A graded treatment and reinforcement method for cracks in concrete bridges

Abstract

This invention relates to the field of building construction, specifically to a method for graded treatment and reinforcement of cracks in concrete bridges, comprising the following steps: Step 1, establishing and acquiring health record data for the bridge; Step 2, conducting a visual inspection of the bridge's exterior using manual inspection and common measurement tools, focusing on the superstructure, substructure, and bridge deck system according to potential hazard areas and re-inspection areas, identifying newly added related cracks and new cracks; Step 3, retrieving maintenance records from the health record data based on related cracks, analyzing the impact of disaster causes on historical reinforcement in the maintenance records, and adjusting the reinforcement methods; further, classifying new cracks into minor, moderate, and severe cracks based on their width to obtain corresponding reinforcement methods; Step 4, identifying and cleaning loose areas within the crack region using an ultrasonic measurement device; This invention is used to achieve classified treatment of cracks in different locations of bridges, ensuring the reinforcement effect of bridge cracks in different locations.

Description

Technical Field

[0001] This invention relates to the field of building construction, specifically to a method for graded treatment and reinforcement of cracks in concrete bridges. Background Technology

[0002] The construction of transportation infrastructure plays an important role in boosting the national economy. In recent years, with the rapid development of the national economy, my country's transportation industry has made great progress in infrastructure construction. As of 2020, the total length of highways in China reached 5.1981 million kilometers, and there were 912,800 highway bridges with a total length of 66.2855 million meters. Among them, there were 6,444 extra-large bridges with a length of 11.6297 million meters, and 119,935 large bridges with a length of 32.7777 million meters. China has begun to transform from a major transportation country to a strong transportation country.

[0003] Although my country has achieved remarkable success in bridge construction, the increasing service life of bridges and the continued booming development of transportation have made bridge maintenance and management increasingly challenging. Due to vehicle loads, temperature differences, chemical corrosion, and other environmental factors, bridge structures are highly susceptible to defects such as pitting, exposed reinforcement, and cracks during use, affecting their lifespan. This is especially true for provincial and county / township road bridges, where aging is already quite common.

[0004] Therefore, existing technologies employ regular inspections and intelligent monitoring systems for detection. However, for bridges in mountainous or other remote areas, the applicability of intelligent monitoring systems is limited due to considerations of construction convenience and economic cost. During regular inspections, manual visual inspection is typically the primary method, supplemented by tools such as crack observation instruments, steel rulers, steel tape measures, telescopes, cameras, calipers, magnifying glasses, and depth detection software. This allows for the examination of common defects in the bridge structure and the determination of the location and size of the damage, enabling the use of surface sealing methods and steel plate bonding methods to reinforce bridge cracks in different locations.

[0005] In the process of reinforcing bridges using different methods, the interface treatment of bridge cracks is particularly important. The treatment methods differ depending on the location of the crack. If the interface dust is not thoroughly cleaned or the interface agent (such as epoxy resin mortar, rebar adhesive, etc.) is applied unevenly, it can easily lead to the separation of concrete from the reinforcement material, failing to achieve the desired reinforcement effect and causing frequent subsequent repairs. Therefore, this invention provides a graded treatment and reinforcement method for concrete bridge cracks to achieve classified treatment of cracks in different locations of the bridge and ensure the reinforcement effect of bridge cracks in different locations. Summary of the Invention

[0006] To address the aforementioned problems, this invention provides a method for graded treatment and reinforcement of cracks in concrete bridges, which enables the classification and treatment of cracks at different locations on the bridge, ensuring the reinforcement effect of bridge cracks at different locations.

[0007] To achieve the above objectives, the technical solution of the present invention is as follows: A method for graded treatment and reinforcement of cracks in concrete bridges, comprising the following steps:

[0008] Step 1: Establish and acquire health records for the bridge. Health records include the bridge's geometric parameters, material parameters, environmental parameters, maintenance records, historical bridge quality inspection reports, and existing defects in historical bridges. Based on the health records, assess potential hazard areas and determine re-inspection areas based on existing defects in historical bridges.

[0009] Step 2: Conduct a visual inspection of the bridge using manual inspection and common measurement tools. Focus on inspecting the superstructure, substructure, and deck system of the bridge according to the areas of potential hazards and areas requiring re-inspection to determine whether any new related cracks have been added to the areas of potential hazards and areas requiring re-inspection. At the same time, obtain information on any new cracks in other locations of the bridge using manual inspection and common measurement tools and record them in the health record data.

[0010] Step 3: Based on the associated cracks, retrieve the maintenance records from the health records, analyze the impact of the disaster cause on the historical reinforcement in the maintenance records, and adjust the reinforcement method; then, based on the width of the newly added cracks, classify them into minor cracks, medium cracks, and severe cracks, and obtain the corresponding reinforcement methods based on minor cracks, medium cracks, and severe cracks.

[0011] Step 4: When reinforcing bridge cracks based on reinforcement methods, the loose areas in the crack area are identified by an ultrasonic measurement device, and the loose areas are cleaned to ensure the accuracy of the bonding of the concrete interface.

[0012] Furthermore, in steps two to four, the method for manually recording associated cracks and newly added cracks is as follows: for areas with potential hazards, they are recorded as naturally growing cracks; for newly added associated cracks in the re-inspection areas, they are recorded as incompletely reinforced cracks.

[0013] Based on the natural growth cracks, retrieve the corresponding influencing conditions; based on the influencing conditions, retrieve the health records to see if there are maintenance records with similar influencing conditions; based on the maintenance records, check the reinforcement status of the corresponding re-inspection areas; if new cracks are found in the reinforcement status, analyze the causes of the disaster based on the new cracks, and adjust the reinforcement method based on the causes of the disaster; if no new cracks are found in the reinforcement status, perform crack reinforcement based on the reinforcement method corresponding to the maintenance records.

[0014] Based on the incomplete reinforcement of cracks, an ultrasonic measurement device is used to determine whether the loose area in the re-inspection area is consistent with the historical cracks in the historical bridge. If they are consistent, the impact of construction factors is recorded in the health record data; if they are inconsistent, the cause of the disaster is analyzed, and the reinforcement method is adjusted based on the cause of the disaster.

[0015] Furthermore, in steps two through four, the method for obtaining historical cracks in the defects of historical bridges will not only include the bridge's own health record data, but also health record data with consistent geometric and material parameters as a reference.

[0016] Furthermore, in step three, minor cracks are defined as having a width of <0.15mm and a length of <2m; moderate cracks are defined as having a width of 0.15mm-0.3mm and a length of 2m-5m; and severe cracks are defined as having a width of >0.3mm and a length of >5m.

[0017] Furthermore, in step four, an ultrasonic measuring device is used to determine the loose area in the crack area, and the consistency of sound between the surrounding bridge concrete layer and the loose area is used to confirm the completion of the cleaning of the interface around the crack.

[0018] Furthermore, in step one, the potential hazard area is determined based on the structural weaknesses of the bridge, the causes of environmental disasters, and the rate of expansion of existing defects in the bridge.

[0019] Furthermore, in step three, the reinforcement methods include surface sealing, pressure grouting, and structural anchoring.

[0020] Furthermore, in step four, the health record data also includes a crack distribution model drawing of each surface of the bridge, and crack markers of different colors are drawn on the corresponding crack distribution model drawing according to associated cracks and newly added cracks.

[0021] Furthermore, in step four, the loosened areas will be marked proportionally based on the crack distribution model drawings, and additional reinforcement treatment will be carried out based on the interaction areas of different loosened areas.

[0022] Furthermore, in step four, a digital model is used to create a crack distribution model drawing. Crack markers and loose areas are recorded in the digital model using digital representation, and reinforcement methods are recorded in the digital model using different markers.

[0023] The above approach has the following beneficial effects:

[0024] 1. This solution integrates geometric parameters, material parameters, environmental parameters, maintenance records, historical bridge quality inspection reports, and key information on existing defects in historical bridges to pre-identify potential hazard areas and areas requiring re-inspection. This reduces the need for comprehensive inspections as in traditional methods, thus decreasing workload. Precise investigations are conducted in key areas to ensure the absence of newly associated cracks in historical defects, improving the efficiency and accuracy of inspections. Furthermore, newly added cracks are recorded in the bridge's health record data, forming a database for that bridge. This not only reduces the workload of subsequent repetitive inspections but also provides comprehensive data support for future defect trend analysis, significantly improving the efficiency and accuracy of inspections.

[0025] 2. This plan also retrieves historical maintenance records for associated cracks, analyzes the impact of newly added associated cracks on the original reinforcement, and adjusts the plan accordingly. This avoids using ineffective or unsuitable measures and improves the effectiveness of reinforcement methods. Furthermore, it clearly classifies cracks into three levels—minor, moderate, and severe—based on crack width, matching corresponding reinforcement methods to different levels of cracks. This avoids the waste of resources caused by over-reinforcing minor cracks and prevents safety hazards caused by insufficient treatment of severe cracks. The reinforcement plan is more in line with the actual situation of the cracks, significantly improving the treatment effect and reducing the secondary risk of crack recurrence or expansion.

[0026] 3. In traditional reinforcement processes, incomplete cleaning of loose concrete around cracks can lead to weak bonding between the old and new concrete, affecting the durability of the reinforcement. This solution addresses this by using ultrasonic testing to precisely identify and thoroughly clean loose areas, effectively ensuring the cleanliness and firmness of the concrete interface. This allows subsequent reinforcement materials (such as epoxy resin mortar, steel plates, and anchoring adhesive) to bond tightly to the original concrete structure, improving the load-bearing capacity and anti-aging properties of the reinforced area and extending the bridge's service life.

[0027] Additional aspects and advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. Attached Figure Description

[0028] Figure 1 This is a schematic diagram showing the number of bridges surveyed in an embodiment of the method for graded treatment and reinforcement of cracks in concrete bridges of the present invention.

[0029] Figure 2 This is a schematic diagram of the bridge deck of the Kaixia River Bridge in an embodiment of the method for graded treatment and reinforcement of cracks in concrete bridges of the present invention.

[0030] Figure 3 This is a schematic diagram of the bridge deck of Xiangshuitan Bridge in an embodiment of the method for graded treatment and reinforcement of cracks in concrete bridges of the present invention.

[0031] Figure 4This is a schematic diagram of the bridge deck of Jiaoxi Bridge in an embodiment of the method for graded treatment and reinforcement of cracks in concrete bridges according to the present invention.

[0032] Figure 5 This is a schematic diagram of epoxy resin sealing of cracks in an embodiment of the graded treatment and reinforcement method for cracks in concrete bridges of the present invention;

[0033] Figure 6 This is a schematic diagram of the steel plate used for bonding in an embodiment of the graded treatment and reinforcement method for cracks in concrete bridges of the present invention;

[0034] Figure 7 This is a flowchart illustrating an embodiment of the method for graded treatment and reinforcement of cracks in concrete bridges according to the present invention. Detailed Implementation

[0035] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0036] The following detailed description illustrates the specific implementation method:

[0037] Example 1:

[0038] As attached Figure 7 The following is a method for graded treatment and reinforcement of cracks in concrete bridges, comprising the following steps:

[0039] Step 1: Establish and acquire bridge health records. These records include the bridge's geometric parameters, material parameters, environmental parameters, maintenance records, historical bridge quality inspection reports, and existing defects. Based on these health records, assess potential hazard areas and determine re-inspection areas based on existing defects. Hazardous areas are determined based on the bridge's structural weaknesses, the causes of environmental disasters, and the rate of expansion of existing defects.

[0040] For example, if there are existing cracks or weak areas in the structure, and if the existing cracks are not effectively controlled, they will extend along the direction of stress concentration, and branch cracks will be generated on or around the extension path. For example, the existing vertical cracks in the main arch ring of the Kaixia River Bridge may extend along the direction of the arch axis under the action of load and environment, and generate small oblique branch cracks at the end of the cracks. At the same time, bridge structures are mostly symmetrically designed. If the existing cracks appear on one side of the component (such as the left main beam), the new cracks may appear in the symmetrical position (the right main beam), especially when the cause is a common factor such as overall load and temperature change.

[0041] If the causes of environmental disasters are not completely eliminated, they will continue to induce new cracks. For example, due to the large temperature difference between day and night, the original structure of bridges in mountainous areas has already developed surface temperature cracks (existing cracks). If these cracks are not sealed in time, the repeated action of temperature stress will cause new temperature cracks (new cracks) to appear around the existing cracks or on similar components (such as adjacent main beams or symmetrical piers). Another example is that if the problem of vehicle overloading is not resolved, existing cracks (such as transverse stress cracks at the bottom of hollow slabs) will continue to expand, while new stress cracks will be generated at weak points in the load transfer path (such as near the mid-span or above the supports).

[0042] After the original cracks are fixed, if they are not effectively treated (e.g., only surface sealing without addressing the root cause) and continue to expand (e.g., width increases by 0.03 mm per month), the expansion rate of new cracks will also be faster. This is because both face the same load and environmental effects, and the original cracks have damaged the overall structural integrity, leading to a decrease in the load-bearing capacity of the area where the new cracks are located, making it more susceptible to external forces and expansion. Secondly, if the original cracks have been reinforced through pressure grouting, steel plate bonding, etc., the cause has been controlled, the structural stress state has improved, the overall stress level has been reduced, and the rapid development of new cracks has been inhibited. However, for a period of time, the new cracks may mostly be minor cracks (width < 0.4 mm) with a slow expansion rate (< 0.01 mm / month), or even remain static. On the other hand, if the original cracks are severe through cracks (e.g., width ≥ 0.6 mm) and are not reinforced in time, it will lead to a decrease in the local stiffness of the structure and an exacerbation of stress concentration. In this case, the new cracks will not only appear frequently but also expand at a significantly faster rate, and may even develop into severe cracks in a short period of time. Therefore, it is necessary to divide the potential hazard areas and carry out timely investigation and treatment.

[0043] Step 2: Conduct a visual inspection of the bridge using manual inspection and common measurement tools. Focus on inspecting the superstructure, substructure, and deck system of the bridge according to the areas with potential hazards and areas requiring re-inspection to determine whether any new related cracks have been added to the areas with potential hazards and areas requiring re-inspection. At the same time, obtain information on any new cracks in other locations of the bridge using manual inspection and common measurement tools and record them in the health record data.

[0044] For example, by integrating geometric parameters, material parameters, environmental parameters, maintenance records, historical bridge quality inspection reports, and key information on existing defects in historical bridges, potential hazard areas and areas requiring re-inspection can be identified in advance, reducing the need for comprehensive inspections in traditional testing and thus decreasing workload. Precise investigations can be conducted in key areas to ensure the absence of newly associated cracks in historical defects, improving the efficiency and accuracy of inspection work. Furthermore, newly added cracks in the bridge are recorded in the bridge's health record data, forming a database for that bridge. This not only reduces the workload of subsequent repeated inspections but also provides complete data support for subsequent defect trend analysis, significantly improving the efficiency and accuracy of inspection work.

[0045] Step 3: Based on the associated cracks, retrieve the maintenance records from the health records, analyze the impact of the disaster causes on the historical reinforcement in the maintenance records, and adjust the reinforcement methods; then, based on the width of the newly added cracks, classify them into minor cracks, medium cracks, and severe cracks, and obtain the corresponding reinforcement methods based on minor cracks, medium cracks, and severe cracks.

[0046] Simultaneously, historical maintenance records were retrieved for associated cracks. Based on newly added associated cracks, the impact of disaster causes on the original reinforcement was analyzed, and the plan was adjusted to avoid using ineffective or unsuitable measures, thus improving the effectiveness of reinforcement methods. Furthermore, cracks were clearly classified into three levels—minor, moderate, and severe—based on crack width, and corresponding reinforcement methods were matched for each level. This avoided the waste of resources caused by over-reinforcing minor cracks and prevented safety hazards caused by insufficient treatment of severe cracks. The reinforcement plan was made more suitable for the actual situation of the cracks, significantly improving the treatment effect and reducing the secondary risk of crack recurrence or expansion. Moreover, the health record data is not only the basis for detection and reinforcement but also the core database for subsequent maintenance. By continuously recording crack development, reinforcement measures, and effectiveness, the evolution trajectory of bridge defects can be clearly traced, providing data support for the formulation of subsequent maintenance plans. This allows for proactive prediction of bridge defects, thereby extending the bridge's service life.

[0047] Step 4: When reinforcing bridge cracks using reinforcement methods, a loose zone within the crack area is identified using an ultrasonic measuring device. This loose zone is then cleaned to ensure accurate bonding of the concrete interface. The cleanliness of the surrounding bridge concrete layer is confirmed by verifying the consistency of sound between the loose zone and the surrounding concrete layer.

[0048] For example, in intact concrete, the aggregates and cement paste are tightly bonded, with low porosity and uniform distribution. Ultrasonic waves propagate smoothly through the concrete with almost no additional obstruction and minimal energy loss. However, in loose areas, due to crack propagation, external impact, or material aging, the internal structure is damaged, resulting in interconnected micro-cracks, separation of aggregates from cement paste, and localized loosening or even voids in the concrete. The overall density decreases significantly, and when ultrasonic waves propagate in loose areas, the presence of numerous cavities makes the propagation path tortuous, leading to significant energy loss. Therefore, based on the reflection of the reflected waves, it is possible to accurately determine whether the loose area has been completely cleaned, facilitating accurate bonding of the subsequent concrete interface.

[0049] In steps two through four, the method for manually recording associated cracks and newly added cracks is as follows: for areas with potential hazards, they are recorded as naturally growing cracks; for newly added associated cracks in re-inspection areas, they are recorded as incompletely reinforced cracks.

[0050] Based on the natural growth cracks, retrieve the corresponding influencing conditions. Based on the influencing conditions, retrieve the health records to see if there are maintenance records with similar influencing conditions. Based on the maintenance records, check the reinforcement status of the corresponding re-inspection areas. If there are new cracks in the reinforcement status, analyze the causes of the disaster based on the new cracks and adjust the reinforcement method based on the causes of the disaster. If there are no new cracks in the reinforcement status, perform crack reinforcement based on the reinforcement method corresponding to the maintenance records.

[0051] Based on the incomplete reinforcement of cracks, an ultrasonic measurement device is used to determine whether the loose area in the re-inspection area is consistent with the historical cracks in the historical bridge. If they are consistent, the impact of construction factors is recorded in the health record data; if they are inconsistent, the cause of the disaster is analyzed, and the reinforcement method is adjusted based on the cause of the disaster.

[0052] For example, after a bridge is built, natural damage due to environmental factors or long-term operation may cause some naturally occurring cracks to appear after a period of time. By retrieving the reinforcement methods in the current health record data, the reinforcement effect of the historical reinforcement methods can be determined. This allows for the adoption of reinforcement methods with good results to reinforce the newly added cracks. This provides data support and reference based on the reinforcement impact and effect of the bridge's historical reinforcement methods, thereby improving the accuracy and stability of the subsequent reinforcement process.

[0053] In the re-inspection area, an ultrasonic detection device is used to obtain newly added related cracks. Based on the consistency between the related cracks and the original historical cracks, the location of the related cracks and historical cracks is used for verification to determine whether the interface separation is caused by the weak bonding of the original historical cracks. This allows for subsequent adjustments to the reinforcement method to improve the accuracy and stability of the concrete interface bonding.

[0054] In steps two through four, the acquisition of historical cracks in the existing defects of the bridge involves not only the bridge's own health record data but also using health record data with consistent geometric and material parameters as a reference. This approach expands the scope of comparison by using health record data with consistent geometric and material parameters, facilitating the selection of appropriate reinforcement methods based on historical data.

[0055] The above steps address the shortcomings of traditional reinforcement processes, where incomplete cleaning of loose concrete around cracks can lead to weak bonding between the old and new concrete, affecting the durability of the reinforcement. Ultrasonic testing precisely identifies and thoroughly cleans loose areas, effectively ensuring the cleanliness and solidity of the concrete interface. This allows subsequent reinforcement materials (such as epoxy resin mortar, steel plates, and anchoring adhesive) to bond tightly to the original concrete structure, improving the load-bearing capacity and anti-aging properties of the reinforced area and extending the bridge's service life.

[0056] Crack identification must follow the principles of comprehensive coverage, layered investigation, and instrument verification. First, the identification scope must be clearly defined to cover the superstructure (main beams, hollow slabs, arches, etc.), substructure (cap beams, piers, abutments, etc.), and bridge deck system (paving layer, guardrails, etc.) to ensure that no key load-bearing components are missed.

[0057] The main contents of the superstructure inspection include:

[0058] (1) Whether there are network cracks, transverse cracks, vertical cracks, longitudinal cracks, diagonal cracks, and horizontal cracks on the concrete surface, and record the key characteristics such as crack width and distribution. Whether there is water accumulation inside the box girder and whether the ventilation is good.

[0059] (2) Whether there are cracks and fissures in the prestressed anchor head and toothed plate, whether the crack width exceeds the limit, whether there are broken wires or failures in the exposed steel strands, and whether there is serious deformation of the beam and plate due to prestress loss.

[0060] The main contents of the substructure inspection include:

[0061] (1) Whether there are structural cracks in the cap beam, whether the concrete of the cap beam has spalling, exposed reinforcement, honeycomb, pitting, voids, or holes, and whether there is water seepage or salt precipitation at the cracks.

[0062] (2) Whether there are structural cracks, deformation, concrete spalling, exposed reinforcement, honeycomb, pitting, voids, holes, weathering, water seepage, corrosion, durability defects, etc. in the pier body.

[0063] (3) Whether there is erosion or hollowing of the base, whether there is deformation or cracking.

[0064] (4) Whether there are cracks, deformation, bulging, or loose masonry in the wing (ear) wall.

[0065] The main inspection contents of the bridge deck system include:

[0066] (1) Visual inspection of the cement concrete bridge deck pavement layer revealed polishing, peeling, exposed aggregate, misalignment, potholes, spalling, arching, damaged joint material, cracks (broken corner slabs, broken slabs), etc.

[0067] (2) Visually inspect the asphalt concrete bridge deck pavement for deformation (ruts, bumps, unevenness), bleeding, damage, and cracks (crazing, block cracks, longitudinal cracks, transverse cracks).

[0068] The identification process is based on manual visual inspection, supplemented by professional tools to improve accuracy (such as crack observation instruments, steel rulers, steel tape measures, telescopes, cameras, calipers, magnifying glasses, and depth detection software): For visible cracks, the direction (horizontal, vertical, longitudinal, diagonal, network, or L-shaped) and distribution area (such as the bottom of the slab, web, or side of the abutment) are initially determined by visual observation. Then, the length of the crack is measured with a steel tape measure, and its start and end positions are marked. Crack width is a core identification indicator and requires precise measurement using an intelligent crack observation instrument or reading microscope. For network cracks in large areas such as bridge deck pavement, a steel ruler is also needed to assist in measuring the crack coverage area, while recording whether the crack is accompanied by related defects such as water seepage, salt precipitation, concrete spalling, or exposed rebar. For hidden parts (such as the inside of box girders and the sides of pier foundations), bridge inspection vehicles and temporary supports are used to approach the components, or telescopes and cameras are used to assist in observation to ensure complete collection of crack information. All identification results must be recorded in detail, including the location, shape, size, and related characteristics of the defects, to provide complete data support for subsequent classification.

[0069] Cracks are then classified based on the recorded data. Crack classification should be combined with the requirements of the specifications and the actual impact of the defects. The severity of the defects should be defined in accordance with the "Technical Condition Assessment Standard for Highway Bridges" (JTG / T H21-2011) and the research report. The classification should be based on the width, length, distribution range and the degree of impact on structural safety.

[0070] Specifically, the cracks are classified as follows: Level 1 cracks are minor cracks with a width of less than 0.15 mm and a short length (generally not exceeding 2 m). They are mostly surface shrinkage cracks or temperature cracks, with no obvious expansion trend, and do not affect the structural bearing capacity. Only surface sealing treatment is required, such as the fine mesh cracks in the bridge deck pavement layer and the short transverse cracks on the pier surface.

[0071] Secondary cracks are medium-sized cracks, with a width between 0.15mm and 0.3mm and a length of 2m to 5m. They may be distributed in the web of the main beam, the side walls of the abutment, etc. Some are accompanied by slight water seepage. Although they do not directly threaten the structural safety, there is a risk of expansion. They need to be sealed by pressure grouting to prevent water intrusion and steel corrosion. Examples include the transverse cracks in the hollow slab of Xiangshuitan Bridge and the medium-length vertical cracks in the abutment of Jiaoxi Bridge.

[0072] Level 3 cracks are severe cracks, with a width > 0.3 mm and a length exceeding 5 m, or are continuous and densely distributed. They may lead to concrete spalling, exposed rebar, and even affect the structural stability of the component. They are considered excessive cracks and require reinforcement treatment after sealing the cracks. Examples include the vertical cracks (maximum crack width 3.0 mm) and circumferential cracks (maximum crack width 0.80 mm) in the main arch of the Kaixia River Bridge, which will be explained later. These types of cracks require reinforcement measures such as bonding steel plates and anchoring rebar, based on the structural bearing capacity test results.

[0073] Furthermore, the crack development trend must be considered during the grading process. Changes in crack width and length are recorded regularly. If a crack expands rapidly in a short period (e.g., its width increases by more than 0.05 mm per month), the treatment level needs to be upgraded, and emergency treatment measures should be prioritized. Simultaneously, a comprehensive assessment is made based on the importance of the component where the crack is located. For example, cracks in core load-bearing components such as the main arch ring and main beam, even if their size does not reach the severe level, require increased attention to prevent structural safety hazards caused by crack expansion. This grading method not only meets the targeted requirements for treating different types of defects but also matches economical and efficient treatment solutions for cracks of different grades, ensuring the scientific and rational nature of bridge maintenance.

[0074] In this embodiment, a survey was conducted on 80 bridges (counted by name) located on main roads and in urban areas of various counties in Tongren Prefecture, Guizhou Province. These included 1 extra-large bridge, 46 medium-sized bridges, and 33 small bridges. The superstructure types included truss composite arch bridges, solid-web masonry arch bridges, hollow-web masonry arch bridges, T-beams, hollow slabs, box girders, and cast-in-place slabs, etc., for reference. Figure 1 Statistical results.

[0075] Based on the statistical results, three representative bridges were selected for illustration: Kaixia River Bridge on G354, Xiangshuitan Bridge on S304, and Jiaoxi Bridge on G326.

[0076] (1) Kaixia River Bridge on G354 Figure 2 ): 2×6.5m reinforced concrete monolithic cast-in-place slab + 1×20m solid web masonry arch + 1×6.5m reinforced concrete monolithic cast-in-place slab; Pier No. 1 adopts a double column pier, the remaining piers adopt gravity piers, and the abutments adopt gravity abutments.

[0077] Key diseases:

[0078] Approach Bridge: One network crack in the cast-in-place slab, totaling 2.0 m²; five spalling cracks, totaling 1.03 m². Pier: One circumferential crack, 0.7 m long, with a maximum width of 0.80 mm (exceeding the width limit); four spalling cracks, totaling 0.68 m². Abutment: Two instances of loose mortar joints. Bridge Deck: Two network cracks, totaling 5.25 m². Guardrail: Five damaged sections, totaling 6.5 m².

[0079] Main Bridge: The mortar joints in the main arch ring are not tight and are whitish. There are two vertical cracks on the upper sidewall of the arch, with a total length of 4.4m and a maximum width of 3.0mm, exceeding the width limit; one mortar joint is not tight. The pier has one diagonal crack with a total length of 4.0m; two vertical cracks with a total length of 2.8m and a maximum width of 1.10mm, exceeding the width limit; the pier stone is weathered and cracked, and one mortar joint is not tight. The foundation has one area of ​​erosion and hollowing. The guardrail has one damaged section with a total area of ​​0.90 square meters. All seven drainage holes are not functioning properly.

[0080] (2) Xiangshuitan Bridge on S304 ( Figure 3 The bridge consists of 2×16m reinforced concrete hollow slabs, simply supported structure, with 6 slabs arranged laterally; the piers are double-column piers, and the abutments are U-shaped abutments.

[0081] Key diseases:

[0082] Defects in the superstructure: 420 transverse cracks on the bottom of the hollow core slab, totaling 458.0m in length, with a maximum crack width of 0.16mm (width within limits); 4 longitudinal cracks, totaling 6.1m in length, with a maximum crack width of 0.20mm (width within limits); 2 areas of peeling and chipping, totaling 0.23㎡; 1 cavity / hole, totaling 0.12㎡; 51 L-shaped cracks in the web, totaling 28.6m in length, with a maximum crack width of 0.14mm (width within limits); 1 area of ​​expansion cracking and peeling, totaling 0.02㎡. Supports exhibit 1 misalignment, 22 voids, and 1 aging crack.

[0083] Substructure defects: One network crack in the pier body, covering an area of ​​0.2 square meters; one instance of concrete corrosion in the cap beam, covering a total area of ​​2.4 square meters. One horizontal crack in the abutment cap, with a total length of 1.0 m and a maximum width of 0.30 mm (width exceeds the limit); one vertical crack, with a total length of 0.40 m and a maximum width of 0.10 mm (width does not exceed the limit); two vertical cracks in the abutment sidewalls, with a total length of 4.0 m and a maximum width of 0.20 mm (width does not exceed the limit). One instance of scour and hollowing in the pier foundation.

[0084] Bridge deck defects: There is one rut in the bridge deck pavement, with a total area of ​​2.0 square meters. Two drainage holes are blocked, and one is not draining properly.

[0085] (3) Jiaoxi Bridge on G326 ( Figure 4 ), 1×15.4m solid reinforced concrete slab arch; gravity abutment.

[0086] Key diseases:

[0087] Superstructure defects: There are 8 cracks in the main arch ring, with a total length of 43.2m and a maximum width of 0.3mm, which is within the width limit; 2 network cracks with a total area of ​​63.0㎡; and 1 area of ​​whitening.

[0088] Substructure defects: There are 2 white spots on the platform; 1 spot is eroded by water; 1 crack with an area of ​​2.296 ㎡, 10 cracks with a total length of 39.9m and a maximum width of 0.28mm, which does not exceed the width limit.

[0089] Bridge deck defects: There is one crack in the bridge deck pavement, covering an area of ​​3.75 square meters; there are a total of 27 vertical cracks in the guardrail, with a total length of 28.3 meters and a maximum width of 0.18 meters.

[0090] Based on the bridge's health record data, a comprehensive analysis of the causes of bridge cracks is conducted as follows:

[0091] 1. Analysis of the causes of defects in the superstructure

[0092] (1) Longitudinal cracks in the main beam: Longitudinal cracks are generated under the influence of factors such as longitudinal prestressing and deviation of pipe position. Surface cracks are caused by concrete drying shrinkage or temperature changes.

[0093] (2) Diagonal cracks in the web of T beam: mainly caused by the large temperature difference between the inside and outside of the concrete or the large temperature difference between the surface of the T beam and the air, resulting in temperature stress greater than the actual tensile strength of the concrete, and cracks on the surface of the approach bridge T beam. The secondary causes are excessive concrete slump, over-vibration, and poor curing.

[0094] (3) Longitudinal cracks in hollow slabs: shrinkage cracks caused by temperature difference between the inside and outside of the hollow slab; possibly due to the difficulty in vibrating the bottom slab concrete, with most of the fine aggregate flowing into the outlet, forming longitudinal cracks under vehicle load.

[0095] (4) Transverse cracks in hollow slabs: shrinkage cracks caused by temperature difference between the inside and outside of the hollow slab; under the action of dead load and vehicle load, the mid-span section of the slab beam is mainly subjected to bending, and the bottom plate is also prone to tensile stress, which generates transverse cracks under the coupling effect with the defects of the main beam itself.

[0096] (5) L-shaped cracks in hollow slabs: transverse shrinkage cracks caused by improper maintenance during construction gradually develop into L-shaped cracks under vehicle load.

[0097] (6) Main beam mesh cracks: surface cracks caused by concrete drying shrinkage or temperature changes.

[0098] (7) Diagonal cracks in the diaphragm: The connection parts of the components assembled later are damaged due to repeated vehicle loads.

[0099] 2. Analysis of the causes of substructure defects

[0100] (1) Vertical cracks in caps and beams: ① Surface cracks caused by concrete shrinkage or temperature changes; ② Cracking of surface concrete caused by the expansion of the volume of the steel reinforcement inside the concrete after oxidation and corrosion.

[0101] (2) Vertical cracks in the front wall of the U-shaped bridge abutment: due to the high backfill behind the abutment, the soil pressure is large; the additional pressure caused by the expansion of the backfill behind the abutment when it encounters water, and other factors, vertical cracks are caused.

[0102] (3) Vertical cracks in the side wall of U-shaped bridge abutment: Due to the closed structure of U-shaped bridge abutment, water is easy to accumulate inside the abutment, which increases the pressure of the backfill soil behind the abutment and generates additional pressure that squeezes the abutment body; uneven settlement of the abutment foundation; impact of overloaded vehicles on the spacing of the abutment.

[0103] (4) Horizontal cracks in bridge abutments: The abutment is cracked due to layered pouring or horizontal loads such as soil pressure and water pressure.

[0104] (5) Cracking of masonry: Masonry arch bridges have a long service life, and long-term environmental effects have led to natural weathering and cracking of the masonry blocks.

[0105] 3. Analysis of the causes of bridge deck system defects

[0106] (1) Potholes in bridge deck pavement: During the operation of the bridge, the bridge deck pavement is cracked due to the rolling and impact of wheel loads, and gradually develops into potholes.

[0107] (2) Bridge deck pavement cracks: During operation, the bridge deck pavement is cracked due to the rolling and impact of wheel loads; the shrinkage of asphalt concrete due to winter cooling; and the loosening and damage at the joints between beams, which lead to reflective cracks in the pavement layer.

[0108] (3) Cracks in the bridge deck pavement at the pier top: Because the bridge deck is located at the part of the main beam with the greatest deformation, it has to bear the deformation caused by the rotation and expansion of the beam. This makes the stress at the bridge deck continuous part complex and prone to cracks, damage and other defects, which are reflected to the pavement layer.

[0109] Based on the analysis of the causes of bridge defects, the Xiangshuitan Bridge on S304 was selected as the target for treatment, and the following maintenance and reinforcement plan was formulated:

[0110] 1. Superstructure

[0111] Epoxy resin mortar is used to repair surface defects in the bridge structure, such as concrete spalling, corrosion, exposed rebar rust, voids, and honeycomb pitting. Cracks less than 0.15mm wide are treated with surface sealing; cracks ≥ 0.15mm wide are sealed with pressure grouting. Hollow core slabs are reinforced with 6mm thick steel plates to improve their bending capacity. See details for further information. Figure 5 and Figure 6 As shown.

[0112] 2. Substructure

[0113] To reduce the scouring of the piers by the water flow, C25 rubble concrete was used for protection at the foot of the retaining wall of pier No. 0 and the hollowed-out area of ​​the pile foundation of pier No. 1; vegetation attached to the piers and other structures was removed and washed clean with water.

[0114] 3. Support system

[0115] Because some bearings have developed defects such as voids, aging and cracking, and misalignment, according to the relevant provisions of Table 1.0.4 in the "General Specifications for Design of Highway Bridges and Culverts" (JTG D60-2015), bearings are replaceable components with a design service life of 15 years. The bearings of this bridge have been in service for nearly 20 years, so all the bearings of the bridge will be replaced.

[0116] 4. Bridge deck system and its ancillary facilities

[0117] Because the original asphalt pavement thickness was 23cm, the guardrail height was reduced, and the asphalt concrete surface layer was partially damaged. Therefore, after completely removing the asphalt pavement and laying a 5cm asphalt concrete surface layer, the guardrail height will meet the specifications. The original guardrail demolition and reconstruction has been cancelled. Instead, the guardrails will be ground and then finished with epoxy resin mortar. The original metal guardrails will be fixed to the concrete guardrails using rebar anchoring. To enhance the bridge's drainage function, the transverse drainage pipes will be reinstalled using 110 PVC pipes, spaced 4m apart longitudinally. The bridge expansion joints will be replaced.

[0118] Example 2:

[0119] The difference from Example 1 is that, in step four, the health record data is also used to record the crack distribution model drawings of each surface of the bridge, and crack markers of different colors are drawn on the corresponding crack distribution model drawings according to the associated cracks and newly added cracks.

[0120] For example, different colored crack markers are used on the corresponding crack distribution model drawings to help construction workers determine the location of cracks on the bridge, clearly identify the impact of subsequent reinforcement methods on the original bridge structure, and adjust the reinforcement direction on-site based on the displayed information.

[0121] In the crack distribution model drawings, loose areas are also marked proportionally based on crack markers, and additional reinforcement is applied to the interaction areas between different loose areas. When loose areas interact with each other in different bridge cracks, it indicates that the cracks are interfering with each other, increasing the subsequent impact on the bridge. Therefore, by marking loose areas, additional reinforcement is applied to the interaction areas during subsequent crack reinforcement, thereby ensuring the stability of the bond between the interface and the bridge.

[0122] It is also used to create digital models for crack distribution drawings. Crack markers and loose areas are recorded in the digital model, and reinforcement methods are recorded in the digital model with different markers. By creating digital models, cracks, loose areas, and reinforcement methods can be accurately represented, allowing construction personnel to confirm in detail the distribution and impact on the bridge, thereby improving the accuracy of subsequent adjustments to reinforcement methods during construction.

[0123] Example 3

[0124] The difference from Example 2 is that in step 3, the different grades of cracks are further classified based on the original width and length indicators, and five key indicators are added: crack morphology, penetration status, importance of the component where it is located, degree of environmental erosion and expansion rate, forming a comprehensive classification system of basic indicators and auxiliary indicators.

[0125] In terms of morphology, cracks are classified into linear cracks (transverse, longitudinal, and oblique), network cracks, and L-shaped / U-shaped composite cracks. Among them, network cracks and composite cracks cause stronger damage to the overall structure, and even if the basic indicators are at a medium level, they need to be upgraded one level. In terms of penetration status, non-penetrating cracks (only surface cracks), semi-penetrating cracks (not penetrating the cross section of the component), and fully penetrating cracks (penetrating the thickness or cross section of the component) are clearly defined. Fully penetrating cracks are directly classified into the category of severe cracks, while semi-penetrating cracks are upgraded by half a level from the original level.

[0126] Based on the importance of the components, bridge components are divided into core load-bearing components (main beams, main arch rings, piers, foundations), secondary load-bearing components (cap beams, diaphragms, upper side walls of the arches), and non-load-bearing components (guardrails, bridge deck pavement). Cracks on core load-bearing components need to be upgraded one level from the original classification, while minor cracks on non-load-bearing components can maintain the original classification but the treatment process is simplified.

[0127] The degree of environmental erosion is classified according to the environment in which the bridge is located: ordinary atmospheric environment, coastal salt spray environment, industrial corrosive environment, and high-altitude freeze-thaw environment. Cracks in corrosive or freeze-thaw environments are more susceptible to accelerated expansion due to environmental factors, so the original level needs to be upgraded by one level, and the reinforcement materials must be selected to be corrosion-resistant.

[0128] The rate of expansion index is determined through regular monitoring (once a month for three consecutive months). If the monthly increase in crack width exceeds 0.05 mm or the monthly increase in length exceeds 0.5 m, it is judged as a rapidly expanding crack and is treated directly as a severe crack. If the monthly increase is between 0.01 mm and 0.05 mm, the original level is upgraded by half a level. If the monthly increase is less than 0.01 mm, the original level is maintained.

[0129] The refined grading standards are more aligned with actual engineering scenarios. For example, a transverse semi-through crack measuring 0.2mm in width and 3m in length appeared on a core load-bearing component (main beam). Located in a coastal salt spray environment, its monthly expansion rate was 0.03mm. According to the original standard, it was classified as a medium crack. After further grading, due to the core component, semi-through state, corrosive environment, and slow expansion characteristics, it was upgraded to a moderately severe crack. The reinforcement method was changed from simple pressure grouting to a combination of pressure grouting and partial steel plate bonding. On the other hand, a network crack measuring 0.2mm in width and 4m in length appeared on a bridge deck pavement (non-load-bearing component). Located in a normal environment and showing no expansion trend, although it was originally classified as a medium crack, after refined grading, it remained at the medium crack level, and the treatment method was simplified to surface sealing. This further grading method, through comprehensive judgment using multiple indicators, makes the grading results more scientific and the reinforcement plan more targeted, further improving the technical reliability of bridge reinforcement while avoiding over-reinforcement or under-treatment, thus balancing technical rationality and economic practicality.

[0130] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for graded treatment and reinforcement of cracks in concrete bridges, characterized in that, Includes the following steps: Step 1: Establish and acquire health records for the bridge. Health records include the bridge's geometric parameters, material parameters, environmental parameters, maintenance records, historical bridge quality inspection reports, and existing defects in historical bridges. Based on the health records, assess potential hazard areas and determine re-inspection areas based on existing defects in historical bridges. Step 2: Conduct a visual inspection of the bridge using manual inspection and common measurement tools. Focus on inspecting the superstructure, substructure, and deck system of the bridge according to the areas of potential hazards and areas requiring re-inspection to determine whether any new related cracks have been added to the areas of potential hazards and areas requiring re-inspection. At the same time, obtain information on any new cracks in other locations of the bridge using manual inspection and common measurement tools and record them in the health record data. Step 3: Based on the associated cracks, retrieve the maintenance records from the health records, analyze the impact of the disaster cause on the historical reinforcement in the maintenance records, and adjust the reinforcement method; then, based on the width of the newly added cracks, classify them into minor cracks, medium cracks, and severe cracks, and obtain the corresponding reinforcement methods based on minor cracks, medium cracks, and severe cracks. Step 4: When reinforcing bridge cracks based on reinforcement methods, the loose areas in the crack area are determined by ultrasonic measurement and cleaned.

2. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 1, characterized in that, In steps two through four, the method for manually recording associated cracks and newly added cracks is as follows: for areas with potential hazards, they are recorded as naturally growing cracks; for newly added associated cracks in re-inspection areas, they are recorded as incompletely reinforced cracks. Based on the natural growth cracks, retrieve the corresponding influencing conditions; based on the influencing conditions, retrieve the health records to see if there are maintenance records with similar influencing conditions; based on the maintenance records, check the reinforcement status of the corresponding re-inspection areas; if new cracks are found in the reinforcement status, analyze the causes of the disaster based on the new cracks, and adjust the reinforcement method based on the causes of the disaster; if no new cracks are found in the reinforcement status, perform crack reinforcement based on the reinforcement method corresponding to the maintenance records. Based on the incomplete reinforcement of cracks, an ultrasonic measurement device is used to determine whether the loose area in the re-inspection area is consistent with the historical cracks in the historical bridge. If they are consistent, the impact of construction factors is recorded in the health record data; if they are inconsistent, the cause of the disaster is analyzed, and the reinforcement method is adjusted based on the cause of the disaster.

3. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 2, characterized in that, In steps two through four, the method for obtaining historical cracks in the defects of historical bridges includes not only the bridge's own health record data, but also health record data with consistent geometric and material parameters as a reference.

4. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 3, characterized in that, In step three, minor cracks are defined as having a width of <0.15mm and a length of <2m; moderate cracks are defined as having a width of 0.15mm-0.3mm and a length of 2m-5m; and severe cracks are defined as having a width of >0.3mm and a length of >5m.

5. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 4, characterized in that, In step four, an ultrasonic measuring device is used to determine the loose area in the crack area, and the consistency of sound between the surrounding bridge concrete layer and the loose area is used to confirm the completion of the cleaning of the interface around the crack.

6. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 5, characterized in that, In step one, the potential hazard area is determined based on the structural weaknesses of the bridge, the causes of environmental disasters, and the rate of expansion of existing defects in the bridge.

7. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 6, characterized in that, In step three, the reinforcement methods include surface sealing, pressure grouting, and structural anchoring.

8. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 7, characterized in that, In step four, the health record data also includes a crack distribution model drawing of each surface of the bridge, and crack markers of different colors are drawn on the corresponding crack distribution model drawing according to associated cracks and newly added cracks.

9. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 8, characterized in that, In step four, the crack distribution model drawing will also mark the loose areas proportionally based on the crack markers, and additional reinforcement treatment will be carried out based on the interaction area of ​​different loose areas.

10. The method for graded treatment and reinforcement of cracks in concrete bridges according to claim 9, characterized in that, In step four, a digital model is also used to create a crack distribution model drawing. Crack markers and loose areas are recorded in the digital model using digital representation. The reinforcement methods are then recorded in the digital model using different markers.

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