Concrete structure waterproof layer test system and test method

Abstract

The application provides a concrete structure waterproof layer test system and a test method, and the test system comprises a concrete beam, a waterproof layer, a support system, a sealing ring, a sealing steel plate, a load applying system and a water pressure applying system; the concrete beam is provided with a steel bar in the longitudinal direction close to the top surface, the support system is supported on the bottom surface of the concrete beam, and the waterproof layer covers the longitudinal middle position of the top surface of the concrete beam; the top surface of the waterproof layer is provided with the sealing ring; the top surface of the sealing ring is pressed with the sealing steel plate, the sealing steel plate is provided with a vertical water injection hole and a vertical exhaust hole; the load applying system is used for applying pressure to the concrete beam; and the water pressure applying system is used for testing the waterproof performance. The application provides the anti-cracking test system and the test method of the waterproof layer based on the action mechanism that the cracking of the concrete causes the cracking of the waterproof layer, which can facilitate the waterproof design, test and long-term performance maintenance of the bridge and various reinforced concrete structures, thereby significantly prolonging the service life.

Description

Technical Field

[0001] This invention is mainly applicable to the field of bridge structure durability, and also applicable to the design, construction, prefabricated construction and waterproofing technology of roads, tunnels, buildings, and hydraulic structures, especially relating to the test system and test method for waterproofing layers of concrete structures. Background Technology

[0002] Extending the lifespan of reinforced concrete structures and ensuring their long-term performance are current research hotspots and long-term strategic issues. Water is the most important factor affecting the durability of reinforced concrete structures, and reducing water erosion of reinforced concrete is of great significance for maintaining the long-term performance of various engineering structures. Taking bridge structures as an example, there were originally no clear regulations regarding the installation of waterproofing layers on bridge decks. However, through nearly 30 to 40 years of engineering experience, especially the experience of repairing and reinforcing a large number of old bridges in the last 10 to 20 years, it has been gradually recognized that the main causes of defects in concrete bridges are concrete carbonation, chloride ionization, alkali content, alkali-aggregate reaction caused by reactive aggregates, as well as frost heave damage and steel corrosion. These are all factors closely related to water. Therefore, the installation of waterproofing layers has become an important means to reduce defects in concrete bridges and extend their service life.

[0003] Even with waterproofing layers, and especially considering that bridge design typically requires waterproofing materials to have an elongation at break exceeding 800%, far exceeding the ultimate tensile strain of steel reinforcement (1%) and concrete (0.01%), the actual performance requirements are still insufficient. Figure 1 In reality, even with dense reinforcement, concrete structures are prone to water leakage at cracks after the concrete cracks, severely reducing the service life of the structure and requiring frequent maintenance. This is especially true for prefabricated concrete beam bridges with simply supported structures and continuous decks, where water damage at the deck continuity has become a common problem.

[0004] It is evident that existing waterproofing layers have failed to maintain their intended performance. The fundamental reason for this is that current technology has not addressed the microscopic nature of concrete cracking and its impact on the waterproofing layer through crack resistance testing. For example, the current national standard GB / T 16777-2008, "Test Methods for Waterproofing Coatings for Buildings," tests individual waterproofing layer specimens using uniaxial tensile and shear tests to measure tensile strength, shear strength, elongation at break, bond strength, low-temperature bending performance, and impermeability.

[0005] A few tests used a pre-set crack width and a "stripping method" to test the crack resistance of the waterproofing layer. This involved creating a crack between two concrete blocks (the crack must have a certain width, at least a few tenths of a millimeter or sub-millimeter), then applying a waterproofing layer to the top of the concrete blocks. After the waterproofing layer cured, thin iron strips were continuously inserted into the pre-set crack to widen the crack until visible cracks or holes appeared. At this point, the waterproofing layer was considered to have failed. However, this loading method was too slow and differed from the actual situation where reinforced concrete structures (especially bridge structures) were subjected to vehicle loads and cracked in a very short time. Furthermore, no water or water pressure was applied during or after the test, so the seepage prevention performance of the waterproofing layer under high water pressure after the concrete cracked could not be measured.

[0006] Obviously, the above-mentioned test methods differ significantly from the actual cracking process of reinforced concrete structures, leading to discrepancies in the test results. Furthermore, none of the above-mentioned test methods consider the microscopic interaction mechanism between the concrete and the waterproof layer during cracking, especially the impact of the sudden release of strain energy on the stress of the waterproof layer during the transient process of concrete cracking. This is the fundamental reason why existing waterproofing technologies have failed to maintain good performance as designed. Summary of the Invention

[0007] To address the aforementioned issues, this invention provides a testing system and method for waterproofing layers in concrete structures. Based on the mechanism by which cracking in concrete leads to cracking in the waterproofing layer, it presents a crack resistance testing system and method for the waterproofing layer. This facilitates the waterproofing design and testing of bridges and various reinforced concrete structures, enabling them to maintain their long-term performance and significantly extend their service life.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] A concrete structure waterproofing layer test system, characterized in that it includes a concrete beam, a waterproofing layer, a support system, a sealing ring, a sealing steel plate, a load application system, and a water pressure application system; the longitudinal direction is defined along the length of the concrete beam, the gravity direction is defined as the vertical direction, and the direction orthogonal to both the longitudinal and vertical directions is defined as the transverse direction;

[0010] The concrete beam is reinforced with steel bars along the longitudinal direction near the top surface. The support system is supported on the bottom surface of the concrete beam. The waterproof layer covers the longitudinal middle position of the top surface of the concrete beam, and an interface is formed between the waterproof layer and the concrete beam.

[0011] The top surface of the waterproof layer is provided with the sealing ring; the top surface of the sealing ring is pressed with the sealing steel plate, and the sealing steel plate is provided with vertically penetrating water injection holes and air vents within the vertical projection range of the sealing ring;

[0012] The load application system is installed on the concrete beam and is capable of applying pressure to the concrete beam to cause cracks to appear on the top surface of the concrete beam;

[0013] The water pressure application system includes a water injection pipe, a pressure testing instrument, and a sealing valve. The water injection pipe is connected to the water injection hole of the sealing steel plate. The pressure testing instrument is installed on the water injection pipe for testing water pressure. The sealing valve is installed on the vent hole of the sealing steel plate for sealing the vent hole.

[0014] The technical principles and effects of the above invention are as follows: (1) The present invention has found that the essence of concrete cracking is that the distance between the concrete material molecules on both sides of the crack changes abruptly from the nanometer level to the millimeter level visible to the naked eye. The interface between the concrete and the waterproof layer is uneven on a microscopic scale. The longitudinal interaction between the concrete and the waterproof layer includes the chemical adsorption force between the molecules of the two, the static friction resistance and the mutual squeezing and biting force. Therefore, the amount of interface slip between the concrete surface and the waterproof layer when the concrete cracks can be basically ignored. Therefore, when the concrete cracks open to both sides, it will also drive the waterproof layer to open to both sides of the crack. That is, the instant the concrete cracks, there will be a tearing effect on the waterproof layer, thereby making the distance between the material molecules on the bottom surface of the waterproof layer also... The abrupt change from the nanometer level to the millimeter level represents a nearly 100,000-fold increase in distance, manifesting as a crack visible to the naked eye. While this increase in longitudinal distance decreases rapidly as the vertical distance between the waterproofing layer molecules and the concrete surface increases, the 800% elongation at break of the waterproofing layer material near the concrete surface is insufficient to withstand such a significant increase in longitudinal distance. Therefore, when the concrete cracks, the waterproofing layer material near its surface will inevitably crack as well, stopping after reaching a certain vertical height. The key issue is whether the remaining uncracked thickness of the waterproofing layer meets the waterproofing performance requirements. Thus, it is necessary to apply water pressure to the cracked reinforced concrete structure according to this invention to test the waterproofing layer's impermeability.

[0015] Preferably, the load application system includes weights, an electro-hydraulic servo actuator, a portal beam, and a beam support; the weights are stacked on the top surface of the sealing steel plate, and the portal beam includes a horizontally arranged beam and vertically arranged legs; the electro-hydraulic servo actuator presses down on the top surface of the portal beam and transmits force to the concrete beam through the beam support at the bottom of the portal beam, causing the concrete beam to crack under the pressure of the electro-hydraulic servo actuator.

[0016] The technical principles and effects of the above invention are as follows: (1) The difficulty of the test system is that when water pressure is applied, it can ensure the sealing of the water injection without affecting the stress of the concrete beam. If the commonly used method of pre-embedding screws in the concrete beam to tighten the sealing steel plate is adopted, or the method of pre-drilling holes to insert tie rods and tightening bolts to apply pressure to the sealing steel plate is adopted, then the concrete beam, screws and sealing steel plate form a rigid connection system, which causes part of the load of the electro-hydraulic servo actuator to be transferred to the sealing steel plate by the screws. The stress of the concrete beam is no longer clear, which is not conducive to calculating the stress and crack width of the concrete beam. However, the present invention achieves sealing by using weights to apply gravity loading, which can ensure that the sealing ring is in close contact with the lower waterproof layer and the upper sealing steel plate, thereby avoiding water seepage when pressurized. At the same time, the deformation of the concrete beam will only be transmitted through the sealing steel plate. The sealing ring transfers a relatively small portion to the sealing steel plate above. Therefore, the sealing steel plate of the present invention will not share the load of the electro-hydraulic servo actuator, avoiding large errors and influences on the test, and providing conditions for precise control of the load actually acting on the concrete beam. In addition, the present invention uses the weight pressure sealing method, which can also realize the reuse of the test equipment and reduce costs. It avoids the material waste caused by the inconvenience of screw removal due to the pre-embedded screw tightening method, and also avoids the problem of corrosion of the waterproof layer caused by the use of adhesive sealing and the need to cut the sealing ring when disassembling, which affects its reuse. (2) Using the electro-hydraulic servo actuator for loading can easily realize the short-term, rapid, automatic loading and holding of the load, which is more in line with the actual situation than the loading method of using jacks and reaction frames.

[0017] Preferably, the weights are symmetrically stacked on the outside of the sealing ring along the longitudinal middle section of the concrete beam; a temporary support rod is provided between the sealing steel plate and the top surface of the concrete beam, the lateral dimension of the temporary support rod is larger than the lateral width of the concrete beam, the temporary support rod is located on the outside of the sealing ring, the temporary support rod is used to temporarily support the sealing steel plate to prevent overturning when the weights are stacked, and the temporary support rod is removed after the weights are stacked.

[0018] The technical principles and effects of the above invention are as follows: (1) Because the bottom surface of the weight is large, when the weight is stacked on the outside of the sealing ring, the material usage of the sealing ring and waterproof layer can be significantly reduced compared with the material usage on the inside of the sealing ring. The vertical projection cross-sectional area of ​​the sealing ring is also smaller, thereby reducing the amount of weight used. In the end, the material usage and weight stacking height of each waterproof layer crack resistance test specimen are significantly saved, the test cost is reduced and the test process is simplified; (2) When the transverse dimension of the temporary pad is greater than the transverse width of the concrete beam, the temporary pad can be removed by hammering it outward with a hammer.

[0019] Preferably, the distribution beam support includes a steel pad, a steel roller, a limiting rib, and a sand layer. The steel roller is located between two steel pads, the steel pad above the steel roller is the first steel pad, and the steel pad below the steel roller is the second steel pad. The limiting ribs are all welded to the surface of the steel pads. There is a gap between the limiting rib on one side of the portal-shaped distribution beam and the steel roller, and the limiting rib on the other side of the portal-shaped distribution beam is in close contact with the steel roller. The sand layer is a layer of fine sand laid on the bottom surface of the second steel pad.

[0020] The technical principles and effects of the above invention are as follows: (1) When the limiting rib is not in direct contact with the steel roller, it can ensure that the steel roller can roll a certain distance along the steel pad, thereby simulating the movable hinge support, and at the same time avoiding the accident of the roller rolling out of the steel pad and causing sudden collapse; (2) When the limiting rib is in direct contact with the steel roller, it can restrict the rolling of the roller, and the sliding friction between the steel roller and the steel pad is greater than the rolling friction, so the steel pad above the roller will not slide relative to the roller, but will only rotate along the roller surface with the deformation of the upper portal beam, thus simulating the fixed hinge support; (3) The surface roughness of the concrete is large. After sand is laid between the steel pad and the concrete, it can ensure that the steel pad and the top surface of the concrete beam are in uniform contact, avoiding the gap between the two and causing uneven force and inconsistent with the actual force; (4) The limiting rib is preferably a plain round steel bar.

[0021] Preferably, the bottom surface of the concrete beam at the longitudinal center has a notch, and the transverse projection shape of the notch includes triangle, rectangle, trapezoid and semicircle.

[0022] The technical principle and effect of the above invention are as follows: after a notch is set in the concrete beam, the bending stiffness of the section at the notch is less than that at the non-notch, and correspondingly the tensile stress at the notch is greater than that at the non-notch, so as to ensure that cracks appear in the area covered by the waterproof layer.

[0023] Preferably, the support system includes a fixed hinge support and a movable hinge support, wherein the fixed hinge support and the movable hinge support are symmetrically arranged along the longitudinal middle section of the concrete beam, and the movable hinge support allows the concrete beam to slide longitudinally.

[0024] The technical principle and effect of the above invention are as follows: the movable hinge support is preferably a cylindrical steel bar, so that the steel bar at the movable hinge support can roll. At this time, the corresponding rolling friction force is small, so as to reduce the influence of the support friction on the concrete beam when it is calculated as a simply supported beam.

[0025] Preferably, the inner and outer contours of the vertical projection shape of the sealing ring are rectangular or circular, and the material of the sealing ring is polyurethane or water-swellable rubber.

[0026] The technical principle and effect of the above invention are as follows: the use of water-swellable rubber can better fill the gap between the sealing ring and the lower waterproof layer and the upper sealing steel plate.

[0027] This invention also provides an automatic control and testing method for a waterproofing layer testing system, characterized in that the automatic control and testing method is implemented based on the above-mentioned concrete structure waterproofing layer testing system, and includes the following steps:

[0028] S1. The cross-sectional width of the concrete beam is b and the vertical height is h. The tension side of the concrete beam is provided with n steel bars with a diameter of d. The net distance between the steel bars and the top surface of the concrete beam is c, and strain gauges are pre-embedded in the longitudinal middle of the steel bars.

[0029] S2. Apply a waterproof layer and cover the longitudinal center of the top surface of the concrete beam, and cure it in accordance with the specifications.

[0030] S3. Place the concrete beam above the fixed hinge support and the movable hinge support of the support system, with a longitudinal distance of l between the fixed hinge support and the movable hinge support. z The longitudinal mid-section of the concrete beam is located at a distance l from the fixed hinge support. z / 2 places;

[0031] S4. Place the sealing ring on top of the waterproof layer, with a longitudinal length of l. q And the longitudinal direction of the sealing ring l q / 2 is aligned vertically with the longitudinal center section of the concrete beam; temporary pads are placed on both sides of the sealing ring, the temporary pads extend beyond the concrete beam at both ends in the lateral direction, and the top surface of the temporary pads is higher than the top surface of the sealing ring with a vertical height difference not exceeding 5mm.

[0032] S5. For longitudinal lengths greater than l q A sealing steel plate is placed on the top surface of the temporary pad, and the sealing steel plate has vertically penetrating water injection holes and vent holes within the vertical projection range of the sealing ring.

[0033] S6. Place weights symmetrically on the top surface of the sealing steel plate, then hammer the part of the temporary pad that extends beyond the concrete beam in the longitudinal direction until the temporary pad is hammered out of the vertical projection range of the sealing steel plate, and then remove the temporary pad.

[0034] S7. Connect the water injection pipe to the pressure testing instrument and connect it to the water injection hole of the sealing steel plate. Inject water into the cavity formed by the sealing steel plate, the waterproof layer and the sealing ring until water overflows from the vent hole. Then seal the vent hole through the airtight valve. Increase the water pressure to the design pressure value p through the pressurization equipment. If water leakage occurs at the sealing ring during the process of increasing the water pressure, continue to add weights. Otherwise, go to S8.

[0035] S8. Place the second steel pad on the sand layer on the top surface of the concrete beam. Stack the steel roller and the first steel pad on the second steel pad in sequence. The longitudinal distance from the center line of the steel roller of the distribution beam to the adjacent support system is l. b The distance from the centerline of the steel roller of the distribution beam to the adjacent end of the concrete beam is l. x Press the portal-shaped distribution beam against the top surface of the distribution beam support, and press the electro-hydraulic servo actuator against the longitudinal center of the portal-shaped distribution beam, so that the pressure of the electro-hydraulic servo actuator is maintained at F. min F min ≤2kN;

[0036] S9. Within 1 second, the pressure of the electro-hydraulic servo actuator is increased from F. min Increase to F max1 F max1 ={M u1 +(G f +G m +pS)l z / 8·(2-l q / l z )+bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), where M u1 G is the design bending moment of the concrete beam. f G is the total weight of the weights. g γ is the total weight of the steel plate used for sealing, S is the vertical projected area enclosed by the inner surface of the sealing ring, and γ is the unit weight of the concrete beam.

[0037] S10. Calculate the average strain ε of the n steel bars based on the real-time data from the strain gauges. a1 If ε a1 <ε s =M u1 / [0.87nπd 2 / 4·(hc)] / E s If yes, then proceed to S11; otherwise, proceed to S13.

[0038] S11. Increase the pressure of the electro-hydraulic servo actuator to F within 1 second. max2 F max2 ={ε s / ε a1 ·M u1 +(G f +G m +pS)l z / 8·(2-lq / l z )+bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), Calculate the average strain ε of n steel bars based on the real-time data from the strain gauges. a2 If ε a2 <ε s If yes, then proceed to S12; otherwise, proceed to S13.

[0039] S12, let ε a1 =ε a2 And transfer to S11;

[0040] S13. Keep the current pressure of the electro-hydraulic servo actuator unchanged until the specified time is reached, and record whether water seepage occurs at the cracks in the concrete beam.

[0041] S14. If no water seepage occurs at the cracks in the concrete beam, the waterproof layer is deemed to meet the design requirements under the test conditions; otherwise, it is deemed not to meet the design requirements.

[0042] S15. Remove all testing equipment and end the waterproofing layer test.

[0043] The technical principles and effects of the above invention are as follows: (1) For the replicated stress structure system formed by concrete beams, weights, water pressure, electro-hydraulic servo actuators, etc., after load decomposition and effect superposition calculation according to structural mechanics theory, the force balance equation can be obtained as M u1 =F max1 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ], thus deduce F max1 (2) The value of the steel bar strain ε obtained from the laboratory cracking test; a1 The standard formula takes into account the strain ε of the steel reinforcement in actual concrete structures after long-term loading. s There are differences, therefore when εa1 <ε s Corrections may be necessary, depending on... Figure 5 The test results show that the strain of the steel bars changes basically linearly after the concrete cracks, and the extension line of the mean strain change line of each steel bar almost passes through the origin. Therefore, it can be calculated according to M. u2 =F max2 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]≈ε s / ε a1 ·M u1 The load on the electro-hydraulic servo actuator is adjusted to F to more closely resemble the actual situation. max2 (3) Considering the error between theory and practice, the initial correction of F max2 The ε generated below a2 It may still be less than ε s At this point, multiple iterations are required to further correct the load on the electro-hydraulic servo actuator. Since the load on the electro-hydraulic servo actuator is usually controlled by a computer, it is convenient to program according to this invention to achieve automatic control and accurately and quickly correct the actual average value of the steel reinforcement strain to ε. s A suitable value, avoiding manual adjustment of F max2 The wasted time and the inability to quickly and accurately apply to ε s Errors caused by values.

[0044] Preferably, M in S9 u1 Calculated based on the basic combination value of the most unfavorable load borne by the concrete beam.

[0045] The technical principle and effect of the above invention are as follows: Because the cracking of the waterproof layer is different from the cracking of the reinforced concrete structure, although the cracks in the reinforced concrete structure will expand to a large width value under the most unfavorable load combination, the cracks will be pulled back to a smaller width value by the steel bars after the load is unloaded. The size of the crack width mainly affects the durability of the steel bars. Therefore, when verifying the crack width of concrete, the load frequent combination value for verifying the durability of the structure is generally taken, rather than the load basic combination value for verifying the bearing capacity of the structure. However, the cracking of the waterproof layer is mainly a problem of crack height. The higher the crack expands, the worse the seepage prevention performance of the waterproof layer. Moreover, when the cracks in the reinforced concrete structure recover to a smaller width value, the crack height of the waterproof layer will not recover. Therefore, for the test load of the crack resistance performance of the waterproof layer, the most unfavorable load basic combination value borne by the reinforced concrete structure below should be applied.

[0046] Preferably, before performing step S13, the crack width at the location of the reinforcing bar is measured using a crack observation instrument and recorded as W0. If W0 > W s W s If the crack width of the concrete beam is calculated according to the relevant industry standard under the combined force of the current electro-hydraulic servo actuator pressure and the test equipment, then proceed to S13; otherwise, increase the pressure of the electro-hydraulic servo actuator to F within 1 second. max3 F max3 ={W s / W0·M u1 +(G f +G m +pS)l z / 8·(2-l q / l z )+bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), then turn to S13.

[0047] The technical principle and effect of the above invention are as follows: taking into account the error between theory and practice, the corrected F max2 The resulting W0 may still be smaller than W. s And W s To standardize the formula and account for the crack width of actual concrete structures after long-term loading, W0 should still be based on W, which is closer to the actual value. s Make corrections; according to Figure 5The test results show that the strain of the steel bars changes basically linearly after concrete cracking, and the extension line of the mean strain change line of each steel bar almost passes through the origin. Since the crack width of concrete structures is usually proportional to the strain of the steel bars, it can be assumed that the crack change of concrete beams also conforms to this law. Therefore, it can be calculated according to M... u3 =F max3 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]=W s / W0·M u1 The load on the electro-hydraulic servo actuator is adjusted to F to more closely resemble the actual situation. max3 .

[0048] Preferably, after executing step S13, the pressure of the electro-hydraulic servo actuator decreases from the current value to F. min Then increase to F max1 This process continues until the number of iterations reaches the required design value, at which point the loop stops, and then proceeds to S14.

[0049] The technical principle and effect of the above invention are as follows: Considering that actual concrete structures, especially bridge structures, may be subjected to cyclic live loads, the fatigue resistance and crack resistance of the waterproof layer under cyclic loads should be further tested to verify its waterproof performance retention effect under long-term repeated loads.

[0050] The beneficial effects of this invention are:

[0051] I. Based on the mechanism of concrete cracking leading to waterproofing layer cracking, this invention provides a crack resistance testing system for waterproofing layers. This system can rapidly load reinforced concrete beams and cause them to crack to simulate the actual cracking of concrete. The waterproofing layer is applied before the concrete cracks to verify the impact of instantaneous concrete cracking on the waterproofing layer. At the same time, it can verify the impermeability of the waterproofing layer under a preset water pressure. It can facilitate the guidance and verification of waterproofing design of reinforced concrete structures, achieve long-term performance maintenance, and significantly extend service life. It is applicable to bridges, roads, tunnels, buildings, and hydraulic structures.

[0052] Second, this invention achieves water injection sealing by using weights for gravity loading, ensuring tight contact between the sealing ring and the lower waterproof layer and the upper sealing steel plate to prevent water leakage during pressurization. Simultaneously, the deformation of the concrete beam is only transmitted to a relatively small portion of the upper sealing steel plate through the sealing ring. Therefore, the sealing steel plate of this invention essentially does not share the load of the electro-hydraulic servo actuator. Applying water pressure ensures water injection sealing without affecting the stress on the concrete beam, thus avoiding significant errors and impacts on the experiment. This provides a guarantee for precise control of the actual load acting on the concrete beam and enables efficient reusability of the testing equipment, reducing costs.

[0053] Third, based on the concrete structure waterproofing layer test system of the present invention, the present invention also provides its automatic control and test method. Using this method, the test load of the concrete beam can be applied quickly and accurately to the most unfavorable load combination value that it may encounter in practice, and the crack width of the tested reinforced concrete beam can be quickly corrected to its actual crack width value under long-term repeated loading. At the same time, a program can be compiled according to the test method and the proposed formula of the present invention to facilitate the automatic control and rapid correction of the test load, avoiding the time wasted by manually adjusting the test load and the error caused by the inability to quickly and accurately apply the correction value. Attached Figure Description

[0054] Figure 1 This is a schematic diagram of a concrete beam with a waterproof layer and reinforcing steel bars, and its cracks, which are common in the background art of this invention.

[0055] Figure 2 This is a schematic diagram of the overall structure of the concrete structure waterproofing layer test system of the present invention;

[0056] Figure 3 This is a schematic cross-sectional view of the concrete structure waterproofing layer test system at point AA of the present invention;

[0057] Figure 4 This is a schematic cross-sectional view of the concrete structure waterproofing layer test system at point BB of the present invention;

[0058] Figure 5 This is the load-steel strain curve of a reinforced concrete beam tested in the concrete structure waterproofing layer test system of this invention.

[0059] Explanation of reference numerals in the attached figures:

[0060] 1. Concrete beam; 111. Notch; 12. Reinforcing steel; 13. Crack;

[0061] 2. Waterproof layer;

[0062] 3. Interface;

[0063] 4. Support system; 41. Fixed hinge support; 42. Movable hinge support;

[0064] 5. Sealing ring; 52. Temporary gasket;

[0065] 6. Sealing steel plate; 61. Water injection hole; 62. Vent hole;

[0066] 7. Load application system; 71. Weights; 72. Electro-hydraulic servo actuator; 73. Portal distribution beam; 74. Distribution beam support;

[0067] 741. Steel pad; 742. Steel roller; 743. Limiting rib; 744. Sand layer;

[0068] 8. Water pressure application system; 81. Water injection pipe; 82. Pressure testing instrument; 83. Sealing valve. Detailed Implementation

[0069] The present invention will be further described in detail below with reference to experimental examples and specific embodiments. However, it should not be construed as the scope of the above-mentioned subject matter of the present invention being limited to the following embodiments. All technologies implemented based on the content of the present invention are within the scope of the present invention.

[0070] Example A

[0071] like Figure 2 As shown, a test system for a concrete structure waterproofing layer includes a concrete beam 1, a waterproofing layer 2, a support system 4, a sealing ring 5, a sealing steel plate 6, a load application system 7, and a water pressure application system 8. The longitudinal direction is along the length of the concrete beam 1, the gravity direction is vertical, and the transverse direction is orthogonal to both the longitudinal and vertical directions. Reinforcing bars 12 are longitudinally arranged near the top surface of the concrete beam 1. The support system 4 supports the bottom surface of the concrete beam 1. The waterproofing layer 2 covers the top surface of the concrete beam 1 at the longitudinal center, forming an interface 3 between the waterproofing layer 2 and the concrete beam 1. A sealing ring 5 is provided on the top surface of the waterproofing layer 2. The surface pressure is provided with a sealing steel plate 6, which has a vertically penetrating water injection hole 61 and an air vent 62 within the vertical projection range of the sealing ring 5; the load application system 7 is set on the concrete beam 1 and can apply pressure to the concrete beam 1 to cause cracks 13 to appear on the top surface of the concrete beam 1; the water pressure application system 8 includes a water injection pipe 81, a pressure testing instrument 82, and a sealing valve 83. The water injection pipe 81 is connected to the water injection hole 61 of the sealing steel plate 6, the pressure testing instrument 82 is installed on the water injection pipe 81 for testing water pressure, and the sealing valve 83 is installed on the air vent 62 of the sealing steel plate 6 for sealing the air vent 62.

[0072] In this embodiment, the concrete structure waterproofing layer test system, through the load application system 7, enables the test system to rapidly load the reinforced concrete 12 and cause it to crack, thereby simulating concrete cracking during actual use. The water pressure application system 8 allows the test system to apply water pressure to the cracked concrete beam 1 while the reinforced concrete 12 structure is cracking, testing the impermeability of the partially cracked waterproofing layer 2. This avoids the influence of the water pressure application system 8 on the load-bearing structure of the concrete beam 1, thus preventing significant errors and impacts on the test. This ensures precise control of the load actually applied to the concrete beam 1, simulates the actual cracking of the concrete beam 1, verifies the impact of instantaneous cracking of concrete on the waterproofing layer 2, and verifies the impermeability of the waterproofing layer 2 under a preset water pressure. This facilitates the guidance and verification of the waterproofing design of the reinforced concrete 12 structure, achieving long-term performance maintenance and significantly extending its service life.

[0073] This concrete structure waterproofing layer test system is based on the mechanism by which concrete cracking leads to the cracking of the waterproofing layer 2. The study found that the essence of concrete cracking is that the distance between the concrete material molecules on both sides of the crack 13 in the concrete beam 1 suddenly changes from the nanometer level to the millimeter level that is visible to the naked eye. The interface 3 between the concrete and the waterproofing layer 2 is uneven at the microscopic level. The longitudinal interaction between the concrete and the waterproofing layer 2 includes the chemical adsorption force between the molecules, the static friction resistance, and the mutual compression and interlocking force. Therefore, the amount of slippage of the interface 3 between the concrete surface and the waterproofing layer 2 when the concrete cracks can be basically ignored. Thus, when the concrete crack 13 opens to both sides, it will also drive the waterproofing layer 2 to open to both sides of the crack 13. That is, the instant that the concrete cracks will have a tearing effect on the waterproofing layer 2, which will cause the distance between the material molecules on the bottom surface of the waterproofing layer 2 to suddenly change from the nanometer level to the millimeter level, that is, the distance increases by nearly 100,000 times and appears as a crack 13 that is visible to the naked eye. Of course, the increase in longitudinal distance will decrease rapidly as the vertical distance between the waterproof layer 2 molecules and the concrete surface increases. However, for the waterproof layer 2 material near the concrete surface, its 800% elongation at break performance is completely insufficient to withstand the nearly 100,000-fold increase in longitudinal distance. Therefore, when the concrete cracks, the waterproof layer 2 material near its surface will inevitably crack as well, and will stop cracking after cracking to a certain height. Therefore, the key to the waterproof performance of the reinforced concrete structure lies in whether the remaining uncracked thickness of the waterproof layer 2 can meet the waterproof performance requirements. Therefore, this test system applies water pressure at the same time as the concrete beam 1 cracks to test the impermeability of the waterproof layer 2 in order to verify the waterproof performance of the reinforced concrete structure.

[0074] Furthermore, the load application system 7 includes a weight 71, an electro-hydraulic servo actuator 72, a portal-shaped distribution beam 73, and a distribution beam support 74; the weight 71 is placed on the sealing steel plate 6 to press the sealing steel plate 6 and the waterproof layer 2 together by gravity; the distribution beam support 74 is located at the bottom of the portal-shaped distribution beam 73; the electro-hydraulic servo actuator 72 is ballasted on the top surface of the portal-shaped distribution beam 73 and is loaded onto the concrete beam 1 through the portal-shaped distribution beam 73 and the distribution beam support 74 so that the concrete beam 1 can generate cracks 13.

[0075] In this embodiment, the load application system 7 uses weights 71 placed on the sealing steel plate 6 to achieve water injection and sealing by gravity loading. This ensures that the sealing rings 5 ​​are in close contact with the lower waterproof layer 2 and the upper sealing steel plate 6 to prevent water leakage during pressurization. At the same time, the deformation of the concrete beam 1 is only transmitted to a relatively small portion of the sealing rings 5 ​​to the sealing steel plate 6 located above the sealing rings 5. This effectively prevents the sealing steel plate 6 from sharing the load applied by the electro-hydraulic servo actuator 72, ensuring water injection sealing without affecting the stress on the concrete beam 1. This avoids large errors and impacts on the test, provides a guarantee for precise control of the actual load acting on the concrete beam 1, and enables efficient reusability of the test equipment, thereby reducing costs. Furthermore, the method of sealing with weights 71 in this invention enables the reuse of the testing equipment, reducing costs. It avoids the material waste caused by the inconvenience of removing pre-embedded screws, which is a problem with traditional methods. It also avoids the corrosion of the waterproof layer 2 caused by adhesive sealing and the need to cut the sealing ring 5 during disassembly, thus preventing reuse. This further improves the utilization rate of testing materials and reduces testing costs. The use of an electro-hydraulic servo actuator 72 for loading in this testing system further facilitates load application, enabling short-term, rapid, and automatic loading and holding of the load on the concrete beam 1. Compared to using jacks and reaction frames, this method offers more precise control and a faster response.

[0076] See Figure 3 and Figure 4 The weights 71 are symmetrically stacked on the outside of the sealing ring 5 along the cross section at the middle of the longitudinal direction of the concrete beam 1; a temporary pad 52 is provided between the sealing steel plate 6 and the top surface of the concrete beam 1. The transverse dimension of the temporary pad 52 is larger than the transverse width of the concrete beam 1. The temporary pad 52 is located on the outside of the sealing ring 5. The temporary pad 52 is used to support the sealing steel plate 6 to prevent overturning when the weights 71 are stacked.

[0077] In this embodiment, the load application system 7 places the weights 71 on the outside of the sealing ring 5. Compared to placing the weights 71 on the inside of the sealing ring 5, this significantly reduces the material usage of the sealing ring 5 and the waterproof layer 2, and also reduces the vertical projected cross-sectional area of ​​the sealing ring 5, thereby reducing the amount of weights 71 used. This significantly saves material usage and weight stacking height for each waterproof layer 2 crack resistance test specimen, lowers test costs, and simplifies the test procedure. When the lateral dimension of the temporary pad 52 is larger than the lateral width of the concrete beam 1, it is convenient to remove the temporary pad 52 by hammering it outwards. In a preferred embodiment, the inner and outer contours of the vertical projected shape of the sealing ring 5 are rectangular or circular. The material of the sealing ring 5 is preferably polyurethane or water-swellable rubber. Using water-swellable rubber can better fill the gap between the sealing ring 5 and the lower waterproof layer 2 and the upper sealing steel plate 6.

[0078] like Figure 2 As shown, the distribution beam support 74 includes a steel pad 741, a steel roller 742, a limiting rib 743, and a sand layer 744. The steel roller 742 is located between two steel pads 741. The steel pad 741 above the steel roller 742 is the first steel pad 741, and the steel pad 741 below the steel roller is the second steel pad 741. The limiting ribs 743 are all welded to the surface of the steel pads 741. There is a gap between the limiting rib 743 on one side of the portal-shaped distribution beam 73 and the steel roller 742, and the limiting rib 743 on the other side of the portal-shaped distribution beam 73 is in close contact with the steel roller 742. The sand layer 744 is a layer of fine sand laid on the bottom surface of the second steel pad 741.

[0079] In this embodiment, when the limiting rib 743 does not contact the steel roller 742, it can effectively ensure that the steel roller 742 can roll a certain distance along the steel pad 741 to simulate the movable hinge support 42. At the same time, the setting of the limiting rib 743 can limit the steel roller 742 and the steel pad 741, avoiding the accident of sudden collapse caused by the steel roller 742 rolling out of the range of the steel pad 741. When the limiting rib 743 is in direct contact with the steel roller 742, the limiting rib 743 can effectively restrict the rolling of the steel roller 742. At this time, the sliding friction between the steel roller 742 and the steel pad 741 is greater than the rolling friction between the steel roller 742 and the steel pad 741. Therefore, the first steel pad 741 above the steel roller 742 is fixed to the steel roller 742. The first steel pad 741 will only rotate along the surface of the steel roller 742 with the deformation of the portal beam 73 above, thereby simulating the fixed hinge support 41. Furthermore, due to the large roughness of the concrete surface, after spreading sand between the steel pad 741 and the concrete, it can ensure that the steel pad 741 and the top surface of the concrete beam 1 are in uniform contact, avoiding the gap between the two and causing uneven stress that does not match the actual stress. In a preferred embodiment, the limiting rib 743 is preferably a plain round steel bar 12.

[0080] like Figure 2 As shown, a notch 111 is provided at the bottom surface of the longitudinal center of the concrete beam 1. The transverse projection shape of the notch 111 includes triangle, rectangle, trapezoid, and semicircle. In this embodiment, after the notch 111 is provided in the concrete beam 1, the bending stiffness of the section at the notch 111 is less than that at the non-notch 111, and correspondingly the tensile stress at the notch 111 is greater than that at the non-notch 111, so as to ensure that the crack 13 appears in the area covered by the waterproof layer 2.

[0081] See Figure 2 The support system 4 includes a fixed hinge support 41 and a movable hinge support 42. The fixed hinge support 41 and the movable hinge support 42 are symmetrically arranged along the longitudinal middle section of the concrete beam 1. The fixed hinge support 41 abuts against the concrete beam 1, and the movable hinge support 42 is movably connected to the concrete beam 1 so that the concrete beam 1 can move in the longitudinal direction. The movable hinge support 42 is preferably a cylindrical steel bar, so that the steel bar at the movable hinge support 42 can roll. This results in a smaller rolling friction force, reducing the influence of support friction on the stress calculation of the concrete beam 1 as a simply supported beam.

[0082] Example B

[0083] The present invention also provides an automatic control and testing method for a waterproof layer 2 test system. The automatic control and testing method is based on the aforementioned concrete structure waterproof layer test system and includes the following steps:

[0084] S1. The cross-sectional width of concrete beam 1 is b and the vertical height is h. There are n steel bars 12 with a diameter of d on the tension side of concrete beam 1. The net distance between the steel bars 12 and the top surface of concrete beam 1 is c, and strain gauges are pre-embedded in the longitudinal middle of the steel bars 12.

[0085] S2. Install waterproof layer 2 to cover the longitudinal center of the top surface of concrete beam 1, and cure it in accordance with the specifications.

[0086] S3. Place the concrete beam 1 above the fixed hinge support 41 and the movable hinge support 42 of the support system 4, with a longitudinal distance of l between the fixed hinge support 41 and the movable hinge support 42. z The longitudinal mid-section of concrete beam 1 is located at a distance of 41l from the fixed hinge support. z / 2 places;

[0087] S4. Place the sealing ring 5 on the top surface of the waterproof layer 2. The longitudinal length of the sealing ring 5 is l. q And the longitudinal direction of the sealing ring 5 l q / 2 is aligned vertically with the longitudinal middle section of the concrete beam 1; temporary pads 52 are placed on both sides of the sealing ring 5, and the temporary pads 52 extend beyond the concrete beam 1 at both ends in the transverse direction. The top surface of the temporary pads 52 is higher than the top surface of the sealing ring 5 and the vertical height difference does not exceed 5mm.

[0088] S5. For longitudinal lengths greater than l q The sealing steel plate 6 is placed on the top surface of the temporary pad 52. The sealing steel plate 6 has a vertically penetrating water injection hole 61 and an exhaust hole 62 within the vertical projection range of the sealing ring 5.

[0089] S6. Place weights 71 symmetrically on the top surface of the sealing steel plate 6, and then apply an external force along the longitudinal direction to the part of the temporary pad 52 that extends beyond the concrete beam 1 in the transverse direction. The temporary pad 52 will undergo longitudinal displacement under the action of the external force until the temporary pad 52 moves outside the vertical projection range of the sealing steel plate 6, and then remove the temporary pad 52.

[0090] S7. Connect the water injection pipe 81 to the pressure testing instrument 82, and connect the water injection pipe 81 to the water injection hole 61 of the sealing steel plate 6. Inject water into the cavity formed by the sealing steel plate 6, the waterproof layer 2 and the sealing ring 5 until water overflows from the vent hole 62 and then seal the vent hole 62. Increase the water pressure to the design pressure value p. If water leakage occurs at the sealing ring 5 during the process of increasing the water pressure, continue to add weight 71 until water no longer leaks at the sealing ring 5. Otherwise, go to S8.

[0091] S8. Place the second steel pad 741 on the sand layer 744 on the top surface of the concrete beam 1. Stack the steel roller 742 and the first steel pad 741 on the second steel pad 741 in sequence. The longitudinal distance between the centerline of the steel roller 742 and the adjacent support system 4 is l. b The centerline of the steel roller 742 is l away from the adjacent end of the concrete beam 1. x The portal-shaped distribution beam 73 is pressed against the top surface of the distribution beam support 74, and the electro-hydraulic servo actuator 72 is pressed against the longitudinal center of the portal-shaped distribution beam 73, so that the pressure of the electro-hydraulic servo actuator 72 is maintained at F. min F min ≤2kN;

[0092] S9. Within 1 second, the pressure applied to the distribution beam by the electro-hydraulic servo actuator 72 is transferred from F... min Increase to F max1 F max1 ={M u1 +(G f +G m +pS)l z / 8·(2-l q / l z )+bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), where M u1 G is the design bending moment of concrete beam 1. f G is the total weight of the 71 weights. g γ is the total weight of the sealing steel plate 6, S is the vertical projected area enclosed by the inner surface of the sealing ring 5, and γ is the unit weight of the concrete beam 1.

[0093] S10. Calculate the average strain ε of n steel bars 12 based on the real-time data of the embedded strain gauges. a1 If ε a1 <ε s =M u1 / [0.87nπd 2 / 4·(hc)] / E s Then go to S11; if ε a1 ≥ε s =M u1 / [0.87nπd 2 / 4·(hc)] / E s Then proceed to S13;

[0094] S11. Within 1 second, increase the pressure applied to the distribution beam by the electro-hydraulic servo actuator 72 to F. max2 F max2 ={ε s / ε a1 ·M u1 +(G f +G m +pS)l z / 8·(2-l q / l z )+bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), calculate the average strain ε of n steel bars 12 based on the real-time data of the embedded strain gauges. a2 If ε a2 <ε s Then go to S12; if ε a2 ≥ε s Then proceed to S13;

[0095] S12, let ε a1 =ε a2And transfer to S11;

[0096] S13. Keep the pressure of the current electro-hydraulic servo actuator 72 unchanged until the specified time is reached, and record whether water seepage occurs at the crack 13 of the concrete beam 1.

[0097] S14. If no water seepage occurs at crack 13 in concrete beam 1, the waterproof layer 2 is deemed to meet the design requirements under the test conditions; otherwise, it is deemed not to meet the design requirements.

[0098] S15. Remove all test equipment and end the waterproof layer 2 test.

[0099] In this embodiment, for the load-bearing structural system formed by the concrete beam 1, the weight 71, the hydraulic pressure, and the electro-hydraulic servo actuator 72, after load decomposition and effect superposition calculation according to structural mechanics theory, the force balance equation can be obtained as M. u1 =F max1 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ], and thus obtain F max1 Regarding the strain of steel bar 12 in step S10, the strain ε of steel bar 12 obtained from the laboratory cracking test... a1 The standard formula takes into account the strain ε of the steel reinforcement after long-term loading in actual concrete structures. s There are differences, therefore when ε a1 <ε s Corrections may be necessary, depending on... Figure 5 The test results show that the strain of the reinforcing steel bar 12 after concrete cracking is basically linear, and the extension line of the mean strain variation line of each reinforcing steel bar 12 is close to passing through the origin. Therefore, it can be calculated according to M... u2 =F max2 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z2 / 8·[1-4(l x +l b ) 2 / l z 2 ]≈ε s / ε a1 ·M u1 The load on the electro-hydraulic servo actuator 72 is corrected to be closer to the actual situation. max2 After correcting the load on the electro-hydraulic servo actuator 72, the average strain ε of the n steel bars 12 is calculated again based on the real-time data from the strain gauges. a2 Taking into account the discrepancy between theory and practice, the initial revised F max2 The ε generated below a2 It may still be less than ε s At this point, multiple iterations are required to further correct the load on the electro-hydraulic servo actuator 72. Since the load on the electro-hydraulic servo actuator 72 is usually controlled by a computer, it is convenient to program according to this invention to achieve automatic control and accurately and quickly correct the actual average strain of the steel bar 12 to ε. s A suitable value, avoiding manual adjustment of F max2 The wasted time and the inability to quickly and accurately apply to ε s Error caused by the value of ε. Multiple iterations of ε a2 Until ε a2 Not less than ε s Then, a water seepage test was conducted at crack 13 in concrete beam 1 to verify the results.

[0100] In a preferred embodiment, M in S9 u1 The calculation is based on the basic combination value of the most unfavorable load borne by concrete beam 1. Since the cracking of waterproof layer 2 differs from the cracking of the reinforced concrete structure 12, although the crack 13 in the reinforced concrete structure 12 will expand to a large width under the most unfavorable load combination, it will be pulled back to a smaller width by the reinforcing steel 12 after the load is unloaded. The width of crack 13 mainly affects the durability of the reinforcing steel 12. Therefore, when verifying the width of concrete crack 13, the frequently encountered load combination value for verifying structural durability is generally used, rather than the basic load combination value for verifying structural bearing capacity. However, the cracking of waterproof layer 2 is mainly a matter of crack height 13. The higher the crack 13 in waterproof layer 2 expands, the worse its seepage prevention performance. Furthermore, when the crack 13 in the reinforced concrete structure 12 recovers to a smaller width, the height of crack 13 in waterproof layer 2 will not recover. Therefore, the test load for the crack resistance performance of waterproof layer 2 should be applied according to the basic combination value of the most unfavorable load borne by the reinforced concrete structure 12 below it.

[0101] Further, before step S13, the width of crack 13 at the location of rebar 12 is measured using a crack 13 observation instrument and recorded as W0. If W0 > W s W s Given the combined force of the current electro-hydraulic servo actuator 72 pressure and the testing equipment, the crack width 13 of the concrete beam 1 calculated according to the relevant industry standard is then used; if W0≤W s Then, within 1 second, the pressure of the electro-hydraulic servo actuator 72 will be increased to F. max3 F max3 ={W s / W0·M u1 +(G f +G m +pS)l z / 8·(2-l q / l z )+ bhγl z 2 / 8·[1-4(l x +l b ) 2 / l z 2 ]} / (l b / 2), then turn to S13.

[0102] In this implementation, taking into account the error between theory and practice, the corrected F max2 The resulting W0 may still be smaller than W. s And W s To standardize the formula and account for the actual crack width of concrete structures after long-term loading, W0 should still be based on W, which is closer to the actual value. s Make corrections; according to Figure 5 The test results show that the strain of the reinforcing steel 12 changes basically linearly after concrete cracking, and the extension line of the average strain change line of each reinforcing steel 12 is close to passing through the origin. Since the width of the crack 13 in the concrete structure is usually proportional to the strain of the reinforcing steel 12, it can be considered that the change of the crack 13 in the concrete beam 1 also conforms to this law. Therefore, it can be assumed that M... u3 =F max3 l b / 2-(G f +G m +pS) / l q ·l q l z / 8·(2-l q / l z )-bhγl z 2 / 8·[1-4(l x +l b ) 2 / lz 2 ]=W s / W0·M u1 The load on the electro-hydraulic servo actuator 72 is corrected to be closer to the actual situation. max3 .

[0103] In a preferred embodiment, after step S13, the pressure of the electro-hydraulic servo actuator 72 decreases from its current value to F. min Then increase to F max1 The process is repeated until the required number of cycles is reached, at which point the cycle stops, and then proceed to step S14. Considering that actual concrete structures, especially bridge structures, may be subjected to cyclic live loads, the fatigue and crack resistance of waterproof layer 2 under cyclic loading are further tested to verify its waterproof performance retention under long-term repeated loading.

[0104] Based on the concrete structure waterproofing layer test system of the present invention, the present invention also provides its automatic control and test method. Through this method, the test load of the concrete beam 1 is quickly and accurately applied to the most unfavorable load combination value that it may encounter in practice, and the width of the crack 13 of the reinforced concrete beam 12 is quickly corrected to the actual crack 13 width value under long-term repeated loading, so as to verify the impermeability of the waterproofing layer 2 when the reinforced concrete structure cracks in actual use. At the same time, a program can be compiled according to the test method and the proposed formula of the present invention to facilitate the automatic control and rapid correction of the test load, avoiding the time wasted by manually adjusting the test load and the error caused by the inability to quickly and accurately apply the correction value.

[0105] The above are merely preferred embodiments of the present invention and are 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 within the protection scope of the present invention.

Claims

1. An automatic control and testing method for a concrete structure waterproofing layer testing system, characterized in that, The concrete structure waterproofing layer test system includes a concrete beam, a waterproofing layer, a support system, a sealing ring, a sealing steel plate, a load application system, and a water pressure application system; the longitudinal direction is along the length of the concrete beam, the vertical direction is the gravity direction, and the transverse direction is orthogonal to both the longitudinal and vertical directions. The concrete beam is reinforced with steel bars along its longitudinal direction near the top surface. The support system is supported on the bottom surface of the concrete beam. The waterproof layer covers the longitudinal center of the top surface of the concrete beam, and an interface is formed between the waterproof layer and the concrete beam. The top surface of the waterproof layer is provided with the sealing ring; the top surface of the sealing ring is pressed with the sealing steel plate, and the sealing steel plate is provided with vertically penetrating water injection holes and air vents within the vertical projection range of the sealing ring; The load application system is installed on the concrete beam and is capable of applying pressure to the concrete beam to cause cracks to appear on the top surface of the concrete beam; The water pressure application system includes a water injection pipe, a pressure testing instrument, and a sealing valve. The water injection pipe is connected to the water injection hole of the sealing steel plate. The pressure testing instrument is installed on the water injection pipe for testing water pressure. The sealing valve is installed on the vent hole of the sealing steel plate for sealing the vent hole. The automatic control and testing method of the concrete structure waterproofing layer test system is implemented based on the concrete structure waterproofing layer test system, and the automatic control and testing method of the concrete structure waterproofing layer test system includes the following steps: S1, the cross-sectional width of the concrete beam is b Vertical height is h The tension side of the concrete beam is provided with n Root diameter is d The reinforcing bars, wherein the net distance between the reinforcing bars and the top surface of the concrete beam is... c And strain gauges are pre-embedded in the longitudinal middle of the reinforcing bars; S2. Install a waterproof layer covering the longitudinal center of the top surface of the concrete beam and cure it in accordance with the specifications; S3. Place the concrete beam above the fixed hinge support and the movable hinge support of the support system, wherein the longitudinal distance between the fixed hinge support and the movable hinge support is... l z The longitudinal mid-section of the concrete beam is located at a distance from the fixed hinge support. l z / 2 places; S4, the longitudinal length of the sealing ring is l q And the longitudinal direction of the sealing ring l q / 2 is aligned vertically with the longitudinal center section of the concrete beam; temporary pads are placed on both sides of the sealing ring, the temporary pads extend beyond the concrete beam at both ends in the lateral direction, and the top surface of the temporary pads is higher than the top surface of the sealing ring with a vertical height difference not exceeding 5mm. S5. The longitudinal length is greater than... l q A sealing steel plate is placed on the top surface of the temporary pad, and the sealing steel plate has a vertically penetrating water injection hole and an air vent within the vertical projection range of the sealing ring. S6. Place weights symmetrically on the top surface of the sealing steel plate, and then apply an external force longitudinally to the part of the temporary pad that extends laterally beyond the concrete beam. The temporary pad will undergo longitudinal displacement under the action of the external force until the temporary pad moves outside the vertical projection range of the sealing steel plate, and then remove the temporary pad. S7. Connect the water injection pipe to the pressure testing instrument and connect the water injection pipe to the water injection hole of the sealing steel plate. Inject water into the cavity formed by the sealing steel plate, the waterproof layer, and the sealing ring until water overflows from the vent hole, then seal the vent hole; and increase the water pressure to the design pressure value. p If water leakage occurs at the sealing ring during the process of increasing water pressure, continue to add weight until water no longer leaks at the sealing ring; otherwise, proceed to step S8. S8. Place the second steel pad on the sand layer on the top surface of the concrete beam, and then stack the steel roller and the first steel pad on the second steel pad in sequence. The centerline of the steel roller is at a longitudinal distance from the adjacent support system. l b The distance from the centerline of the steel roller to the adjacent end of the concrete beam is... l x Press the portal-shaped distribution beam against the top surface of the distribution beam support, and press the electro-hydraulic servo actuator against the longitudinal center of the portal-shaped distribution beam, maintaining the pressure of the electro-hydraulic servo actuator at a certain level. F min , F min ≤2kN; S9. Within 1 second, the pressure applied to the distribution beam by the electro-hydraulic servo actuator is transferred from... F min Increase to F max1 , F max1 ={ M u1 +( G f + G m + pS ) l z / 8·(2- l q / l z )+ bhγl z 2 / 8·[1-4( l x + l b ) 2 / l z 2 ]} / ( l b / 2), where M u1 The design bending moment of the concrete beam. G f The total weight of the weights. G m The total weight of the sealing steel plates, S It is the vertical projected area enclosed by the inner surface of the sealing ring. γ This is the unit weight of the concrete beam; S10. Calculate based on the real-time data of the embedded strain gauge. n The average strain of the steel reinforcement ε a1 ,like ε a1 < ε s = M u1 / [0.87 n π d 2 / 4·( h - c )] / E s Then switch to S11, where ε s , E s The standard formulas respectively consider the strain of steel bars and the corresponding elastic modulus of steel bars after long-term loading in actual concrete structures; if ε a1 ≥ ε s = M u1 / [0.87 n π d 2 / 4·( h - c )] / E s Then proceed to S13; S11. Within 1 second, increase the pressure applied to the distribution beam by the electro-hydraulic servo actuator to... F max2 , F max2 ={ ε s / ε a1 · M u1 +( G f + G m + pS ) l z / 8·(2- l q / l z )+ bhγl z 2 / 8·[1-4( l x + l b ) 2 / l z 2 ]} / ( l b / 2), Calculate based on the real-time data of the pre-embedded strain gauges. n Average strain of the reinforcing bar ε a2 ,like ε a2 < ε s Then go to S12; if ε a2 ≥ ε s Then proceed to S13; S12, Order ε a1 = ε a2 And transfer to S11; S13. Keep the current pressure of the electro-hydraulic servo actuator unchanged until the specified time is reached, and record whether water seepage occurs at the cracks in the concrete beam. S14. If no water seepage occurs at the cracks in the concrete beam, the waterproof layer is deemed to meet the design requirements under the test conditions; otherwise, it is deemed not to meet the design requirements. S15. Remove all testing equipment and end the waterproofing layer test.

2. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, The load application system includes weights, an electro-hydraulic servo actuator, a portal beam, and a beam support. The weight is placed on the sealing steel plate to press the sealing steel plate and the waterproof layer together by gravity. The distribution beam support is set at the bottom of the portal-shaped distribution beam. The electro-hydraulic servo actuator is pressed on the top surface of the portal-shaped distribution beam and loaded onto the concrete beam through the portal-shaped distribution beam and the distribution beam support so that the concrete beam can generate cracks.

3. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 2, characterized in that, The weights are symmetrically stacked on the outside of the sealing ring along the longitudinal middle section of the concrete beam. A temporary support rod is provided between the sealing steel plate and the top surface of the concrete beam. The lateral dimension of the temporary support rod is larger than the lateral width of the concrete beam. The temporary support rod is located outside the sealing ring. The temporary support rod is used to support the sealing steel plate to prevent it from tipping over when weights are stacked.

4. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 2, characterized in that, The distribution beam support includes a steel pad, a steel roller, a limiting rib, and a sand layer; The steel roller is located between the upper and lower steel pads. The steel pad above the steel roller is the first steel pad, and the steel pad below the steel roller is the second steel pad. The limiting ribs are all welded to the surface of the steel pads. There is a gap between the limiting rib on one side of the portal-shaped distribution beam and the steel roller, and the limiting rib on the other side of the portal-shaped distribution beam is in close contact with the steel roller. The sand layer is a layer of fine sand laid on the bottom surface of the second steel pad.

5. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, A notch is provided on the bottom surface at the longitudinal center of the concrete beam.

6. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, The support system includes a fixed hinge support and a movable hinge support. The fixed hinge support and the movable hinge support are symmetrically arranged along the longitudinal middle section of the concrete beam. The fixed hinge support abuts against the concrete beam, and the movable hinge support is movably connected to the concrete beam so that the concrete beam can move in the longitudinal direction.

7. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, S9 M u1 Calculated based on the basic combination value of the most unfavorable load borne by the concrete beam.

8. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, Before step S13, the crack width at the location of the reinforcing bar is measured using a crack observation instrument and recorded as follows: W 0, if W 0> W s , W s If the crack width value of the concrete beam is calculated according to the relevant industry standard under the combined action of the current electro-hydraulic servo actuator pressure and the test equipment, then proceed to S13; like W 0≤ W s Then, within 1 second, the pressure of the electro-hydraulic servo actuator will be increased to... F max3 , F max3 ={ W s / W 0· M u1 +( G f + G m + pS ) l z / 8·(2- l q / l z )+ bhγl z 2 / 8·[1-4( l x + l b ) 2 / l z 2 ]} / ( l b / 2), then turn to S13.

9. The automatic control and testing method of the concrete structure waterproofing layer test system according to claim 1, characterized in that, After step S13, the pressure of the electro-hydraulic servo actuator decreases from the current value to... F min Then increase to F max1 The loop continues until the number of iterations reaches the required design value, at which point the loop stops and then proceeds to S14.

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