Bridge steel-concrete combined section void condition monitor and construction method thereof

Abstract

The invention relates to the technical field of bridge detection, in particular to a bridge steel-concrete combined section void condition monitor and a construction method thereof, and the monitor comprises a plurality of surface-mounted strain gauges; a strain gauge assembly is arranged on the outer side of the mounting plate, and the two ends of the strain gauge assembly are fixedly connected with the mounting plate through mounting frames; two reflecting plates which are arranged in parallel are installed in an inner cavity of the outer shell, and the reflecting plates are 'lt'; reflecting layers are arranged on the surfaces, close to each other, of the two reflecting plates; the method has the beneficial effects that the to-be-detected void area of the steel-concrete combined section is divided, a column of surface-mounted strain gauges for monitoring parameters are arranged on each divided area, and a laser beam is reflected for multiple times between the two reflecting plates, so that the initial emission angle can be amplified, the deformation of the void area can be detected more accurately, and the detection accuracy is improved. The device has the characteristics of accurate data, easiness in installation and the like, and is good in detection effect and high in detection conclusion credibility.

Description

Technical Field

[0001] The invention relates to the technical field of bridge detection, and in particular to a monitoring device for the void condition of a steel-concrete joint section of a bridge and a construction method thereof. Background Art

[0002] In the field of modern bridge construction, steel-concrete combined sections are used in more and more scenarios; steel-concrete combined sections are composed of different materials combined into an integral structure that work together and have better properties than single material structures. Steel-concrete composite structure bridges have good technical characteristics and higher cost-effectiveness compared to other types of bridges. They are not only suitable for large-span bridge construction, but also have strong competitiveness in small and medium-span bridge construction.

[0003] In the prior art, during the construction process and later use of the steel-concrete joint section, due to the long-term repeated action of vehicles, the steel plates and concrete in local areas may be tensile against each other. When the tensile force exceeds a certain level or under the influence of other factors, the steel plates in these areas may be separated from the concrete, which is the so-called void phenomenon. At present, there are many methods for void identification at home and abroad, such as the knocking method of manually knocking on the surface of the test object; the magnetic particle inspection method of applying magnetic powder on the concrete surface and detecting it with a magnetometer after it dries; the drilling sampling method of coring through drilling, etc.

[0004] However, due to the special material properties and complex structure of the steel-concrete joint section, the above methods have great limitations in practical application: the tapping method is highly subjective, and its accuracy is related to the proficiency of the staff, which is easy to cause misjudgment; the magnetic particle inspection method is difficult to obtain accurate results due to the complex structure of the steel-concrete joint section itself, the non-uniform concrete material, and the large number of structural parts; the drilling sampling method belongs to the local damage detection method, and multiple drillings will cause greater damage to the structure. It is generally used for secondary confirmation or sampling surveys in engineering. Therefore, these methods are not completely applicable. To this end, the present invention proposes a bridge steel-concrete joint section degassing condition monitoring instrument and its construction method to solve the above problems. Summary of the invention

[0005] The object of the present invention is to provide a void condition monitoring device for a steel-concrete joint section of a bridge and a construction method thereof, so as to solve the problem that the traditional void detection methods proposed in the above background technology all have great limitations.

[0006] To achieve the above object, the present invention provides the following technical solution: a monitoring device for the hollowing condition of a steel-concrete joint section of a bridge, comprising:

[0007] Surface-mounted strain gauges, wherein a plurality of surface-mounted strain gauges are provided and are distributed at equal intervals on the web and bottom plate of the steel-concrete joint section;

[0008] The surface-mounted strain gauge comprises a mounting plate fixedly connected to the surface of the steel-concrete joint section, a strain gauge assembly is arranged on the outer side of the mounting plate, and both ends of the strain gauge assembly are fixedly connected to the mounting plate through a mounting frame;

[0009] The strain gauge assembly includes an outer shell, and two parallel reflective plates are installed in the inner cavity of the outer shell. The reflective plates are in the shape of a letter "<", and the surfaces of the two reflective plates close to each other are provided with reflective layers. A laser transmitter and a laser receiver are respectively provided at two ends of the outer shell. The laser beam emitted by the laser transmitter irradiates a surface of a reflective layer at an angle of forty-five degrees and irradiates the laser receiver after reflection.

[0010] Preferably, both ends of the outer shell are fixedly connected with a mounting sleeve and an open spherical shell respectively, the outer side of the laser receiver is provided with a thread and is screwed into the inner cavity of the mounting sleeve, the mounting sleeve is connected with the inner cavity of the outer shell, and a transparent glass plate is provided at the connection.

[0011] Preferably, a fixing tube is fixedly connected to the surface of the laser receiver, one end of the fixing tube extends to the outside of the mounting sleeve and is fixedly connected to a knob, the knob rests against the end face of the mounting sleeve, and an annular sealing gasket is arranged between the two, and a receiver cable electrically connected to the laser receiver is passed through the inner cavity of the fixing tube.

[0012] Preferably, a connecting ball is provided on the outer side of the end of the laser emitter, and the two are fixedly connected by a hollow connecting tube. The connecting ball is rotatably installed in the inner cavity of the open spherical shell and adapted thereto. A through hole is penetrated through the middle of the connecting ball. The laser beam emitted by the laser emitter passes through the through hole into the inner cavity of the outer shell. A protective hose is fixedly connected to the end face of the laser emitter, and one end of the protective hose is fixed to the surface of the outer shell.

[0013] Preferably, a retaining ring 1 is fixedly connected to the outer side of the mounting sleeve, a retaining ring 2 is fixedly connected to the outer side of the laser emitter, and the mounting frame includes two symmetrically arranged arc-shaped clamping parts arranged in a circular ring shape, and the two groups of mounting frames are respectively fixedly sleeved on the outer side of the mounting sleeve and the outer side of the laser emitter.

[0014] Preferably, an arc pad is bonded and fixed to the inner wall of the arc clamp, and a connecting block and a protrusion are fixedly connected to both ends of the arc clamp respectively. The surfaces of the connecting block and the protrusion are provided with connecting holes, and the two arc clamps are fixedly connected by bolts.

[0015] Preferably, one end of the connecting block is fixedly connected to a connecting plate, a long waist hole is opened on the surface of the connecting plate, a shock-proof pad is bonded and fixed to the surface of the connecting plate away from the connecting block, and a fixing stud corresponding to the waist hole is fixedly connected to the surface of the mounting plate. The connecting plate and the fixing stud are pressed and fixed by nuts, and a pad is provided between the nut and the connecting plate, and the two fixing studs are connected together as a group at both ends of the pad.

[0016] Preferably, an opening is provided on one side surface of the outer shell, and a cover plate for sealing the opening is fixedly connected to the opening by bolts, and a positioning block is fixedly provided on the inner wall of the outer shell, and the positioning block abuts against the surface of the reflector and positions it.

[0017] A construction method according to the above-mentioned bridge steel-concrete joint section debonding condition monitoring device specifically comprises the following steps:

[0018] Step 1: Determine the distribution area of ​​the voids in the steel-concrete joint section:

[0019] Based on the force analysis, stress analysis was conducted on different parts of the steel-concrete joint section, and it was found that the area with large normal stress is prone to voiding;

[0020] Based on construction analysis, there was insufficient vibration during the construction process, resulting in the failure of local concrete bonding at corners.

[0021] Combined with the material properties, settlement and inclination of the steel-concrete joint section to be tested, the finite element analysis results of the steel-concrete joint section are used to select the area with voids for subsequent strain monitoring;

[0022] Step 2: Determine the placement method of the surface-mount strain gauge:

[0023] According to the scale, settlement and testing requirements of the steel-concrete joint section, the area to be tested for the steel-concrete joint section is divided into regions;

[0024] A row of surface-mounted strain gauges for monitoring parameters are arranged on each divided area;

[0025] Step 3: Collect parameter information and conduct positioning monitoring of the empty parts:

[0026] Summarize all the data collected by the surface-mounted strain gauges used for testing, then process the collected information data and display them intuitively in the form of images;

[0027] Once a sudden change in the strain value of a certain point is found, it can be determined that there may be void damage at that point, and the scope of the void area can be preliminarily determined by comparing the strain with the adjacent points;

[0028] When more accurate positioning is required, the detection area where the possible empty part is located is further divided into smaller detection areas using the same division method, and the above operation is repeated.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The present invention divides the steel-concrete combination section hollowing-out area to be tested, and arranges a row of surface-mounted strain gauges for monitoring parameters in each divided area. The surface-mounted strain gauge comprises a mounting plate, a mounting frame and a strain gauge assembly. The strain gauge assembly comprises an outer shell and two reflective plates installed in the inner cavity of the outer shell. A laser transmitter and a laser receiver are respectively arranged at two ends of the outer shell. The reflective plates are in the shape of a “>”. The surfaces of the two reflective plates close to each other are both provided with a reflective layer, which can reflect the laser beam emitted by the laser transmitter and located between the two reflective plates to be received by the laser receiver. When the installation position of the surface-mounted strain gauge is hollowed out, the steel plate inside the steel-concrete combination section at this position will bulge outward in a normal direction, thereby changing the angle at which the laser beam is emitted by the laser transmitter. Since the laser beam will experience multiple reflections between the two reflective plates, the initial emission angle can be magnified, so that the deformation of the hollowing-out area can be detected more accurately. Compared with the traditional detection method, the device has the characteristics of accurate data and easy installation, and does not need to install or use large-scale detection equipment. It can accurately locate the hollowing-out position of the steel-concrete combination section, and has good detection effect and high credibility of detection conclusion. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of the overall structure distribution position of the present invention;

[0032] Figure 2 It is a three-dimensional schematic diagram of the structure of the surface-mounted strain gauge of the present invention;

[0033] Figure 3 It is an exploded schematic diagram of the structure of the surface-mounted strain gauge of the present invention;

[0034] Figure 4 It is a three-dimensional schematic diagram of the mounting frame structure of the present invention;

[0035] Figure 5 It is an exploded schematic diagram of the structure of the strain gauge assembly of the present invention;

[0036] Figure 6 This is a schematic diagram of the interior of the outer shell structure of the present invention;

[0037] Figure 7 It is a three-dimensional schematic diagram of the structure of the laser transmitter of the present invention;

[0038] Figure 8 This is a schematic diagram of the laser beam reflection path of the present invention;

[0039] Fig. 9The strain variation curve of the bottom plate of the steel-concrete combined section in the present invention at the row a position;

[0040] Fig.10 The strain variation curve of the bottom plate of the steel-concrete combined section at the column b position of the present invention;

[0041] Fig.11 The strain variation curve of the web c row position of the steel-concrete joint section of the present invention;

[0042] Fig.12 The strain variation curve of the web d row position of the steel-concrete joint section of the present invention;

[0043] Fig.13 It is a schematic diagram of the construction process of the present invention.

[0044] In the figure: 1. surface-mount strain gauge; 2. mounting plate; 21. fixing stud; 22. pad; 3. mounting frame; 31. arc-shaped clamp; 32. arc-shaped pad; 33. connecting block; 331. protrusion; 332. connecting hole; 34. connecting plate; 35. waist hole; 36. shock-proof pad; 4. strain gauge assembly; 41. outer shell; 411. mounting sleeve; 412. open spherical shell; 413. retaining ring 1; 414. positioning block; 415. cover plate; 42. reflective plate; 421. reflective layer; 43. laser transmitter; 431. connecting ball; 432. connecting tube; 433. through hole; 434. protective hose; 435. retaining ring 2; 44. laser receiver; 441. fixing tube; 442. knob; 443. receiver cable. DETAILED DESCRIPTION

[0045] In order to make the purpose and technical solution of the present invention clearly and completely described, and the advantages more clearly understood, the embodiments of the present invention are further described in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are part of the embodiments of the present invention, rather than all of the embodiments, and are only used to explain the embodiments of the present invention, and are not used to limit the embodiments of the present invention. All other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] In the description of the present invention, it should be noted that the terms "center", "middle", "upper", "lower", "left", "right", "inner", "outer", "top", "bottom", "side", "vertical", "horizontal" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "one", "first", "second", "third", "fourth", "fifth", "sixth" are used for descriptive purposes only, and cannot be understood as indicating or implying relative importance.

[0047] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" 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 or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0048] For the purpose of simplicity and illustration, the principles of the embodiments are mainly described by reference to examples. In the following description, many specific details are proposed to provide a thorough understanding of the embodiments. However, it is obvious that for those of ordinary skill in the art, these embodiments may not be limited to these specific details in practice. In some instances, known methods and structures are not described in detail to avoid making these embodiments unnecessarily difficult to understand. In addition, all embodiments can be used in combination with each other.

[0049] See also Figures 1 to 8 , the present invention provides a technical solution:

[0050] Embodiment 1, a bridge steel-concrete joint section debonding condition monitoring device, comprising:

[0051] Surface-mounted strain gauges 1 are provided in plurality and are distributed at equal intervals on the web and bottom plate of the steel-concrete joint section, such as Figure 1 As shown, the surface-mounted strain gauge 1 can be distributed linearly with equal spacing or in a rectangular array according to actual needs. In addition, since the steel-concrete joint section of the bridge is usually a bilaterally symmetrical distribution structure, the surface-mounted strain gauge 1 can be installed only on one side of the web and half of the bottom plate of the steel-concrete joint section;

[0052] Secondly, the surface-mounted strain gauge 1 includes a mounting plate 2 fixedly connected to the surface of the steel-concrete joint section. The mounting plate 2 and the steel-concrete joint section can be fixed by glue or expansion bolts. A strain gauge assembly 4 is arranged on the outside of the mounting plate 2. Both ends of the strain gauge assembly 4 are fixedly connected to the mounting plate 2 through a mounting frame 3. The mounting frame 3 is used to install and position the strain gauge assembly 4. The specific structures of the mounting frame 3 and the strain gauge assembly 4 are described below.

[0053] Specifically, the strain gauge assembly 4 includes an outer shell 41, and two parallel reflective plates 42 are installed in the inner cavity of the outer shell 41. The reflective plates 42 are in the shape of a "<" and the surfaces of the two reflective plates 42 close to each other are both provided with a reflective layer 421. Figure 5 and Figure 6 As shown, the two halves of the reflective plate 42 are perpendicular to each other, and the two ends of the outer shell 41 are respectively provided with a laser emitter 43 and a laser receiver 44. The laser beam emitted by the laser emitter 43 irradiates the surface of a reflective layer 421 at a 45-degree angle, and irradiates the laser receiver 44 after being reflected. Figure 8 As shown, the laser beam is irradiated on a reflective layer 421 at an angle of forty-five degrees, and is emitted coaxially and in the same direction after being reflected four times between two reflective plates 42, and is finally received by a laser receiver 44. When the incident angle of the laser beam changes, the multiple reflections of the laser beam will amplify the error after the reflection (the error here refers to the distance that the laser beam deviates from the initial position), ensuring that the device can accurately detect the slight deformation at the gap between the steel-concrete joint section, thereby improving the credibility of the detection conclusion.

[0054] In order to install, position and protect the laser receiver 44, the present application also has a mounting sleeve 411 and an open spherical shell 412 fixedly connected to both ends of the outer shell 41, and the outer side of the laser receiver 44 is provided with a thread and screwed into the inner cavity of the mounting sleeve 411. Figure 5 and Figure 6 As shown, the mounting sleeve 411 is used to install, position and protect the laser receiver 44 . The mounting sleeve 411 is connected to the inner cavity of the outer shell 41 , and a transparent glass plate is provided at the connection to ensure that the laser beam can pass through the inner wall of the outer shell 41 and irradiate the laser receiver 44 .

[0055] In order to prevent water from entering the laser receiver 44, the present application also has a fixing tube 441 fixedly connected to the surface of the laser receiver 44, one end of the fixing tube 441 extends to the outside of the mounting sleeve 411 and is fixedly connected to a knob 442. When the laser receiver 44 is installed, the staff only needs to tighten the knob 442. The knob 442 rests against the end face of the mounting sleeve 411, and an annular sealing gasket is provided therebetween to prevent water from entering the inner cavity of the mounting sleeve 411. A receiver cable 443 electrically connected to the laser receiver 44 is also passed through the inner cavity of the fixing tube 441.

[0056] In order to limit the movement of the laser emitter 43, the present application also has a connecting ball 431 disposed on the outer side of the end of the laser emitter 43, and the two are fixedly connected by a hollow connecting tube 432, and the connecting ball 431 is rotatably mounted in the inner cavity of the open spherical shell 412 and adapted thereto, combined with Figure 7 and Figure 5 As shown, the laser emitter 43 can move on the outside of the outer shell 41, and the laser emitter 43 will be restricted by the open spherical shell 412 and the connecting ball 431 when moving, that is, the laser emitter 43 can only rotate around the center of the open spherical shell 412 and the connecting ball 431. A through hole 433 is opened in the middle of the connecting ball 431. The laser beam emitted by the laser emitter 43 passes through the through hole 433 and enters the inner cavity of the outer shell 41, which can avoid the laser beam emitted by the laser emitter 43 being blocked by the side wall of the outer shell 41. In addition, the movement of the laser emitter 43 will change the emission angle of the laser beam for subsequent detection. A protective hose 434 is fixedly connected to the end face of the laser emitter 43, and one end of the protective hose 434 is fixed to the surface of the outer shell 41. The protective hose 434 itself has deformation ability and can adapt to the rotation and movement of the laser emitter 43. The protective hose 434 is used to protect the end of the laser emitter 43.

[0057] In order to install the strain gauge assembly 4, the present application also has a retaining ring 413 fixedly connected to the outside of the mounting sleeve 411, a retaining ring 435 fixedly connected to the outside of the laser emitter 43, and the mounting frame 3 includes two symmetrically arranged arc-shaped clamping members 31 arranged in a circular ring shape. The two groups of mounting frames 3 are respectively fixedly sleeved on the outside of the mounting sleeve 411 and the outside of the laser emitter 43. The two groups of mounting frames 3 clamp and position the two ends of the strain gauge assembly 4 respectively to ensure that the strain gauge assembly 4 can be correctly installed on the surface of the steel-concrete joint section.

[0058] In order to describe the structure of the mounting frame 3 in detail, the present application also has an arc pad 32 bonded and fixed to the inner wall of the arc clamp 31, which is used to protect the mounting sleeve 411 and the laser emitter 43 to prevent them from being damaged by excessive extrusion force. The two ends of the arc clamp 31 are respectively fixedly connected with a connecting block 33 and a convex block 331. The surfaces of the connecting block 33 and the convex block 331 are provided with connecting holes 332. The two arc clamps 31 are fixedly connected by bolts. Figure 4 and Figure 3 It can be seen that the mounting frame 3 is symmetrically arranged as a whole, and can clamp and fix the strain gauge assembly 4.

[0059] In order to connect the mounting frame 3 with the mounting plate 2, the present application also has a connecting plate 34 fixedly connected to one end of the connecting block 33, a long waist hole 35 is opened on the surface of the connecting plate 34, a shock-absorbing pad 36 is bonded and fixed to the surface of the connecting plate 34 away from the connecting block 33, and a fixing stud 21 corresponding to the waist hole 35 is fixedly connected to the surface of the mounting plate 2, and the connecting plate 34 and the fixing stud 21 are pressed and fixed by nuts, such as Figure 3 and Figure 4 As shown, the mounting bracket 3 is installed on the surface of the mounting plate 2, and the mounting bracket 3 can be finely adjusted in position along the length direction of the waist hole 35. A pad 22 is arranged between the nut and the connecting plate 34, and two fixing studs 21 are connected together as a group at both ends of the pad 22, which can improve the stability of the connection between the mounting bracket 3 and the mounting plate 2.

[0060] In order to facilitate the installation of the reflector 42, the present application also has an opening on one side of the outer shell 41, and a cover plate 415 for sealing the opening is fixedly connected to the opening by bolts, such as Figure 5 As shown, the cover plate 415 can be detachably installed so that the reflective plate 42 can be installed into the inner cavity of the outer shell 41. A positioning block 414 is fixedly provided on the inner wall of the outer shell 41. The positioning block 414 abuts against the surface of the reflective plate 42 and positions it. The positioning block 414 is provided to prevent the reflective plate 42 from shaking and shifting in position in the inner cavity of the outer shell 41, thereby preventing the reflective plate 42 from affecting the reflection path of the laser beam.

[0061] The present invention also discloses a construction method according to the above-mentioned bridge steel-concrete joint section debonding condition monitoring device, which specifically comprises the following steps:

[0062] Step 1: Determine the distribution area of ​​the voids in the steel-concrete joint section:

[0063] Based on the force analysis, stress analysis was conducted on different parts of the steel-concrete joint section, and it was found that the area with large normal stress is prone to voiding;

[0064] Based on construction analysis, there was insufficient vibration during the construction process, resulting in the failure of local concrete bonding at corners.

[0065] Combined with the material properties, settlement and inclination of the steel-concrete joint section to be tested, the finite element analysis results of the steel-concrete joint section are used to select the area with voids for subsequent strain monitoring;

[0066] In this example, the steel-concrete joint section is 3m long, 6.48m high, 12.6m wide on the top plate, and 7m wide on the bottom plate. After finite element software analysis, the bottom plate and web plate are selected as the areas to be tested;

[0067] Step 2: Determine the placement method of the surface-mount strain gauge 1:

[0068] According to the scale, settlement and detection requirements of the steel-concrete joint section, the area to be tested for the steel-concrete joint section is divided into regions; in this example, Figure 1 As shown, the bottom plate and the web of the area to be inspected are divided into two areas, located at the center of the bottom plate and the web and 0.15m away from the corner respectively;

[0069] A row of surface-mounted strain gauges 1 for monitoring parameters is placed in each divided area; in the divided area, two rows of surface-mounted strain gauges 1 are placed on the bottom plate and the web plate respectively, and 9 surface-mounted strain gauges 1 are placed along the bridge at an interval of 0.3m on the steel-concrete joint section with a length of 3m (for the convenience of recording, the row of surface-mounted strain gauges 1 placed at the center of the bottom plate and at a position 0.15m away from the corner are recorded as row a and row b respectively, and the row of surface-mounted strain gauges 1 placed at the center of the web plate and at a position 0.15m away from the corner are recorded as row c and row d respectively);

[0070] Step 3: Collect parameter information and conduct positioning monitoring of the empty parts:

[0071] Summarize all the data collected by the surface-mounted strain gauge 1 for detection, and then process the collected information data to display them intuitively in the form of images;

[0072] Once a sudden change in the strain value of a certain point is found, it can be determined that there may be void damage at that point. By comparing the strain with the adjacent points, the scope of the void area can be preliminarily determined; Fig. 9 and Fig.10 As shown in the figure, the strain change curve of the attached strain gauge 1 in column a shows a sudden change at 0.3m, and the strains of column a and column b that are not empty after 0.3m increase slowly and maintain a certain regularity. It can be preliminarily judged that the center of the bottom plate of the steel-concrete combined section is empty at 0.3m along the bridge direction. At the same time, the approximate empty area can be obtained by comparing the adjacent points; Fig.11 and Fig.12 As shown in the figure, the strain change curve of the attached strain gauge 1 in column d shows a sudden change at 0.9m, and the strain changes of column d after 0.9m and column c without emptying are relatively uniform. It can be preliminarily judged that the web of the steel-concrete joint section is empty at 0.9m along the bridge at a position of 0.15m away from the corner. At the same time, the approximate emptying area can be obtained by comparing the adjacent points.

[0073] like Fig.13 As shown, when more accurate positioning is required, the detection area where the possible empty space is located can be further divided into smaller detection areas using the same division method, and the above operation can be repeated.

[0074] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A monitoring device for the emptying condition of the steel-concrete joint section of a bridge, characterized by: include: A surface-mounted strain gauge (1), wherein a plurality of the surface-mounted strain gauges (1) are arranged and distributed at equal intervals on the web and bottom plate of the steel-concrete joint section; The surface-mounted strain gauge (1) comprises a mounting plate (2) fixedly connected to the surface of the steel-concrete joint section, a strain gauge assembly (4) is arranged outside the mounting plate (2), and both ends of the strain gauge assembly (4) are fixedly connected to the mounting plate (2) via a mounting frame (3); The strain gauge assembly (4) comprises an outer shell (41), the inner cavity of the outer shell (41) is provided with two parallel reflective plates (42), the reflective plates (42) are in the shape of a letter "<", and the surfaces of the two reflective plates (42) close to each other are both provided with reflective layers (421), and the two ends of the outer shell (41) are respectively provided with a laser transmitter (43) and a laser receiver (44), and the laser beam emitted by the laser transmitter (43) irradiates the surface of a reflective layer (421) at an angle of forty-five degrees and irradiates the laser receiver (44) after being reflected.

2. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 1 is characterized in that: The two ends of the outer shell (41) are respectively fixedly connected with a mounting sleeve (411) and an open spherical shell (412); the outer side of the laser receiver (44) is provided with a thread and is screwed into the inner cavity of the mounting sleeve (411); the mounting sleeve (411) is communicated with the inner cavity of the outer shell (41), and a transparent glass plate is provided at the connection.

3. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 2 is characterized in that: A fixing tube (441) is fixedly connected to the surface of the laser receiver (44), one end of the fixing tube (441) extends to the outside of the mounting sleeve (411) and is fixedly connected to a knob (442), the knob (442) abuts against the end surface of the mounting sleeve (411), and an annular sealing gasket is arranged between the two, and a receiver cable (443) electrically connected to the laser receiver (44) is passed through the inner cavity of the fixing tube (441).

4. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 2 is characterized in that: A connecting ball (431) is arranged on the outer side of the end of the laser emitter (43), and the two are fixedly connected via a hollow connecting tube (432). The connecting ball (431) is rotatably mounted in the inner cavity of the open spherical shell (412) and is adapted thereto. A through hole (433) is provided through the middle of the connecting ball (431). The laser beam emitted by the laser emitter (43) passes through the through hole (433) and enters the inner cavity of the outer shell (41). A protective hose (434) is fixedly connected to the end face of the laser emitter (43), and one end of the protective hose (434) is fixed to the surface of the outer shell (41).

5. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 4 is characterized in that: The outer side of the installation sleeve (411) is fixedly connected to a retaining ring 1 (413), the outer side of the laser emitter (43) is fixedly connected to a retaining ring 2 (435), the installation frame (3) comprises two arc-shaped clamping parts (31) which are symmetrically arranged and assembled into a circular ring shape, and the two groups of the installation frames (3) are respectively fixedly sleeved on the outer side of the installation sleeve (411) and the outer side of the laser emitter (43).

6. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 5 is characterized in that: An arc-shaped pad (32) is bonded and fixed to the inner wall of the arc-shaped clamping piece (31), and a connecting block (33) and a convex block (331) are respectively fixedly connected at both ends of the arc-shaped clamping piece (31), and connecting holes (332) are provided on the surfaces of the connecting block (33) and the convex block (331), and the two arc-shaped clamping pieces (31) are fixedly connected by bolts.

7. The monitoring device for the hollowing condition of the steel-concrete joint section of a bridge according to claim 6 is characterized in that: One end of the connecting block (33) is fixedly connected to a connecting plate (34), a long strip waist hole (35) is provided on the surface of the connecting plate (34), a shock-absorbing pad (36) is bonded and fixed to the surface of the connecting plate (34) away from the connecting block (33), a fixing stud (21) corresponding to the waist hole (35) is fixedly connected to the surface of the mounting plate (2), the connecting plate (34) and the fixing stud (21) are pressed and fixed by nuts, and a pad (22) is provided between the nut and the connecting plate (34), and two fixing studs (21) are sleeved and connected together as a group at both ends of the pad (22).

8. The monitoring device for the void condition of the steel-concrete joint section of a bridge according to claim 1 is characterized in that: An opening is provided on one side surface of the outer shell (41), and a cover plate (415) is fixedly connected to the opening by bolts to seal the opening. A positioning block (414) is fixedly provided on the inner wall of the outer shell (41), and the positioning block (414) abuts against the surface of the reflective plate (42) to position the reflective plate (42).

9. A construction method for a bridge steel-concrete joint section void condition monitoring device according to any one of claims 1 to 8, characterized in that: The specific steps include: Step 1: Determine the distribution area of ​​the voids in the steel-concrete joint section: Based on the force analysis, stress analysis was conducted on different parts of the steel-concrete joint section, and it was found that the area with large normal stress is prone to voiding; Based on construction analysis, there was insufficient vibration during the construction process, resulting in the failure of local concrete bonding at corners. Combined with the material properties, settlement and inclination of the steel-concrete joint section to be tested, the finite element analysis results of the steel-concrete joint section are used to select the area with voids for subsequent strain monitoring; Step 2: Determine the placement method of the surface-mount strain gauge (1): According to the scale, settlement and testing requirements of the steel-concrete joint section, the area to be tested for the steel-concrete joint section is divided into regions; A row of surface-mounted strain gauges (1) for monitoring parameters are arranged on each divided area; Step 3: Collect parameter information and conduct positioning monitoring of the empty parts: Summarize all the data collected by the surface-mounted strain gauges (1) for detection, and then process the collected information data to display them visually in the form of images; Once a sudden change in the strain value of a certain point is found, it can be determined that there may be void damage at that point, and the scope of the void area can be preliminarily determined by comparing the strain with the adjacent points; When more accurate positioning is required, the detection area where the possible empty part is located is further divided into smaller detection areas using the same division method, and the above operation is repeated.

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