Loading device for single-sided freeze thawing-bending coupling durability test

Abstract

The invention relates to the technical field of civil engineering, in particular to a single-side freeze-thaw-flexural coupling durability test load holding device which comprises a test piece loading and load measuring mechanism and a load holding mechanism. The loading mechanism is composed of two high-strength steel plates, four loading screws, a hydraulic cylinder and a pressure sensor, and the stability and accuracy of load application are ensured. The load holding mechanism adopts a tripod structure, so that the overall height is reduced, the space of the freeze-thaw test box is saved, the dead weight of the device is reduced, and the test piece is convenient to carry. In addition, a resistance strain gauge arranged on the device can monitor the loading state in real time, supplementary loading is carried out according to strain data, and the loading effect is ensured. The design breaks through the limitation of a traditional test device, the accuracy and reliability of the concrete durability test are improved, and more effective experiment conditions are provided for related research.

Description

Technical Field

[0001] The invention relates to the technical field of civil engineering, and in particular to a single-sided freeze-thaw-bending coupled durability test holding device. Background Art

[0002] Durability is the most important indicator of high-performance concrete. There are a lot of research reports on concrete durability at home and abroad, and new results and new experiences are constantly being achieved. In 2006, Mu Ru of Southeast University proposed in his paper "Durability and Life Prediction of Concrete under the Combined Action of Freeze-Thaw Cycles, External Bending Stress and Salt Solution" that laboratories often conduct independent research on various durability factors of concrete and extract the damage laws of various durability factors on concrete. In fact, the durability damage of concrete occurs under the condition of continuous load. The freeze-thaw test based on the damage of a single factor is used to analyze the durability of concrete under the coupling of continuous load and freeze-thaw environment in actual engineering. The conclusions obtained are often not objective and difficult to accurately reflect the actual engineering. Du Peng of China Building Materials Science Research Institute also mentioned in his 2014 paper "Freeze-thaw Damage Model and Life Prediction of Concrete under Multi-factor Coupling" that actual service concrete structures are usually under the action of complex environmental factors, and the concrete damage caused by the coupling of different factors is far greater than the superposition of the individual effects of each factor.

[0003] Reinforced concrete flexural members are an important part of the concrete structure system. In order to study the durability of actual service concrete flexural members under the action of freeze-thaw environmental factors, the experimental study of the coupling effect of freeze-thaw cycles and bending stress is gradually becoming a hot topic. In this experiment, the loading and holding device of concrete flexural members is an important guarantee for achieving the research goal. At present, the research and development of this device in China is still in its infancy. The way to apply bending stress in the experimental device is mainly to clamp with steel tie rods, and to generate pre-stress by bolt tightening to make the beam bend and deform. For example, 1) The Chinese patent "CN201681017U" published on December 22, 2010, "A kind of reinforced concrete beam freeze-thaw load coupling durability test holding device", uses four steel tie rods and loading plates to bend and hold two concrete beams. For example, 2) The paper "Study on the bending performance of PP-ECC beams under freeze-thaw-bending load coupling" in the Journal of Southwest Jiaotong University in April 2024 uses two tie rods and a base to apply loads to the two beams through a jack. Both of the above methods apply bending loads to two beams at the same time by tensioning the steel rods. During the load holding process, the two beams cannot be tested separately and cannot meet the requirements of the single-sided freeze-thaw test. In the above method 1), the load is applied by manually tightening the bolts, the load level is low, and effective bending deformation cannot be achieved. In addition, due to the lack of a load measuring device, the tension generated by each lever is difficult to maintain, and the error in applying the load is large. In method 2), the jack for applying the load and the sensor for measuring the load occupy space, resulting in the height of the loaded specimen being too large to be placed in a conventional freeze-thaw test chamber, which increases the difficulty of the freeze-thaw test. Summary of the invention

[0004] Based on the above purpose, the present invention provides a single-sided freeze-thaw-bending coupled durability test holding device.

[0005] There are three aspects of technical problems to be solved by the invention: 1) To achieve the application of bending load to a single reinforced concrete beam and to hold the load, so as to meet the requirements of the single-sided freeze-thaw test for the specimen. 2) To control the loading level of the load and achieve precise loading. 3) To reduce the overall height of the load-holding specimen, reduce the space volume occupied by the load-holding specimen in the freeze-thaw test chamber, and reduce the difficulty of the single-sided freeze-thaw test.

[0006] The technical solution adopted to solve this technical problem: A single-sided freeze-thaw-bending coupled durability test holding device includes a specimen loading and load measuring mechanism and a load holding mechanism. The specimen loading and load measuring mechanism applies bending load to the reinforced concrete beam specimen, and the mechanism includes a high-strength steel plate, a holding screw, a high-strength nut, a loading steel rod, a hydraulic cylinder, and a pressure sensor; the high-strength steel plates are horizontally arranged relative to each other, and there are screw holes on both sides of the steel plates; the holding screw passes vertically and parallelly through the screw holes of the high-strength steel plates; the nuts are used to fix the holding screw and the high-strength steel plate; the loading steel rod is tightly arranged between the high-strength steel plate and the upper side of the reinforced concrete specimen; the hydraulic cylinder is placed between the high-strength steel plates, and the pressure sensor is placed between the top of the hydraulic cylinder and the high-strength steel plate. The load-holding mechanism includes 1 steel tie rod, 2 steel compression rods, 4 top angle pin steel bars, 4 bottom angle pin steel bars, 1 loading steel plate, 1 support steel bar, and 1 resistance strain gauge; the 1 steel tie rod and the 1 steel compression rod form two tripods, each tripod is composed of 1 steel tie rod and 1 steel compression rod; the 1 top angle pin steel bars are respectively connected to 1 steel tie rod; the 1 bottom angle pin steel bars are respectively connected to 1 steel tie rod and 1 steel compression rod; the two ends of the loading steel plate each have a circular hole, and one end of the loading steel plate is respectively connected to the 1 bottom angle pin steel bar; the 1 support steel bar is placed tightly against the lower side of the reinforced concrete specimen, and the two ends of each support steel bar are respectively connected to the other end of the loading steel plate; the 1 resistance strain gauge is attached to the 1 tie rod.

[0007] Beneficial effects of the present invention: The present invention proposes for the first time a loading and holding device for a bending member in a single-sided salt freezing test. The loading mechanism of the device is small and space-saving, and the holding mechanism adopts a tripod structure to reduce the weight of the device. The space in the single-sided salt freezing test box is limited. The device is small in size, which is conducive to the conduct of the test. It has a low weight, which reduces the damage of the specimen to the test box and is convenient for the transportation of the specimen. The use of a resistance strain gauge to monitor the load reduces the occupation of the loading equipment and the measuring equipment by the holding device, and further reduces the weight of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0008] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings in the following description are only for the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0009] Figure 1 It is a schematic diagram of the overall structure of an embodiment of the present invention; Figure 2 It is a schematic diagram of the front structure of an embodiment of the present invention.

[0010] The markings in the figure are: 1. Upper high-strength steel plate; 2. Lower high-strength steel plate; 3. Loading screw; 4. High-strength nut; 5. Loading steel rod; 6. Hydraulic cylinder; 7. Pressure sensor; 8. Steel pull rod; 9. Steel pressure rod; 10. Top angle pin steel rod; 11. Bottom angle pin steel rod; 12. Loading steel plate; 13. Support steel rod; 14. Reinforced concrete beam specimen; 15. Resistance strain gauge. DETAILED DESCRIPTION

[0011] The present invention is described in detail below in conjunction with the accompanying drawings and specific embodiments. At the same time, it is explained here that in order to make the embodiments more detailed, the following embodiments are the best and preferred embodiments, and those skilled in the art may also adopt other alternatives to implement some known technologies; and the accompanying drawings are only for more specific description of the embodiments, and are not intended to specifically limit the present invention.

[0012] It should be noted that the references to "one embodiment", "embodiment", "exemplary embodiments", "some embodiments" and the like in the specification indicate that the embodiments described may include specific features, structures or characteristics, but not every embodiment may include the specific features, structures or characteristics. In addition, when a specific feature, structure or characteristic is described in conjunction with an embodiment, it should be within the knowledge of a person skilled in the art to implement such feature, structure or characteristic in conjunction with other embodiments (whether or not explicitly described).

[0013] In general, a term can be understood, at least in part, from its use in context. For example, depending, at least in part, on the context, the term "one or more" as used herein can be used to describe any feature, structure, or characteristic in the singular sense, or can be used to describe a combination of features, structures, or characteristics in the plural sense. Additionally, the term "based on" can be understood as not necessarily intended to convey an exclusive set of factors, but can instead, depending, at least in part, on the context, allow for the presence of other factors that are not necessarily explicitly described.

[0014] A single-sided freeze-thaw-bending coupled durability test loading device comprises a specimen loading and load measuring mechanism and a load holding mechanism.

[0015] The loading and load measuring mechanism includes: an upper high-strength steel plate 1, a lower high-strength steel plate 2, a holding screw 3, a high-strength nut 4, a loading steel rod 5, a hydraulic cylinder 6, and a pressure sensor 7. The load holding mechanism includes: a steel pull rod 8, a steel pressure rod 9, a top angle pin steel rod 10, a bottom angle pin steel rod 11, a loading steel plate 12, and a support steel rod 13.

[0016] The specific steps are as follows: Step 1: Place two support steel bars 13 at corresponding positions at the lower part of the reinforced concrete beam specimen 14; Step 2: Make the round holes at one end of the four loading steel plates 12 with round holes at both ends intersect with the support steel rod 13; Step 3: Insert the four bottom angle pin steel bars 11 and the other end circular holes of the four loading steel plates 12; Step 4: Insert the two ends of the two steel pressure rods 9 into the four bottom angle pin steel rods 11; Step 5: Insert one end of the four steel tie rods 8 into the four bottom angle pin steel bars 11; Step 6: Weld the two top angle pin steel bars 10 to the upper high-strength steel plate 1; the welding position is as follows: Figure 1 , Figure 2 As shown; Step 7: Insert the other ends of the four steel tie rods 8 into the two top angle pin steel bars 10; Step 8: Place two loading steel bars 5 at corresponding positions on the top surface of the reinforced concrete beam specimen 14; Step 9: Place the lower high-strength steel plate 2 on the two loading steel rods 5; Step 10: Insert the four holding screws 3 into the corresponding circular holes of the upper high-strength steel plate 1 and the lower high-strength steel plate 2, and temporarily fix them with high-strength nuts 4; Step 11: Place the hydraulic cylinder 6 on the lower high-strength steel plate 2; Step 12: Place the pressure sensor 7 on the hydraulic cylinder 6; Step 13: Paste the resistance strain gauge 15 on one of the steel rods 8; and connect the strain gauge to the strain acquisition device; Step 14: The oil pump supplies oil to the hydraulic cylinder 6 for loading, and the pressure sensor 7 records the load value; Step 15: When the load value recorded by the pressure sensor 7 reaches the test requirement, the strain value of the resistance strain gauge 15 is recorded, and the collection of strain data of the resistance strain gauge 15 is continued.

[0017] Step 16: Tighten the high-strength nut 4 to achieve load holding; Step 17: Hydraulic cylinder 6 returns oil to unload; Step 18: Remove the hydraulic cylinder 6 and the pressure sensor 7; Step 19: Place the loaded specimen into a freeze-thaw cycle chamber for a single-sided freeze-thaw test; during the test, continue to collect 15 strain data from the resistance strain gauge, monitor the strain value in real time, and perform additional loading according to the change in the strain value to ensure the loading effect.

[0018] The present invention covers any substitution, modification, equivalent method and scheme made on the essence and scope of the present invention. In order to make the public have a thorough understanding of the present invention, specific details are described in detail in the following preferred embodiments of the present invention, but those skilled in the art can fully understand the present invention without the description of these details. In addition, in order to avoid unnecessary confusion about the essence of the present invention, well-known methods, processes, procedures, components and circuits are not described in detail.

[0019] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A single-sided freeze-thaw-bending coupled durability test loading device, comprising a specimen loading and load measuring mechanism and a load holding mechanism, wherein the specimen loading and load measuring mechanism is composed of an upper high-strength steel plate (1), a lower high-strength steel plate (2), four loading screws (3), eight high-strength nuts (4), two loading steel rods (5), a hydraulic cylinder (6) and a pressure sensor (7), and is characterized in that: The load-holding mechanism is composed of four steel tension rods (8), two steel compression rods (9), a top angle pin steel rod (10), a bottom angle pin steel rod (11), four loading steel plates (12), two support steel rods (13) and a resistance strain gauge (15). The device can apply a bending load to a single reinforced concrete beam and hold the load, and has load measurement and control functions.

2. A single-sided freeze-thaw-bending coupled durability test holding device according to claim 1, characterized in that: The combined use of the hydraulic cylinder (6) and the pressure sensor (7) can monitor the load level in real time and ensure accurate load application in a single-sided freeze-thaw test.

3. A single-sided freeze-thaw-bending coupled durability test holding device according to claim 1, characterized in that: The load holding mechanism adopts a tripod structure, which reduces the overall height of the load holding specimen and effectively saves space in the freeze-thaw test chamber.

4. A single-sided freeze-thaw-bending coupled durability test holding device according to claim 1, characterized in that: The resistance strain gauge (15) can monitor the load holding state in real time, and perform supplementary loading according to the strain data of the test piece, thereby ensuring the load holding effect.

5. A single-sided freeze-thaw-bending coupled durability test holding device according to claim 1, characterized in that: The four load-bearing screw rods (3) are fixed to the high-strength steel plate via high-strength nuts (4), thereby ensuring the stability and accuracy of load application.

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