Plate-type pull-out test device and vehicle-induced vibration simulation test method based on the device

Abstract

The invention relates to the technical field of concrete model test devices, and in particular to a plate-type pull-out test device and a vehicle-induced vibration simulation test method based on the device; in the vehicle-induced vibration simulation test method of the invention, a plurality of pull-out steel bars are buried in parallel in the beam and slab by prefabricating beams and slabs, a protective sleeve is provided in the pull-out steel bars in the first-casting section area, and a low-melting-point slurry is poured in the protective sleeve, and after the vibration test is completed, the low-melting-point slurry is melted and discharged from the beam and slab, so that a mode of independent connection between the pull-out steel bars and the later-casting section is formed, in which case, a bonding strength test is performed to eliminate the influence of the first-casting section on the later-casting section, thereby ensuring the accuracy of the test result, and after the low-melting-point slurry is solidified, the relative displacement of the steel bars and the concrete of the first-casting section is limited, thereby avoiding the displacement of the steel bars in the first-casting section due to less constraints on the steel bars, thereby solving the problem of distortion of the test result caused by the non-perpendicularity between the steel bars and the concrete of the test component under a vibration environment.

Description

Technical Field

[0001] The invention relates to the technical field of concrete model test devices, in particular to a plate-type pull-out test device and a vehicle-induced vibration simulation test method based on the device. Background Art

[0002] In recent years, there are more and more bridge widening projects. When widening bridges, traffic on old bridges is often not interrupted, and wet joints are used to connect old bridges and new bridges. During the pouring of wet joints, the vibration of the old bridge will affect the mechanical properties of the joint concrete, and the vehicle-induced vibration will cause displacement differences between the steel bars and concrete in the wet joints.

[0003] The existing simulation test is often to pour concrete in a cubic test mold with the steel bars to be pulled out embedded in advance, and then place it on a vibration table for vibration after pouring. After 24 hours of vibration, the vibration table is turned off, and the steel bars are pulled out after reaching the test age and curing is completed, and the test machine readings are recorded. In the actual bridge widening project, there is a displacement difference between the steel bars and the concrete during the vibration process when the wet joints are just poured, but the existing simulation test method cannot simulate this displacement difference between the steel bars and the concrete. In addition, the force of the concrete test block is very different from the force of the wet joints of the actual bridge. When the actual bridge is widened, the wet joints have a large tensile stress under the vehicle-induced vibration conditions, and the wet joints may crack. However, in the existing test method, when the cubic test block is vibrated, there is no tensile stress in the cubic test block, and the test block will not crack. In addition, due to the small size of the concrete, the steel bars are subject to small constraints, which easily leads to a large degree of inclination of the steel bars during the vibration process. Therefore, it is urgent to improve the existing test specimens and test methods for reinforced concrete pull-out tests under simulated vehicle-induced vibration environments. Summary of the invention

[0004] The purpose of the present invention is to provide a plate-type pull-out test device and a vehicle-induced vibration simulation test method based on the device to address the problem that in the prior art, during the test process of simulating vehicle-induced vibration, the test block of the pull-out test cannot simulate the environment of vehicle-induced vibration well, resulting in the simulation result and the simulation data being of no reference value.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A plate-type pull-out test device comprises a prefabricated test beam and a group of vibration tables arranged below the prefabricated test beam; the prefabricated test beam is divided into a first precast section, a post-cast section and a second precast section in sequence along its width direction, the vibration table comprises a first vibration table and a second vibration table, the first vibration table is arranged below the first precast section, and the second vibration table is arranged below the second precast section; in the prefabricated test beam, a plurality of pull-out steel bars are arranged in parallel perpendicular to the length direction of the post-cast section, and both ends of each of the pull-out steel bars respectively penetrate into the interior of the precast section on both sides of the post-cast section; the pull-out steel bars located inside the precast section are respectively provided with protective sleeves, and an isolation layer is provided inside the sleeves.

[0007] The present invention proposes a prefabricated test beam and slab, and fixes the beam and slab to a vibration table. In the process of burying drawn steel bars in the beam and slab, multiple drawn steel bars are arranged in parallel, and a protective sleeve is provided in the drawn steel bars in the first pouring section area. An isolation layer is formed by pouring a low-melting point slurry in the protective sleeve. After the vibration test is completed, the low-melting point slurry is melted and discharged from the beam and slab, forming a way of independent connection between the drawn steel bars and the post-casting section, which largely restores the stress condition of wet joint concrete during the widening of the actual bridge, and can reflect the comprehensive influence of different deflection differences of the wet joint along the length direction of the post-casting section on the bond strength between the steel bars and the wet joint concrete. The obtained data is more comprehensive, and the stress condition of the wet joint concrete during the widening of the actual bridge is simulated and restored from multiple angles, which provides more appropriate opinions and more reliable data support for the implementation of the later bridge construction work.

[0008] As a preferred technical solution of the present invention, the prefabricated test beam and slab are nested in a beam and slab mold, which is a rectangular shell. The beam and slab mold is composed of a bottom plate, a first side plate and a second side plate, respectively. The first side plates are relatively arranged at the two ends of the test beam and slab (fitting the two ends of the post-cast section on the beam and slab); the second side plates are respectively arranged along the length direction of the first cast section; the first side plate on each side includes three independently arranged plates, which correspond to two first cast sections and one post-cast section respectively; the bottom plate also includes three independently arranged plates, and the three independently arranged plates correspond to the first cast section and the post-cast section respectively; the relatively arranged second side plates correspond to the side faces of the first cast section; a partition plate for dividing the post-cast section is also arranged in the rectangular shell.

[0009] As a preferred technical solution of the present invention, it also includes a contour reinforcement strip, which is arranged on the beam and slab mold located at the post-casting section;

[0010] The contour reinforcement strip comprises a first reinforcement strip and a second reinforcement strip, the first reinforcement strip and the second reinforcement strip are laid vertically and horizontally on the bottom plate, the first reinforcement strip is a long side strip, the second reinforcement strip is a short side strip, and the second reinforcement strip is detachably connected to the first reinforcement strip;

[0011] It also includes a third reinforcement bar, which is arranged on the first side panel. The third reinforcement bar is arranged at intervals along the width direction of the first side panel, and the third reinforcement bar is detachably connected to the first reinforcement bar.

[0012] As a preferred technical solution of the present invention, one end of the drawn steel bar is flush with the side wall of the first first cast section, and the other end of the drawn steel bar extends out of the side wall of the second first cast section by 40-60 cm.

[0013] As a preferred technical solution of the present invention, a plurality of screw rods are passed through the first cast-in-place section and the second precast section in the vertical direction, one end of the screw rod is fixed to the top surface of the vibration table, and the other end of the screw rod is fixed by a limit bolt.

[0014] As a preferred technical solution of the present invention, the protective sleeve is made of PVC material; the diameter range of the protective sleeve 9 is 3-6 mm larger than the diameter of the steel bar, and the diameter range of the steel bar is 12-20 mm.

[0015] As a preferred technical solution of the present invention, the isolation layer is formed by condensing a low-melting-point slurry, the components of the low-melting-point slurry include epoxy resin, and the melting point range of the low-melting-point slurry is 58°C-80°C.

[0016] A vehicle-induced vibration simulation test method based on a plate-type pull-out test device, characterized in that it comprises the following steps:

[0017] Step 1: Collect data by installing several vibration pickups under the target bridge to collect bridge vibration curves under different vehicle conditions; then establish a finite element model of the old bridge;

[0018] Step 2, adjust the simulation test device; the first pre-cast section is used to simulate the old bridge side, the second pre-cast section is used to simulate the new bridge side; the post-cast section is used to simulate the wet joint; pour concrete into the post-cast section, and immediately start the first vibration table after the concrete pouring is completed;

[0019] Step 3: When the concrete in the post-casting section reaches final setting, all first vibration tables are closed; the test beam and slab are separated from the vibration table, and the formwork on the test beam and slab is demolded, and then the bonding strength between the steel bars and the post-casting section concrete of the test beam and slab is tested.

[0020] As a preferred technical solution of the present invention, in step 3, the bonding strength test is carried out according to the following steps: the disassembled test beam and slab is heated to melt the slurry poured into the protective sleeve and flow out, and a test device is installed on the pulled steel bars on one side of the test beam and slab for testing.

[0021] The testing device includes a pair of jacks, sensors and a fixing device; the fixing device includes a steel beam plate and a positioning anchor. The steel beam plate is provided with a through hole. The jacks are placed on both sides of the drawn steel bars to be tested, and sensors are installed on the ends of each jack. The steel beam plate is sleeved on the drawn steel bars and fixed at a specific position by the positioning anchor. The jacks can then be turned on for testing.

[0022] As a preferred technical solution of the present invention, the method for preparing the prefabricated beam slab comprises the following steps:

[0023] Step S1, building a beam-slab mold, the beam-slab mold is a rectangular shell, three rectangular sub-areas are divided in the same direction in the rectangular shell, the three rectangular sub-areas are the first pre-casting area, the post-casting area and the second pre-casting area in sequence, the three rectangular sub-areas are independent of each other, the three rectangular sub-areas correspond to the first pre-casting section, the post-casting section and the second pre-casting section of the test beam-slab respectively, the post-casting area and the pre-casting areas adjacent to both ends are provided with partition plates, the template corresponding to each rectangular sub-area is detachably connected to the template of the adjacent area; the templates corresponding to adjacent rectangular sub-areas are detachably connected; a steel cage is provided in the beam-slab mold, and the size of the steel cage is adapted to the rectangular shell;

[0024] Step S2, arranging a plurality of drawn steel bars in the beam and slab mold, each of the drawn steel bars sequentially passing through the second pre-casting area, the post-casting area, and the first pre-casting area, and a protective sleeve is respectively sleeved on the same drawn steel bar at the positions of the first pre-casting area and the second pre-casting area, and the length of the protective sleeve is the same as the width of the corresponding pre-casting section; and a pouring channel is arranged on the tube wall of the protective sleeve;

[0025] The diameter of the drawn reinforcement corresponds to the diameter of the transverse reinforcement in the wet joints in actual bridge widening projects;

[0026] Step S3, in the first pre-casting area and the second pre-casting area, in the corresponding vibration table installation area, a plurality of screws are fixed, one end of the screw is fixed to the vibration table, and the other end extends out of the beam and slab mold; the plurality of screws are respectively arranged to avoid the protective sleeves;

[0027] Step S4, pouring low-melting-point slurry into the protective sleeve through the pouring channel to form an isolation layer between the protective sleeve and the drawn steel bar; then pouring concrete in the first first pouring area and the second first pouring area, and after the concrete in the first first pouring area and the second first pouring area is finally solidified, the screw is limited by a nut on the top surface of the solidified concrete to complete the prefabrication of the beam and slab.

[0028] After the slurry solidifies, two preliminary sections of concrete are poured to ensure that the drawn steel bars in the preliminary sections of concrete remain horizontal during the subsequent vibration process, and further ensure that the drawn steel bars are vertical during pulling.

[0029] The beam and slab prefabricated by the above method is fixed to the vibration table in advance by fixing the beam and slab mold, and the length of the multiple screws used for fixing is higher than the thickness of the beam and slab. After the first and second pre-casting areas are poured with concrete and cured until solidification, the screws are fixed to the top of the beam and slab through the screws. Compared with the method of drilling and fixing the beam and slab after pouring, this operation method can better adjust the position of the vibration table at the bottom of the pre-casting section. After the vibration table is positioned, it can be directly limited with the beam and slab mold. In this way, when the steel cage, drawing steel bars and other components are set later, their positions can be better coordinated based on the positions of the screws, and no conflict will occur. And the fixing effect is better.

[0030] As a preferred solution of the present invention, a steel cage is provided in the prefabricated test beam, the steel cage is composed of a plurality of longitudinal stirrups, and the volume of the steel cage is adapted to the volume of the beam and slab mold.

[0031] As a preferred embodiment of the present invention, the low melting point slurry comprises epoxy resin, and the melting point of the low melting point slurry ranges from 58° C. to 80° C. The low melting point slurry is placed in a container, the container cover is opened, the low melting point slurry is poured into the grouting hole, and then the slurry is waited for to solidify naturally.

[0032] In summary, due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0033] 1. In the vehicle-induced vibration simulation test method of the present invention, the beams and slabs are prefabricated and fixed to the vibration table in advance. In the process of burying the drawn steel bars in the beams and slabs, a plurality of drawn steel bars are arranged in parallel, and the drawn steel bars in the first-cast section area are sleeved with a protective sleeve, and the protective sleeve is poured with a low-melting point slurry. After the vibration test is completed, the low-melting point slurry is melted and discharged from the beams and slabs, thereby forming a way in which the drawn steel bars and the later-cast section are independently connected. In this case, when performing the bonding strength test, the influence of the first-cast section on the later-cast section can be excluded, thereby ensuring that the test results have nothing to do with the bond strength of the drawn steel bars in the concrete of the first-cast section, thereby ensuring the accuracy of the test results.

[0034] 2. The present invention arranges multiple tensile steel bars in parallel, and can test the bonding strength of post-cast sections at different positions through a beam slab. Compared with the conventional reinforced concrete beam tensile test device, this method shortens the test time and obtains more accurate bond strength data.

[0035] 3. The technical solution of the present invention restores the stress condition of wet joint concrete during the widening of an actual bridge to a large extent, and can reflect the comprehensive influence of different deflection differences of the wet joint along the length direction of the post-casting section on the bond strength between the steel bar and the wet joint concrete. The data obtained is more comprehensive, and the stress condition of wet joint concrete during the widening of an actual bridge is simulated and restored from multiple angles, providing more appropriate opinions and more reliable data support for the implementation of later bridge construction work. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the structure of the present invention;

[0037] Figure 2 It is a schematic diagram of the test structure of the present invention;

[0038] Figure 3 It is a structural schematic diagram of a plate-type pull-out test device;

[0039] Figure 4 It is a schematic diagram of the structure of the beam and slab mold viewed from above;

[0040] Figure 5 It is the curve of reinforcement stirring action along the length direction of reinforcement.

[0041] Icons: 1-first pouring section; 2-latter pouring section; 3-second pouring section; 4-first vibration table; 5-second vibration table; 6-beam and slab mold, 61-bottom plate, 62-first side plate, 63-second side plate, 13-third reinforcement bar, 15-first reinforcement bar, 16-second reinforcement bar; 8-pulled steel bars; 9-protective casing; 91-casting channel, 10-isolation layer; 11-jack, 12-sensor, 14-positioning anchor, 17-steel beam and slab. DETAILED DESCRIPTION

[0042] The present invention will be described in detail below in conjunction with the accompanying drawings.

[0043] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0044] Example 1

[0045] A plate pull test device, such as Figure 3As shown, it includes a prefabricated test beam and a group of vibration tables arranged below the prefabricated test beam; the prefabricated test beam is divided into a first precast section 1, a post-cast section 2 and a second precast section 3 in sequence along its width direction, and the vibration table includes a first vibration table 4 and a second vibration table 5, the first vibration table 4 is arranged below the first precast section 1, and the second vibration table 5 is arranged below the second precast section 3; in the prefabricated test beam, a plurality of drawn steel bars 8 are arranged in parallel perpendicular to the length direction of the post-cast section, and both ends of each drawn steel bar 8 are respectively passed through the inside of the precast section on both sides of the beam; the drawn steel bars 8 located inside the precast section are respectively provided with protective sleeves 9, and an isolation layer 10 is provided inside the protective sleeves 9.

[0046] Specifically, the prefabricated test beam plate is nested in the beam plate mold 6, and the beam plate mold 6 is a rectangular shell, such as Figure 4 As shown, the beam-slab mold 6 is respectively composed of a bottom plate 61, a first side plate 62 and a second side plate 63, wherein the first side plates 62 are relatively arranged at the two ends of the test beam-slab; the second side plates 63 are respectively arranged along the length direction of the first pouring section; the first side plate 62 on each side includes three independently arranged plates, which correspond to two first pouring sections and one later pouring section respectively; the bottom plate 61 also includes three independently arranged plates, which correspond to the first pouring section and the later pouring section respectively; the second side plates 63 which are relatively arranged correspond to the side faces of the first pouring section; a partition plate for dividing the later pouring section is also arranged in the rectangular shell 6.

[0047] More specifically, the beam-slab mold 6 further includes a contour reinforcement strip, and the contour reinforcement strip is arranged on the beam-slab mold 6 located at the post-casting section;

[0048] The contour reinforcement strip includes a first reinforcement strip 15 and a second reinforcement strip 16, which are laid vertically and horizontally on the bottom plate 61, the first reinforcement strip 15 is a long side strip, the second reinforcement strip 16 is a short side strip, and the second reinforcement strip 16 is detachably connected to the first reinforcement strip 15; and also includes a third reinforcement strip 13, which is arranged on the first side plate 62, and the third reinforcement strip 13 is arranged at intervals along the width direction of the first side plate 62, and the third reinforcement strip 13 is detachably connected to the first reinforcement strip 15.

[0049] like Figure 1-2 As shown, one end of the drawn steel bar 8 is flush with the side wall of the first first cast section 1, and the other end of the drawn steel bar 8 extends out of the side wall of the second first cast section 3 by 40-60 cm.

[0050] A plurality of screw rods are passed through the first precast section 1 and the second precast section 3 in the vertical direction, one end of the screw rod is fixed to the top surface of the vibration table, and the other end of the screw rod is fixed by a limit bolt.

[0051] Specifically, the protective sleeve 9 is made of PVC; the inner diameter of the protective sleeve 9 corresponds to the diameter of the drawn steel bar 8; the protective sleeve 9 is made of PVC; the diameter range of the protective sleeve 9 is 3-6mm larger than the diameter of the steel bar, and the diameter range of the steel bar is 12-20mm. The isolation layer 10 is formed by condensing a low melting point slurry.

[0052] Example 2

[0053] A vehicle-induced vibration simulation test method based on a plate-type pull-out test piece comprises the following steps:

[0054] Step 1: Collect data. Install several vibration pickups under the target bridge to collect bridge vibration curves under different vehicle conditions. Then build a finite element model of the old bridge. Install vibration pickups at multiple points on the widened side of the bridge that has not been widened, and record the vibration time history curves of the test points at different vehicle speeds. Then build a finite element model of the old bridge, and calculate the maximum deflection of the old bridge on the widened side and the time history curve of the point under the vehicle-bridge coupling. The maximum deflection of the old bridge on the widened side calculated in this example is 5mm.

[0055] Step 2, adjust the simulation test device; wherein the first precast section 1 and the second precast section 3 of the precast test beam slab are both concrete slabs, and the middle post-cast section is in a state of not being cast;

[0056] The first pre-cast section 1 is used to simulate the old bridge side, and the second pre-cast section 3 is used to simulate the new bridge side; the post-cast section 2 is used to simulate the wet joint; concrete is poured into the post-cast section 2, and the first vibration table 4 is immediately turned on after the concrete pouring is completed;

[0057] In step 2, the preparation method of the prefabricated beam and slab is carried out according to the following steps:

[0058] Step 2.1, build a beam-slab mold 6, the beam-slab mold 6 is a rectangular shell, and three rectangular sub-areas are divided in the same direction in the rectangular shell 6, the three rectangular sub-areas are the first pre-casting area, the post-casting area and the second pre-casting area in turn, the three rectangular sub-areas are independent of each other, and the three rectangular sub-areas correspond to the first pre-casting section 1, the post-casting section 2 and the second pre-casting section 3 of the test beam-slab respectively, the post-casting area and the pre-casting areas adjacent to both ends are provided with partition plates, the template corresponding to each rectangular sub-area is detachably connected to the template of the adjacent area; the templates corresponding to adjacent rectangular sub-areas are detachably connected; a steel cage is provided in the beam-slab mold, and the size of the steel cage is adapted to the rectangular shell 6;

[0059] Step 2.2, a plurality of drawn steel bars 8 are arranged in the beam-slab mold, each of the drawn steel bars 8 is sequentially arranged to pass through the second pre-casting area, the post-casting area, and the first pre-casting area, and a protective sleeve 9 is respectively sleeved on the same drawn steel bar 8 at the positions of the first pre-casting area and the second pre-casting area, and the length of the protective sleeve 9 is the same as the width of the corresponding pre-casting section; a pouring channel 91 is arranged on the tube wall of the protective sleeve 9;

[0060] The diameter of the drawn reinforcement 8 corresponds to the diameter of the transverse reinforcement in the wet joint in the actual bridge widening project;

[0061] Step 2.3, in the first pre-casting area and the second pre-casting area, in the corresponding vibration table installation area, a plurality of screws are fixed, one end of the screw is fixed to the vibration table, and the other end extends out of the beam and slab mold; the plurality of screws are respectively arranged to avoid the protective sleeve 9;

[0062] Step 2.4, pouring low-melting-point slurry into the protective sleeve 9 through the pouring channel to form an isolation layer 10 between the protective sleeve 9 and the drawn steel bar 8; then pouring concrete in the first first pouring area and the second first pouring area, and after the concrete in the first first pouring area and the second first pouring area is finally solidified, the screw is limited by a nut on the top surface of the solidified concrete to complete the prefabrication of the beam and slab.

[0063] The prefabricated test beam is provided with a steel cage, which is composed of a plurality of longitudinal stirrups, and the volume of the steel cage is adapted to the volume of the beam and slab mold. The composition of the low-melting point slurry includes epoxy resin, and the melting point range of the low-melting point slurry is 58°C-80°C. Specifically, first purchase the low-melting point slurry in the container, then open the container cover, pour the low-melting point slurry into the grouting hole, and then wait for the slurry to solidify naturally.

[0064] Step 3, pour concrete into the area where the post-casting section is located. After the concrete pouring is completed, immediately turn on the first vibration table 4. When the concrete in the post-casting section reaches final setting, turn off all the first vibration tables 4; demould the formwork of the post-casting section 2 of the test beam and slab, and then disassemble the test beam and slab to test the bonding strength between the steel bars and the concrete of the post-casting section 2. If the vibration is performed by inputting a time history curve, the first vibration table 4 uses an electromagnetic vibration table that can input a time history curve. If the vibration is performed by a fixed amplitude, the first vibration table 4 uses a vibration table driven by an attached vibrator. The vibration of the first vibration table 4 simulates the deflection of the side of the old bridge close to the wet joint under the vehicle-bridge coupling in the actual bridge widening project.

[0065] In step 3, the bonding strength test is performed according to the following steps:

[0066] The disassembled test beam plate is heated to melt the slurry poured into the protective sleeve and flow out, and a test device is installed on the drawn steel bar on one side of the test beam plate for testing. The test device includes a pair of jacks 11, sensors and a fixing device; the fixing device is a steel beam plate 17 and a positioning anchor 14, and a through hole is opened on the steel beam plate 17. The jacks 11 are placed on both sides of the drawn steel bar to be tested, and sensors are installed at the ends of each jack 11. The steel beam plate 17 is sleeved on the drawn steel bar, and the steel beam plate 17 is fixed at a specific position by the positioning anchor, and the jacks 11 can be opened for testing.

[0067] Two jacks 11 and sensors 12 are symmetrically arranged between the steel beam and the concrete slab, and the force applied by the jacks 11 is slowly increased. When the reading of the jacks 11 no longer increases, the loading is stopped and the reading is recorded. The bonding strength between several other pulled steel bars 8 and the concrete of the post-casting section 2 is tested in the same way.

[0068] In the technical solution of the present invention, two precast sections are used to simulate the old bridge and the new bridge in the actual bridge widening project, and the postcast section simulates the wet joint in the actual bridge widening project. The deflection of the old bridge near the wet joint under the vehicle-bridge coupling effect is simulated by vibrating one precast section, and the new bridge is fixed by another precast section to simulate that no deflection is generated. The steel bars in the wet joint in the actual bridge widening project are simulated by the drawn steel bars arranged in the middle. The steel bars are continuous in the interface between the precast section and the postcast section so that the displacement of the steel bars at the interface is consistent with the concrete at the precast section when the postcast section is just poured. There may be a displacement difference between the concrete and the postcast section, thereby simulating the displacement difference between the steel bars and the concrete on the side of the wet joint near the old bridge in the actual bridge widening project.

[0069] The inner diameter of the protective sleeve 9 is close to the outer diameter of the drawn steel bar 8, so as to ensure that the drawn steel bar 8 can be reliably fixed in the first cast section. The drawn steel bar 8 can be kept horizontal in the first cast section concrete by pouring low melting point slurry, so that the steel bar is vertical when the specimen is drawn. After the concrete of the post-cast section 2 is poured, finally set, and vibrated, the low melting point slurry is heated and melted to achieve the process of drawing the steel bar 8 without bonding with the remaining first cast section concrete.

[0070] Comparative Example 1

[0071] A conventional pulling test device comprises a gripping force test block and a vibration table arranged below the test block; the vibration table is arranged below the vibration table.

[0072] Specifically, the bond strength test block is tied to the vibration table with hemp rope, and consists of a test mold, a test fixture, steel bars and a concrete test block. The test mold and test fixture are the same as those specified in the "Testing Procedure for Cement and Cement Concrete for Highway Engineering JTG 3420-2020" T0566-2020, and the steel bars are the steel bars used in the post-casting section when the actual bridge is widened. The size of the concrete test block is 150mm×150mm×150mm, and the concrete used is the same as the concrete material used when the actual bridge is widened.

[0073] A vehicle-induced vibration simulation test method based on a conventional pull-out test device comprises the following steps:

[0074] Step 1: Collect data. Install several vibration pickups under the target bridge to collect bridge vibration curves under different vehicle conditions. Then build a finite element model of the old bridge. Install vibration pickups at multiple points on the widened side of the bridge that has not been widened, and record the vibration time history curves of the test points at different vehicle speeds. Then build a finite element model of the old bridge, and calculate the maximum deflection of the old bridge on the widened side and the time history curve of the point under the vehicle-bridge coupling. The maximum deflection of the old bridge on the widened side calculated in this example is 5mm.

[0075] Step 2: Adjust the simulation test device. The preparation method of the bond strength test block is carried out according to the following steps:

[0076] Step 2.1. Brush the steel bars clean with a wire brush and wipe them with acetone or ethanol to remove rust and oil stains on the surface of the steel bars.

[0077] Step 2.2: Apply a thin layer of mineral oil inside the test mold.

[0078] Step 2.3: Place the test mold on the vibration table and tie it to the vibration table surface with hemp rope.

[0079] Step 3, pouring concrete into the test mold. After the concrete pouring is completed, the vibration table is immediately turned on, and the vibration table is turned off when the concrete in the post-casting section reaches final setting; the template of the test block is demolded, and then the bonding strength between the steel bar and the post-casting section concrete is tested.

[0080] In step 3, the bonding strength test is performed according to the following steps:

[0081] Remove the test block from the mold, put on the pad with a hole in the middle, and then install it into the fixture installed on the universal testing machine, so that the lower clamp of the universal testing machine can clamp the steel bars of the test piece firmly. Install the gauge fixing frame and the micrometer on the test piece, so that the end of the micrometer rod is vertically downward and in contact with the top surface of the steel bar that slightly extends out of the test piece surface. Before adding load, check whether the micrometer rod is in good contact with the top surface of the steel bar and whether the micrometer is flexible. After recording the initial reading of the micrometer, start the test machine and record the reading.

[0082] The bonding strength τ =3.35MPa measured under non-vibration conditions in Comparative Example 1, and the bonding strength τ =3.29MPa measured under vibration conditions, are reduced by 1.8% compared with the bonding strength under non-vibration conditions. The force F =84.74kN measured under non-vibration conditions in Example 2 to pull out the steel bars, that is, the measured bonding strength τ =3.33MPa, was observed after the steel bars were pulled out and the cracks at the junction with the concrete were found to have denser oblique cracks. The force F =75.33kN measured under vibration conditions to pull out the steel bars, that is, the measured bonding strength τ =2.96MPa, is reduced by 11.1% compared with the bonding strength under non-vibration conditions. After the steel bars were pulled out, core samples were drilled at the location of the original steel bars in the post-casting section, and the traces of steel bar pulling out were observed. It was found that the oblique cracks were denser at the position close to the second first-casting area, while the oblique cracks were not obvious at the position close to the first first-casting area, and were relatively smooth. This indicates that due to the relative displacement between the steel bars and the concrete during the vibration process, voids may be generated near the first pre-cast area, and the vibration has different effects on the bond strength between the steel bars and the concrete at different positions in the post-cast section. Comparative Example 1 cannot simulate the effect of the relative displacement between the steel bars and the concrete in the actual bridge widening project, and cannot simulate the effect of vibration on the bond strength between the steel bars and the concrete at different positions in the post-cast section, which leads to a larger bond strength in the test results of Comparative Example 1 than in Example 2.

[0083] like Figure 5 The graph shows the reinforcement stirring action curve along the length of the reinforcement;

[0084] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0085] The above is only a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein through the above teachings or the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A plate pull-out test device, characterized in that: The invention comprises a prefabricated test beam plate and a group of vibration tables arranged below the prefabricated test beam plate; the prefabricated test beam plate is nested in a beam plate mold (6); the beam plate mold (6) is a rectangular shell; the prefabricated test beam plate is divided into a first precast section (1), a postcast section (2) and a second precast section (3) in sequence along its width direction; the vibration table comprises a first vibration table (4) and a second vibration table (5); the first vibration table (4) is arranged below the first precast section (1); the second vibration table (5) is arranged above the second precast section (3); ) below; in the prefabricated test beam and slab, a plurality of drawn steel bars (8) are arranged in parallel perpendicular to the length direction of the post-cast section (2), and both ends of each drawn steel bar (8) respectively penetrate into the interior of the pre-cast section on both sides of the beam and slab; protective sleeves (9) are respectively sleeved on the drawn steel bars (8) located inside the pre-cast section, and an isolation layer (10) is provided inside the protective sleeves; the isolation layer (10) is formed by condensing a low-melting point slurry, and the composition of the low-melting point slurry includes epoxy resin; the melting point range of the low-melting point slurry is 58°C-80°C.

2. The plate pull-out test device according to claim 1, characterized in that: The beam-slab mould (6) is respectively formed by splicing a bottom plate, a first side plate (62) and a second side plate (63), wherein the first side plates (62) are arranged oppositely at two ends of the test beam-slab; the second side plates (63) are arranged respectively along the length direction of the first-casting section; the first side plate (62) on each side further comprises three independently arranged plates, and the three independently arranged plates respectively correspond to two first-casting sections and one post-casting section (2); the bottom plate also comprises three independently arranged plates, and the three independently arranged plates respectively correspond to the first-casting sections and the post-casting sections (2); the second side plates (63) arranged oppositely correspond to the side surfaces of the first-casting sections; and a partition plate for dividing the post-casting sections (2) is also arranged in the rectangular shell.

3. The plate pull-out test device according to claim 2, characterized in that: It also includes a profile reinforcement strip, wherein the profile reinforcement strip is arranged on the beam and slab mold (6) located at the position of the post-casting section (2); The contour reinforcement strip comprises a first reinforcement strip (15) and a second reinforcement strip (16), the first reinforcement strip (15) and the second reinforcement strip (16) being laid vertically and horizontally on the bottom plate, the first reinforcement strip (15) being a long side strip, the second reinforcement strip (16) being a short side strip, and the second reinforcement strip (16) being detachably connected to the first reinforcement strip (15); It also includes a third reinforcement strip (13), the third reinforcement strip (13) being arranged on the first side plate (62), the third reinforcement strip (13) being arranged at intervals along the width direction of the first side plate (62), and the third reinforcement strip (13) being detachably connected to the first reinforcement strip (15).

4. The plate pull-out test device according to claim 2, characterized in that: One end of the drawn steel bar (8) is flush with the side wall of the first precast section (1), and the other end of the drawn steel bar (8) protrudes 40-60 cm from the side wall of the second precast section (3).

5. The plate pull-out test device according to claim 2, characterized in that: A plurality of screw rods are passed through the first precast section (1) and the second precast section (3) in the vertical direction, one end of the screw rod is fixed to the top surface of the vibration table, and the other end of the screw rod is fixed by a limit bolt.

6. The plate pull-out test device according to claim 1, characterized in that: The protective sleeve (9) is made of PVC; the diameter of the protective sleeve (9) is 3-6 mm larger than the drawn steel bar (8).

7. A vehicle-induced vibration simulation test method of a plate-type pull-out test device according to any one of claims 1 to 6, characterized in that: The steps include: Step 1: Collect data by installing several vibration pickups under the target bridge to collect bridge vibration curves under different vehicle conditions; then establish a finite element model of the old bridge; Step 2, adjusting the simulation test device; the first pre-cast section (1) is used to simulate the old bridge side, and the second pre-cast section (3) is used to simulate the new bridge side; the post-cast section (2) is used to simulate the wet joint; concrete is poured into the post-cast section (2), and after the concrete pouring is completed, the first vibration table (4) is immediately turned on; Step 3: When the concrete in the post-cast section (2) reaches final setting, all first vibration tables (4) are closed; the test beam and slab are separated from the vibration table, and the formwork on the test beam and slab is demoulded, and then the bonding strength between the steel bars and the concrete in the post-cast section (2) is tested on the test beam and slab.

8. The vehicle-induced vibration simulation test method according to claim 7, characterized in that: In step 3, the bonding strength test is performed according to the following steps: The disassembled test beam and slab are heated to melt the slurry poured into the protective sleeve (9) and flow out, and a test device is installed on the drawn steel bar (8) on one side of the test beam and slab for testing.

9. The vehicle-induced vibration simulation test method according to claim 8, characterized in that: The test device comprises a pair of jacks (11), a sensor (12) and a fixing device; the fixing device comprises a steel beam plate (17) and a positioning anchor (14); a through hole is provided on the steel beam plate (17); the jacks are respectively placed on both sides of the drawn steel bar (8) to be tested, and a sensor (12) is installed at the end of each jack (11); the steel beam plate (17) is sleeved on the drawn steel bar (8), and the steel beam plate (17) is fixed at a specific position by the positioning anchor (14); and the jacks (11) can be opened for testing.

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