A loading method suitable for static and dynamic load tests in old bridge sites

Abstract

The present invention discloses a loading method suitable for static and dynamic load tests in old bridge sites. Before the static and dynamic load tests are carried out, a pedestal foundation and a reaction frame foundation are set at the test site to locate the test area, and then a track and a mobile pedestal are set to carry the test beam to the test area. After the beam is carried to the test area, a jack is installed using the reaction frame. The overall test site has fewer installation structures, fewer reaction frames, a high degree of prefabrication, and convenient transportation of small-volume components. The assembly process is simple and safe, the operation space is large, and repeated test operations are convenient. The mobile pedestal simultaneously has the functions of carrying the test beam and limiting and supporting the beam in static and dynamic load tests. The method has strong applicability and can meet the static and dynamic load test requirements of beams with various cross-sections such as T-shaped, I-shaped, and box-shaped by changing the positions of the mobile pedestal, the reaction frame, the jack, and the distribution beam.

Description

Technical Field

[0001] The present invention relates to the technical field of bridge maintenance and inspection, and more particularly to a loading method suitable for static and dynamic load tests in old bridge sites. Background Art

[0002] The static and dynamic load test of a bridge is to apply static and dynamic loads to the designated locations of the bridge. By measuring the stress, strain, deflection, cracks, as well as the natural frequency, damping ratio, impact coefficient and other parameters of the bridge structure, the actual working performance and bearing capacity of the tested span structure under load can be understood, an overall evaluation of the bridge structure can be made, and the safety reserve or overload capacity of the structure can be grasped.

[0003] In order to understand the actual working status of bridge structures that have been in service for a period of time, it is necessary to conduct static and dynamic load tests on old bridges in order to explore the operational status, degree of damage, bearing capacity and remaining life of existing structures, and provide a basis and reference for bridge maintenance, reconstruction and reinforcement.

[0004] Conventional laboratories are mostly used to conduct scaled model tests. Due to limited space, it is difficult to conduct full-scale model tests. In addition, old bridges are often large in size, heavy in weight, and have structural damage, which makes them inconvenient to load and unload and transport. The transportation process may cause further damage to the structure, thereby interfering with the accuracy of the test results. Therefore, old bridge tests are more suitable for on-site testing at the demolition site.

[0005] At present, static and dynamic load tests of bridge structures are often carried out using steel structure reaction frames. The reaction frames are mainly composed of beams, columns, bases, etc. All components are assembled by welding or bolting. Conventional reaction frames are relatively fixed in shape, with poor applicability and mobility. They are also limited by the pedestals at both ends, making it difficult to place test specimens under the reaction frames. Summary of the Invention

[0006] An object of the present invention is to solve at least the above problems and to provide at least the advantages which will be described hereinafter.

[0007] Another object of the present invention is to provide a loading method suitable for static and dynamic load tests in old bridge sites, so as to solve the technical problems in the prior art of poor flexibility in static and dynamic load tests on bridge structures and inability to meet the diverse and repeated testing requirements.

[0008] In order to achieve these objects and other advantages according to the present invention, a loading method suitable for static and dynamic load tests in old bridge sites is provided, comprising the following steps:

[0009] S1. Level the test site to ensure that the bearing capacity of the foundation meets the test requirements;

[0010] S2. Construct a pedestal foundation and a reaction frame foundation at the test site. The upper surfaces of the pedestal foundation and the reaction frame foundation should be flush with the ground. The pedestal foundation should correspond to both ends of the test beam, and the reaction frame foundation should correspond to the middle of the test beam. Embedded parts should be symmetrically installed on the upper surface of the reaction frame foundation on both sides of the length of the test beam. A through groove should be opened in the middle of the upper surface of the pedestal foundation and the reaction frame foundation, respectively, along the length of the test beam.

[0011] S3. Install a track on the ground of the test site. The track passes through all the grooves in sequence to make a reaction frame. The reaction frame has a door-shaped structure.

[0012] S4. Two mobile platforms are arranged on the track at intervals corresponding to the pedestal foundations. Embedded parts are symmetrically installed on the upper surfaces of the mobile platforms on both sides of the length of the test beam. Support assemblies for supporting the test beam are connected through the embedded parts. A track transmission device is provided at the bottom of the mobile platforms. A lifting support device is provided on the track transmission device. The lifting range of the lifting support device for the mobile platforms includes the height of the upper surface of the pedestal foundation. The test beam is erected on the top of the two mobile platforms. The test beam is carried by the track transmission device until each mobile platform moves to the top of a pedestal foundation.

[0013] S5. The lifting support device drives the mobile pedestal to descend so that the mobile pedestal is fully supported on the upper surface of the pedestal foundation. The reaction frame is fixed. The reaction frame is set on the outer side of the middle part of the test beam. The bottom of each end of the reaction frame is fixed to the reaction frame foundation through embedded parts.

[0014] S6. Install the jack, pressure sensor, and distribution beam in order downwards between the bottom surface of the upper end of the reaction frame and the test beam;

[0015] S7. Arrange a data acquisition system on the test beam and conduct static and dynamic load tests to test the mechanical properties of old bridges with different degrees of damage;

[0016] S8. Unload the jack, dismantle the data acquisition system, and move the test beam out through the mobile pedestal;

[0017] S9. Repeat steps S5-S8 until all test beams are tested, dismantle the test instruments and equipment, and restore the site.

[0018] Preferably, the reaction frame comprises a pair of columns and a crossbeam connected between the tops of the pair of columns, and the bottoms of the columns are fixed to the reaction frame foundation through the embedded parts;

[0019] After obtaining the reaction frame in step S3, first fix the columns on the reaction frame foundation. After the test beam moves with the mobile pedestal to a position directly above the two pedestal foundations, install the crossbeam between a pair of columns, and then install the distribution beam, the pressure sensor, and the jack in step S6.

[0020] Preferably, bolt holes penetrating along the length direction of the test beam are provided at both ends of the crossbeam and the upper end of each column, and the crossbeam and the columns are connected by tightening bolts in the bolt holes.

[0021] Preferably, two groups of embedded parts are provided on the upper surface of the movable platform, wherein one group of embedded parts is provided in the middle of the movable platform, and the other group of embedded parts is symmetrically provided on the outer side of the middle of the movable platform, and the support assembly includes a support, a pair of diagonal braces, and a pair of web braces. The support is connected to the embedded part located in the middle, the width of the support is equal to the bottom width of the test beam, the bottom of the test beam is placed on the upper surface of the support, the web braces are used to be attached to the two side surfaces of the test beam, the lower end of the web brace is connected to the two sides of the support, the lower end of the diagonal brace is fixedly connected to the embedded part located on the outer side, and the upper end of the diagonal brace is fixedly connected to the upper end of the web brace on the corresponding side;

[0022] By arranging the support assembly, the position of the test beam is limited when the test beam is hung on the movable platform, and the end side and bottom of the test beam are supported.

[0023] Preferably, a flexible connector is provided between the two movable platforms, and the maximum extension length of the flexible connector is greater than the length of the test beam. When the two movable platforms are installed on the track, the flexible connector is used to protect them so that the spacing between the movable platforms does not exceed the limit.

[0024] Preferably, a pair of auxiliary positioning forks are provided in the middle of a pair of uprights of the reaction frame in the direction of the test beam, and a guide hole is respectively opened on the uprights in a longitudinal direction parallel to the cross beam, and the cross section of the guide hole is circular. After the mobile platform carries the test beam to the test area, the pair of auxiliary positioning forks are used to obtain the verticality of the current test beam relative to the reaction frame, and the auxiliary positioning forks include:

[0025] A crossbar is arranged to pass through the guide hole in the horizontal direction, a stopper is provided at one end of the crossbar facing the test beam, the size of the stopper is larger than the diameter of the guide hole, a sliding groove is provided at the upper part of the side wall of the crossbar at the end close to the test beam along the length direction, and an end of the crossbar away from the test beam passes through the corresponding column and is threadedly connected to a nut plate, and a side of the nut plate facing the test beam is used to abut against the corresponding surface of the column;

[0026] A lower limit rod is a horizontally arranged L-shaped rod, the shorter end of which is arranged along the radial direction of the crossbar and connected to the bottom of the stopper, and the longer end of which is arranged toward the test beam and connected to a lower pressure sensor at the end, which is used to contact the outer side of the belly of the test beam;

[0027] The upper limit rod is a horizontally arranged L-shaped rod. The upper limit rod and the lower limit rod are arranged opposite to each other and are located in the same radial plane of the cross bar. The shorter end of the upper limit rod extends into the slide groove and is slidably connected to the slide groove. A welded part is further provided between the shorter end of the upper limit rod and the cross bar. The longer end of the upper limit rod is arranged toward the test beam body and is connected to an upper pressure sensor at the end. The upper pressure sensor is used to contact the outer side of the belly of the test beam body.

[0028] According to the cross-sectional shape and size of the current test beam, the upper limit rod is slid along the slide groove so that the relative positions of the outer ends of the upper pressure sensor and the lower pressure sensor match the test beam. Then, the upper limit rod is fixed by welding, and then a pair of auxiliary adjustment forks are respectively inserted along the guide holes from the inside so that the spacing between the pair of auxiliary adjustment forks is greater than the belly cross-sectional width of the test beam. When the test beam arrives above the pedestal foundation and the reaction frame foundation along the movable pedestal, the pair of auxiliary adjustment forks are driven to move toward each other synchronously so that the spacing between the auxiliary adjustment forks is exactly consistent with the width of the corresponding position of the test beam. During this process, the lower pressure sensors and upper pressure sensors on both sides monitor the pressure data in real time. At the same time, the position of the test beam is fine-tuned until the central axis of the test beam in the longitudinal direction is consistent with the central axis of the pedestal foundation and the reaction frame foundation, and the pressure data of the lower pressure sensors on both sides are consistent, and the pressure data of the upper pressure sensors on both sides are consistent. Finally, the jacking support device is retracted and lowered until the test beam completely falls on the pedestal foundation and the reaction frame foundation.

[0029] The present invention has at least the following beneficial effects:

[0030] (1) The loading method of the present invention, which is applicable to static and dynamic load tests in old bridge sites, is used to locate the test area by setting a pedestal foundation and a reaction frame foundation at the test site before conducting the static and dynamic load tests. Tracks and a mobile pedestal are set to carry the test beam to the test area. The reaction frame is used to install the jack. The overall test site has few installation structures, a high degree of prefabrication, and small-volume components are easy to transport. The assembly process is simple and safe, and the operating space is large.

[0031] (2) The loading method of the present invention is suitable for static and dynamic load tests in old bridge sites. After the loading test of a beam body is completed, the current test beam body can be moved out by moving the pedestal, replaced with a new test beam body, and the connecting parts between the distribution beam, the jack, and the embedded parts are disassembled and replaced with new connecting parts, and then the test can be carried out again, and repeated testing is convenient.

[0032] (3) The loading method of the present invention, which is suitable for static and dynamic load tests in old bridge sites, is applicable to a wide range of beam forms and can meet the static and dynamic load test requirements of beams with various cross-sections such as T-shaped, I-shaped, and box-shaped beams by changing the positions of the movable pedestal, reaction frame, jack, and distribution beam.

[0033] (4) The present invention combines dynamic load tests with static load tests, and can obtain static and dynamic load test results in sequence, or perform static and dynamic load tests alternately, so as to obtain the static response and dynamic response of the structure under different damage degrees, thereby meeting diverse research needs.

[0034] Other advantages, objectives and features of the present invention will be reflected in part from the following description and will be understood by those skilled in the art through study and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the overall structure of the present invention after the test beam is transported to its place at the test site;

[0036] Figure 2 for Figure 1 AA view;

[0037] Figure 3 for Figure 2 BB view;

[0038] Figure 4 This is a schematic diagram of the structure of the test site arrangement before the test beam is transported in steps S1-S4 of the present invention;

[0039] Figure 5 This is a schematic structural diagram of the present invention driving the mobile platform before carrying the test beam and before receiving the test beam;

[0040] Figure 6 This is a schematic diagram of the structure of the mobile platform of the present invention when carrying the test beam;

[0041] Figure 7 This is a schematic diagram of the structure of the present invention when the test beam is transported to the pedestal foundation and the reaction frame foundation;

[0042] Figure 8 This is a side structural diagram of the auxiliary positioning harpoon provided at the reaction frame of the present invention;

[0043] Figure markings in the specification: 1. pedestal foundation, 2. reaction frame foundation, 3. test beam, 4. embedded parts, 5. track, 6. reaction frame, 7. mobile pedestal, 8. support assembly, 9. track transmission device, 10. jacking support device, 11. upper pad, 12. jack, 13. pressure sensor, 14. distribution beam, 15. lower pad, 16. support, 17. diagonal brace, 18. web brace, 19. column, 20. bolt hole, 21. cross beam, 22. auxiliary adjustment fork, 23. guide hole, 24. cross bar, 25. slide, 26. nut plate, 27. lower limit rod, 28. upper limit rod, 29. lower pressure sensor, 30. upper pressure sensor, 31. block, 32. weldment, 33. flexible connector. DETAILED DESCRIPTION

[0044] The present invention will be described in further detail below in conjunction with the accompanying drawings so that those skilled in the art can implement the invention with reference to the description.

[0045] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials are commercially available unless otherwise specified; in the description of the present invention, the terms "horizontal", "longitudinal", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation to the present invention.

[0046] like Figure 1-7 As shown, the present invention provides a loading method suitable for static and dynamic load tests in old bridge sites, comprising the following steps:

[0047] S1. Level the test site to ensure that the bearing capacity of the foundation meets the test requirements.

[0048] S2. Combination Figure 4 As shown, a pedestal foundation 1 and a reaction frame foundation 2 are cast in the test site. The upper surfaces of the pedestal foundation 1 and the reaction frame foundation 2 are flush with the ground. The pedestal foundation 1 is arranged corresponding to the two ends of the test beam 3, and the reaction frame foundation 2 is arranged corresponding to the middle of the test beam 3. Embedded parts 4 are symmetrically installed on both sides of the upper surface of the reaction frame foundation 2 in the length direction of the test beam 3 to facilitate the subsequent installation of other components. A through groove is opened in the middle of the upper surface of the pedestal foundation 1 and the reaction frame foundation 2 along the length direction of the test beam 3.

[0049] S3. Combination Figure 4As shown, track 5 is installed on the ground of the test site, passing through all grooves in sequence to form a reaction frame 6. The reaction frame 6 has a gate-shaped structure and ensures that the bearing capacity of the reaction frame 6 meets the test loading requirements. The length of track 5 is set long enough to allow the test beam 3 to move in and out from different directions. Corresponding grooves are opened in the ground of the non-pedestal foundation 1 and the reaction base foundation to facilitate the installation of track 5. Multiple parallel tracks can be set according to the site conditions and the width of the test beam. The grooves are set according to the track conditions to jointly support the piggyback transportation.

[0050] S4. Combination Figure 4-6 As shown, two mobile pedestals 7 are set on the track 5 at a distance corresponding to the pedestal foundation 1. The upper surface of the mobile pedestal 7 is symmetrically installed with embedded parts 4 on both sides of the length direction of the test beam 3, and a support assembly 8 for supporting the test beam 3 is connected through the embedded parts 4. A track transmission device 9 is provided at the bottom of the mobile pedestal 7. The track transmission device 9 is a similar structure such as a driving wheel. It only needs to be able to drive and walk on the track 5. A jacking support device 10 is provided on the track transmission device 9. The jacking support device 10 is a structure such as a jacking cylinder and a jack 12. The jacking range of the mobile pedestal 7 by the jacking support device 10 includes the height of the upper surface of the pedestal foundation 1. The test beam 3 is erected on the top of the two mobile pedestals 7. The test beam 3 is carried by the track transmission device 9, so that each mobile pedestal 7 travels to the top of a pedestal foundation 1, that is, moves to the test area.

[0051] S5. Combination Figure 7 As shown, the jacking support device 10 drives the movable pedestal 7 to descend so that the movable pedestal 7 is fully supported on the upper surface of the pedestal foundation 1. At this time, the test position of the test beam 3 is determined, and the reaction frame 6 is fixed. The reaction frame 6 is framed on the outer side of the middle part of the test beam 3, and the bottoms of both ends of the reaction frame 6 are respectively fixed to the reaction frame foundation 2 through embedded parts 4.

[0052] S6. Combination Figure 1 、 Figure 7 As shown, an upper pad 11, a jack 12, a pressure sensor 13, a distribution beam 14, and a lower pad 15 are installed downward in sequence between the upper bottom surface of the reaction frame 6 and the test beam body 3. The upper pad 11 is set between the jack 12 and the upper bottom surface of the reaction frame 6, and the lower pad 15 is set between the distribution beam 14 and the test beam body 3. The distribution beam 14 is set along the length direction of the test beam body 3. The bottom of the pressure sensor 13 is in contact with the upper surface of the distribution beam 14, and the load is applied downward to the test beam body 3 through the jack 12.

[0053] S7. Arrange the data acquisition system on the test beam 3, implement static and dynamic load tests, and test the mechanical properties of old bridges with different degrees of damage. Static and dynamic load tests are commonly used test items in this field. The specific process and equipment setting method will not be repeated here. The data acquisition system can use a conventional acquisition module sensor + display terminal. When conducting a dynamic load test, an exciting force is applied to the specimen. Under this excitation, the vibration signal generated by the specimen is captured by the acceleration sensor fixed on the surface of the beam and recorded by the data acquisition system. After modal analysis, the dynamic characteristics of the model under different damage conditions are determined. The test items include: the first three natural frequencies, damping ratio and vibration mode. Implement a static load test, test: load the test specimen step by step, and collect stress, strain, deflection, and crack test data at the same time until the specimen reaches the bearing capacity limit state, then terminate the loading.

[0054] S8. After the static and dynamic load tests corresponding to the current test beam 3 are completed, the jack 12 is unloaded, the data acquisition system is removed, and the test beam 3 is moved out of the test beam 3 via the mobile platform 7. The current mobile platform 7 is moved out of the current test beam 3, and the next pair of mobile platforms 7 are operated to connect to the next beam 3 to be tested, thereby improving test efficiency.

[0055] S9. Repeat steps S5-S8 until all test beams 3 are tested, dismantle the test instruments and equipment, and restore the site.

[0056] The loading method of the present invention, which is applicable to static and dynamic load tests in old bridge sites, is used to locate the test area by setting a pedestal foundation 1 and a reaction frame foundation 2 at the test site before conducting the static and dynamic load tests, and then setting a track 5 and a mobile pedestal 7 to carry the test beam 3 to the test area. The mobile pedestal 7 has the functions of carrying the test beam 3 and limiting the support of the beam in the static and dynamic load tests. After being carried into place, the reaction frame 6 is used to install the jack 12. The overall test site installation structure is small, the number of reaction frames 6 is small, the prefabrication degree is high, the small volume components are easy to transport, and the assembly is convenient. The installation process is simple and safe, the operation space is large, and repeated tests are convenient. After the loading test of a beam is completed, the current test beam 3 can be removed, and the new test piece can be replaced before the test can be repeated. The distribution beam 14, prestressed steel bundle and jack 12, and the connectors between the embedded parts 4 are disassembled and replaced with the new test beam 3 and connectors, and the test can be repeated. It has strong applicability and can meet the static and dynamic load test requirements of beams with various cross-sections such as T-shaped, I-shaped, and box-shaped by changing the position of the movable platform 7, reaction frame 6, jack 12, and distribution beam 14. This method combines dynamic load testing with static load testing, and can obtain static and dynamic load test results in sequence, or perform static and dynamic load tests alternately, so as to obtain the static response and dynamic response of the structure under different damage levels and meet diverse research needs.

[0057] In another technical solution, Figure 1 、3 As shown in FIG. 8 , the reaction frame 6 includes a pair of columns 19 and a crossbeam 21 connected between the tops of the pair of columns 19 , and the bottoms of the columns 19 are fixed to the reaction frame foundation 2 through the embedded parts 4 ;

[0058] After obtaining the reaction frame 6 in step S3, first fix the column 19 on the reaction frame foundation 2. After the test beam 3 moves with the mobile platform 7 to the position directly above the two platform foundations 1, install the crossbeam 21 between a pair of columns 19, and then install the distribution beam 14, the pressure sensor 13, and the jack 12 in step S6.

[0059] By setting the reaction frame 6 in a detachable connection form, the convenience of on-site installation and disassembly is improved. First, after fixing the column 19, when the mobile platform 7 carries the test beam 3 through the reaction frame 6, it plays a certain limiting role, which is conducive to adjusting the position and moving direction of the mobile platform 7. After the test beam 3 is moved into place, the crossbeam 21 of the reaction frame 6 is fixed. When the test beam 3 needs to be moved out, it can be directly moved out through the mobile platform 7, or the crossbeam 21 can be removed according to the status of the on-site construction site, and the tested beam 3 can be carried or lifted, or transferred to other construction sites for reuse, thereby reducing the installation and disassembly process.

[0060] In another technical solution, Figure 3 、 8 As shown, bolt holes 20 are respectively provided at both ends of the crossbeam 21 and the upper end of each column 19 , which pass through the length direction of the test beam body 3 . The crossbeam 21 and the columns 19 are connected by tightening bolts in the bolt holes 20 .

[0061] Before the test beam 3 is moved to the bottom of the reaction frame 6, the crossbeam 21 is rotated in the vertical plane around the bolt hole 20 of one of the columns 19. After the test beam 3 is moved into place, the crossbeam 21 is fastened to the top of the column 19 with bolts. By setting up the bolt connection, the crossbeam 21 can rotate around the column 19 when the bolts are loosened, which facilitates installation and removal and reduces the number of welding times.

[0062] In another technical solution, Figure 1-3As shown, two groups of embedded parts 4 are provided on the upper surface of the movable platform 7, wherein one group of embedded parts 4 is provided in the middle of the movable platform 7, and the other group of embedded parts 4 is symmetrically provided on the outer side of the middle of the movable platform 7. The support assembly 8 includes a support 16, a pair of diagonal braces 17, and a pair of web braces 18. The support 16 is connected to the embedded part 4 located in the middle, and the width of the support 16 is equal to the bottom width of the test beam 3. The bottom of the test beam 3 is placed on the upper surface of the support 16. The web brace 18 is used to be attached to the two side surfaces of the test beam 3. The lower end of the web brace 18 is connected to both sides of the support 16, the lower end of the diagonal brace 17 is fixedly connected to the embedded part 4 located on the outer side, and the upper end of the diagonal brace 17 is fixedly connected to the upper end of the web brace 18 on the corresponding side.

[0063] By providing the support assembly 8, the test beam 3 is limited in position when it is hoisted onto the mobile platform 7, and the end sides and bottom of the test beam 3 are supported. When the test beam 3 is placed on the two mobile platforms 7, the two support assemblies 8 align the limited test beam 3, quickly locking the position of the test beam 3 relative to the mobile platform 7, facilitating subsequent test operations and preventing the position of the test beam 3 from shifting during transportation. The position of the support assembly 8 can be replaced or adjusted according to the different cross-sectional forms of the beam.

[0064] In another technical solution, Figure 4-6 As shown, a flexible connector 33 is provided between the two movable platforms 7. The maximum extension length of the flexible connector 33 is greater than the length of the test beam 3. When the two movable platforms 7 are installed on the track 5, the flexible connector 33 is used for protection so that the spacing between the movable platforms 7 does not exceed the limit.

[0065] By providing a flexible connection between the movable bases 7, a protective effect is achieved, thereby improving safety during installation and transportation.

[0066] In another technical solution, Figure 8 As shown, a pair of auxiliary positioning forks 22 are provided in the middle of a pair of uprights 19 of the reaction frame 6 in the direction toward the test beam 3. A guide hole 23 is respectively opened on the uprights 19 along the length direction parallel to the crossbeam 21. The cross section of the guide hole 23 is circular. After the mobile platform 7 carries the test beam 3 to the test area, the pair of auxiliary positioning forks 22 are used to obtain the verticality of the current test beam 3 relative to the reaction frame 6. The auxiliary positioning forks 22 include:

[0067] A crossbar 24 is provided horizontally through the guide hole 23. A stopper 31 is provided at one end of the crossbar 24 facing the test beam 3. The size of the stopper 31 is larger than the diameter of the guide hole 23. A sliding groove 25 is provided along the length direction of the side wall of the crossbar 24 at the upper part of the end close to the test beam 3. The end of the crossbar 24 away from the test beam 3 passes through the corresponding column 19 and is threadedly connected to a nut plate 26. The side of the nut plate 26 facing the test beam 3 is used to abut against the corresponding surface of the column 19.

[0068] The lower limit rod 27 is a horizontal L-shaped rod. The shorter end of the lower limit rod 27 is arranged along the radial direction of the cross bar 24 and connected to the bottom of the stopper 31. The longer end of the lower limit rod 27 is arranged toward the test beam 3 and is connected to a lower pressure sensor 29 at the end. The lower pressure sensor 29 is used to contact the outer side of the belly of the test beam 3.

[0069] An upper limit rod 28 is a horizontally arranged L-shaped rod. The upper limit rod 28 and the lower limit rod 27 are arranged opposite each other and are located in the same radial plane of the cross bar 24. The shorter end of the upper limit rod 28 extends into the slide groove 25 and is slidably connected to the slide groove 25. A weldment 32 is further provided between the shorter end of the upper limit rod 28 and the cross bar 24. The longer end of the upper limit rod 28 is arranged toward the test beam 3 and is connected to an upper pressure sensor 30 at the end. The upper pressure sensor 30 is used to contact the outer side of the belly of the test beam 3;

[0070] According to the cross-sectional shape and size of the current test beam 3, the upper limit rod 28 is slid along the slide groove 25 so that the relative positions of the outer ends of the upper pressure sensor 30 and the lower pressure sensor 29 match the test beam 3, and then the upper limit rod 28 is fixed by the welding piece 32. Then, a pair of auxiliary adjustment forks 22 are respectively passed through the guide holes 23 from the inside, so that the spacing between the pair of auxiliary adjustment forks 22 is greater than the cross-sectional width of the belly of the test beam 3. When the test beam 3 arrives above the pedestal foundation 1 and the reaction frame foundation 2 with the moving pedestal 7, the pair of auxiliary adjustment forks 22 are driven to move synchronously toward each other, so that the auxiliary adjustment forks 22 are 2 is exactly consistent with the width of the corresponding position of the test beam 3. During this process, the lower pressure sensors 29 and the upper pressure sensors 30 on both sides monitor the pressure data in real time. At the same time, the position of the test beam 3 is fine-tuned until the central axis of the test beam 3 in the length direction is consistent with the central axis of the pedestal foundation 1 and the reaction frame foundation 2, and the pressure data of the lower pressure sensors 29 on both sides are consistent, and the pressure data of the upper pressure sensors 30 on both sides are consistent. Finally, the jacking support device 10 is retracted and lowered until the test beam 3 completely falls on the pedestal foundation 1 and the reaction frame foundation 2.

[0071] By setting a pair of auxiliary adjustment harpoons, the position of the test beam 3 can be fine-tuned after the test beam 3 reaches the test area, so as to avoid torque and other conditions in the subsequent static and dynamic load tests. The auxiliary adjustment harpoons have a simple structure and are easy to install and disassemble. An external thread is set on the surface of the end of the cross bar 24 away from the test beam 3. The cross bar 24 can be temporarily fixed by screwing the nut plate 26 on the outside of the column 19 onto the cross bar 24. The cross bar 24 moves axially along the guide hole 23 and can be adjusted to the position of the outer end of the upper limit rod 28 and the lower limit rod 27, which is convenient for installation and can It can adapt to beams of different cross-sectional shapes. Since the cross-sections of the guide hole 23 and the crossbar 24 are set to be circular, the crossbar 24 can also rotate relative to the guide hole 23, further improving the adaptability of the auxiliary positioning harpoon to different shapes and positions. The guide hole 23 can be adjusted to the height on the column 19 according to the required position, or multiple holes can be set at intervals along the length of the column 19. When the data of the upper pressure sensor 30 and the lower pressure sensor 29 at the same level on the left and right are equal, it indicates that the test beam 3 is in a good test state. The two ends of the test beam 3 are supported by the support assembly 8, and the auxiliary positioning harpoon structure is set on the reaction frame foundation 2 and the reaction frame 6 in the middle, which reduces the adjustment range of the test beam 3 and is also conducive to mastering the force balance state of the test beam 3.

[0072] Although the embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the description and implementation methods. They can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and illustrations shown and described herein.

Claims

1. A loading method suitable for static and dynamic load tests in old bridge sites, characterized in that: The steps include: S1. Level the test site to ensure that the bearing capacity of the foundation meets the test requirements; S2. Construct a pedestal foundation and a reaction frame foundation at the test site. The upper surfaces of the pedestal foundation and the reaction frame foundation should be flush with the ground. The pedestal foundation should correspond to both ends of the test beam, and the reaction frame foundation should correspond to the middle of the test beam. Embedded parts should be symmetrically installed on the upper surface of the reaction frame foundation on both sides of the length of the test beam. A through groove should be opened in the middle of the upper surface of the pedestal foundation and the reaction frame foundation, respectively, along the length of the test beam. S3. Install a track on the ground of the test site. The track passes through all the grooves in sequence to make a reaction frame. The reaction frame has a door-shaped structure. S4. Two mobile platforms are arranged on the track at intervals corresponding to the pedestal foundations. Embedded parts are symmetrically installed on the upper surfaces of the mobile platforms on both sides of the length of the test beam. Support assemblies for supporting the test beam are connected through the embedded parts. A track transmission device is provided at the bottom of the mobile platforms. A lifting support device is provided on the track transmission device. The lifting range of the lifting support device for the mobile platforms includes the height of the upper surface of the pedestal foundation. The test beam is erected on the top of the two mobile platforms. The test beam is carried by the track transmission device until each mobile platform moves to the top of a pedestal foundation. Two groups of embedded parts are provided on the upper surface of the movable platform, wherein one group of embedded parts is provided in the middle of the movable platform, and the other group of embedded parts is symmetrically provided on the outer side of the middle of the movable platform. The support assembly includes a support, a pair of diagonal braces, and a pair of web braces. The support is connected to the embedded part located in the middle, the width of the support is equal to the bottom width of the test beam, the bottom of the test beam is placed on the upper surface of the support, the web brace is used to be attached to the two side surfaces of the test beam, the lower end of the web brace is connected to the two sides of the support, the lower end of the diagonal brace is fixedly connected to the embedded part located on the outer side, and the upper end of the diagonal brace is fixedly connected to the upper end of the web brace on the corresponding side; By setting the support assembly, the test beam is limited when it is hung on the movable platform, and the end side and bottom of the test beam are supported; S5. The lifting support device drives the mobile pedestal to descend so that the mobile pedestal is fully supported on the upper surface of the pedestal foundation. The reaction frame is fixed. The reaction frame is set on the outer side of the middle part of the test beam. The bottom of each end of the reaction frame is fixed to the reaction frame foundation through embedded parts. S6. Install the jack, pressure sensor, and distribution beam in order downwards between the bottom surface of the upper end of the reaction frame and the test beam; S7. Arrange a data acquisition system on the test beam and conduct static and dynamic load tests to test the mechanical properties of old bridges with different degrees of damage; S8. Unload the jack, dismantle the data acquisition system, and move the test beam out through the mobile pedestal; S9. Repeat steps S5-S8 until all test beams are tested, dismantle the test instruments and equipment, and restore the site.

2. The loading method for static and dynamic load tests in old bridge sites as claimed in claim 1, characterized in that: The reaction frame includes a pair of columns and a crossbeam connected between the tops of the pair of columns, and the bottoms of the columns are fixed to the reaction frame foundation through the embedded parts; After obtaining the reaction frame in step S3, first fix the columns on the reaction frame foundation. After the test beam moves with the mobile pedestal to a position directly above the two pedestal foundations, install the crossbeam between a pair of columns, and then install the distribution beam, the pressure sensor, and the jack in step S6.

3. The loading method for static and dynamic load tests in old bridge sites as claimed in claim 2, characterized in that: Bolt holes penetrating along the length direction of the test beam are respectively provided at both ends of the crossbeam and the upper end of each column. The crossbeam and the columns are connected by tightening bolts in the bolt holes.

4. The loading method for static and dynamic load tests in old bridge sites as claimed in claim 1, characterized in that: A flexible connector is provided between the two movable platforms. The maximum extension length of the flexible connector is greater than the length of the test beam. When the two movable platforms are installed on the track, the flexible connector is used for protection so that the spacing between the movable platforms does not exceed the limit.

5. The loading method for static and dynamic load tests in old bridge sites as claimed in claim 2, characterized in that: A pair of auxiliary positioning forks are provided in the middle of a pair of upright posts of the reaction frame in the direction of the test beam. A guide hole is respectively opened on the upright posts along the length direction parallel to the cross beam. The cross section of the guide hole is circular. After the mobile platform carries the test beam to the test area, the pair of auxiliary positioning forks are used to obtain the verticality of the current test beam relative to the reaction frame. The auxiliary positioning forks include: A crossbar is arranged to pass through the guide hole in the horizontal direction, a stopper is provided at one end of the crossbar facing the test beam, the size of the stopper is larger than the diameter of the guide hole, a sliding groove is provided at the upper part of the side wall of the crossbar at the end close to the test beam along the length direction, and an end of the crossbar away from the test beam passes through the corresponding column and is threadedly connected to a nut plate, and a side of the nut plate facing the test beam is used to abut against the corresponding surface of the column; A lower limit rod is a horizontally arranged L-shaped rod, the shorter end of which is arranged along the radial direction of the crossbar and connected to the bottom of the stopper, and the longer end of which is arranged toward the test beam and connected to a lower pressure sensor at the end, which is used to contact the outer side of the belly of the test beam; The upper limit rod is a horizontally arranged L-shaped rod. The upper limit rod and the lower limit rod are arranged opposite to each other and are located in the same radial plane of the cross bar. The shorter end of the upper limit rod extends into the slide groove and is slidably connected to the slide groove. A welded part is further provided between the shorter end of the upper limit rod and the cross bar. The longer end of the upper limit rod is arranged toward the test beam body and is connected to an upper pressure sensor at the end. The upper pressure sensor is used to contact the outer side of the belly of the test beam body. According to the cross-sectional shape and size of the current test beam, the upper limit rod is slid along the slide groove so that the relative positions of the outer ends of the upper pressure sensor and the lower pressure sensor match the test beam. Then, the upper limit rod is fixed by welding, and then a pair of auxiliary adjustment forks are respectively inserted along the guide holes from the inside so that the spacing between the pair of auxiliary adjustment forks is greater than the belly cross-sectional width of the test beam. When the test beam arrives above the pedestal foundation and the reaction frame foundation along the movable pedestal, the pair of auxiliary adjustment forks are driven to move toward each other synchronously so that the spacing between the auxiliary adjustment forks is exactly consistent with the width of the corresponding position of the test beam. During this process, the lower pressure sensors and upper pressure sensors on both sides monitor the pressure data in real time. At the same time, the position of the test beam is fine-tuned until the central axis of the test beam in the longitudinal direction is consistent with the central axis of the pedestal foundation and the reaction frame foundation, and the pressure data of the lower pressure sensors on both sides are consistent, and the pressure data of the upper pressure sensors on both sides are consistent. Finally, the jacking support device is retracted and lowered until the test beam completely falls on the pedestal foundation and the reaction frame foundation.

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