Concrete experiment beam capable of monitoring full-length strain of reinforcing steel bar

Abstract

The utility model discloses a concrete experiment beam capable of monitoring the full-length strain of a reinforcing steel bar, which internally comprises a plurality of layers of longitudinal bars with measurable full-length strain and a plurality of columns of stirrups with measurable full-length strain, and each stirrup consists of two hooked reinforcing steel bars with consistent structures and two sections of stirrup limbs, a steel sleeve is welded to the free end of each hook steel bar, the sleeves at the ends of the hook steel bars are connected through stirrup limbs to form a closed annular stirrup structure, long and straight grooves extending longitudinally are formed in the two sections of stirrup limbs, optical fibers are attached to the inner walls of the long and straight grooves, and the long and straight grooves are connected with the optical fibers. And the optical fiber extends out of the concrete beam and is connected to an optical fiber demodulator to read data. The surface non-transverse rib area of the longitudinal rib is provided with a small-size groove penetrating in the axial direction of the longitudinal rib, and an optical fiber sensor is attached to the small-size groove and also extends out of the concrete beam. The device can effectively improve the adverse factors which cannot be monitored by the traditional testing technology, and is convenient to evaluate and ensure the safety of the concrete structure.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of reinforced concrete performance test, specifically relates to a concrete experimental beam that can realize the strain monitoring of the whole length of steel bar. BACKGROUND

[0002] Steel bar strain measurement plays a crucial role in civil engineering, it is essential for evaluating and ensuring the safety, durability and functionality of concrete structures, it is directly related to the structural safety, performance evaluation and life prediction of buildings and infrastructure. Through accurate measurement of steel bar strain, engineers can verify and optimize structural design, ensure the reliability and stability of the structure under various load conditions. This measurement capability enables engineers to monitor the response of the structure in real time, so as to discover and repair potential structural damage in time, avoid catastrophic accidents. Steel bar strain measurement is also crucial for construction quality control, it can ensure the accurate placement of steel bars and the correct pouring of concrete during construction, so as to guarantee the overall performance of the structure. In addition, this measurement technology is also very useful in structural reinforcement and reconstruction engineering, which can help to evaluate the effectiveness of reinforcement measures, and provide data support for future maintenance and repair.

[0003] One of the commonly used steel bar strain measurement methods is to use strain gauges, which measure the strain of concrete by sticking or embedding strain gauges inside the concrete structure. Strain gauges can sense the tiny deformation of concrete and convert it into electrical signal output. These electrical signals can be used to calculate the strain of concrete after amplification and processing. However, this type of steel bar strain measurement technology has the following limitations and deficiencies:

[0004] 1, it destroys the bond between steel bar and concrete, changes the stress performance of reinforced concrete member, and cannot obtain the stress of steel bar under real stress conditions.

[0005] 2, there is locality, lack of data continuity, existing technology can usually only provide strain information in local area, cannot provide continuous strain distribution data along the whole length of steel bar, which limits the comprehensive understanding of the overall behavior of the structure.

[0006] 3, increase the complexity of construction, traditional strain gauges need to be pasted or fixed on steel bars during construction, and welding and other operations during construction will inevitably cause damage to strain gauges, increasing the complexity and cost of construction.

[0007] 4, durability problem, strain gauges pasted on the surface of steel bars may be damaged due to environmental factors (such as humidity, temperature change, chemical corrosion), affecting their long-term durability and reliability.

[0008] 5, existing technology may not be able to realize real-time data transmission or need complex data acquisition system, affecting the safety and reliability of the design.

[0009] The above-mentioned defects result in that real and accurate concrete steel bar strain data cannot be obtained quickly and conveniently for a long time, and thus the accuracy and safety of the reinforced concrete member design are adversely affected. Practical new type content

[0010] To solve the above-mentioned problems, the utility model discloses a concrete experimental beam capable of realizing steel bar full-length strain monitoring, which effectively improves the adverse factors of the traditional testing technology and facilitates the evaluation and safety assurance of the concrete structure.

[0011] To achieve the above-mentioned purpose, the technical scheme of the utility model is as follows:

[0012] A concrete experimental beam capable of realizing steel bar full-length strain monitoring, which comprises multiple layers of full-length strain measurable longitudinal bars and multiple columns of full-length strain measurable stirrups, wherein the full-length strain measurable stirrups comprise two U-shaped hook-shaped steel bars with the same structure, the two hook-shaped steel bars are oppositely arranged and enclose the full-length strain measurable longitudinal bars, a sleeve is welded to the free end of each hook-shaped steel bar, the sleeves at the two ends of the two hook-shaped steel bars are connected by a stirrup limb to form a whole, two anchor end plates are arranged at the top and bottom of the beam of the full-length strain measurable longitudinal bars, and each anchor end plate is arranged at the longitudinal bar end portion of the top and bottom of the beam; a long straight groove penetrating along the axial direction of each full-length strain measurable stirrup limb is arranged in the stirrup limb, an optical fiber is attached to the inner wall of the long straight groove, the optical fiber extends out of the stirrup limb and is connected to a demodulation device, and a small-size groove penetrating along the axial direction of each full-length strain measurable longitudinal bar is arranged in the surface of the longitudinal bar without a horizontal rib area, an optical fiber is continuously attached to the inner wall of the small-size groove, and the optical fiber extends out of the longitudinal bar and is connected to the demodulation device.

[0013] As a supplement of the utility model, each full-length strain measurable stirrup limb has an external thread segment at the two ends, the two ends of the stirrup limb pass through the sleeve, and are fixed by a nut assembled on the stirrup limb.

[0014] As a supplement of the utility model, each full-length strain measurable longitudinal bar has an external thread segment at the two ends, the longitudinal bar passes through the bar hole of the anchor end plate, and is fixed by a nut assembled on the longitudinal bar at the two sides of the anchor end plate.

[0015] As a supplement of the utility model, the length of the external thread segment at the two ends of the steel bar is 5mm-20mm.

[0016] As a supplement of the utility model, the nut on the stirrup limb or the nut on the longitudinal bar is a hexagonal nut or a threaded steel sleeve, and the diameter of the hexagonal nut is the same as the diameter of the steel bar.

[0017] As a supplement of the utility model, the optical fiber adopts nylon coating cable, and the optical fiber is bonded by cyanoacrylate adhesive, and the optical fiber surface is coated with an epoxy resin protective layer.

[0018] As a supplement of the utility model, the length of the optical fiber is 400mm-2400mm.

[0019] As a supplement of the utility model, the full-length strain measurable stirrup limb adopts ribbed steel bar or plain round steel bar, and the diameter is 8mm-20mm.

[0020] As a supplement of the utility model, the depth of the long straight groove of the full-length strain measurable stirrup is 3mm-5mm, and the width is 3mm-5mm.

[0021] As a supplement of the utility model, the small-size groove width of the full-length strain measurable longitudinal reinforcement is 3mm-5mm, and the depth is 3mm-5mm.

[0022] As a supplement of the utility model, the full-length strain measurable longitudinal reinforcement is provided with an anchoring end plate at both ends, and the thickness is 10mm-20mm.

[0023] As a supplement of the utility model, the optical fiber lead wire of the full-length strain measurable longitudinal reinforcement is sleeved with a polyvinyl chloride (PVC) pipe, steel wire binding is used for fixing the connection of the PVC pipe and the longitudinal reinforcement, and the diameter of the PVC pipe is 2-3mm.

[0024] The concrete experimental beam capable of realizing full-length strain monitoring of steel bars, adopts a four-point bending loading scheme, and only the left half-span beam section adopts a full-length strain testing scheme of steel bars, the right half-span beam section is not grooved, and dense stirrups are arranged.

[0025] The utility model has the advantages that:

[0026] Under the premise of not damaging the bonding performance of the steel bars and the concrete, the full-length strain of the steel bars can be measured, the closed connection mode can effectively guarantee the constraint performance of the stirrups on the concrete, the stirrups are all made by adopting the welding-free mechanical connection, the damage of the optical fiber sensor caused by welding high temperature can be effectively avoided, the grooved and pasted optical fiber sensor greatly guarantees long-term durability, the full-length strain measurement can obtain the data of each part in real time, guarantee the safety and rationality of the design, and potential structure problems of the existing structure can be found in time.

[0027] 1. The utility model discloses a groove and continuously pastes optical fiber sensor, effectively eliminates the influence of the traditional measurement mode on the bonding performance of the steel bars and the concrete.

[0028] 2. The length direction continuous optical fiber sensor pasted on the inside of the stirrup limb can obtain continuous strain along the full length of the stirrup limb, so that the actual stress condition of the steel bar can be accurately obtained, the error of the traditional measurement mode is greatly reduced, and the overall understanding of the structure overall behavior is ensured.

[0029] 3. The stirrup limb and the hooked steel bar are combined into a stirrup in a mechanical connection mode, damage of the optical fiber sensor caused by high temperature welding is effectively avoided, so that the readability of the measurement data is ensured, and the complexity and cost of construction are reduced.

[0030] 4. The utility model discloses a certain degree of physical protection is provided for the optical fiber sensor through the slot in the stirrup and the groove on the surface of the longitudinal reinforcement, so that it is not easy to be damaged or eroded by the environment, and the long-term durability is greatly ensured.

[0031] 5. The full length strain measurement can help to verify and calibrate the structure design theory, ensure the safety and rationality of the design, for the existing structure, the full length strain measurement of the steel bar can monitor the use state and health condition of the structure, and potential structure problems can be found in time. BRIEF DESCRIPTION OF DRAWINGS

[0032] Figure 1 It is the utility model experimental beam perspective drawing.

[0033] Figure 2 It is the utility model loading schematic view.

[0034] Figure 3 It is the internal perspective view of the concrete experimental beam of the utility model.

[0035] Figure 4 It is the stirrup assembly perspective view of the utility model.

[0036] Figure 5 It is the stirrup assembly section view of the utility model.

[0037] LIST OF FIGURES:

[0038] 1, longitudinal reinforcement, 2, stirrup, 3, hooked steel bar, 4, sleeve, 5, stirrup limb, 6, beam top anchoring end plate, 7, beam bottom anchoring end plate, 8, optical fiber, 9, nut on the stirrup limb, 10, anchoring end plate, 11, nut on the longitudinal reinforcement. DETAILED DESCRIPTION

[0039] The utility model will be further illustrated in combination with the drawings and specific embodiments, and it should be understood that the following specific embodiments are only used to illustrate the utility model and are not used to limit the scope of the utility model.

[0040] As shown in the figure, the concrete experimental beam capable of realizing full-length strain monitoring of steel bars, the utility model discloses a full-length strain measurable longitudinal reinforcement 1 and full-length strain measurable stirrup 2, longitudinal reinforcement 1 is divided into upper and lower two layers, a plurality of stirrups 2 are spaced and enclose longitudinal reinforcement 1, and longitudinal reinforcement 1 and stirrup 2 are provided with grooves inside and are arranged with optical fiber 8, the longitudinal reinforcement 1 and the stirrup 2 are all in the concrete experimental beam, and the optical fiber extends out of the concrete experimental beam and is connected with a demodulation device.

[0041] Its manufacturing process is as follows:

[0042] First, the stirrup limb 5 is made, and the specific process is as follows:

[0043] 1, first, the two ends of the steel bar are threaded, and the threaded section length is 5mm-20mm.

[0044] 2, then, along the axis of the steel bar length direction, the steel bar (cylindrical) is cut into two halves (half-cylindrical) by wire cutting.

[0045] 3, long straight grooves are respectively cut on the two sections along the steel bar axis direction by wire cutting or punch, and the depth is 3mm-5mm, the width is 3mm-5mm, and the length is the same as the steel bar length.

[0046] 4, on the inner wall of the groove, the optical fiber is attached along the steel bar axis direction, as shown in the figure, the optical fiber extends out of the steel bar and is connected with a demodulation device. Figure 3

[0047] 5, finally, the two cut steel bars (half-cylindrical) are re-bonded into the stirrup limb 5 (cylindrical) by high-strength epoxy glue, and the optical fiber is drawn out from one end of the steel bar or from both ends.

[0048] The second step, the manufacturing method of the hook steel bar 3 with sleeve 4 at both ends is as follows:

[0049] 1, first, the steel bar is bent into a hook steel bar 3 (U-shaped) with hooks at both ends by a steel bar bending machine or manually bending the hook, the hook section and the straight section are at 90 degrees, and the hook section length is 50mm-100mm.

[0050] 2, second, the sleeve 4 is connected with the hook section of the hook steel bar 3 to form a whole by welding.

[0051] The third step, the assembly method of the full-length strain measurable stirrup is as follows:

[0052] 1, the two ends of the stirrup limb 5 are respectively connected with the matching nut, and are screwed to the root of the threaded section.

[0053] 2, then, the two ends of the stirrup limb 5 are respectively inserted through the sleeves at the ends of the two hook steel bars, and the sleeve one end is close to the nut at the root of the threaded section. ​

[0054] 3. Finally, the threaded segment of the stirrup limb is connected to another matching nut, and is screwed to tightly adhere to the other end surface of the sleeve, finally forming a closed stirrup 2.

[0055] Fourthly, the method for manufacturing the longitudinal reinforcement 1 is as follows:

[0056] (1) A threaded lathe is used to make threads on both ends of the steel bar. The threaded segment cooperates with the steel bar threaded sleeve, which can provide effective end anchoring during the later assembly of the steel bar framework.

[0057] (2) A groove with a width of 3 mm and a depth of 5 mm is punched and milled on the surface of the steel bar. Since only the steel bars in the half-span beam segment use a continuous strain measurement system (the other half-span is the stirrup densification area) in the later test, the longitudinal reinforcement does not need to be slotted throughout the length, but only needs to be slotted half the length and two optical fibers are attached to the inner wall of the long straight groove, which extend outside the stirrup limb and are connected to the demodulation equipment.

[0058] (3) In the steel bar groove, the optical fiber uses a nylon-coated cable, and the optical fiber is bonded with cyanoacrylate adhesive, and an epoxy resin protective layer is applied to the surface of the optical fiber. Then the groove is fully coated with silicone.

[0059] To reduce the test cost, for the four-point bending test beam, only the left half-span beam segment uses the full-length steel bar strain test scheme, the right half-span beam segment steel bar is not slotted, and dense stirrups are configured to prevent shear failure, as shown in FIG. 1. Regarding the anchoring of the longitudinal reinforcement, the processing method of the conventional end hook will cause difficulty in leading the optical fiber lead, and the lead cannot be smoothly led out of the beam end. Therefore, anchor end plates are provided at both ends of the longitudinal reinforcement in this test, which facilitates accurate positioning of the longitudinal reinforcement and provides effective anchoring for the longitudinal reinforcement. The specific scheme is as follows:

[0060] (4) Use 10 mm thick steel plates to make beam top longitudinal reinforcement anchor end plate 6 and beam bottom longitudinal reinforcement anchor end plate 7, respectively. The anchor end plate is provided with a reinforcing bar hole, and the upper and lower end plates are positioned and connected as a whole by welding short steel bars to provide support for the longitudinal reinforcement framework.

[0061] (5) The longitudinal reinforcement 1 is inserted through the reinforcing bar hole of the end plate, and is embedded with a hexagonal nut or a threaded steel sleeve. During installation, the slotted side of the longitudinal reinforcement is directed towards the side of the beam.

[0062] (6) The lead wire extending from the end of the longitudinal reinforcement is protected by a plastic corrugated pipe. Steel wire is used to bind and fix the connection between the corrugated pipe and the steel bar. In the beam end support range, the stirrup densification measure is used to further enhance the anchoring and prevent local concrete damage.

[0063] (7) To achieve accurate positioning of the longitudinal reinforcement framework, the beam span end with stirrup densification is also anchored using a perforated steel plate.

[0064] The utility model adopts a stirrup distributed strain test scheme, is more close to the real stress condition of traditional closed stirrup, can form effective anchoring and restraint, and can protect internal optical fiber.

[0065] (1) make the hook steel bar 3 as the closed stirrup bottom component, and weld the connecting ring (sleeve 4) at both ends of the hook steel bar. In order to prevent the out-of-plane bending moment of the stirrup limb when being pulled, the sleeve 4 needs to be symmetrically welded at the opposite end of the hook steel bar with the axis of the hook steel bar as the center.

[0066] (2) the stirrup limb 5 with the distributed optical fiber sensor pasted inside is passed through the sleeve 4, and is fixed by the hexagonal nut anchoring.

[0067] (3) the hook steel bar section needs to be additionally made as the stirrup top component, and is bound with the stirrup limb as a whole, and can effectively restrain the lateral buckling of the compression longitudinal reinforcement.

[0068] (4) after the concrete pouring demoulding, the opening steel plate is installed at the beam top, and is connected as a whole with the stirrup limb through the nut.

[0069] Working process:

[0070] When measuring the strain of the experimental beam in the stress deformation process, the optical fiber led out from the stirrup limb and longitudinal reinforcement end is connected with the strain demodulator, and the full-length continuous strain distribution of the internal steel bar of the experimental beam can be measured in real time.

[0071] It should be noted that the above content only illustrates the technical idea of the utility model, and cannot limit the protection scope of the utility model, and for ordinary skilled persons in the technical field, a plurality of improvements and refinements can be made without departing from the principle of the utility model, and the improvements and refinements all fall within the protection scope of the utility model claim.

Claims

1. A concrete test beam capable of implementing full-length strain monitoring of steel reinforcement, characterized in that: Its inside includes multilayer full length strain measurable longitudinal reinforcement (1) and multilayer full length strain measurable stirrup (2), the full length strain measurable stirrup (2) includes two identical U-shaped hook reinforcement (3), two hook reinforcement (3) are oppositely arranged and enclose full length strain measurable longitudinal reinforcement (1), the free end of each hook reinforcement (3) is welded with a sleeve (4) respectively, two hook reinforcement ends of the sleeve are connected to form a whole through a stirrup limb (5) respectively, the beam top and beam bottom of the full length strain measurable longitudinal reinforcement (1) are provided with two anchor end plates (6), (7), each anchor end plate is positioned at the longitudinal reinforcement end of the beam top and beam bottom respectively, each full length strain measurable stirrup limb (5) is provided with a long straight groove through its axial direction, the inner wall of the long straight groove is pasted with optical fiber (8), the optical fiber is stretched out of the stirrup limb (5) and connected with demodulation equipment, the surface of each full length strain measurable longitudinal reinforcement (1) is provided with a small size groove through its axial direction in the non-rib area, the inner wall of the small size groove is continuously pasted with optical fiber (8), and the optical fiber is stretched out of the longitudinal reinforcement (1) and connected with demodulation equipment. 2.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: Each full length strain measurable stirrup limb (5) has an external thread segment at both ends, the length of the external thread segment is 5mm-20mm, the two ends of the stirrup limb (5) pass through the sleeve (4) and are fixed by the nut (9) assembled on the stirrup limb. 3.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: Each full length strain measurable longitudinal reinforcement (1) has an external thread segment at both ends, the length of the external thread segment is 5mm-20mm, the longitudinal reinforcement passes through the hole of the anchor end plate and is fixed by the nut (11) assembled on the longitudinal reinforcement on both sides of the anchor end plate.

4. The concrete test beam capable of monitoring the strain of the steel bar according to claim 1, characterized in that: The length of the optical fiber (8) is 400mm-2400mm.

5. The concrete test beam capable of monitoring the strain of the steel bar along the whole length according to claim 2 or 3, characterized in that: The nut (9) on the stirrup limb or the nut (11) on the longitudinal reinforcement is a hexagonal nut or a threaded steel sleeve. 6.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: The optical fiber (8) adopts nylon coating cable, and the optical fiber is bonded with cyanoacrylate adhesive, and an epoxy resin protective layer is applied on the surface of the optical fiber. 7.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: The full length strain measurable stirrup limb (5) adopts ribbed steel bar or bright round steel bar, and the diameter is 8mm-20mm. 8.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: The depth of the long straight groove of the full length strain measurable stirrup (2) and the small size groove of the full length strain measurable longitudinal reinforcement (1) is 3mm-5mm, and the width is 3mm-5mm. 9.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: The anchor end plate is arranged at both ends of the full length strain measurable longitudinal reinforcement (1), and the thickness is 10mm-20mm. 10.The concrete experimental beam capable of monitoring the full-length strain of steel bars according to claim 1, characterized in that: The optical fiber lead wire protruding from the longitudinal reinforcement end of the full length strain measurable longitudinal reinforcement (1) is sleeved with a PVC pipe, the PVC pipe is fixed by steel wire binding at the connection with the longitudinal reinforcement, and the diameter of the PVC pipe is 2-3mm.

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