Defect detection, evaluation and maintenance method for top and bottom plates of hollow slab beam

Abstract

The invention relates to a hollow slab beam top and bottom plate defect detection, evaluation and maintenance method, which comprises the following steps of: drilling at least three detection holes in a hollow slab beam bottom plate, cleaning sundries in an inner cavity of a hollow slab beam, measuring and obtaining the thickness of a top plate and the bottom plate, and observing the state of a steel strand; according to the result, the bearing capacity is calculated according to the current specification, and replacement or maintenance is determined according to the result; spraying the top plate with insufficient thickness, injecting a repairing material into the bottom plate, and filling the detection hole; and finally, after maintenance is completed, carrying capacity testing is carried out, and maintenance is completed when the standard is reached. By comprehensively mastering the condition of the hollow slab girder, acquiring data to calculate the bearing capacity of the hollow slab girder and performing detection again after targeted maintenance, potential safety hazards are effectively eliminated, the performance and durability of the hollow slab girder are improved, the service life of a bridge is prolonged, the maintenance cost is reduced, safe and stable operation of the bridge is guaranteed, and great significance is achieved for quality maintenance and safety guarantee of bridge engineering.

Description

Technical Field

[0001] The present invention belongs to the technical field of bridge maintenance. Specifically, it relates to a method for detecting, evaluating, and repairing defects in the top and bottom plates of hollow slab beams. Background Art

[0002] As a precast component widely used in bridge engineering, the hollow slab beam has the advantages of light self-weight, convenient construction, and high economy. However, in actual projects, the hollow slab beam often has problems such as insufficient thickness of the top and bottom plates due to design defects and construction deviations, seriously affecting the structural safety and durability.

[0003] In the prior art, the relatively thin top plate of the hollow slab beam will not only reduce the overall bearing capacity of the beam body, resulting in uneven stress distribution, but also generate excessive deformation under the action of vehicle loads due to the weakening of local stiffness, leading to damage to the bridge deck pavement and cracking of the top plate. These cracks will further allow moisture and corrosive substances to penetrate into the interior of the beam body, threatening the structural safety of the beam body. The relatively thin bottom plate weakens the bond effect of the prestressing tendons, affecting the flexural bearing capacity of the slab beam and the reserve of the precompression stress of the bottom plate. Secondly, it reduces the thickness of the protective layer of the prestressing tendons, and even directly exposes the steel strands in the cavity of the hollow slab beam, affecting its durability, accelerating corrosion, and further threatening the durability and safety of the structure. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for detecting, evaluating, and repairing defects in the top and bottom plates of hollow slab beams. By detecting, evaluating, and performing corresponding repair and reinforcement on the top and bottom plates of the hollow slab beam, the bearing capacity and durability of the hollow slab beam are improved, and the safe operation of the bridge is ensured.

[0005] To achieve the above technical purpose, the technical solution of the present invention is as follows:

[0006] A method for detecting, evaluating, and repairing defects in the top and bottom plates of a hollow slab beam, comprising the following steps:

[0007] (1) Detection: Drill at least three detection holes on the bottom plate of the hollow slab beam, clean the debris in the cavity of the hollow slab beam, measure and obtain the thickness of the top and bottom plates, and observe the exposed and rusted state of the steel strands;

[0008] (2) Evaluation: According to the exposed and rusted situation of the steel strands, the thickness of the bottom plate, and the thickness of the top plate, calculate the bearing capacity of the hollow slab beam in accordance with the current national and industrial codes. If the bearing capacity does not meet the codes, or still cannot meet the requirements of the current national and industrial codes after repair, replace it with a qualified slab beam of the same type; if the bearing capacity meets the codes, or meets the requirements of the current national and industrial codes after repair, perform repair on it;

[0009] (3) Maintenance: Clean the cavity. If the top plate does not meet the minimum thickness requirement, spray repair material on the top plate until the thickness requirement is met; if the bottom plate does not meet the minimum thickness requirement, inject repair material into the bottom plate until the thickness requirement is met, and fill the inspection holes.

[0010] (4) Testing: After the repair is completed, conduct a bearing capacity test on the hollow slab beam. After the test results meet the requirements of current national and industrial codes, the maintenance is completed.

[0011] Through the systematic inspection, evaluation, maintenance, and testing processes, comprehensively understand the actual condition of the hollow slab beam. Accurately obtain the thickness of the top and bottom plates and the status of the steel strands during the inspection, and evaluate and judge the bearing capacity of the hollow slab beam. Based on the results, reasonably select replacement or maintenance measures, conduct targeted maintenance, and re-inspect after maintenance to ensure the treatment effect. The entire process effectively eliminates potential safety hazards, improves the bearing capacity and durability of the hollow slab beam, extends the service life of the bridge, reduces the bridge maintenance cost, and ensures the safe and stable operation of the bridge.

[0012] In a specific implementable solution, in step (1), if there are three inspection holes, one of the inspection holes is located in the middle of the bottom plate, and the other two inspection holes are respectively located below the anchorage sections at both ends of the steel strands in the bottom plate; since the anchorage section of the steel strand is the key part where it connects with the hollow slab beam and transfers prestress, the status of the anchorage section directly affects the bearing capacity and structural stability of the hollow slab beam, so it is necessary to detect the anchorage section of the steel strand.

[0013] Furthermore, in step (1), if there are multiple sections of foam core molds inside the hollow slab beam, drill inspection holes on the bottom plate below each section of the foam core mold; since in precast hollow slab beams, the attitude of each section of the foam core mold in the hollow slab beam is different, the position of the foam core mold may be too high, which will cause the bottom plate to be too thick and the top plate to be too thin; the position of the foam core mold may be too low, which will cause the bottom plate to be too thin and the top plate to be too thick. Therefore, it is necessary to open inspection holes on the bottom plate below each section of the foam core mold. By detecting the bottom plate below each section of the foam core mold, the thickness of the bottom and top plates of the hollow slab beam at different positions can be comprehensively understood, avoiding the influence on the evaluation of the structural bearing capacity due to the failure to detect local thickness anomalies, and helping to formulate more accurate maintenance or reinforcement plans.

[0014] In a specific implementable solution, in step (1), use high-pressure water flow to clean the inner cavity of the hollow slab beam. If there is a foam core mold in the inner cavity of the hollow slab beam, the foam core mold can be broken by high-pressure water flow, which can facilitate the cleaning of the inner cavity and improve the convenience of detecting the hollow slab beam.

[0015] In a specific feasible implementation, in step (2), within the effective prestress range of the steel strand, if there is a broken wire in the steel strand, then this steel strand does not contribute to the bearing capacity; if there is rusting, peeling, or flaking of the steel strand, then this steel strand does not contribute to the bearing capacity;

[0016] Within the anchorage length range starting from the end anchorage point of the steel strand and towards the mid-span direction, if the steel strand at the bottom slab is exposed or the thickness of the bottom slab is less than 9 cm, then this steel strand does not contribute to the bearing capacity.

[0017] Due to the existence of broken wires, rusting, peeling, or flaking in the steel strand, or the exposure of the steel strand in the anchorage section, or the insufficient thickness of the bottom slab to fully wrap the steel strand, the bearing capacity of the steel strand will be severely weakened. Therefore, excluding such steel strands from the bearing capacity contribution can avoid overestimating the actual bearing capacity of the hollow slab beam, ensure that the evaluation result is more in line with the actual stress condition of the structure, and provide a scientific basis for subsequent decision-making.

[0018] In a specific feasible implementation, in step (3), after filling the top slab and / or the bottom slab, fill the inner cavity of the hollow slab beam with filling material; if the overall filling of the inner cavity of the hollow slab beam is too heavy, then locally fill the inner cavity of the hollow slab beam at the repair area of the top slab and / or the bottom slab.

[0019] After spraying repair material on the top slab of the hollow slab beam, due to the continuous action of vehicle dynamic loads during the actual service process of the bridge, the repair material on the top slab is in a vibrating environment for a long time and is subjected to repeated fatigue loads. In this way, the bonding interface between the repair material and the top slab matrix is prone to fatigue damage, resulting in the risk of the repair material falling off. Therefore, filling the inner cavity of the hollow slab beam with filling material to support the repair material at the top slab can effectively reduce the possibility of the repair material falling off, ensure the stable structural performance of the repaired hollow slab beam, and meet the long-term use requirements.

[0020] In addition, for some bridges, after filling the entire inner cavity, the hollow slab beam becomes too heavy. Therefore, the repair area of the hollow slab beam can be filled, which can not only repair the hollow slab beam but also avoid adding excessive materials that may increase additional loads and change the original force system of the hollow slab beam.

[0021] Furthermore, the filling material is the repair material. To simplify the convenience of repairing the hollow slab beam, the same material as the repair material is used to fill the inner cavity of the hollow slab beam.

[0022] Further, the filling material includes foamed lightweight soil, polyurea or polyurethane. By filling the inner cavity of the hollow slab beam with lightweight filling material, it can not only support the repair material of the top plate, but also reduce the over-limit load generated by the filling material on the hollow slab beam, achieving the pouring effect of vertical stratification, thus avoiding affecting the overall stability of the bridge structure. This enables the beam body to stably exert its bearing capacity during long-term use, effectively avoiding problems such as insufficient bearing capacity of the slab beam, bearings, and the lower structure of the bridge caused by over-limit load, and ensuring the safety and reliability of the bridge structure.

[0023] Further, the repair material for the top plate includes cement-based grouting material or fine aggregate concrete, and the repair material for the bottom plate is cement-based grouting material. Spraying the cement-based grouting material or fine aggregate concrete on the top plate and filling the bottom plate with the cement-based grouting material can effectively repair the top plate and the bottom plate.

[0024] Advantages of the present invention: By detecting, evaluating, repairing, and testing the hollow slab beam, the thickness of the top plate and bottom plate of the hollow slab beam and the state of the steel strands can be accurately obtained. Based on this, the bearing capacity is evaluated, replacement or repair measures are reasonably selected, and repairs are carried out specifically and tested again to ensure the treatment effect. At the same time, when repairing the hollow slab beam, according to the disease conditions of different hollow slab beams, the top plate and bottom plate are repaired specifically. According to different situations of the hollow slab beam, the inner cavity is filled integrally or partially, and the same or different materials are filled. This can not only effectively eliminate potential safety hazards, improve the performance and durability of the hollow slab beam, extend the service life of the bridge, reduce the maintenance cost, but also ensure the safe and stable operation of the bridge structure. Description of the Drawings

[0025] Figure 1 It is a structural schematic diagram of repairing the top plate of the hollow slab beam.

[0026] Figure 2 It is a structural schematic diagram of repairing the bottom plate of the hollow slab beam.

[0027] Figure 3 It is a structural schematic diagram of filling the entire cross-section of the inner cavity of the hollow slab beam.

[0028] Figure 4 It is a structural schematic diagram of repairing the top plate and bottom plate of the hollow slab beam and filling the inner cavity with lightweight material.

[0029] Figure 5 It is a structural schematic diagram of repairing the top plate of the hollow slab beam and filling the entire cross-section of the local inner cavity.

[0030] Figure 6 It is a structural schematic diagram of repairing the top plate of the hollow slab beam and filling the entire cross-section of the local inner cavity with lightweight material.

[0031] Figure 7It is a structural schematic diagram for repairing the bottom plate of a hollow slab beam and filling the entire cross-section of the inner cavity locally.

[0032] Figure 8 It is a structural schematic diagram for repairing the bottom plate of a hollow slab beam and filling the entire cross-section of the inner cavity locally with lightweight materials.

[0033] Figure 9 It is a structural schematic diagram for repairing the top and bottom plates of a hollow slab beam and filling the entire cross-section at the repair position.

[0034] Figure 10 It is a structural schematic diagram for repairing the top and bottom plates of a hollow slab beam and filling the entire cross-section at the repair position with lightweight materials.

[0035] Figure 11 It is a structural schematic diagram for another case of repairing the top and bottom plates of a hollow slab beam and filling the entire cross-section at the repair position with lightweight materials. Specific implementation mode

[0036] The following further elaborates on the present invention in conjunction with the attached Figures 1-11 Make a further detailed description of the present invention.

[0037] Refer to Figure 1 , a method for detecting, evaluating and repairing defects of the top and bottom plates of a hollow slab beam, comprising the following steps:

[0038] (1) Detection: Drill at least three detection holes on the bottom plate of the hollow slab beam. In this embodiment, there are three detection holes, one of which is located in the middle part of the bottom plate, and the other two detection holes are respectively located below the anchorage sections at both ends of the steel strands in the bottom plate. In other embodiments, the detection holes can be multiple and evenly distributed on the bottom plate, or if the foam core mold has multiple segments, then detection holes are drilled on the bottom plate below each segment of the foam core mold according to the number of segments.

[0039] Insert a high-pressure water device into the detection holes to spray high-pressure water flow to clean the sundries, dust, etc. in the inner cavity of the hollow slab beam. If there is a foam core mold in the inner cavity, use the high-pressure water flow to impact the foam core mold, break it, and discharge it from the detection holes to clean out the corresponding observation inner cavity; Use equipment such as a ruler and a radar to detect the thickness of the bottom plate and the inner cavity of the hollow slab beam, and then calculate the thickness of the top plate using the overall height of the hollow slab beam, and use an endoscope to observe the exposed and rusted state of the steel strands;

[0040] (2) Evaluation: Within the effective prestress range of the steel strands, (a) if there is a broken wire situation in the steel strands, then the steel strands do not contribute to the bearing capacity; (b) if there is a situation of rusting, peeling and flaking in the steel strands, then the steel strands do not contribute to the bearing capacity; (c) within the anchorage length range from the end anchorage point of the steel strands towards the mid-span direction, if the steel strands in the bottom plate are exposed or the thickness of the bottom plate is less than 9 cm, then the steel strands do not contribute to the bearing capacity.

[0041] The steel strand is judged through the above three cases, and the bearing capacity of the hollow slab beam is calculated according to the thickness of the bottom slab and the top slab in accordance with the current national and industry codes, including but not limited to: "General Code for Design of Highway Bridges and Culverts" (JTGD60); "Code for Design of Highway Reinforced Concrete and Prestressed Concrete Bridges and Culverts" (JTG3362); "Technical Standard for Highway Engineering" (JTG B01); "Code for Design of Highway Bridge and Culvert Foundations" (JTG3363);

[0042] If the bearing capacity does not meet the code requirements, or still cannot meet the requirements of the current national and industry codes after repair, it shall be replaced; if the bearing capacity meets the code requirements, but the thickness of the bottom slab or the top slab is insufficient, the insufficient thickness part of the hollow slab beam still needs to be repaired, or if it meets the requirements of the current national and industry codes after repair, it shall be repaired;

[0043] (3) Repair: First, clean the cavity, refer to Figure 1 , if the top slab does not meet the minimum thickness requirement, spray cement-based grouting material, fine aggregate concrete or other repair materials on the top slab until the thickness requirement is met; refer to Figure 2 , if the bottom slab does not meet the minimum thickness requirement, inject cement-based grouting material into the bottom slab until the thickness requirement is met, and finally fill the inspection hole;

[0044] To further improve the repair effect, in other embodiments, refer to Figure 3 , spray cement-based grouting material, fine aggregate concrete or other repair materials on the area where the top slab thickness is insufficient, and inject cement-based grouting material into the area where the bottom slab thickness is insufficient. After the top slab and the bottom slab are repaired, fill the inner cavity of the hollow slab beam to support the repaired area of the top slab and improve the local stiffness of the top slab; the filling material for filling the inner cavity is selected from the same repair material as the top slab or the bottom slab, which can simplify the construction; in other embodiments, if the weight affects the force of the bridge structure after filling the inner cavity of the hollow slab beam with the same filling material as the repair material, refer to Figure 4 , the filling material for filling the inner cavity of the hollow slab beam can be selected from lightweight materials such as foamed lightweight soil, polyurea or polyurethane.

[0045] To improve the repair effect and avoid increasing the additional load of the hollow slab beam, in other embodiments, refer to Figure 5 , spray cement-based grouting material, fine aggregate concrete or other repair materials on the area where the top slab thickness is insufficient, and then locally fill and fill the inner cavity of the hollow slab beam at the position where the top slab is repaired. To improve the construction convenience, the filling material for filling the inner cavity is the same material as the repair material; in other embodiments, refer to Figure 6, if the increase in the weight of the local filling material affects the force-bearing of the bridge structure, the filling material for filling the inner cavity of the hollow slab beam is selected from lightweight materials such as foam lightweight soil, polyurea or polyurethane.

[0046] In other embodiments, refer to Figure 7 , first inject a repair material, that is, a cement-based grouting material, into the area where the bottom plate thickness is insufficient until the thickness requirement is met, and then locally fill and fill the inner cavity of the hollow slab beam at the position where the bottom plate is repaired. To improve the construction convenience, the filling material for filling the inner cavity is the same material as the repair material; In other embodiments, refer to Figure 8 , if the increase in the weight of the local filling material affects the force-bearing of the bridge structure, the filling material for filling the inner cavity of the hollow slab beam is selected from lightweight materials such as foam lightweight soil, polyurea or polyurethane.

[0047] In other embodiments, refer to Figure 9 , if the repaired top plate and bottom plate are in adjacent or intersecting areas, spray a repair material on the area where the top plate thickness is insufficient. The repair material is a cement-based grouting material, fine aggregate concrete or other repair materials, and inject a repair material into the bottom plate. The repair material is a cement-based grouting material. After the top plate and bottom plate are repaired, use a filling material to locally fill and fill the inner cavity of the hollow slab beam at the positions of the repaired top plate and bottom plate. In this embodiment, the filling material can be selected from the repair material of the top plate or the repair material of the bottom plate; Refer to Figures 10-11 , in other embodiments, to reduce the weight of the filling material, the filled filling material includes but is not limited to foam lightweight soil, polyurea or polyurethane with lighter mass.

[0048] (4) Testing: After the in-cavity repair is completed, a static loading test is used to conduct load-bearing capacity tests such as flexural and shear resistance. After the test results meet the requirements of current national and industrial codes, the repair is completed.

[0049] The above are all preferred embodiments of the present invention, and the protection scope of the present invention is not limited accordingly. Therefore, all equivalent changes made according to the structure, shape and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A method for detecting, evaluating and repairing defects in the top and bottom plates of a hollow slab beam, characterized in that: It includes the following steps: (1) Detection: Drill at least three detection holes on the bottom plate of the hollow slab beam, clean the debris in the inner cavity of the hollow slab beam, measure and obtain the thickness of the top plate and the bottom plate, and observe the exposed and rusted state of the steel strands; (2) Evaluation: According to the exposed and rusted condition of the steel strands, the thickness of the bottom plate, and the thickness of the top plate, calculate the bearing capacity of the hollow slab beam in accordance with the current national and industrial codes. If the bearing capacity does not meet the codes, or still cannot meet the requirements of the current national and industrial codes after repair, then replace it; if the bearing capacity meets the codes, or meets the requirements of the current national and industrial codes after repair, then repair it; (3) Repair: If the top plate does not meet the minimum thickness requirement, spray repair material on the top plate until the thickness requirement is met; if the bottom plate does not meet the minimum thickness requirement, inject repair material into the bottom plate until the thickness requirement is met, and fill the detection holes; (4) Testing: After the repair is completed, conduct a bearing capacity test on the hollow slab beam. After the test results meet the requirements of the current national and industrial codes, the repair is completed.

2. The method for detecting, evaluating and repairing the defects of the top and bottom plates of the hollow slab beam according to claim 1, wherein: In step (1), if there are three detection holes, one of the detection holes is located in the middle part of the bottom plate, and the other two detection holes are respectively located below the anchorage sections at both ends of the steel strands in the bottom plate.

3. The method for detecting, evaluating and repairing the top and bottom plate defects of the hollow slab beam according to claim 1, wherein: In step (1), if there are multiple sections of the foam core mold inside the hollow slab beam, drill detection holes on the bottom plate below each section of the foam core mold for detection.

4. The method for detecting, evaluating and repairing the defects of the top and bottom plates of the hollow slab beam according to claim 1, characterized in that: In step (1), use high-pressure water flow to clean the inner cavity of the hollow slab beam.

5. The method for detecting, evaluating and repairing the top and bottom plate defects of the hollow slab beam according to claim 1, characterized in that: In step (2), within the effective prestress range of the steel strands, if there are broken wires in the steel strands, then these steel strands do not contribute to the bearing capacity; if there are rusted, peeled, and flaked conditions in the steel strands, then these steel strands do not contribute to the bearing capacity; Within the anchorage length range from the end anchorage point of the steel strands towards the mid-span direction, if the steel strands in the bottom plate are exposed, or the thickness of the bottom plate is less than 9 cm, then these steel strands do not contribute to the bearing capacity.

6. The method for detecting, evaluating and repairing the top and bottom plate defects of the hollow slab beam according to claim 1, characterized in that: In step (3), after filling the top plate and / or the bottom plate, fill the inner cavity of the hollow slab beam with filling material; if the overall filling of the inner cavity of the hollow slab beam is too heavy, then locally fill the inner cavity of the hollow slab beam at the repair area of the top plate and / or the bottom plate with filling material.

7. The method for detecting, evaluating and repairing the top and bottom plate defects of the hollow slab beam according to claim 6, characterized in that: The filling material is repair material.

8. The method for detecting, evaluating and repairing the defects of the top and bottom plates of the hollow slab beam according to claim 6, characterized in that: The filling material includes foamed light soil, polyurea, or polyurethane.

9. The method for detecting, evaluating and repairing the defects of the top and bottom plates of the hollow slab beam according to claim 1, wherein: The repair material for the top plate includes cement-based grouting material or fine aggregate concrete, and the repair material for the bottom plate is cement-based grouting material.

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