that is, the first acceleration sensor 11, the second acceleration sensor and the signal collector 13 are used to form the detection system at the construction site (supporting rubber hammer 14 , or directly use the rubber hammer on the construction site), which has the characteristics of low cost, recyclable utilization, simple and reliable operation.

Due to the same construction site, the dimensions of the finished rebar 2 used, the dimensions of the prestressed anchor head 7 and the prestressed anchor plate 6 are basically the same. Therefore, for a construction project, the present invention pre-acquires the relationship curve between the prestress value of an exposed steel bar and the first-order natural frequency to perform prestress detection on each anti-floating anchor rod of the entire construction project, which greatly improves the prestress detection. The efficiency and reduce the cost of prestress testing.

Of course, for different construction sites, the size of the finished-rolled rebar 2 and the size of the prestressed anchor head 7 of the designed anti-floating anchor will be different, so the prestress value and the first-order inherent frequency relationship curve.

When the present invention detects on site, it only needs to obtain the first-order natural frequency of the exposed section steel bar of the finished-rolled rebar anti-floating anchor rod through the detection system (i.e. the first acceleration sensor, the second acceleration sensor and the signal collector). It has the characteristics of fast detection speed, convenient on-site operation, stability and reliability, which greatly saves the time of anti-floating anchor prestress detection, so that the construction progress will not be affected by the prestress detection, and finally achieves the purpose of saving construction costs.

The present invention pre-acquires the relationship curve between the first-order natural frequency and the prestress value of the exposed steel bar of the finish-rolled rebar anti-floating anchor rod in the indoor laboratory, and only needs to calibrate one anti-floating anchor rod to obtain the whole batch. The relationship curve between the second first-order natural frequency and the prestress value further improves the detection speed of the anti-floating anchor bolt prestress. And the present invention can be carried out indoors (as the relationship curve between the first-order natural frequency and the size of the prestress value of the exposed section steel bar of the finish-rolled rebar anti-floating anchor bar obtained in the laboratory) and the on-site detection can be carried out simultaneously, without affecting the on-site prestress resistance. The detection progress of the floating anchor rod, and then achieve the purpose of improving the detection speed.

The detection method of the present invention has the characteristics of simple and convenient operation, high reliability, and fast detection speed. Since the number of prestressed anti-floating anchor rods in a construction site is relatively large, it is necessary to detect each anti-floating anchor rod, so , can save a lot of detection time on the whole, thereby shortening the construction period of the anti-floating anchor rod and reducing the construction cost.

Claims (7)

1. based on the prestressed non-destructive testing method of the natural frequency of the finish-rolled rebar anti-floating anchor rod, it is characterized in that, comprising: (1) Pre-acquire the first-order natural frequency of the exposed steel bar of the finished rolled rebar anti-floating anchor rod under the prestressing effect, so as to establish the prestress value and first-order natural frequency of the exposed steel bar of the finished rolled rebar anti-floating anchor rod frequency curve; (2) Obtain the first-order natural frequency of the steel bars in the exposed section of the anti-floating anchor rod of the finished rolled rebar that has been prestressed on site through the detection system; (3) According to the relationship curve between the prestress value and the first-order fixed frequency established in step (1) and the first-order fixed frequency obtained in step (2), the prestress of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor rod is obtained value. 2. the prestressed non-destructive testing method based on the natural frequency of the finish-rolled rebar anti-floating anchor rod according to claim 1, is characterized in that, in described step (1), obtain the finish-roll rebar anti-floating by detection system The first-order fixed frequency of the steel bar in the exposed section of the anchor rod under the action of prestress. 3. the prestressed non-destructive detection method based on the natural frequency of the finish-rolled rebar anti-floating anchor rod according to claim 2, wherein the detection system includes a first acceleration sensor and a second acceleration sensor, and the first The acceleration sensor is installed on the upper end of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod, and the second acceleration sensor is installed on the lower section of the steel bar in the exposed section of the finished-rolled rebar steel anti-floating anchor rod. The upper end surface of the steel bar of the exposed section of the rolled rebar anti-floating anchor is flush, and the lower end surface of the second acceleration sensor is attached to the upper end surface of the prestressed anchor head at the lower end of the steel bar of the exposed section of the finished rolled rebar anti-floating anchor. Both the first acceleration sensor and the second acceleration sensor are electrically connected to the signal collector. 4. The prestressed non-destructive detection method based on the natural frequency of the finished-rolled rebar anti-floating anchor rod according to claim 3, wherein the first acceleration sensor is used to monitor the exposed section of the finished-rolled rebar anti-floating anchor rod The acceleration time-history curve of the steel bar input, the second acceleration sensor is used to monitor the acceleration time-history curve of the steel bar response of the exposed section of the finish-rolled rebar anti-floating anchor rod; the signal collector is used for time-frequency analysis of the received signal Thereby, the acceleration excellent frequency f1 corresponding to the first acceleration sensor and the acceleration excellent frequency f2 corresponding to the second acceleration sensor are obtained, and the acceleration excellent frequency f2 is divided by the acceleration excellent frequency f1 to obtain the first-order intrinsic frequency. 5. the prestressed non-destructive testing method based on the natural frequency of the finish-rolled rebar anti-floating anchor rod according to claim 4, wherein the prestress value P of the exposed section reinforcement of the finish-rolled rebar anti-floating anchor rod Obtained by the following formula:

Among them, f is the first-order natural frequency of the steel bar in the exposed section of the finished-rolled rebar anti-floating anchor rod, R is the average value of the diameter of the anchor head and the diameter of the finished-rolled rebar, M is the mass of the anchor head, and L is the anti-floating rebar of the finished-rolled rebar. The length of the steel bar in the exposed section of the floating anchor, ρ is the linear density of the steel bar in the exposed section of the finished rolled rebar anti-floating anchor, and a and b are the experimental parameters. 6. the prestressed non-destructive testing method based on the natural frequency of finish-rolled rebar steel anti-floating anchor rod according to claim 5, is characterized in that, experimental parameter a and b obtain by following way: When the finished-rolled rebar is stretched in stages, the first acceleration sensor, the second acceleration sensor and the signal collector are used to obtain a part of the steel bar of the exposed section of the anti-floating anchor rod of the finished-rolled rebar under the load. The first-order natural frequency f, and then the prestress value P applied to the anti-floating anchor rod of fine-rolled rebar steel is obtained through the through-hole pressure sensor; f and P values; finally, curve fitting is performed on multiple pairs of f and P values to obtain the values of a and b. 7. The prestressed non-destructive testing method based on the natural frequency of the finish-rolled rebar anti-floating anchor rod according to claim 6, wherein, when the finish-rolled rebar is stretched in stages, it should be at rest under each level of load certain time.

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